Laser polishing for surface enhancement of AISI 316 L parts fabricated by laser powder bed fusion

This study investigates the influence of laser polishing (LP) as a post-processing method for enhancing the surface quality of Laser Powder Bed Fusion (LPBF) components. Cylindrical specimens were manufactured using LPBF processing parameters (i.e., laser power of 150 and 170 W, and point distance of 20 and 30 μm) for a range of specific energies between 5.0 and 8.5 J/mm2. After this process, LP treatment was performed on the top surfaces at energy densities ranging from 0.142 to 0.475 J/mm. Surface characterization was performed by measuring surface roughness (Ra, Rz), height, and surface topography quality. Apparent density and cross-sectional surface porosity of the LPBF were quantified. The results indicated that higher specific energy values (> 7.5 J/mm2) during the LPBF process produced samples with lower surface roughness, reduced porosity (1.42–1.97%), and increased density (7.30–7.36 g/cm2). LP post-processing demonstrated that an energy per unit length of 0.225 J/mm was most effective at reducing the ten-point mean roughness and height across all sample types. The maximum reduction in ten-point surface roughness achieved was 52.5% (from 70.71 μm to 33.58 μm) in samples with a specific energy of 5.33 J/mm2. Microhardness measurements revealed that LP slightly softened the near-surface region (≈ 4 μm depth) in high-porosity samples, while samples with porosity below 2% exhibited higher and more uniform hardness profiles up to 1000 μm. Our findings reveal that LP effectiveness is strongly dependent on initial surface quality and porosity of LPBF components, emphasizing the importance of post-processing stages for achieving a superior surface finish.