Hybrid intermetallic Ru/Pt-modified bond coatings for thermal barrier systems

NiAl-based bond coatings for thermal barrier coating (TBC) systems containing varying amounts of Ru and Pt have been investigated. The addition of Ru to bulk NiAl has shown substantial increases in the creep strength of these aluminide materials, while Pt-modifications are known to improve the oxidation resistance of NiAl. The oxidation and interdiffusion behavior of these hybrid Ru/Pt bond coat systems are compared to conventional Pt-modified aluminide bond coats. The Ru/Pt-modified aluminide bond coats demonstrate cyclic oxidation lives comparable to those of Pt-modified aluminide bond coatings. These hybrid Ru/Pt-modified bond coats exhibit better creep properties than traditional Pt-modified coatings and suppress the rumpling mechanism typically responsible for the spallation of TBC from Ni(Pt)Al bond coatings. The evolution of coating microstructures at various stages of cyclic life was studied, and phase equilibria issues relevant to the fabrication and oxidation behavior of these multilayer systems are discussed.