Degradation Behaviour of Nanostructured CeO2 Films on Superalloy
The present work proposes the development of nanostructured oxidation barrier film on nickel-based superalloy Superni 750 by electroless process. The oxidation barrier film is intended to increase the life of the thermal barrier coatings by acting as a diffusion barrier to the movement of anions and cations. Cerium oxide was deposited on the substrate at different concentrations. Cyclic high-temperature oxidation in air was conducted at 900 °C for 100 thermal cycles. The nanostructured CeO2 film on Superni 750 substrate was characterized using SEM/EDS and XRD, before and after oxidation. X-ray photoelectron spectroscopy (XPS) was carried out to determine the oxidation state of cerium in the scale formed after oxidation. The coated samples have shown to exhibit improved oxidation resistance as compared to the bare substrate at 900 °C. It was also observed that increasing the Ce ion concentration in the film improves the oxidation resistance by impeding the movement of Ti, Cr and Ni ions (substrate elements) along the grain boundaries in the superalloy. The scale formed on coated samples was found to have a good spallation resistance.
KeywordsElectroless process Nanostructured CeO2 coatings Cyclic high-temperature oxidation Superalloys
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