Experimental investigation on the surface and subsurface damages characteristics and formation mechanisms in ultra-precision grinding of SiC

Surface and subsurface damages appear inevitably in the grinding process, which will influence the performance and lifetime of the machined components. In this paper, ultra-precision grinding experiments were performed on Reaction-bonded Silicon Carbide (RB-SiC) ceramics to investigate surface and subsurface damages characteristics and formation mechanisms in atomic scale. The surface and subsurface damages were measured by a combination of scanning electron microscopy (SEM), atomic force microscopy (AFM), raman spectroscopy and transmission electron microscope (TEM) techniques. Ductile-regime removal mode is achieved below critical cutting depth, exhibiting with obvious plough stripes and pile-up. The brittle fracture behavior is noticeably influenced by the microstructures of RB-SiC such as impurities, phase boundary and grain boundary. It was found that subsurface damages in plastic zone mainly consist of stacking faults (SFs), twins and limited dislocations. No amorphous structure can be observed in both 6H-SiC and Si particles in RB-SiC ceramics. Additionally, with the aid of high resolution TEM analysis, SFs and twins were found within the 6H-SiC closed packed plane i.e. (0001). At last, based on the SiC structure characteristic, the formation mechanisms of SFs and twins was discussed, and a schematic model was proposed to clarify the relationship between plastic deformation induced defects and brittle fractures.