Additive Manufacturing and Post Processing of Alloy 22 by Laser Powder Bed Fusion

Abstract A nickel-based superalloy (Alloy 22) powder was gas atomized to be used as a feedstock in the Laser Powder Bed Fusion (L-PBF) process. In this study, laser power and scanning speed were optimized to manufacture parts with the highest density. Samples manufactured with power of 150 W and scanning speed of 200 mm/s showed the highest relative density of 99.6%. Additionally, for a higher production rate, samples were manufactured with power of 225 W and scanning speed of 1200 mm/s. Additively manufactured parts were post processed by conducting solution heat treatment, hot isostatic pressing (HIP), and HIP+solution heat treatments. HIP effectively eliminated most of the defects in the as-printed samples, but Mo-rich ultrafine precipitates were observed in HIP processed samples. Solution heat treatment led to full recrystallization and the total dissolution of the Mo-rich second phases into the Ni matrix. The role of solution treatment on enhancing ductility of HIPPed sample was found significant. Sample manufactured at 150 W and 200 mm/s followed by HIP and solution treatment showed similar mechanical properties to wrought Alloy 22.