Enhancement of Arc Erosion and Welding Resistance in Ag-SnO₂ Contacts through WO₃ and Ag₂WO₄ Additives

To improve both welding and arc erosion resistance of AgSnO₂ contact material, the WO₃ and Ag₂WO₄ are designed as additives with consideration of the arc extinction ability of WO₃ and the expected improvement of interface between Ag and SnO₂ through Ag₂WO₄. The Ag-8 wt%SnO₂ contact materials without, and with WO₃ and Ag₂WO₄ additions are prepared, and the electrical contact tests are performed for 10 000 switching operations at 24 V/20 A. The microstructure, eroded morphology, arc characteristics, material transfer, and welding behavior are investigated, and the arc erosion mechanism is discussed as well. The results show that both WO₃ and Ag₂WO₄ have a good combination with Ag and SnO₂, and the melting and coating effects of Ag₂WO₄ happen during sintering owing to its low melting point. Compared with the material without addition, the mass loss rate decreases by over 50% with WO₃ addition, and it further decreases to near the zero with Ag₂WO₄ addition. Moreover, the WO₃ and Ag₂WO₄ additions also results in the decrease of welding force. The good performance can be attributed to the generated Ag₂WO₄, which is helpful for the dispersed distribution of SnO₂ at the eroded area.