Effect of heat treatment on microstructural evolution of additively manufactured Inconel 718 and cast alloy

Additive manufacturing (AM) processes facilitate the fabrication of complex shape metallic components directly from Computer-Aided Design models, which may be challenging to be produced using conventional manufacturing technologies. However, it is revealed that additively manufactured components usually have non-equilibrium microstructures. Thus, post-built heat treatments are recommended for AM components to achieve homogenous microstructures. In this study, the effects of solution annealing and ageing treatments on the microstructure evolution of Inconel 718 alloy processed by laser powder bed fusion (LPBF) and directed energy deposition (DED) processes are compared with those produced by casting. Microstructural characterization techniques including OM, SEM/EDS analysis were employed on AM and cast components to obtain more information regarding the microstructure and phase evolution during these heat treatments. These microstructural studies demonstrate that the starting microstructure could play a key role in the microstructural evolution during the heat treatment of Inconel 718 alloy.