Forming quality, microstructure, and ductility-oriented mechanical performance of laser powder bed fusion processed Ni-based superalloy using different thermal input modes

Thermal input modes significantly affect forming quality, microstructure, and mechanical properties of components fabricated by laser powder bed fusion (LPBF). However, their influence on GH4169 Ni-based superalloy remains inadequately characterized. This study systematically investigates five thermal input modes—sub-area distributed, continuous repeated, long-range quasi-steady, closed-loop cyclical, and strip-based linear—for fabricating GH4169 using LPBF. The continuous repeated mode yielded the lowest surface roughness ( Sa = 12.33 μm), while the closed-loop cyclical mode exhibited the highest ( Sa = 38.80 μm). Enhanced densification and microstructural homogeneity were observed under continuous repeated and strip-based linear modes, whereas significant defects and irregular melt pool boundaries were noted with the closed-loop cyclical mode. Although nano-hardness and elastic modulus values were similar across all modes, the long-range quasi-steady and closed-loop cyclical modes demonstrated higher Vickers hardness. Tensile testing at room temperature and 650 °C (the operational temperature for GH4169) revealed marked differences in ductility but minor strength variations. Specifically, long-range quasi-steady and closed-loop cyclical modes showed reduced ductility due to microstructural defects, whereas sub-area distributed and strip-based linear modes achieved superior elongation. Overall, strip-based linear modes provided optimal balance between forming quality, mechanical performance, and processing efficiency. These findings underscore the importance of thermal input mode selection in controlling microstructural evolution and ductility-oriented mechanical performance in LPBF-fabricated GH4169 components, offering valuable insights for additive manufacturing of Ni-based superalloys.