Increase in properties of copper electrical contacts in formation of composite coatings based on Ni–C–Ag–N system

Abstract

The article is concerned with analyzing the structure and properties of the Ni–C–Ag–N coating formed on copper by the complex method combining the electroexplosive spraying of coating, its irradiation by a pulsed electron beam and a subsequent nitriding in plasma of a gas discharge of low pressure. The structural constituents of coating's surface after the electroexplosive spraying as well as after the electron-beam processing and nitriding are studied. It is shown that a coating's thickness amounts to ≈90 μm. The wear resistance of a copper sample with the deposited coating exceeds that of the copper without the coating by ≈ 1.6 times. The friction coefficient of samples with the coating (μ = 0.5) is less than that of the copper without the coating (μ = 0.679) by ≈ 1.35 times. It is established that the hardness of the coating increases as the substrate is approached and reaches the maximum value of ≈1780 MPa (the hardness of substrate is 1300 MPa). By means of micro-X-ray-spectral analysis it is detected that the main chemical element of the coating is silver, but copper, nickel, carbon and nitrogen are present in a considerably smaller quantity. It is established by the methods of diffraction electron microscopy that the main phases of the coating are solid solutions.