Microstructure and Mechanical Properties of IN738C Superalloy Fabricated by Laser Powder Bed Fusion

IN738C is a widely utilized precipitation hardening nickel-based superalloy known for its excellent mechanical properties in various industries. Laser powder bed fusion (LPBF) has emerged as a highly advantageous additive manufacturing process for fabricating complex-shaped parts using metal powders. This study investigates the influence of process parameters, specifically the scanning speed and hatch spacing, on the defect formation in LPBF-manufactured IN738C alloy. Additionally, the microstructure of heat-treated IN738C samples is examined, and their mechanical properties are evaluated through ambient tensile testing. The results indicate that LPBF-produced IN738C alloy exhibits the highest density when using a hatch spacing of 90 μm and a scanning speed of 750 mm/s. Upon heat treatment, cracks within the material propagated. Microscopic analysis of the heat-treated specimens reveals the presence of precipitated carbides and the 03B3′ phase, with continuous carbides observed along the grain boundaries. The as-built (AB) specimens exhibit a medium result in ultimate tensile strength (UTS), yield strength (YS), and elongation. However, the heat-treated (HT) specimens fail prior to yielding, exhibiting a lower result in UTS and elongation than AB specimens.