MICROSTRUCTURE, MECHANICAL PROPERTIES AND FRICTION/WEAR BEHAVIOR OF HOT-PRESSED Si_3N_4/BN CERAMIC COMPOSITES

摘要

Nano-scale and micro-scale hexagonal boron nitride (hBN) powders, respectively, were added to silicon nitride (Si3N4) matrix powder, and Si3N4/BN ceramic composites with different content of solid-lubrication hBN were produced by hot pressing. The combined effect of starting powder and hBN content on the microstructure, mechanical properties and tribological properties of Si3N4/BN ceramic composites has been studied. The results showed that the nano-sized starting powder was beneficial to the densification of Si3N4/BN ceramic composites, and resulted in a Si(3)N4/BN nanoano ceramic composite with slightly higher density and improved mechanical properties compared to the corresponding microano ceramic composite. The physical and mechanical properties of Si3N4-based ceramic composites were found to be affected by addition of BN. Increasing BN content led to a decrease of bulk density, hardness, bending strength and fracture toughness. On the other hand, the starting powder has no significant influence on the tribological properties of Si3N4/BN ceramic composites. The friction properties and wear resistance continuously improved with increasing BN content up to 20 vol. %, due to the formation of tribochemical film composed of H3BO3, SiO2, and metal oxides.