A novel super hard ZrO₂/ZrB₂/VC nanocomposite in presence of liquid phase

In this research, ZrO₂/ZrB₂/VC nanocomposite in the presence of silicon liquid phase was sintered via spark plasma method at a temperature of 2000 °C and holding time of 12 min. The relative density of the sample was measured by the Archimedes method. Phase identification and microstructural studies were done using X-ray diffraction analysis and scanning electron microscope, respectively. The hardness and fracture toughness of the samples were measured using the Vickers method and crack length measurement. The results showed that the sintered sample has an almost complete relative density (99.3%) with a very high hardness of 33.1 GPa. The fracture toughness values calculated by Anstis and Shetty methods were obtained at 8.53 MPa m^0.5 and 13.51 MPa m^0.5, respectively. These combinations of good mechanical properties were related to reaching the nanostructure (crystallite size of 22.6 nm and 36 nm according to the Scherrer–Monshi and Williamson–Hall methods) and nanograin size of 84 nm as well as formation of oxide/boride/carbide solid solution with expansion lattice parameters which enhances both hardness and fracture toughness simultaneously.