Initial stage of oxidation process and microstructure analysis of HfB₂–20 vol.% SiC composite at 1500°C

The initial stage of oxidation process of HfB2–20 vol.% SiC composite at 1500°C in air was investigated. With no holding, the oxide scale is composed of a discontinuous SiO2-rich glass layer and an imperfect SiC-depleted layer. Detailed analysis showed that the imperfect SiC-depleted layer contained an HfB2 matrix with partially oxidized HfB2 and SiC particles enclosed in graphite, which revealed that the formation of the SiC-depleted layer during oxidation resulted from the active oxidation of SiC with C as an initial product.