Study of Nanostructured CeO₂ Coatings on Superalloy

Abstract

Nanostructured CeO₂ coatings on Superni-718 substrate were deposited by electroless process in the present work. Microstructure and cyclic high-temperature oxidation behaviour of nanostructured CeO₂ coatings on Superni-718 substrate was investigated. Cyclic high-temperature oxidation tests were conducted on uncoated and coated samples at peak temperatures of 900°C for up to 50 thermal cycles between the peak and room temperature. The results showed that the coated sample has higher oxidation resistance as compared to bare substrate at 900°C. The external scale of the coated sample exhibited good spallation resistance during cyclic oxidation testing at both temperatures. The improvement in oxide scale spallation resistance is believed to be related to the fine-grained structure of the coating. The oxidation results have shown the improved oxidation resistance of the CeO₂ coating on superalloy as compared to bare substrate up to 50 cycles. The relevant oxidation mechanisms are discussed.

Keywords:

• Electroless process
• Nanostructured CeO₂ coatings
• Cyclic high-temperature oxidation
• Scale spallation

Acknowledgment

One of the authors, Dr Atikur Rahman, would like to thank Prof (Dr) Rajat Gupta, Director, National Institute of Technology Srinagar Hazratbal, Kashmir 190006, India, for their financial support to this work (Order No. 189 of 2012, Dated 04–04–2012).