Improving Wear-resistance Of Mould Used On Casting By Mono-Plating Ni-Fe Alloys

This paper presents a new way to prepare wear-resistance Ni-Fe alloy coating for a crystallizer used in continuous casting and the wear mechanism of the alloy coating has been investigated. A bath composition, a brightener and the operating conditions have been determined through systematic research. The optimum Ni-Fe alloy coating contains 3 to 5 percent Fe.The Ni-Fe coating has excellent wear resistance, about two times as high as that of the pure Ni coating. The properties of Ni-Fe alloy coating are superior to that of the normal all-nickel systems. The deposits are higher in hardness, wear resistance, heat impact resistance and a strong adhesion to the substrate cause the thermal expansion coefficient of Ni-Fe coating is very close to that of the cupper alloy. Thus Ni-Fe coating is very suitable for a crystallizer used in continuous casting. In comparision to pure nickel coating in the same thickness, the service life of the crystallizer by nickel-iron plating twice of pure nickel coating.EDS, XRD and SEM were employed to analyze the content arid pattern of oxidation layer. It was found that, the high-temperatureoxidation of Ni-Fe alloy plating obeys parabola law. Furthermore, the rate of oxidation increased with Fe wt% and the temperature. FeiOj content in the layer increases with the Fe wt% in plating. At the higher temperature, the main content in the layer was NiO. However, at the lower temperature, the major content was FeOs. On the basis of the content and the microstructure of the layer, this paper attempt to explore the mechanism of the high-temperature of Ni-Fe alloy plating and its oxidation resistance.The structure of nickel-iron alloy coating has been analyzed by means of XRD. The change in microstructure and structure of the coating before and after wear have been investigated SEM .The difference between nickel-iron alloy coating and nickel coating in wear-resistance is due to the effect of iron upon the oxidation and its products. Measures for improving the wear-resistance are proposed according to the wear mechanism of nickel-iron coating.