Analysis and classification of the process-induced surface topography nonuniformities during laser remelting

Surface polishing by laser remelting (SP-LRM) uses the energy of a focused laser beam to remelt the thin top layer of the workpiece material in order to improve its surface quality by 3D topography smoothing. Visual observations of the experimentally-obtained remelted laser tracks revealed that the uniformity of the LRM surface topography highly depends on the stability of the laser-material interactions and initial surface topography. Two metrics of LRM topography were proposed to assess the LRM process stability: uniformity of the laser track contour and uniformity of the middle longitudinal profile. Several sub-areas of the LRM tracks with typical topographic nonuniformities were visually selected and their nonuniformity metrics determined. Two common types of surface topography nonuniformities characterized by distinctive geometric patterns were identified: those induced by the LRM process (excessively remelted material) and those affected by the surrounding initial surface topography. The obtained results open new research avenues toward the in-process estimation of the surface topography formation and evolution via online monitoring of the LRM process stability.