Synergistic hydrogen embrittlement in high-strength steels

Hydrogen embrittlement (HE) remains a critical scientific challenge in building reliable infrastructure for a carbon-free hydrogen economy. Predictive models for hydrogen-induced material failure are still lacking, largely due to an incomplete understanding of hydrogen's effects on deformation behavior, especially in multiphase alloys with complex compositions and microstructures. Here, we demonstrate a synergistic hydrogen embrittlement (SHE) phenomenon in high-strength martensitic steels, where hydrogen interacts with carbon in solution to activate hydrogen-enhanced localized plasticity (HELP). Microcantilever bending tests revealed greater hydrogen susceptibility with higher carbon content, evidenced by a significant reduction in work-hardening capacity, promoting slip localization and reduced ductility. First-principles calculations and theoretical modeling revealed that carbon intensifies hydrogen-dislocation interactions and amplifies hydrogen redistribution around screw dislocations, inhibiting cross-slip. This work integrates experimental and modeling approaches to elucidate the synergistic interactions between hydrogen and solute elements, providing critical insights for designing high-strength, hydrogen-tolerant structural materials.