Abstract
The life and performances of gas turbine engines are greatly damaged by the oxidation, sulphidation, and hot corrosion of the surface layer of the blades. Recently, protective coatings of superalloys on the blades have been frequently attempted to improve them. We have designed and constructed a sputtering apparatus with two targets facing each other to deposit magnetic films on the blade alloy at a very high rate with no extreme rise in substrate temperature. Protective coatings of superalloys of the (Co, Ni)-Cr-Al-Y system of ferromagnetic properties at high rates have been made under various sputtering conditions. Films of above 4μm in thickness were deposited at a rate of about 3000Å/min with the two circular targets of the same composition and of 58mm in diameter. This deposition rate is about 30 times as high as the rate observed in conventional diode sputtering techniques. The films deposited in the argon atmosphere of the pressure below 5×10-3 Torr were adherent to the substrate and crack-free even after annealing at 900°C. In addition, the films exhibited neither any structural imperfections such as spits, flake and linear defects nor any columnar structure. These results show that this sputtering method can be practically used to deposit the superalloy films on the blades of gas turbine engine for protective coating purposes.
