Effects of boron content on the microstructure and properties of B_xC-TiB₂ (x=4.5, 6.5 or 8.5) ceramic composites by the reactive spark plasma sintering

BxC-TiB2 ceramic composites were fabricated via reactive spark plasma sintering using TiC and B as the raw materials. The impact of B/TiC mole ratios on the phase compositions, densification behaviors, microstructure, and mechanical properties of the ceramic composites were investigated. The results showed that the stoichiometry of ‘BxC’ could be tailored by changing initial boron content and the obtained B4.5C, B6.5C and B8.5C phases have the same crystal structure (R-3 m). The excess of B enhanced the reaction between TiC and B, which released a large amount of hot energy and promoted the densification of the composites. The TB8.5 composite sintered at 1900°C had the best comprehensive mechanical properties, with hardness and flexural strength of 40.36 GPa and 551 MPa, respectively. The formation of nano-sized TiB2 grains induced by reaction were beneficial for improving the mechanical properties of these composites.