Grooving on SiC Ceramics Surface by Reaction with Solid Metal (Part 3)

Chemical reaction between SiC ceramics and Ni foil has been used for making grooves on the sliding face of SiC ceramics. The grooved face should be crack free, and then generation of cracks was already understood to be dependent on the size of deposited graphite in reaction product layer. To investigate the growth of graphite in detail, graphite remained after dissolving other reaction products with acid, and the mean diameter of the graphite particles was determined from SEM photos. The graphite particles grew as a function of cube root of time. When the mean graphite particle diameter was larger than about 3μm, cracks were not generated on the SiC face. The influence of sintered SiC structure on the reaction product layer was investigated. Reaction between Ni foil and low density SiC or SiC as with extraordinarily large grains yielded graphite, δ-Ni2Si and Ni3Si2, as with normally sintered SiC. The size of graphite particles in reaction product layer of low density SiC was smaller than that of other sintered bodies, and craks were generated on the surface of low density SiC. In low density SiC, the smaller size of graphite particles was considered to promote crack formation, in addition to the low strength due to the low density.