Oxidation of ZrB2 and its composites: a review

The oxidation behavior and oxidation mechanisms of monolithic ZrB2 and particulate-ZrB2 matrix composites were reviewed. Dispersion of SiC particles into ZrB2 was found to be an effective way to prevent extensive oxidation. However, the formation of a SiC-depleted layer can become a critical problem because it can lead to spallation and delamination of the protective surface layer. The addition of ZrC in conjunction with rapid heating to temperatures higher than 2000 °C effectively reduced the porosity of the SiC-depleted layer. The formation of a dense surface layer was attributed to large volumetric expansion during the conversion from ZrC to ZrO2. The effect of the ZrC addition depended on the temperature, heating rate, and composition. This review showed that material design for specific applications is required for high-temperature applications to maximize the oxidation resistance of ZSZ composites.