Fabrication And Application Of Enamel Heat Protective Coating On K424 Alloy

At present, with the development of the aero engine with large thrust-weight ratio, harms to the hot end components subjected to a high temperature oxidation as well as high temperature corrosion has become more and more severe. In order to increase the resistance to high temperature oxidation, a coating on the expansion nozzle and hot end surface of the parts is necessary. In order to improve the high temperature performance of K424 alloy hot end components, the preparation process of a protective coating, and performance evaluations as well as its application in aircraft engine were carried out in this research.Through the analysis of the coating structure and performance testing, optimized parameters for the multi arc ion plating and enamel coating preparation were obtained. The main components of the enamel coating are amorphous glass, and Al2O3、Zn Al2O4、Na(Al Si3O8) were formed in the interface. Optimized parameters for the coating were verified through the constant temperature oxidation performance contrast between alloy matrix and coated sample. And the coating with a superior high temperature oxidation resistance can be used for the product.According to the design standard of the performance test methods and technical indexes, Ni Cr Al Y bonding layer fabricated by multi arc ion plating for various properties of composite heat enamel coating were tested. The test results show that the coating has excellent resistances to thermal shock, bending, salt fog, gas hot corrosion and high temperature oxidation. In addition, the influence of the coating on the mechanical properties of the substrate can be neglected. The weight loss of the composite heat enamel coating reaches equilibrium after 25 h, and its value is about 1g/m2, which is less than 20% of that for the substrate. As a consequence, high temperature composite enamel coating can meet the requirement of K424 alloy parts protection technology.Many practical components such as adjust pieces, are plated with this composite enamel coating, and installed into a certain aero engine. After the engine test evaluation for a long time, the inspection of the engine shows that the erosion of adjust pieces is negligible. At present, the plating of enamel coating have been a standard process of many practical components.