Surface Engineering and Applied Electrochemistry最新文献

Using the methods of mathematical planning of the experiment, the optimization of the process of applying coatings based on aluminum alloys by the centrifugal induction method was performed, which made it possible to develop a mathematical model and determine the range of values of technological modes and to establish the dependences of the minimum coefficient of friction of the coating material on the parameters of centrifugal induction surfacing aluminum alloy coatings. As the main factors influencing the value of the coefficient of friction of the coating material, the rotational speed of the part, part temperature during isothermal holding, and the time of isothermal holding were considered. Based on the results of computational and experimental modeling, it is shown that, in order to obtain the optimal coefficient of friction of the coating material based on an aluminum alloy, the parameters of the process of centrifugal induction surfacing should be as follows: part rotation frequency n = 1700–1800 rpm, part temperature during isothermal holding T = 760–780°C, and isothermal holding time t = 300–360 s.

The main and leading factor in the world economy is the use of innovation. The development of new and highly intelligent technologies makes it possible to ensure high rates of economic development. In addition, the development of high-level technologies makes it possible to preserve the ecosystem and reduce the number of harmful industries. The article discusses the problems of the development of laser technologies for solving the problems of the leather industry of the Republic of Belarus and the Republic of Uzbekistan according to the research conducted by the authors. The morphology of the surface of the sample was investigated by the methods of optical and scanning electron microscopy, and the elemental analysis of natural leather under the action of laser radiation was carried out. Laser processing was carried out on the Flexsi 600 industrial complex (based on a CO₂ laser source Rofin Synar (Germany), which is designed for high-speed cutting, marking, and engraving of various materials, power P = 135 W, scanning speed V = 600 mm/s, frequencies ν = 5.0; 3.5; 2.5; 1.5; 1 kHz). Laser processing was carried out from the front surface of the shoe blank. The process of leather perforation was investigated. It is shown that, after perforation with a frequency of 5 kHz, the laser impact zone is approximately 330 μm along the entire perimeter of the hole. With a decrease in the frequency of laser action, a continuous combustion zone is not formed and the size of the zone of influence narrows. From the analysis of the results, it follows that the most favorable perforation modes are in the region of 2.5–3 kHz. At an exposure frequency of 1–1.5 kHz, leather perforation does not occur. The scanning electron microscopy method was used to study the surface morphology of a natural leather sample exposed to laser radiation from the front and back sides. It was found that the effect of laser polishing of leather is achieved in the range of input energies of 30–240 J and exposure durations of 30–240 s. The treatment was performed using a LS-2134D yttrium aluminum garnet laser (LOTIS, Belarus) with a wavelength of 1064 nm, generating in a two-pulse mode (pulses are separated by a time interval of 3 μs, pulse duration is 10 ns..

The effect of magnetic-pulse treatment on changes in the properties of steel grades 40Kh13, R6M5, and 40KhMFA depending on the pulse duration, frequency and energy characteristics of the treatment is studied theoretically and experimentally. An experimental MIU 20-21 magnetic-pulse unit capable of increasing pulse duration and changing the strength of the magnetic field is developed. Dependencies of variation in microhardness and in the surface roughness parameter Ra of the studied samples are obtained on different magnetic-pulse units with different technical characteristics and under different modes of exposure. The treatment has made it possible to reduce the surface roughness values from 5 to 26%, to diminish the spread in values of surface microhardness and to increase it up to 20%. The research into the pulsed magnetic field effect on residual stresses in samples indicates the possibility of changing them stably and repeatedly. Stresses have been completely regulated in several samples using this method of magnetic-pulse treatment.

A comparison is made of the characteristics studied in recent years in the CIS and other countries and relevant for the industry processes of forming wear-resistant coatings from self-fluxing alloys on metal products using a combination of gas-thermal (plasma, flame) spraying and high-frequency induction (HF) melting. A preliminary analysis of the parameters of this type of process is performed using various types of melting of coatings containing (after spraying) the strengthening ceramic (carbide, boride , oxide) or other phases that have been experimentally tested at the present stage. The prospects for using devices for melting that provide increased energy efficiency during HF treatment are revealed. Taking this into account, an experimental study was conducted with the measurement of the mode parameters of the high-frequency current inductor affecting the properties and quality of the melted surfaces obtained on cylindrical samples of ferritic steel wear-resistant coatings based on the PR-NH17SR4 self-fluxing alloy sprayed by the gas-flame method on nickel. It was shown that, using this hybrid technology, in particular, at an inductor power of 80–100 kW and a field frequency of 53 kHz, it is possible to obtain wear-resistant coatings, moreover, dispersion-hardened, as is assumed, due to microinclusions of phases of borides, silicides, and carbides of chromium and iron crystallizing in the metal matrix, with a sufficiently high level of microhardness of the melted layers (≥60 HRC) with a thickness of up to 750 μm and higher, and not containing cracks in the melted coating. Specific energy consumption achieved in the tested version of coating formation on steel parts using high-frequency melting are still somewhat higher than the level (about 4–5 kWh per 1 m² of coating) demonstrated in recent years in a number of studies (in particular in the Russian Federation).

Based on the combined use of the method of mathematical modeling of the process of electric discharge impact on the bottom-hole zone of a water intake well and a physical experiment, the pressure distribution on the surface of the casing pipe was determined. Based on physical experiment data, the mathematical model was verified and refined under conditions of low capacitance of the capacitor bank and low inductance of the discharge circuit. The readings of the pressure sensor on the surface of the casing pipe were coordinated with the results of mathematical modeling taking into account the interrelated physical processes in the discharge circuit, the discharge channel, and the liquid filling the casing pipe of the water well.

Coatings based on the Ti–Cu–N system were obtained from separated plasma flows by vacuum-arc deposition. The effect of reaction gas pressure on the electrochemical behavior of coatings has been studied. The study of the relationship between the elemental, phase composition of Ti–Cu–N coatings and their electrochemical characteristics showed that coatings with a copper concentration of 4–7 at % in their composition are characterized by low values of the anodic dissolution current density, which is due to the corrosion resistance of copper located along the grain boundaries of titanium nitride. Increasing the copper content to 12 at % leads to the formation of a two-phase coating based on Ti₂N and СuN₃, which, as a result, reduces its corrosion resistance. The study of the corrosion resistance of the multilayer TiN/TiCu (7 at %)N/TiN/TiCu(7 at %)N coatings showed that layer-by-layer deposition makes it possible to reduce the current density of the anodic dissolution of the multilayer coating by a factor of four compared to the single-layer TiCu(7 at %)N, which is due to the increased length of interphase boundaries, a decrease in porosity, and structural heterogeneity.

The structure of the cathode spot of the vacuum arc of the alloy is presented. It is shown that there are regions of predominant ionization of alloy components atoms by electrons in the plasma cloud of the cathode spot.

The specific features of electrodeposition of coatings from a room-temperature ionic liquid based on a eutectic mixture of choline chloride and ethylene glycol, in which a trivalent chromium salt is dissolved, were considered. The influence of the water content in the electrolyte on the kinetics of electrode processes and the electrodeposition of electrodeposits was shown. It has been established that the introduction of additional water leads to an increase in the current density of the irreversible discharge of Cr(III) ions on a glassy carbon electrode due to a significant decrease in the viscosity of the solution. Coatings deposited from an electrolyte based on a room-temperature ionic liquid demonstrate an increased electrocatalytic activity in the reaction of hydrogen evolution in an alkaline medium. A change in the water content in the chromium plating electrolyte is a factor that allows modulating the electrocatalytic activity of electrodeposits via a controllable change in their chemical composition and surface morphology features.

The regularities of sintering of finely dispersed mechanically activated powders, which differ from the known sintering processes of aluminosilicates by the synthesis on the surface of particles of aggregates of chemically and wear-resistant SiC compounds with sizes of 200–500 nm and that establish a relationship between the conditions for the formation of silicon carbide in the aluminosilicate–C system, have been studied, which made it possible to develop the foundations of a controlled process formation of porous materials with a microfiltration layer of carbon-containing compounds on an aluminosilicate basis.

The effect of powerful ultrasonic oscillations (USO) on the microstructure and phase composition of the self-propagating high-temperature synthesis (SHS) products in the Ti–B binary system is studied. It is demonstrated that the application of USO during the synthesis leads to a change in the microstructure and phase composition of the synthesis products and allows one to exert an operational influence on the resulting final product.