Densification and mechanical properties of B4C-SiC-BN multiphase ceramics fabricated by reactive spark plasma sintering

The phase composition, densification, microstructure, and mechanical properties of B 4 C-based composite ceramics reinforced with SiC and BN platelets fabricated from B 4 C and Si 3 N 4 via in situ spark plasma sintering were discussed. The densification of B 4 C began at a lower temperature, where the reaction between Si 3 N 4 and B 4 C enhanced the sintering ability of B 4 C grains. The in situ-formed SiC and BN nanoparticles were uniformly distributed around the larger B 4 C particles and effectively inhibited the growth of B 4 C grains. The B 4 C-SiC-BN multiphase ceramic containing 10 wt% Si 3 N 4 , sintered at 1850 °C for 5 min, exhibited optimal performance, with a relative density of 99.30 %, Vickers hardness of 27.14 GPa, flexural strength of 356 MPa, and fracture toughness of 4.13 MPa m 1/2 . The flexural strength and fracture toughness increased by 55 % and 38 % compared to pure B 4 C. The mismatch in thermal expansion coefficients among B 4 C, SiC, and BN generated microcracks, which led to crack deflection, branching, and bridging, thereby effectively enhancing the toughness of B 4 C.