Removal rate and surface roughness in the lapping and polishing of RB-SiC optical components

Optical components made of reaction-bonded silicon carbide (RB-SiC) have aroused the interest of researchers and engineers due to their distinct properties, such as low density, high hardness and low thermal expansion coefficient. The present study focuses on efficient fabrication of RB-SiC optical components. Here, a two-stage fabrication process is proposed. Firstly, a plate fixed with solid pellet-shaped abrasives is used for rapid removal of surface error and initial smoothing. After that, fine error removal and surface polishing is performed using felt buffs and diamond abrasives. Material removal rates and surface roughness are measured based on a Form Talysurf surface profiler. The final surface roughness with an initial value of Ra = 110.8 nanometer (nm) reached 21.6 nm after 5 min of lapping by adjusting the size of abrasives continuously from 30 to 10 micrometer (μm), and then convergent to 10.7 nm after 15 min of polishing using different sized diamond pastes as the polishing abrasive. The validity of the two-stage process in terms of efficiency and surface quality has been verified by experiments. How these factors are affected by process parameters such as the relative rotation speed, abrasives grit size, etc. are also examined.