Laser Powder Bed Fusion of Inconel® 625: Guidelines for Robust Parameter Selection Toward Optimal Quality Parts

Producing INCONEL® 625 (IN625) components by laser powder bed fusion (PBF-LB) demands a careful selection of process parameters to concurrently ensure high densification, stable microstructural features, and adequate surface integrity. Previous studies investigated the isolated effect of these parameters or narrow volumetric energy density (VED) ranges, albeit without offering indications on how to simultaneously optimize surface roughness, microhardness, and density. Furthermore, the validity of VED as an input for process optimization is still debated. The present study offers a systematic exploration of the laser power–scan speed (P–v) space over a wide VED interval (33–400 J/mm³) to identify stable and robust process regimes for PBF-LB of IN625. Cylindrical samples built according to dissimilar P–v combinations reveal an extended process window where the properties of interest remain well balanced. Within this region, surface roughness below 10 μm, microhardness near 300 HV1, and relative density over 99.5% were consistently achieved. Furthermore, distinct P–v combinations sharing the same VED value were confirmed to produce markedly different results, underscoring the limitations of VED as a predictive descriptor. The findings allowed to establish quantitative guidelines for selecting robust P–v conditions, offering a practical foundation for future data-driven or physics-informed multi-objective process optimisation of PBF-LB IN625.