Oxidation behavior of near nanostructured coating developed by the HVOF process

Abstract

AbstractMicrostructured and near nanostructured Cr3C2–Ni–Cr–B–Si coatings were deposited on Inconel 718 superalloy by high‐velocity oxygen fuel thermal spray technique. The oxidation behavior of microstructured and near nanostructured Cr3C2–Ni–Cr–B–Si coated superalloy at 900°C in air for 50 cycles under cyclic heating and cooling conditions was studied. The kinetics of oxidation of both nanostructured and microstructured coated superalloy was analyzed by weight change measurement. It was noticed that the uncoated and coated alloy obey the parabolic rate law of oxidation. X‐ray diffraction, field‐emission scanning electron microscopy/energy dispersive x‐ray analysis, and elemental mapping techniques were used to analyze the oxidized samples of coated and uncoated samples. In the coated superalloy, iron, silicon, and titanium were oxidized in the inter‐splat region, whereas the splats which consist mainly of Ni and Cr remain unoxidized. Because of the formation of compact and adhesive thin NiO and Cr2O3 scale on the surface of the coating during oxidation, the developed nanostructured coated superalloy shows better oxidation resistance than the microstructured one.