Microstructure evolution and mechanical properties of wire-fed electron beam directed energy deposition repaired GH4169 superalloy

Abstract

In this paper, the microstructural evolution and failure behavior of GH4169 superalloy repaired using wire-fed electron beam directed energy deposition (EB-DED) are investigated in detail. Results show that in the deposited zone (DZ), the Laves phase is formed in the interdendritic zone, and the γ'' phase and γ′ phase precipitate around the Laves phase and are distributed gradiently along the building direction. In contrast, the substrate zone (SZ) is composed of fine equiaxed grains and uniform distributed γ'' and γ′ phases. Direct aging heat treatment cannot effectively dissolve the Laves phase, but can further precipitate the γ'' and γ′ phases, resulting in an increase in yield strength and ultimate tensile strength and a decrease in elongation. During the plastic deformation process, dislocation activity preferentially occurs in the γ matrix and forms accumulation at the Laves/γ interface, leading to the formation of cracks in the DZ, so that all tensile samples fail in the DZ. In addition, this study further elucidates the fracture mechanism of the Laves phase within grains and at grain boundaries.