Evaluation of the ATI 718Plus repaired by laser metal deposition under heat treatment regimes: Microstructures, mechanical properties, and their heterogeneity

Laser metal deposition (LMD) is an attractive repaired technology for integral impellers and blades. After maintenance, the LMD usually generates an inhomogeneous microstructure joint consisting of two zones: repaired zone (RZ) is mainly composed of highly textured columnar dendrite and long striped Laves phases in the inter-dendrite, while the substrate zone (SZ) displayed equiaxed grains with rod-like η phases on grain boundaries. RZ is the limiting factor due to the absence of γ′ and the presence of Laves phase. Three specific heat treatment regimes, namely direct aging (DA), solution and aging (SA), and homogenization and aging (HA) were chosen to investigate the microstructure response of heat treatments including the grain size, Laves phase, η phase, and γ′ phase of RZ and SZ. After heat treatment, the mechanical compatibility was highly improved, and the global tensile properties were analyzed based on the microstructure evolution and respective tensile properties. The tensile properties of the DA and SA joint reached the same level of wrought ATI 718plus alloys, whereas the ductility is lower due to the inhomogeneous deformation. Comparatively, the HA sample showed higher ductility and lower strength due to abnormal grain growth.