Evaluation of Laser-Welded IN625 Produced via Laser Powder Bed Fusion

This study investigates and evaluates laser welds of Inconel 625 produced via laser powder bed fusion (L-PBF). Bead-on-plate welds were performed on plates manufactured in different orientations (horizontal, vertical, and diagonal) using a high-power laser system. The research comprehensively characterizes the welds to assess the influence of the unique L-PBF microstructure, building orientation, and key process parameters-welding speed, laser power, and power modulation. Metallographic analysis confirmed that all welds were fully penetrated and largely free from defects such as solidification/liquation cracks and porosity. The results demonstrate that the peculiar, textured microstructure of the L-PBF material and the building orientation have a negligible impact on weld quality. Furthermore, within the studied ranges, laser power and modulation showed a minimal effect, with welding speed being the primary parameter controlling the fusion zone size. To deepen the microstructural analysis, a semi-analytical thermal model was developed and calibrated to simulate the characteristic hourglass-shaped melt pool. The computed thermal fields were used to establish a quantitative correlation between the local cooling rate (G × R) and the secondary dendritic arm spacing (SDAS) measured within the fusion zone, providing insight into the solidification conditions. It is concluded that L-PBF IN625 can be conveniently welded through a laser welding process, with the joint integrity being largely independent of the initial building orientation and robust to variations in the laser welding parameters investigated.