Effect of post-heat treatment on the microstructure and mechanical properties of laser metal deposition Inconel 718

The microstructure, hardness, and fracture strength of Inconel 718 fabricated with laser metal deposition are investigated. The solution treatment plus aging (STA) (including 980 degrees C, 720 degrees C, and 620 degrees C for 1, 8, and 8 h, respectively) and low-temperature stress-relief annealing (LTSLA) (including 650 degrees C for 1 h) are compared, which can respectively improve the hardness and tensile properties. Results show that the as-deposited sample mainly contained gamma matrix, coarse Laves phase, granular carbides, and nitrides. STA and LTSLA post-heat treatments could respectively improve the hardness and tensile properties, while the elongation slightly decreased. The solution treatment promoted almost Laves phase to dissolve into gamma matrix and homogenized the matrix, and the aging treatment promoted the precipitation of gamma ' and gamma '' phases, which significantly improved the mechanical properties.