Mechanical and oxidation behavior of spark plasma sintered ZrB ₂-ZrC-SiC composites

ZrB₂-ZrC-SiC composites were prepared by spark plasma sintering (SPS) at temperatures of 1750°C for 300s under a pressure of 40MPa. Densification, microstructural, mechanical properties and oxidation behavior of the composites were investigated. Fully dense ZrB₂-ZrC-SiC composites with a relative density of more than 99% were obtained at 1750°C for 300s. Vickers hardness of ZrB₂-ZrC-SiC composites decreased with increasing ZrC content from 20 to 40vol%, and composite containing 60 vol% ZrB ₂, 20vol% ZrC and SiC sintered at 1750°C for 300s had the highest value of 21.1 GPa. The crack mode for the same composite was zigzag, and resulted in remarkable crack deflections and the highest fracture toughness value of 5.5 MPa·m^1/2. Oxidation of composites resulted in formation of protective layered oxide structures consisted of ZrO₂ and Si-O rich layer in the form of SiO₂ or SiO, and normalized mass change results increased with increasing oxidation temperature.