Reactive sputter-coated reaction-bonded silicon nitride
A coating technique was developed to provide high temperature oxidation resistance and hot corrosion resistance to gas turbine components made of reaction-bonded silicon nitride. Thick coatings of reactively sputtered silicon nitride were deposited onto reaction-bonded silicon nitride surfaces to form an effective oxygen diffusion barrier by eliminating all potential short-circuit paths. To accomplish this, hard crystalline coatings were produced by subsequent heat treatment of the as-deposited silicon nitride. The as-deposited and annealed films were characterized by a variety of methods to determine the phase content, extent of crystallinity, grain size and morphology. With this coating technique, the oxidation of the underlying silicon nitride was substantially reduced in the temperature range 1000-1200°C. © 1982.