Mechanical properties and ablation behavior of ZrB2-SiC ceramics fabricated by spark plasma sintering

ZrB2-SiC ceramics were prepared by spark plasma sintering at 1375 °C for 5 min under a uniaxial load of 25 MPa. Mechanical properties and ablation behavior of ZrB2-SiC ceramics were investigated. The results showed that the flexural strength of ZrB2-30 vol.% SiC ceramic was significantly higher than that of ZrB2-15 vol.% SiC ceramic due to the larger amount of SiC whereas the ablation resistance was reduced. The increase in flexural strength was attributed to the sintering of SiC particles which located in the boundary of ZrB2 and enhanced the binding force between ZrB2 particles. The decrease in the ablation resistance at 3000 °C was due to the increase in weight loss and voids which were mainly caused by the rapid evaporation of SiO2. Ablation mechanism revealed that excessive SiC could supply much flaws and was hard to form continuous layer to seal the defects, which led to the dissatisfactory resistance to ablation for the ZrB2-30 vol.% SiC. The different ablation behaviors of central and outer ablation regions were also discussed.