Uniform Microstructure and Excellent Corrosion Resistance of HVOF-Sprayed CoCrNi Medium-Entropy Alloy Coating in Fluoride Ion Environment

다국어 초록 (Multilingual Abstract)

To solve the corrosion problem of the copper plates caused by fluoride ions, the Ni55 and CoCrNi medium-entropy alloycoatings were prepared via high-velocity oxygen fuel technology. The corrosion resistance of the Ni55 and CoCrNi coatingsin NaF solution was compared through electrochemical experiments and immersion corrosion experiments. The Ni55coating contained complex precipitated phases, resulting in preferential corrosion at the phase boundaries between the γ-Nisolid solution and the precipitated phases. The composition of the CoCrNi coating was more homogeneously distributed,and mainly uniform corrosion occurred. The corrosion products of the two coatings in the NaF solution were both complexescomposed of metal oxides and fluorides. Compared with the Ni55 coating, the passive film formed on the CoCrNi coatinghad a more uniform and protective property; therefore, the CoCrNi coating had better corrosion resistance. This researchcan pave a pathway for developing coating on copper and its alloys with excellent corrosion resistance.