Interdisciplinary study on degradation of material strength due to high-temperature hydrogen for safety of advanced high-temperature hydrogen technologies

• Applicants: Professor Dr. Reiner Kirchheim; Professorin Dr. Cynthia A. Volkert
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins ; Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 514742965

Understanding and controlling the effect of hydrogen on materials is a necessary step toward achieving a carbon-neutral and sustainable future. Structural materials such as Fe- and Ni-based alloys will play a central role in hydrogen generation, storage, transport, and end-use. Hydrogen-induced degradation of these materials at room temperature (hydrogen embrittlement), which poses a serious reliability threat to energy infrastructure, has been extensively studied. The resultant understanding is that room temperature embrittlement is driven either by hydrogen enhanced localized plasticity or hydrogen induced decohesion. On the other hand, very little is known about how hydrogen affects the mechanical behavior of structural alloys at elevated temperatures, for example, at the operating temperatures (>500°C) of Solid Oxide Electrolysis Cells (SOEC) and Solid Oxide Fuel Cells (SOFC) for hydrogen and power generation. Recent studies at macroscopic component level reveal that 600°C hydrogen accelerates creep deformation, but the underlying mechanisms are not understood.The focus of the proposed research is to explore and understand the macroscopic response of materials at high temperatures (>500°C) in terms of atomic level hydrogen interactions with microstructural defects such as vacancies, dislocations, and grain boundaries. These studies are important to develop a mechanistic understanding of the creep behavior of stainless steels that are used in the design of SOECs and SOFCs. The ultimate goal of the project is to develop macroscopic constitutive laws for the creep response of 304 and 310 stainless steels on the basis of defect-level understanding of the effect of hydrogen on dislocation plasticity that can be used in the analysis and design of SOEC and SOFC components against failure.Toward this goal we will use a scale bridging approach consisting of (i) high temperature macro-scale creep testing under gas environment to obtain quantitative information about how creep strain rates depend on hydrogen and microstructure, (ii) in-situ TEM mechanical tests with and without in-situ hydrogen loading to directly observe how hydrogen effects the defects involved in creep, (iii) physical-based kinetics modeling to relate the defect kinetics with creep strain rates and to predict the role of deformation and microstructure on hydrogen degradation, and (iv) from this mechanistic understanding, identification of the processes which must be inhibited to reduce damage.

• DFG Programme: Research Grants
• International Connection: Japan
• Co-Investigator: Lin Tian, Ph.D.
• Cooperation Partners: Professor Masanobu Kubota; Professor Petros Sofronis