Patent ID: 8084094

Claim:
A process of applying a coating system on a surface of a substrate of an article, the substrate being formed of a nickel-base alloy containing at least one refractory metal in an amount sufficient to render the substrate susceptible to a gamma/gamma-prime inversion and susceptible to forming a secondary reaction zone (SRZ) in which deleterious topologically close-packed (TCP) phases form, the process comprising: forming a stabilizing layer on the surface of the substrate, the stabilizing layer consisting of at least 75 atomic percent of at least one platinum group metal chosen from the group consisting of platinum, rhodium, iridium, and palladium, optionally up to about 25 atomic percent of one or more intentional additions chosen from the group consisting of nickel, cobalt, chromium, aluminum and ruthenium, and incidental impurities; and depositing an aluminum-containing overlay coating on the stabilizing layer such that the stabilizing layer is between the overlay coating and the substrate, the overlay coating being a nickel aluminide intermetallic overlay coating of predominantly the beta phase and containing aluminum in an amount greater by atomic percent than an amount of aluminum in the metal alloy of the substrate; and then subjecting the article, the overlay coating, and the stabilizing layer therebetween to a temperature that renders the substrate susceptible to the gamma/gamma-prime inversion and susceptible to forming the SRZ; wherein neither the stabilizing layer nor the overlay coating undergo a diffusion treatment to diffuse the stabilizing layer and the overlay coating into the substrate, the stabilizing layer has a thickness of at least about three micrometers, separates the overlay coating from the substrate and consists of the at least one platinum group metal, optionally the one or more intentional additions, and the incidental impurities, and the substrate is essentially free of an SRZ that is deleterious to the mechanical properties of the metal alloy.