Development and implementation of plasma sprayed nanostructured ceramic coatings

A broad overview of the science and technology leading to the development a nd implementation of the first plasma sprayed nanostructured coating is des cribed in this paper. Nanostructured alumina and titania powders were blend ed and reconstituted to a sprayable size. Thermal spray process diagnostics , modeling and Taguchi design of experiments were used to define the optimu m plasma spray conditions to produce nanostructured alumina-titania coating s. It was found that the microstructure and properties of these coatings co uld be related to a critical process spray parameter (CPSP), defined as the gun power divided by the primary gas flow rate. Optimum properties were de termined at intermediate values of CPSR These conditions produce limited me lting of the powder and retained nanostructure in the coatings. A broad ran ge of mechanical properties of the nanostructured alumina-titania coatings was evaluated and compared to the Metco 130 commercial baseline. It was fou nd that the nanostructured alumina-titania coatings exhibited superior wear resistance, adhesion., toughness and spallation resistance. The technology for plasma spraying these nanostructured coatings was transferred to the U S Navy and one of their approved coating suppliers. They confirmed the supe rior properties of the nanostructured alumina-titania coatings and qualifie d them for use in a number of shipboard and submarine applications. (C) 200 1 Elsevier Science B.V. All rights reserved.