Development of methods for the alloy design of austenitic steels with a homogeneous deformation behavior and a high resistance against hydrogen embrittlement

• Applicant: Professor Dr.-Ing. Sebastian Weber
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins ; Computer-Aided Design of Materials and Simulation of Materials Behaviour from Atomic to Microscopic Scale
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 456380481

Previous research projects have examined the influence of the local stability of the fcc phase resulting from the solidification behavior of conventionally produced materials on the hydrogen embrittlement of metastable austenitic steels. It was found that the material response to deformation and the resulting local transformation of the fcc-phase into the martensitic bcc-phase significantly affected hydrogen embrittlement. With this knowledge, in the initial proposal, we were able to conduct computer-assisted automated optimization based on a conventional steel 1.4307 and a subsequent characterization. Additionally, the efforts focused on the influence of temperature on deformation-induced transformation of the fcc-phase, while cracks resulting from hydrogen embrittlement in a three-dimensional manner could be quantitatively analyzed. As preliminary work for the continuation project subject of this proposal, it was also possible to employ the methods developed during the first phase of the project to characterize microstructural inhomogeneities in parts produced by PBF-LB/M. These investigations serve as the basis, as microstructural defects may exert a significant impact on hydrogen trapping and, consequently, the hydrogen embrittlement of austenitic steels. This influence will be examined and quantified in the context of the project continuation, with a comparison of various manufacturing processes. To this end, the conventionally produced, optimized alloy developed in the initial proposal will be manufactured both by melting and powder metallurgy, followed by processing via HIP and PBF-LB/M and heat treatment. Using these different states, it will be possible, through homogeneity and interface analyses in correlation with hydrogen loading, thermal desorption spectroscopy, and low-temperature tensile testing, to draw conclusions about the influence of these manufacturing routes on hydrogen trapping and hydrogen embrittlement of metastable austenitic steels. Based on these findings, in the final step of the proposal, the chemical composition of the alloy optimized for conventional manufacturing will be further adapted in terms of an “alloy design for AM”.

• DFG Programme: Research Grants