Laser Surface Polishing of Additively Manufactured Components via Beam Shaping: Influence on Surface Topography, Microstructure, and Mechanical Properties

Additively manufactured components often exhibit poor surface quality due to partially fused powder particles and overlapping tracks. To overcome this limitation, laser surface polishing (LSP) was applied to laser-directed energy deposited Stellite6 samples. LSP involves surface remelting, redistributing molten material between peaks and valleys and eliminating asperities formed during deposition. In this study, two beam geometries, a circular beam (3 mm diameter) and a line beam (16 × 0.5 mm2), were evaluated for improving surface finish and mechanical performance. A constant interaction time was maintained using polishing speeds of 1200 mm/min for circular beam and 200 mm/min for line beam at 1000 W. Scanning orientations of 0°, 45°, and 90° relative to deposition tracks were investigated. The line beam at 0° produced the best surface finish by melting tracks simultaneously, whereas circular beam melted fewer tracks per pass. At 90°, narrow line beam limited effectiveness, and at 45°, both beams produced poor finish due to misaligned melt pools. Surface roughness reductions of ∼80% and ∼86% were achieved with circular and line beams. Both beams enhanced hardness and wear resistance through microstructural refinement. The circular beam caused deeper remelting with a columnar dendritic structure, while the line beam produced a shallower melt pool with equiaxed grains. Wear changed from adhesive in as-deposited samples to abrasive and delamination after polishing, with circular beam-treated samples showing the least wear. Overall, LSP improved surface quality and mechanical performance, with beam geometry and scan orientation influencing outcomes.