Preparation And Properties Of Ag/WC@SnO₂Electrical Contact Material

Ag/SnCO2contact material is widely accepted as the possible replacement of toxic Ag/CdO, and has been applied to low voltage apparatus. However, the current produced Ag/SnO2has a main problem that is the aggregation of SnO2reinforcement on the surface of contact after arcing, which will increase the contact resistance and over-temperature, lead to bad contact properties. The cause of the problem is the bad wettability between SnO2and Ag and the low density of SnO2. So, it is of great significance to research on the modification of SnO2reinforcement to promote the physical and contact properties of AgSnO2.In this paper, WC@SnO2composites were preparation by chemical deposition method and hydrothermal method. A new kind of Ag/WC@SnO2contact material was prepared by powder metallurgy method, and its properties was tested and discussed. The main work and results are as follows:(1) WC@SnO2powders were fabricated via wet chemical methods combined with surface modification method.1) Using PVA, CMC, SDBS, PVP as surface modifier, the dispersion stability of WC suspension was investigated.2) Using PVP as the surface modifier, SnCl4as raw material, we fabricated WC@SnO2composites by hydrothermal method, which WC core was covered with SnO2crysta1.3) Using PVP as the surface modifier, Na2SnO3as raw material, WC@SnO2composite were also fabricated by chemical deposition method, but the amount of SnO2is very small.(2) We prepared Ag/WC@SnO2contact material, with the as prepared WC@SnO2composite by powder metallurgy method.1) Compared with roller ball milling, the high energy ball milling could remarkably promote the distribution of SnO2in Ag matrix, and its physical properties.2) When the sinter temperature was varied from750℃to920℃, the density of Ag/WC@SnO2first decreased, then increased, and then decreased.3) A process of800MPa repress and600℃re-sintering could also promote the density, hardness and conductivity of the material.(3) Two pairs of contactors were made with Ag/WC@SnO2and Ag/SnO2material, and their dynamic contact properties were tested. The welding power of Ag/WC@SnO2contact is more stable, and the surface of the Ag/WC@SnO2contacts is more flat. The reason is that when the Ag evaporated and sputtered by arc, the content of W of the Ag/WC@SnO2risen, and then improve the anti-welding properties.