Study Of Preparation And Performance Of Ag/Cu Composite Contactor Materials

The electrical contactor is very important in high-low voltage electricalequipment, which directly influences the reliability and service lifespan of switch andelectrical operation in key components of electrical appliances, so been known as theheart of electrical appliances. Ag/Cu contactor material is a kind of composites bycoating Ag on Cu substrate, which neither forms solid solutions nor compounds. Andcombine the high conductivity, thermal conductivity, easy processing of Ag and thehigh melting point, density, wear resistance of Cu. It is well known that Cu couldabsorb amount of arc energy, lower arc temperature and galvanic corrosion andimprove the operation conditions. Usually, Ag/Cu composites for application inhigh-voltage contactor materials are fabricated by electroplating and thermal spraying.The former technique has long production cycle and badly contamination, but the laterpossess the characters of short production cycle, low cost and environmental friendly.Thermal spraying technology also has its own disadvantages, such as the weakinterfacial bonding, which is improved by use of high speed arc spraying or plasmaspraying technique.In this dissertation, Ag/Cu composites contactors were prepared by DH-X2plasma spraying (PS) and QD8high-speed arc spraying (HVAS). Arc time,breakdown voltage and arc chopping current are tested by arc ablation instrument inarc extinguishing chamber. The surface morphologies and mechanical properties ofspecimens are also analyzed after electrical breakdown of100times. The effect ofdiffusion annealing on concentration distributions at interfacial zone of Ag/Cucomposite contactors is also investigated. The main conclusions are given in thefollowing.1. PS could improve the effective thermal power of jet heating in spraying process andthe PS coatings of Ag/Cu electrical contactor are dense and uniform compared withhigh-speed arc spraying.2. The Ag/Cu electrical contactor prepared by PS has high electroconductibility, highmicro hardness of coating and good interfacial bonding of coating/substratecompared with high-speed arc spraying.3. The Ag/Cu electrical contactor prepared by PS has long lifespan, low arc choppingcurrent and high breakdown voltage compared with that prepared by HVAS. Tracesof burn stain points of contactor prepared by PS separate each other after vacuum electric breakdown.4. The coating of Ag/Cu contactor annealed at400℃produces sinteringphenomenon, coating cracks, pore reduction and conductivity increase at hightemperature. Secondary precipitation phase of Cu in the interfacial zone of Ag/Cudecreases the probability of electro scattering and increases the electricalconductivity significantly after600℃annealing. However, electricalconductivity decreases with annealing time prolonging because of the increase ofthe porosity and cracks in the Ag coating.