Femtosecond laser polishing of SiC/SiC composites: Effect of incident angle on surface topography and oxidation

Abstract

In this article, a new ultrafast laser polishing method for SiC/SiC composites was reported and the effects of different incident angles were discussed in detail. The results indicated that the incident angle had a great influence on the polishing of SiC/SiC composites. Under the normal incident condition, the surface roughness was barely improved and the laser-induced defects even degraded the process quality. With the increasing incident angle, surface oxidation and defects dramatically decreased. At 80 degrees, the surface convex structure is almost eliminated and the protruding fiber was neatly cut off. Furthermore, a theoretical model of laser polishing for SiC/SiC composites is used to analyze the laser propagation and power density distribution in different incident angles. The model successfully predicted the laser energy resonance enhancement and illustrated the formation mechanism of laser-induced defects and nanoripples. Meanwhile, the result shows that the laser energy concentrated on the convex fiber of composites as the incident angle increased, which explained that the SiC/SiC composites polishing quality was significantly improved under the inclined incident condition.