| Material transfer caused by electrical arcing is a problem for electrical contacts used in electrical load condition. Since arc discharges involve the evaporation and sputtering of the electrodes, they will cause the material to transfer between the electrodes or to be lost from the electrodes, thus leading to contacting problems or ending the life of the contacts. The effects of the arc discharge on material transfer have been a long-interested topic both in physics and electrical engineering. And the phenomena of arc discharge were further studied with the demands of engineering long lifetime in communication and high reliability in control, such as mechanism of arc erosion, phenomena of fusion welding. But further work is still needed not only to make sure how the material is transferred during arcing, and what parameters govern the transfer process, but also to give a general picture of arc erosion in electrical contacts. Meanwhile, the universal rules are needed to be established to explain the phenomena of arc discharge and arc erosion.In this paper, the arc erosion of Ag-La2Ni04electrical contacts is studied in some aspects, such as microstructure, surface profile, simulation of the temperature field of the contacts. We aimed to enrich the research productions on electrical contacts, and lead a foundation for a general understanding the behavior of arc erosion.Results showed that the direction of material transfer was strongly depended on performance of the electrical contact materials and load condition. When the voltage is8V DC, only slight arc can be seen and hardly any splash; a preiection and pit are left on the cathode and anode surfaces after the experiment and metallic luster are visible on both surfaces. Under such a low voltage, the molten pools produced by joule heat are limited and the molten bridges are little; further more, the first ionization potential of Ag, La, Ni, Sn, O, N are7.576eV,5.577eV,7.635eV,7.344eV,13.618eV,14.534eV respectively, so short metallic phase arc can steadily exist and there is hardly any gaseous phase arc. Therefore, under this condition, the material is transferred from anode to cathode, and is obviously caused by the metallic phase arc.When the voltage is18V DC and the current is below20A, the gaseous phase is on the leading position. After balance the process of materials transferred from anode to cathode caused by the metallic phase (and the total transfer are less than the material transferred under the condition of8V DC), a comprehensive result that the materials transferred from cathode to anode can also be brought about; when the current is higher than20A, the violently raised temperature of the electrode materials, surface evaporation and molten drop splash are the main factors for the material transferred from anode to cathode.To investigate the difference between the Ag-La2NiO4composite contact and the commonly used Ag-SnO2composite contact, the contact resistance, material transfer and corrosion features of the two materials are studied. The results show each has its merits:the Ag-La2NiO4composite contact is suitable to service under DC30V low load and carry out a closing-breaking circulation for a longtime.The hypothesis that oxide layer could protect electrode surface and reduce material transfer was putted forward. The rate of input coefficient f was confirmed for anode0.5≤f≤1.0, and for cathode0≤f≤0.5. Electrical field between anode and cathode and numerical value of input coefficient f are two important research aspects in the future. |
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