Corrosion resistance and erosion-corrosion wear performance of HVOF sprayed Cr3C2-NiCr coating in NaOH solution

The work aims to analyze the corrosion resistance and erosion-corrosion wear performance of HVOF sprayed Cr3C2-NiCr coating in alkaline solution, and reveal the mechanisms of corrosion and erosion-corrosion wear. Cr3C2-NiCr ceramic coating was deposited on the surface of 45# steel by high velocity oxy-fuel spraying (HVOF). The microstructure, microhardness, corrosion resistance, erosion-corrosion wear performance in the alkaline environment, weight loss and surface morphology were tested by optical microscopy (OM), microhardness tester, corrosion performance test bench in alkaline environment, electrochemical analyzer, erosion-corrosion wear tester, electronic balance and scanning electron microscope, respectively. Cr3C2-NiCr coating exhibited a typical layered structure and pores and oxides were randomly distributed among the coating. The porosity and microhardness of the coating were 1.3% and 817HV0.1 on average, respectively. In the NaOH solution with pH=11, the electrochemical corrosion potential of Cr3C2-NiCr coating was -0.38 V. The oxides produced by the corrosion reaction could effectively prevent the corrosion from proceeding. During long-term immersion, the corrosive medium underwent a corrosion reaction with substrate after penetrating into the coating and substrate through the cracks or penetrating pores. The corrosion products formed by the corrosion reaction were gradually accumulated and discharged to the surface of the coating, thus eventually forming a bulky and flocculent corrosion product. In the alkaline corrosive environment, corrosion medium could exacerbate material consumption in erosion wear. Under the same conditions, the weight loss of erosion-corrosion wear of coating was significantly less than that of substrate material. The main failure mechanisms of erosion-corrosion wear of Cr3C2-NiCr coating were falling of corrosion products, spalling of hard particles, abrasion of binder phases, falling of the defects due to fatigue cracks. In alkaline environment, Cr3C2-NiCr coating has strong corrosion resistance. The corrosion medium can accelerate the erosion process of the coating, and the surface of the coating after wear is a non-smooth surface. Due to the non-smooth surface, the coating has excellent erosion wear resistance. Therefore, Cr3C2-NiCr coating can significantly improve the comprehensive performance of the substrate surface. © 2019, Chongqing Wujiu Periodicals Press. All rights reserved.