Experimental investigation on electrical discharge diamond grinding of RB-SiC ceramics

The reaction-bonded silicon carbide (RB-SiC) ceramics are very difficult to be machined by conventional techniques. In this work, a hybrid process termed electrical discharge diamond grinding (EDDG) was applied to the precision grinding of RB-SiC ceramics considering its weak electrical conductivity. Focus of investigation was especially placed on the effects of grit sizes and polarities of grinding wheel on the surface quality. The machined surface texture and roughness were measured by confocal scanning laser microscope. The surface texture topography and cross-section profile at different grit sizes and polarities were analyzed. The results show that the dominant state of grinding or EDM decides surface texture of machined surface and consequently affects the surface roughness. The surface morphology and subsurface damage were measured by scanning electron microscopy and energy dispersive spectrometer (EDS). The influence of grit sizes and polarities of grinding wheel was focused on the resolidified zone of the machined surface. The material migration phenomenon was found. The subsurface damage was also analyzed by detecting the polished cross-sections, and the depth of subsurface was determined by analyzing the element distribution with EDS spectrums. At last, the formation mechanism of machined surface and the effects of grit sizes and polarities of grinding wheel on machined surface quality were discussed from the viewpoint of discharge energy based on EDM theory.