University of California Energy Institute

Thermal barrier coating (TBC) systems protect turbine blades against high-temperature corrosion and oxidation. They consist of a metal bond coat (MCrAIY, M = Ni, Co) and a ceramic top layer (ZrO2/Y2O3). In this work the oxidation behavior of conventional and nanostructured HVOF NiCrAIY coatings has been compared. Commercially available NiCrAIY powder was mechanically cryomilled and HVOF sprayed on a nickel alloy foil to form a nanocrystalline coating. Free-standing bodies of conventional and nanostructured HVOF NiCrAIY coatings were oxidized at a 1000ºC for different time periods in order to form the thermally grown oxide (TGO) layer. The experimants show an improvement in oxidation resistance in the nanostructured coating when compared to that of the conventional one. This behavior is a result of the formation of a continuous AI2O3 layer on the top surface of the nanostructured HVOF NiCrAIY coating. This layer protects the coating from further oxide protrusions present in the conventional coating.