Solidification microstructure and elemental segregation in laser-based powder bed fusion additively manufactured IN738LC Ni-based superalloy

• The solidification microstructure in AM IN738LC Ni-based superalloy is investigated. • High laser power and high scan speed give the minimum defects in the as-built superalloy. • Dendrite impingement decreases undercooling, thereby lowering solute segregation. • The high laser power condition induces a low volume fraction of MC carbides. • The maximum strength with high ductility is observed by high laser power and high scan speed. We systematically investigate the solidification microstructure and elemental segregation in Inconel 738LC fabricated via laser-based powder bed fusion of metals (PBF-LB/M) under three representative process conditions. Microstructural characterizations confirm a strong correlation between thermal input, solidification behavior, and microstructural anisotropy. Within the conditions, the high laser power and scan speed result in low porosity, low micro-cracks, and minimum lack-of-fusion defects. A combination of three-dimensional finite element method (FEM) simulations and phase-field modeling (PFM) quantify the thermal gradients, cooling rates, and predicts dendritic growth behavior. Optimized high power and scan speed lead to a relatively low thermal gradient, which gives dendrite impingement. The dendrite impingement decreases undercooling, thereby lowering solute partitioning ratio between cell core and cell boundary. The high laser power condition induces a relatively low interface velocity with a larger tip radius, lowering solute segregation of γ’ forming elements based on the Gibbs-Thomson effect. Thus, the high laser power condition gives a relatively low volume fraction of MC carbides, possibly enhancing γ’ precipitation for strength during the post heat treatment process. This work provides new insights into the process-structure–property relationship in PBF-LB/M of IN738LC and establishes a modeling framework for predicting microstructure and segregation phenomena in Ni-based superalloy.