Fundamentals of hydrogen impact on diffusion of Cr and Fe in pure iron, ferrite steels and Fe-Cr alloy

• Applicant: Dr.-Ing. Olga Lukianova
• Subject Area: Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials ; Mechanical Properties of Metallic Materials and their Microstructural Origins ; Metallurgical, Thermal and Thermomechanical Treatment of Materials ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 505248157

There exist urgent fundamental and technological demands for rigorous determination of the impact of hydrogen on the bulk and grain boundary diffusion rates of Cr in modern FeCr-based ferritic steels. At the moment, there is no direct experimental proof of the hypothesis that hydrogen affects the rates of grain boundary diffusion in Fe alloys. The present project aims to answer these important and actual problems via thorough measurements of both, Fe and Cr diffusion rates in Fe-based model systems. Such a systematic study is possible only using the unique radiotracer technique available at the Institute of Materials Physics, WWÜ Münster. Pure iron (Fe), iron-chromium alloy (FeCr) and a ferritic stainless steel are selected as main objects for the proposed research to focus on the basic processes facilitating the hydrogen attack. Both volume and grain boundary diffusion rates of Cr and Fe will be measured under H2-free atmosphere and under H2 environment. The radiotracer technique will be used to provide direct and unambiguous understanding of the fundamental nature of thermodynamic and kinetic interactions of H atoms with Fe and Cr. Furthermore, the impact of carbon on these interactions will be evaluated. The results will be used to evaluate the impact of hydrogen on grain boundary energy in the materials under investigation. The kinetic measurements will be accompanied by a careful evaluation of the hydrogen impact on the mechanical properties of the alloys using nano-indentation measurements.A significant advance in the basic understanding of the physical nature of the hydrogen attack in ferritic steals is expected.

• DFG Programme: WBP Position