Research on hydrogen embrittlement behavior of L-PBF 18Ni(300) maraging steel by experiments and numerical simulations

Affected by complex microstructural evolution, dominant factors in hydrogen embrittlement (HE) of maraging steels in different aging states were not clear. This fundamental issue was clarified systematically by experiments and numerical simulations in this work. In under-aged and peak-aged states, diffuse coherent ω/matrix interfaces and sharp semi-coherent η-Ni ₃ Ti/matrix interfaces acted as reversible traps, respectively. Their different interfacial properties determined the differences in trap density in the two states. The lowest trap density led to the fastest hydrogen diffusion and the highest hydrogen content in lattice, causing the worst HE in under-aged state. In peak-aged state, the situation was relieved by the highest trap density. In over-aged state, the newly formed Laves-Fe ₂Mo/matrix interfaces acted as slightly deeper traps compared with the η-Ni ₃ Ti/matrix interfaces, but the reduction in interfacial area decreased trap density and accelerated hydrogen diffusion instead. Even so, the improvement in ductility by reverted austenite further relieved HE susceptibility in this state.