Enhancing hot oxidation resistance of the HVOF- sprayed NiCoCrAlTaY coating by alumina nanoparticles via a modified suspension route

The effect of alumina (Al2O3) nanoparticles on the hot oxidation behavior of NiCoCrAlTaY coating is investigated. High velocity oxygen fuel (HVOF) technique was employed to de-posit coatings on a single crystal CMSX-4 Ni-based superalloy. Different amounts of a-Al2O3 nanoparticles (3, 6 and 9 wt%) were added to NiCoCrAlTaY powder via a modified sus-pension route. By this modification, the Al2O3 nanoparticles were adhered on the surface of the atomized metallic NiCoCrAlTaY powders with a relatively uniform distribution. The composite powder was then sprayed on the superalloy substrate by an industrial HVOF route. The cyclic hot oxidation resistance of the coatings was evaluated at 1100 degrees C. Results showed that the coating with 6 wt% nano-Al2O3 experienced significantly better oxidation performance. The presence of nano-Al2O3 in the coating accelerated the formation of a-Al2O3 dense oxide layer and, thereby, delayed diffusion of other elements to the surface. Adding more Al2O3 nanoparticles up to 9 wt% led to an increase in porosity and surface roughness of the coating which decreased oxidation resistance.(c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).