ВЛИЯНИЕ ТЕРМОДИНАМИЧЕСКИХ ПАРАМЕТРОВ ПЛАЗМЕННОЙ СТРУИ НА АДГЕЗИОННУЮ ПРОЧНОСТЬ ГАЗОТЕРМИЧЕСКИХ ПОКРЫТИЙ

Abstract

Gas-thermal spraying of metals and alloys makes it possible to obtain coatings with high performance properties on the surfaces of parts. These coating methods can be effectively used in the restoration of worn-out parts of machines and equipment of various types, which, in the face of large-scale sanctions, is one of the most important tasks of technological independence of Russian industries. (Research purpose) The research purpose is searching for the regularities of the influence of the main thermodynamic parameters of the plasma jet on the adhesive strength of the formed coatings. (Materials and methods) The deposition of refractory metals and alloys on a graphite substrate was carried out using the UPU-3 plasma installation. The temperature and velocity of the particles during plasma spraying of the wire were determined according to the generally accepted method. The average mass temperature of the particles in the considered section of the plasma jet was estimated by the increment of the enthalpy of the particles of the deposited metal. When calculating the heating temperature of the particles of the sprayed powder material, it was assumed that the temperature field of the gas stream beyond the nozzle section is determined by the thermophysical properties of plasma-forming gases and the conditions of heat exchange of the jet with the environment. The adhesive strength of the coatings was measured by the shear method. To estimate the values of residual stresses, temperature fields in the deposited layer and substrate were studied. (Results and discussion) The existing theoretical ideas about the physical processes in the formation of gas-thermal coatings were analyzed. The main thermophysical characteristics of the plasma jet affecting the sputtering of various powder and wire materials were considered. The factors ensuring the maximum adhesion strength of gas-thermal coatings to the surface of the composite material were determined. (Conclusions) It has been proved that the temperature of the particles of the sprayed material determines the adhesion strength of the coatings. The magnitude of thermal stresses occurring in coatings depends on the ratio of the thermophysical constants of the coating material and the substrate. To obtain coatings with maximum adhesive strength during high-temperature spraying of the material, it is necessary to additionally take into account the conditions determined by the forces of mechanical engagement of deforming particles.