Investigation on the preparation of Si/mullite/Yb2Si2O7 environmental barrier coatings onto silicon carbide

With the development of aero-engine, gas import temperatures of hot section structural materials are increasingly higher. Metal alloy materials due to the rapidly decreased mechanical properties at relative high temperature are gradually replaced with silicon-based non-oxide silicon carbide ceramics. However, silicon carbide ceramic materials tend to spall and deform in engine combustion environment, need environmental barrier coatings for the protection of the matrix. The preparation of Si/mullite/Yb2Si2O7 environmental barrier coatings onto silicon carbide was realized with plasma spraying and sol-gel method. Coatings structure, surface morphology and layer components were principally discussed through the test of X-ray diffraction (XRD), thermogravimetric analysis (TG) and scanning electron microscopy (SEM). This paper explored how to match coefficient of thermal expansion (CTE) and enhance chemical compatibility effectively. The results showed that most areas of the environmental barrier coatings were uniform, close-grained and crack-free, which could maintain excellent adherence. Their oxidation resistance would be better with the increase of dipping time and spraying time in preparation.