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 degrees 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.

Automated summary

SiC ceramic matrix composites (CMC) have potential applications in hot section gas turbine components due to their high heat resistance and low density, but they degrade over time in steam oxidation environments. In this study, environmental barrier coatings (EBC) containing Yb2Si2O7 were used to protect SiC substrates. Self-healing property was enhanced by incorporating SiC in the form of Yb2Si2O7/SiC granulated powders. Different SiC contents and particle sizes were investigated to evaluate the long-term oxidation behavior of the coatings.