MICROSTRUCTURE AND ELECTRICAL PROPERTIES

As a pollution-free contact material, Ag/SnO2 has shown a promising prospect to replace noxious Ag/CdO because of its remarkable resistance to arc-erosion and welding. Especially La-doped Ag/SnO2 contact alloy shows excellent electrical properties during arcing test. In this paper, Ag/(Sn0.8La0.2)O2 coating on the Cu substrate was prepared by atmospheric plasma spraying. The phase structure and microstructure of Ag/(Sn0.8La0.2)O2 coating were characterized using XRD and SEM, respectively. The tests of tensile and arc erosion were employed to evaluate bonding strength and electrical properties of coating. The results show that the prepared coating has the uniform dense microstructure. The nanosized (Sn0.8La0.2)O2 particles are uniformly dispersed within the Ag matrix of coating. The bonding strength is 18.8 MPa. The breakdown strength and arc erosion rate of coating are 3.76×10 7 V/m and 37.7 μg/C, and the value are close to the bulk material. After arcing test, the surface of coating presents the dispersion of cathode spots and a little erosion, and the arc erosion mechanism of Ag/(Sn0.8La0.2)O2 coating has a change tendency from liquid splash to evaporation erosion.