Impact of material microstructure and diamond grit wear on surface finish in micro-grinding of RB-SiC/Si and WC/Co carbides

Ultra-precision surface grinding experiments were conducted at two different grinding conditions (rough and fine) to study the surface finish of RB-SiC/Si and WC/Co carbides, with Si and Co as binders, respectively. It was found that RB-SiC/Si and WC/Co showed two different types of surface generation mechanism under the same selected grinding conditions: brittle fractured surface of RB-SiC/Si and plastic deformation surface of WC/Co. Obvious micro-breaks occurred on SiC surface with a coarse grit wheel at higher material removal rate, but it changed to micro-pits at the phase boundary with a fine grit wheel at a lower material removal rate. Nevertheless, the surface characteristic only changed from rough grinding traces to finer for WC/Co. It was found that the surface finish of RB-SiC/Si and WC/Co was closely related to the material brittleness. The surface roughness (Ra) of RB-SiC/Si was limited to be about 20 nm under both rough and fine grinding conditions while about 5 nm (Ra) could be achieved for WC/Co under the fine condition. It was also identified that the surface profile of workpieces was replicated from diamond grits. To explain the difference in wavy surface profile at nanoscale, a simple model was built to illustrate the impact of grit wear.