Synthesis of boron nitride- silicon carbide composites and investigation of its properties

SiC is a covalently bonded hard material, therefore the production and machinability of complex shaped parts are difficult and expensive. In this study, the production of hBN-SiC composites was investigated to improve properties and machinability of SiC by using hBN. hBN-SiC composite powders were produced by coating the surface of α-SiC powders with hBN particles in H3BO3 and CO(NH2)2 chemical reactions, calcined and hBN-SiC composite was obtained by shaping and sintering it with SPS method. Effects of boric acid : urea ratio and calcination times on composite powder production were investigated. The composite powders were sintered in SPS with the addition of Al2O3-Y2O3 and the changes in microstructure, physical and mechanical properties were determined. The activation energy of the SiC grain's growth was calculated depending on the sintering temperature, and the effect of hBN amount on SiC grain's growth was examined. The fracture behavior and machinability properties of hBN-SiC composites were investigated, and tribology tests were carried out. The formation of hBN was found to be influenced by urea amount and calcination time. It has been found that there was a decrease in physical and mechanical properties of hBN-SiC composites, faster machinability, and increased surface wear with increasing hBN amount.