Microstructural development and mechanical properties of hot pressed SiC reinforced TiB₂ based composite

Abstract The present work is focused on investigating the effect of SiC addition (0, 15, 20, 25 and 30 vol.%) on microstructural features, phase evolution and mechanical properties of the vacuum hot pressed TiB₂ at 1850 °C/2 h/20 MPa. Hardness measurements revealed an initial increase in hardness from 14.2 GPa for nominally pure TiB₂ to 20.8 GPa for TiB₂-15 vol.% SiC and a subsequent decrease with further increase in the SiC addition. Also the TiB₂-30 vol.% SiC showed an improved indentation fracture toughness of 5.76 MPa m^1/2 which was mostly attributed to the addition of the SiC particles that could activate toughening mechanisms such as crack deflection, crack branching and grain breaking. The microstructure of the sintered samples was characterized by XRD and FESEM, which indicated that SiC reacted with and removed oxide impurities (TiO₂ and B₂O₃) that were present on the particle surfaces. Elimination of such impurities promoted densification by minimizing grain coarsening and in composite contain 30 vol.% SiC the reaction led to in situ formation of TiC. Hence, the results indicated that sinterability of TiB₂-based composites was remarkably improved by addition of SiC compared to the single phase TiB₂ ceramic.