Formation of Al2O3 - HfO2 eutectic EBC film on silicon carbide substrate

Abstract

The formation mechanism of Al2O3 - HfO2 eutectic structure, the preparation method, and the formation mechanism of the eutectic EBC layer on the silicon carbide substrate are summarized. Al2O3 - HfO2 eutectic 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 of Al2O3 and HfO2 in molten phase also react with the free carbon. The Al2O3 phase reacts with free carbon and vapor species of AlO phase is formed. The composition of the molten phase becomes HfO2 rich from the eutectic composition. HfO2 phase 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 of HfO2 phase is reduced to HfC phase, HfC- HfO2 functionally graded layer is formed on the silicon carbide substrate and the Al2O3 - HfO2 eutectic structure grows from the top of the intermediate layer.