Defects, microstructure, and properties in laser powder bed fusion IN718: Power density effects and feature maps

The cross-industry applications of additive manufacturing components necessitate a thorough understanding of potential outcomes within the formable range. In this study, we examine the defects, microstructure, and mechanical properties of L-PBF IN718 across a broad spectrum of power densities (18–1000 J/mm³). Our findings demonstrate that even under ultra-high power density conditions (623 J/mm³), conduction mode can still be achieved, with five stable processing windows consistently observed between 48 J/mm³ and 623 J/mm³. Lack of fusion defects manifests in various types distributed perpendicular to the build direction, exhibiting an average sphericity of 0.49 and mean size of 217 μm. Interestingly, keyhole pores tend to be oriented perpendicular to the building direction rather than elongating along it (83°), with a mean sphericity of 0.57, and a mean size of 173 μm. Additionally, our observations indicate that high thermal input leads to grain boundary enhancement resulting in a distinct grain morphology different from typical L-PBF results. Furthermore, we developed comprehensive defect and microstructure feature maps that encompass potential outcomes of defect distribution patterns and grain morphologies observed in L-PBF IN718. Findings highlight geometrically necessary dislocations (GND) and grain morphology as key factors contributing to strength deterioration and excellent elongation in samples subjected to high thermal input. This study aims to provide a comprehensive understanding of L-PBF IN718's potential outcomes across the available sample power densities range.