Evaluation of Spatter Generation and Compositional Changes of Hastelloy X during Laser Powder Bed Fusion using <i>In-Situ</i> X-ray Imaging and EPMA

The additive manufacturing of porous and lattice metals is advancing rapidly. However, laser powder bed fusion (LPBF) presents several challenges. In particular, the relationship between evaporation-driven spatter and compositional changes, which are critical defects remains unclear. The LPBF of Hastelloy X (HX) was investigated to clarify the relationship between the amount of spatter and compositional changes along the melt track. In-situ X-ray radiography was performed to quantify the amount of spatter based on the mean brightness of the region of interest, Imean, during 3.5 s of laser irradiation at a laser power of 100 W and a laser scanning speed of 5 mm·s−1. Ex-situ electron probe microanalysis (EPMA) was performed, which provided composition at 1 mm intervals along the track centerline. The Imean decreased significantly at x ≈ 0–2.5 mm and then recovered, thus indicating that the spatter generation peaked near the scan start. Additionally, EPMA revealed a localized Ni decrement and Mo increment at x ≈ 2 mm, whereas Cr, Fe, and Co largely remained within the ±2σ range of the composition of the as-received powder. The composition of the spatter was equivalent to that of the as-received powder, which did not support the selective carry-off of Ni. These findings are consistent with preferential Ni evaporation at the scan start, which elevates the recoil pressure and promotes spatter. The integrated in-situ and ex-situ monitoring quantitatively correlates spatter intensity to track compositional changes, thus offering a mechanistic basis for mitigating evaporation-induced deviations in the LPBF of HX.