Effect of pre-oxidation on the isothermal and cyclic oxidation behaviour of cold-sprayed NiCoCrAlY coating

Abstract

The effects of vacuum pre-oxidation treatment on the isothermal and cyclic oxidation behaviour of a cold-sprayed NiCoCrAlY coating are investigated. It is found that the cold-sprayed NiCoCrAlY coating has a dense structure with low oxygen content and consists of a single γ-matrix phase. A uniform and continuous α-Al₂O₃ layer with a thickness of 0.47 ± 0.02 μm can be obtained by pre-oxidation treatment in a vacuum environment. The pre-oxidation treatment decreases the growth rate of thermally grown oxide by the formation of Al₂O₃ with larger grain sizes and thus improves the thermal cyclic life of coating. Surface-geometry imperfections are the source of initial spallation of thermally grown oxide.

Keywords:

• NiCoCrAlY
• Cold spray
• Pre-oxidation
• Oxidation
• Thermally grown oxide