Enhancing hydrogen embrittlement resistance in high-strength martensitic steels via tailoring variant selection at prior austenite grain boundaries

This study presents a thermomechanical processing strategy to improve the resistance to hydrogen embrittlement (HE) in martensitic steels through controlling variant selection at prior austenite grain boundaries (PAGBs), while retaining ultrahigh tensile strength (>1.5 GPa). Under identical hydrogen-charging conditions, the 10% hot-compressed specimen exhibited the highest HE resistance, correlating with its largest fraction of low-angle PAGB segments. Misorientation-distribution analysis and tensile tests revealed a non-monotonic dependence of compressive strain: an optimal compressive level maximized the beneficial stress-assisted variant selection at PAGBs, whereas excessive strains promoted self-accommodation of transformation strain in the work-hardened austenite, diminishing the beneficial effect. The improved HE resistance stems from reduced hydrogen trapping, enhanced strain-dissipating slip transfer, and increased cohesive energy at PAGBs. Tailoring variant selection at PAGBs through this simple process thus provides an industry-feasible route to hydrogen-resistant high-strength martensitic steels.