Role of co-addition of BN and SiC on microstructure of TiB₂-based composites densified by SPS method

The present research aims to investigate the influences of SiC reinforcement and h-BN additive on the relative density, microstructure, and thermodynamic aspects of TiB₂-based ceramics. Three different specimens, including monolithic TiB₂, TiB₂–SiC, and TiB₂-SiC-BN were fabricated using spark plasma sintering (SPS) at 1900 °C. A dwelling time of 7 min and an external pressure of 40 MPa were applied as the sintering conditions. The characteristics of SPSed monolithic TiB₂ and the prepared composites were studied using X-ray diffractometry, thermodynamic inspections, and scanning electron microscopy. These assessments unveiled the in-situ formation of TiC and graphitized carbon in the TiB₂–SiC preparation process, whereas no carbon was detected in the composite doped with h-BN. Introducing SiC had immense impact on the relative density of both composites, yielding near fully dense ceramics. The intergranular type was the dominant fracture mode in the all three TiB₂-based ceramics. Moreover, the addition of secondary phase substantially refined the microstructure of TiB₂, reaching ceramics with finer grains than the undoped ceramic.