Patent ID: 7407718

Claim:
A coating system on an article having a substrate formed of a silicon-containing material, the coating system comprising: an inner layer overlying the substrate and containing an alkaline earth metal aluminosilicate; an intermediate layer overlying the inner layer, the intermediate layer consisting essentially of an yttria-stabilized hafnia and at least one material selected from the group consisting of mullite, alumina, and aluminosilicates; and a top coat overlying the intermediate layer and formed of a thermal-insulating material that contains yttria and is chemically reactive with the alkaline earth metal aluminosilicate in the inner layer at temperatures above about 1370° C.; wherein the intermediate layer contacts the inner layer and the top coat, has better resistance to chemical interaction with the alkaline earth metal aluminosilicate in the inner layer than the thermal-insulating material, and has a coefficient of thermal expansion between that of the thermal-insulating material and that of the inner layer.