Sliding-wear-resistant liquid-phase-sintered SiC processed using α-SiC starting powders

Low-cost alpha-silicon carbide (SiC) starting powder, instead of the more expensive beta-SiC starting powder, has been used to process liquid-phase-sintered (LPS) SiC ceramics with different microstructures: (i) elongated SiC grains (in situ toughened LPS SiC), (ii) fine equiaxed SiC grains, and (iii) coarse equiaxed SiC grains. The effects of microstructure on the sliding-wear properties of these LPS SiC ceramics have been studied. The sliding-wear resistance of the in situ toughened LPS SiC ceramic is found to be significantly better than that of two equiaxed-grain LPS SiC ceramics. This has been attributed to the existence of a hard, interlocking network of elongated SiC grains and the isolated nature of the yttrium aluminum garnet (YAG) second phase in the in situ toughened LPS SiC ceramic. This is in contrast to the equiaxed-grain LPS SiC ceramics, where the equiaxed grains are embedded within a continuous YAG phase matrix. The use of the alpha-SiC starting powder allows the processing of low-cost LPS SiC ceramics that are both sliding-wear resistant and tough.