TY - CONF A1 - Schröder, Jakob T1 - Diffraction and Single-Crystal Elastic Constants of Laser Powder Bed Fused Inconel 718 N2 - In this presentation, the results of the determination of the diffraction and single-crystal elastic constants of laser powder bed fused Inconel 718 are presented. The analysis is based on high-energy synchrotron diffraction experiments performed at the Deutsches Elektronen-Synchrotron. It is shown that the characteristic microstructure of laser powder bed fused Inconel 718 impacts the elastic anisotropy and therefore the diffraction and single-crystal elastic constants. Finally, the consequences on the diffraction-based residual stress determination of laser powder bed fused Inconel 718 are discussed. T2 - AWT-Fachausschuss 13 "Eigenspannungen" CY - Wolfsburg, Germany DA - 19.03.2024 KW - Additive Manufacturing KW - Laser Powder Bed fusion KW - Diffraction KW - In-Situ Testing KW - Diffraction Elastic Constants PY - 2024 AN - OPUS4-59900 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröder, Jakob T1 - Influence of Microstructure on the Diffraction-Based Residual Stress Determination in Laser Powder Bed Fused Inconel 718 N2 - Additive manufacturing processes such as laser powder bed fusion (PBF-LB) offer the ability to produce parts in a single manufacturing step. On the one hand, this manufacturing technique offers immense geometric freedom in part design due to its layer-by-layer manufacturing strategy. On the other hand, the localized melting and solidification impose the presence of large temperature gradients in the process. From a microstructural perspective, this inevitably results in micro-segregation and a columnar grain structure, often paired with a significant crystallographic texture. Even worse, these large temperature gradients can lead to internal stress-induced deformation or cracking during processing. At the very least, residual stress is retained in the final structures as a footprint of this internal stress. In this context, diffraction-based methods allow the non-destructive characterization of the residual stress field in a non-destructive fashion. However, the accuracy of these methods is directly related to the microstructural characteristics of the material of interest. First, diffraction-based methods access microscopic lattice strains. To relate these lattice strains to a macroscopic stress, so-called diffraction elastic constants must be known. The deformation behavior is directly linked to the microstructure. Therefore, the diffraction elastic constants also depend on the microstructure. Second, the presence of crystallographic texture should be considered in the residual stress determination, as variations in crystal orientations contribute differently to the diffraction signal. Here we present the influence of the microstructure on the determination of residual stress by diffraction-based methods in as-built PBF-LB Inconel 718 parts. We obtained different microstructures by employing two different scanning strategies. In particular, different crystallographic textures were obtained by changing the relative angle of the scan vectors to the geometric axes of the part. The texture-based characterization of the residual stress field was carried out by surface, sub-surface, and bulk residual stress measurements. It was found that the residual stress determination significantly depends on the microstructure for strong crystallographic textures. T2 - Material Science and Engineering Congress CY - Darmstadt, Germany DA - 24.09.2024 KW - Additive Manufacturing KW - Electron Backscatter Diffraction KW - Microstructure KW - Residual Stress KW - X-ray Diffraction PY - 2024 AN - OPUS4-61475 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Waske, Anja T1 - A unique authenticator for additively manufactured parts derived from their microstructure N2 - In the field of additive manufacturing, the ability to uniquely identify and authenticate parts is crucial for certification, logistics, and anti-counterfeiting efforts. This study introduces a novel methodology that leverages the intrinsic microstructural features of additively manufactured components for their identification, authentication, and traceability. Unlike traditional tagging methods, such as embedding QR codes on the surface [1] or within the volume of parts, this approach requires no alteration to the printing process, as it utilizes naturally occurring microstructural characteristics. The proposed workflow [2] involves the analysis of 3D micro-computed tomography data to identify specific voids that meet predefined identification criteria. This method is demonstrated on a batch of 20 parts manufactured with identical process parameters, proving capable of achieving unambiguous identification and authentication. By establishing a tamper-proof link between the physical part and its digital counterpart, this methodology effectively bridges the physical and digital realms. This not only enhances the traceability of additively manufactured parts but also provides a robust tool for integrating digital materials, parts databases, and product passports with their physical counterparts. T2 - Artificial Intelligence in MSE CY - Bochum, Germany DA - 18.11.2025 KW - Authentication KW - Additive Manufacturing KW - Non-destructive testing PY - 2025 AN - OPUS4-65204 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Nietzke, Jonathan T1 - Performance of Conventional and Additive Manufactured Austenitic Stainless Steels under Gaseous Hydrogen Environment using in-situ Hollow Specimen Technique N2 - Hydrogen and its derivatives (e.g. ammonia) are considered as a suitable energy carrier in the future supply of renewable energy. Hydrogen transportation systems require pipes, valves and fittings, among other components. In this sense, austenitic stainless steels are commonly used structural materials for pure hydrogen applications. Stable austenitic alloys, like AISI 316L, are often assumed to be practically unsusceptible to hydrogen embrittlement. At the same time, a number of studies show the influence of hydrogen even in 316L under some circumstances. Some other studies state that this embrittlement could be avoided by using steel grades with a higher nickel equivalent which contributes to a more stable austenitic phase. Nonetheless, 316L is widely used in hydrogen atmospheres since many years because of lower costs and positive practical experience. For these reasons, not only 316L but also 304 could be further utilized by identifying the exact constraints. With increasing demand for components regarding hydrogen applications, additive manufacturing technologies are getting increasingly important complementary to conventional manufacturing. In the context of additive manufacturing, 316L is a common material as well. The manufacturing process offers great advantages due to higher freedoms in design and the possibility for customized components in small batches. For example, valves with improved flow characteristics and reduced component weight can be produced. Nevertheless, there is still lack of experience and experimental results concerning additively manufactured parts under hydrogen service. Therefore, the influence on the material properties for additively manufactured parts in hydrogen environments needs to be further investigated. In the present work, slow strain rate testing (SSRT) has been applied using hollow specimens. This testing procedure allows to perform practicable and faster in-situ tests in comparison to tests in autoclaves and investigate the influence of hydrogen on the mechanical properties. Conventional AISI 304 and 316L specimens as well as additively manufactured 316L specimens were tested at room temperature and a pressure of 200 bar. Elongation at fracture and relative reduction of area (RRA) have been used to evaluate the influence of hydrogen. It is shown that the influence of hydrogen is more pronounced in 304 than in 316L. Furthermore, potentially influencing factors such as surface roughness, microstructure and porosity are discussed. T2 - International Hydrogen Conference CY - Park City, Utah, USA DA - 17.09.2023 KW - Hydrogen KW - Hollow Specimen Technique KW - Additive Manufacturing KW - Austenitic Steels PY - 2023 AN - OPUS4-58776 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yu, C.-H. T1 - Distribution of subsurface residual stress as a function of wall thickness in stainless steel 316L LPBF structures N2 - The subsurface residual stress in laser powder bed fused 316L structures was analyzed using X-ray diffraction (XRD) and layer removal. The influence of varying structure thicknesses was investigated. In this study the importance of combining surface roughness measurements with XRD was shown. Moreover, a clear relation between the structure thickness and the subsurface residual stress profiles was observed. T2 - The 11th International Conference on Residual Stress CY - Nancy, Frankreich DA - 28.03.2022 KW - AGIL KW - Residual Stress KW - X-ray Diffraction KW - Additive Manufacturing PY - 2022 AN - OPUS4-54581 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sprengel, Maximilian A1 - Mohr, Gunther A1 - Altenburg, Simon A1 - Evans, Alexander A1 - Serrano-Munoz, Itziar A1 - Kromm, Arne A1 - Pirling, T. A1 - Bruno, Giovanni A1 - Kannengießer, Thomas T1 - Triaxial Residual Stress in Laser Powder Bed Fused 316L: Effects of Interlayer Time and Scanning Velocity N2 - The triaxial distribution of the residual stress in laser powder bed fused austenitic steel 316L was determined by X-ray and neutron diffraction. The residual stress analysis results were linked to the thermal history of the specimens, which were manufactured with varying inter-layer-times and scanning velocities. A clear link between the in-process temperature of the specimens and the residual stress was found, based on in-situ monitoring data. KW - Stainless Steel KW - AGIL KW - Residual Stress KW - X-ray and Neutron Diffraction KW - Additive Manufacturing PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-542620 DO - https://doi.org/10.1002/adem.202101330 SP - 1 EP - 13 PB - Wiley-VCH GmbH AN - OPUS4-54262 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ulbricht, Alexander A1 - Ávila Calderón, Luis A1 - Sommer, Konstantin A1 - Mohr, Gunther A1 - Evans, Alexander A1 - Skrotzki, Birgit A1 - Bruno, Giovanni T1 - Evolution of Creep Damage of 316L Produced by Laser Powder Bed Fusion N2 - The damage mechanisms of metallic components produced by process laser powder bed fusion differ significantly from those typically observed in conventionally manufactured variants of the same alloy. This is due to the unique microstructures of additively manufactured materials. Herein, the focus is on the study of the evolution of creep damage in stainless steel 316L specimens produced by laser powder bed fusion. X-ray computed tomography is used to unravel the influence of the process-specific microstructure from the influence of the initial void distribution on creep damage mechanisms. The void distribution of two specimens tested at 600 °C and 650 °C is analyzed before a creep test, after an interruption, and after fracture. The results indicate that the formation of damage is not connected to the initial void distribution. Instead, damage accumulation at grain boundaries resulting from intergranular cracking is observed. KW - Creep KW - Computed Tomography KW - PBF-LB/M/316L KW - Laser Powder Bed Fusion KW - Microstructure KW - AISI 316L KW - Additive Manufacturing PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-574127 DO - https://doi.org/10.1002/adem.202201581 SP - 1 EP - 9 PB - Wiley-VCH GmbH CY - Weinheim AN - OPUS4-57412 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sprengel, Maximilian T1 - Surface and bulk residual stress in laser powder bed fused 316L: Influence of inter layer time and scanning velocity N2 - The influence of the inter-layer-time and the scanning velocity on the surface and bulk residual stress in laser powder bed fused 316L specimens was investigated. This study combines X-ray and neutron diffraction results with the thermal history of the specimens acquired through in-situ process monitoring. The process parameter variations were observed to directly influence the thermal history, which gave new insights in the assessment of the residual stress results. T2 - The 11th International Conference on Residual Stress CY - Nancy, Frankreich DA - 28.03.2022 KW - AGIL KW - Residual Stress KW - X-ray and Neutron Diffraction KW - Additive Manufacturing KW - Stainless Steel PY - 2022 AN - OPUS4-54582 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ávila Calderón, Luis A1 - Rehmer, Birgit A1 - Schriever, Sina A1 - Ulbricht, Alexander A1 - Agudo Jácome, Leonardo A1 - Sommer, Konstantin A1 - Mohr, Gunther A1 - Skrotzki, Birgit A1 - Evans, Alexander T1 - Creep and creep damage behavior of stainless steel 316L manufactured by laser powder bed fusion N2 - This study presents a thorough characterization of the creep properties of austenitic stainless steel 316L produced by laser powder bed fusion (LPBF 316L) contributing to the sparse available data to date. Experimental results (mechanical tests, microscopy, X-ray computed tomography) concerning the creep deformation and damage mechanisms are presented and discussed. The tested LPBF material exhibits a low defect population, which allows for the isolation and improved understanding of the effect of other typical aspects of an LPBF microstructure on the creep behavior. As a benchmark to assess the material properties of the LPBF 316L, a conventionally manufactured variant of 316L was also tested. To characterize the creep properties, hot tensile tests and constant force creep tests at 600 °C and 650 °C are performed. The creep stress exponents of the LPBF material are smaller than that of the conventional variant. The primary and secondary creep stages and the times to rupture of the LPBF material are shorter than the hot rolled 316L. Overall the creep damage is more extensive in the LPBF material. The creep damage of the LPBF material is overall mainly intergranular. It is presumably caused and accelerated by both the appearance of precipitates at the grain boundaries and the unfavorable orientation of the grain boundaries. Neither the melt pool boundaries nor entrapped gas pores show a significant influence on the creep damage mechanism. KW - 316L KW - Laser Powder Bed Fusion (LPBF) KW - Creep behavior KW - Additive Manufacturing KW - AGIL PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-539373 DO - https://doi.org/10.1016/j.msea.2021.142223 SN - 0921-5093 VL - 830 SP - 142223 PB - Elsevier B.V. AN - OPUS4-53937 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröder, Jakob A1 - Fritsch, Tobias A1 - Luzin, Vladimir A1 - Ferrari, Bruno A1 - Simón-Muzás, Juan A1 - Evans, Alexander A1 - Bruno, Giovanni T1 - Impact of scan strategy on principal stresses in laser powder bed fusion N2 - Additive manufacturing techniques, such as laser powder bed fusion (PBF-LB), are well known for their exceptional freedom in part design. However, these techniques are also characterized by the development of large thermal gradients during production and thus residual stress (RS) formation in produced parts. In this context, neutron diffraction enables the non-destructive characterization of the bulk RS distribution. By control of the thermal gradients in the powder-bed plane by scan strategy variation we study the impact of in-process scan strategy variations on the microstructure and the three-dimensional distribution of RS. Microstructural analysis by means of electron backscatter diffraction reveals sharp microstructure transitions at the interfaces ranging from 100-200 µm. The components of the RS tensor are determined by means of neutron diffraction and the principal stress directions and magnitudes are determined by eigenvalue decomposition. We find that the distribution of RS in the powder-bed plane corresponds to the underlying scan strategy. When the alternating scan vectors align with the x- and y sample coordinate axes, the principal stress directions co-align. In the present geometry, nearly transverse isotropic stress states develop when the scan vectors are either aligned 45° between x and y or continuously rotated by 67° between each layer. KW - Additive Manufacturing KW - Laser Powder Bed Fusion KW - Electron Backscatter Diffraction KW - Neutron Diffraction KW - Residual Stress KW - Principal Stress PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-607910 DO - https://doi.org/10.1016/j.matdes.2024.113171 SN - 0264-1275 VL - 244 SP - 1 EP - 10 PB - Elsevier Ltd. AN - OPUS4-60791 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -