Preparation and properties of mullite-Si₃N₄/SiC composite ceramic

Mullite-Si₃N₄/SiC (M-SBSN) composite ceramic was fabricated by a pressless sintering process. The effects of SiC content and sintering additives as well as mullite on the wearability and thermal/mechanical properties of Si₃N₄/SiC(SBSN) were investigated. The results show that the addition of mullite can improve the sintering properties, bending strength, abrasion resistance and thermal shock resistance as well. M-SBSN composite ceramic with a low density and a superior wearability can be obtained at 1 600℃, which is a relatively low temperature for sintering. The optimal abrasion resistance occurs at mullite addition of 30%. Also, the wearability of the sample is superior to that of Al₂O₃ and ZrO₂ as the wear loss is 80%-85% lower than that of Al₂O₃ and ZrO₂. Moreover, the density is only 76% of Al₂O₃, and 48% of ZrO₂. According to the SEM micrographs, the wearing surfaces of M-SBSN are less worn than those of Al₂O₃ and ZrO₂, which are consistent with the results of the friction and wear test.