Influence of electrical characteristics of the electric arc discharge device and temperature on the quality of the coating of contacts restored by the gas-plasma method

Abstract

The regularities of the influence of the electrical characteristics of the electric arc discharge device and the temperature during the gas-plasma process on the quality of the coating of the restored contacts of electromagnetic starters are revealed; the parameters of the quality of the coating on the electrical characteristics of the technological process of gas-plasma spraying are investigated. The regularities of creating high-quality coatings on contact parts with high characteristics have been established. In general, a significant number of factors directly or indirectly affect the process of coating formation during gas-plasma spraying and, ultimately, its quality. At the same time, it is important, on the one hand, to select indicators of the coating formation process, and on the other hand, to select the most significant and limiting factors from the total mass. All major factors can be divided into several main groups: - factors associated with the design of the spraying mechanism and various devices for spraying and the plasma torch (configuration and length of the channel, outlet diameter of the nozzle, location of the feed point and angle of entry into the plasma jet of powder, diameter of the powder supply channel; pressure and flow rate of cooling water; operating mode of the system gas cooling of the sprayed contact piece, etc.); - factors associated with the properties of the sprayed material (type of material - powder or wire; chemical composition, size and shape of wire or powder particles, physicochemical and thermophysical properties of the material, etc.); - factors related to the shape and size of the contact piece and the properties of the contact holder material (thickness, curvature of the sprayed surface, the presence of edges, grooves, etc.; chemical composition, mechanical and thermophysical properties of the base, etc.); - factors associated with the preliminary preparation of the contact holder surface for coating (surface roughness; preliminary heating of the base, etc.); - factors characterizing the operating mode of the spray device (current strength and voltage, type and consumption of plasma-forming and transporting gases; powder consumption or wire feed rate, etc.). By the way, this multifactorial nature of the process is further complicated by the possibility of various random perturbations, uncontrollable changes in individual factors, especially in conditions of manual gas-plasma spraying (for example, the spraying distance, the angle of inclination of the spray device to the sprayed surface; the nature and speed of the relative movement of the spray device and contact holder, the number of spray device passes, etc.). For example, erosion of the anode channel and cathode wear change the design characteristics of the burner, instability of the electrical parameters of the power source, and pulsation during powder supply affect the heating and particle motion conditions.