As-Built and Post-treated Microstructures of an Electron Beam Melting (EBM) Produced Nickel-Based Superalloy

The microstructures of an electron beam melted (EBM) nickel-based superalloy (Alloy 718) were examined in both as-built and post-treated conditions, focusing on the contour and hatch regions of the build. Both regions exhibited similar hardness and carbide content, but the contour region had a higher density of fine carbides. Post-treatments, such as hot isostatic pressing (HIP) and HIP plus heat treatment (HIP + HT), significantly reduced defect content in both regions. Grain coarsening occurred in the contour region after HIP + HT. Various factors contributing to grain growth were discussed, and carbide sizes became more similar after post-treatment. Additionally, both regions showed increased hardness after HIP + HT compared to the as-built material.