TY - CONF A1 - Krankenhagen, Rainer A1 - Chaudhuri, Somsubhro A1 - Pittner, Andreas A1 - Winterkorn, Rene A1 - de Finis, Rosa A1 - Palumbo, Davide A1 - Galietti, Umberto T1 - Thermographic investigation of the anisotropic behaviour of additively manufactured AISI316 steel using DED-Arc N2 - Additive manufacturing is one of the most promising techniques for industrial production and maintenance, but the specifics of the layered structure must be considered. The Direct Energy Deposition-Arc process enables relatively high deposition rates, which is favourable for larger components. For this study, specimens with different orientations were prepared from one AISI316 steel block – parallel and orthogonal to the deposition plane. Quasistatic tensile loading tests were carried out, monitored by an infrared camera. The obtained surface temperature maps revealed structural differences between both orientations. The consideration of surface temperature transients yields more details about the behaviour of the material under tensile loading than the conventional stress-strain-curve. These preliminary investigations were supplemented by thermographic fatigue trials. Although the anisotropy was also observed during fatigue loading the fatigue behaviour in general was the same, at least for both inspected specimens. The presented results demonstrate the abilities and the potential of thermographic techniques for tensile tests. T2 - 17th Quantitative Infrared Thermography Conference CY - Bologna, Italy DA - 07.07.2025 KW - Thermoelastic effect KW - Wire-arc-additive manufacturing KW - thermal stress analysis KW - fatigue testing PY - 2026 DO - https://doi.org/10.21611/qirt-2024-029 SP - 1 EP - 8 AN - OPUS4-65372 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Campari, Alessandro A1 - Konert, Florian A1 - Razavi, Nima A1 - Sobol, Oded A1 - Alvaro, Antonio T1 - Hydrogen-assisted cracking: A deep learning approach for fractographic analysis N2 - Hydrogen handling equipment suffers from interaction with their operating environment, which degrades the mechanical properties and compromises component integrity. Hydrogen-assisted cracking is responsible for several industrial failures with potentially severe consequences. A thorough failure analysis can determine the failure mechanism, locate its origin, and identify possible root causes to avoid similar events in the future. Postmortem fractographic analysis can classify the fracture mode and determine whether the hydrogen-metal interaction contributed to the component’s breakdown. Experts in fracture classification identify characteristic marks and textural features by visual inspection to determine the failure mechanism. Although widely adopted, this process is time-consuming and influenced by subjective judgment and individual expertise. This study aims to automate fractographic analysis through advanced computer vision techniques. Different materials were tested in hydrogen atmospheres and inert environments, and their fracture surfaces were analyzed by scanning electron microscopy to create an extensive image dataset. A pre-trained Convolutional Neural Network was finetuned to accurately classify brittle and ductile fractures. In addition, Grad-CAM interpretability method was adopted to identify the image regions most influential in the model’s prediction and compare the saliency maps with expert annotations. This approach offered a reliable data-driven alternative to conventional fractographic analysis. KW - Failure analysis KW - Fractographic analysis KW - Hydrogen embrittlement KW - Material compatibility PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-646610 DO - https://doi.org/10.1016/j.commatsci.2025.114366 SN - 0927-0256 VL - 262 SP - 1 EP - 16 PB - Elsevier Science CY - Amsterdam [u.a.] AN - OPUS4-64661 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröder, Nina A1 - Uhlig, Marvin A1 - Kromm, Arne A1 - Schröpfer, Dirk A1 - Höfer, Kevin A1 - Hensel, Jonas A1 - Kannengießer, Thomas T1 - Challenges in the evaluation of the weldability of old mild steels for future use N2 - For reasons of sustainability and cost efficiency, there is an increasing trend in the steel-processing industry to retrofit existing structures, avoiding costly shutdowns or dismantling. Although welding is a cost-effective joining method, it is rarely applied to old steels, whereas riveted or bolted connections are often uneconomical. Repair and refurbishment frequently require the replacement of damaged material or the creation of dissimilar old–new steel joints. Due to the varied manufacturing processes of historical steels, not all twentieth-century steels are inherently weldable, making an initial assessment of weldability essential. In this study, a historical non-deoxidized mild steel (produced by Siemens–Martin processing) originating from the construction of the Berlin Radio Tower (erected in 1926) was investigated using dilatometry to analyze its welding behavior. A database of welding CCT diagrams and HAZ simulations was established to support practice-oriented welding experiments, providing key insights into their weld-metallurgical behavior and weldability. Furthermore, initial welding trials were conducted, and the local residual stress states in dissimilar old–new steel joints were determined. These foundational investigations are critical for the development of innovative, load-adapted welding concepts for the repair and refurbishment of existing old-steel infrastructure in Germany. KW - Old mild steels KW - Repair welding KW - Weldability KW - Thermo-physical simulation KW - CCT diagrams PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-654784 DO - https://doi.org/10.1007/s40194-026-02366-6 SN - 1878-6669 SP - 1 EP - 14 PB - Springer nature AN - OPUS4-65478 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hübner, Martin A1 - Dittmann, Florian A1 - Kromm, Arne A1 - Varfolomeev, Igor A1 - Kannengiesser, Thomas T1 - Enhancement of the fatigue strength by application of a low transformation temperature (LTT) welding consumable N2 - Low transformation temperature (LTT) welding consumables offer a possibility to enhance fatigue strength in welded components without post-treatment. By lowering the martensite start temperature (MS), the volume expansion during transformation near ambient temperature reduces welding related tensile residual stresses in fatigue-critical areas. To evaluate this effect, longitudinal stiffeners were used, a LTT and conventional filler serve as welding consumable, also high frequency mechanical impact (HFMI) treatment was carried out. Three single-pass and six additional-pass sample series were investigated on residual stress and fatigue strength. The additional welds were applied in fatigue crack critical areas with different weld shapes, achieved by varying welding parameters. Mechanical tests on reference samples evaluated the properties of the diluted LTT welds. Although reduced toughness was observed, no fatigue cracks occurred in LTT single-pass weld roots. The fatigue strength at two million cycles increased from 81 MPa to 121 MPa compared to conventional welds, while HFMI reached 146 MPa. With an additional LTT weld pass the results varied from 138 MPa to 196 MPa, depending to the shape and residual stress state. The results show that LTT fillers effectively enhance fatigue performance, and that weld geometry and parameter selection are as critical as the chemical composition for maximizing the LTT effect. CY - Genua, Italy DA - 22.06.2025 KW - Low transformation temperature (LTT) KW - Martensite start temperature KW - Residual stress KW - Longitudenal stiffener KW - Fatigue strength PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-654520 DO - https://doi.org/10.1007/s40194-026-02356-8 SP - 1 EP - 14 PB - Springer Nature AN - OPUS4-65452 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kleba-Ehrhardt, Rafael A1 - Dávila, Josué A1 - Geissler, Johann A1 - Mohr, Gunther A1 - Schmidt, Johannes A1 - Heinze, Christoph A1 - Hilgenberg, Kai A1 - Gurlo, Aleksander A1 - Karl, David T1 - Influence of Haynes 282 powder oxidation on powder properties and component quality in laser powder bed fusion N2 - Reuse of powder in powder bed additive manufacturing is a common practice to enhance sustainability and reduce costs. However, the reusability of metal powder is limited by the oxidation of the powders. Even in a protective atmosphere, each build job leads to gradual oxidation of the powder, which has led to concerns about its impact on powder and part properties. Consequently, strict confidence intervals for oxygen content in nickel-based alloy feedstocks are enforced in the industry. Despite this, there is currently a lack of in-depth studies investigating the specific influence of oxygen on Haynes 282, a widely used nickel-based alloy. This study examines artificially aged Haynes 282 powder batches with oxygen content of 160 ppm, 330 ppm, 1050 ppm, and 1420 ppm. Detailed powder characterization was performed, including morphology, chemical composition, particle size, flowability, and packing behavior. Components were fabricated via PBF-LB/M to evaluate density and mechanical properties. The results showed that higher oxidation levels improved powder flowability and packing density. However, in manufactured parts, irregular melt tracks and increased surface roughness were observed, which could easily be removed by post-processing. No significant differences in density or mechanical properties at room temperature, such as tensile strength and elongation, were found. These findings indicate that H282 powder potentially remains suitable for reuse, even when the batches exhibit increased oxygen content, supporting discussions on revising the existing oxygen content confidence intervals for nickel-based alloys. The results highlight the potential for optimizing recycling strategies and reducing material waste in additive manufacturing processes. KW - Additive manufacturing KW - Powder bed fusion KW - Powder characterization KW - Powder oxidation KW - Powder recycling PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-654545 DO - https://doi.org/10.1016/j.addma.2025.105050 SN - 2214-8604 VL - 116 SP - 1 EP - 16 PB - Elsevier B.V. AN - OPUS4-65454 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pittner, Andreas T1 - Adaptive manufacturing strategies for DED-Arc: Case studies on high-strength aluminium alloys and gas-turbine blade repair N2 - In this presentation, we showcase BAM’s current research activities on DED-Arc/M processes, covering both the manufacture of novel high-strength aluminium alloys and the development of automated repair strategies for gas turbine blades, with a focus on robust process control and repeatable component quality. T2 - 12. Wissenschaftliches Kolloquium im Rahmen des SFB/TRR 375 "Multifunktionale Hochleistungskomponenten aus hybriden porösen Materialien" CY - Online meeting DA - 05.02.2026 KW - DED-Arc KW - Automation KW - Quality assessment PY - 2026 AN - OPUS4-65472 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bär, J. A1 - Kanna, N.K. A1 - Duarte, Larissa A1 - Madia, Mauro T1 - Determination of the Kitagawa-Takahashi Diagram using DC Potential Drop Measurements N2 - The Kitagawa-Takahashi Diagram is an important tool for describing the fatigue limit of components containing defects. The models used for its description differ, particularly in the transition region corresponding to the short crack regime. Therefore, for a reliable statement about the fatigue limit in this area, an experimental validation of the models is necessary. However, the standardized staircase method requires a large number of samples and has a long test duration. In this work, a method is presented that allows a simpler and faster validation of the Kitagawa-Takahashi Diagram in the region of short cracks. Rectangular notches with a defined width and depth were manufactured in flat samples of a low-alloyed steel with two different heat treatments using an engraving laser. This method allows a rapid production of very sharp notches without plastic deformation and with only a slight thermal influence on the surrounding material. The samples prepared in this way were fatigued with block wise increasing loads until failure. Cracks are detected by means of a Direct Current Potential Drop method. The length of the loading block (number of cycles) is determined by the measured potential drop. This procedure enables a reliable and precise determination of the limit stress for the respective notch size with low experimental effort and time consumption. The tests have shown that in case of the normalized steel none of the models describes the determined values for the fatigue limit. For the hardened steel, the plot of the fatigue limit as a function of the Murakami parameter √area in combination with the El Haddad model allows a satisfactory description of the measured values. T2 - 5th International Symposium on Fatigue Design and Material Defects CY - Trento, Italy DA - 14.05.2025 KW - Kitagawa-Takahashi diagram KW - Damage tolerance KW - Fatigue KW - Potential drop KW - Fracture mechanics PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-655519 DO - https://doi.org/10.1016/j.prostr.2025.12.283 VL - 76 SP - 27 EP - 34 PB - Elsevier B.V. AN - OPUS4-65551 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Witte, Julien A1 - Treutler, Kai A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas T1 - Influence of Microstructure on the Machinability and Surface Integrity of Additively Manufactured Iron Aluminides N2 - The increasing global focus on energy and resource efficiency has stimulated a growing interest in additive manufacturing. AM offers economic advantages and enables an efficient use of materials. However, AM components often require subsequent mechanical post-processing, such as machining (e.g. milling), to achieve the final contours or surfaces. This is a particular challenge due to the heterogeneous and anisotropic nature of AM structures, which affect machining and the resulting component properties. High-performance materials such as iron aluminide represent a promising alternative to conventional high-temperature materials with a significant economic advantage. However, the strength and hardness properties, which are advantageous for applications in highly stressed lightweight components, pose a challenge for economical machining in addition to the AM microstructure properties. The difficult-to-cut material causes accelerated tool wear and insufficient surface quality. This study shows that crack-free additive manufacturing of the three-component system of iron-nickel-aluminum is possible, and advantages in terms of machinability compared to FeAl-AM components are achieved. The more homogeneous microstructure leads to a reduction in cutting forces, with positive effects on the machinability and optimized surface integrity. Ultrasonic assisted milling (USAM) offers great potential to address the major challenges posed by difficult-to-cut materials and additively manufactured weld structures. Therefore, this study focuses on assessing the transferability of previous positive results by USAM to the selected iron aluminide alloys. The machinability of the aluminides is analyzed by varying significant influencing variables in finish milling experiments and evaluated in terms of the loads on the tool and the resulting surface integrity. T2 - AA Meeting of Commission IX ‘Behavior of Metals subject to Welding’ CY - Rhodes, Greece DA - 08.07.2024 KW - Iron aluminide KW - Additive manufacturing KW - Machinability KW - Surface integrity KW - Ultrasonic-assisted milling PY - 2026 SP - 1 EP - 16 AN - OPUS4-65530 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dixneit, J. A1 - Gibmeier, J. A1 - Kromm, Arne A1 - Schubnell, J. A1 - Lang, F. A1 - Loebich, F. A1 - Carl, E.-R. A1 - Ya, W. T1 - Residual stress distribution of a large component manufactured by AM-DED-Arc from high-strength weld filler material X90 N2 - Currently, DED-Arc manufactured components are not covered by design guidelines, and design factors such as residual stress factors are not defined for such components. This hinders industrial use, especially for components with a remaining surface waviness required by industry. For the first time the stress state of a high-strength, low-alloy, large-scale DED-Arc component was characterised in the as-built state and after cutting off the component from the substrate plate. Complementary methods of residual stress analyses were applied to gain a holistic insight into the residual stress distributions of a thick-walled part. In the as-built state, direction-dependent and position-dependent tensile residual stresses were found for the component at the level of the yield strength of the part. The additive manufacturing strategy continuous spiral deposition has no significant influence on the residual stresses in bead threshold area compared to the residual stresses of the remaining component. For this case, bead threshold is no structural imperfection. By removing the part from the substrate plate, the residual stresses are significantly redistributed. Tensile residual stresses are then present at a moderate level. Compressive residual stresses were determined in the volume of the deposited material. The general consideration of ‘‘high’’ tensile residual stresses in such thick-walled components is rather conservative. Therefore, design guidelines should take the manufacturing condition into account. KW - AM-DED-Arc KW - Residual stress KW - High strength steel PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-655239 DO - https://doi.org/10.1177/03093247251406876 SN - 2041-3130 SP - 1 EP - 18 PB - SAGE AN - OPUS4-65523 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, Sergej A1 - Biegler, Max A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Integration of hybrid laser-arc and narrow gap submerged arc welding for cost-effective joining of 80 mm thick S355ML steel plates N2 - This paper presents the results of developing a cost-effective, robust process for welding thick steel plates. Welding trials were performed on S355ML structural steel plates with a thickness of 80 mm. A specially designed U-shaped joint preparation with a 45 mm root face was proposed to enable thick welds to be welded using a combined technique. In the developed process, a hybrid laser arc weld (HLAW) is performed as the first pass. Subsequently, narrow-gap submerged arc welding (NG-SAW) is applied to the opposite side using a multi-layer technique. The weld cross-section is completed using a reliable overlap of both the HLAW and NG-SAW welds. This method achieves a 2.9-fold reduction in weld volume and filler material consumption, as well as shorter production times for thick-walled welds. Further advantages of the process combination include eliminating the need to form the root of the HLAW weld and the absence of a backing support. The applied process parameters ensure that the maximum heat input does not exceed 5 kJ/mm, leading to uniform hardness across the weld metal and heat-affected zone (HAZ). Impact toughness testing at −40 °C demonstrated excellent performance, with Charpy V-notch energies of 138 ± 45 J in the arc-dominated region and 65 ± 12 J in the critical laser-dominated zone of the HLAW weld. In addition, the NG-SAW weld exhibited an average Charpy V-notch energy of 274 ± 5 J, confirming excellent low-temperature toughness of the fill passes. Owing to its high process stability and practical applicability, the proposed welding approach shows high potential for integration into the fabrication of thick-walled offshore constructions. KW - Hybrid laser arc welding KW - Narrow gap submerged arc welding KW - Low carbon structural steel KW - Fusion zone size KW - Microstructure KW - Impact absorbed energy KW - Hardness PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-655627 DO - https://doi.org/10.1016/j.optlastec.2026.114796 SN - 0030-3992 VL - 197 SP - 1 EP - 12 PB - Elsevier Ltd. AN - OPUS4-65562 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Czeskleba, Denis A1 - Rhode, Michael A1 - Wandtke, Karsten A1 - Irfan, Muhammad Dary A1 - Kannengiesser, Thomas T1 - Hydrogen diffusion in thick-walled S690 SAW joints: part 2 – predictive modeling of heat input and microstructure influence N2 - High-strength low-alloy (HSLA) steels such as S690 are widely employed in thick-walled welded structures, where hydrogen-assisted cold cracking (HACC) remains a persistent concern. While microstructure-specific hydrogen diffusion coefficients (DH) for weld metal (WM), heat-affected zone (HAZ), and base material (BM) were experimentally established in Part 1 of this study, their quantitative influence on hydrogen accumulation and effusion has not yet been fully clarified. This work presents a transient, spatially resolved numerical model for simulating hydrogen transport in multi-pass submerged arc welds. The model integrates experimentally determined DH values with realistic thermal cycles and temperature-dependent boundary conditions. Developed in Python, the simulation tool is purpose-built for hydrogen diffusion in welded joints. It offers a focused, transparent alternative. It offers a focused, transparent alternative to general-purpose finite element platforms. Parametric analyses demonstrate that, although the diffusion coefficients vary by up to 50%, their impact on overall hydrogen retention is minor. In contrast, plate thickness, bead geometry, cooling time (t₈/₅), and interpass temperature exert a dominant influence on hydrogen distribution. Despite clear microstructural differences between the thermomechanically rolled (S690MC) and quenched and tempered (S690Q) variants, including opposite HAZ hardness responses (softening in S690MC, hardening in S690Q) in the (pen)ultimate weld bead, the simulations confirm that their diffusion behavior and hydrogen solubility are closely aligned. Consequently, differences in DH and solubility exert only a minor influence on hydrogen retention compared to thermal exposure and joint geometry. These findings support the interchangeable use of both steel grades in terms of HACC risk due to hydrogen diffusion kinetics under comparable welding conditions. KW - Hydrogen assisted cracking KW - Numerical simulation KW - Diffusion KW - Submerged arc welding PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-655721 DO - https://doi.org/10.1007/s40194-026-02395-1 SN - 0043-2288 SP - 1 EP - 16 PB - Springer Science and Business Media LLC AN - OPUS4-65572 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Czeskleba, Denis A1 - Rhode, Michael A1 - Wandtke, Karsten A1 - Irfan, Muhammad Dary A1 - Kannengiesser, Thomas T1 - Hydrogen diffusion in thick-walled S690 saw joints: part 1—experimental determination of microstructure-dependent diffusion coefficients N2 - High-strength low-alloyed steel S690 is widely used in heavy-duty applications, such as structural components, mobile cranes, and industrial plant construction, owing to their high strength and weldability. However, thick-plate submerged arc welding (SAW) can introduce elevated hydrogen levels and residual stresses that promote time-delayed hydrogen-assisted cold cracking (HACC). Accurate, microstructure-specific diffusion data are scarce, limiting predictive HACC assessments. This study presents an experimental determination of hydrogen diffusion coefficients (DH) in two S690 variants: thermomechanically rolled (S690MC) and quenched and tempered (S690Q). Multi-layer SAW welds were produced from 30 mm thick plate material at three heat input levels, and diffusion membranes were extracted from weld metal (WM), heat-affected zone (HAZ), and base material (BM). Hydrogen permeation tests, conducted in accordance with DIN En ISO 17081, yielded flux curves normalized in time from which DH was derived using the inflection-point method. At room temperature, DH values ranged from 6 × 10−5 mm2/s to 9 × 10−5 mm2/s across all regions and heat inputs, with no significant difference between S690MC and S690Q. Weld metal exhibited marginally lower DH, attributed to enhanced hydrogen trapping, while base material measurements showed greater variability. These microstructure-resolved diffusion coefficients add quantitative data for modern S690 SAW welds and provide internally consistent input parameters for the numerical simulations presented in part 2. The results support improved parameterization for subsequent assessments of HACC risk through the optimization of welding parameters. KW - Hydrogen assisted cracking KW - Submerged arc welding KW - Diffusion KW - Electrochemical permeation KW - Microstructure PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-655711 DO - https://doi.org/10.1007/s40194-026-02400-7 SN - 0043-2288 SP - 1 EP - 15 PB - Springer Science and Business Media LLC AN - OPUS4-65571 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ulbricht, Alexander T1 - Do Microbes like Additively Manufactured Aluminium? N2 - The use of laser-additively manufactured metallic components in the industrial sector is gaining traction, with the process now entering its application phase. Consequently, the materials are exposed to corrosive microbes, which this study examines in order to determine the implications of this exposure. Specifically, the study examines the exposure of laser powder bed fused AlSi10Mg (PBF-LB/AlSi10Mg) components to sulphate-reducing bacteria in an anaerobic environment. Is the specific PBF-LB microstructure a potential factor in determining or aiding biocorrosion? A prismatic specimen was exposed to sulphate-reducing bacteria (SRB) for two weeks. The sample was scanned by X-ray computed tomography (XCT) before and after SRB exposure. The two data sets were registered to each other (using the internal void distribution as markers, due to the corrosion of the specimen’s surface) to enable the evaluation of the corrosion damage. Virtual cuts of the 3D XCT reconstructions show a loss of volume and localised damage. The damage distribution aligns with the hatching pattern of laser exposure from laser powder bed fusion. T2 - Konferenz iCT 2026 CY - Linz, Austria DA - 10.02.2026 KW - Computed tomography KW - Biokorrosion KW - Additive manufacturing KW - PBF-LB KW - Laser powder bed fusion KW - Sulphate-reducing bacteria PY - 2026 AN - OPUS4-65570 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bachmann, Marcel A1 - Putra, Stephen Nugraha A1 - Yang, Fan A1 - Meng, Xiangmeng A1 - Pusbatzkies, Pablo A1 - Rethmeier, Michael T1 - Elucidation of the laser beam energy attenuation by the vapor plume formation during high-power laser beam welding N2 - In high-power laser beam welding, a common phenomenon is the formation of a keyhole caused by the rapid evaporation of the material. Under atmospheric pressure, this evaporation generates a vapor plume that interacts with the laser beam, leading to energy attenuation and scattering of the laser radiation along its path. These interactions affect the stability of the process and the overall weld quality. This study investigates the influence of the vapor plume on the weld pool and keyhole dynamics during high-power laser beam welding of AlMg3 aluminum alloy through experimental and numerical approaches. The primary goal is to identify key vapor plume characteristics, particularly its length fluctuations, and to improve the accuracy of the numerical models. To achieve this, an algorithm was developed for the automated measurement of the vapor plume length using high-speed imaging and advanced data processing techniques. The measured plume length is then used to estimate additional vapor heating and laser energy attenuation using the Beer–Lambert law. A refined numerical CFD model, incorporating 3D transient heat transfer, fluid flow, and ray tracing, was developed to evaluate the vapor plume’s impact. Results show that already the time-averaged plume length effectively captures its transient influence and aligns well with experimental weld seam geometries. Additionally, energy scattering and absorption caused by the vapor plume led to a wider weld pool at the top surface. The study also shows an increased percentage of keyhole collapses due to the reduced laser power absorption at the keyhole bottom, further highlighting the importance of accurately modeling vapor plume effects. T2 - International Congress of Applications of Lasers & Electro-Optics 2025 CY - Orlando, USA DA - 12.10.2025 KW - Laser beam welding KW - Vapor plume formation KW - Weld pool KW - Keyhole dynamics KW - Numerical modeling PY - 2026 DO - https://doi.org/10.2351/7.0001863 SN - 1938-1387 IS - 38 SP - 012001-1 EP - 012001-9 PB - Laser Institute of America AN - OPUS4-64949 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tabin, J. A1 - Kawałko, J. A1 - Schob, Daniela A1 - Roszak, R. A1 - Brodecki, A. A1 - Bała, P. A1 - Maasch, philipp A1 - Kowalewski, Z. A1 - Ziegenhorn, M. T1 - Deformation-induced martensitic transformation in fused filament fabrication austenitic stainless steels during tension at wide range of temperatures (77 K, RT) N2 - This study investigates the mechanical behaviour of fused filament fabrication (FFF) of 316L austenitic stainless steel compared to conventional 316L at room temperature and 77 K, focusing on deformation-induced martensitic transformation (DIMT). Results reveal that the Lüders-like effect, present in conventional 316L at 77 K, is absent in FFF 316L due to porosities that hinder martensitic front propagation. At room temperature, uniform strain distribution and DIMT were observed in conventional 316L, whereas in FFF 316L, martensitic nucleation occurred around pores, serving as a localized strengthening mechanism. Microstructural analysis identified Fe-δ islands along grain boundaries in FFF 316L, which contribute to its multiphase nature. Although FFF 316L demonstrates lower yield stress and elongation compared to conventional 316L, this study does not establish design allowables. The present findings are limited to monotonic tensile behaviour, fatigue performance and corrosion resistance under cryogenic conditions were not assessed. Further optimization of fabrication parameters to minimize ferrite content and porosities is suggested to enhance mechanical performance. KW - TRIP effect KW - Fused filament fabrication KW - 316L KW - Cryogenic KW - Cryogenic temperatures KW - Microstructure PY - 2026 DO - https://doi.org/10.1016/j.msea.2025.149552 SN - 0921-5093 VL - 950 SP - 1 EP - 13 PB - Elsevier B.V. AN - OPUS4-65141 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ferrari, Bruno A1 - Fantin, Andrea A1 - Said, D. A1 - Fitch, A. N. A1 - Suárez Ocano, Patricia A1 - Mishurova, Tatiana A1 - Roveda, Ilaria A1 - Kromm, Arne A1 - Darvishi Kamachali, Reza A1 - Bruno, Giovanni A1 - Evans, Alexander A1 - Requena, G. A1 - Agudo Jácome, Leonardo A1 - Serrano Munoz, Itziar T1 - The impact of scanning strategy on cell structures in PBF-LB/M/IN718: an in situ synchrotron x-ray diffraction study N2 - In additive manufacturing, any change of the process parameters, such as scanning strategy, directly affects the cooling rates, heat accumulation, and overall thermal history of the build. Consequently, parts built with different process parameters tend to have different levels of crystallographic texture, residual stress, and dislocation density. These features can influence the properties of the material and their development during post-processing operations. In this study, IN718 prisms were built by laser powder bed fusion (PBF-LB/M) using two different scanning strategies (continuous 67° rotations around the build direction, ROT, and alternating 0°/67° scans, ALT) to provide two different as-built conditions. In situ time-resolved synchrotron diffraction was performed during a solution heat treatment at 1027 °C for 1 h. Ex situ scanning electron microscopy was used to support and complement the in situ observations. An approach to quantify the effect of elemental microsegregation at the cell walls is developed based on the deconvolution of asymmetric γ-nickel matrix peaks. Following this approach, the scanning strategies are shown to affect the as-built fraction of cell walls in the material, resulting in a difference of approximately 5 %, in weight fraction, between ROT and ALT (19 % vs. 24 %, respectively). This microsegregation was observed to be rapidly homogenized during the heating ramp, and no significant changes to the peak shape in the γ peaks occurred during the isothermal part of the heat treatment, regardless of the scanning strategy. KW - Additive manufacturing KW - Inconel 718 KW - Synchrotron x-ray diffraction KW - Heat treatment KW - Laser powder bed fusion KW - Cellular microstructure PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-650958 DO - https://doi.org/10.1016/j.jmrt.2025.11.214 SN - 2238-7854 VL - 41 SP - 593 EP - 608 PB - Elsevier B.V. AN - OPUS4-65095 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Bachmann, Marcel A1 - Rethmeier, Michael A1 - Meng, Xiangmeng T1 - Project title: Multi-physical simulation of the influence of an auxiliary magnetic field on the process porosity formation during high-power laser beam welding N2 - In this project, a multiphysically coupled numerical model will be developed to quantitatively describe porosity reduction in high-power laser beam welding of up to 10 mm thick AlMg3 using an oscillating magnetic field. The aim is to gain fundamental insights into the physical dependencies of the introduced electromagnetic forces on the melt pool behavior and the reduction of porosity. With the help of the numerical model, the transient, multi-coupled, three-dimensional problem of heat transfer, liquid flow, free surface deformation, and magnetic induction is to be solved, taking into account temperature-dependent material properties. The numerical modelling of the heat source will integrate all relevant physical mechanisms, for instance, multiple reflections of the laser radiation by an advanced ray tracing model, as well as local Fresnel absorption at the keyhole wall. This allows an analysis of the keyhole fluctuations, which have a dominant influence on the formation of process spores during deep penetration welding, based on physical principles. In addition, further physical factors such as the ablation pressure of the evaporating metal, the Laplace pressure, and Marangoni shear stresses are also to be integrated into the model. To evaluate the pore formation and reduction by means of the electromagnetic forces introduced in the molten pool, suitable models for describing the movement of the pores in the melt are to be developed. For the process pores, their movement can be implemented by tracking their surface under consideration of their internal pressure and temperature. With the help of the simulation model, all key factors for the formation of process pores during laser beam welding of the used aluminum alloy, as well as their avoidance, can be decoupled and analyzed. Accompanying welding tests are planned at BAM on a 20 kW fiber laser and a 16 kW disk laser. The magnetic flux density will be up to 500 mT at a maximum frequency of 5 kHz. The experimental results, in particular temperature measurements, weld cross sections, computer tomography, and X-ray examinations, will be used to verify the multiphysical model and its calibration. Moreover, the models will be validated and quantified by in situ high-speed imaging of the keyhole dynamics in a metal/quartz glass configuration with keyhole illumination by a diode laser coaxial to the processing laser. On the basis of the numerical and experimental results, the dependencies between applied magnetic field, melt pool behavior, and porosity formation will be revealed in this project. KW - Laser beam welding KW - Electromagnetic weld pool control KW - Numerical simulation KW - Process porosity PY - 2026 DO - https://doi.org/10.34657/27669 SP - 1 EP - 14 AN - OPUS4-65335 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hilgenberg, Kai T1 - EOS M300 as the heart of the QI living lab: Advancing with digital process chains N2 - This presentation shows how the connectivity of the EOS-M300/4 laser powder bed system is used to capture machine and process data as part of the living lab in QI Digital and how this can enable future digital quality assurance in additive manufacturing. T2 - AM Forum 2025 CY - Berlin, Germany DA - 17.03.2025 KW - Additive manufacturing KW - Quality assurance KW - QI Digital KW - Living lab PY - 2025 AN - OPUS4-62740 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Nietzke, Jonathan T1 - H2HohlZug: Standardisation of a New, Cost-effective Method for Material Characterisation for the Hydrogen Economy N2 - The feasibility of the method for slow strain tensile tests has been demonstrated in several studies, leading to the establishment of the ISO/TC 164/SC 1/WG 9 ISO committee for its standardisation. Questions have emerged during this process, that currently prevent the method from being standardised for hydrogen testing. These questions relate to specimen geometry, specimen manufacturing and gas quality and are being systematically addressed in the TransHyDE-H2HohlZug project. T2 - TrasnsHyDE Abschlusskonferenz CY - Berlin, Germany DA - 25.03.2025 KW - Hydrogen KW - Hydrogen Embrittlement KW - High-Pressure Gaseous Gas KW - Hollow Specimen Technique KW - TransHyDE KW - H2HohlZug PY - 2025 AN - OPUS4-62823 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Strauß, Lea A1 - Duarte, Larissa A1 - Kruse, Julius A1 - Madia, Mauro A1 - Löwisch, Günther T1 - An equivalent stress approach for predicting fatigue behavior of additively manufactured AlSi10Mg N2 - Laser-based powder bed fusion (PBF-LB) is an advanced additive manufacturing technique renowned for its precision and capability to fabricate complex metal components. However, the high thermal gradients and rapid cooling rates intrinsic to this process introduce significant process-induced effects, such as inhomogeneities, surface roughness, anisotropy, and residual stress, all of which critically influence the fatigue behavior of the produced parts. This study investigates the fatigue performance of AlSi10Mg samples produced by PBF-LB, examining the impact of varying surface conditions, geometries, and residual stress levels. Fatigue-life prediction models are formulated based on nominal stress amplitude, residual stress, form factor, crack-initiating inhomogeneity, and surface roughness, with smooth samples serving as a baseline reference. The study presents two empirical models for predicting fatigue life and fatigue strength using S–N curves and the Kitagawa–Takahashi diagram with the El Haddad approach, derived from comprehensive experimental data, including finite element modeling, fatigue-life measurements, surface roughness evaluations, and residual stress analysis. KW - AlSi10Mg KW - Kitagawa–Takahashi diagram KW - El Haddad KW - Equivalent stress KW - Fatigue-life prediction KW - PBF-LB/M PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-625176 DO - https://doi.org/10.1007/s40964-025-00974-0 SP - 1 EP - 16 PB - Springer Science and Business Media LLC AN - OPUS4-62517 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Poka, Konstantin A1 - Ali, Sozol A1 - Saeed, Waleed A1 - Merz, Benjamin A1 - Epperlein, Martin A1 - Hilgenberg, Kai T1 - Quality assurance via a cyber physical system of a PBF-LB/M machine N2 - Powder Bed Fusion with Laser Beam of Metals (PBF-LB/M) faces challenges in reproducibility and quality assurance, even for widely applied alloys like AlSi10Mg. This work introduces a digital provenance framework for PBF-LB/M, showcased through the EOS M 300–4 multi-laser machine. An Extract, Transform, Load (ETL) pipeline autonomously captures machine data, including scan vectors as well as process signals, and organizes them into a Digital Shadow (DS). The DS is further extended by external data sources, such as Melt Pool Monitoring (MPM), to enable comprehensive analysis and root cause identification. This approach ensures continuous data representation and facilitates the development of new quality metrics. Moreover, the framework enhances quality assurance and traceability, supports compliance with industry standards, and improves productivity. It also enables more precise cost calculations and predictive maintenance. By addressing these challenges, the framework is essential for advancing PBF-LB/M in industrial applications, achieving greater consistency and scalability in production. KW - PBF-LB/M KW - Data driven quality assurance KW - Data engineering KW - Digital shadow PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-625187 DO - https://doi.org/10.1007/s40964-025-00978-w SN - 2363-9520 VL - 10 IS - 3 SP - 1771 EP - 1783 PB - Springer Science and Business Media LLC AN - OPUS4-62518 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Maasch, Philipp T1 - Numerical Modelling of Deformation-Induced Martensitic Transformation in Additively Manufactured 316L Stainless Steel under Cryogenic Conditions N2 - Cryogenic structural components, including collars, bladders, and keys for superconducting magnets, as well as elements for liquid hydrogen storage systems, are often fabricated from austenitic stainless steel (e.g., 316L) due to favorable mechanical properties and corrosion resistance. However, producing these complex geometries through traditional methods is challenging. Additive manufacturing presents a promising alternative, though the numerical understanding of material behavior under extreme cryogenic conditions remains limited. This study advances the numerical simulation of deformation-induced martensitic transformation (DIMT) in additively manufactured fused filament fabricated (FFF) 316L stainless steel. Central to this effort is the prediction of tensile behavior at temperatures ranging from ambient down to 4K. Supporting experiments—including tensile tests and microstructural characterization via scanning electron microscopy (SEM) and computed tomography (CT)—provide essential input parameters and validation data for the numerical framework. The numerical modelling in this study is based on a nonlinear, temperature-dependent finite element approach incorporating a newly developed constitutive material law. This law couples a phase-kinetic description of the martensitic transformation with a mixed kinematic/isotropic plastic hardening formulation. By solving the underlying conservation laws and boundary conditions while considering temperature-dependent material parameters, the model provides a realistic representation of stress-strain states and evolving martensitic phase fractions across a wide range of thermal conditions. The implementation within a commercial finite element software relies on user-defined subroutines that integrate the constitutive relations and transformation kinetics. The simulations use adaptive time-stepping and iterative strategies to handle highly nonlinear, cryogenic loading scenarios efficiently. After parameter identification through experimental data, the numerical results are systematically compared with measured values from tensile tests and microstructural analyses. This iterative validation process continuously enhances the predictive capability of the model. By merging advanced material-theoretical concepts with robust numerical methods, the presented framework offers deeper insight into the mechanical behavior of additively manufactured austenitic steels under extreme thermal conditions. Ultimately, it supports the targeted design and optimization of cryogenic lightweight components and contributes to the fundamental understanding of material modeling challenges in applied mechanics. T2 - 95th GAMM 2025 Poznan CY - Poznan, Poland DA - 07.04.2025 KW - Constitutive Modelling KW - Deformation-induced martensitic transformation KW - Cryogenic Conditions KW - Fused Filament Fabrication KW - Austenitic stainless steel 316L PY - 2025 AN - OPUS4-63198 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhu, Jiangchao A1 - Madia, Mauro A1 - Schurig, Michael A1 - Kruse, Julius A1 - Conrad, Fabian A1 - Schlums, Hartmut A1 - Kontermann, Christian A1 - Zerbst, Uwe T1 - On the use of representative specimens for the structural integrity assessment of safety-relevant rotating components N2 - Safety-relevant components, for which a failure in service could have catastrophic consequences, are usually designed for extremely low probability of failure and they are subjected to stringent part qualification procedures according to guidelines set by regulatory agencies. Manufacturers are often forced to perform tests on full scale or scaled components to ensure the structural integrity under defined loading conditions, which usually implies a huge experimental and financial effort. Therefore, companies try to develop new strategies such as digital twins, which allow to massively reduce costs, without compromising safety. This work presents a new quasi-static testing and assessment concept, the main idea of which is to replace, or at least reduce, the experimental testing on components by testing specimens representative of the component. Fracture mechanics specimens have been designed iteratively by numerical simulations to match the stress state at the crack-tip of the maximum permissible defect defined by regulatory agencies for the component. Potentially, the major benefit of the proposed approach is that the tests can be performed on conventional laboratory testing machines. The effectiveness of the methodology is demonstrated in case of the structural integrity assessment of a Ni-base superalloy aero-engine turbine disk at overspeed conditions. KW - Structural integrity KW - Turbine disk KW - Burst KW - Fracture mechanics KW - Representative specimens KW - Quasi-static testing PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-624208 DO - https://doi.org/10.1016/j.engfracmech.2024.110710 SN - 0013-7944 VL - 314 SP - 1 EP - 23 PB - Elsevier Ltd. AN - OPUS4-62420 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Madia, Mauro T1 - Influence of defects on the fatigue strength of parts repaired by cold spray N2 - Cold spray repair is a promising and cost-saving alternative to replacing worn parts. Depositing of materials into machined damage volumes in decent quality can restore the performance of refurbished parts and extend their working life. Furthermore, repair counts as resource-efficient and green process in a world targeting at decarbonization of many industrial sectors. Despite the advantages, cold spray repair still suffers from major limitations which prevent its application in safety relevant parts. The main factors influencing the structural integrity concern the adhesion strength, inherent non-bonded internal interfaces, the reduced ductility by work hardening during the manufacturing process, and the presence of residual stresses. This work presents the results of the collaborative project CORE devoted to the development of automatized repair of aerospace parts by cold spray. The investigations considered the aluminum alloy Al6061-T6 which combines medium-high strength, good workability, and high corrosion resistance. Quasi-static tensile tests, high cycle fatigue and fatigue crack propagation tests were performed to compare the performance of base and repaired materials. These were complemented by fractographic and microstructural investigations. T2 - 5th International Symposium on Fatigue Design and Material Defects CY - Trento, Italy DA - 14.05.2025 KW - Cold Spray KW - Component Repair KW - Fatigue Strength KW - Defects KW - Surface Treatment PY - 2025 AN - OPUS4-63146 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa T1 - Application of the cyclic R-curve analysis to determine the Kitagawa-Takahashi Diagram N2 - The fatigue limit of metallic materials corresponds to the maximum stress below which all microcracks that were originally able to grow still arrest. In technical alloys, microcracks are normally initiated at material defects. As a result, the fatigue limit of these materials is a function of the defect size. The Kitagawa-Takahashi Diagram (KT-diagram) provides a useful description of this dependency. However, the established methods for its determination are associated with great uncertainties, especially in the technically interesting region corresponding to the short crack regime. In addition, the effect of crack closure and the influence of local stresses are not considered. For this reason, short crack models offer a better alternative for estimating KT-diagrams. In this work, a methodology is presented that incorporates the determination of the fatigue limit based on crack arrest (cyclic R-curve analysis). The crack driving force is determined by FE simulations, while the increase in material resistance with cyclic crack propagation in the region of physically short cracks is described experimentally by the cyclic R-curve. To validate the procedure, fatigue limit tests based on the staircase method are carried out on smooth and notched specimens with 3 different notch sizes. Furthermore, tests are carried out on a low-alloyed steel with two different heat treatments for considering different strengths. The experimental results are compared with the simulations and the possible differences are discussed. T2 - 5th International Symposium on Fatigue Design and Material Defects CY - Trento, Italy DA - 14.05.2025 KW - Fatigue limit KW - Material defects KW - Kitagawa-Takahashi Diagram KW - Cyclic R-curve analysis PY - 2025 AN - OPUS4-63144 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bär, Jürgen T1 - Determination of the Kitagawa-Takahashi Diagram using DC Potential Drop Measurements N2 - The Kitagawa-Takahashi Diagram is an important tool for describing the fatigue limit of components containing defects. The models used for its description differ, particularly in the transition region corresponding to the short crack regime. Therefore, for a reliable statement about the fatigue limit in this area, an experimental validation of the curve is necessary. However, the standardized stair-case method requires a large number of samples and has a long test duration. In this work, a method is presented that allows a simpler and faster validation of the Kitagawa-Takahashi Diagram in the region of short cracks. Notches with a defined width and depth were manufactured in flat samples of a low-alloyed steel with two different heat treatments using an engraving laser. This method allows to produce very sharp notches without plastic deformation and with only a slight thermal influence on the surrounding material. The samples prepared in this way were fatigued with block wise increasing loads until failure. Cracks are detected by means of a direct current potential drop method. The length of the loading block (number of cycles) is determined by the measured potential drop. This procedure enables a reliable and precise determination of the limit stress for the respective notch size with a low experimental effort and time consumption. T2 - 5th International Symposium on Fatigue Design and Material Defects CY - Trento, Italy DA - 14.05.2025 KW - Fatigue limit KW - Material defects KW - Kitagawa-Takahashi Diagram KW - DC Potential Drop PY - 2025 AN - OPUS4-63145 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröder, Nina T1 - Ti and Nb influence on the HAZ microstructures of weld-simulated high strength structural steel S690QL N2 - High-strength low-alloyed (HSLA) steels with yield strength / proof stress ≥ 600 MP are the basis of modern light-weight steel constructions. Indeed, the economic and ecological benefits strongly depend on their processability in terms of welding. In this context, he use of highly productive welding processes, suitable welding consumables is of vital interest and requires a fundamental understanding of the microstructural changes in the HSLA steel and especially the heat-affected zone (HAZ) of the welded joint. Microalloying elements, such as Ti or Nb, are essential to achieve the desired mechanical properties. In this context, the underlying standards such as EN 10025-6 only specify maximum values, resulting in different manufacturer customized microalloy concepts. Furthermore, even small deviations can have a drastic effect expressed by an excessive hardening or softening despite identical welding conditions and filler metal. The reason is the different thermal stability of the Ti and Nb-related precipitates (typically carbides or carbon nitrides). As a result, it is difficult (or even impossible) to adequately predict the weldability. Against this background, different microalloying routes with varying Ti and Nb contents for a S690QL reference grade were systematically investigated in terms of lab-cast alloys close to realistic chemical compositions. To investigate the influence of the welding heat input on the HAZ microstructure formation, physical simulations were carried with specified peak temperatures and cooling times (by a dilatometer, see Fig. 1a). The focus was the identification of the occurring phase transformations during cooling and the final HAZ microstructure, see Fig. 1b. In this context, a double welding cycle was simulated to further identify the behavior of the so-called intercritical HAZ (where softening is likely to occur) in case of the common multi-layer welding for thick plates, see Fig. 1c. The results showed: (1) microalloying has significant influence on the formation of the individual HAZ dependent on (2) the thermal stability of the Ti or Nb-precipitates and (3) synergistic effects of further elements such as Mo and their effect on phase transformations in the HAZ. The results represent a microstructure-based validation of welding processing of such HSLA-steels e.g. in terms of preferred microalloy and weld heat input combinations. T2 - MaterialsWeek/SteelInnovation 2025 CY - Frankfurt am Main, Germany DA - 02.04.2025 KW - HSLA KW - Dilatometry KW - Microalloying elements KW - HAZ-Softening KW - Digital Image Correlation (DIC) PY - 2025 AN - OPUS4-62938 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hübner, Martin A1 - Reichel, Levin A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Modern welding processes for optimising repair welds on high strength offshore steels N2 - The successful energy transition in Germany will require offshore wind turbines with outputs >10 MW in the future. To achieve these high outputs, turbines far from coast are required with large subsea jacket structures (30 m up to 50 m) and tall towers (up to 200 m). High-strength steels with a yield strength up to 500 MPa and wall thicknesses up to 150 mm are increasingly being used for these structures. This plac-es high demands on welding manufacturing, especially for high-strength offshore steels. During the manu-facturing process detected defects by NDT require localized repair of welds by gouging and rewelding. Due to a lack of investigations, there are no repair concepts and information in standards and guidelines, par-ticularly for high-strength thick plate joints made of high-strength offshore steels. However, these are ur-gently needed to enable manufacturers, especially SMEs, to carry out safe and economical repairs. There-fore, BAM started the FOSTA project P1629 (IGF 01IF22746N) to investigate the stress-optimized repair (local gouging and welding) of high-strength thick plate joints made of offshore grades in the yield strength range off 355 to 460 MPa and similar weld metal with controlled high-performance GMAW pro-cesses and optimized narrow gouging grooves. The experimental analyses take into account the complex interaction of process, material, and design-related influences on the formation of weld induced stresses and the special microstructure of high-strength fine-grain structural steels. Welding-related material degra-dation and crack-critical residual tensile stresses need to be avoided to ensure high component safety and performance. A reduction in residual stress in the presence of high restraint conditions can be achieved by adapted heat control (if no disassembly measures are possible). The repair process involves manual thermal gouging, which allows the groove configuration to be modi-fied. Modern welding processes using high frequency arc control provide deep root penetration and focused energy input capable of welding narrow seams. A comparison was made between the traditional weld con-figuration with a wide 45° groove and transition arc welding and a narrow 30° groove with modern welding process. Even in the case of free shrinkage specimens, the narrow groove weld exhibits a significant reduc-tion of residual stresses, cf. Figure 1, especially in the HAZ and toward the adjacent base material. This can be attributed to the lower weld metal volume needed and the reduction of heat input per layer due to the controlled arc process. For the purposes of this comparison, the same weld seam build-up (but different number of layers) has been applied to both seam configurations. Note that in industrial application (manu-al welding), the wider groove would be welded with several off-center weld beads with conventional weld-ing process. In this analysis this would cause asymmetric effects regarding the residual stress state, diffi-cult to compare to each other. Component-related welding experiments on special testing equipment, adapted process and heat control concepts along with variable groove configurations will be developed and recommendations for guidelines elaborated. This is the prerequisite for fully utilizing the strength potential of high-strength steels and making a valuable contribution to the energy transition in Germany, especially for steel-processing SMEs. T2 - IIW Intermediate Meeting CII CY - Trollhättan, Sweden DA - 10.03.2025 KW - Repair welding KW - Gouging KW - Residual stress KW - Offshore wind turbines KW - High-strength steels PY - 2025 AN - OPUS4-62743 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Fey, Gero T1 - Dilatometer-based welding simulation: CCT-Diagram and investigation of heat-affected zones in pipeline steels N2 - Presentation of the research project “Hydrogen-dependent mechanical properties of the weld microstructure of low-alloy steels for long-distance gas pipelines” and the present results at the Young Professionals International Conference (YPIC) of the International Institute of Welding (IIW) T2 - 2nd Online Young Welding Professional International Conference - YPIC2025 CY - Online meeting DA - 06.02.2025 KW - Pipeline steel KW - CCT KW - Dilatometry KW - Heat-affected zone PY - 2025 AN - OPUS4-62583 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Fey, Gero T1 - Thermophysically Simulated Weld HAZ and CCT Diagram of High Strength Low Alloy Pipeline Steel N2 - This study investigates the suitability of low-alloy pipeline steels for hydrogen transportation, focusing on the development of weld microstructures. Previous research has been limited by a deficiency in the understanding of how different microstructural components respond to trapped hydrogen. By developing Continuous Cooling Transformation (CCT) diagrams through dilatometry analysis, this study explores the impact of t8/5-cooling times (the time between 800 °C and 500 °C) on the microstructure and mechanical properties of the HAZ compared to the base material. The findings provide valuable insights into how cooling times influence transformation temperatures and microstructure development, which, in turn, affect hydrogen diffusion and absorption. These findings establish a foundation for future investigations into hydrogen's impact on weld microstructures, including experimental studies, with the aim of optimizing welding practices and enhancing resistance to hydrogen-assisted cracking. Ultimately, this research contributes to improving the safety and reliability of hydrogen transportation systems in commonly used industrial pipeline steels. T2 - 78th IIW Annual Assembly & International Conference on Welding and Joining CY - Genoa, Italy DA - 22.06.2025 KW - Pipeline steel KW - CCT KW - HAZ KW - Dilatometry KW - Welding KW - L485ME KW - X70M PY - 2025 AN - OPUS4-63752 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Erxleben, Kjell A1 - Kaiser, Sebastian A1 - Rhode, Michael A1 - Kannengiesser, Thomas A1 - Kromm, Arne T1 - In-service and repair welding of pressurized hydrogen pipelines–a review on current challenges and strategies N2 - Hydrogen is the energy carrier for a sustainable future without fossil fuels. As this requires a reliable transportation infrastructure, the conversion of existing natural gas (NG) grids is an essential part of the worldwide individual national hydrogen strategies, in addition to newly erected pipelines. In view of the known effect of hydrogen embrittlement, the compatibility of the materials already in use (typically low-alloy steels in a wide range of strengths and thicknesses) must be investigated. Initial comprehensive studies on the hydrogen compatibility of pipeline materials indicate that these materials can be used to a certain extent. Nevertheless, the material compatibility for hydrogen service is currently of great importance. However, pipelines require frequent maintenance and repair work. In some cases, it is necessary to carry out welding work on pipelines while they are under pressure, e.g., the well-known tapping of NG grids. This in-service welding brings additional challenges for hydrogen operations in terms of additional hydrogen absorption during welding and material compatibility. The challenge can be roughly divided into two parts: (1) the possible austenitization of the inner piping material exposed to hydrogen, which can lead to additional hydrogen absorption, and (2) the welding itself causes an increased temperature range. Both lead to a significantly increased hydrogen solubility in the respective materials compared to room temperature. In that connection, the knowledge on hot tapping on hydrogen pipelines is rare so far due to the missing service experiences. Fundamental experimental investigations are required to investigate the possible transferability of the state-of-the-art concepts from NG to hydrogen pipeline grids. This is necessary to ensure that no critical material degradation occurs due to the potentially increased hydrogen uptake. For this reason, the paper introduces the state of the art in pipeline hot tapping, encompassing current research projects and their individual solution strategies for the problems that may arise for future hydrogen service. Methods of material testing, their limitations, and possible solutions will be presented and discussed. KW - In-service KW - Welding KW - Hydrogen pipeline KW - Review PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-638847 DO - https://doi.org/10.1007/s40194-025-02127-x SN - 0043-2288 SP - 1 EP - 24 PB - Springer Science and Business Media LLC AN - OPUS4-63884 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Liepold, Philipp A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - A Force Based Determination of Hot Cracking Susceptibility N2 - Two high-strength, low-alloy Gas Metal Arc Welding (GMAW) wires were evaluated for their susceptibility to Solidification Cracking (SC) using a modified version of the Transverse Motion Weldability (TMW) test. In theoriginal TMW test, the Transverse Displacement Speed (TDS) is varied iteratively, and crack lengths are measured in each iteration. The modified version eliminates the need for multiple runs by continuously reducing the TDS over a single run. Rather than emphasizing crack lengths, this method assesses the reaction force to the TDS, thereby determining a Critical TDS (CTDS). This critical point directly correlates with the cessation of SC growth. CTDS values were measured under a range of welding parameters, thereby demonstrating the influence of Welding speed and arc energy (U × I/welding speed) on SC susceptibility for the tested filler metals. The CTDS data obtained from this testing method have the potential to provide valuable insights for practical applications in the field. KW - Force based KW - Neural Network KW - TRS PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-640140 DO - https://doi.org/10.5781/JWJ.2025.43.4.10 SN - 2466-2100 VL - 43 IS - 4 SP - 447 EP - 457 AN - OPUS4-64014 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yang, Fan A1 - Meng, Xiangmeng A1 - Putra, Stephen Nugraha A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Numerical studies of process porosity suppression by magnetohydrodynamic technology during the laser beam welding of aluminum alloy N2 - Magnetohydrodynamic (MHD) technology is acknowledged as a promising method for mitigating the porosity defects in laser-welded joints of aluminum alloys. A transient 3D multi-physical numerical model of laser beam welding (LBW), coupled with the MHD and oscillating metal vapor plume model, is developed to study the suppression mechanisms of process porosity by an external magnetic field. The experimental results demonstrate that the porosity ratio is reduced by 93.5 % as the oscillating magnetic field is applied. This significant reduction confirms the effectiveness of the MHD technology in suppressing porosity defects. A downward time-averaged Lorentz force is induced in the weld pool, which affects the fluid flow pattern and the weld pool profile. The change of the flowing pattern in the weld pool by the magnetic field does not always have a positive effect on the porosity suppression. In addition, an analytical model shows that the bubble escape window is expanded by 62 % under the effect of the oscillating magnetic field. The additional upward velocity provided by the electromagnetic expulsive force on the bubbles and the change of weld pool profile are considered favorable factors in eliminating the porosity defects. The numerical and analytical model developed for analyzing the bubble escape window have been validated by experimental results. KW - Laser beam welding KW - Aluminum alloy KW - Process porosity defects KW - Magnetohydrodynamic technology KW - Bubble escape KW - Numerical simulation PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-637642 DO - https://doi.org/10.1016/j.ijheatmasstransfer.2025.127525 SN - 0017-9310 VL - 253 SP - 1 EP - 13 PB - Elsevier Ltd. AN - OPUS4-63764 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yang, Keke A1 - Wang, Zhuoqun A1 - Haak, Viktor A1 - Olfert, Viktoria A1 - El-Sari, Bassel A1 - Hein, David A1 - Biegler, Max A1 - Rethmeier, Michael A1 - Meschut, Gerson T1 - A novel welding schedule for expanding the expulsion-free process window in resistance spot welding of dissimilar joints with ultra-high strength steel N2 - This study introduces a novel approach to expanding the maximum expulsion-free process window in resistance spot welding (RSW) of dissimilar joints between ultra-high strength steel (UHSS) and mild steel. Quantitative analysis revealed that expulsion is driven by the interaction between nugget growth rate and plastic shell thickness. Based on this finding, the welding schedule was optimized by applying a preheating current to form an initial plastic shell, followed by a ramp-up current profile during the main welding phase. Welding simulations indicated that the ramp-up current slowed nugget growth, improved plastic shell formation, and prevented nugget breakthrough, thereby reducing the risk of expulsion. Experimental validation showed a 19 % increase in maximum expulsion-free heat input, with the nugget diameter increasing by 7.6 % to 8.94 mm compared to the reference welding schedule. Furthermore, even when expulsion occurred beyond the process window, this optimization delayed its occurrence, minimizing its impact on spot weld quality. Finally, the optimized welding schedule also exhibited significant robustness. Despite a 2 mm initial gap disturbance, the maximum expulsionfree heat input increased by 57 %, while the nugget diameter grew by 30 % to 8.92 mm. These results confirm that the proposed approach effectively extends the process window by preventing expulsion and enhances process stability. KW - Expulsion KW - Resistance spot welding KW - Finite element modelling KW - Preheating KW - Ultra-high-strength steel PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-626877 DO - https://doi.org/10.1016/j.jmapro.2025.02.009 SN - 2212-4616 VL - 137 SP - 306 EP - 309 PB - Elsevier BV AN - OPUS4-62687 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Iskhakov, Tagir T1 - Computational modeling of temperature compensation for eddy current testing during PBF-LB/M N2 - The laser powder bed fusion (PBF-LB/M) process enables the production of highly customized parts with complex geometries. However, the mechanical performance of additively manufactured parts can be compromised by the presence of microstructural inhomogeneities. To address this issue, a reliable process monitoring tool is required to detect these flaws and improve part quality. Eddy current testing presents a promising solution for such monitoring. However, the high temperature gradients within the manufactured specimen affect the electrical conductivity of the material, which, in turn, influences the eddy current testing performance. Therefore, accurately predicting the temperature distribution is essential for reliable flaw detection, which is the focus of this work. In this study, a Finite Element (FE) transient thermal model is developed to predict the temperature field in multipart build jobs. In this model, scan vectors are grouped into clusters based on their timestamps, enabling the homogenization of thermal loads from multiple scan vectors. When a single cluster is used, the thermal load is applied to the entire layer in a single step. Increasing the number of clusters per layer — and thus the number of steps — enhances the accuracy of temperature predictions. This approach allows for optimizing the trade-off between modeling accuracy and computational efficiency. The study evaluates the prediction accuracy required for eddy current testing and investigates the optimal number of clusters (i.e., the adequate level of homogenization) needed to achieve this accuracy. The model predictions are validated through comparison with thermography images and thermocouple measurements. Finally, the concept of eddy current testing with simulation-based temperature compensation is evaluated on specimens with simple geometries. T2 - SIM-AM 2025 CY - Pavia, Italy DA - 09.09.2025 KW - Eddy current testing KW - FEM KW - 316L PY - 2025 AN - OPUS4-64121 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erxleben, Kjell T1 - Component test for the assessment of in-service welding on/onto pressurized hydrogen pipelines N2 - Hydrogen is seen as the energy carrier of the future. Therefore a reliable infrastructure to transport hydrogen in a large scale is needed. A so called European hydrogen backbone out of long distance transmission pipelines is planned by European countries to create a hydrogen transport infrastructure. Due to economic reasons this will be achieved by new build pipelines such as repurposed natural Gas (NG) pipelines, converted to hydrogen useage. A general suitability for hydrogen service of low alloyed pipeline steel, as it is used for NG service today, is given. But in case of necessary in-service welding procedures in terms of e.g. hot-tapping and stoppling, the risk of a critical hydrogen uptake into the pipe materials due to much higher temeperatures while welding and the possibility of hydrogen embrittlement (HE) needs to be closely investigated. The presentation gives an overview of the current H2-SuD project, investigating the feasability of in-service welding on future hydrogen pipelines. Therefore, component-like demonstrators were developed to test (I) the additional hydrogen uptake due to in-service welding under hydrogen pressure and (II) to measure the temperature field due to different welding parameters and demonstrator geometries, especially on the inner pipe wall surface. Collected data will be used to validate a numerical simulation of the thermal field and additionally the hydrogen diffusion in the pipeline material. T2 - Presentation at The University of Manchester CY - Manchester, United Kingdom DA - 12.09.2025 KW - In-service KW - Hydrogen KW - Pipeline KW - Welding PY - 2025 AN - OPUS4-64129 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Numerical simulation of weld heat input effect on microstructure and hydrogen diffusion in thick-walled S690 submerged arc welded joints N2 - High-strength, low-alloy (HLSA) steels such as S690 are an attractive option for heavy industries such as offshore wind turbines and peripheral equipment due to their combination of excellent mechanical properties and weldability. The construction of these thick-walled structures requires highly efficient welding processes such as submerged arc welding (SAW). However, SAW presents challenges related to delayed hydrogen assisted cold cracking (HACC). Despite its importance, the effect of different diffusion coefficients on the cold cracking susceptibility of different microstructures within SAW-welded S690 steels is not fully understood. For this reason, the present study focuses on comparing the cold cracking susceptibility of thermomechanically rolled (TM) or quenched and tempered (QL) variants of S690 steel. SAW was performed on specimens of both steel grades to produce weldments consisting of weld metal, heat-affected zone (HAZ), and base metal. Electrochemical hydrogen permeation tests (ISO 17081) were performed to determine the microstructure specific coefficients. Using the obtained coefficients, a numerical model was developed to identify the time- and microstructure-dependent local hydrogen diffusion and its influence on the distribution within the welds. The results showed that the TM grade exhibited slightly accelerated hydrogen diffusion compared to the QL grade, which is beneficial for hydrogen reduction and increases the HACC resistance. However, the further simulations with different ply sequences showed that the welding heat input (i.e. welding ply sequence) had a significantly higher effect on hydrogen accumulation. Specifically, increased welding heat input and increased thicknesses decrease hydrogen diffusivity. For this reason, microstructure-specific hydrogen diffusion played a minor role in thick-layer SAW joints compared to the need to control the welding parameters (layer sequence, individual layer thickness, welding heat input). T2 - FEMS Euromat 2025 - 18th European Congress and Exhibition on Advanced Materials and Processes CY - Granada, Spain DA - 15.09.2025 KW - Hydrogen assisted cracking KW - Welding KW - High strength steels KW - Numerical simulation KW - Electrochemical permeation PY - 2025 AN - OPUS4-64158 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Hydrogen trap characterization in 200 and 1,000 bar charged CoCrNi medium entropy alloy compared to steel AISI 316L N2 - Multiple principal element alloys (MPEAs) represent a new class of metallic materials. MPEAs, such as the CoCrNi medium entropy alloy (MEA), have attracted considerable research attention as potential materials to replace, for example, austenitic steels in high-pressure hydrogen environments. Due to the relatively new alloy concept, studies on the specific hydrogen diffusion and trapping behavior of high-pressure hydrogen-charged CoCrNi MEAs are rare so far. For this reason, a CoCrNi-MEA was investigated and compared to an austenitic stainless steel, AISI 316L. Both materials were subjected to high pressure hydrogen loading for two different pressures: 200 bar and 1,000 bar. After charging, thermal desorption analysis (TDA) was used with three heating rates from 0.125 K/s to 0.500 K/s to clarify the specific hydrogen desorption and trapping behavior. To the best of our knowledge, this study is the first to characterize hydrogen diffusion and trapping in 1,000 bar high-pressure charged CoCrNi. For this purpose, the underlying TDA spectra were analyzed in terms of peak deconvolution into a metallurgically justifiable number of defined peaks. The individual peak temperatures and activation energies “EA” were calculated. The following conclusions can be drawn from the results obtained: (1) Exposure to 200 bar or 1,000 bar leads to an increase in hydrogen absorption, regardless of the material investigated, expressed by a significantly increased desorption rate at 1,000 bar. However, the effusion peaks typically occur only at high temperatures. The (2) TDA showed that a four-peak deconvolution scenario was sufficient to describe the trapping behavior and the "EA" indicated the dominance of irreversible traps. In addition, the average trapping energy is higher than in the 316L. The (3) charge pressure related hydrogen solubility was in the order of: CoCrNi-MEA < 316L for both pressures and (4) charging at 1000 bar results in an average concentration of 49 wt.ppm (CoCrNi-MEA) and > 75 wt.ppm (316L). In summary, the CoCrNi-MEA was characterized by a reduced solubility, but very deep entrapment compared to the 316L. For this reason, further application potentials of the MEA may arise. T2 - FEMS Euromat 2025 - 18th European Congress and Exhibition on Advanced Materials and Processes CY - Granada, Spain DA - 15.09.2025 KW - Medium entropy alloy KW - Hydrogen KW - Trapping KW - Diffusion KW - High-pressure charging PY - 2025 AN - OPUS4-64160 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Effect of Ti and Nb on hydrogen trapping in welded S690 HSLA steel and effect on delayed cold cracking N2 - Fine-grain, high-strength, low-alloy (HSLA) structural steels with yield strengths > 600 MPa are now the state of the art in construction applications such as mobile cranes and civil engineering. HSLA grades derive their strength from a combination of specific heat treatment and the underlying chemical composition. In this context, Ti or Nb are essential to obtain a fine-grained microstructure as well as the necessary carbides or nitrides for precipitation strengthening. In this context, the specific effect of Ti or Nb-rich compounds on hydrogen trapping and diffusion is well known for special laboratory cast alloys, but unknown for realistic steel compositions. For this reason, a series of S690Q-based alloys were synthesized, close to a real steel composition, but with well controlled Ti or Nb additions in different amounts. Specimens were obtained from these alloys by electrochemical discharge machining (EDM). The specimens were tested using the well-established electrochemical permeation technique. From the experimental results, the hydrogen diffusion coefficients and the analytical subsurface hydrogen concentration were calculated. In addition, the hydrogen trapping behavior at elevated temperatures was interpreted by thermal desorption analysis (TDA) using different heating rates of hydrogen charged samples. The results showed that in contrast to metallurgically "pure" laboratory cast alloys, realistic chemical compositions were similar in their hydrogen trapping behavior, despite some small differences. All investigated steel grades exhibited shallow and reversible hydrogen trapping, regardless of their chemical composition. Of course, the experiments only allowed the calculation of effective diffusion coefficients and trapping energies, which represent an average of the entire microstructure. Nevertheless, HSLA steels are typically joined by arc welding, which includes the risk of delayed hydrogen assisted cracking. From the point of view of welding practice, however, a more or less identical hydrogen diffusion behavior means that no special "metallurgically specific", justifiable measures need to be considered, despite the well-established processes such as "soaking" or dehydrogenation heat treatment. Of course, a closer look at the heat-affected zone (HAZ) or the weld metal of the specific welds is necessary. However, especially in the case of thick-walled welds, it is assumed that the weld metal and HAZ are similar to the base material due to the multi-layer welding, which results in multiple annealing cycles of the weld metal and HAZ. T2 - FEMS Euromat 2025 - 18th European Congress and Exhibition on Advanced Materials and Processes CY - Granada, Spain DA - 15.09.2025 KW - Hydrogen assisted cracking KW - HSLA KW - Diffusion KW - Electrochemical permeation PY - 2025 AN - OPUS4-64156 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Component test for the assessment of in-service welding on/onto pressurized hydrogen pipelines N2 - Hydrogen is the energy carrier of tomorrow and requires a reliable large-scale transport infrastructure. In addition to new pipelines, the conversion of existing natural gas (NG) pipeline grids is an essential part. The transport of hydrogen is fundamentally different from that of NG, as hydrogen can be absorbed into the pipeline material. Given the effects of hydrogen embrittlement, the material compatibility (low alloy steels in a wide range of strengths and thicknesses) must be investigated. However, pipelines e.g. require maintenance or the need for installation of additional outlets with the necessity of welding on/onto the pipelines while they are still in service, i.e. with gas flow under high pressure, such as the well-known "hot tapping". This in-service welding poses challenges for hydrogen operations. The challenge can be roughly divided into the possible austenitization of the inner pipe material exposed to hydrogen, the welding itself, which causes an increased temperature range. Both lead to a significant increase in hydrogen solubility and diffusivity compared to room temperature. In addition, possible surface reactions of the present iron oxides (e.g. magnetite or hematite) with the hot hydrogen should be considered. In this context, the knowledge of hydrogen pipelines is scarce due to the lack of operational experience. Fundamental experimental investigations are required to investigate the transferability from NG to hydrogen pipeline grids. For this reason, the present study presents a specially designed mock-up / demonstrator concept for the realistic assessment of the welding process conditions. The mock-up was designed to allow in-situ temperature measurement during the welding process as well as ex-post sample extraction for quantification of the absorbed hydrogen concentration. For safety reasons, the required volume of pressurized hydrogen was limited by inserting a solid cylinder to ensure a 1 cm thick layer of hydrogen gas. Welding experiments on the DN60 and DN200 pressurized mock-ups showed the possibility of safe welding on or onto pressurized hydrogen pipelines. Indeed, the austenitizing temperature was reached on the inner surface of the pipeline, especially on thinner-walled pipelines, using current welding parameter recommendations. This corresponded to an increased hydrogen uptake in the welded area of several ppm. From this point of view, the suggested component concept is a viable strategy for the screening of several materials and welding parameter combinations under realistic operational conditions. T2 - FEMS Euromat 2025 - 18th European Congress and Exhibition on Advanced Materials and Processes CY - Granada, Spain DA - 15.09.2025 KW - In-service welding KW - Pipeline KW - Hydrogen KW - Component test PY - 2025 AN - OPUS4-64159 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Component-test for determination of welding residual stresses and their effect on stress relief cracking in thick-walled welds N2 - Controlling the residual stress level during welding of creep-resistant Cr-Mo-V steels is crucial to avoid so called stress relief cracking (SRC) during post weld heat treatment (PWHT) of large-scale components. In the present study, a laboratory scale test specimen (slotted sample with 400 mm width, 400 mm length and 25 mm thickness) was used to simulate thick-walled component welds made of 13CrMoV9-10. The aim was to identify the level and distribution of residual stresses to evaluate the suitability of the specimen for laboratory based SRC testing. High restraint was ensured by the specimen geometry with a narrow welding gap in the center. This gap was filled by multi-layer submerged arc welding. Two specimens were welded with identical parameters and compared in the as-welded state and after PWHT (705 °C for 10 h). Neutron diffraction was used to determine the residual stresses in the weld metal, the heat-affected zone (HAZ) and the base material at different depths longitudinal, transverse, and normal to the welding direction. The experiments were performed on the former instrument E3 of the research reactor BER II of Helmholtz-Zentrum Berlin (HZB), Germany. Complementarily, laboratory X-ray diffraction was applied to characterize the surface residual stresses. In the welded condition, especially in the weld metal and the adjacent HAZ, the longitudinal residual stresses reached values of up to 1,000 MPa to 1,200 MPa due to the increasing strength and hardness of the CrMoV-material during welding. The conducted welding experiments revealed that way higher residual stresses in the welded joint have to anticipated before the PWHT is performed than it was expected in advance. This demonstrated the necessity of suitable component-like welding tests as they must ensure realistic mechanical stiffness (hindered shrinkage of welding joint by slotted self-restraint sample) and heat dissipation conditions (definition of minimum welding joint thickness vs. welding process-specific heat input). T2 - FEMS Euromat 2025 - 18th European Congress and Exhibition on Advanced Materials and Processes CY - Granada, Spain DA - 15.09.2025 KW - Component test KW - Submerged arc welding KW - Post weld heat treatment KW - Residual stresses KW - Neutron diffraction PY - 2025 AN - OPUS4-64161 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Geranmayeh, Ali T1 - Laser Metal Deposition of NiTi Shape Memory Alloys: Influence of Process Parameters on Thermal Profiles and Part Properties N2 - Laser Metal Deposition (LMD), a laser powder–directed energy deposition technology (LP-DED), offers unique flexibility for fabricating complex metallic components. Among candidate materials, Nitinol (NiTi) is particularly attractive due to its shape memory and superelastic properties, though its high sensitivity to processing conditions demands precise parameter control. In this work, prealloyed NiTi powder was deposited as single tracks, and process parameters were optimized using a Design of Experiments methodology. A Central Composite Design (CCD) was implemented with laser power, scan speed, and powder feed rate as inputs, while track’s height, width, aspect ratio, and dilution served as optimization responses. To address the strong susceptibility of NiTi to heat accumulation, hatch spacing was further optimized using a geometrically derived formula, enabling the use of maximum spacing while ensuring dense parts with smooth surfaces and minimal waviness. The presented framework establishes a systematic route for parameter optimization in NiTi LMD, offering practical guidelines for balancing densification and surface quality. T2 - WGF Assistant Seminar CY - Rechenberg-Bienenmühle, Germany DA - 10.09.2025 KW - Additive manufacturing KW - Shape memory alloys KW - Nitinol KW - Laser metal deposition KW - Design of experiments PY - 2025 AN - OPUS4-64164 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yalçınyüz, Aybike A1 - Raute, Julius A1 - Gonzalez-Gutierrez, Joamin A1 - Pei, Eujin A1 - Biegler, Max A1 - Rethmeier, Michael T1 - Electron Beam Bonding: A novel method for joining additively manufactured carbon fiber thermoplastic composites with aluminum to produce multi-material joints for lightweight applications N2 - In recent years, new solutions have been explored to reduce the weight of components for the automotive, railway, and aerospace industries. For this reason, Carbon Fiber Composites (CFCs) have increasingly replaced metals in products that need to be lightweight. However, due to their poor thermal conductivity, CFCs have limited use in applications requiring efficient heat dissipation. In such applications, conventionally manufactured metal alloys are typically utilized. To address these limitations, a novel approach using a combination of additively manufactured aluminum and CFCs is proposed to exploit the distinct advantages of both materials. These innovative hybrid structures aim to combine good structural and thermal management properties with reduced weight compared to conventionally produced metal products. In this study, additively manufactured aluminum alloy (AlSi10Mg) and short carbon fiber Polyamide 6 composite (sCF-PA6) are utilized to produce metal–polymer pairs using electron beam energy to bond the two materials. Direct irradiation of short CFCs with electron beam leads to polymer degradation. Thus, a novel method “Electron Beam Bonding” for joining CFCs with aluminum alloy in various joint configurations using electron beam technology is demonstrated. This innovative approach presents a promising solution for creating metal–polymer multi-materials for lightweight applications. KW - Electron beam bonding KW - Multi-material KW - Lightweight KW - Additive manufactured materials KW - Short carbon fiber composites KW - AlSi10Mg KW - Joining PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-641705 DO - https://doi.org/10.1007/s40964-025-01206-1 SN - 2363-9512 SP - 1 EP - 7 PB - Springer International Publishing CY - Cham AN - OPUS4-64170 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meng, Xiangmeng A1 - Bachmann, Marcel A1 - Yang, Fan A1 - Rethmeier, Michael T1 - Toward prediction and insight of porosity formation in laser welding: A physics-informed deep learning framework N2 - The laser welding process is an important manufacturing technology for metallic materials. However, its application is often hindered by the occurrence of porosity defects. By far, an accurate prediction of the porosity defects and an insight into its formation mechanism are still challenging due to the highly nonlinear physics involved. In this paper, we propose a physics-informed deep learning (PIDL) framework by utilizing mechanistic modeling and experimental data to predict the porosity level during laser beam welding of aluminum alloys. With a proper selection of the physical variables (features) concerning the solidification, liquid metal flow, keyhole stability, and weld pool geometry, the PIDL model shows great superiority in predicting the porosity ratio, with a reduction of mean square error by 41 %, in comparison with the conventional DL model trained with welding parameters. Furthermore, the selected variables are fused into dimensionless features with explicit physical meanings to improve the interpretability and extendibility of the PIDL model. Based on a well-trained PIDL model, the hierarchical importance of the physical variables/procedures on the porosity formation is for the first time revealed with the help of the Shapley Additive Explanations analysis. The keyhole ratio is identified as the most influential factor in the porosity formation, followed by the downward flow-driven drag force, which offers a valuable guideline for process optimization and porosity minimization. KW - Laser beam welding KW - Physics-informed deep learning KW - Porosity prediction KW - Feature fusion KW - Hierarchical importance PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-624708 DO - https://doi.org/10.1016/j.actamat.2025.120740 VL - 286 SP - 1 EP - 13 PB - Elsevier B.V. AN - OPUS4-62470 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Akyel, Fatma A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Brunner-Schwer, Christian A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Influence of heat input on cooling rates and mechanical properties of laser hybrid welded thick structural steels N2 - Laser hybrid welding presents several challenges when used to weld thick steels. A typical weld is divided into the arcdominated and laser-dominated zone. These zones lead to variations in the mechanical properties of the weld. The laserdominated zone is of particular importance regarding mechanical properties, notably Charpy impact toughness, due to the high cooling rates and the absence of filler wire. The low heat input of the laser can lead to martensitic microstructure causing hardening and deterioration of impact toughness. The high heat input of the arc can lead to grain coarsening and even loss of impact toughness. This study examines the influence of heat input on the cooling rates, microstructure and mechanical properties of single-pass laser hybrid welded steels of S355J2 and EH36 with thicknesses up to 30 mm. The experiments were performed with a 20-kW fibre laser and a contactless electromagnetic weld backing in the butt-joint configuration in 1G welding position. The cooling time was measured in three different locations near the fusion lines corresponding to different heights of the seam using a special configuration with pyrometers, collimators and optical fibres. The test specimens for the Charpy impact testing and tensile testing were extracted in three different depths. The experiments indicated that a heat input of 1.6 kJ/mm–2 kJ/mm, 2 kJ/mm–2.4 kJ/mm and 3.7 kJ/mm were recommended when single-pass laser hybrid welding of 20-, 25-, and 30-mm-thick structural steels regarding the minimum requirements of the mechanical properties, respectively. KW - Laser hybrid welding KW - Heat input KW - Mechanical properties KW - Charpy impact toughness KW - Cooling rate PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-625282 DO - https://doi.org/10.1007/s40194-025-01924-8 SN - 1878-6669 SP - 1 EP - 15 PB - Springer CY - United Kingdom AN - OPUS4-62528 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Jonathan T1 - Near-real-time in-situ powder bed anomaly detection using machine learning algorithms for high-resolution image analysis in PBF-LB/M N2 - In-situ captured visual images of the laser powder bed fusion process (PBF-LB/M) provide valuable insights into process dynamics. Automatic analysis of after-recoating images using machine learning algorithms enables the detection of process deviations to reduce scrap production. However, current industrial monitoring systems for PBF-LB/M are limited by low image resolution. While higher resolutions enable the system’s ability to capture smaller features, they increase storage and computational demand. Edge devices offer a solution by enabling near-real-time, on-premises image analysis within the machine and company network. In this study, high-resolution after-recoating images, captured with a spatial resolution of 17 µm/pixel and an image size of 9344 x 7000 pixels, were processed on an Nvidia Jetson Orin NX16 edge device. The images were downscaled, and anomaly detection algorithms were used to identify regions of interest for segmentation and classification at full resolution. To address computational constraints, state-of-the-art anomaly detection algorithms were evaluated and an appropriate downscaling factor for the on-edge implementation was determined. The EfficientAD algorithm achieved promising results, detecting anomalies within an inference time of less than 10 seconds. The presented framework enables anomaly detection with a maximum delay of one layer. This lays the foundation for the future development of near-real-time intervention in the PBF-LB/M process. T2 - ISAM 2025 – 6th International Symposium on Additive Manufacturing CY - Dresden, Germany DA - 21.05.2025 KW - Additive manufacturing KW - Image processing KW - In-situ monitoring KW - Powder bed fusion PY - 2025 AN - OPUS4-63231 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schob, Daniela T1 - Numerical and Experimental Investigation of Deformation Induced Martensitic Transformation in Fused Filament Fabricated Austenitic Stainless Steel for Cryogenic Applications N2 - Cryogenic structural components, such as collars, bladders, keys for superconducting magnets, and elements of liquid hydrogen storage systems like hoses and valves, are frequently constructed from austenitic stainless steel due to its favorable properties. However, manufacturing these components using traditional methods is challenging due to their complex geometries. Additive manufacturing emerges as a promising solution, though a comprehensive understanding of the associated material behavior under extrem e conditions is still developing. This study aims to explore the deformation induced martensitic transformation (DIMT) in fused filament fabricated (FFF) 316L stainless steel through both experimental testing and numerical simulation. The research focuses on predicting the material’s respo nse under tensile stress at ambient, 77K, and 4K temperatures. Numerical simulations employ a finite element approach to incorporate the constitutive model and its temperature dependent phase transformation kinetics, enabling detailed investigation of stress and strain distributions at various cryogenic temperatures. These simulations are systematically calibrated and validated against corresponding experimental datasets, ensuring that the computational predictions mirror the observed microstructural evolution and macroscopic response under tensile loading. By comparin g simulation results to experimental findings obtained at temperatures from room temperature down to 4K, the reliability of the model can be assessed, and its predictive capabilities can be refined. Ultimately, the research seeks to expand the understanding of DIMT in additively manufactured 316L components, supporting the development of advanced, simulation driven material models tailored for demanding cryogenic structural applications. T2 - Cryogenic Engineering Conference (CEC) and International Cryogenic Materials Conference (ICMC) CY - Reno, NV, USA DA - 18.05.2025 KW - Phase transformation KW - Deformation induced martensitic transformation KW - 316L KW - Fused Deposition Modelling PY - 2025 AN - OPUS4-63238 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ulbricht, Alexander T1 - Do Microbes like Additively Manufactured Aluminium? First Details of a Corrosion Test using Sulphate-Reducing Bacteria N2 - Additively manufactured metals become relevant for industrial application. Although many studies on wet corrosion of these metals have been conducted, to the authors knowledge no study seems to contain microbiological corrosion (MIC). In the presented study an experiment was conducted on PBF-LB/AlSi10Mg to test this material's susceptibility for MIC. The tested specimen were analysed using Computed Tomography before and after the MIC experiment to enable a detailed characterisation the damage on the specimens' global and local level. A global reduction of material was observed. In addition, localised damage along process inherent features of the materials microstructure was observed. T2 - Beiratssitzung TF Umwelt CY - Berlin, Germany DA - 17.03.2025 KW - Computed Tomography KW - Additive Manufacturing KW - Biocorrosion KW - Sulphate-reducing Bacteria KW - Microbially influenced corrosion PY - 2025 AN - OPUS4-62772 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Fey, Gero T1 - Thermophysically Simulated Weld HAZ and CCT Diagram of� High Strength Low Alloy Pipeline Steel N2 - Kurzvorstellung der laufenden Projekte "Wasserstoffabhängige mechanische Eigenschaften der Schweißnahtgefüge niedriglegierter Stähle für Ferngasleitungen" und "Praktikable Prüfung geschweißter Ferngasleitungen aus niedrig-legierten Stählen für den sicheren Transport von Wasserstoff" mit kurzem Ergebnisstand und zukünftiger Versuchsplanung/Outlook T2 - Sitzung des NA 092-00-05 GA "Gemeinschaftsarbeitsausschuss NAS/NMP: Zerstörende Prüfung von Schweißverbindungen (DVS AG Q 4/Q 4.1)" CY - Online meeting DA - 20.03.2025 KW - ZTU-Diagramm KW - CCT KW - WEZ KW - Dilatometry KW - Pipeline Steel PY - 2025 AN - OPUS4-63107 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Willeke, Maraike A1 - Giese, Marcel A1 - Lorenz, Swenja A1 - Treutler, Kai A1 - Schröpfer, Dirk A1 - Wesling, Volker A1 - Kannengießer, Thomas T1 - Effect of alloy modification on the wear protection coatings made of Ni- and Co-based materials and surface machinability via ultrasonic milling process N2 - AbstractWear-resistant coatings are required for highly efficient and economical steel components in equipment, process, and power plant engineering to withstand high corrosive, tribological, thermal, and mechanical stresses. Co-alloys are used as wear-resistant coatings for steel components, tailored to the specific application. The substitutability of Co alloys with Ni-based wear protection systems, in addition to price and supply uncertainties, is facilitated by the combination of innovative welding and machining processes such as ultrasonic-assisted milling. The aim of the study is to improve the machinability of two different hard-facing alloys while maintaining the same wear protection potential. Therefore, the wear-resistant alloys NiMoCrSi (Colmonoy C56) and CoMnCrSi (Tribaloy T400) were modified by the alloying additions Nb, Hf, and Ti and then applied to a carbon-manganese steel S355 using the plasma transfer arc (PTA) welding process. The influence of the alloying additions on the microstructure as KW - Wear resistance KW - Co-based alloy KW - Ni-based alloy KW - PTA welding process KW - Ultrasonic assisted milling process PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-623931 DO - https://doi.org/10.1007/s00170-024-14955-0 SN - 0268-3768 SP - 1 EP - 17 PB - Springer Science and Business Media LLC AN - OPUS4-62393 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Liepold, Philipp A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Transvarestraint testing of high-strength steel filler metal N2 - High-strength steel welds are typically not known to be susceptible to Solidification Cracking (SC). However, modern light-weight constructions may force welding in highly restrained conditions, which are known to increase the probability of Solidification Crack (SC) emergence. In this article, the Modified Varestraint-Transvarestraint (MVT) test was used to evaluate the hot cracking susceptibility of welds made from high-strength, low-alloyed filler material. The materials tested include solid wires and a metal-cored wire. All wires are typically used in the Gas Metal Arc Welding (GMAW) process. Susceptibility to SC was measured over a wide range of welding parameters and bending speeds. Results show little affinity of the tested materials to SC. However, crack length increases in most cases with arc energy ( U ∙ I∕welding speed ) and welding speed. The length of the longest crack in one test specimen follows a similar trend until high welding speeds, where stagnation of crack length with changing arc energy was observed. KW - MVT KW - Varestraint KW - Transvarestraint KW - Solidification cracking KW - High-strength steel PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-630084 DO - https://doi.org/10.1007/s40194-025-02042-1 SN - 1878-6669 VL - 2025 SP - 1 EP - 12 PB - Springer CY - Berlin ; Heidelberg AN - OPUS4-63008 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Influence of residual stresses and heat control on stress relief cracking in a CrMoV steel mockup N2 - Preventing failures in the manufacture or operation of petrochemical reactors made from creep-resistant, low-alloy steels such as 13CrMoV9-10 still requires research, despite over 60 years of investigation into the field of stress relief cracking. Welding this steel grade requires care. This is due to its low toughness and high strength in the welded condition if not heat treated after welding, combined with an increased susceptibility to cracking during stress relaxation. Previous research on cracking in creep resistant steels has focused on thermal and metallurgical factors; however, little knowledge has been gained on cracking under real-life restraint conditions. In this work, the influence of welding heat control on cracking was investigated by simulating the manufacturing conditions prevailing in the construction of petrochemical reactors using a special weld mockup. The application of acoustic emission analysis showed that cracks formed during post-weld heat treatment in a temperature range between 300 °C and 500 °C. Compared to small scale samples, the toughness of the restrained welds was significantly lower. SEM and TEM analyses of all samples revealed early ageing due to early precipitation of special carbides during post-weld heat treatment under restraint. Neutron diffraction experiments showed that the residual stresses in the weld seam reach the yield point of the material. The presentation provides an overview of how a comprehensive assessment of the integrity of submerged arc welded CrMoV steels can be achieved in the laboratory. T2 - Cracking Phenomena in Welding and Additive Manufacturing 2025 CY - Trollhättan, Sweden DA - 12.03.2025 KW - CrMoV KW - Stress Relief Cracking KW - Sub-merged arc welding PY - 2025 AN - OPUS4-62783 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Fey, Gero A1 - Schröder, Nina T1 - Challenges in the evaluation of the weldability of old mild steels for future use N2 - This study concentrates on two selected different old steels Samples from pressure tank construction , designated Old_A and a sample of a riveted construction , designated Old_E from the first half of 20th century. The study contains analysis results for their microstructure in the ‘as delivered condition’, chemical composition and their expected behaviour during welding. By means of dilatometry, a supplementary database was created (weld CCT diagrams, weld simulated HAZ micro structures), which enables the derivation of systematic practice relevant welding experiments. T2 - IIW Intermediate Meeting CY - Trollhättan, Sweden DA - 10.03.2025 KW - Old mild steel KW - Weldability KW - CCT KW - Dilatometry PY - 2025 AN - OPUS4-63105 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Griesche, Axel T1 - Laser-Induced Breakdown Spectroscopy (LIBS) for Hydrogen Measurements in Steel N2 - Laser-induced breakdown spectroscopy (LIBS) allows for a time and spatially resolved almost non-destructive in situ measurement of hydrogen in metals. A surface pretreatment is not necessarily needed. We measured quantitatively hydrogen in steel samples, which were charged either electrochemically or by high-pressure hydrogen gas and compared the results. Further, the feasibility of quantitative hydrogen line scan measurements was demonstrated by measuring hydrogen at water jet cut surfaces. The hydrogen concentrations measured with the help of LIBS were compared with CGHE measurements. It was observed that hydrogen can be reliably measured with LIBS for concentrations larger than 2 wt.-ppm. The results show that LIBS is a promising technique for time- and spatially resolved measurements of hydrogen in steel and steel weldments. Results of time-dependant hydrogen permeation experiments will also be presented. T2 - H2MSE 2025 CY - Siegburg, Germany DA - 11.02.2025 KW - LIBS KW - Hydrogen Measurements KW - Steel PY - 2025 AN - OPUS4-62561 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hübner, Martin A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Dittmann, Florian A1 - Varfolomeev, Igor T1 - Effect of weld design on fatigue strength of welded components using LTT filler materials N2 - Low transformation temperature (LTT) filler metals are an innovative approach to reduce tensile residual stress in weld seams and the surrounding heat affected zone (HAZ). The reduced tensile stress leads to an improvement in the fatigue strength of welded components. LTT filler metals are characterized by a reduced martensite start temperature (Ms), which is close to room temperature because of their chemical composition. This paper focuses on the hybrid use of LTT filler metals, where the LTT filler is applied as an additional layer to conventional welds on fatigue-critical spots. Conventional gas metal arc welded longitudinal stiffeners are used as specimens and at the face ends of the stiffeners, a second LTT layer was added with various weld modifications. These modifications were achieved by changing the welding parameters such as welding speed and offset to the first layer. These samples were used to analyze shape, dilution and resulting Ms, residual stress and fatigue strength. The dilution and dilatometer verified Ms did not change significant, although the surface of the 2nd LTT weld seam was varying clear with each modification. However, the weld modification had a significant effect on the residual stress state and the fatigue strength. The X-ray determined residual stress in the HAZ became lower when the weld toe of the LTT layer was further away from the stiffener. The Fatigue strength is clearly dependent on the residual stress state. The lower the residual stress at weld toe, the higher the fatigue strength. All samples with LTT weld exhibit significantly higher fatigue strength values than conventionally single and double-layer welded samples. The results show that on the one hand LTT filler metals increase the fatigue strength, and on the other hand the impact of LTT fillers materials is not restricted to the dilution and Ms, the shape of the weld seam must also be considered. T2 - IIW Intermediate Meeting CII CY - Trollhättan, Sweden DA - 10.03.2025 KW - LTT (Low Transformation Temperature) KW - Residual stress reduction KW - Fatigue strength KW - High-strength steels KW - Welding PY - 2025 AN - OPUS4-62708 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Griesche, Axel T1 - In situ Measurement of Hydrogen in Steel using Laser‑induced Breakdown Spectroscopy (LIBS) N2 - The ISO 3690 standard “Determination of hydrogen content in arc weld metal” requires a thermal activation of the diffusible hydrogen in a piece of weld metal for the subsequent ex situ concentration measurement by carrier gas hot extraction CGHE or thermal desorption spectroscopy (TCD). Laser-induced breakdown spectroscopy (LIBS) offers a time and spatially resolved, almost non-destructive, in situ measurement of hydrogen at surfaces without sample preparation. We measured hydrogen in steels, which were charged either electrochemically or by high-pressure hydrogen gas and compared the results. Further, the feasibility of quantitative hydrogen line scan measurements with LIBS was demonstrated by measuring hydrogen at water jet cut surfaces. The hydrogen concentrations measured with the help of LIBS were compared with CGHE measurements. It was observed that hydrogen can be reliably measured with LIBS for concentrations larger than 2 wt.-ppm. The maximum hydrogen concentration achieved using electrochemical charging was 85.1 ppm. The results show that LIBS is a promising technique for time- and spatially resolved measurements of hydrogen in steels. T2 - 2025 European Winter Conference on Plasma Spectrochemistry CY - Berlin, Germany DA - 02.03.2025 KW - Hydrogen measurement KW - LIBS KW - Spatial resolution KW - Temporal resolution PY - 2025 AN - OPUS4-62699 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Czeskleba, Denis T1 - Numerical simulation of hydrogen diffusion in thick-walled S690 SAW joints: the role of microstructure-dependent diffusion vs. welding heat input N2 - S690 steels are increasingly employed in modern steel construction, including building, plant, and mobile crane applications, due to their high strength and weldability. Submerged arc welding (SAW) is commonly used for these thick-walled structures but poses a risk of delayed hydrogen-assisted cold cracking (HACC). The influence of microstructure-dependent diffusion coefficients (DH) on hydrogen accumulation and distribution during welding and cooling remains poorly understood. In this study, the HACC susceptibility of thermomechanically rolled (MC) and quenched and tempered (Q) variants of S690 steel was compared. Weldments were fabricated using SAW, followed by electrochemical hydrogen permeation tests to determine microstructure-specific DH. A numerical model was developed to analyze hydrogen diffusion as a function of temperature, time, and microstructure. Results showed that the MC-grade exhibited slightly faster hydrogen diffusion than the Q-grade. However, simulations indicated that higher welding heat input and increased plate thickness had a significantly greater impact on hydrogen retention than microstructure-dependent diffusion effects. These findings suggest that while differences in hydrogen diffusivity exist between S690MC and S690Q, microstructure-specific diffusion plays a minor role in HACC risk. Instead, proper control of welding parameters is crucial for mitigating HACC, particularly in thick-plate, multi-layer SAW joints. T2 - Cracking Phenomena in Welding and Additive Manufacturing, 5th Int. Conference CY - Trollhätten, Sweden DA - 12.03.2025 KW - Hydrogen Cracking KW - Submerged Arc Welding KW - Hydrogen Diffusion KW - Cold Cracking PY - 2025 AN - OPUS4-63126 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erxleben, Kjell T1 - Component test for safety assessment of in-service welding on / onto pressurized hydrogen pipelines N2 - Hydrogen is the energy carrier of tomorrow for a fossil-free future. This requires a reliable transport infrastructure capable of transporting large quantities of hydrogen, e.g. for the steel and chemical industries. In addition to the construction of new pipelines, the conversion of existing natural gas (NG) networks is an essential part of global hydrogen strategies. The transport of hydrogen is fundamentally different from that of NG, as hydrogen can be absorbed into the pipeline material. Given the known effects of hydrogen embrittlement, the compatibility of the materials for the proposed pipelines (typically low alloy steels in a wide range of strengths and thicknesses) must be investigated. However, pipelines require frequent maintenance, repair, or the need to install additional outlets. In some cases, it is necessary to perform welding on or to the pipelines while they are still in service, i.e. with active gas flow under high pressure, such as the well-known "hot tapping". This in-service welding poses challenges for hydrogen operations in terms of additional hydrogen absorption during welding and material compatibility. The challenge can be roughly divided into the possible austenitization of the inner pipe material exposed to hydrogen, which can lead to sufficient hydrogen absorption, and the welding itself, which causes an increased temperature range. Both lead to a significant increase in hydrogen solubility and diffusivity of the respective materials compared to room temperature. In this context, knowledge about hot tapping on hydrogen pipelines is scarce due to the lack of operational experience. Fundamental experimental investigations are required to investigate the transferability from natural gas to hydrogen pipeline networks. For this reason, the present study presents a specially designed mock-up / demonstrator concept for the realistic assessment of the welding process conditions. T2 - Materials Week 2025 CY - Frankfurt am Main, Germany DA - 02.04.2025 KW - In-service KW - Hydrogen KW - Pipeline KW - Repair welding PY - 2025 AN - OPUS4-62874 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kaiser, Sebastian T1 - Evaluation of welding on in-service pressurized hydrogen pipelines by component testing N2 - Hydrogen transportation is fundamentally different from natural gas (NG) as it can be absorbed into the pipeline material. However, pipelines require frequent maintenance or repair, in some cases on or onto the pipelines while they are still under pressure. This in-service welding causes challenges for hydrogen operations. They can be roughly divided into: (1) possible austenitization of the inner pipe material exposed to hydrogen, and (2) welding itself with its temperature cycles. Both lead to a significant increase in hydrogen solubility/diffusivity of the materials. Fundamental investigations are required due to the missing service experience. The present study introduces a specially designed demonstrator concept for the assessment of the welding processing conditions. The mock-up was designed to enable temperature measurement during welding as well as ex-post extraction of samples for the quantification of the absorbed hydrogen. The necessary pressurized hydrogen volume was limited by the insertion of a solid cylinder. Welding experiments on the pressurized mock-ups (DN50 and DN200) have shown that the austenitization temperature is nearly reached on the inner surface of the pipeline. This corresponds to a significant hydrogen absorption of several ppm in the welded joint, especially for thin-walled pipelines. Nonetheless, a potential hydrogen assisted cracking was not identified. T2 - 24. Werkstofftechnisches Kolloquium CY - Chemnitz, Germany DA - 02.04.2025 KW - Pipeline KW - In-Service KW - Welding KW - Hydrogen PY - 2025 AN - OPUS4-62917 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Reichel, Levin A1 - Kromm, Arne A1 - Michael, Thomas A1 - Schroepfer, Dirk A1 - Kannengiesser, Thomas T1 - Modern welding processes for optimizing repair welding on high-strength offshore steels N2 - The successful energy transition in Germany will require offshore wind turbines with outputs >10 MW in the future, for which high-strength steels with a yield strength of up to 500 MPa and wall thicknesses up to 150 mm are increasingly being used. The repair of weld seams when detecting defects during NDT requires localized gouging and rewelding. This involves high demands on welding manufacturing, especially for highstrength steels. Due to a lack of investigations, there are no repair concepts and information in standards and guidelines, particularly for high-strength thick plate joints made of high-strength offshore steels. However, these are urgently needed to enable processors, especially SMEs, to carry out safe and economical repairs. Therefore, BAM startedthe FOSTA project P1629 (IGF 01IF22746N) to investigate the stress-optimized repair(local gouging and welding) of high-strength thick plate joints made of offshore grades in the yield strength range off 355 to 460 MPa and similar weld metal with controlled high-performance GMAW processes and optimized narrower gouging grooves. The experimental analyses consider the complex interaction of material, process, and designrelated influences on the formation of weld-related stresses and the special microstructure of high-strength fine-grain structural steels. Welding-related material Degradation and crack-critical residual tensile stresses need to be avoided to ensure high component safety and performance. With component-related welding experiments on special testing equipment, adapted process and heat control concepts along with variable groove configurations will be developed and recommendations for guidelines elaborated. This is the prerequisite for fully utilizing the strength potential of high-strength steels and making a valuable contribution to the energy transition in Germany, especially for steelprocessing SMEs. T2 - 6. Symposium Materialtechnik CY - Clausthal-Zellerfeld, Germany DA - 20.02.2025 KW - Narrow groove KW - Optimized repair welding KW - Modern welding processes KW - High-strength steel PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-636520 DO - https://doi.org/10.21268/20250507-5 SP - 3 EP - 15 AN - OPUS4-63652 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröder, Nina T1 - Challenges in the evaluation of the weldability of old mild steels for future use N2 - From the middle of the 19th century, the development and implementation of completely new manufacturing processes meant that molten steel could be produced in almost any quantity. This enabled the widespread use of the steels from this time, whose area of application was considerably expanded. Numerous structures built on this basis are still in operation today and represent an essential part of the infrastructure. For example, around 50 % of the bridges and engineering structures in the German railway network are over 80 years old, with around 80 % of these structures having existed for more than 100 years. Similarly, around 6,000 bridges in Germany's road network were built more than 80 years ago. Particularly, today high level of loads due to railway/road traffic (masses, speed etc.) intensifies the importance of maintaining and repairing these structures. The focus of these measures is to enable the structures to fulfil future requirements. As earlier constructions were predominantly designed for screws and rivet joints, old steels were originally manufactured without considering their suitability for welding. In addition, for historical steel structures there is often insufficient or no documentation available. This includes data on material specifications such as the chemical composition, information on the mechanical-technological properties and on the manufacturing process used. These missing information poses a major challenge for the assessment of the steels suitability for welding. Furthermore, old steels are characterised by a typical macrostructure. Depending on whether the manufacturing process is a cast steel process or ingot casting (currently continuous casting), the question arises as to the type of deoxidisation (non-/deoxidized). In the case of non-deoxidized old mild steels, a relatively clean, dense surface layer, the so-called ‘rim-layer’, forms during the solidification of the steel ingot. Towards the centre of the sheet cross-section however, the remaining molten metal becomes increasingly enriched with tramp elements such as sulphur and phosphorus. This so-called segregation layer makes fault-free welding significantly more difficult, as depending on the heat input, chemical composition and the filler metal used, hot cracking, the risk of brittle fracture and a tendency to terrace fracture can be expected. Thus, an individual assessment of the suitability for welding of each old steel charge used in such old structures, that must be repaired is necessary. T2 - 78th Annual Assembly and International Conference CY - Genoa, Italy DA - 22.06.2025 KW - Old mild Steels KW - Weld-CCT diagrams KW - Suitability for welding KW - Dilatometry KW - Repair measures PY - 2025 AN - OPUS4-63649 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Reichel, Levin T1 - From conventional to narrow groove repair: Optimizing repair welding with modern welding processes for high strength offshore steels N2 - The successful energy transition in Germany will require offshore wind turbines with outputs >10 MW in the future. To achieve these high outputs, turbines far from the coast are required, featuring large subsea jacket structures (30 m up to 50 m) and tall towers (up to 200 m). High-strength steels with a yield strength up to 500 MPa and wall thicknesses of up to 120 mm are increasingly being used for these structures. During manufacture, weld defects detected by non-destructive testing (NDT) require localized repair (gouging and rewelding). To date, there is a lack of repair concepts and information in standards and guidelines. Therefore, BAM initiated the FOSTA project P1629 (IGF 01IF22746N) to investigate the stress-optimized repair (local gouging and welding) of high-strength thick plate joints made of offshore grades in the yield strength range off 355 to 460 MPa and similar weld metal. This research aims to develop a stress-optimized repair concept for thick plate joints, using controlled high-performance GMAW processes and optimized, narrow gouging grooves. Thermal and mechanical gouging are performed, allowing the groove configuration to be modified. Modern welding processes provide deep root penetration and focused energy input capable of welding narrow seams. The aimed residual stress reduction can be attributed to the lower input of weld metal due to the changes in groove configuration and to the reduction in heat input per layer due to the controlled arc process. The experimental analyses take into account the interaction of process, material, and design-related influences on the formation of weld induced stresses. Concluding with recommendations for guidelines elaborated for steel-processing SMEs. T2 - 78th IIW Annual Assembly and International Conference CY - Genoa, Italy DA - 22.06.2025 KW - Narrow groove KW - Optimized repair welding KW - Modern welding processes PY - 2025 AN - OPUS4-63651 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröder, Nina T1 - Influence of various microalloying strategies on the mechanical properties of weld seams in S690QL steel N2 - Microalloying elements such as niobium (Nb) and titanium (Ti) play a crucial role in achieving the desired mechanical properties of quenched and tempered high-strength fine-grained structural steels with a nominal yield strength of ≥ 690 MPa. Current specifications for the chemical composition only define upper limits for these elements, providing manufacturers with some flexibility. However, even minor deviations in alloying concepts can significantly influence the resulting mechanical properties. Consequently, accurately predicting weldability and the integrity of welded joints becomes challenging or even unfeasible due to variations in composition and the associated microstructural changes. Potential adverse effects include the softening of the heat-affected zone (HAZ) or, conversely, localized hardening phenomena. To address these challenges, various microalloying strategies with different Ti and Nb contents are being systematically investigated for the first time using specially designed laboratory-cast alloys. Each alloying approach is based on the commonly used S690QL steel grade while maintaining consistent chemical composition and heat treatment parameters. T2 - 78th Annual Assembly and International Conference CY - Genoa, Italy DA - 22.06.2025 KW - HSLA KW - Digital Image Correlation KW - HAZ Softening KW - Impact Toughness KW - Microalloying influence PY - 2025 AN - OPUS4-63648 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Czeskleba, Denis T1 - Numerical simulation of hydrogen diffusion in submerged arc multilayer welds as a tool for the evaluation of cold cracking resistance N2 - High-strength structural steels are increasingly used in modern steel construction for economic and design reasons, e.g., in building, plant or mobile crane construction. By using steels with higher yield strengths (≥690 MPa), significant weight reductions and lower processing costs can be achieved by reducing the wall thickness. For example, substituting S235J2 with S960QL can reduce weight by up to 78%. Current efforts in lightweight design result from the goal of reducing greenhouse gas emissions by up to 65% by 2030 compared to 1990. These demands mean a significant reduction in process emissions in industry by increasing the efficiency of energy and raw materials. Submerged arc welding (SAW) offers high deposition rates and the welding of sheet thicknesses of up to 200 mm. Due to their special microstructure to achieve strength, high strength steels have reduced ductility and are susceptible to hydrogen-assisted cold cracking (HACC), which can also form with delay. In addition, large plate thicknesses lead to high residual welding stresses and long diffusion paths for hydrogen introduced via the welding process, for example. Numerical simulations provide a tool for evaluating the susceptibility of welded joints to cold cracking. In this study, the influence of heat input (ranging from 14.5 kJ/cm to 22 kJ/cm) and plate thickness (30 mm to 60 mm) on the hydrogen content in welded joints was investigated using the finite difference method. The simulation was parametrized to account for weld geometry, heat input and conduction, as well as hydrogen diffusion. Experimental investigations within the project determined hydrogen diffusion coefficients using electrochemical permeation. Additionally, the geometry of the weld layers was analyzed through macrosection examinations. These simulations showed that the heat input has a significant influence on the effusion of hydrogen and the distribution of the hydrogen concentration. Significant influencing factors are above all the sheet thickness and the thickness of the weld bead, as the hydrogen needs more time for effusion with longer diffusion paths. The simulation results can be used to derive HRHT diagrams and improve efficiency through process optimization. T2 - IIW Intermediate Meeting 2025 CY - Trollhätten, Sweden DA - 10.03.2025 KW - Hydrogen Cracking KW - Submerged Arc Welding KW - Hydrogen Diffusion KW - Cold Cracking PY - 2025 AN - OPUS4-63125 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yang, Chunliang A1 - Yang, Fan A1 - Meng, Xiangmeng A1 - Putra, Stephen Nugraha A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Multi-refining effects of an AC electromagnetic field on the microstructure in AA5754 laser beam welding N2 - Fine-grain structure is beneficial to the mechanical properties of the joint. Different kinds of grain and sub-grain structures refined by magnetic field during laser beam welding of AA5754 aluminum alloy are analyzed in this manuscript, and the influences of different magnetic field parameters (magnetic flux density and frequency) in these refining effects are also studied. Using the scanning electron microscope (SEM), the sub-grain structure near the fusion line was obtained, and it was found that the branching promotion and branches refinement can be achieved by the magnetic field. The branches become finer with the magnetic flux density or frequency increases, and this effect is stronger in the dendritic region than in the equiaxed region. The results of electron backscatter diffraction (EBSD) in the equiaxed region show that a high-frequency magnetic field can greatly reduce the average grain size, while a low-frequency one has little effect. A phenomenological nucleation model based on dendrite fragmentation theory was established, and it was introduced into the phase field model to analyze the equiaxed grains evolution process. In addition, another refinement mechanism was also observed. The periodic solidification pattern caused by the unstable solidification in the molten pool can refine the grains, and the magnetic field promotes this kind of grain refinement by promoting the solidification period. KW - Laser beam welding KW - Magnetic field KW - Aluminum alloy KW - Crystal branch development KW - Periodic solidification pattern KW - Grain refinement PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-637222 DO - https://doi.org/10.1016/j.ijheatmasstransfer.2025.127509 SN - 0017-9310 VL - 252 SP - 1 EP - 16 PB - Elsevier Ltd. AN - OPUS4-63722 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Biegler, Max A1 - Yang, Keke A1 - Meschut, Gerson A1 - Rethmeier, Michael T1 - Occurrence and avoidance of liquid metal embrittlement in resistance spot welding of springback-afflicted deep-drawn components N2 - This study investigates the occurrence and mitigation of liquid metal embrittlement occurring during resistance spot welding in deep-drawn automotive components, specifically focusing on an S-Rail made from advanced high-strength steel. A simulation-based liquid metal embrittlement risk criterion based on local major component stresses was established and used to quantify and compare liquid metal embrittlement risks between different tests. Experimental and numerical analyses were conducted, revealing that springback significantly impacts liquid metal embrittlement formation. Adjustments in electrode geometry and hold time post-welding were found to mitigate liquid metal embrittlement risks. The effects of stack-up configuration and related parameter settings on liquid metal embrittlement occurrence were identified and liquid metal embrittlement was effectively prevented across both stack-up configurations. These findings advance the understanding of liquid metal embrittlement mechanisms and provide practical approaches to enhance the spot weld quality in AHSS-based body-in-whites. KW - Liquid metal embrittlement KW - Crack KW - Advanced high-strength steels KW - Resistance spot welding KW - Weld current KW - Heat input KW - Simulation KW - Springback KW - Deep drawing KW - S-Rail PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-636577 DO - https://doi.org/10.1177/13621718251340452 SN - 1362-1718 SP - 1 EP - 9 PB - SAGE Publications AN - OPUS4-63657 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meng, Xiangmeng A1 - Putra, Stephen Nugraha A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - A statistical assessment of the laser energy absorption and keyhole stability in high-power laser welding N2 - The behavior of the molten pool and final weld qualities in high-power laser welding are significantly influenced by laser absorption and keyhole stability. However, the dynamic features involved make the in-depth analyses challenging. This study addresses the challenges by conducting a thorough statistical evaluation of the effects of key welding parameters on laser absorption and keyhole fluctuations, using experimental investigations and a robustly validated multi-physics model. From a statistical aspect, the laser energy distribution and the keyhole collapse, commonly considered to be highly time-varying, show certain regularities, for example, three distinct regions of the temporally averaged energy distribution and a universal normal distribution of the keyhole collapse positions. Further discussion is performed to clarify the greater potential of the statistical data in revealing some well-known, industry-related but unclearly explained findings, such as the saturation of the weld penetration with increasing heat input and the physical basis of the contributions of different welding parameters in the porosity reduction. KW - Laser welding KW - Laser absorption KW - Keyhole stability KW - Porosity defect KW - Multi-physics modeling PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-628367 DO - https://doi.org/10.1016/j.jmapro.2025.03.053 SN - 2212-4616 VL - 141 SP - 885 EP - 896 AN - OPUS4-62836 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller, Vinzenz A1 - Fasselt, Janek Maria A1 - Klötzer-Freese, Christian A1 - Kruse, Tobias A1 - Kleba-Ehrhardt, Rafael A1 - Biegler, Max A1 - Rethmeier, Michael T1 - Recycling nickel aluminium bronze grinding chips to feedstock for directed energy deposition via impact whirl milling: Investigation on processability, microstructure and mechanical properties N2 - During the production of ship propellers, considerable quantities of grinding chips from nickel aluminium bronze are produced. This paper examines the mechanical comminution of such chips via impact whirl milling and the utilization of two chip-powder batches as feedstock for a laser-based directed energy deposition process. The materials are characterized via digital image analysis, standardized flowability tests, scanning electron microscopy and energy dispersive X-ray spectroscopy and are compared to conventional, gas atomized powder. The specimens deposited via directed energy deposition are analyzed for density, hardness and microstructure and tensile properties for vertical and horizontal build up directions are compared. At elevated mill rotation speeds, the comminution with impact whirl milling produced rounded particles, favorable flow properties and particle size distribution, making them suitable to deposit additive specimens. The microstructure exhibited characteristic martensitic phases due to the high cooling rates of the additive manufacturing process. The presence of ceramic inclusions was observed in both the powder and on the tensile fracture surfaces, partly impairing the mechanical properties. However, specimens in the vertical build-up direction (Z) showed competitive tensile results, with 775 MPa in tensile strength, 455 MPa in yield strength and 12.6 % elongation at break. The findings of this study indicate that recycling of machining chips to additive manufacturing feedstock can be a viable option for reducing material costs and environmental impact. KW - Nickel aluminium bronze KW - Grinding chips KW - Recycling KW - Directed energy deposition KW - Material characterization PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-633442 DO - https://doi.org/10.1016/j.addma.2025.104804 SN - 2214-8604 VL - 105 SP - 1 EP - 9 PB - Elsevier BV AN - OPUS4-63344 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Marquardt, Raphael A1 - Biegler, Max A1 - Rethmeier, Michael T1 - Influence of laser power on the melt pool shape of handheld laser beam welding of 1.5 mm thick micro alloyed steel N2 - Manual welding of structures requires highly skilled welders due to the large heat-affected zone of arc-based processes, that can negatively impact microstructure and cause distortion. Handheld laser beam welding is a promising alternative with high welding velocity and a concentrated heat input. However, its current use in industry is limited to parts with aesthetic requirements, often made of high-alloyed steel. To extend the use of handheld laser beam welding to low-cost steels with good mechanical properties, this study investigates the influence of laser power on the melt pool shape for micro-alloyed steel with a thickness of 1.5 mm. Tested joint geometries are T-joints welded with filler wire as well as butt joints and overlap joints without filler wire, which are typically found in assemblies under mechanical load. Weld quality is assessed by weld porosity analysis. The results show that the handheld laser beam welding with filler wire produces T-joints with a very good external appearance, but with porosity between level C and D in the cross sections according to DIN EN ISO 13919-1. By increasing the laser power, a deep penetration of the T-joint zone can be achieved without increasing the actual throat thickness. For handheld laser beam welding of butt joints a full penetration weld of the highest quality class can be reached. Overlap joints can be welded with full or partial penetration depending on the laser power selected, with quality classes between B and C in terms of porosity. T2 - 20th Nordic Laser Materials Processing Conference CY - Kongens Lyngby, Denmark DA - 26.08.2025 KW - Hand held laser welding KW - Laser beam welding KW - Low alloyed steel KW - Process parameter PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-641671 DO - https://doi.org/10.1088/1757-899X/1332/1/012015 SN - 1757-899X VL - 1332 SP - 1 EP - 6 PB - Institute of Physics CY - London [u.a.] AN - OPUS4-64167 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Marquardt, Raphael T1 - Influence of laser power on the melt pool shape of handheld laser beam welding of 1.5 mm thick micro alloyed steel N2 - Manual welding of structures requires highly skilled welders due to the large heat-affected zone of arc-based processes, that can negatively impact microstructure and cause distortion. Handheld laser beam welding is a promising alternative with high welding velocity and a concentrated heat input. However, its current use in industry is limited to parts with aesthetic requirements, often made of high-alloyed steel. To extend the use of handheld laser beam welding to low-cost steels with good mechanical properties, this study investigates the influence of laser power on the melt pool shape for micro-alloyed steel with a thickness of 1.5 mm. Tested joint geometries are T-joints welded with filler wire as well as butt joints and overlap joints without filler wire, which are typically found in assemblies under mechanical load. Weld quality is assessed by weld porosity analysis. The results show that the handheld laser beam welding with filler wire produces T-joints with a very good external appearance, but with porosity between level C and D in the cross sections according to DIN EN ISO 13919-1. By increasing the laser power, a deep penetration of the T-joint zone can be achieved without increasing the actual throat thickness. For handheld laser beam welding of butt joints a full penetration weld of the highest quality class can be reached. Overlap joints can be welded with full or partial penetration depending on the laser power selected, with quality classes between B and C in terms of porosity. T2 - 20th Nordic Laser Materials Processing Conference CY - Kongens Lyngby, Denmark DA - 26.08.2025 KW - Hand held laser welding KW - Laser beam welding KW - Low alloyed steel KW - Process parameter PY - 2025 AN - OPUS4-64169 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Savitsky, Viktor A1 - Schmies, Lennart A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Comparative performance of DIC and optical flow algorithms for displacement and strain analysis in laser beam welding N2 - The measurement of strain and displacement in the context of the welding process represents a significant challenge. Optical methods, such as digital image correlation (DIC) or optical flow algorithms, have demonstrated their efficacy in robust and reliable data acquisition in harsh environments, including those encountered in welding processes. Concurrently, a trade-off between the accuracy of the measurement and the computational resources required for the associated calculations must be evaluated on a case-by-case basis. The application of filters to initial images represents a technique that serves to enhance the quality and accuracy of the strain and displacement prediction. In the present study, the estimated error of two algorithms, namely the Lucas-Kanade (LK) and the inverse compositional Gauss-Newton (IC-GN), is compared on the basis of both synthetic and real welding images. The displacement field is evaluated for different zones in the laser weld seam with varying contrast performance. Based on the aforementioned results, a strain calculation was conducted for both methods, which yielded comparable results for the LK and IC-GN algorithms. KW - Laser speckle KW - DIC KW - Optical flow KW - Error estimation KW - Strain measurement KW - Laser beam welding PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-625919 DO - https://doi.org/10.1016/j.optlaseng.2025.108870 SN - 1873-0302 VL - 187 SP - 1 EP - 15 PB - Elsevier Ltd. AN - OPUS4-62591 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bachmann, Marcel T1 - Numerical studies of keyhole dynamic behavior during the laser beam welding with an oscillating magnetic field N2 - The formation of keyhole induced porosity (Process porosity) during laser beam welding (LBW) is mainly associated with the dynamic keyhole behavior. Experimental studies have confirmed that the application of a magnetic field can effectively suppress process porosity. However, there is still no quantitative evidence supporting that this suppression mechanism involves a direct influence of the magnetic field on the keyhole dynamics. In this paper, a novel keyhole reconstruction algorithm is developed and incorporated into a three-dimensional transient multi-physics coupled numerical model to study the dynamic keyhole behavior under the influence of an oscillating magnetic field. This keyhole reconstruction algorithm accurately reproduces the 2D time-averaged keyhole shape, effectively capturing the keyhole tailing and the backward shift of its centroid on the keyhole top. The application of an oscillating magnetic field reduces the keyhole diameter and enhances its stability. The frequency of keyhole collapse is reduced under the influence of a magnetic field. Additionally, the occurrence of keyhole collapses with long duration is significantly reduced in the presence of a magnetic field. T2 - 78th IIW Annual Assembly and International Conference CY - Genua, Italy DA - 22.06.2025 KW - Laser beam welding KW - Magnetohydrodynamics KW - Porosity KW - Numerical simulation PY - 2025 AN - OPUS4-63645 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Jonathan T1 - High-resolution in-situ image analysis in laser powder bed fusion N2 - Visual images captured - in-situ - in laser powder bed fusion (PBF-LB/M) provide valuable insights into process dynamics. This poster presents methods for analyzing high-resolution images with a spatial resolution of 17 µm/pixel and a size of 9344 × 7000 pixels. In the context of identifying microstructural anomalies, the relationship between the contrast values derived from the grey-level co-occurrence matrix (GLCM) of post-exposure images and ex situ measurements of surface roughness, porosity, and melt pool depth is illustrated. Furthermore, a workflow to detect process anomalies in post recoating images using an edge device is presented. T2 - BAM Advisory Council Meeting CY - Berlin, Germany DA - 25.06.2025 KW - Additive manufacturing KW - High resolution camera KW - Image processing KW - In situ monitoring KW - Powder bed fusion PY - 2025 AN - OPUS4-63990 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Liepold, Philipp A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Semantic Segmentation for Hot Cracking N2 - The images in this dataset are light microscope images of the surfaces of modified Varestraint-Transvarestraint test samples. The training images show the surface of a tungsten inert gas weld with possible hot cracks. The dataset is intended for use in training crack segmentation networks. This database consists of images in .png format. The training images were taken in 24-bit, 3-color channels with an optical light microscope (Keyence). The corresponding mask images are 8-bit grayscale images, where 255-valued pixels (white) denote crack areas and 0-valued pixels (black) denote non-cracked areas. This dataset was created manually with the help of a self-written segmentation program based on OpenCV. I used it to train networks based on ViT, ConvNeXt, U-Net, and EfficientNet architectures. The images were taken at magnifications of 50x and 100x. The dataset is structured as follows: Wire → Magnification (50, 100) → Data (train, mask = label) → Numbered images (1, 2, 3, …) (There may be missing numbers. The reasons are: 1) I did not take images of all surfaces if they were not cracked, and 2) the 100x magnification images were taken at a later point, by which time some samples had already been prepared for further evaluation, so no images could be taken.) For every image number in train, there is an equivalent number in mask with the same image size (but a different channel size, since train is 3-channel color and mask is single-channel). There is no fixed image size (h × w). If you want to train a network, I recommend either rescaling or taking sub-images for both the training and mask sets, or using architectures that can handle varying input sizes. The research project " Evaluation of design-induced solidification cracks during welding of high-strength fine-grained structural steels" is funded by the Federal Ministry of Economics and Climate Protection as part of the "Industrial Collective Research" programme on the basis of a resolution of the German Bundestag. This project IGF 01IF21837N FE 1 / P 1516 from the Research Association for steel Application (FOSTA), Düsseldorf, is carried out at Bundesanstalt für Materialforschung und -prüfung. KW - CNN KW - Segmentation KW - Hot cracking KW - AI PY - 2025 DO - https://doi.org/10.5281/zenodo.16919144 PB - Zenodo CY - Geneva AN - OPUS4-64031 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tobias, Charlie A1 - Gehrenkemper, Lennart A1 - Bernstein, Thomas A1 - Schlau, Sven A1 - Simon, Fabian A1 - Röllig, Mathias A1 - Meermann, Björn A1 - von der Au, Marcus T1 - Development of a fully automated slurry sampling introduction system for GF-AAS and its application for the determination of cadmium in different matrices N2 - element analysis, offering high sensitivity and precision. However, its effectiveness is limited by sample preparation challenges for solid samples like soils and microplastics. Traditional methods include sample preparation, such as digestion, which is time-consuming and involves reagents, like acids, contributing to measurement uncertainty and higher carbon footprints. Slurry sampling allows direct analysis of suspensions, offering a more efficient alternative. However, maintaining suspension stability is challenging, requiring robust autosampler systems to streamline the process and enhance analytical performance. Results: We present a novel autosampler extension for slurry sample introduction into GF-AAS. This system ensures suspension stability with a stirring device and closed vessels to prevent evaporation and contamination, incorporating a cooling unit to reduce solvent and analyte losses. It installs and removes in minutes without additional connections. Validation with cadmium analysis in BAM-U110 (Soil) and BAM-H010 (ABS) showed high reliability. For BAM-U110 (Soil), we achieved recovery rates of 94 % ± 13 % in water suspension. The recovery rate for BAM-H010 (ABS) was 104 % ±11 % in acetonitrile suspension. These results demonstrate the system’s robustness, versatility, and accuracy for different matrices. Significance: The autosampler extension helps solve key problems in trace element analysis of solid samples, making the process faster and more accurate. It works well with complex materials, making it useful for areas like microplastic or nanoparticle analysis. This improvement also helps meet regulations for monitoring environ mental and polymer samples, offering a reliable and flexible tool for high-throughput analysis with fewer errors. KW - Slurry AAS KW - Soil KW - Cd PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-618531 DO - https://doi.org/10.1016/j.aca.2024.343460 SN - 0003-2670 VL - 1335 SP - 1 EP - 7 PB - Elsevier BV AN - OPUS4-61853 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Erxleben, Kjell A1 - Kaiser, Sebastian A1 - Rhode, Michael A1 - Kannengiesser, Thomas A1 - Kromm, Arne T1 - In-service and repair welding of pressurized hydrogen pipelines–a review on current challenges and strategies N2 - Hydrogen is the energy carrier for a sustainable future without fossil fuels. As this requires a reliable transportation infrastructure, the conversion of existing natural gas (NG) grids is an essential part of the worldwide individual national hydrogen strategies, in addition to newly erected pipelines. In view of the known effect of hydrogen embrittlement, the compatibility of the materials already in use (typically low-alloy steels in a wide range of strengths and thicknesses) must be investigated. Initial comprehensive studies on the hydrogen compatibility of pipeline materials indicate that these materials can be used to a certain extent. Nevertheless, the material compatibility for hydrogen service is currently of great importance. However, pipelines require frequent maintenance and repair work. In some cases, it is necessary to carry out welding work on pipelines while they are under pressure, e.g., the well-known tapping of NG grids. This in-service welding brings additional challenges for hydrogen operations in terms of additional hydrogen absorption during welding and material compatibility. The challenge can be roughly divided into two parts: (1) the possible austenitization of the inner piping material exposed to hydrogen, which can lead to additional hydrogen absorption, and (2) the welding itself causes an increased temperature range. Both lead to a significantly increased hydrogen solubility in the respective materials compared to room temperature. In that connection, the knowledge on hot tapping on hydrogen pipelines is rare so far due to the missing service experiences. Fundamental experimental investigations are required to investigate the possible transferability of the state-of-the-art concepts from NG to hydrogen pipeline grids. This is necessary to ensure that no critical material degradation occurs due to the potentially increased hydrogen uptake. For this reason, the paper introduces the state of the art in pipeline hot tapping, encompassing current research projects and their individual solution strategies for the problems that may arise for future hydrogen service. Methods of material testing, their limitations, and possible solutions will be presented and discussed. KW - In-service KW - Hydrogen KW - Repair welding KW - Pipeline PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-638944 DO - https://doi.org/10.1007/s40194-025-02127-x SN - 0043-2288 SP - 1 EP - 24 PB - Springer Science and Business Media LLC AN - OPUS4-63894 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Thermal desorption spectroscopy for identification of diffusion and trapping in CoCrFeMnNi high-entropy alloy at 1,000 bar high-pressure hydrogen N2 - First studies on the mechanical behavior of high-entropy alloys (HEAs) in high-pressure hydrogen environment are available. In contrast, the underlying hydrogen absorption, diffusion and trapping in these HEAs like the Cantor-alloy was less in the scientific scope so far. For that reason, the CoCrFeMnNi-HEA was compared to a conventional AISI 316L austenitic steel, by exposing to high-pressure hydrogen charging at 200 bar and very-high pressure at 1,000 bar. Thermal desorption analysis (TDA) was applied with different heating rates (0.125 K/s to 0.500 K/s). The underlying TDA spectra were analyzed in terms of a reasonable peak deconvolution to into a defined number of peaks and the calculation of the activation energies for the respective and predominant hydrogen trap sites. Both materials show a comparable hydrogen diffusivity. The obtained activation energies suggest that in case of the CoCrFeMnNi-HEAs an interaction of the austenitic phase as well as the direct atomic bonding of hydrogen to the metal atoms are the dominant traps, since “impurities” such as carbides or inclusions are only present in trace amounts. Available literature suggests that the Cr and Mn-content is here of special interest for the direct hydrogen bonding at solute atoms. Despite the activation energy, the trap occupancy rate must be considered in terms of a pressure-related hydrogen absorption. The derived apparent hydrogen solubility was in the order: 316L < CoCrFeMnNi-HEA for both charging pressures. Especially, the 1,000 bar values lead to noteworthy results with > 70 wt.ppm for the AISI 316L and >130 wt.ppm for the CoCrFeMnNi. In fact, both the hydrogen diffusion and trapping data on gaseous high-pressure hydrogen charged HEAs are rare so far. The results of the present study allow a deeper understanding of hydrogen trapping in the regarded CoCrFeMnNi-system. T2 - 1st Conference on Hydrogen in Materials Science and Engineering (H2-MSE) CY - Freiburg, Germany DA - 11.02.2025 KW - High-entropy alloy KW - Hydrogen diffusion KW - High-pressure charging KW - Thermal desorption analysis PY - 2025 AN - OPUS4-62543 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Jonathan A1 - Merz, Benjamin A1 - Poka, Konstantin A1 - Mohr, Gunther A1 - Hilgenberg, Kai T1 - Surface structure analysis using visual high-resolution in situ process monitoring in laser powder bed fusion N2 - Parameter studies are a common step in selecting process parameters for laser powder bed fusion of metals (PBF-LB/M). Density cubes are commonly used for this purpose. Density cubes manufactured with varied process parameters can exhibit distinguishable surface structures visible to the human eye. The layer-wise process enables such surface structures to be detected during manufacturing. However, industrial visual in situ monitoring systems for PBF-LB/M currently have limited resolution and are incapable of reliably capturing small differences in the surface structures. In this work, a 65 MPixel high-resolution monochrome camera was integrated into an industrial PBF-LB/M machine together with a high-intensity LED (light-emitting diode) bar. Post-exposure images were taken to analyse differences in light reflection of fused areas. It is revealed that the grey-level co-occurrence matrix can be used to quantify the visual surface structure of nickel-based superalloy Inconel®939 density cubes per layer. The properties of the grey-level co-occurrence matrix correlate to the energy input and the resulting porosity of density cubes. Low-energy samples containing lack of fusion flaws show an increased contrast in the grey-level co-occurrence matrix compared to specimens with optimal energy input. The potential of high-resolution images for quality assurance via in situ process monitoring in PBF-LB/M is further discussed. KW - Additive manufacturing KW - Powder bed fusion KW - In situ monitoring KW - Image processing KW - High resolution camera PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-626685 DO - https://doi.org/10.1007/s40194-025-01955-1 SN - 1878-6669 SP - 1 EP - 15 PB - Springer Science and Business Media LLC AN - OPUS4-62668 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erxleben, Kjell A1 - Kaiser, Sebastian A1 - Rhode, Michael A1 - Kannengießer, Thomas A1 - Hadick, C. A1 - Schu, K. T1 - Quantification of hydrogen uptake during in-service hydrogen pipeline welding N2 - Hydrogen must be transported on a large scale from producers to consumers to ensure the energy transition. The necessary pipeline grid is achieved by conversion of the natural gas (NG) grid and building new pipelines. Welding during service as part e.g. of “hot-tapping” is unavoidable for maintenance/repair/expansion. Based on existing studies, the basic material compatibility of (low-alloyed) pipeline steels with hydrogen is postulated. However, this cannot be assumed for the case of in-service welding on pipelines in pressurized condition. The reason is the increased temperature e.g. by preheating and (in particular) during welding of the single passes. As a result, the inner pipeline surface undergoes multiple short-term heating but to high temperatures. In particular, the first passes can result in a temperature close to the austenitic transformation of the material for small wall thicknesses. Both increase the hydrogen uptake into the welded joint. If hydrogen embrittlement is likely to occur, depends on the hydrogen uptake, which must be quantified. For this purpose, welding experiments on pressurized demonstrators were conducted. The hydrogen uptake at 100 bar was compared to reference experiments with nitrogen. A new sample extraction routine for the quantification of the weld-zone specific hydrogen uptake was established. Comprehensive experiments with different steels (P235, L360, L485), wall thicknesses (4.1 mm to 7.8 mm) and diameters (DN50 and DN200) were conducted. In addition, the influence of the welding layer sequence on the hydrogen uptake between single- and multi-layer welds was investigated. Analytical approaches were used to approximate the hydrogen uptake in the respective weld zones. The main findings were that the layer sequence and especially the wall thickness have a large influence on the hydrogen uptake. T2 - 20th Pipeline Technology Conference ptc2025 CY - Berlin, Germany DA - 06.05.2025 KW - In-service KW - Hydrogen KW - Pipeline KW - Repair welding KW - component test PY - 2025 SP - 1 EP - 12 AN - OPUS4-63166 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Hydrogen diffusion in thick-walled S690 SAW joints: Part 1 - Experimental determination of microstructure dependent diffusion coefficients N2 - S690 steels are widely used in heavy-duty applications, such as structural components, mobile cranes, and industrial plant construction, owing to their high strength and weldability. However, thick-plate submerged arc welding (SAW) can introduce elevated hydrogen levels and residual stresses that promote time-delayed hydro-gen-assisted cold cracking (HACC). Accurate, microstructure-specific diffusion data are scarce, limiting pre-dictive HACC assessments. This study presents an experimental determination of hydrogen diffusion coeffi-cients (DH) in two S690 variants: thermomechanically rolled (S690MC) and quenched and tempered (S690Q). Multi-layer SAW welds were produced from 30 mm-thick plate material at three heat input levels, and diffusion membranes were extracted from weld metal (WM), heat-affected zone (HAZ), and base material (BM). Hydro-gen permeation tests, conducted in accordance with DIN EN ISO 17081, yielded time-normalized flux curves from which DH was derived using the inflection-point method. At room temperature, DH values ranged from 6 × 10⁻⁵ to 9 × 10⁻⁵ mm²/s across all regions and heat inputs, with no significant difference between S690MC and S690Q. Weld metal exhibited marginally lower DH, attributed to enhanced hydrogen trapping, while base mate-rial measurements showed greater variability. These microstructure-resolved diffusion coefficients fill a critical data gap and provide essential input for the numerical simulations presented in Part 2. The results also support practical guidelines for mitigating HACC risk through the optimization of welding parameters. T2 - 78th IIW Annual Assembly, Meeting of Commission II-C CY - Genoa, Italy DA - 22.06.2025 KW - Hydrogen assisted cracking KW - Submerged arc welding KW - High strength steels KW - Hydrogen Diffusion KW - Electrochemical permeation PY - 2025 AN - OPUS4-63540 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Weld heat input effect on microstructure and hydrogen diffusion in thick-walled S690 submerged arc welded joints N2 - High-strength, low-alloy (HLSA) steels such as S690 are an attractive option for heavy industries such as offshore wind turbines and peripheral equipment due to their combination of excellent mechanical properties and weldability. The construction of these thick-walled structures requires highly efficient welding processes such as submerged arc welding (SAW). However, SAW faces challenges related to delayed hydrogen assisted cold cracking (HACC). Despite its importance, the effect of different diffusion coefficients on the cold cracking susceptibility of different microstructures within SAW-welded S690 steels is not fully understood. For this reason, the present study focuses on comparing the cold cracking susceptibility of thermomechanically rolled (TM) or quenched and tempered (QL) variants of S690 steel. Submerged arc welding was performed on both steel grades at different welding heat inputs. From these thick-walled welds, metallic membranes were extracted from the weld metal, the heat-affected zone (HAZ), and the two base metals. The specimens were subjected to electrochemical hydrogen permeation tests (according to ISO 17081) to determine the microstructure-specific hydrogen diffusion coefficients. In general, increased welding heat input and thickness decreased the hydrogen diffusion coefficients, i.e., the time required for hydrogen diffusion increased. In addition, the results showed that the TM grade exhibited slightly accelerated hydrogen diffusion coefficients compared to the QL grade, which is beneficial for hydrogen reduction and increases the HACC resistance. As a result, the microstructure-specific assessment of hydrogen diffusion in the BM, HAZ or WM of the SAW joint was less important for a given set of welding parameters compared to other welding processes such as gas metal arc welding (GMAW). The reason is that in multilayer SAW, the relatively large welding heat input and multiple annealing resulted in similar microstructures, resulting in very close hydrogen diffusion coefficients. From this point of view, it is sufficient to characterize the hydrogen diffusion coefficients of both the weld metal and the base material. T2 - 78th IIW Annual Assembly and International Conference CY - Genoa, Italy DA - 26.06.2025 KW - Hydrogen assisted cracking KW - Submerged arc welding KW - Diffusion KW - Electrochemical permeation KW - Microstructure PY - 2025 AN - OPUS4-63543 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Hydrogen diffusion in thick-walled S690 SAW joints: Part 2 - Predictive modeling of welding heat input and microstructure influence N2 - High-strength low-alloy (HSLA) steels such as S690 are widely employed in thick-walled welded structures, where hydrogen-assisted cold cracking (HACC) remains a persistent concern. While microstructure-specific hydrogen diffusion coefficients (DH) for weld metal (WM), heat-affected zone (HAZ), and base material (BM) were experimentally established in Part 1 of this study, their quantitative influence on hydrogen accumulation and effusion has not yet been fully clarified. This work presents a transient, spatially resolved numerical model for simulating hydrogen transport in multi-pass submerged arc welds. The model integrates experimentally determined DH values with realistic thermal cycles and temperature-dependent boundary conditions. Developed in Python, the simulation tool is purpose-built for hydrogen diffusion in welded joints and offers a focused, transparent alternative to general-purpose finite element platforms. Parametric analyses demonstrate that, although the diffusion coefficients vary by up to 50 %, their impact on overall hydrogen retention is minor. In contrast, welding parameters such as plate thickness, bead geometry, cooling time (t₈/₅), and interpass tem-perature exert a dominant influence on hydrogen distribution. Despite clear microstructural differences between the thermomechanically rolled (S690MC) and quenched and tempered (S690Q) variants, including hardness softening versus hardening in the heat-affected zone of the (pen)ultimate weld bead, the simulations confirm that their diffusion behavior and hydrogen solubility are closely aligned. Consequently, differences in diffusivity and solubility exert only a minor influence on hydrogen retention compared to thermal exposure and joint geometry. These findings support the interchangeable use of both steel grades in terms of HACC risk due to hydrogen diffusion kinetics, under comparable welding conditions. T2 - 78th IIW Annual Assembly, Meeting of Commission II-C CY - Genoa, Italy DA - 22.06.2025 KW - Hydrogen assisted cracking KW - Numerical simulation KW - Hydrogen diffusion PY - 2025 AN - OPUS4-63541 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rhode, Michael A1 - Czeskleba, Denis A1 - Fleißner-Rieger, H. A1 - Nietzke, Jonathan A1 - Kannengießer, Thomas T1 - Combined heating rate and restraint condition effect on stress relief cracking during PWHT of thick-walled Cr–Mo-V steel SAW joints N2 - Creep-resistant steels such as 13CrMoV9-10 are utilized in the manufacture of thick-walled pressure vessels and are typically joined by submerged arc welding (SAW). However, these materials are susceptible to stress relief cracking (SRC) if the required post weld heat treatment (PWHT) is not applied correctly. Existing PWHT guidelines, encompassing heating rate and dwell (or holding) time at a given temperature, are derived from a synthesis of empirical knowledge and typically free-shrinkage weld experiments to assess the susceptibility to SRC. Therefore, this study discusses the combined effect of the PWHT heating rate under free-shrinkage compared to restrained shrinkage. Welding experiments were conducted (using plates with a thickness of 25 mm) for both shrinkage conditions for a variety of heating rates and maximum temperatures. In-situ acoustic emission analysis was used to locate propagating SRCs during PWHT. Hardness measurements, mechanical property characterization (Charpy impact strength), and microstructure correlation were used to evaluate the SRC susceptibility. The results suggested that the influence of heating rate could not be directly related to SRC formation and that the initial weld microstructure prior to PWHT was more relevant in terms of very high hardness in the coarse grain heat affected zone, especially that of the last beads in the top layer of the welding sequence. This was seen in the form of random, unexpected SRC occurrence in only one specimen at a heating rate commonly used in welding practice (approximately 100 K/h). In this context, the additional effect of an external shrinkage restraint on SRC must be considered in the form of increasing mechanical loads during welding, which are typically not within the scope of welding practice. To mitigate the probability of SRC during PWHT, it is imperative to reduce the welding heat input and to restrict the structural shrinkage restraint of the weld joint. KW - Component test KW - Stress relief cracking KW - PWHT KW - Creep-resistant steel PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-631439 DO - https://doi.org/10.1007/s40194-025-02062-x SN - 1878-6669 SP - 1 EP - 17 PB - Springer Nature AN - OPUS4-63143 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Liepold, Philipp A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Investigation of restraint intensity influence on solidification cracking of high-strength filler materials in fillet welds via CTS testing N2 - In addition to chemical composition, metallurgy, and welding parameters, the intensity of restraint is one of the key variables influencing solidification cracking (SC). Due to their high strength-to-density ratio, many modern lightweight steel constructions increasingly rely on high-strength steel. Given the theoretical framework of solidification cracking theory, tests tend to focus on the effects of strain rate. Externally restrained tests have provided valuable insights into solidification crack susceptibility. In practice, most welded structures are self-restrained; therefore, self-restraint tests more accurately reflect real-world applications. By varying the plate thickness in controlled thermal severity (CTS) tests conducted on S1100 QL, it was possible to adjust the intensity of restraint on fillet welds at a high level. Testing was performed using four different filler wires for gas metal arc welding (GMAW), including three solid wires and one metal-cored wire. Additionally, two sets of welding parameters were evaluated. High arc energy (U × I/welding speed) and increased welding speed were found to be more prone to solidification cracking compared to the parameter set with lower arc energy and welding speed. The results indicate a correlation between increasing restraint severity and a higher incidence of solidification cracking. KW - CTS KW - Controlled thermal severity KW - High-strength steel KW - GMAW KW - Restraint PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-631315 UR - 1878-6669 DO - https://doi.org/10.1007/s40194-025-02046-x SP - 1 EP - 13 PB - Springer AN - OPUS4-63131 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hübner, Martin A1 - Dittmann, Florian A1 - Kromm, Arne A1 - Varfolomeev, Igor A1 - Kannengießer, Thomas T1 - Residual stress reduction using a low transformation temperature welding consumable with focus on the weld geometry N2 - Low transformation temperature (LTT) welding consumables represent an innovative approach to realize compressive residual stress in the weld seam and HAZ. LTT welding consumables use the volume-expanding martensitic phase transformation near room temperature to generate compressive residual stress during cooling. This article focuses on the weld geometry and its influence on residual stress reduction using an LTT welding consumable. For this purpose, layers with an LTT welding consumable were additionally applied to the front sides of conventionally welded longitudinal stiffeners. Different weld geometries of the second weld seam could be realized by varying the welding parameters. These samples were analyzed for geometric parameters, chemical composition, and residual stress. While the chemical composition and martensite start temperature (MS) were only slightly influenced by parameter changes, a clear influence with regard to residual stress and weld geometry was observed. Depending on the shape of the second LTT weld seam, residual stress reductions of 200 to 500 MPa were achieved using the same LTT welding consumable. T2 - IIW Annual Assembly and International Conference CY - Rhodes Island, Dodecanisa, Greece DA - 07.07.2024 KW - Low transformation temperature (LTT) KW - Martensite start temperature KW - Dilution KW - Weld geometry KW - Residual stress PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-633707 DO - https://doi.org/10.1007/s40194-025-02094-3 SN - 1878-6669 SP - 1 EP - 11 PB - Springer Nature CY - Berlin ; Heidelberg AN - OPUS4-63370 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Engelking, Lorenz A1 - Scharf-Wildenhain, R. A1 - Schröpfer, Dirk A1 - Hälsig, A. A1 - Kannengießer, Thomas A1 - Hensel, J. T1 - Influence of heat input on properties and residual stresses in hybrid addi-tive manufacturing of high strength steels using MSG processes N2 - The application of steels with a higher yield strength allows reductions in wall thickness, component weight and production costs. Hybrid additive manufacturing based on Gas Metal Arc Welding (GMAW) processes (DED-Arc) can be used to realise highly effi-cient component modifications and repairs on semi-finished products and additively manufactured structures. There are still a number of key issues preventing widespread implementation, particularly for SMEs. In addition to the manufacturing design, detailed information about assembly strategy and geometric adaptation of the component for modifications or repairs are missing. These include the welding-related stresses associ-ated with the microstructural influences caused by the additive manufacturing steps, particularly in the transition area of the substrate and filler material interface. The pre-sent research focuses the effect of welding heat control during DED-Arc process on the residual stresses, especially in the transition area. Defined specimens were welded fully automatically with a high-strength solid wire (yield strength > 790 MPa) especially adapted for DED-Arc on S690QL substrate. The working temperature and heat input were systematically varied for a statistical effect analysis on the residual stress state of the hybrid manufactured components. Regarding heat control, t8/5 cooling times within the recommended processing range (approx. 5 s to 20 s) were complied. The investiga-tion revealed a significant influence of the working temperature Ti on the compressive residual stresses in the transition area and the tensile residual stresses at the base of the substrate. High working temperatures result in lower compressive residual stresses, heat input E does not significantly affect the tensile stresses. T2 - 6. Symposium Materialtechnik CY - Clausthal-Zellerfeld, Germany DA - 20.02.2025 KW - DED-Arc KW - Residual stress KW - Heat control PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-632188 DO - https://doi.org/10.21268/20250506-3 SP - 110 EP - 122 AN - OPUS4-63218 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erxleben, Kjell T1 - Component test to simulate critical conditions of hydrogen assisted cracking in submerged arc welded offshore steel N2 - Offshore Wind Turbines (OWT) are a key factor in tomorrow's sustainable energy generation. The ever� increasing installation depth and weight of OWTs require suitable foundation concepts such as monopiles or tripods. Typically, mild steels such as S420ML are used with plate thicknesses of up to several hundred mm, resulting in high restraints in the welded joints. The large plate thickness requires high-efficiency welding processes such as submerged arc welding (SAW) with multiple wires. Due to the very high stiffness and plate thickness of the large-scale offshore structure, a susceptibility to time� delayed hydrogen assisted cracking (HAC) may occur. For this reason, a minimum waiting time (MWT) of up to 48 h must be considered before NDT is conducted. The evaluation of the crack susceptibility is complex due to the component size and stiffness of real offshore structures. For this purpose, a near-component test geometry has been developed to transfer the real stiffness conditions to laboratory (i.e. workshop) scale. The 350 kg mock-up consisted of heavy plates (thickness 50 mm, seam length 1,000 m) joined by a 22-pass submerged-arc weld. Additional stiffeners simulated the effect of high restraint or shrinkage restraint of the weld. Extreme scenarios of hydrogen absorption during welding were simulated by using flux in dry (HD < 5 ml/100g Fe) and wet (HD > 15 ml/100g Fe) conditions. Weld residual stresses were determined using a robotic X-ray diffractometer. Areas of critical tensile residual stress (at the yield strength level) were found in the weld metal and in the heat affected zone, suggesting that these weld subzones are the most critical in the case of hydrogen ingress. To identify possible delayed cracking, the welds were inspected by phased array ultrasonic testing (PAUT) after welding, 6 h, 12 h, 24 h, and a maximum of 48 h. Summarized, no significant occurrence of HAC was detected, indicating the high crack resistance of the welded joint, i.e., a suitable combination of base material, welding consumable and parameters. T2 - Materials Week/Steel Innovation CY - Frankfurt am Main, Germany DA - 02.04.2025 KW - Cold cracking KW - Component test KW - Hydrogen KW - Minimum waiting time KW - Offshore steel grade PY - 2025 AN - OPUS4-62873 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Characterization of hydrogen trapping in a CoCrFeMnNi high-entropy alloy charged up to 1000 bar high-pressure hydrogen N2 - First studies on the mechanical behavior of high-entropy alloys (HEAs) in high-pressure hydrogen environment are available. In contrast, the underlying hydrogen absorption, diffusion and trapping in these HEAs like the Cantor-alloy was less in the scientific scope so far. For that reason, the CoCrFeMnNi-HEA was compared to a conventional AISI 316L austenitic steel, by exposing to high-pressure hydrogen charging at 200 bar and very-high pressure at 1,000 bar. Thermal desorption analysis (TDA) was applied with different heating rates (0.125 K/s to 0.500 K/s), see Fig. 1a to d. The underlying TDA spectra were analyzed in terms of a reasonable peak deconvolution to into a defined number of peaks and the calculation of the activation energies for the respective and predominant hydrogen trap sites. Both materials show a comparable hydrogen diffusivity. The obtained activation energies suggest that in case of the CoCrFeMnNi-HEAs an interaction of the austenitic phase as well as the direct atomic bonding of hydrogen to the metal atoms are the dominant traps, since “impurities” such as carbides or inclusions are only present in trace amounts. Available literature suggests that the Cr and Mn-content is here of special interest for the direct hydrogen bonding at solute atoms. In addition, the trap occupancy rate must be considered in terms of a pressure-related hydrogen absorption. The derived apparent hydrogen solubility was in the order: 316L < CoCrFeMnNi-HEA for both charging pressures. Especially, the 1,000 bar values lead to noteworthy results with > 70 wt.ppm for the AISI 316L and >130 wt.ppm for the CoCrFeMnNi. In fact, both the hydrogen diffusion and trapping data on gaseous high-pressure hydrogen charged HEAs are rare so far. The results of the present study allow a deeper understanding of hydrogen trapping in the regarded CoCrFeMnNi-system. T2 - 78th IIW Annual Assembly and International Conference CY - Genoa, Italy DA - 26.06.2025 KW - Hydrogen KW - Thermal desorption analysis KW - High-pressure charging KW - Trapping KW - Diffusion PY - 2025 AN - OPUS4-63542 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Rhode, Michael A1 - Mente, Tobias A1 - Kannengießer, Thomas A1 - Czeskleba, Denis T1 - Simulation of hydrogen distribution in submerged arc welded heavy plates as tool for evaluating cold cracking sensitivity for offshore structures N2 - Foundation structures for offshore wind turbines are typically made of heavy plate struc-tural steels, such as S420ML, welded by submerged arc welding. Due to the welding process conditions, higher amounts of hydrogen can be introduced. In this context, large plate thicknesses result in long diffusion paths and a prolonged diffusion time for hydrogen at ambient temperature and possible delayed hydrogen-assisted cold cracking. As a result, hydrogen can accumulate in areas of high mechanical stress and strain. Due to the delayed diffusion, a minimum waiting time of up to 48 h must be observed before non-destructive testing can be performed. In addition, the assessment of possible cold crack locations is very complex. For this reason, a numerical model of a component-like weld test was developed to simulate the temperature field during welding and subsequent cooling. A hydrogen diffusion model based on the temporal-local temperature distribution was established. It was applied to simulate the change of hydrogen distribution as a function of temperature cycle during multi-layer welding and further for the entire waiting time interval ≤ 48 h. As a result, crack critical areas could be evaluated in terms of accu-mulated hydrogen. An advantage of the diffusion model is the simulation of a normalized concentration, i.e. between "0" (no hydrogen) and "1" (max. concentration), which can be scaled to experimentally determined hydrogen concentrations. Finally, selected results for increased real hydrogen ingress are presented, which confirm the relatively high crack resistance of the S420 submerged arc welded joint. KW - Hydrogen assisted cracking KW - Diffusion KW - Numerical simulation KW - Offshore steel PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-632416 DO - https://doi.org/10.21268/20250507-6 SP - 1 EP - 12 PB - Technische Universität Clausthal CY - Clausthal-Zellerfeld, Deutschland AN - OPUS4-63241 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erxleben, Kjell A1 - Kaiser, Sebastian A1 - Rhode, Michael A1 - Kannengießer, Thomas A1 - Hadick, C. A1 - Schu, K. T1 - Component test concept for evaluation of in-service welding on pressurized hydrogen pipelines N2 - Hydrogen is set as the energy carrier of tomorrow and most countries will achieve large-scale hydrogen transport through the conversion of the natural gas (NG) grid and the construction of new pipelines. The interaction between hydrogen and the pipeline materials differs fundamentally from that of NG, as hydrogen is readily absorbed into the material. Considering the possible hydrogen embrittlement (HE), the compatibility of the pipeline materials (low-alloyed steels with a wide strength/thickness range) must be investigated. However, pipelines require intervention for maintenance, repair, or grid expansion with welding on/onto the pipelines while in service, i.e. the well-known "hot tapping" and "plugging" or “stoppling”. The challenges compared to NG can be broadly divided into the possible austenitization of the inner pipe material exposed to hydrogen and the welding itself. Both result in a significant increase in hydrogen solubility and could potentially pose challenges in terms of HE. Emphasis is placed on the word "could" because knowledge of "hot tapping" on hydrogen pipelines is scarce due a lack of service experience. To this end, this study proposes a concept for a component-like demonstrator with the objectives: (1) safe feasibility of "hot tapping" on pressurized model hydrogen pipeline sections, (2) facilitate ex-post sample extraction for the purpose of quantifying the absorbed hydrogen concentrations, and (3) ensure in-situ temperature measurement during welding to monitor the pipeline surface temperature. For safety reasons in the event of an unintentional "burn-through", a solid cylinder was inserted in the demonstrator to restrict the hydrogen gas volume to a small, pressurized layer. Reference pipeline surface temperature measurements were ensured on comparable, unpressurized geometries. The investigated range of welding conditions was investigated for representative material/thickness combinations (DN50 to DN200), suggesting the feasibility of the demonstrator for the determination of reliable in-service welding conditions for both installed and new pipelines for hydrogen service. T2 - 20th Pipeline Technology Conference ptc2025 CY - Berlin, Germany DA - 06.05.2025 KW - In-service KW - Hydrogen KW - Pipeline KW - Repair welding KW - component test PY - 2025 SP - 1 EP - 11 AN - OPUS4-63168 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erxleben, Kjell T1 - Component test concept for evaluation of in-service welding on pressurized hydrogen pipelines N2 - Hydrogen is set as the energy carrier of tomorrow and most countries will achieve large-scale hydrogen transport through the conversion of the natural gas (NG) grid and the construction of new pipelines. The interaction between hydrogen and the pipeline materials differs fundamentally from that of NG, as hydrogen is readily absorbed into the material. Considering the possible hydrogen embrittlement (HE), the compatibility of the pipeline materials (low-alloyed steels with a wide strength/thickness range) must be investigated. However, pipelines require intervention for maintenance, repair, or grid expansion with welding on/onto the pipelines while in service, i.e. the well-known "hot tapping" and "plugging" or “stoppling”. The challenges compared to NG can be broadly divided into the possible austenitization of the inner pipe material exposed to hydrogen and the welding itself. Both result in a significant increase in hydrogen solubility and could potentially pose challenges in terms of HE. Emphasis is placed on the word "could" because knowledge of "hot tapping" on hydrogen pipelines is scarce due a lack of service experience. To this end, this study proposes a concept for a component-like demonstrator with the objectives: (1) safe feasibility of "hot tapping" on pressurized model hydrogen pipeline sections, (2) facilitate ex-post sample extraction for the purpose of quantifying the absorbed hydrogen concentrations, and (3) ensure in-situ temperature measurement during welding to monitor the pipeline surface temperature. For safety reasons in the event of an unintentional "burn-through", a solid cylinder was inserted in the demonstrator to restrict the hydrogen gas volume to a small, pressurized layer. Reference pipeline surface temperature measurements were ensured on comparable, unpressurized geometries. The investigated range of welding conditions was investigated for representative material/thickness combinations (DN50 to DN200), suggesting the feasibility of the demonstrator for the determination of reliable in-service welding conditions for both installed and new pipelines for hydrogen service. T2 - 20th Pipeline Technology Conference ptc2025 CY - Berlin, Germany DA - 06.05.2025 KW - In-service KW - Hydrogen KW - Pipeline KW - Repair welding KW - Component test PY - 2025 AN - OPUS4-63170 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erxleben, Kjell T1 - Quantification of hydrogen uptake during in-service hydrogen pipeline welding N2 - Hydrogen must be transported on a large scale from producers to consumers to ensure the energy transition. The necessary pipeline grid is achieved by conversion of the natural gas (NG) grid and building new pipelines. Welding during service as part e.g. of “hot-tapping” is unavoidable for maintenance/repair/expansion. Based on existing studies, the basic material compatibility of (low-alloyed) pipeline steels with hydrogen is postulated. However, this cannot be assumed for the case of in-service welding on pipelines in pressurized condition. The reason is the increased temperature e.g. by preheating and (in particular) during welding of the single passes. As a result, the inner pipeline surface undergoes multiple short-term heating but to high temperatures. In particular, the first passes can result in a temperature close to the austenitic transformation of the material for small wall thicknesses. Both increase the hydrogen uptake into the welded joint. If hydrogen embrittlement is likely to occur, depends on the hydrogen uptake, which must be quantified. For this purpose, welding experiments on pressurized demonstrators were conducted. The hydrogen uptake at 100 bar was compared to reference experiments with nitrogen. A new sample extraction routine for the quantification of the weld-zone specific hydrogen uptake was established. Comprehensive experiments with different steels (P235, L360, L485), wall thicknesses (4.1 mm to 7.8 mm) and diameters (DN50 and DN200) were conducted. In addition, the influence of the welding layer sequence on the hydrogen uptake between single- and multi-layer welds was investigated. Analytical approaches were used to approximate the hydrogen uptake in the respective weld zones. The main findings were that the layer sequence and especially the wall thickness have a large influence on the hydrogen uptake. T2 - 20th Pipeline Technology Conference ptc2025 CY - Berlin, Germany DA - 06.05.2025 KW - In-service KW - Hydrogen KW - Pipeline KW - Repair welding KW - Component test PY - 2025 AN - OPUS4-63165 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Grimault de Freitas, Tomás T1 - Repair Welding on Future Pressurized Hydrogen Pipelines N2 - Hydrogen is the energy carrier for a sustainable future without fossil fuels. This requires a reliable transport infrastructure. In this context, the conversion of existing natural gas (NG) grids is an essential part of the worldwide hydrogen strategies, in addition to the construction of new pipelines. Given the known effects of hydrogen embrittlement, the compatibility of the materials already in use (typically low alloy steels in a wide range of strengths and thicknesses) must be investigated. Initial comprehensive studies of the hydrogen compatibility of pipeline materials indicate that these materials can be used to a certain extent. However, pipelines require frequent maintenance and repair. In some cases, it is necessary to perform welding on pipelines while they are under pressure, such as the well-known tapping of natural gas grids. This in-service welding presents additional challenges for hydrogen operations in terms of additional hydrogen absorption during welding and material compatibility. The challenge can be roughly divided into the possible austenitization of the inner pipe material exposed to hydrogen, which can lead to sufficient hydro- gen absorption, and the welding itself, which causes an increased temperature range. Both lead to a significant increase in hydrogen solubility and diffusivity of the respective materials compared to room temperature. In this context, knowledge about hot tapping on hydrogen pipelines is scarce due to the lack of operating experience. Fundamental experimental investigations are required to investigate the possibility of transferring the state-of-the-art concepts from natural gas to hydrogen pipeline grids to ensure that no critical material degradation occurs due to the potentially increased hydrogen uptake. For this reason, the presentation will present the state of the art in hydrogen pipeline hot tapping, including current research projects and their solution strategies in terms of pressurized mock-ups and basic testing scenarios. T2 - ASTM Conference on Hydrogen Materials CY - La Rochelle, France DA - 03.06.2025 KW - Component Test KW - Hydrogen KW - In-service welding KW - Pipeline PY - 2025 AN - OPUS4-63332 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Fey, Gero T1 - Dilatometry Based Determination of Continuous Cooling Transformation (CCT) Diagrams in Low Alloy Pipeline Steels for Hydrogen transportation N2 - This study investigates the suitability of low-alloy pipeline steels for hydrogen transportation, focusing on the development of weld microstructures. Previous research has been limited by a deficiency in the understanding of how different microstructural components respond to trapped hydrogen. By developing Continuous Cooling Transformation (CCT) diagrams through dilatometry analysis, this study explores the impact of t8/5-cooling times (the time between 800 °C and 500 °C) on the microstructure and mechanical properties of the HAZ compared to the base material. The findings provide valuable insights into how cooling times influence transformation temperatures and microstructure development, which, in turn, affect hydrogen diffusion and absorption. These findings establish a foundation for future investigations into hydrogen's impact on weld microstructures, including experimental studies, with the aim of optimizing welding practices and enhancing resistance to hydrogen-assisted cracking. Ultimately, this research contributes to improving the safety and reliability of hydrogen transportation systems in commonly used industrial pipeline steels. T2 - 20th Pipeline Technology Conference CY - Berlin, Germany DA - 05.05.2025 KW - Pipelinestahl KW - CCT PY - 2025 AN - OPUS4-63098 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Fey, Gero T1 - Thermophysically Simulated Weld HAZ and CCT Diagram of High Strength Low Alloy Pipeline Steel N2 - Green produced Hydrogen is considered as a key energy carrier for the transition to a more sustainable energy supply. Large-scale infrastructure projects, such as the European Hydrogen Backbone, aim to establish a hydrogen pipeline network connecting production and consumption regions. To enable this distribution, existing and newly build pipeline networks play a crucial role. High-strength low-alloy (HSLA) pipeline steels such as L485ME (X70) are therefore faced to challenges associated with hydrogen transportation. One critical challenge in hydrogen transportation is hydrogen-assisted cracking (HAC), which is influenced by mechanical loading, hydrogen content, and the material itself. The microstructure of the steel has a significant impact on its resistance to HAC. Since pipeline tube sections are commonly joined by welding, the weld metal and heat-affected zone (HAZ) reveal different microstructures compared to the base material. In particular, the coarse grain heat affected zone (CGHAZ) is considered to be a critical zone for HAC. Therefore, the understanding of the resulting microstructure in the HAZ is essential to assess the material’s performance under hydrogen exposure. A quenching dilatometer was used to simulate the weld HAZ of an HSLA L485ME pipeline steel. The influence of cooling on the CGHAZ was investigated at a peak temperature of 1250°C using varying t8/5-cooling times (from 2 s up to 500 s), focusing on microstructural evolution and hardness. Based on these experiments, a continuous cooling transformation (CCT) diagram was constructed. Additionally, other regions of the weld HAZ were thermophysically simulated using two different t8/5-cooling times, namely 6 s and 15 s, while varying the peak temperature between 1250°C and 800°C. The resulting microstructures and hardness values were analyzed and compared. T2 - IIW Intermediate Meeting CY - Trollhättan, Sweden DA - 10.03.2025 KW - L485ME KW - Pipeline steel KW - CCT KW - Heat-affected zone KW - Dilatometry PY - 2025 AN - OPUS4-63102 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Assessment of in-service welding conditions for pressurized hydrogen pipelines via component test N2 - Hydrogen is the energy carrier of tomorrow. This requires a reliable transport infrastructure with the ability to carry large amounts of hydrogen e.g. for steel industry or chemical industry. The conversion of existing natural gas (NG) grids is an essential part of the worldwide hydrogen strategies, in addition to the construction of new pipelines. In this context, the transportation of hydrogen is fundamental different from NG as hydrogen can be absorbed into the pipeline material. Given the well-known effects of hydrogen embrittlement, the compatibility of the materials for the intended pipelines must be investigated (typically low alloy steels in a wide range of strengths and thicknesses). However, pipelines require frequent maintenance, repair or the need for installation for further outlets. In some cases, it is necessary to perform welding on or onto the pipelines while they are still in service, i.e. with active gas flow under high pressure, e.g. such as the well-known “hot tapping”, see Fig. 1a. This in-service welding causes challenges for hydrogen operations in terms of additional hydrogen absorption during welding and the material compatibility. The challenge can be roughly divided into the possible austenitization of the inner pipe material exposed to hydrogen, which can lead to sufficient hydrogen absorption, and the welding itself, which causes an increased temperature range. Both lead to a significant increase in hydrogen solubility and diffusivity of the respective materials compared to room temperature. In this context, knowledge about hot tapping on hydrogen pipelines is scarce due to the lack of operating experience. Fundamental experimental investigations are required to investigate the transferability from NG to hydrogen pipeline grids. For this reason, the present study introduces a specially designed mock-up / demonstrator concept for the realistic assessment of the welding processing conditions, see Fig. 1b. The mock-up was designed to enable in-situ temperature measurement during welding as well as ex-post extraction of samples for the quantification of the absorbed hydrogen concentration, see Fig. 1c. For safety measures, the necessary pressurized hydrogen volume was limited by the insertion of a solid cylinder ensuring a 1 cm hydrogen gas layer. Welding experiments on the pressurized mock-ups with the diameters DN50 and DN200 have shown that the austenitization temperature can be reached on the inner surface of the pipeline, especially on thinner-walled pipelines, using current welding practices. This corresponds to an increased hydrogen uptake in the welded area of several ppm T2 - 1st Conference on Hydrogen in Materials Science and Engineering (H2-MSE) CY - Siegburg, Germany DA - 11.02.2025 KW - Hydrogen KW - Pipeline KW - In-service welding KW - Component test PY - 2025 AN - OPUS4-62544 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kaiser, Sebastian T1 - Component-like demonstrator for determination of temperature field and inner surface temperatures during in-service welding of hydrogen pipelines N2 - Hydrogen is considered as one of the most important energy carriers in the future. The necessary large-scale transport over long distances requires a suitable pipeline infrastructure. Current plannings encompass a dual-way strategy of repurposing existing natural gas (NG) pipelines, supplemented by the construction of new hydrogen pipelines. In some cases, such as necessary grid extensions or installation of bypasses in case of repair work, techniques like “hot tapping” are applied. These techniques include so-called in-service welding on pressurized pipelines and are state-of-the-art for NG grids and oil pipelines. The existing NG pipeline grid consists of a wide range of materials with different strengths, diameters, and wall thicknesses. In this context, the material compatibility is crucial. The main difference between hydrogen and NG is that hydrogen can both penetrate the material and cause hydrogen embrittlement. In that connection, in-service welding encompasses elevated temperatures for a certain time during the typically multi-layer welding process. Locally even austenitization temperature can be reached or surpassed. Austenite has a higher hydrogen solubility at a significantly lower diffusion rate, which could lead to a critical hydrogen accumulation. Especially the inner pipe surface temperature is from utmost interest, as this interface is exposed to the pressurized hydrogen (up to 100 bar). However, direct measurement of the locally occurring temperatures is very challenging. For this reason, a component-like geometry was developed. The geometry consists of a pipeline segment with a metal sheet joined to the pipe segment, representing similar heat dissipation conditions as in the field. In addition, typical welding parameters were applied that are currently used in the NG grid. This allows the welding of realistic multi-layer fillet welds on the outer pipe wall with simultaneous temperature measurement using manifold thermocouples at defined positions: (1) adjacent to the weld seam on the outer pipe surface, (2) on the inner pipe surface and (3) on the welded metal sheet. To ensure realistic conditions, manual shielded metal arc welding (SMAW) and gas tungsten arc welding (GTAW) was investigated. The effects of different wall thicknesses and welding heat inputs on the temperature distribution and peak temperatures achieved on the inner pipe surface during welding vary depending on the chosen method. Peak temperatures above austenitization temperature up to 1078 °C have been measured on L245 pipes with wall thickness of 3.6 mm. For pipes made from higher strength materials, such as L485, with a wall thickness of 8 mm, peak temperatures between 607 °C and 755 °C were recorded. Temperature and austenitization directly affects hydrogen diffusivity and solubility, showing the importance of the findings. The temperature profile and cooling conditions influence the mechanical properties of the material as well. For this reason, metallurgical investigations are carried out to assess the hardness and microstructure of the welds. Hardening up to 248 HV10 was detected in the heat-affected zone (HAZ) of the top layer, which could lead to a locally increased susceptibility to hydrogen assisted cracking. Meanwhile, the minimum hardness found in the HAZ of the root layer was as low as 144 HV10, indicating a softening. The results of this study provide valuable insights into the suitability of existing materials and geometries for hydrogen transport. Secondly, the data collected will serve as a basis for planned numerical simulations to further improve knowledge and optimize welding processes to ensure the integrity and safety of hydrogen pipelines. T2 - 78th IIW Annual Assembly and International Conference, Meeting of Commission II-C: "Testing and Measurement of Welds" CY - Genoa, Italy DA - 22.06.2025 KW - Pipeline KW - Welding KW - Inner-surface temperature KW - Temperature measurement KW - Hydrogen PY - 2025 AN - OPUS4-63637 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kaiser, Sebastian T1 - Assessment of in service welding conditions for pressurized hydrogen pipelines via component test N2 - Hydrogen is the energy carrier of tomorrow for a fossil-free future. This requires a reliable transport infrastructure with the ability to carry large amounts of hydrogen e.g. for steel industry or chemical industry. The conversion of existing natural gas (NG) grids is an essential part of the worldwide hydrogen strategies, in addition to the construction of new pipelines. In this context, the transportation of hydrogen is fundamental different from NG as hydrogen can be absorbed into the pipeline material. Given the well-known effects of hydrogen embrittlement, the compatibility of the materials for the intended pipelines must be investigated (typically low alloy steels in a wide range of strengths and thicknesses). However, pipelines require frequent maintenance, repair or the need for installation for further outlets. In some cases, it is necessary to perform welding on or onto the pipelines while they are still in service, i.e. with active gas flow under high pressure, e.g. such as the well-known “hot tapping”. This in-service welding causes challenges for hydrogen operations in terms of additional hydrogen absorption during welding and the material compatibility. The challenge can be roughly divided into the possible austenitization of the inner pipe material exposed to hydrogen, which can lead to sufficient hydrogen absorption, and the welding itself, which causes an increased temperature range. Both lead to a significant increase in hydrogen solubility and diffusivity of the respective materials compared to room temperature. In this context, knowledge about hot tapping on hydrogen pipelines is scarce due to the lack of operating experience. Fundamental experimental investigations are required to investigate the transferability from NG to hydrogen pipeline grids. For this reason, the present study introduces a specially designed mock-up / demonstrator concept for the realistic assessment of the welding processing conditions. The mock-up was designed to enable in-situ temperature measurement during welding as well as ex-post extraction of samples for the quantification of the absorbed hydrogen concentration. For safety measures, the necessary pressurized hydrogen volume was limited by the insertion of a solid cylinder ensuring a 1 cm hydrogen gas layer. Welding experiments on the pressurized mock-ups with the diameters DN60 and DN200 have shown that the austenitization temperature can be reached on the inner surface of the pipeline, especially on thinner walled pipelines, using current welding practices. This corresponds to an increased hydrogen uptake in the welded area of several ppm. T2 - 78th IIW Annual Assembly and International Conference, IC-Session "Hydrogen Applications and Energy Transition" CY - Genoa, Italy DA - 22.06.2025 KW - Pipeline KW - Welding KW - Hydrogen KW - In-Service KW - Component-testing PY - 2025 AN - OPUS4-63638 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Determination of inner pipe surface temperatures during in-service welding on hydrogen pipelines by means of component-like mock up experiments N2 - Hydrogen is considered as one of the most important energy carriers in the future. The necessary large-scale transport over long distances requires a suitable pipeline infrastructure. Current plannings encompass a dual-way strategy of repurposing existing natural gas (NG) pipelines, supplemented by the construction of new hydrogen pipelines. In some cases, such as necessary grid extensions or installation of bypasses in case of repair work, techniques like “hot tapping” are applied. These techniques include so-called in-service welding on pressurized pipelines and are state-of-the-art for NG grids and oil pipelines. The existing NG pipeline grid consists of a wide range of materials with different strengths, diameters, and wall thicknesses. In this context, the material compatibility is crucial. The main difference between hydrogen and NG is that hydrogen can both penetrate the material and cause hydrogen embrittlement. In that connection, in-service welding encompasses elevated temperatures for a certain time during the typically multi-layer welding process. Locally even austenitization temperature can be reached or surpassed. Austenite has a higher hydrogen solubility at a significantly lower diffusion rate, which could lead to a critical hydrogen accumulation. Especially the inner pipe surface temperature is from utmost interest, as this interface is exposed to the pressurized hydrogen (up to 100 bar). However, direct measurement of the locally occurring temperatures is very challenging. For this reason, a component-like geometry was developed. The geometry consists of a pipeline segment with a metal sheet joined to the pipe segment, representing similar heat dissipation conditions as in the field. In addition, typical welding parameters were applied that are currently used in the NG grid. This allows the welding of realistic multi-layer fillet welds on the outer pipe wall with simultaneous temperature measurement using manifold thermocouples at defined positions: (1) adjacent to the weld seam on the outer pipe surface, (2) on the inner pipe surface and (3) on the welded metal sheet. To ensure realistic conditions, manual shielded metal arc welding (SMAW) and gas tungsten arc welding (GTAW) was investigated. The effects of different wall thicknesses and welding heat inputs on the temperature distribution and peak temperatures achieved on the inner pipe surface during welding vary depending on the chosen method. Peak temperatures above austenitization temperature up to 1078 °C have been measured on L245 pipes with wall thickness of 3.6 mm. For pipes made from higher strength materials, such as L485, with a wall thickness of 8 mm, peak temperatures between 607 °C and 755 °C were recorded. Temperature and austenitization directly affects hydrogen diffusivity and solubility, showing the importance of the findings. The temperature profile and cooling conditions influence the mechanical properties of the material as well. For this reason, metallurgical investigations are carried out to assess the hardness and microstructure of the welds. Hardening up to 248 HV10 was detected in the heat-affected zone (HAZ) of the top layer, which could lead to a locally increased susceptibility to hydrogen assisted cracking. Meanwhile, the minimum hardness found in the HAZ of the root layer was as low as 144 HV10, indicating a softening. The results of this study provide valuable insights into the suitability of existing materials and geometries for hydrogen transport. Secondly, the data collected will serve as a basis for planned numerical simulations to further improve knowledge and optimize welding processes to ensure the integrity and safety of hydrogen pipelines. T2 - IIW Intermediate Meeting, Com. II-A CY - Trollhättan, Sweden DA - 10.03.2025 KW - Testing KW - In-service welding KW - Hydrogen KW - Pipelines PY - 2025 AN - OPUS4-62690 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Influence of various microalloying strategies on the mechanical properties of weld seams in S690QL steel N2 - Microalloying elements such as niobium (Nb) and titanium (Ti) play a crucial role in achieving the desired mechanical properties of quenched and tempered high-strength fine-grained structural steels with a nominal yield strength of ≥ 690 MPa. Current specifications for the chemical composition only define upper limits for these elements, providing manufacturers with some flexibility. However, even minor deviations in alloying concepts can significantly influence the resulting mechanical properties. Consequently, accurately predicting weldability and the integrity of welded joints becomes challenging or even unfeasible due to variations in composition and the associated microstructural changes. Potential adverse effects include the softening of the heat-affected zone (HAZ) or, conversely, localized hardening phenomena. To address these challenges, various microalloying strategies with different Ti and Nb contents are being systematically investigated for the first time using specially designed laboratory-cast alloys. Each alloying approach is based on the commonly used S690QL steel grade while maintaining consistent chemical composition and heat treatment parameters. To evaluate the weldability, three-layer welds were produced using gas metal arc welding (GMAW), and critical microstructural regions, particularly those within the heat-affected zone (HAZ) exhibiting significant softening or hardening, were identified. The influence of the softened HAZ region on failure behavior was assessed through transverse tensile testing. Digital image correlation (DIC) was employed for in situ analysis of local strain distributions across different HAZ regions. In addition, Charpy tests were carried out on BM, WM and HAZ to determine the Charpy impact toughness. This was supported by metallographic analyses and thermodynamic simulation using ThermoCalc. T2 - IIW Intermediate Meeting, Com. II-A CY - Trollhättan, Sweden DA - 10.03.2025 KW - Welding KW - Microalloy elements KW - High strength steels KW - Mechanical properties PY - 2025 AN - OPUS4-62691 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -