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This work presented a study of the structure, hardness and wear resistance of 65G steel treated with electrolyte-plasma hardening under different conditions. The electrolyte-plasma hardening technology and a laboratory installation for the realisation of electrolyte-plasma hardening are also described. After electrolyte-plasma hardening, we have established that a modified layer consists of the a-phase (martensite) and M3C cementite. The study results showed that electrolyte-plasma hardening makes it possible to obtain layers on the 65G steel surface that provides an increase in microhardness by 2.6 times, wear resistance by two times, resistance to abrasive wear by 1.7 times compared to the original samples. In addition, local hardening ensures the achievement of technical and economic effects due to the absence of the need to isolate an unwanted site of parts, processing only the areas requiring hardening.

The article presents the study results of detonation spraying parameters on the phase composition and tribological properties of NiCr-Al2O3 powder coatings. The spraying was carried out at a ratio of the acetylene-oxygen mixture O2 /C2H2=1.856. The detonation barrel filling volume with an explosive gas mixture varied from 30% to 68%. It is determined that the phase composition of the NiCr-Al2O3 coatings varies depending on the degree of detonation barrel filling. With an increase in the detonation barrel’s filling volume, the intensity of the NiCr diffraction peaks is decreased, and the intensity of the a-Al2O3 reflexes is increased, which indicates an increase in the content of the Al2O3 phase. When low filling volume, there is determined a low coating density and uneven roughness. The tribological test results showed that with an increase in the detonation barrel filling volume, there is a decrease in the wear volume, which confirms the increase in the coatings wear resistance. Determined that the lowest friction coefficient was recorded in the sample obtained at the barrel filling volume 68%. The coatings’ high wear resistance is associated with an increase in the alpha phase volume fraction of a-Al2O3 and coatings density.

In work considers the results of studies of the phase composition and mechanical-tribological properties of Ni-Cr detonation coatings obtained at different values of the volume of filling the detonation barrel with an explosive acetylene-oxygen mixture. Analysis of the obtained experimental results indicates that the phase composition and properties of detonation coatings strongly depend on the technological parameters of spraying. When the barrel is filled with an explosive gas mixture of 40%, the coating is not dense enough, with noticeable boundaries between individual particles, which may be the result of insufficient heating and acceleration of the particles of the sprayed powder. It is determined that when the volume of filling the detonation barrel with an explosive mixture is up to 60%, there is a widening and a decrease in the intensity of the main peaks. Higher values of microhardness were obtained at 50% filling of the barrel. The results of tribological tests of coatings showed that the coating applied when filling the detonation barrel with an explosive mixture of up to 60% has a lower coefficient of friction than other coatings.

The results of experimental studies of changes in the structure, microhardness, and wear resistance of the AMG6 aluminum alloy during equal channel angular pressing (ECAP) are presented in this work. The evolution of the fine structure and the formation of secondary phases in the AMG6 alloy during ECAP were studied. The dark-field image of the structure of the AMg6 alloy in the matrix reflex showed the splitting of the material into small disoriented fragments of about 0.5 μm in size with a small-angle disorientation boundary (about 2–5°). Optimal method and modes of ECAP of the AMG6 aluminum alloy were selected of the bases of experimental research, which make it possible to obtain a workpiece with enhanced tribological and mechanical characteristics. It was established that the most intensive grinding of the grain structure in the AMG6 alloy occurs at ECAP-12 at a channel angle intersection of 120°. It is shown that with a decrease in grain size, the microhardness of the alloy AMG6 after ECAP increases by 4 times, compared with the initial state.The results of the test samples for abrasive wear showed a decrease in mass loss after 12 passes of ECAP, which indicates an increase in the wear resistance of the alloy AMG6 by 13–14 %, compared with the initial state.

This article investigates the influence of thermal annealing on microhardness and wear resistance of the surface of steel U9/Y9 protected by a composite coating Ti 3 SiC 2 /TiC obtained by detonation sputtering. Thermal annealing was performed in the range of temperatures 700-900 ◦ C during 1 hour. Following annealing the formation of TiO 2 and an increase in the phase content of Ti 3 SiC 2 are observed. Higher microhardness was obtained in coatings subjected to annealing at 800 ◦ C, which can be explained by an increase in the content of carbonized titanium. As the annealing temperature rises further, the thickness of the oxide layer increases, leading to a decrease in the microhardness for the coatings annealed at 900 ◦ C. According to the results of tribological tests, formation of the oxide increases wear resistance of Ti 3 SiC 2 /TiC composite surface coatings.

This paper investigates the influence of the technological parameters of detonation spraying on the phase composition of NiCr- and Al2O3-based coatings. It was determined that the phase composition of Al2O3 coatings during detonation spraying strongly depends on the barrel filling volume with the gas mixture. The acetylene–oxygen mixture, which is the most frequently used fuel in the detonation spraying of powder materials, was used as a fuel gas. To obtain a ceramic layer based on Al2O3, spraying was performed at an acetylene–oxygen O2/C2H2 mixture ratio of 1.856; the volume of filling of the detonation gun barrel with an explosive gas mixture was 63%. To obtain a NiCr-based metallic layer, spraying was performed at the O2/C2H2 ratio of 1.063; the volume of filling of the detonation gun barrel with an explosive gas mixture was 54%. Based on a study of the effect of the detonation spraying mode on the phase composition of NiCr and Al2O3 coatings, NiCr/NiCr-Al2O3/Al2O3-based multilayer coatings were obtained. Mixtures of NiCr/Al2O3 powders with different component ratios were used to obtain multilayer gradient coatings. The structural-phase composition, mechanical and tribological properties of multilayer gradient metal–ceramic coatings in which the content of the ceramic phase changes smoothly along the depth were experimentally investigated. Three-, five- and six-layer gradient coatings were obtained by alternating metallic (NiCr) and ceramic (Al2O3) layers. The phase composition of all coatings was found to correspond to the removal of information from a depth of 20–30 μm. It was determined that the five-layer gradient coating, consisting of the lower metal layer (NiCr), the upper ceramic layer (Al2O3) and the transition layer of the mechanical mixture of metal and ceramics, is characterized by significantly higher hardness (15.9 GPa), wear resistance and adhesion strength.

The structural-phase state and tribological characteristics of detonation coatings based on Ti–Si–C before and after pulsed-plasma exposure have been experimentally investigated. The authors of the research used a detonation set-up of CCDS2000 to obtain coatings. The modification of coating surfaces was carried out by a pulsed-plasma flow using the “Impulse-6” installation. The results of the research have shown that the modification of coatings surface by a pulsed-plasma effect causes an increase in the microhardness of the surface layer and in its wear resistance. It was determined that after such type of treatment, there is an increase in the content of the Ti3SiC2 phase. According to the results of XRD analysis, the improvement in the mechano-tribological properties of detonation spraying coatings of the Ti–Si–C system as a result of pulsed-plasma treatment is associated with an increase in the content of Ti3SiC2 phases in the coatings, as well as the formation of carbide and oxide phases on the surface layer.

This work is devoted to the research of the influence of the technological parameters of electrolytic-plasma surface hardening on the structure and tribological properties of the surface of samples of the retaining steel mark 2. In the electrolytic-plasma surface hardening was carried out in an electrolyte from an aqueous solution of 20% urea and 20% sodium carbonate. According to the result of metallographic and X-ray diffraction analysis, it was determined that the phase composition of steel mark 2 after processing varies, and fine martensite with a small amount of troostite and iron oxide is formed on the surface of the samples. Tribological experiments of samples without lubrication were carried out. These experiments have shown that all the studied samples have an increased wear resistance, which may be associated with the formation of a fine-grained martensitic structure. It was shown that from the point of view of the complex of the properties obtained, the most promising is electrolytic-plasma action with a treatment time of 2 s.

This work presents the results of the study on the effect of pulse-plasma treatment on the structural-phase states of the surface layer of detonation coatings based on Ti3SiC2. Structural-phase studies were carried out by three main methods: scanning electron microscopy, transmission electron diffraction microscopy on thin foils and X-ray structural analysis. It was determined that after the pulse-plasma treatment, an increase in the intensity of the Ti3SiC2 peaks was observed, and the appearance of new reflections (101, 102, 112, 204, 1110, 0016) of this phase was detected, which indicates the increase in the MAX-phase content. It was determined that after the pulse-plasma treatment, the fraction of voids (pores) and the particle area decreased and the microstructure became more homogeneous, which resulted in the densification of the Ti3SiC2-based detonation coating. It was found that the process of detonation spraying with subsequent pulse-plasma treatment resulted in the formation of a Ti3SiC2-based coating, with TSC carbosilicide (Ti3SiC2) 0] plane reflexes, lamellar layered structure, and reduced porosity.

The paper considers the research results of structural-phase state and tribological characteristics of detonation coatings based on Ti&ndash, Si&ndash, C, obtained at different filling volumes of the explosive gas mixture barrel of a detonation gun. The results analysis indicates that the phase composition and properties of detonation coatings strongly depend on the technological parameters of spraying. With an increase of the explosive mixture in the filling volume of the detonation barrel up to 70% of the coatings consist mainly of the TiC phase, because high temperature leads to a strong decomposition of Ti3SiC2 powders. Thus, the XRD results confirm that at 70% of the explosive gas mixture&rsquo, s filling volume, partial decomposition and disintegration of the powders occurs after detonation spraying. We established that detonation coatings based on titanium carbosilicide obtained at the explosive gas mixture&rsquo, s filling volume at 60% are characterized by high wear resistance and adhesive strength. Thermal annealing was performed after spraying in the temperature range of 700&ndash, 900 &deg, C for 1 h to reduce microstructural defects and improve the Ti&ndash, C coating characteristics. As a result of the heat treatment in the Ti&ndash, C system at 800 &deg, C, we observed that an increase in the volume fraction of the Ti3SiC2 and TiO2 phases led to a 2-fold increase in microhardness. This means that the after-heat-treatment can provide a sufficient reaction time for the incomplete reaction of the Ti&ndash, C (TSC) coating during the detonation gun spraying. Thus, annealing can provide an equal distribution of elements in the coatings.

This study is aimed at obtaining a coating of aluminum oxide containing α-Al2O3 as the main phase by detonation spraying, as well as a comparative study of the structural, tribological and mechanical properties of coatings with the main phases of α-Al2O3 and γ-Al2O3. It was experimentally revealed for the first time that the use of propane as a combustible gas and the optimization of the technological regime of detonation spraying leads to the formation of an aluminum oxide coating containing α-Al2O3 as the main phase. Tribological tests have shown that the coating with the main phase of α-Al2O3 has a low value of wear volume and coefficient of friction in comparison with the coating with the main phase of γ-Al2O3. It was also determined that the microhardness of the coating with the main phase of α-Al2O3 is 25% higher than that of the coatings with the main phase of γ-Al2O3. Erosion resistance tests have shown (evaluated by weight loss) that the coating with α-Al2O3 phase is erosion-resistant compared to the coating with γ-Al2O3 (seen by erosion craters). However, the coating with the main phase of γ-Al2O3 has a high value of adhesion strength, which is 2 times higher than that of the coating with the main phase of α-Al2O3. As the destruction of coatings by the primary phase, α-Al2O3 began at low loads than the coating with the main phase γ-Al2O3. The results obtained provide the prerequisites for the creation of wear-resistant, hard and durable layered coatings, in which the lower layer has the main phase of γ-Al2O3, and the upper layer has the main phase of α-Al2O3.

In this paper, Ni–Cr–Al coatings were deposited using the detonation spraying method. The aim was to investigate how technological parameters influence coating structure formation, phase composition and tribological performances. We observed that the degree to which the barrel is filled with an O2/C2H2 gas mixture strongly influences the chemical composition of manufactured coatings. High degrees of barrel filling led to a decrease in aluminum content in the coating. Filling degrees of 40% and 50% produced sprayed coatings in which only Ni–Cr phases could be found. When the filling degree was reduced up to 25%, Ni–Al phases began to form in the sprayed coatings. Gradient Ni–Cr–Al coatings were produced by gradually reducing the filling degree from 50% to 25%. These coatings are characterized by Ni–Cr near the substrate level with Ni–Cr and Ni–Al phases at higher levels. The results obtained confirm that gradient Ni–Cr–Al coatings exhibit high hardness as well as good wear resistance.

In this work the influence of electrolytic-plasma nitriding on the abrasive wear-resistance of R6M5 high-speed steel were under research. We registered that after electrolytic-plasma nitriding on R6M5 steel surface modified layer is formed with 20-40 μm thickness and with increased microhardness of 9000-12200 MPa. Testing mode for the nitrided samples high-speed steel on abrasive wear developed. It is established, that electrolyte-plasma nitriding allows to increase wear-resistance of R6M5 steel surface layer comparing to original. It was determined that abrasive wear-resistance of R6M5 steel surface layer is increased to 25% as a result of electrolytic plasma nitriding. Thus, studies have demonstrated the feasibility and applicability of electrolytic-plasma nitriding in order to improve cutting tools work resource, working under friction and wear conditions.