Influence of water vapor partial pressure on self-healing and oxidation of SiC-dispersed yttrium silicate composites

Abstract

The self-healing and oxidation behavior of SiC-dispersed Y₂Si₂O₇-Y₂SiO₅ composites were elucidated under various water vapor partial pressures $P_{H_{2}O}$. Samples were exposed in a furnace for self-healing experiments at 1100–1300°C and for high-temperature oxidation at 1200–1400°C, both for 1–24 h, under $P_{H_{2}O}$ ranging from 2×10⁴ to 5×10⁴ Pa, while keeping $P_{O_2}$constant at 2×10⁴ Pa. Water vapor promoted the self-healing effectiveness of the composites. A mechanism contributing to the closure of surface cracks was consistent with volume expansion derived from the oxidative conversion of SiC into SiO₂ and the outward diffusion of yttrium cations. The formation of the internally oxidized zone signifies oxidation behavior, resulting from the inward diffusion of oxygen ions. Growth of the internally oxidized zone obeys the parabolic pattern. The influence of $P_{H_{2}O}$ on the high-temperature oxidation of SiC/Y₂Si₂O₇-Y₂SiO₅ is discussed in this study.