The coupling effect of immersion corrosion and cavitation erosion of NiCoCrAlYTa coatings in artificial seawater

The HVOF-sprayed NiCoCrAlYTa coating is mainly composed of γ-Ni, β-NiAl and γ’-Ni3Al phases, and possesses excellent mechanical properties. The oxidized zone and its boundary are preferentially corroded during immersion corrosion. The formation of (Al, Cr)-rich passive scale is beneficial for the mechanical properties of the coating surface. Thus, the samples of S2 and S3 exhibit better apparent mechanical properties than that of S1. Especially, S2 exhibits the best mechanical properties (HIT, S and E*, etc.) and corrosion resistance. NiCoCrAlYTa coating (S1) displays great cavitation erosion resistance in the artificial seawater. The fatigue failure and spallation of the splats are the primary damage methods of the cavitation erosion of the coating. The synergy effect between corrosion and cavitation erosion would aggravate the cavitation damage of the coating. [Display omitted] •The HVOF-sprayed NiCoCrAlYTa coating is dense and uniform, and has excellent mechanical properties.•The formation of the (Al, Cr)-rich passive scale could enhance corrosion resistance of coating surface.•The fatigue failure and spallation of the splats are the prime damage methods of the cavitation erosion of the coating.•The coupling effect between corrosion and cavitation erosion would aggravate the cavitation damage of the coating. The coupling effect of immersion corrosion and cavitation erosion of HVOF-sprayed NiCoCrAlYTa coatings in artificial seawater is studied, in this work. The oxidized zone and its boundary on the coating surface are corroded, preferentially. Interestingly, an (Al, Cr)-rich passive scale forms on the coating surface after immersion corrosion, which would enhance its mechanical and anti-corrosion properties. The coating presents better cavitation erosion resistance, despite the coupling effect between corrosion and cavitation erosion causes the aggravation of the cavitation damage. The cavitation loss mainly is attributed to the fatigue failure and spalling of splats in the coatings.