Oxidation Behavior of MoSi<sub>2</sub>-CoNiCrAlY Composite Coating Prepared by Plasma Spraying

Abstract:

MoSi<sub>2</sub>-CoNiCrAlY composite coatings were deposited on GH4169 alloy with ball milled nanocrystalline powders by plasma spraying technology. Cycle oxidation behavior of coated and uncoated GH4169 alloy at 900℃ in static air was investigated. The results showed that the composite coating exhibited good oxidation resistance at high temperature, and the oxidation rate was only 1.23×10<sub>-7</sub> mg<sub>2</sub>.cm<sub>-4</sub>.s<sub>-1</sub>, which was attributed to a self-sealing oxide film SiO<sub>2</sub> with excellent protective properties formed at the early stage by oxidation of MoSi<sub>2</sub>. The oxidation resistance of the coating would be reduced by the peeling of SiO<sub>2</sub> in the later period of oxidation and the reoxidation of Mo<sub>5</sub>Si<sub>3</sub> phase to generate MoO<sub>3</sub> and MoO<sub>2</sub> gas phase as well as the internal oxidation of MoSi<sub>2</sub>.