Mechanical properties and microstructure evolution of pressureless-sintered B4C–SiC ceramic composite with CeO2 additive

Abstract Boron carbide ceramic composites (B 4 C)-silicon carbide (SiC) with the cerium oxide (CeO 2 ) additive, which was varied from 0 wt% to 9 wt%, were prepared by pressureless sintering at 2150 °C for 60 min. The effect of CeO 2 additive content on the microstructure and mechanical properties of the B 4 C–SiC ceramic composites was investigated in detail. In-situ synthesised cerium hexaboride (CeB 6 ) was identified in the B 4 C–SiC ceramic composites. B-rich transition zones (such as B 38.22 C 6 , B 51.02 C 1.82 ) were formed between the B 4 C and CeB 6 grains, which introduced local lattice distortion to increase the sintering driving force. The thermal conductivity coefficient of CeB 6 was higher than that of B 4 C, which benefited the delivery of heat quantity and helped achieve a highly dense and uniform sintered body. When the CeO 2 additive was excessively increased (more than 5 wt%), the CeB 6 grains had a large grain size and exhibited an increase in the amount of generated carbon monoxide (CO) gas, which led to an increase in the porosity of the B 4 C–SiC ceramic composites and decrease in the mechanical properties. The optimum values of the relative density, Vickers hardness, flexural strength, and fracture toughness of the B 4 C–SiC ceramic composite with 5 wt% CeO 2 additive were 96.42%, 32.21 GPa, 380 MPa, and 4.32 MPa m 1/2 , respectively.