Synergistic regulation of dendrite structure and δ phase for alleviating hydrogen embrittlement in selective laser-melted 718 alloy

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 %.