Influence of surface morphology and processing parameters on polishing of silicon carbide ceramics using femtosecond laser pulses

In this paper, silicon carbide (SiC) ceramics were polished using a high-frequency femtosecond laser (fs-laser). The influence of different laser incidence angles on the machined surface were investigated in detail, and the processing morphologies for different laser processing parameters were analyzed and optimized. The theoretical simulation and experimental results indicated that the original surface defects of pits prior to processing of the SiC surface remarkably affects the ablation effect. When fs-laser polishing at vertical incidence, the effect of light trapping occurred in the pits due to multiple reflections, enhancing the absorption of laser energy to enlarge the size of pits. The small incidence angle can eliminate the effects of light trapping in the pits and obtain the smooth surface of the material. In addition, the degree of oxidation and graphitization decrease significantly with a decrease of incidence angle. The optimal processing parameter combination under the incidence angle of 10 degrees, laser frequency of 100 kHz, scanning speed of 200 mm/s, single pulse energy of 60 mu J was obtained. The polished SiC ceramic exhibited a smooth, flat and pit-free surface with the average Sa of 0.187 mu m and Sz of 2.313 mu m. Finally, the formation of typical features such as pits, particles and debris deposition, was explained in detail. Our work provides new research ideas for understanding the polishing mechanisms concerning the removal of surface defects and depositions from the SiC ceramics.