ELECTROCATALYTIC COBALT-VANADIUM COATINGS FOR THE HYDROGEN EVOLUTION REACTION

The study of existing energy-saving materials and obtaining the new ones for reducing the cost of the hydrogen production, is relevant for modern hydrogen energy industry. Such properties can be predicted for materials containing vanadium, molybdenum, tungsten and exhibiting catalytic activity for the hydrogen evolution reaction Aforementioned metals can be co-deposited from aqueous solutions with iron subgroup metal-catalysts through the formation of cluster intermetallic compounds with Me-V bond adsorbed on the cathode surface. The induced co-deposition of cobalt with vanadium from the complex citrate electrolyte was investigated in the current work. As a result of the research, it was found that the uniform microcrystalline light-gray high-quality cobalt-vanadium alloy coating is possible to precipitate from a citrate electrolyte with content of 20 g/dm3 vanadium (in terms of metal) as a citrate complex The process was carried out at a current density of 5–10 A/dm2, at a temperature of 30–40°С, pH = 2,8–3,2. The content of vanadium in the coating is 0,37–0,53 % by weight. The maximum vanadium content in the coating is observed at current densities 8–9 А/dm2. The catalytic activity study of the coating that was obtained using cobalt-vanadium alloy in the reaction of hydrogen reduction at the cathode was performed in solution of 2,5М NaOH + 0,02 M NaCl. By increasing the vanadium content in the coating from 0,37 to 0,53% the hydrogen evolution overvoltage is reduced by 0,5 V. It was found that the overvoltage of the hydrogen ion evolution reaction on cathodes from steel 20 with cobalt-vanadium coating is 0.08–0,1 V lower, and the exchange current is higher than on electrodes made of steel 20, which are used in industrial water-alkali electrolysis. This indicates the electrocatalytic activity of the investigated materials for the hydrogen evolution reaction. Electrodes with coating, obtained by cobalt-vanadium alloy can be recommended as a cathode material for the hydrogen electrochemical production. Hydrogen evolution overvoltage reduction also decrease the energy consumption for this process by 15–20 %.

Виготовлення авіаційних деталей з жароміцних нікелевих сплавів методом адитивного плазмового наплавлення

The aviation part of the ring-type was made of heat-resistant structural alloy EI 868 (HN60VT) by the method of additive multilayer plasma surfacing with wire. The traditional technology for obtaining this type of ring blank is the stamping of rods, which are then brought to the final shape of the part by further machining. The disadvantage of traditional technology is the significant cost of metal, which in the process of machining the pressed rod, is converted into chips and not reused, which increases the cost of the finished product. The use of additive technologies will significantly reduce the cost of material in obtaining annular workpieces by manufacturing a workpiece with a configuration as close as possible to the geometry of the part. Additive surfacing was performed on a robotic complex consisting of a plasma power supply SBI PMI-350 AC/DC TL and work FANUC M-710iC on a rigidly fixed substrate of steel 20. To determine the possibility of obtaining aviation parts using the method of layer-by-layer plasma surfacing, a study of the deposited material was conducted The structure of the grown part was studied, it was found that the microstructure corresponds to the normal state of the alloy EI868 (HN60W) in the microstructure of the fusion line is not visible, the structure is homogeneous with the mutual germination of grains between layers. Alloy parts obtained using the method of additive cultivation are at the level of cast blanks and forgings and at T = 900oC are: sв =35±5 кгс/мм2,s0,2 =49±5 кгс/мм2, y = 62±5 %. After machining the grown workpiece, a capillary method of control and radiation control of the grown part - cracks and other types of critical metallurgical defects was not detected. The practical significance of the introduction of this method is a significant reduction in material costs in obtaining parts and ensuring economic efficiency, which is about 159 thousand hryvnias.

Deformation of a pipeline element under cyclic loading by internal pressure

An experimental study of the strain of a rectilinear segment of a pipeline Du 200 made of steel 20 under cyclic loading by internal pressure was carry out. The tests were performed on a pneumohydraulic stand under conditions of flat stress, normal temperatures, and load cycle asymmetry with registration of circular and axial elastic-plastic strain. The aim of the work was to test an experimental technique for studying the effect of ratcheting (unilateral accumulation of plastic deformations) on real structural elements when changing the modes of cyclic loading. According to the results of the study, curves of cyclic deformation (ratcheting) of the pipe in the circular and axial direction on the basis 100 cycles were obtained.

Structures based on elliptical arcs in the problems of designing trajectories and creating mechanical systems

An experimental study of the strain of a rectilinear segment of a pipeline Du 200 made of steel 20 under cyclic loading by internal pressure was carry out. The tests were performed on a pneumohydraulic stand under conditions of flat stress, normal temperatures, and load cycle asymmetry with registration of circular and axial elastic-plastic strain. The aim of the work was to test an experimental technique for studying the effect of ratcheting (unilateral accumulation of plastic deformations) on real structural elements when changing the modes of cyclic loading. According to the results of the study, curves of cyclic deformation (ratcheting) of the pipe in the circular and axial direction on the basis 100 cycles were obtained.

Thermal diffusion chromium plating of structural carbon steel 20 by high frequency currents

To increase the service life of the gear teeth made of steel 20, operating under high shock loads, their main surfaces were subjected to high-temperature diffusion metallization, namely, chromium plating with high-frequency currents. As a result of diffusion metallization, the surface hardness increased 5.1–5.4 times – from 156–159 HV to 800–866 HV, and the strength level 3.3 times – from 250 to 820 mAh. Optimal parameters for the diffusion metallization: current I = 0.25–0.3 kA, power Pe = 8–10 kW, hardening τ = 8–10 min. By the method of scanning electron microscopy, it was found that after diffusion saturation of the surface of the gear teeth with chromium, the steel has a homogeneous structure with clearly pronounced transition layers, the average thickness of the diffusion layer was 0.06 mm. Energy dispersive analysis showed that after diffusion metallization with chromium powder, the basic composition of the steel remained constant, only the qualitative ratio of the components changed. X-ray phase analysis revealed the presence of an αFe-phase with the incorporation of Cr on the surface of the sample.

Study on efficiency of corrosion inhibitors based on derivatives of isothiuronic salts

Metals play a pivotal role in industry; their use constantly grows. It is virtually impossible to find an industrial field without the use of metals and their alloys. However, owing to the quality degradation of metal during the operational process, corrosion appears not only on its surface but also under a coating, which leads to its destruction. To avoid this, corrosion inhibitors are necessary. Organic compounds have been widely used as corrosion inhibitors. Many organic corrosion inhibitors have been developed nowadays. In the literature, organic compounds comprising N, O, S and P heteroatoms are described, which reduce corrosion rate. The organic compounds are adsorbed on the metal surface, forming a thin layer. Adsorption occurs either through electrostatic interaction or, in some cases, the formation of covalent bonds. The work aimed to study isothiuronic salts as corrosion inhibitors to evaluate their protective properties using the polarisation curves method. Objects of research were isothiuronic compounds containing two active centres separated by saturated and unsaturated carbon bonds (structures 1-3). In structures 4-7, one isothiuronic fragment has different propylene substituting groups. It has been previously shown that these compounds can act as effective brightening agents when applying nickel coatings. A model solution with a density of 1.12 g/cm3 was prepared to study the corrosion inhibitors. The corrosion inhibitor concentration was 400 mg/L. Studies have shown that the compounds with two isothiuronic moieties do not always exhibit improved properties for inhibiting metal degradation in a corrosive environment. In particular, they showed worsening of the inhibiting properties for samples made of steel 20 and identical properties for that made of steel 3.

DETERMINATION OF THE COMPRESSIVE STRESS OF A RAIL USING THE EFFECT OF ACOUSTOELASTICITY AND STRAIN GAUGE

A method for monitoring the compression stress in a rail and a sample made of steel 20 using the effect of acoustoelasticity and strain gauge has been developed. Wire load cells were pasted to the opposite sides of the rail and the sample. Measurements, recording and processing of strain gauge information was carried out by a certified microprocessor strain gauge system MMTS-64.01 with accuracy class 0.2. To control the compression stress, the developed microprocessor-based ultrasonic system “Akusto-1” was used, which operates on the basis of the acoustoelasticity effect. The angle of input of ultrasonic vibrations, equal to 18°. This allowed to excite longitudinal, transverse and transformed waves in the object. Compressive stresses in the rail and steel sample were carried out by 250-ton loading machine “PSY-250”. Longitudinal and transformed ultrasonic waves were used to control compressive stresses. A comparative analysis of the experimental and calculated dependences of compressive stresses on the load obtained by acoustic, tensometric and computational methods is performed. The reliability of the experimental and calculated results was controlled by a certified microprocessor strain gauge system MMTS-64.01.

Estimation of corrosion aggression of aquatic media and corrosion resistance of steels of equipment of oil and gas condensate deposits

Corrosion destruction of the metal of the field equipment and gas pipelines of the oil and gas condensate field (OGCF) was revealed, the cause of which is carbon dioxide corrosion. In order to determine the corrosiveness of the OGCF equipment media, laboratory tests were carried out with periodic moisture condensation in an atmosphere of carbon dioxide, autoclave tests in the liquid phase at elevated temperatures and partial pressure of CO2, and laboratory tests in the gas-vapor phase in the presence of CO2. Tests were carried out on steel 20, the selected solutions were tested on pipe segments of 09G2S steels (well connections and loops) and J55LT (tubing) of 2 types (old, after operation in a well, and new, not operated). Studies have shown that steels used at OGCF (steel 20, J55LT and 09G2S) are not resistant to carbon dioxide corrosion. All items of equipment made of these steels will be potentially weakly resistant to corrosion in the oil and gas condensate field. It is proposed to conduct tests of corrosion inhibitors from various manufacturers in laboratory and field conditions. Recommendations are given for the corrosion inhibitor selected according to the test results. Keywords: local corrosion; aggressiveness of the environment; metal resistance; well piping; plume; tubing; laboratory tests; autoclave tests.

X-RAY STUDIES OF COMPOSITE MATERIAL STEEL 20 - STAINLESS STEEL 50CR15MO2V AFTER EXPLOSION WELDING AND NORMALIZATION

The results of studies of the characteristics of the fine structure of a bimetal made of stainless steel 50Kh15M2F and carbon steel 20 after explosion welding and subsequent heat treatment in the joint zone are presented. It was found that normalization at temperatures above 900 ° C leads to a martensitic transformation in steel 50Cr15Мo2V, which is accompanied by an increase in hardness and the development of a fine structure: an increase in the level of elastic deformation of the crystal lattice and fragmentation of coherent scattering regions.

Computational and experimental determination of the parameters of the Cowper — Symonds hardening materials model for metal beams

The study introduces a method for the computational and experimental determination of the parameters of the Cowper — Symonds material model for steel beam structures under shock loads, the method being based on the finite element method. A full-scale experiment was carried out on a developed and manufactured installation that implements dynamic shock loading of metal beams according to the three-point bending scheme. The results of the practical approbation of the proposed method are presented on the example of determining the parameters of the Cowper — Symonds model for beams of steel 20. The difference between the calculated and experimental values of the residual deflection of the beam did not exceed 5%. Computer simulation of the experiment was carried out in the ANSYS LS-DYNA software package. The above methodological approaches are proposed to be used in the calculated assessment of the strength of the power structure of passenger vehicles for compliance with the requirements of UN Regulation No. 66.