Abstract: A turbomachine component includes a silicon nitride substrate and a multi-layer coating bonded to the substrate. The coating includes an interlayer of porous fibrous silicon nitride having a density of between 85-98%. The coating also includes an outer layer formed of an oxide compound, preferably tantalum oxide, that is applied by Electron Beam-Physical Vapor Deposition. The combination of the silicon nitride interlayer and tantalum oxide outer layer serves to protect the substrate from the adverse affects of oxidation, impact by foreign objects and extreme operating temperatures.

Abstract: A bond coating is applied between a ceramic matrix composite and a insulative and abradable top coat layer. The bond coating is a slurry layer of fine particles of silicon nitride and silicon carbide suspended in a colloidal silica or zircon binder. The ratio of these materials in the bond coating should match the ratio of these in the CMC. If the CMC is SiC fibers in a SiC matrix, the slurry should be composed of SiC particles with a colloidal silica binder. High surface roughness is achieved by entrapping coarse ceramic particles into the wet bond coating slurry. Thereafter the product is heat treated to maximize bond strength and verify oxidation resistance.

Abstract: A turbomachine component includes a silicon nitride substrate and a multi-layer coating bonded to the substrate. The coating includes an interlayer of porous fibrous silicon nitride having a density of between 85-98%. The coating also includes an outer layer formed of an oxide compound, preferably tantalum oxide, that is applied by Electron Beam-Physical Vapor Deposition. The combination of the silicon nitride interlayer and tantalum oxide outer layer serves to protect the substrate from the adverse affects of oxidation, impact by foreign objects and extreme operating temperatures.

Abstract: A coating of whisker shaped beta silicon nitride grains are formed upon a silicon nitride substrate by sintering over a period of several hours, and the resulting product has a porous reaction bond coating strongly adhered to the silicon nitride substrate.