Laser polishing for integrated enhancement of thin-walled LPBFed dental Co-Cr-Mo alloy frameworks.

Abstract

Removable partial denture (RPD) frameworks manufactured using laser powder bed fusion (LPBF) offer high accuracy and short production cycles; however, surface post-processing these thin-walled, complex-shaped components presents significant challenges. Conventional mechanical method is time-consuming, labor-intensive, and difficult to apply uniformly on such intricate structures. In this study, an efficient laser polishing method was proposed to post-process the LPBFed RPD frameworks. The results demonstrate that the surface roughness of LPBF framework decreased from Sa 12.75 μm to Sa 0.72 μm at optimized laser polishing parameters. The microstructure of the surface layer transformed from fully ε-martensite to a fine mixture of austenite and ε-martensite, and the density of dislocations was also increased in the remelting layer. The microhardness and ultimate tensile strength were improved due to grain refinement and high-density dislocations in the remelted layer. The improved corrosion resistance is attributed to a refined grain structure and Mo enrichment, which promote a more protective passive film and facilitate the formation of a stable, electrolyte-derived bio-integrated film. Furthermore, the average and maximum dimensional deviations induced by laser polishing were 21 μm and 253 μm, respectively, indicating minimal impact on the dimensional accuracy of the frameworks.