Effect of grinding and polishing on the residual stress and bending strength of a silicon nitride ceramic

The residual stresses on the surface of the differently ground and polished silicon nitride ceramics were measured using X-ray diffraction and identified by SEM. The effect of the residual stress on the bending strength was investigated. The investigations show that the grinding process can introduce subatantial tensile residual stresses up to 290 MPa on the surface of silicon nitride ceramics, which has a significant effect on reducing the bending strength of the ceramics after grinding. Thus, in comparison with the ceramics with a rough surface, the ceramics with a mirror image surface may have a lower strength. Polishing can smooth the residual stresses. When we evaluate the quality of the ceramic components after grinding, we must take residual stress into consideration. The grinding methods and grinding conditions must be carefully selected in order to get the fovorite residual stress as well as the surface smoothness.