Effect of Aging Parameters on Inconel 718 Fabricated by Laser Directed Energy Deposition

Inconel 718 is a nickel-based superalloy of high interest in high temperature applications such as turbine parts. To be used in such applications, heat treatments are commonly applied to dissolute Laves phase and to achieve γ′′ phase. However, conventional heat treatment methods for wrought Inconel 718 may not be suitable for Inconel 718 fabricated by laser directed energy deposition (LDED) due to its unique microstructure formed during the rapid solidification process. There has been a lack of investigation in heat treatments for Inconel 718 fabricated by this process, specifically around the impact of aging parameters on this alloy. In this study, the effects of aging parameters were studied by performing seven different heat treatments, including solutionising and aging treatments. Our results indicate that for LDED Inconel 718, a high temperature solution treatment of 1100 ℃ for 1 h followed by single aging at 650 ℃ for 20 h achieved a tensile strength and elongation of 1247 MPa and 23%, respectively. Further, results indicated that even with a shorter aging time of 10 h, γ′′ phase was found to be of comparable size to the standard double aged treatment.