Concentric mutual lapping to improve sliding surface function of SiC ceramics

Ring-shaped SiC ceramics used in sliding components were examined herein. Conventional lapping generates many shallow scratches in random directions in the surface of such SiC ceramics, and these starches extend from the inner circumference of the surface to its perimeter. The scratches affect the ability of the surface to prevent liquid from escaping from the perimeter side to the inner-circumference side of the SiC ring, and they can increase the friction force of the finished surface as a sliding material. We propose concentric mutual lapping to remove the scratches caused by conventional lapping. The surface topography of a SiC ring is evaluated quantitatively using a white light interferometer, and a vector and quantitative analysis of the surface profile is proposed. The results show that concentric mutual lapping can quickly remove the scratches caused by conventional lapping, and subsequently, circumferential scratches are generated along the lapping direction. We have also conducted sliding tests to analyze the effect of surface topography on the surface function as a sliding material. The results reveal that concentric mutual lapping suppresses the differences in surface function that occurred depending on the sliding direction.