Fabrication and characterization of Ag-4wt.%TiB2-4wt.%Ni contact materials utilizing coarse and ultrafine Ag powders

To clarify the effect of Ag particle size on the microstructure, properties and arc-erosion characteristics, Ag-4wt. %TiB2-4wt.%Ni materials were fabricated using 72 mu m and 0.4 mu m Ag powders. The sintered materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The degradation behavior under the action of electric arc was studied by different electrical contact operations. The results show that the sintered material prepared by 0.4 mu m Ag powder presents a good dispersion of strengthening particles, while the strengthening phases aggregate at the Ag particle boundaries for the sintered material prepared by 72 mu m Ag. Furthermore, it is found that Ni3B and Ni3Ti form owing to the reaction of TiB2 with Ni during sintering. Besides, ultrafine Ag powder not only increases the hardness (increased by 85.41%) and electrical conductivity (increased by 22.44%), but also improves the compression strength. Additionally, ultrafine Ag powder increases the make-arc-energy, but decreases the break-arc-energy. The difference of make-arc-energy and break-arc-energy can be attributed to the morphological change and the arc dispersion effect derived from the distribution of strengthening phase. Furthermore, the aggregation of strengthening phase causes the formation of Ag-rich phase and the locally aggravated splash.