Enhanced strength and ductility of laser-directed energy deposition repaired IN718 superalloy via a novel tailored heat treatment

High-quality repair of damaged Inconel 718 (IN718) superalloy components can achieve great economic benefits. However, the directly double aging (DA) treatment by industrial standards, yields an inferior ductility on the repaired component than that of the wrought base metal. In this work, wrought IN718 components were repaired by laser-directed energy deposition (LDED), a novel tailored heat treatment (THT) schedule consisting of a short-term low-temperature homogenization, and subsequent DA was subsequently conducted to strengthen the repaired IN718 alloys. The microstructure evolution and mechanical properties of the DA and THT-treated repaired alloys were comparatively investigated. The results indicated that the THT effectively dissolved most of the hard brittle Laves precipitates in the deposition region with only slight coarsening of the grains in the substrate. As compared to the DA sample, the elongation of the THT sample increased remarkably by 88% with only a slight reduction of 19.2 MPa in yield stress. Moreover, the strain distribution of the THT sample was overall more even but then destabilized in a narrow abnormal coarsened grain region caused by the static recrystallization. In general, this study breaks through the limitation of the low ductility of the DA-treated repaired IN718 alloys and provides a promising way to further improve the mechanical properties.