Hydrogen embrittlement (HE) remains a significant challenge for metallic materials when exposed to hydrogen environment. The diffusable hydrogen atoms in the metal can cause interaction with microstructural features which results in a marked decrease in ductility and/or toughness. Literature studies have shown that microstructural features in different alloys can have significant effect on the hydrogen diffusion and thus alloy’s susceptibility to HE. Desinging a microstructure containing favored features (e.g. FCC phases, coherent precipitation, etc.) can hold great potential for improved performance under hydrogen environments.

The aim of this study is to provide an insight for designing alloys that are resistant to HE. Accordingly, our approach was to activate multiple mechanisms against HE: i) design a bulk microstructure that provides more trapping sites for Hydrogen, against HE, ii) reduce and Hydrogen uptake to the material by forming an in-situ and continuous oxide layer on the surface. In addition to conventional computational thermodynamics (CALPHAD), the concept of high entropy alloys or multi-principal element alloys was employed for alloy design, using the related empirical models.

Based on a literature study, and using high-throughput CALPHAD screening, two Fe-based alloys were designed and experimentally processed/characterized.

Metal casting (Vac. Induction melting/casting), rolling, and heat treatment was used as the processing methods. Microscopy evaluation confirmed the desired microstructure that is expected to have high resistant to HE based on the literature. Formation of in-situ oxide was studied using Thermo-Gravimetry-Analysis (TGA) method. Preliminary testing confirmed that FCC (austenitic) Fe-based alloys with the least amount of secondary phases could posses high resistant to HE. Tensile testing was conducted to benchmark the mechanical properties of the alloys.