Nanocrystalline MCrAlY bond coat for thermal barrier coating applications

This work describes recent progress in improving the oxidation behavior of the bond coat using HVOF nanostructured MCrAlY coatings. NiCrAlY powder was cryomilled and HVOF sprayed onto a Ni-based alloy. Oxidation experiments were performed on the coating to form the thermally grown oxide layer (TGO). The formation of the oxide phases on top of the bond coat after heat treatment at 1000degreesC was analyzed (morphology and composition) for different heat treatment times. In the nanostructured coatings, the presence of a homogeneous alpha-Al2O3 layer was observed. The nanostructured characteristic of the coating and the presence of Al2O3 within the cryomilled powders enhance the nucleation of the TGO alumina layer which protects the coating from further oxidation and avoids the formation of mixed oxide protrusions presented on the coating sprayed using the as-received powder. The cryomilling process of the MCrAlY powders has shown to be effective in improving the oxidation behavior of the coatings used in turbine engines applications.