Patent ID: 6974637

Claim:
An article comprising: a substrate formed of a metal alloy containing ruthenium above an amount that might be unintentionally present as an impurity; and a coating system on a surface of the substrate, the coating system comprising an aluminum-containing bond coat on the surface of the substrate and a ceramic coating bonded to the substrate by the bond coat, the bond coat being substantially free of ruthenium except for ruthenium that has diffused into the bond coat from the substrate; wherein the bond coat comprises an overlay coating consisting essentially of intermetallic phases and contains, in atomic percent, about 30% to about 60% aluminum, optionally up to about 10% chromium, 0.1% to about 1.2% of at least one element chosen from the group consisting of zirconium, hafnium, silicon, and titanium, the balance being essentially nickel.