Mechanical and tribological performances of C-SiC nanocomposites synthetized from polymer-derived ceramics sintered by spark plasma sintering

The mechanical and tribological performances of densified polymer-derived C-SiC nanocomposites containing in situ formed nano-carbon were studied. The hardness, elastic modulus, and fracture toughness of the nanocomposites decreased while increasing the carbon volume from 5% to 16%. Compared with monolithic SiC, all the nanocomposites showed higher toughness as a result of the crack deflection and bridging of the carbon phase. The wear mechanism included mechanical wear (micro-crack), abrasive wear, carbon lubrication, and humidity-driven tribochemical reactions. Wear resistance was found to be mainly controlled by both the hardness and the crystal size of SiC. 6%-DP, with the smallest SiC crystal size, showed the highest wear resistance among the samples studied though with a lower hardness herein. The small SiC crystal size was important in accelerating the formation of a tribo-oxidation-film and contributed to increase the fraction of transgranular fractures, both improving wear resistance.