The effect of oxidation pre-treatment on the cyclic life of EB-PVD thermal barrier coatings with platinum–aluminide bond coats

A simple method of improving the durability of EB-PVD thermal barrier coatings (TBC) based on pre-oxidation of the bond coat is described. The method produces a twofold increase in TBC cyclic life and is effective in postponing the two major types of the oxidation-induced failure typical of TBC systems with platinum–aluminide bond coats: the gradual growth of separations between the TBC and the thermally grown alumina scale (TGO), and spontaneous failure by spallation. The stable alpha-alumina scale, formed on the bond coat surface prior to TBC deposition, is less susceptible to separation along the TBC–TGO interface and also exhibits a lower growth rate in comparison with the TGO that develops on a similar bond coat without pre-oxidation. Based on these and related observations, some key principles and requirements of the oxidation pre-treatment as well as the origin of its beneficial effect are discussed.