Study On Preparation And Properties Of Green Silver-based Coatings With High Sulfur Resistance

The silver-based coatings have been widely used in the surface coatings of electrical contact material for outdoor high-voltage isolation switch,due to its excellent electrical conductivity,heat conduction and wear resistance etc.In this paper,the pure silver coating,silver/graphite and silver/graphene composite coatings were prepared by common and vacuum cyanide-free electrodeposition,respectively.The composition,morphology and structure of silver-based coatings were investingated by X-ray diffraction?XRD?,energy dispersive spectroscopy?EDS?,field emission scanning electron microscope?FESEM?,X-ray photoelectron spectroscopy?XPS?and transmission electron microscopy?TEM?etc.The contact resistance,hardness,thermal conductivity,wear resistance and sulfuration resistance of silver based-coatings were investigated by contact resistance measuring instrument,thermal conductivity meter,wear test and sulfur resistance test,respectively.With increasing the amount of graphene in the plating bath,the graphene content in the silver/graphene composite coatings prepared by common electrodeposition method increases,hardness and contact resistance changes little,wear rate decreases and thermal conductivity increases.The silver/graphene composite coating which was prepared in plating baths with graphene content of 70 g/L achieved the best performance,with hardness of 115 HV,contact resistance value of 42??,wear rate of 3.237×10^-11mm³·N^-1·m^-1and thermal conductivity of 388.1 W·m^-1·k^-1.Compared with pure silver coating,the contact resistance of this silver/graphene composite coating changed little,hardness increased by 24.6%,wear rate decreased by 50.2%and thermal conductivity increased by 17.3%.The pure silver,silver/graphite and silver/graphene composite coatings have been prepared in different deposition current densities by common electrodeposition method measuring their sulfur resistance in 5%Na₂S solution.It was found that the pure silver coating prepared by using a current density of 0.4 A/dm² has the best sulfur resistance.After 6 hours of sulfur resistance test,the pure silver coating showed a slight discoloration,but the silver/graphite and silver/graphene composite coatings have more serious discoloration than pure silver coating.The pure silver,silver/graphite and silver/graphene composite coatings have been prepared in 0.4A/dm²deposition current densities by vacuum electrodeposition method,and the coating color does not change after sulfur resistance test for 12 hours,5 minutes and 1hour,respectively.The silver-based coatings prepared by vacuum electrodeposition method have more excellent sulfur resistance compared with that prepared by common electrodeposition method.In this paper,the sulfur resistance of pure silver coatings prepared by self-made and domestic manufacturers are as followed:self-made pure silver coating prepared by vacuum electrodeposition?self-made pure silver coating with surface protection prepared by common electrodeposition?pure silver coating which prepared by Siemens AG?pure silver coating prepared by Tai Kai Co.Ltd?self-made pure silver coating prepared by common electrodeposition.