The Composition And Performance Analysis Of Conductive Copper Coating Preparation By Spraying

At present, most of the high voltage electrical aluminum alloy switch are manufactured by using technology of surface’s copper-coating or surface’s silver plating. The surface electroplating always goes with long time, complicated technology and residues of pollutants, so it is necessary to find a method to prepare copper coating in a environmentally-friendly, simple and high efficient way.The copper coating was prepared on 5052 and 2A12 aluminum alloy’s surface by using arc spraying, plasma spraying and cold spraying technology. The microstructure of copper coating were observed by using scanning electron microscopy, optical metallographic microscope, and X-ray diffraction(XRD) analysis method. The properties of coating like resistivity and tensile were measured and tested, which was compared with the electric plating coating. It was showed that Cu2 O existed in the coating during the process of arc spraying with compressed air as gas source. Instead of using nitrogen and argon gas as gas source, there was almost no oxide exist. The copper coating prepared by plasma spraying had a good adherent on 5052 and 2A12 aluminum alloy substrate. The microstructure of copper coating presented layered and it could getting better coating when using 500 A. Ni5 Al could be used as bonding layer which made the porosity of the coating decreased, and the coating performance was improved. The copper coating prepared by using cold spraying and electroplating was thinner than by using thermal spraying. The adherence between copper coating and substrate was good. There was no layer structure which exist in the process of thermal spraying. The phenomenon of short-time oxidizing and discoloration existed in the copper coating prepared by using copper electroplating. The cell structure could be found with globular morphology covered on the surface.The bonding strength between the substrate and the copper coating prepared by using arc spraying was about 14 Mpa. When changing gas source, it has little effect on the adherence between the substrate and the coating. The porosity of copper coating prepared by using arc spraying was under 5%, which presented obvious lamellar structure. The porosity of copper coating prepared by using plasma spraying was between 8%~10%. The XRD analysis showed that cold spraying method was more suitable for the preparation of conductive cooper coating. The resistivity of different coatings was tested by using four point probe tester. It was found that the difference of resistivity of every coating prepared by plasma spraying, arc spraying and cold spraying was little, which was closed to the resistivity of pure copper. Temperature-rise test proved that the spraying coating can be used for static contact surface on high voltage switch of aluminum.