Microstructure and mechanical property of B4C–SiC–CrB2 composites fabricated via reactive hot pressing

Dense B 4 C–SiC–CrB 2 ternary composites were fabricated via reactive hot pressing with B 4 C and chromic silicides (84 wt% CrSi 2 +16 wt% CrSi) as raw materials. The effects of chromic silicides on the densification, phase components, microstructure and performance of the prepared composites were investigated. The reaction mechanism and toughening mechanism were also studied. The results indicated that the chromic silicides were the reactive sintering aids which reacted with B 4 C and C to introduce CrB 2 and SiC in the matrix in situ. Partial B 4 C, CrB 2 and SiC formed the eutectic liquid phase, which enhanced the densification of B 4 C. The addition of chromic silicides enhanced the densification and fracture toughness while reduced the hardness. The good comprehensive performances of 435 MPa flexural strength , 4.09 MPa m 1/2 fracture toughness and 33.11 GPa hardness were obtained in the composites fabricated with 10 wt% chromic silicides. The higher addition amounts of chromic silicides resulted in the larger-size SiC, which reduced the flexural strength. The transgranular fracture of SiC and partial CrB 2 , the existing phenomena such as microcracks , crack branching and crack deflection could cumulatively improve the fracture toughness of the materials.