Experimental study on the multiscale surface morphology of femtosecond laser polishing of silicon carbide ceramics based on inclination angle effect

In this paper, an infrared femtosecond laser was used to polish silicon carbide ceramics at large incidence angles. For silicon carbide ceramics with different initial roughness surfaces, the improvement mechanism of laser incident angle on polishing surface quality was systematically analyzed. The effects of other process factors during laser polishing, including spot overlap rate, laser power, and scanning times, on the polishing quality when processing with a large incident angle was investigated. The results indicate that, compared to a vertically incident laser, laser polishing at large incident angles significantly enhances surface roughness. During the polishing process, the laser first removes the higher convex structures on the surface, which helps level peaks to obtain a smooth material surface. Additionally, at an incident angle of 80°, the surface roughness of the polished surface gradually decreases with the increase of the spot overlap rate in the X direction and the Y direction. The roughness only increases when the X-direction overlap rate is 95 %. As single pulse energy increases, the roughness of the polished surface shows a trend of initially increasing and then decreasing. With the increase in laser repetition frequency, the roughness of the polished surface shows a general trend of slow decrease. As the scanning times increase, the roughness of the polished surface generally exhibits a trend of initially decreasing and then increasing. Throughout the experimental process, when the laser incidence angle was set at 80°, the pulse energy at 85 μJ, the overlap rate in the X direction at 90 %, the overlap rate in the Y direction at 95 %, the laser repetition rate at 35 kHz, and the scanning times at 6, the surface roughness of the silicon carbide ceramic reached a minimum of 0.74 μm with the 1000 × magnification.