THE EFFECTS OF GRINDING PARAMETERS ON THE STRENGTH AND SURFACE FINISH OF 2 SILICON-NITRIDE CERAMICS

The effects of various grinding parameters on the flexural bending strength, surface-roughness parameters, and surface microstructure of two ceramic materials, reaction-bonded silicon nitride (RBSN) and silicon-infiltrated reaction-bonded silicon nitride (SRBSN), are reported in this paper. Experiments were conducted to determine the effect on grit size, depth of cut, material removal rate, and table feed on the strength and surface finish of these ceramics. Surfaces were ground in the longitudinal direction in accordance with common practice for modulus-of-rupture test specimens. The grinding parameters did not have any significant effect on the average strength of these materials, but there were some effects of grit size on the standard deviation in strength of SRBSN. There was an improvement only for the SRBSN material in the surface finish with a decrease in the grit size of the grinding wheel. Scanning-electron microscopy (SEM) showed that the surface features generated during grinding did not vary significantly with the variation in grinding parameters. The mechanical behavior may therefore be more sensitive to the presence of larger flaws in the bulk than to the residual grinding damage at the surface.