The thermal cyclic behavior of the TBCs with the MCrAlY coating method

The rotating components in the hot sections of land-based gas turbine are exposed to severe environment during several tens thousand hours at above 1100°C operating temperature. To protect such components from high temperature oxidation, an intermediate bond coat is applied, typical of a MCrAlY-type metal alloy. Various processing methods have been studied for bond coat deposition. This study is concerned with the thermal cyclic behavior of thermal barrier coatings. The MCrAlY bond coatings are deposited by a vacuum plasma, low vacuum plasma and high-velocity oxygen fuel spray on a nickel-based superalloy (GTD-111). Thermal cyclic tests at 1100°C in still air for various periods of time were used to evaluate the thermal cyclic resistance of the TBC coating with the various processing sprayed bond coating layer. The microstructure and morphology of as-sprayed and of thermal cycled coatings were characterized by scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The order of thermal cyclic resistance was YSZ-VPS bond coat, YSZ-LVPS and YSZ-HVOF. The influence of bond coat spray methods on durability of TBCs is discussed.