Material transfer behavior of AgTiB2 and AgSnO2 electrical contact materials under different currents

To clarify the effect of the characteristics of strengthening phase on the material transfer behavior of silver base contact materials, the good electrical and thermal-conductive TiB2 ceramic and insulating and poor thermal-conductive SnO2 ceramic were selected as the strengthening phases, and the Ag-4wt.% TiB2 and Ag-4wt.% SnO2 contact materials were prepared with different sized TiB2 and SnO2 powders by powder metallurgy. The electrical contact tests were performed on an electrical contact material testing system at a voltage of 12 V DC and a current ranging from 5 A to 24 A. The results show that the material transfer mode is from cathode to anode at small currents for the Ag-4wt.% TiB2 contact material. However, it changes reversely at large currents. For the Ag-4wt.% TiB2 contact materials prepared with 500 nm and 60 nm TiB2 powders, the critical current at which the material transfer mode changes are 16 A and 24 A, respectively. Nevertheless, the material transfer mode for the Ag-4wt.% SnO2 contact material is always from cathode to anode at 5-24 A. Furthermore, fine strengthening particles are beneficial for less mass loss and relative transfer mass for both Ag base contact materials. The Ag-4wt.% TiB2 contact material presents a lower relative transfer mass than Ag-4wt.% SnO2 contact material. (C) 2016 Elsevier Ltd. All rights reserved.