Optimizing grain size in PBF-LB Inconel 939: a cost-effective approach using solution annealing, HIP, and integrated heat treatments for enhanced high-temperature performance

This work focuses on the Laser Powder Bed Fusion Additive Manufacturing (PBF-LB-AM) of a nickel-based superalloy, Inconel 939 (IN939), addressing one of the key limitations: the final grain size and texture of the produced sample. Controlling the grain size is particularly critical for IN939, commonly used in high-temperature applications, where equiaxed and coarse grains contribute to enhanced creep resistance. The study aims to achieve significant grain coarsening by entering the incipient melting region of the alloy during the solution annealing. This heat treatment ensures equiaxed microstructure, although it may induce some localized melting, considered a detrimental defect. However, the simultaneous application of Hot Isostatic Pressing (HIP) and heat treatment effectively promotes severe grain coarsening while preventing defect formation.