Investigation on microstructure and mechanical properties of HfB2-SiC-HfC ternary system with different HfC content prepared by spark plasma sintering

Abstract HfB2-based ultrafine composites with 25 vol% SiC and various volume fractions of HfC (5–20 vol%) have been successfully fabricated using spark plasma sintering. The composites were sintered in both 1800 °C and 1850 °C for different soaking times of 5 and 15 min and flexural strength, hardness and fracture toughness of specimens were measured. Sintering mechanism and mechanical properties of composites and HfC impact on them were investigated. The highest relative density (99.97 ± 0.02%) and the lowest apparent porosity (0.07 ± 0.03) were obtained for the specimen with 15 vol% of HfC. This composite also showed the maximum flexural strength (592 ± 17 MPa) and fracture toughness (4.98 ± 0.12 MPam1/2), even more than the composite with 20 vol% of HfC which had the highest Vickers hardness (22.7 ± 0.9 GPa).