The effects of hatch spacing and stripe offset on the surface morphology and microstructure of biomedical 316 L stainless steel formed by laser powder bed fusion

Medical grade 316L stainless steel is widely utilized in biomedical materials applications due to its excellent corrosion resistance and biocompatibility. This study investigates the mechanisms by which hatch spacing and stripe offset affect the surface morphology of medical grade 316L stainless steel during the laser powder bed fusion (LPBF) process. A full-factorial experimental design was employed to systematically examine the synergistic effects of hatch spacing (60–120 μm) and stripe offset (±0.08 mm). Surface roughness, three-dimensional morphology, and microstructural evolution were quantitatively characterized using a digital microscope with extended depth of field and scanning electron microscopy, whereas the surface mechanical properties were evaluated through Vickers hardness testing. The results demonstrate that hatch spacing predominantly controls density and roughness, and optimal overall performance achieved at a hatch spacing of 0.09 mm. Stripe offset further improves surface morphology and density by modulating temperature distribution and its evolution. A slight negative offset was found to effectively suppress keyhole formation and improve surface roughness. Based on these findings, this study establishes an additive manufacturing processing map within the h–Δs parameter space to optimize the surface quality of medical-grade 316L stainless steel, offering a theoretical basis for process optimization of high-surface-quality LPBF components.