Effect of SiC Content and Particle Size on the Self-Healing Property of Plasma-Sprayed Environmental Barrier Coatings

SiC ceramic matrix composites (CMC) are potential materials for hot section gas turbine components due to their high heat resistance and low density. However, SiC CMC degrades over time in steam oxidation environments. Therefore, environmental barrier coatings (EBC) are necessary to protect SiC substrates. Yb₂Si₂O₇ is one of the most potent materials for barrier coatings. In this study, self-healing property is further added to Yb₂Si₂O₇ EBC by incorporating SiC in the form of Yb₂Si₂O₇/SiC granulated powders. We investigated the effect of different SiC contents and particle sizes on the long-term oxidation behavior of Yb₂Si₂O₇/SiC coatings. The self-healing property was observed in the microstructural changes of artificial cracks induced by Vickers indentation. The samples were oxidized at 1300°C, and the structural change before and after the oxidation was evaluated by SEM, XRD, and EDX. The cross-sectional SEM images show that SiC was entirely oxidized in the first 50 h. Meanwhile, the surface SEM results show that small particle size and high SiC content exhibited a significant volume expansion during the oxidation of SiC. In addition, the self-healing property was significantly active in the initial stage of oxidation, but drastically deteriorated as the oxidation progressed.