The Vapor Deposition and Oxidation of Platinum- and Yttria-Stabilized Zirconia Multilayers

Abstract

Attempts to increase the gas temperature within gas turbine engines are driving the development of thermal barrier coatings that reduce superalloy component oxidation rates by disrupting thermal transport processes. Novel metal–ceramic multilayer's combining thin metal layers with low thermal conductivity oxide ceramics offer a potential approach for impeding both the radiative and conductive transport of heat to a component surface. A gas jet-assisted vapor deposition technique has been modified and used to experimentally explore the deposition model thermal protection system consisting of platinum- and yttria-stabilized zirconia (YSZ) multilayers. Coatings containing one, three and four platinum layers in 7YSZ have been deposited on NiCoCrAlY bond-coated Hastelloy X substrates and compared with conventional 7YSZ monolayers deposited on the same bond-coated substrates. The multilayer samples have been thermally cycled to 1100°C and found to be less susceptible to delamination failure than the conventional coatings. Their bond coat oxidation rate at 1100°C was also measured and discovered to decrease as the number of platinum layers was increased. The observations are consistent with a retarded inward diffusion of oxygen by the platinum layers.