The effect of charging conditions on hydrogen embrittlement behavior of ultra-high-strength steel 22MnB5

The effect of charging conditions on hydrogen embrittlement (HE) of the hot-stamping boron steel was investigated with its hydrogen distributions and reversibility properties. With low hydrogen concentration, no noticeable hydrogen-induced cracking was detected, coupled with the uniform distributed diffusible hydrogen, realizing reversible HE. The quasi-cleavage fracture modes suggested the hydrogen-enhanced localized plasticity (HELP) mechanism. At high hydrogen concentration, the diffusible hydrogen distributed at the martensitic block and prior austenite grain boundaries which facilitated hydrogen-induced cracking initiation and propagated along the {110}M plane, leading to irreversible HE. The intergranular fracture modes suggested the transition of HELP to hydrogen-enhanced decohesion mechanism (HEDE).