The influence of solution temperature on microstructure evolution and mechanical properties of ATI 718Plus repaired by wire and arc additive manufacturing

Wire and arc additive manufacturing technology was applied to repair damaged 718Plus components to save life -cycle costs. In this work, the effects of different solution temperatures on the microstructural evolution and tensile properties of repaired samples were investigated in detail. The results showed that the heat-treated microstructure in the deposited zone (DZ) mainly consisted of columnar grains along the building direction. Laves phase, needle-like i phase and gamma' phase were gathered in the interdendritic region. In contrast, the microstructure of the substrate zone (SZ) contained equiaxed grains with grain boundary (GB) eta phase and a uniform distribution of gamma' phase. With the solution temperature increasing, the undesirable Laves phase was gradually dissolved, and its morphology varied from long-striped to granular. The number of i phases was observed to increase initially and then decrease with morphology changing to granular. The resultant granular i phase in SZ lost its pinning effect on GBs, leading to the rapid coarsening of grains in SZ. Tensile tests show that the dissolution of Laves phase and i phase in DZ helps to improve the ductility while the grain growth results in the decrease of tensile stress.