MoSi2-Si3N4 COMPOSITE COATING LAYER AND MANUFACTURING METHOD

Japanese Patent JP3793157

B2

PROBLEM TO BE SOLVED: To provide an MoSi2-Si3N4 composite coating layer which is formed on a substrate material composed of molybdenum, a molybdenum alloy, molybdenum- coated niobium or a molybdenum-coated niobium alloy and by which repeated-oxidation resistance and low temperature oxidation resistance can be improved and the high- temperature mechanical properties of a coating layer can be improved, and also to provide its manufacturing method. SOLUTION: The method for manufacturing the MoSi2-Si3N4 composite coating layer comprises (1) a process where nitrogen is vapor-deposited onto the surface of the substrate material to form an Mo2N diffusion layer and then silicon is vapor- deposited onto the surface of the Mo2N diffusion layer to form the MoSi2-Si3N4 composite coating layer; and (2) a process where silicon is vapor-deposited onto the surface of the substrate material by a chemical vapor deposition method (CVD) to form an MoSi2 diffusion layer, the MoSi2 diffusion layer is heated under a high-purity hydrogen or argon atmosphere to undergo phase transformation into an Mo5Si3 diffusion layer, nitrogen is vapor-deposited onto the surface of the Mo5Si3 diffusion layer by CVD to form an Mo2N-Si3N4 composite diffusion layer, and silicon is vapor-deposited onto the surface of the Mo2N-Si3N4 composite diffusion layer to form the MoSi2-Si3N4 composite coating layer.