Oxidation behavior of ZrB₂-15vol.%SiC at an oxygen partial pressure of 57 Pa

The oxidation tests of the ZrB₂-15vol.%SiC composite were carried out at 1673-1923 K under a low partial pressure of oxygen. Cross sections of the oxidized samples were studied using WDS. The reaction layer consists of ZrO₂ and SiO₂ at 1673 K. The SiO₂ protective layer is formed on the surface. No apparent SiC depleted layer is observed. SiC depletion seems to occur at 1923 K and only the ZrO₂ phase exists at the reaction layer. The passive oxidation occurs at 1673 K, whereas the active oxidation at 1923 K. The mass changes are quantitatively discussed by introducing a new emprical equation. The ZrB₂-30 vol.%SiC composite is also discussed briefly.