Effects of laser fluence on the micro-structure formation and material removal rate in ablation of silicon carbide

Laser micro-drilling or machining of high aspect ratio features often encountered reducing material removal rate (MRR) with increasing laser power or drill time. The laser ablated material appeared to have difficulties in ejecting out of the deep holes, being blocked by the debris and side walls in the holes. We found that the reduction in MRR also happens to many materials when micro-machining low aspect ratio surface profiles. This paper describes the surface microstructure formation phenomena and its effects on the ablation rate during laser machining of SiC. It was found that four stages of SiC surface modifications were produced, namely melting, ablation, formation of spherical-shaped nodules, and build up of white flake substances. The four regimes were formed depending only on the laser fluence irrespective of the beam power, travel speed and track overlapping density. The results also showed that MRR was highly affected by the formation of different micro-structures on the surface, and that high laser fluence might lead to low MRR.