Oxidation Behavior and Corrosion Mechanism of Self‐Bonded SiC Refractories in High‐Temperature Water Vapor Environments

ABSTRACT Self‐bonded SiC refractories were exposed to water vapor corrosion at 1000°C for 100, 300, and 500 h, respectively. The phase evolution, microstructure, and pore evolution were analyzed by multi‐scale characterization (XRD, SEM, and X‐ray CT). The results demonstrate that the oxidation mechanism of self‐bonded SiC is governed by a crystallization‐and‐phase‐transition‐controlled degradation process: (1) protective layer instability—initial amorphous SiO 2 formation offers temporary passivation, while both volatilization and quartz crystallization degrade structural coherence; (2) transient passivation—secondary cristobalite growth, facilitated by impurity‐assisted quartz transformation, fills intergranular voids. The resulting crystalline oxide layer reduces water vapor permeability through (i) reduced open porosity and (ii) elongated diffusion paths, temporarily decelerating oxidation; (3) accelerated degradation—time‐dependent phase transformation and cristobalite/SiC thermomechanical incompatibility generated localized stress accumulation, which critically drove progressive oxide layer degradation through crack initiation and interfacial spallation. Stress‐derived percolation porosity networks reactivate aggressive water vapor permeation, while fresh surface exposure drives intensified oxidation. A mechanistic model governing high‐temperature water vapor oxidation in self‐bonded SiC materials was established.