Investigation of the composition of Ag, Ni and Ag-Ni pseudo-alloy coatings applied by electrospark alloying on a Cu substrate

The electrospark alloying (ESA) coating process is a promising technique for the creation of bimetallic electric contacts. It is known that, owing to alloying of the electrode and substrate materials during the ESA process, coating and electrode compositions do not remain constant. It is necessary to have information about the coating compositions to predict in some way the properties of the electric contacts to be designed. The quantitative composition of ESA Ag, Ni and Ag-Ni pseudo-alloy coatings on a Cu substrate was investigated in this using scanning electron microscopy and electron microprobe analysis. It was found that the Ag concentration on the surface of the Ag-Ni pseudo-alloy coating is 1%-5% above the Ag concentration in the nominal pseudo-alloy composition. The Cu distribution along the Ag coating cross-section is examined and it is shown that the intermediate ESA Ni layer applied between the Ag coating and the Cu substrate completely expels the Cu penetration into the Ag. It is also stated that the transition zone depth, which is supposed to correspond to the cathode liquid bath depth, is not more than 3 μm in the pulse energy range 0.04-0.155 J. (orig.)