Low-energy proton implantation reveals the incipience of hydrogen embrittlement in a martensitic steel

Hydrogen embrittlement remains a critical challenge in steels, particularly as hydrogen gains importance as a clean energy carrier. Direct microstructural evidence of HE mechanisms is difficult to obtain due to the high mobility of hydrogen and the instability of crack propagation. In this study, we introduce a controlled experimental approach using low-energy proton implantation to locally introduce hydrogen into 22MnB5 press hardened steel. This technique, adapted from prior investigations in silicon, confines hydrogen-induced effects to a well-defined depth, enabling focused nano-scale analysis by transmission electron microscopy. The results reveal the nucleation of hydrogen-stabilized nano-cavities aligned in one-dimensional rafts, which subsequently coalesce into nano-cracks within the martensitic matrix. These findings provide direct experimental insight into the incipience of HE, supporting the synergistic action of hydrogen-enhanced localized plasticity and hydrogen-enhanced decohesion. The proposed methodology offers a promising route to systematically investigate the onset of hydrogen embrittlement in metallurgy with nanoscale resolution.