Fabrication of EBC System with Oxide Eutectic Structure

In this paper, the fabrication method and the formation mechanism of a new EBC system with Al2O3-HfO2 eutectic structure are discussed. A rapid heating process is required for the fabrication of Al2O3-HfO2 eutectic EBC film on silicon carbide substrate. Optical zone melting method was applied for the fabrication method of the eutectic EBC film. At high temperature under light focusing, a small amount of silicon carbide decomposed into silicon and carbon and each component of the Al2O3 and HfO2 in molten phase reacts with the free carbon. And a small amount of Al2O3 component reacts with the free carbon and vaporized from the molten phase. The composition of the molten phase becomes H HfO2 rich. HfO2 phase is also reacts with the free carbon and HfC phase is solidified on the silicon carbide substrate. A high density intermediate layer consisted of HfC is formed. 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. The Al2O3-HfO2 eutectic structure grows from the top of the intermediate layer.