Surface Engineering and Applied Electrochemistry最新文献

Structural features of electrospark coatings formed on metal substrates of different nature depending on the chemical composition, the nature of the substrate, and the conditions of deposition of superhard layers are studied. It is shown that the above parameters have a fundamental effect on the physicomechanical and chemical properties of coatings. The formation of nanophases and MAX-phases in the structure of electrospark coatings during their deposition on metal substrates has been established. A change in the energy parameters during the formation of coatings can lead to an intensification of ordering processes in the coating structure, which has a positive effect on the physical and mechanical properties of the modified metal substrates.

The article presents the results of studies on modeling and optimizing the structure of refractory nonmetallic materials with a rigid system of transport pores formed by sintering basalt fibers. Based on the analysis of the images of the structures, it is shown that the Kozeny approach can be chosen as an approximate model for calculating and optimizing the characteristics for a combination of two media: a medium formed by ceramic fibers and a medium in the form of a rigid system of transport pores. Moreover, the interpenetration of media obeys a normal distribution. It has been established by calculation that the optimal structure with a porosity of 52–75% is characterized by an average pore size of 20–25 µm, a permeability coefficient (2–3) × 10^–10 m², and a compressive strength of 7–21 MPa. The calculated values are confirmed by experimental results. The conducted studies prove that the porous material made of basalt fiber is able to provide better filtering characteristics compared to analogues.

The features of surface alloying of Hardox 600 steel using B₄C, WC, and Ni powders based on exposure to ytterbium fiber laser radiation are studied. The study of the geometric dimensions, quality, and structure of the surface layers was carried out. The laser-processing modes for steel were selected depending on the power density of the laser radiation of the installation, the linear velocities of the beam, and the diameter of the laser spot. It is shown that the doping process is critical to the regimes of laser action. At a radiation power of ~2 kW, high-quality doping zones can be observed more stably over the entire range of laser beam scanning speeds under study. With an increase in the depth of the alloying zone when using B₄C, the microhardness decreases, which is associated with a decrease in the concentration of introduced alloying elements. The microhardness of the layer can vary in the range of 7300–16 000 MPa.

Research into the influence of the carbon content in AlCrCN coatings on their phase composition and structure were carried out. A carbon solid solution was found to form in coatings when deposited by the cathodic-arc method in the acetylene gas atmosphere. The formation of the coatings having the B1-type phase structure and the [200] texture axis provided a level of their hardness at 3300 HK. The formation of a tribolayer consisting of oxides of the particles of both the coating and the counterbody was studied, leading to a friction coefficient of 0.6, without using a lubricant. The coating showed an almost twofold increase in adhesion to a Kh12MF die steel base material, and the carbon-containing coating showed an increase in crack resistance as compared to the AlCrN coating.

Mathematical modeling has been used to study heat transfer during five-layer casting of impact liners from wear-resistant chromium cast iron. From the analysis of the calculated temperature fields, a number of patterns that showed a significant difference from heat transfer during casting as whole have been obtained. Experimental testing has revealed significant refinement of the carbide component in cast iron in the depth of the casting.

The resistance and emission properties of films obtained on silicon and sitall substrates by direct current magnetron sputtering of CrSi₂, WSi₂, and MoSi₂ targets were investigated. The effect of high-temperature current heating and thermal annealing on the electrical resistivity of the films was studied. It was found that the films obtained by sputtering of WSi₂ and MoSi₂ targets withstand multiple current pulse heating to a temperature of at least 900°C. The films obtained by sputtering of CrSi₂ target are destroyed under the action of the first current pulse when the temperature reaches 700°C. The heat resistances of the films obtained by sputtering of WSi₂ and MoSi₂ targets during stationary constant thermal heating at a temperature of 800°C in air are 14 min and 6 h, respectively. Heat treatment of all the studied films at a temperature of 900°C for 3 h leads to stabilization of the electrical resistivity of the films. It was determined that the emissivities of the films obtained by sputtering of CrSi₂, WSi₂, and MoSi₂ targets are 0.7, 0.75, and 0.8, respectively. It was found that the films obtained by sputtering of MoSi₂ target have optimal properties for use in IR emitters operating at a temperature of 700–800°C.

The aim of the work was to study the structure, phase composition, and hardness of composite gas-thermal coatings of the Cu–Al system, sprayed by hypersonic metallization using industrial wire materials from welding bronze CuSi3Mn1 and aluminum alloy AlSi12. It is shown that interdiffusion occurs between the bronze and aluminum interlayers during the sprayed of coatings and the intermetallic compounds Cu₉Al₄, CuAl₂, and Cu₃Al are formed. The porosity of the sprayed coatings did not exceed ≈10 vol %. The hardness of the composite coatings was 180–190 HV 1, and their microhardness was 180–240 HV 0.025. It has been established that annealing coatings of the Cu–Al system at 175 and 225°С for 2 h leads to an increase in the content of intermetallic compounds in them as well as an increase in their microhardness to 260 HV 0.025. It is concluded that the composite coatings of the Cu–Al system, obtained by the method of hypersonic metallization, can be used as an antifriction material for friction pairs.

It was shown that, to ensure import substitution of bearings and improve the quality of bearing steel produced in Belarus, it is necessary to study the structure of original bearings manufactured by leading foreign companies, the products of which are known for their high quality and are in high demand in the world market. The composition of the material of bearing rings, and the microstructure and morphology of the metal matrix and carbide inclusions were studied by optical and scanning electron microscopy at magnifications from 1000 to 20 000, emission spectroscopy, and electron probe microanalysis. It was demonstrated that the high quality of bearing steel is ensured by the fine-grained structure of martensite, uniform distribution of dispersed carbides (Fe, Cr)₃C with a size of about 1 μm, and low content of detrimental impurities (sulfur and phosphorus) and nonmetallic inclusions. The results of the studies can be used to improve the production technology of high-quality bearing steels at OAO BMZ—Management Company of BMK Holding within the framework of the import substitution program.

The optical properties of transparent conductive coatings based on an aluminum grid embedded in anodic aluminum oxide have been studied. The coatings were formed by local porous anodizing of an aluminum film deposited on a glass substrate. The conductivity of the coating samples produced reaches the equivalent of the conductivity of films with a surface resistance of 1.0 Ohm/square. The transmittance of the best sample of coatings averaged over the visible wavelength range reaches 89%, which is comparable with the best modern transparent conductive coatings.

Experimental data on the content of alloying elements in structural steels 40Kh and 38Kh2MYuA are presented. The results of calculating the hardness increase of the nitrided layer depending on the concentration of alloying elements, as well as experimental data on the hardness increase of the nitrided layer for the specified steels, are provided.