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Preparation and arc erosion resistance of Ag/ Ti2Snc composites

2021-02-18

Low-voltage switches are widely used in aerospace, rail transportation, electronic and electrical fields, etc. The reliability of the heart component "electric contact" which is subjected to current impact largely determines the service life of the switch. Since the middle of last century, Ag/ CDO electric contacts with outstanding arc erosion resistance have been favored. However, the toxic CD vapor released in the process of electrical contact poses a serious threat to human body and the environment, so it is urgent to replace the CD-free electric contact material. So far, Ag/SnO2, Ag/ZnO, Ag/Ni, Ag/C and other non-toxic contact materials still have a variety of problems in the aspects of workability, contact resistance, temperature rise, arc erosion resistance, etc., and can not fully replace Ag/ CDO. Therefore, it is one of the key problems in this field to find a new environment-friendly silver-based reinforced phase material for electrical contacts.In recent years, MAX phase materials with the dual characteristics of cermet have shown great potential in the fields of electrical conductivity, thermal conductivity, friction, corrosion resistance and other applications. In the MAX phase in the family, Ti2SnC processing performance is good, high thermal conductivity (43 W/m, K), and the lowest resistivity (0.22 mu Ω, m), fully agree with the basic properties of the Ag enhancement phase material requirements.
Ag/Ti2SnC composites organization even, relative density of 93%, moderate hardness (62-76 HV1), low resistivity (0.14 to 0.32 mu Ω, m). The wetting experiment at high temperature (1025℃) showed that Ag and Ti2Snc had good wettability (contact Angle ~14°), which was conducive to the uniform distribution of Ti2Snc in Ag group and the interface bonding between them.Under the condition of 400V/100A/ 50Hz /AC3 for 2000 times, the shape of Ag/ 10Ti2Snc composite electric contacts remains intact, and the erosion area is smaller than that of commercial Ag/ CDO electric contacts, while the surface of electric contacts with high Ti2Snc content is damaged by arc relatively seriously. The microstructure of Ag/ 10Ti2Snc and Ag/ 20Ti2Snc electric contact surface erosion zone and transition zone after arc erosion were analyzed by SEM and EDS, and the interaction characteristics between arc and Ag matrix and Ti2Snc particles were identified, including silver ball, crack, molten pool, hole, arc pit, slightly corroded Ti2Snc, etc. Combined with the results of cross section metallography, scanning electron microscopy, energy spectrum and material loss, it is found that the silver base contact with low Ti2Snc content is better than the silver base contact with high Ti2Snc content. In the process of electric contact, the high temperature rise is effectively avoided, and the erosion damage of the enhanced Ti2Snc particles caused by high arc temperature is reduced.Combined with XRD and EDS results, it is found that Ti2Snc is mainly destroyed by slow oxidation resulting in structural disintegration under high arc temperature, and the main destruction products are titanium oxides. The study explores the MAX phase material potential applications in the field of silver based electric contact, early results show that the strengthening phase material Ti2SnC content is appropriate, has good conductivity, thermal conductivity, and can be compared with the commercial Ag/CdO shoulder arc erosion resistance, it is a good CdO alternative candidate material, has the potential value of the research and application.

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