Abstract: A thermal barrier coating system and a method for forming the coating system on an article designed for use in a hostile thermal environment, such as superalloy turbine, combustor and augmentor components of a gas turbine engine. The method is particularly directed to a coating system comprising an APS bond coat on which a thermal-insulating APS ceramic layer is deposited, wherein the oxidation resistance of the bond coat and the spallation resistance of the ceramic layer are increased by diffusing platinum, palladium, hafnium, rhenium and/or rhodium into the bond coat. The diffusion process is performed so as not to alter the surface roughness of the bond coat, which is maintained in a range of about 200 to about 500.mu. inch Ra.