Structure and properties of the electromagnetic starter’s contacts with the electro-explosive CuO-Ag coating

Abstract

Abstract Phases and elemental composition of CJ20 electromagnetic starter’s contacts subjected to electro-explosive spraying of the CuO-Ag coating were studied by using transmission and scanning electron microscopy methods. Electro-explosive spraying CuO-Ag coating were carried out in mode providing contact’s premelting condition. Such mode managed to minimize energy cost. Produced coating has a homogeneous structure containing silver matrix and CuO inclusions located in the matrix. After electro-explosive spraying the structure of coating elements’ surface and their scale vary in a very wide range from thousands µm to tens of hundreds µm. The high-speed cellular crystallization’s structure is formed in the electro-explosive CuO-Ag coating regardless of distance to modifying surface. The cell’s size is ranged from 150 nm to 300 nm. The cells are separated by the second phase’s layers which thickness varies from 10 nm to 70 nm. The cell is volume formed by copper atoms; silver atoms are located in interlayers along the cell boundaries. Sprayed coatings were tested for wear resistance, friction coefficient, nanohardness and Young’s modulus. The formed coating shows an increase in 2.0 times nanohardness, in 3.3 times wear-resistance and in 1.4 times friction coefficient and decrease to 5.3 times Young’s modulus in comparison with the original copper electrical contact.