Formation ofAl2O3-HfO2Eutectic EBC Film on Silicon Carbide Substrate

Abstract

The formation mechanism ofAl2O3-HfO2eutectic structure, the preparation method, and the formation mechanism of the eutectic EBC layer on the silicon carbide substrate are summarized.Al2O3-HfO2eutectic EBC film is prepared by optical zone melting method on the silicon carbide substrate. At high temperature, a small amount of silicon carbide decomposed into silicon and carbon. The components ofAl2O3andHfO2in molten phase also react with the free carbon. TheAl2O3phase reacts with free carbon and vapor species of AlO phase is formed. The composition of the molten phase becomesHfO2rich from the eutectic composition.HfO2phase also reacts with the free carbon and HfC phase is formed on the silicon carbide substrate; then a high density intermediate layer is formed. The adhesion between the intermediate layer and the substrate is excellent by an anchor effect. When the solidification process finished before all ofHfO2phase is reduced to HfC phase, HfC-HfO2functionally graded layer is formed on the silicon carbide substrate and theAl2O3-HfO2eutectic structure grows from the top of the intermediate layer.