Using chromatography, the gas composition in a cold plasma jet, which is a flowing afterglow of a microwave glow discharge at atmospheric pressure, is analyzed. The plasma jet is formed by the interaction of the discharge plasma with atmospheric air behind the outlet of the 6-electrode plasma torch, electrical power to which is supplied from the waveguide microwave (2.45 GHz) plasmatron. An analysis of the gas samples of the jet shows that when plasma-forming argon flows through the microwave discharge, hydrogen and methane are formed behind the discharge region, and the concentration of carbon monoxide increases by 5–6 times. The reactive oxygen species in the cold plasma jet is studied using liquid chromatography of an aqueous solution of isopropyl alcohol after treatment with the plasma jet. It is found that because of plasma treatment, partial oxidation of isopropyl alcohol to acetone occurs. This makes it possible to consider acetone as an indicator of reactive oxygen species (hydroxyl radicals, atomic oxygen and ozone) in a cold plasma jet.

Method of electric arc synthesis of composite microparticles metal-semiconductor-dielectric based on titanium, titanium nitride and rutile with productivity up to 10 g/min is proposed. Using diffraction and microscopic methods, the morphology and structural-phase composition of the synthesized microparticles were studied. Using the example of methylene blue degradation, the photocatalytic activity of synthesized microparticles in the visible radiation range was demonstrated and its possible mechanism was proposed.

The influence of heat treatment, simulating thermal cycles and welding in the process of manufacturing joint fittings on microstructure, strengthening phase precipitation, and mechanical properties of base metal and near-weld zone of fittings, made of low-carbon copper-containing steel, is studied. Rolled product specimens are produced under laboratory and industrial conditions. Heat treatment regimes are developed, and mechanical properties of pipeline fittings of strength class K60 (X70) after normalizing with tempering and strength class K65 (X80) after additional quenching before tempering combined with satisfactory impact strength and weldability are provided.

The effect of copper content in the range of 0.8–1.4% on mechanical properties and cold resistance of low-alloy precipitation-hardening steel for fittings after heat treatment is investigated. It is established that steel containing 1.4% copper provides the maximum level of strength properties after normalizing and tempering and in this case the steel has an acceptable level of impact strength and cold resistance. The microstructure of steel with 1.4% Cu is investigated by scanning and transmission electron microscopy after tempering at different temperatures. Structure formation in steel with a high copper content during heat treatment by regimes simulating fitting preparation by hot stamping with subsequent tempering, including changes occurring with a secondary structural component, carbonitride particles, and copper particle strengthening precipitates, is studied in detail.

Technologies for plasma heating of steel in a continuous caster tundish, plasma-arc remelting nitriding, and metal surface modification are developed using an efficient dc low-temperature plasma generator with a self-adjusting arc length, vortex stabilization, and an expanding gas-discharge channel. The temperature stabilization of the cast steel increases the fracture toughness and the critical crack opening in the deformed steel in both the transverse and longitudinal rolling directions. Remelting of steel in nitrogen plasma refines grains; increases the strength, ductility, total fracture work, and wear resistance under dry friction conditions; and decreases the corrosion rate. Plasma treatment saturates the metal surface with nitrogen and forms a wide range of structures with a deep and gradual transition zone, which ensures strong adhesion of the hardened layer to the base metal.

An experimental unit is described for effective alloying of steel with nitrogen by plasma arc remelting. Production regimes are developed for unit operation making it possible to obtain a super-equilibrium content of nitrogen (up to 0.22%) in remelted metal with action of a plasma flow at a temperature of ≈ 7000 K in molten metal with the metal temperature in the arc-binding zone of up to ≈ 2700 K. The technology of remelting of 55Kh20G9N4 steel facilitates grain refinement, an increase in strength properties, ductility, and overall energy for failure, wear resistance under dry friction conditions and a reduction in the corrosion rate.

The influence of sheet microstructure formed by various thermomechanical processing schedules on sulfide stress cracking ( SSC ) resistance under uniaxial tension for low-alloy pipe steels grades X42–X65 is studied. A favorable role is established for substitution of a ferritic-pearlitic by a ferritic-bainitic microstructure and improvement of structural component dispersion is established. The favorable effect is facilitated by using high intensity post-deformation cooling from the austenite region. It is shown that segregation bands and non-metallic inclusions in a sheet axial zone do not affect the duration of specimens withstanding SSC, but they can lead to formation of hydrogen cracks ( HIC ) on a specimen surface that is a defective feature. In order to prevent crack formation in a specimen surface and premature failure it is necessary to lay down high specifications for specimen gauge length and fillet surface quality.

Results are given for a study of the corrosion resistance of a number of protective coatings for offshore structures and shelf zone constructions operating under conditions of total and periodic immersion in sea water.

The problem of crack strength and wear resistance of metal products increase becomes particular significance in relation to continuously increasing requirement to their reliability and long service time. Traditional methods of volume strengthening of structure elements mainly exhausted their capacity. At the same time their resource, for example, under high wear conditions, is determined mainly by the structure and working surface properties and can be increased by application of plasma surface strengthening of metal products. Plasma surface strengthening of metal products is a typical of a technology covering spheres of plasma physics, hydrodynamics, theory of heat exchange, metal science. Complication of its mathematical simulation and digital calculation is stipulated by extensiveness of processes taking place: from crystal lattice scale till plasma treatment facility scale. By this reason experimental approach to solving a series of particular problems, enabling for optimizing plasma treatment facilities and technological process in the whole is important and actual. Results of influence study of outlet channel configuration of plasma treatment facility and treatment regimes on the structure and properties of metal surface after plasma thermal treatment presented. Forms of flow transformer outlet channel of plasmatron determined, providing the samples obtained demonstrated the highest level of surface hardness and wear resistance, during dry friction tests and wear test by semi-fixed abrasive material. It was shown, that change of the plasma treatment facility outlet channel configuration enables to effectively control the technological parameters (plasmatron travelling speed, plasmatron power and plasma-forming gas consumption), as well as the thermal cycle, which provides forming of required surface properties of treated detail. A basis of the results obtained based on the analysis of strengthened layer metal structure presented. Abrasion tests by a semi-fixed abrasive material showed, that surface plasma treatment gives a considerable wear resistance growth – up to 3 times comparing with a non-strengthened metal.

The review of the methods of controlling the steel temperature in the tundish of the billet continuous caster has been presented including their advantages and disadvantages. The advisability of selecting one of the methods of heating, the plasma method has been grounded. The international experience in operating the plants for the steel plasma heating in the tundish has been described. The values of the main technological parameters of the heating process have been presented. And the recommendations for utilizing the technology depending on the parameters of casting have been given.

The influence of the electric field on a single air bubble in transformer oil has been studied. It has been shown that, depending on its size, the bubble may initiate breakdown. The sizes of air and sulfur hexafluoride bubbles at which breakdown will not be observed have been estimated based on the condition for the avalanche-to-streamer transition.

Low-temperature plasma is used in the plasma-arc remelting of 55Kh20G9N4 steel. The plasmaforming gases employed are nitrogen and argon. The influence of the remelting parameters on the structure, the mechanical properties, the flexural strength, and the corrosion and wear resistance of the stainless steel is studied. When using nitrogen to form the plasma, its content in the steel increases. That increases the strength, crack resistance, and corrosion and wear resistance of the steel.

Одиночный пузырек электроотрицательного газа в трансформаторном масле под действием электрического поля

A technique of determination of the thermal conductivity of structural materials in a wide range of temperatures has been developed and verified. A three-dimensional simulation of the process of heat propagation into the body from the surface heated by a nonstationary source of heat has been performed based on the data obtained on thermal conductivity. A satisfactory coincidence between the computational and the experimental results of temperature measurements at different depths from the heated surface has been obtained.

Разработана и верифицирована методика определения теплопроводности конструкционных материалов в широком диапазоне температур. На основе полученных данных по теплопроводности выполнено трехмерное моделирование распространения тепла в глубь тела от прогреваемой нестационарным источником тепла поверхности. Получено удовлетворительное совпадение между расчетами и экспериментом по измерению температуры на разной глубине от прогреваемой поверхности.

The combination of forging with plasma-powder hardfacing is a further development of the method applied in the reconditioning of railway junctions. The process, equipment and the effect of impact energy on the properties of layers are investigated. The technology is promising for the hardening (reconditioning) of long components and eliminates the need for preliminary bending and subsequent heat treatment.

Successful use of plasma hardening technology requires a search for optimum plasma treatment methods, especially when there is a change in the chemical composition of the metal in the products. In order to study the impact of the chemical composition of steel on the structure and properties after plasma hardening, various steel alloying options were selected with respect to concentration of major elements affecting phase transitions upon cooling. In wheel steel, these elements are carbon, manganese, chromium, and others. This paper describes the results of metallographic studies and mechanical tests.