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the development of high-tech industries stimulates the growth of requirements for the metal of welded structures and the complex of their basic and special properties. the use of pulsed electric currents, plasma currents, pulsed electromagnetic fields and their combined effects to improve the mechanical characteristics of metals and alloys is relevant in connection with the need in replacing traditional energy-intensive technologies for treatment of welded structures with more progressive ones. the use of a pulsed barrier discharge (pbD) in the metal treatment, which generates a low-temperature plasma on the surface of the treated metal is a new approach to optimizing mechanical properties of high-strength steels for welded structures, which is based on electrophysical processes. In the work, strengthening of 25khgnmt steel as a result of pbD action on its surface was investigated. The PBD treatment of steel took place in a discharge device at an increment rate of voltage ≈ 3•10 11 V/s. the effect of pbD treatment period on Vickers hardness value (HV) of test specimens was investigated. examinations of the structure of 25khgnmt steel were carried out by the method of transmission electron microscopy to reveal its changes as a result of pbD action. It was found that values of HV after pbD treatment increase from 420 to 505 kg/mm 2 , which is accompanied by a general increase in the dislocation density and dispersion of the microstructure, which can positively affect the mechanical characteristics of 25khgnmt steel for welded structures operating under dynamic loads.

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The present paper presents a study of the behaviour of Fe3Al intermetallic powders particles based on 86Fe-14Al, 86Fe-14(Fe5Mg), and 60.8Fe-39.2(Ti37.5Al) compositions obtained by mechanochemical synthesis at successive stages of the plasma spraying process: during transfer in the volume of the gas stream and deformation at the moment of impact on the substrate. The effect of the change in current on the size of powder particles during their transfer through the high-temperature stream and the degree of particle deformation upon impact with the substrate was determined. It was found that during transfer through the plasma jet, there was an increase in the average size of sputtering products by two–three times compared to the initial effects of mechanochemical synthesis due to the coagulation of some particles. In this case, an increase in current from 400 to 500 A led to a growth in average particle size by 14–47% due to the partial evaporation of fine particles with an increase in their heating degree. An increase in current also led to a 5–10% growth in particle deformation degree upon impact on the substrate due to the rising temperature and velocity of the plasma jet. Based on the research, the parameters of plasma spraying of mechanically synthesized Fe3Al intermetallic-based powders were determined, at which dense coatings with a thin-lamellar structure were formed.