Plasma sprayed thermal bond coat system

Abstract

A method for forming a thermal barrier coating system on an article subjected to a hostile thermal environment, such as the hot gas path components of a gas turbine engine. The coating system is generally comprised of a ceramic layer and an environmentally resistant beta phase nickel aluminum intermetallic (β-NiAl) bond coat that adheres the ceramic layer to the component surface. A thin aluminum oxide scale forms on the surface of the β-NiAl during heat treatment. An additional layer of diffusion aluminide may can be formed underlying the ceramic layer. The β-NiAl may contain alloying elements in addition to nickel and aluminum in order to increase the environmental resistance of the β-NiAl. These elements include hafnium, chromium and zirconium and increase the oxidation resistance of the β-NiAl. The β-NiAl is supplied as a powder having a size in the range of 20-80 microns. The β-NiAl powder is applied using air plasma spray techniques to produce a surface having a roughness of 400 microinches or rougher. The ceramic top coat, a stabilized zirconia, typically ytrria-stabilized zirconia, can be applied using inexpensive thermal spray techniques to greater thicknesses than achievable otherwise because of the rough surface finish of the underlying β-NiAl bond coat. Alternatively, the β-NiAl coat can be used as an environmental coating without application of an overlying ceramic topcoat.

Dependencies are inferred from the claim text.