High temperature oxidation behavior of nanostructured Ni–Al coatings on superalloy

The high temperature oxidation behavior of magnetron sputtered Ni–Al coatings on the superalloy substrate has been studied in the present work. The microstructural and morphological features of Ni–Al coatings were characterized by FE-SEM, AFM and XRD. Thermo gravimetric technique was used to investigate the oxidation behavior of the coatings, in air at 900 °C. The growth kinetics of oxide layers was predicted from the weight changes of the coating samples measured during oxidation. It was found that the corrosion rate of nanostructured Ni–Al coated superalloy was lower than that of the uncoated superalloy due to the formation of continuous, dense, adherent and protective oxide scale over the surface of the coatings. The morphological features and phases of the corroded coatings were used to elucidate the mechanism of high temperature oxidation. A continuous thin layer of protective oxide films such as NiO and Al2O3 has formed over the Ni–Al coatings exposed to air at high temperature, 900 °C.