Phase evolution during spark plasma sintering of novel Si3N4-doped TiB2–SiC composite

Spark plasma sintering process was employed to fabricate TiB2–SiC and novel Si3N4-doped TiB2–SiC ceramic composites at 1900 °C for 7 min under 40 MPa. The microstructural development of TiB2-based composites was significantly influenced by the addition of SiC as a reinforcement phase and Si3N4 as a sintering aid. Thermodynamic assessment, X-ray diffractometry, scanning electron microscopy and energy dispersive spectroscopy disclosed the in-situ formation of TiC, B4C and SiO2 in both samples as well as TiN and BN in the Si3N4-doped TiB2–SiC sample through the chemical reactions of SiC and Si3N4 additives with the surface oxide impurities of TiB2 particles (TiO2 and B2O3). The elimination of harmful oxide layers and the in-situ formation various secondary phases had remarkable influences on the sinterability and final microstructure of TiB2. •The effect of Si3N4 addition on microstructure of TiB2–SiC composite was studied.•Fully dense TiB2-based composite was obtained by addition of SiC and Si3N4.•TiC, B4C and SiO2 were formed in Si3N4-free and Si3N4-doped TiB2–SiC ceramics.•TiN and BN were in-situ formed only in Si3N4-doped TiB2–SiC sample.