This study investigated the influences of microstructural evolution on the hydrogen embrittlement (HE) behaviors of selective laser-melted (SLM) 718 alloys during typical solution treatments. The hydrogen trapping behaviors of the dendrite structure, Laves and δ phases were effectively confirmed. Results indicate that hydrogen-induced fracture of brittle precipitates (Laves and δ phases), along with debonding at phase interfaces, contributes to the development of extensive micropores and microcrack. Dendrite walls with high-density entangled dislocations function as effective hydrogen traps, substantially suppressing the diffusion of hydrogen into matrix, and lowering the accumulated hydrogen content in the alloy after 24 h of hydrogen charging. A short-time solution treatment at 980 °C for 10 min effectively inhibits almost δ phase precipitation while retaining dislocation-rich dendritic substructures, achieving a remarkable reduction in HE susceptibility to 7.8 %. • The microstructure evolutions of SLM-718 alloy during solution treatment were analyzed; • The hydrogen trapping behaviors of the dendrite structures and δ phase were obtained; • The influences of Laves and δ phases on the hydrogen-assisted cracking were analyzed; • A lowest HE sensitivity of 7.77% was achieved by solution treatment at 980 °C for 10 min.
Zhao et al. (Sun,) studied this question.