One of the most promising applications of FeNiCoCrMoAl-based high-entropy alloy is the fabrication of protective coatings. In this work, gas-atomized powder of FeNiCoCrMo_0.5Al_1.3 composition was deposited via high-velocity oxygen fuel spraying. It was shown that in-flight oxidation of the powder influences the coating’s phase composition and properties. Powder oxidation and phase transformations were studied under HVOF deposition, and during continuous heating and prolonged isothermal annealing at 800 °C. Optical and scanning electron microscopy observation, energy dispersive X-ray analysis, X-ray diffraction analysis, thermogravimetric analysis, differential thermal analysis, and microhardness tests were used for study. In a gas-atomized state, the powder consisted of BCC supersaturated solid solution. The high rate of heating and cooling and high oxygen concentration during spraying led to oxidation development prior to decomposition of the supersaturated solid solution. Depleted Al layers of BCC transferred to the FCC phase. An increase in the spraying distance resulted in an increase in α-Al₂O₃ content; however, higher oxide content does not result in a higher microhardness. In contrast, under annealing, the supersaturated BCC solid solution decomposition occurs earlier than pronounced oxidation, which leads to considerable strengthening to 910 HV.

The paper presents the results of plasma torch development and gas fluxes using possibility in plasma welding process. As part of the work, existing plasma torches were analyzed in order to identify opportunities for their modernization. The literature data was analyzed for identifying the optimal design of the plasma torch. During the study of literature data, it was found that the diameter of the nozzle tip has a great influence on the plasma welding process. Therefore, it was decided to model the processes occurring in the plasma torch using tips with different diameter sizes. Parameters that effects on the stability of plasma welding process were presented. Possible and potential effective plasma torch tip designs were proposed. The model of the behavior of argon in a plasma torch was constructed, which made it possible to draw conclusions about the optimum diameter of the plasma torch tip. Also, was shown the effect of the diameter of the plasma torch on the behavior of plasma gas.

The present work considers the results on synthesis of composite clad powder systems with the “core-shell” type of structure for spraying wear-resistant metal-ceramic coatings. Powders of highly hard TiB₂ and HfB₂ borides were used as a core for the synthesis of a composite powder, and titanium was used to create coating on their surface. The cladding layer is synthesized by the iodine transport method. Powder cladding uses the method of detecting one component on another gas transport path, the agent of which is contact iodine. The deposition of composite clad powders of the TiB₂/Ti and HfB₂/Ti systems is implemented by the microplasma method, which, in contrast to the classical plasma deposition, makes it possible to dissolve transformations in composite powders due to thermal action. In the study of transverse microsections of sprayed coatings, it was found that during microplasma spraying, titanium is saturated with oxygen, forming a titanium dioxide phase, as a result of which the clad composite powder of systems TiB₂/Ti and HfB₂/Ti are converted into coatings from systems TiB₂(TiB)/Ti(TiO₂) and HfB₂/Ti(TiO₂). Features of the composition in terms of coating thickness were revealed. The study of hardness shows that the integral value of microhardness for a coating based on titanium diboride is 1300 HV. Coating based on hafnium diboride has integral microhardness of about 1600 HV. When checking the wear resistance, pairs with TiB₂(TiB)/Ti(TiO₂) and HfB₂/Ti(TiO₂) coatings were mated with a counterbody from the 45Kh sample without coatings and together with each other. Despite the lower microhardness, the most wear-resistant is coating of TiB₂(TiB)/Ti(TiO₂) system.