Ceramic coatings on ceramic for improved oxidation-corrosion resistance
Date of Original Version
Thin films of covalent ceramics were deposited onto a variety of hot-pressed and pressureless sintered silicon nitride substrates to reduce oxidation-hot corrosion of the underlying material and to minimize pitting and localized attack of the substrate. The extent of oxidation-corrosion of the hot-pressed and pressureless sintered nitride ceramics in the presence of thin films of sodium sulfate at 1000 °C was dependent on the out-diffusion of cations from the intergranular phase into the predominantly silica corrosion product. Silicon nitride, silicon oxynitride, silicon carbide and silicon aluminum oxynitride films were deposited by reactive r.f. sputtering to form an effective diffusion barrier to cation migration. The amount of protection provided by these covalent ceramic coatings was dependent on the composition, microstructure and phase distribution within the coating. Crystallization of the as-deposited films was performed by conventional furnace heat treatment. Corrosion rates of the silicon nitride ceramics protected with covalent ceramic coatings were significantly reduced. Pitting of the ceramic substrates was also significantly reduced when protective coatings were applied. © 1988.
Surface and Coatings Technology
Davies, G. B., and O. J. Gregory. "Ceramic coatings on ceramic for improved oxidation-corrosion resistance." Surface and Coatings Technology 36, 1-2 (1988): 419-432. doi:10.1016/0257-8972(88)90170-3.