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composition and flow rate of plasma-forming gas, spraying distance). As a rule, its value is in the range of 4-8 mm. The coating over a given area occurred due to the linear movement of the plasma torch in combination with either the transverse displacement of the plasma torch or the contact part. The specific mechanism of the formation of coatings from sprayed materials and the difficulty of manufacturing experimental samples determined the need for special studies of the properties of sprayed coatings: tensile and compressive strength, elastic characteristics of the stress state, thermal expansion and thermal conductivity, and switching wear resistance of restored contacts.

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.

The questions of influence of contact material, switching modes and environment with various impurity on electroerosion resistance of contact details of switching devices are considered. Substantiated possibilities and measures to increase the reliability and efficiency of relays in electrical installations through agriculture through the use of erosion-resistant contact materials based on the study of physical and mechanical properties of the components of the composite contact material in switching current; substantiated composition of ingredients in the new composite material for contact parts of switching devices. The results of researches of electro erosive stability of composite material depending on structure of ingredients and their physical and mechanical properties are resulted. It has been experimentally established and theoretically confirmed that electric erosion is mainly determined by the microstructure of the material and the change in the physical and mechanical properties of the ingredients on the working surface of the contact parts during current switching. Factors providing increased arc resistance due to thermoemission properties of contact compositions that control the processes of diffusion, migration and phase transformations in chemical reactions are obtained, and the theory of the mechanism of arc reference points movement on the working surface of electrical contacts is substantiated.