Ensuring the Quality of the Surface of Turbine Blades by the Application of Protective Diffusion Coatings

Abstract

Scanning electron microscopy and x-ray microanalysis were used to study defects in protective diffusion coatings on the blades of gas-turbine engines. It was established that the defects in the coatings on the flowthrough surface of the middle of the blades are caused by the entry of corundum particles into the surface of the heat-resistant alloy during the pneumoabrasive treatment administered to the blade surface. Defects are formed in the coatings on the inside surfaces of the cooled channels due to the use of an oxidizing atmosphere in the gas-circulation chromizing-aluminizing operation and leaching of carbides from the alloy when ceramic cores are removed from the blade castings. It is shown that the technology of hydrothermal autoclave leaching in a protective argon atmosphere makes it possible to remove corundum particles embedded in the flow-through surface of the middle of the blades and properly prepare the surface of the internal cooled channels for the application of quality protective diffusion coatings.