Influence of overlap between the laser beam tracks on surface quality in laser polishing of AISI H13 tool steel

Polishing by laser beam radiation is a novel manufacturing process to modify the initial surface topography in order to achieve a desired level of surface finish. The performance of laser polishing (LP) is determined by an optimum combination of several key process parameters. In this regard, the overlap between two successive laser beam tracks is one of the important LP process parameters, which has a significant effect over the final surface quality. In the current study, influence of overlap between the laser beam tracks on surface quality was experimentally investigated during the laser polishing of AISI H13 tool steel. Surface areas were polished by using four different overlap percentages (e.g. 80%, 90%, 95%, and 97.5%) while applying the same energy density. The improvement of surface quality was estimated through the analysis of line profiling surface roughness Ra, areal topography surface roughness Sa, and material ratio function. Also, individual components of the surface quality, e.g. waviness and roughness, and their evolution during LP were statistically analyzed using the power spectral density and the transfer functions. Finally, as an example of the best achieved LP result, flat surface area was polished using optimum set of the process parameters improving surface quality by 86.7% through the reduction of an areal topography surface roughness Sa from 1.35 μm to 0.18 μm.