TY - JOUR A1 - Rhode, Michael A1 - Mente, Tobias A1 - Kannengießer, Thomas A1 - Schaupp, Thomas A1 - Zavdoveev, Anatoly T1 - Challenges for testing hydrogen-assisted cold cracking in weld seams of high-strength steel grades N2 - Hydrogen can cause weld cold cracking even days after fabrication. In this respect, higher strength steels present a challenge to established cold crack testing. In general, the tolerable hydrogen concentration for crack prevention decreases with increasing material strength. In addition, advanced welding processes require changes in weld geometry and heat input. This directly influences the formation of crack-critical microstructures, e.g. in hardened areas of the heat-affected zone. The limits of use and application of modern cold cracking tests are evaluated by (1) the externally loaded Implant-test and (2) the self-restraint Tekken-test. In particular, external mechanical stresses, which cause additional mechanical loads on the components during welding, must be considered due to the component-specific stiffness of high-strength steels. Accompanying test methods for determining hydrogen concentration and diffusion in welds are presented, such as carrier gas hot extraction for determining hydrogen concentration (ISO 3690) or temperature-dependent diffusion coefficients. These values are of great importance for a holistic approach to the evaluation of the cold cracking sensitivity of high strength steels. KW - Hydrogen KW - Welding KW - Cold cracking test KW - High-strength steel PY - 2024 DO - https://doi.org/10.37434/tpwj2024.08.01 SN - 0957-798X VL - 2024 IS - 8 SP - 3 EP - 9 PB - International Association "Welding" CY - Kyiv, Ukraine AN - OPUS4-60946 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Griesche, Axel T1 - Crystallographic phase transformations and corresponding temperature distributions during gtaw of supermartensitic stainless steel visualized by nbei N2 - We investigated the phase transformations during butt-welding of supermartensitic steel plates with help of Neutron-Bragg-Edge Imaging (NBEI). Gas tungsten arc welding (GTAW) was used with a motorized torch allowing for automated weldments. The austenitization in the heat affected zone (HAZ) could be clearly visualized at λ = 0.39 nm, a wavelength smaller than the Bragg edge wavelengths of both austenite and martensite. The re-transformation into the martensitic phase during cooling was clearly detected. However, we observed an unexpected additional change in transmission at λ = 0.44 nm, a wavelength larger than the wavelength of the Bragg edges of both the martensitic and austenitic phases. We attribute this change to the Deybe-Waller-Factor that describes the temperature dependence of coherent scattering at a crystal lattice. The observed two-dimensional attenuation map corresponds well with a temperature distribution modelling by software macros in ANSYS [3]. Here, the absolute temperature values could be achieved by calibrating the modelled attenuation with help of a thermocouple placed at the steel plate. This allows in return for a direct two-dimensional temperature reading based on the Debye-Waller-relation between neutron attenuation and sample temperature. T2 - WCNR-12 CY - Idaho Falls, Id, USA DA - 02.06.2024 KW - Neutron KW - Radiography KW - Welding PY - 2024 AN - OPUS4-60242 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rhode, Michael A1 - Mente, Tobias A1 - Kannengießer, Thomas T1 - Parameters and challenges for reliable hydrogen determination in welded joints by carrier gas hot extraction N2 - For the hydrogen-based energy economy of tomorrow, the construction of the necessary infrastructure will play a central role. Most materials used to date, such as welded steels, can be prone to hydrogen embrittlement under certain conditions. This includes the classic delayed cold cracking during welding as well as degradation phenomena during service of components in hydrogen-containing environment. For the evaluation of any hydrogen effect, for example, on the mechanical properties of a welded metallic material, the hydrogen content must be precisely determined. In the case of weld seams, the carrier gas hot extraction (CGHE) according to ISO 3690 is meanwhile state-of-the-art. CGHE is based on accelerated hydrogen degassing due to the thermal activation of hydrogen at elevated temperatures. In addition to the quantification of hydrogen, thermal desorption analysis (TDA) with varying heating rates can be used to determine and evaluate the hydrogen trapping at microstructural defects in the material. For both techniques, experimental and metrological influences must be considered, which have a major effect on the result. For example, ISO 3690 suggests different sample geometries and minimum extraction times for CGHE. This study summarizes the results and experiences of numerous investigations at the Federal Institute for Materials Research and Testing (BAM) with different sample temperatures and geometries (ISO 3690 type B and cylindrical TDA samples) regarding the influence of the sample surface (polished/welded), measurement accuracy depending on the sample volume and the insufficient monitoring of the effect of PI control on the extraction temperature. A deviating extraction temperature from the target temperature can significantly falsify the measurement results. Based on the results, methods are shown which allow the desired extraction temperature to be reached quickly without physically interfering with the measuring equipment. This serves to significantly improve the reliability of the hydrogen measurement through increased signal stability and accelerated hydrogen desorption. In general, an independent temperature measurement with dummy samples is recommended for the heating procedure of choice to exclude possible undesired temperature influences before the measurement. The methods described can be transferred directly to industrial applications KW - Welding KW - Hydrogen measurement KW - ISO 3690 KW - Carrier gas hot extraction PY - 2024 DO - https://doi.org/10.37434/tpwj2024.04.01 SN - 0957-798X VL - 4 SP - 3 EP - 10 PB - International Association Welding AN - OPUS4-60071 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Processing and application properties of multiple principal element alloys (MPEA) N2 - The presentation gives an overview of BAM's activities on processing influences and application properties of MPEAs in the form of joined and machined high and medium entropy alloys (CoCrFeMnNi and CoCrNi). In the case of welding, the focus is on defect-free welded joints with sufficient mechanical properties. In the case of machining, the focus is on the possible influence on the surface quality of the materials through adequate milling parameters. In addition, the hydrogen absorption and diffusion properties as well as the electrochemical corrosion behavior are fundamentally examined. T2 - FAU-Department Werkstoffwissenschaften, Seminar: Aktuelle Probleme der Werkstoffwissenschaften CY - Erlangen, Germany DA - 25.04.2024 KW - Welding KW - Application properties KW - Machining KW - High-entropy alloy KW - Hydrogen PY - 2024 AN - OPUS4-59975 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Combined effect of heating rate and restraint condition on stress relief cracking susceptibility during PWHT of thick-walled Cr-Mo-V steel submerged arc welded joints N2 - Contemporary steels creep-resistant steels like the 13CrMoV9-10 are used as thick plates e.g., for applications in hydrocrackers. The large plate thickness requires high efficiency welding processes like submerged arc welding (SAW) and a mandatory post weld heat treatment (PWHT). The PWHT-parameters stem from a combination of empirical knowledge and traditional experiments on free shrinking (FS) welds. In that connection, the formation of so-called stress-relief cracking (SRC) must be anticipated. The SRC susceptibility of a welded component is a complex combination and interaction of com-ponent specific, thermal, and metallurgical factors. Many of which have to date not been conclusively researched. For example, it is well known that SRCs develop during PWHT due to formation and growth of carbides on prior austenite grain boundaries, resulting in a significant hardness increase (secondary hardening) and toughness decrease. This leads to a high SRC susceptibility of the coarse grain heat-affected zone (CGHAZ) of the last weld bead during PWHT. This is intensified in case of high residual stresses from the component-specific, structurally induced stiffness. In combination with multi-layer welding this leads to a multiaxial stress distribution. Nonetheless, the combined effect of PWHT and high-residual stresses on the SRC formation is merely unknown. For that reason, this study presents the effect of different heating rates in conjunction with a certain component stiffness. For that reason, SAW joints of 13CrMoV9-10 steel were investigated under FS and defined external restraint condition. T2 - IIW Intermediate Meeting, Com. II-A CY - Incheon, Republic of Korea DA - 12.03.2024 KW - Stress relief cracking KW - Welding KW - Post weld heat treatment KW - Submerged arc welding KW - Cr-Mo-V steel KW - Creep-resisting steel PY - 2024 AN - OPUS4-59673 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Reliable hydrogen determination in metallic materials and their weld joints: Parameters and challenges N2 - In the course of tomorrow's hydrogen-based energy transition, the construction of the corresponding infrastructure will play a central role. The majority of materials used to date are typically welded for component fabrication. In that context, steels are widely applied and can be prone to hydrogen embrittlement. This includes the classical delayed cold cracking during welding processing as well as embrittlement phenomena during operation. For the evaluation of any hydrogen effect on, for example, the mechanical properties of a welded metallic material, the hydrogen content must be precisely determined. In the case of welds, for example, according to ISO 3690, this is the isothermal carrier gas hot extraction (CGHE). CGHE is based on accelerated hydrogen degassing due to thermal activation of hydrogen at elevated temperatures. In addition to the pure quantification of hydrogen, thermal desorption analysis (TDA) with varied heating rates can be used to determine and evaluate the bonding state at microstructural defects in the material. For both techniques, experimental and measurement influences have to be considered, which have a great effect on the result. For CGHE, for example, ISO 3690 suggests different sample geometries as well as minimum extraction times. The present study summarizes results and experiences of numerous investigations with different sample temperatures and geometries (ISO 3690 type B and cylindrical TDA samples) regarding: the influence of the sample surface (polished/welded), measurement accuracies depending on the sample volume as well as the insufficient monitoring of the effect of the PI controller on the extraction temperature. In particular, a deviating extraction temperature to the set temperature, can significantly falsify the measurement results. Based on the results, methods are shown to quickly reach the desired extraction temperature without having to physically interfere with the measurement equipment. This serves to substantially improve the reliability of hydrogen measurement through increased signal stability and accelerated hydrogen desorption. In general, an independent temperature measurement with dummy samples for the selected heating procedure is advisable to exclude possible unwanted temperature influences already before the measurement. In addition (and way more important), the methods described can be transferred directly to industrial applications. T2 - 47th MPA-Seminar CY - Stuttgart, Germany DA - 10.10.2023 KW - Hydrogen assisted cracking KW - Carrier gas hot extraction KW - Welding KW - ISO 3690 KW - Metals PY - 2023 AN - OPUS4-58677 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Microalloying influence on precipitation behavior and mechanical properties of welded high strength structural steels N2 - Microalloying elements, such as Nb and Ti, are essential for the targeted mechanical strength of quenched and tempered, high-strength fine-grained structural steels with a nominal yield strength ≥ 690 MPa. Current specifications for chemical composition only provide upper limits for manufacturers. But even small deviations in the alloying route can have a drastic effect on the mechanical properties. Thus, an adequate prediction of the weldability and the integrity of the welded joint becomes difficult or even impossible due to the varying composition and, hence, the microstructures. Undesirable side effects are the possible softening of the heat-affected zone (HAZ) as well as the opposite effect of hardening. Against this background, different microalloying routes with varying Ti and Nb contents are systematically investigated for the first time on specially designed lab-cast alloys. The basis of each alloy route was the common S690QL in terms of both the chemical composition as well as the heat treatment. To investigate the weldability, three-layer welds were performed using metal active gas welding (MAG) and critical microstructural areas with high softening/hardening were identified. The scope was here on the identification of phase transformations during cooling and on the respective metallurgical precipitation behavior. Isothermal and non-isothermal phase calculations were performed using Thermo-Calc® and showed that the prediction of the non-equilibrium precipitation characteristics during welding is not trivial, especially for this relatively complex chemical composition. The mechanical properties of the welded joints were identified by both Charpy tests (toughness) and tensile tests (strain and strength). During the test, the local straining behavior of the welded joints, was identified using a digital image correlation (DIC) system, see Figure 1. Despite the generally good weldability of the materials, the results show a significant influence of the microalloying route as well as the welding heat input on the different precipitation kinetics. T2 - FEMS EUROMAT 2023 CY - Frankfurt a. M., Germany DA - 04.09.2023 KW - High-strength KW - Steel KW - Mechanical properties KW - Welding KW - Thoughness PY - 2023 AN - OPUS4-58221 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk A1 - Rhode, Michael T1 - Local mechanical properties of TIG dissimilar metal welded CoCrFeMnNi high-entropy alloy to austenitic steel AISI 304 N2 - Multiple principal element alloys (MPEA) encompass the well-known high entropy alloys (HEAs). MPEA/HEA represent a new class of materials consisting of at least three alloying elements, each containing 5 to 35 at.-%. This alloying concept thus differs fundamentally from conventional materials such as steel or nickel alloys. For this purpose, the alloying elements are specifically selected, and the microstructures are adjusted in a single-phase and, in some cases, multi-phase manner. In particular, conflicting goals, such as the trade-off between strength and ductility in conventional steels, are overcome. In the last 20 years, however, the focus has been on material synthesis. With the increase in available material quantities, the focus is now on pro-cessing issues such as joining and welding processes. The weldability of MPEA has received very little atten-tion so far. Experience with dissimilar metal welds (DMWs) is completely lacking but is essential for the appli-cation of these materials in combination with conventional materials. The present study presents, comprehen-sive experimental results on the weldability of MPEA-DMWs. For that purpose, a Co20Cr20Fe20Mn20Ni20 HEA in cold-rolled and heat-treated condition was joined by means of tungsten inert gas welding (TIG) with the austenitic Cr-Ni steel AISI 304. The DMWs resulted in interesting mechanical properties. They were obtained by instrumented tensile tests as well as the local deformation in the weld area by using digital image correlation (DIC) technique. A significant softening in the heat-affected zone (HAZ) of the MPEAs as well as a slightly reduced tensile strength with a significant decrease of the elongation at fracture were found. The experiments provided proof in principle of the weldability of the MPEAs for DMWs with conventional materials that ensure a corresponding capability for mechanical loading. This allows further considerations on the application of these innovative materials. T2 - IIW Annual Assembly, Meeting of Commission C-II CY - Singapore DA - 18.07.2023 KW - High-entropy alloy KW - Welding KW - Microstructure KW - Mechanical properties KW - Dissimilar metal weld PY - 2023 AN - OPUS4-57978 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Manzoni, Anna Maria T1 - Mechanical performance and integrity of tungsten inert gas (TIG) welded CoCrFeMnNi high entropy alloy with austenitic steel AISI 304 N2 - High entropy alloys (HEA) are a new class of materials that have been investigated since the early 2000s and offer great potential to replace conventional alloys. However, since they sometimes have significant contents of expensive alloying elements such as Co or Ni, their use is only conceivable in highly stressed areas of components. For this purpose, the weldability with conventional alloys such as high-alloy austenitic steels must be investigated. In addition to the resulting microstructure, the mechanical properties are also fundamental for the usability of HEAs in DMWs. For this purpose, TIG welds of CoCrFeMnNi HEA (cold rolled and recrystallized state) with AISI 304 austenitic steel are investigated. These mechanical properties are analyzed in this work by means of tensile tests and local hardness measurement. The local strain behavior of the welded joints is also characterized by means of Digital Image Correlation (DIC). The results of the local hardness measurement show a clear influence of the initial condition of the HEA on the HAZ. Thus, the HEA in the cold-rolled condition shows a clear softening because of recrystallization processes in the HAZ. On the other hand, there is no influence on the hardness of the weld metal, which is approx. 200 HV0.1 in both cases. The tensile tests show a consistent failure of the weld in the weld metal. However, regardless of the HEA condition, strengths in the range of the recrystallized HEA (RM ~ 550–600 MPa) are achieved, although with significantly reduced fracture elongations. T2 - International Conference on High-Entropy Materials (ICHEM 2023) CY - Knoxville, TN, USA DA - 18.06.2023 KW - Multi-principal element alloys KW - Welding KW - Mechanical properties KW - Dissimilar metal weld KW - Digital image correlation PY - 2023 AN - OPUS4-57713 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Richter, Tim T1 - Local mechanical properties of TIG dissimilar metal welded high entropy alloy with austenitic steel AISI 304 N2 - High entropy alloys (HEA) are a new class of materials that have been investigated since the early 2000s and offer great potential to replace conventional alloys. However, since they sometimes have significant contents of expensive alloying elements such as Co or Ni, their use is only conceivable in highly stressed areas of components. For this purpose, the weldability with conventional alloys such as high-alloy austenitic steels must be investigated. In addition to the resulting microstructure, the mechanical properties are also fundamental for the usability of HEAs in DMWs. For this purpose, TIG welds of CoCrFeMnNi HEA (cold rolled and recrystallized state) with AISI 304 austenitic steel are investigated. These mechanical properties are analyzed in this work by means of tensile tests and local hardness measurement. The local strain behavior of the welded joints is also characterized by means of Digital Image Correlation (DIC). The results of the local hardness measurement show a clear influence of the initial condition of the HEA on the HAZ. Thus, the HEA in the cold-rolled condition shows a clear softening because of recrystallization processes in the HAZ. On the other hand, there is no influence on the hardness of the weld metal, which is approx. 200 HV0.1 in both cases. The tensile tests show a consistent failure of the weld in the weld metal. However, regardless of the HEA condition, strengths in the range of the recrystallized HEA (RM ~ 550–600 MPa) are achieved, although with significantly reduced fracture elongations. T2 - IIW Intermediate Meeting of Commission II-A CY - Garching, Germany DA - 06.03.2023 KW - High-entropy alloy KW - Welding KW - Dissimilar metal weld (DMW) joint KW - Mechanical properties KW - Digital image correlation PY - 2023 AN - OPUS4-57108 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Richter, Tim A1 - Schröpfer, Dirk A1 - Rhode, Michael T1 - Residual stresses in a high- and a medium-entropy alloy due to TIG and friction stir welding N2 - The new alloying concept of multi-element systems with defined entropy (HEA—high-entropy alloy; MEA—medium-entropy alloy) is gaining increasing importance in materials research. Significantly improved properties or combinations of properties are shown by some HEA/MEA systems. Thus, primarily the production and resulting microstructures of HEA, as well as its properties, have been investigated so far. Furthermore, processing is a main issue in transferring HEA systems from the laboratory to real components. Since welding is the most important joining process for metals, it is crucial to investigate the influence of welding to guarantee component integrity. Welding leads to residual stresses, which significantly affect the component integrity. Hence, the focus of this study is the residual stress formation and distribution in a CoCrFeMnNi HEA and ternary CoCrNi MEA using two different welding processes: tungsten inert gas (TIG) welding and solid-state friction stir welding (FSW). As a pathway for the application of HEA in this investigation, for the first time, residual stress analyses in realistic near-component specimens were performed. The residual stresses were determined by X-ray diffraction (XRD) on the surfaces of top and root weld side. The results were correlated with the local welding microstructures. The results show that both FSW and TIG generate significant tensile residual stresses on the weld surfaces in, and transverse to, the welding direction. In the case of FSW of the CoCrFeMnNi HEA, the longitudinal residual stresses are in the range of the yield strength of approx. 260 MPa in the weld zone. KW - High entropy alloy KW - Welding KW - Residual stresses KW - Microstructure PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-567039 DO - https://doi.org/10.3390/jmmp6060147 SN - 2504-4494 VL - 6 IS - 6 SP - 1 EP - 11 PB - MDPI CY - Basel AN - OPUS4-56703 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Richter, Tim T1 - Residual stresses in near-component specimens of a high and a medium entropy alloy due to tig and friction stir welding N2 - The new alloying concept of multi-element systems with defined entropy (HEA - High Entropy Alloy or MEA - Medium Entropy Alloy) is gaining increasing importance in materials research. Significantly improved properties or combinations of properties are shown by some HEA/MEA-systems, which have the potential to substitute conventional alloys such steels and are therefore promising for a wide range of applications, e.g., overcome of the trade-off between high strength and ductility. Thus, primarily the production and resulting microstructures of HEA as well as properties have been investigated so far. Furthermore, processing is a main issue to transfer HEA systems from the laboratory to real components, e.g., for highly stressed components. Since welding is the most important joining process for metals, it is crucial to investigate the influence of welding processing on these material properties to guarantee component integrity. Welding leads to residual stresses, which significantly affect the component integrity. Only a very few studies on the effect of welding on residual stresses in HEA and MEA weld joints are available so far. Hence, the focus of this study is the residual stress formation and distribution in a CoCrFeMnNi HEA and ternary CoCrNi MEA using two different welding processes: Tungsten Inert Gas (TIG) welding and soldi-state Friction Stir Welding (FSW). As a pathway for application of HEA in this investigation for the first time residual stress analyses in realistic near-component specimens were performed. The residual stresses were determined by X-ray diffraction (XRD) on the surfaces of top and root weld side. The results were correlated with the local welding microstructures. The results show that both FSW and TIG generate significant tensile residual stresses on the weld surfaces in and transverse to the welding direction. In the case of FSW of the CoCrFeMnNi HEA, the longitudinal residual stresses are in the range of the yield strength of approx. 300 MPa in the weld zone. T2 - OVGU-Kolloquium (BMDK des IWF) CY - Online meeting DA - 19.05.2022 KW - High Entropy Alloy KW - Welding KW - Residual stresses KW - Microstructure PY - 2022 AN - OPUS4-56671 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rhode, Michael A1 - Nietzke, Jonathan A1 - Richter, Tim A1 - Mente, Tobias A1 - Mayr, P A1 - Nitsche, A T1 - Hydrogen effect on mechanical properties and cracking of creep‑resistant 9% Cr P92 steel and P91 weld metal N2 - Martensitic 9% Cr steels like P91 and P92 can show an increased susceptibility to delayed hydrogen-assisted cracking. The focus of this study was the microstructure and heat treatment efect on the mechanical properties of P92 base material and P91 multi-layer weld metal in both as-welded and post weld heat treated (PWHT) condition. Tensile tests with hydrogen free reference samples and electrochemically hydrogen charged samples were carried out; the mechanical properties were assessed and supported by detailed fractographic analysis. Finally, a hydrogen and microstructure-dependent fracture criterion is established. All investigated microstructures showed a hydrogen-infuenced degradation of the mechanical properties compared to the hydrogen-free reference samples. The as-welded martensitic P91 weld metal had the highest degree of degradation in the presence of hydrogen. The P91 PWHT weld metal and the P92 base material had comparable properties. From that point of view, a signifcantly increased risk for hydrogen-assisted cold cracking during welding fabrication of P91 weld joints must be considered before any heat treatment is conducted. T2 - IIW Annual Assembly, Meeting of Commission IX-C CY - Tokyo, Japan DA - 16.07.2022 KW - Creep-resisting materials KW - Welding KW - Hydrogen assisted cracking KW - Hydrogen embrittlement KW - Mechanical properties PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-564070 DO - https://doi.org/10.1007/s40194-022-01410-5 SN - 0043-2288 SP - 1 EP - 12 PB - Springer Nature CY - Basel (CH) AN - OPUS4-56407 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Griesche, Axel T1 - The Debye-Waller Factor for Temperature Distribution Determination in NBEI Experiments: A Case Study for GTAW N2 - In Neutron-Bragg-Edge Imaging (NBEI) in situ experiments, we studied the phase transitions in martensitic steel sheets during butt-welding. Gas tungsten arc welding was used with a motorized torch allowing automated weldments. The austenitization in the heat affected zone underneath the welding head could be clearly visualized. Also, the retransformation into the martensitic phase upon cooling. However, we observed an unexpected additional change in transmission at λ = 0.44 nm that is at a wavelength larger than the wavelength of the Bragg edges of both the martensitic and austenitic phases. We attribute this change to the Deybe-Waller-Factor that describes the temperature dependence of coherent scattering at a crystal lattice. With help of temperature field simulations that were calibrated by the reading of anattached thermo couple during welding, we could show that the Debye-Waller factor can produce an additional image contrast. T2 - SNI 2022 CY - Berlin, Germany DA - 05.09.2022 KW - Welding KW - Debys-Waller-Factor KW - Neutron Imaging PY - 2022 AN - OPUS4-55630 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Influence of Residual Stresses on Stress Relief Cracking of Thick Walled Creep Resistant Steel 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 (400 mm x 400 mm x 25 mm) 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 submerged arc welding in a multi-layer technique. 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 instrument E3 of the research reactor BERII of HZB Berlin, Germany. Complementarily, laboratory X-ray diffraction was applied to characterize the surface residual stresses. In the welded state, especially in the weld metal and the adjacent HAZ, the residual stress can reach the yield strength of the untreated material. The highest levels occur in the longitudinal direction. The transverse and normal directions are characterized by residual stress of lower magnitude. As expected, the residual stress is almost completely relieved after PWHT. T2 - International Conference on Residual Stresses ICRS-11 CY - Nancy, France DA - 27.03.2022 KW - Welding KW - Creep-resistant steel KW - Stress relief cracking KW - Residual stress KW - Post weld heat treatment PY - 2022 AN - OPUS4-54577 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Residual stresses and hydrogen assisted cracking in thick walled submerged arc weld joints for offshore applications N2 - Offshore wind turbines continuously increase in size and weight and demand adequate offshore foundations concepts like monopiles, tripods or jackets. These components are typically submerged arc welded (SAW) high-strength thick steel plates like the S420ML. During welding, the occurrence of delayed hydrogen assisted cracking (HAC) must be anticipated. HAC is a critical combination of the local hydrogen concentration within a susceptible microstructure under certain mechanical load, i.e., the occurring (welding) residual stresses. The welding sequence of the thick-walled plates complicate the residual stress distribution due to the necessary repeated thermal cycling, i.e., welding seam / layer deposition to fill the joint. For that purpose, SAW with two-wire-technique was used to weld a specially designed and prototype-like mock-up of a real component with a thickness of 50 mm, filled with 22 passes and a seam length of 1,000 mm. Additional welded stiffeners simulated the effect of a high restraint, to stimulate critical HAC conditions. The residual stresses were determined by a robot XRD goniometer. A least square regression analysis of the sin²ψ-law by using multiple ψ- and φ-tilts was applied. Tensile residual stresses up to the yield limit are found both in the weld metal and in the heat-affected zone. Numerical modelling allowed the qualitative estimation of the hydrogen diffusion in the weld, enabling the determination of critical conditions for the formation of HAC. In a future step, a structural simulation will allow the assessment of the welding residual stresses and the comparison to the XRD-values. T2 - International Conference on Residual Stresses ICRS-11 CY - Nancy, France DA - 27.03.2022 KW - Welding KW - X-ray diffraction KW - Hydrogen KW - Cracking KW - Offshore steel PY - 2022 AN - OPUS4-54576 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Joining processes for components in hydrogen technologies: Current need and future importance N2 - This presentation gives an overview on the importance of joining processes for component fabrication in hydrogen technologies. For that reason, the current need and future research and developement activites are highlighted for the three technological fields: hydrogen storage, transport and use (in terms of the emerging field of additive manufacturing). Finally, some remarks are given for necessary changes in the standardization. T2 - IIW Intermediate Meeting, Comm. II-A "Welding Metallurgy" CY - Online meeting DA - 17.03.2022 KW - Hydrogen KW - Welding KW - Research KW - Review KW - Additive manufacturing PY - 2022 AN - OPUS4-54488 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rhode, Michael A1 - Richter, Tim A1 - Mente, Tobias A1 - Mayr, P. A1 - Nitsche, A. T1 - Thickness and microstructure effect on hydrogen diffusion in creep‑resistant 9% Cr P92 steel and P91 weld metal N2 - Martensitic 9% Cr steels like P91 and P92 show susceptibility to delayed hydrogen assisted cracking depending on their microstructure. In that connection, effective hydrogen diffusion coefficients are used to assess the possible time-delay. Limited data on room temperature diffusion coefficients reported in literature vary widely by several orders of magnitude (mostly attributed to variation in microstructure). Especially P91 weld metal diffusion coefficients are rare so far. For that reason, electrochemical permeation experiments had been conducted using P92 base metal and P91 weld metal (in as-welded and heat-treated condition) with different thicknesses. From the results obtained, diffusion coefficients were calculated using to different methods, time-lag, and inflection point. Results show that, despite microstructural effects, the sample thickness must be considered as it influences the calculated diffusion coefficients. Finally, the comparison of calculated and measured hydrogen concentrations (determined by carrier gas hot extraction) enables the identification of realistic diffusion coefficients. KW - Creep-resistant steel KW - Diffusion KW - Hydrogen assisted cracking KW - Welding KW - Electrochemical permeation PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-540645 DO - https://doi.org/10.1007/s40194-021-01218-9 SN - 0043-2288 SP - 1 EP - 16 PB - Springer Nature Switzerland AG AN - OPUS4-54064 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Joining Processes in Hydrogen Technologies - Current need and future R&D activites, a review N2 - This study gives an overview on the important field of joining processes for component fabrication in hydrogen technologies. For that reason, the current need and future research and developement activites are highlighted for the different technological field of hydrogen generation, storage, transport and use. In addition, the emerging field of additive manufacturing is included. Finally, some remarks are given for necessary changes in the standardization and its challenges. T2 - 46th Seminar - Additive Manufacturing, Hydrogen, Energy, Integrity CY - Online meeting DA - 12.10.2021 KW - Hydrogen KW - Joining process KW - Welding KW - Review KW - Research and Development PY - 2021 AN - OPUS4-53554 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - HEA Processing - SURDIA - Current R&D at BAM N2 - This presentation summarizes the latest results on the BAM-Themenfeld project SURDIA on processing of high-entropy alloys (HEAs) at BAM. At first, the influence of machining by ultrasonic-assisted milling on the surface integrity is presented. Second, the weld processing by Tungsten Inert Gas (TIG) welding is presented and the results of the Friction Stir Welding (FSW), which is conducted at BAM for the first time. T2 - DFG SSP 2006 - Subgroup meeting on the synthesis and processing of CCAs/HEAs CY - Online meeting DA - 08.10.2021 KW - High-entropy alloy KW - Ultrasonic-assisted milling KW - Welding KW - Processing KW - Surface integrity PY - 2021 AN - OPUS4-53497 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -