Embrittlement mechanisms of high-strength steel for hydrogen injectors under sequential hydrogen exposure and cyclic impact

While hydrogen internal combustion engines are pivotal for achieving carbon neutrality, critical injector components are acutely susceptible to premature brittle fracture induced by the synergistic effects of cyclic impact fatigue and hydrogen degradation. To date, the underlying embrittlement mechanisms remain poorly understood. This study systematically investigates the dynamic impact damage mechanisms of high-strength steel following pre-exposure to an extreme high-temperature and high-pressure hydrogen environment. The results reveal that prior hydrogen exposure induces a profound brittle transition. At the crystallographic level, hydrogen severely restricts lattice deformation and accelerates the dynamic micro-fragmentation process under cyclic impact. Crucially, a mechano-chemical vicious synergy is identified: the profound micromechanical plasticity constraint synergizes with severe tribo-chemical oxidation, thereby drastically diminishing the capacity of material for ductile energy dissipation. This work fundamentally elucidates the embrittlement mechanisms of high-strength steel under sequential hydrogen-impact conditions, providing theoretical guidance for enhancing the durability of dynamic components in hydrogen energy systems.