Oxidation behavior of ZrC-based composites in static laboratory air up to 1300 °c

Two ZrC-based composites, viz., ZrC + 20 vol.%SiC and ZrC + 20 vol.%SiC + 20 vol.%ZrB₂, were prepared by hot pressing. The oxidation behavior of the composites was studied in the temperature range of 800 °C-1300 °C in air. From the mass gain tests, the surface and cross-sectional SEM observation and EDS analysis of the oxidized samples, it was found that the ZrC + 20 vol.%SiC composite seemed to have a high oxidation resistance below 1000 °C, but the ZrC + 20 vol.%SiC + 20 vol.%ZrB₂ composite appeared a more excellent oxidation resistance up to 1200 °C. It is main reason that the oxidation rate of ZrC is higher than that of SiC below 1300 °C, meaning that SiO₂ from SiC is insufficient to form a dense tight protection film; however, the addition of ZrB₂ particles promotes the formation of more borosilicate above 1000 °C, which exerts more protective effect by self-healing mechanism.