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 °C, 720 °C, and 620 °C for 1, 8, and 8 h, respectively) and low-temperature stress-relief annealing (LTSLA) (including 650 °C for 1 h) are compared, which can respectively improve the hardness and tensile properties. Results show that the as-deposited sample mainly contained γ 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 γ matrix and homogenized the matrix, and the aging treatment promoted the precipitation of γ′ and γ″ phases, which significantly improved the mechanical properties. [ABSTRACT FROM AUTHOR]