Research On Process And Performance Of Yttrium-modified Aluminide Coatings By CVD Methods

The working temperature of aviation turbine engine can be highly improved by using internal cooling channels blades, but the high temperature oxidation and hot corrosion happened in the surface of internal cooling channels is the key factor that limits the working life of aviation turbine engine. The service life of aviation turbine engine can be effectively improved by deposition aluminde coating on the surface of internal channels by chemical deposition(CVD) methods. Compared with simple aluminide coating, modified aluminide coating has better high-temperature oxidation resistance and hot corrosion resistance. So the study of modified aluminide coating preparation method is the hot topic right now.In this topic, the preparation process of Y-modified aluminide coating was studied by analyzing and calculating the thermodynamics and dynamics process. Experiment was used to verify the designed proscess. The experiment result shows that the Y-modified aluminide coating can be successfully obtained on the surface of Inconel 718 Ni-based super alloy by using 950? of reaction temperature, 400 mbar of reaction pressure and Al-Y impregnant which mole ratio of Al and Y is 8:2.The component and structure of coating and the functional mechanism of Y was studied by various examining methods. The result shows that Y can promote the interdiffusion of Al and Ni, increase the content of Al in coating and decrease the microhardness of coating. The Al and Y content in coating increased with reaction time went on, and the structure of coating changed from single ?- Ni Al phase to ?- Ni Al and Ni5Al3 mixed phase.High temperature oxidation test was also carried out at 1100 ?with oxidation of 60 hours in this topic. The results showed that the oxidation resistance of Y-modified aluminide coatings was superior to that of simple aluminide coatings. The high-temperature oxidation resistance performance of Y-modified coating can be promote with the increase of Y.