Abstract
Additive manufacturing of superalloys has significant merits as it produces components with higher complexity and less post-machining. Inconel 718 (IN718) is a well-known high-strength nickel alloy that can be manufactured using laser powder bed fusion (LPBF). During the LPBF process, the thermal gradient and solidification rates vary, resulting in various solidification conditions and microstructures. This study aims to investigate the microstructural characteristics of IN718 manufactured by LPBF, including grain size and orientation. The presented work developed post heat treatment procedures to enhance the mechanical properties of fabricated IN718 and minimize anisotropy associated with the as-built conditions. Three different heat treatments with varying times and temperature ranges were investigated, followed by standard aging in IN718 samples fabricated in the X and Z orientations to homogenize the microstructure. Digital light microscope, X-Ray Diffraction (XRD), and hardness tests were used to characterize the microstructure of additively fabricated IN718. Results indicated that the heat treatment at 980°C improved the hardness. An additional increase in heat treatment temperature increased grain size and undesirable precipitates.
