Evaluation of High Temperature Oxidation Behaviour of Nanostructured Cr/Co-Al Coatings

The high temperature oxidation behavior of sputtered Cr/Co-Al coatings fabricated by DC/RF magnetron sputtering on a superalloy substrate has been studied in the present work. The microstructural features and phase formation of the as-deposited coatings were characterized by FE-SEM, AFM, and XRD, respectively. Weight-change measurements were made to calculate the cyclic oxidation kinetics of the coated superalloy exposed to air at 900 degrees C. It was observed that the corrosion rate of sputtered Cr/Co-Al coated superalloy is lower than that of the uncoated superalloy owing to the formation of continuous, dense, adherent and protective oxide scales over the surface of the coatings. The protective oxide scales in the corroded coatings were basically the thin layer of Cr2O3, CoO, Al2O3 and CoCr2O4, which provide protection to the base superalloy at high temperature.