Microstructural Evolution and Mechanical Properties of Post-Processed IN 625 Fabricated by Laser Powder Bed Fusion

ABSTRACT: Laser powder bed fusion (LPBF) is widely used for manufacturing nickel-based superalloy components with complex geometries; however, the process produces non-equilibrium microstructures characterized by directional grain growth, cellular substructures, and compositional segregation, which can lead to anisotropic mechanical behavior. In this study, the influence of multiple post-processing heat-treatment routes on the microstructural evolution and mechanical properties of LPBF-fabricated Inconel 625 (IN625) was systematically investigated by combining stress relief, hot isostatic pressing (HIP), and solution annealing. Microstructural characterization was performed using optical microscopy and scanning electron microscopy, while tensile properties were evaluated from room temperature to 700 °C. The HT3 condition resulted in a fully recrystallized, equiaxed grain structure with reduced segregation and minimal Nb-rich Laves phase, leading to nearly isotropic mechanical properties, with an ultimate tensile strength of approximately 880 MPa and an elongation exceeding 50%. Elevated-temperature testing demonstrated stable mechanical performance, with a localized strengthening effect near 600 °C attributed to dynamic strain aging. These results demonstrate that appropriate post-processing can effectively homogenize LPBF IN625 and improve its mechanical reliability.