Microstructure, mechanical properties and thermal shock behavior of h-BN-SiC ceramic composites prepared by spark plasma sintering

Abstract

h-BN-SiC ceramic composites with different SiC contents were fabricated by spark plasma sintering. The results indicate that the addition of hard SiC particles has a remarkable effect on the densification, microstructure, mechanical properties and thermal shock resistance of the composites. Compared with pure h-BN ceramic, the relative density and mechanical properties of h-BN-SiC ceramic composites were improved obviously. The optimal properties of h-BN-SiC ceramic composites were obtained at SiC content of 25%, and the relative density, flexural strength and fracture toughness reached 97.8%, 289.2MPa and 3.45MPam1/2, respectively. Moreover, the relationship of fracture toughness and fracture mode was discussed. The thermal shock test results showed that the h-BN-SiC ceramic composite with the SiC content of 25% exhibited excellent thermal shock resistance, presenting critical temperature difference up to 900 °C. The high temperature oxidation of h-BN and SiC on material surface led to the formation of borosilicate glass phase, which could heal the surface microcracks and then improve the thermal shock resistance.