Oxidation of ZrB2–SiC ultra-high temperature composites over a wide range of SiC content

The oxidation performance of ZrB2–SiC ultra-high temperature ceramics with SiC content ranging from 20 to 80 vol% has been evaluated at 1773 K for 50 h and at 2073 K for 20 min. Oxidation reaction pathways were interpreted using volatility diagrams of the ZrB2–SiC system. At 1773 K for 50 h, all ZrB2–SiC composites from 20 to 80 vol% SiC formed a protective SiO2 surface coating. Samples with ≤50 vol% SiC developed a distinguishable SiC-depleted layer at 1773 K and 2073 K. High temperature torch testing for 20 min at approximately 2073 K revealed that samples with ≥65 vol% SiC exhibit a depression under the torch flame. Samples rich in ZrB2 were dominated by a ZrO2 layer after a similar exposure. The overall weight density of ultra-high temperature ceramics can be reduced with improved oxidation performance at 1773 K by adding at least 65 vol% SiC.