Process dependence of Ir-based bond coatings

The process dependence of Ir-based-alloy-coated Ni-based single crystal superalloys was investigated. An Ir-4 at%Ta alloy, 10 μm thick, was coated on a Ni-based single crystal superalloy TMS-82+, by means of magnetron sputtering deposition (SD) and electron beam physical vapor deposition (EB-PVD). X-ray analysis revealed that the grain size of the as-SD-coated layer (∼20 nm) has five times smaller than that of the as-EB-PVD coated layer (∼100nm), and the SD-coated specimens showed more rapid outer diffusion of Ni and Al from the substrate after annealing, than the EB-PVD-coated ones. On the other hand, the aluminizing treatment reduces the differences between the SD coated and EB-PVD coated specimens in terms of compositional distribution and oxidation resistance. This study also revealed that even without aluminizing, the simple annealing treatment enhances the oxidation resistance of the Ir-4%Ta-coated TMS-82+.