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

Abstract

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.