Structure and properties of composite coatings of the SnO2–In2O3–Ag–N system intended for strengthening the copper contacts of powerful electric network switches

Abstract

The goal of the research is to analyze the structure and properties of the coating SnO2–In2O2–Ag–N formed on copper by a complex method. The method of coating formation combined the electroerosion spraying, irradiation by pulsed electron beam and subsequent nitriding in plasma of a gas discharge of a low pressure. It is shown that the thickness of the coating amounts to ≈100 μm. The wear resistance of a copper sample with the deposited coating is ≈ 2.8 times higher than that of copper without the coating. The friction coefficient of samples with the coating (μ = 0.479) is ≈ 1.4 times less than that of copper without the coating (μ = 0.679). It is established that the coating hardness increases as the substrate is approached and reaches its maximum value of ≈1400 MPa (substrate hardness is 1270 MPa). By means of micro-X-ray- spectral analysis it is detected that the main chemical element of the coating is silver, with copper, tin, indium, oxygen and nitrogen being present in a much smaller quantity. By the methods of X-ray phase analysis it is revealed that the main phases of the coating are copper-and silver base solid solutions. Tests for the electroerosion resistance showed that the coatings meet the requirements of standards for electromagnet starters with the category of application AC-3 of direct action.