Investigation of ultra-high temperature performance of environmental barrier coatings (EBCs) with mullite-Si modified HfSiO₄ as bond coating

A novel mullite-Si modified HfSiO₄ bond coating was proposed, and its performance was evaluated in a bi-layer EBCs system designed for ultra-high temperature applications. The 3 wt% mullite-10 wt% Si modified HfSiO₄ (3M10S), which exhibited a thermal expansion coefficient compatible with SiC substrate and excellent oxidation resistance, was selected as bond coating. The bi-layer EBCs of Yb₂Si₂O₇/3M10S prepared by Air Plasma Spraying (APS) exhibited significant stability when exposed to atmosphere at 1450 ℃, and no channel cracks or interfacial spalling were detected after 300 h. At 1500 ℃, though a portion of the coatings peeled off at the 3M10S/SiC interface after 100 h, the Yb₂Si₂O₇/3M10S interface remained intact. Besides, the EBCs demonstrated ultra-high temperature and prolonged stability (1450 ℃ for 100 h) against water vapour corrosion. The mullite-Si modified HfSiO₄ coating showed considerable potential for ultra-high temperature EBCs, supporting further exploration and application in extreme service circumstances.