Cyclic Oxidation Behavior of Electrodeposited Ni3Al–CeO2Base Coatings at 850°C

Abstract

The cyclic-oxidation behavior of electrodeposited pure, nano CeO2 (9–15 nm)- and micron CeO2 (5 μm)-modified Ni3Al coatings on Fe–Ni–Cr substrates have been investigated at 850°C for periods up to 1000 hr. All the coatings showed good oxidation resistance in the early stage, but decreased oxidation protection during the intermediate stage of exposure. The formation of slow-growing γ-Al2O3 scales provided the coatings with good oxidation resistance in the early stage. However, a high volume fraction of pores in the coatings decreased oxidation resistance in the intermediate stage by forming oxidized channels between the pores. After long-term exposure, however, the pores in the coatings were healed by coating–substrate interdiffusion, and an improvement in cyclic-oxidation resistance was observed. The CeO2 particles in the coating affected the stability of the protective oxide scale and the pore-healing behavior. The most significant effect was from nano size CeO2 particles, which improved the stability of the protective oxide scale but retarded the rate of pore healing.