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

The most important effect of hydrogen on the bulk diffusion of iron (a significant acceleration of diffusion) in pure BCC iron, ferritic steel and iron-chromium alloys was discovered for the first time in this project. An analytical interpretation of the observed phenomena is planned during the second (final) stage of the project. The influence of hydrogen on a significant slowdown in the grain-boundary diffusion of chromium in pure BCC iron, ferritic steel and iron-chromium alloys was revealed for the first time within the first stage of the project. This conclusion helps to understand the nature of corrosion mechanism in this group of corrosion-resistant materials. Study of the chemical diffusion in pure Fe, ferritic steels and FeCr alloys in environment of both argon and argon/hydrogen mixture is proposed as the final stage of investigation of the mass transfer mechanisms. Diffusion fluxes will be characterized and corresponding interdiffusion coefficients will be calculated. The microstructure evolution of the manufactured interdiffusion couples in the interdiffusion zone will be carefully studied. The pores in the weld joint (initial interface) will be characterized. It is also planned to conduct a series of corrosion tests simulating real operating conditions. All data will be systematized and the universal mechanism of the hydrogen influence on the diffusion and corrosion of iron, steel and iron-chromium alloys will be described. The proposed studies will help to explain the observed fundamental effects of hydrogen on the mass transfer and corrosion in the reported Fe-based materials. The described results allow to shed the light on the nature of the observed phenomena underlying catastrophic accidents and irreversible destruction of the considered iron-based materials after hydrogen exposure. The announced patterns provide a powerful incentive for the development of a new generation of materials with improved performance properties.

• DFG Programme: WBP Position