Mechanism of High-Temperature Oxidation of ZrB2-Based Composite Ceramics in the ZrB2–SiC–AlN System

Abstract

The paper examines the oxidation of the ZrB2–SiC–AlN composite at high temperatures (1550–1700°C) and focuses on the structure and phase composition of the starting ceramic material and scale layer. The oxide layer develops in two stages. At the low-temperature stage (1170–1250°C), an intermediate layer forms, consisting of ZrB2 and involving solid solutions in the AlON–SiC/SiO2 system. The high-temperature stage (1250–1350°C) gives rise to the main protective layer consisting of xAl2O3–ySiO2 mullite solid solutions and colonies of zirconium oxide crystals, located at the grain boundaries of the mullite phase. The resultant oxide layer is an effective potential barrier to the diffusion of oxygen into the sample.