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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.

This work shows the results of research of the fine and dislocation structure of the transition layer of 18CrNi3Mo low-carbon steel after the influence of electrolytic plasma. Conducted research has shown that the modified steel layer, as a result of carbonitriding, was multiphase. Quantitative estimates were made for carbonitride М23(С,N)6 in various morphological components of α-martensite and on average by material in the transition layer of nitro-cemented steel. It was established that α-phase is tempered martensite after nitrocementation. Released martensite is represented by batch, or lath and lamellar low-temperature and high-temperature martensite. Inside the tempered martensitic crystals, lamellar cementite precipitates are simultaneously present, and residual austenite is found along the boundaries of the martensitic rails and plates of low-temperature martensite. It was determined that inside the crystals of all morphological components of α-martensite there are particles of carbonitride М23(С,N)6.

The features of the formation of low-temperature plasma and its interaction with a metal surface were studied in this work. A qualitative model of the interaction of low-temperature plasma with the steel surface during nitriding has been developed by summarizing the available research results and taking into account the specific features of the electrolyte plasma process. In accordance with this model, in the first moments of the interaction of low-temperature plasma with the steel surface in the near-surface layer, which accelerated formation of the Feα(N) solid solution occurs due to the action of directed bombardment of charged particles, which enhances the adsorption and diffusion of nitrogen into the interior of the material, then dispersed particles of nitride of alloying elements are formed as further saturation in places with an increased level of free energy (at lattice defects, at grain boundaries, etc.). Subsequently, transformations occur in the surface zone of the layer when the limiting solubility of nitrogen in iron is exceeded, which leading to the formation of nitrides of the γ′-phase (Fe4N) and ε-phase (Fe2–3N) in it. Thus, electrolyte plasma nitriding opens up many new possibilities, in particular: varying the nitriding temperature over a wide range (400–700 ºC), targeted production of a nitrided layer consisting only of a diffusion layer without a layer of compounds, while obtaining a diffusion layer with particles γ’-phase (Fe4N) of plate form and with finely dispersed nitrides MN (CrN). The use of an electric discharge in an electrolyte (low-temperature plasma) makes it possible to increase the heating rate and diffusion saturation of the material surface. This work is of practical importance, since the studied method of electrolytic-plasma nitriding makes it possible to obtain a modified surface layer on steels with high physical and mechanical properties.

The article presents the results of studying the process of electrolytic-plasma hardening of 0.34Cr-1Ni-Mo-Fe steel by surface hardening, as well as the results of the current-voltage characteristics of the cathodic electrolytic-plasma process depending on the composition of the electrolyte. Temperature-time and special modes of electrolytic-plasma hardening of steel 0.34Cr-1Ni-Mo-Fe were determined. The optimal composition of the electrolyte for electrolytic-plasma hardening has been determined, providing a relatively high heating rate and high hardness of the steel surface. It has been determined that after the electrolytic-plasma hardening, the microhardness of 34KhN1M steel increases 2.9 times due to the formation of fine martensite. In this case, the basis of the material does not change, it consists of a ferrite-pearlite structure.

Structural-phase transformations in 0.34C–1Cr–1Ni–1Mo–Fe steel during plasma electrolytic hardening were investigated. Electrolytic-plasma hardening of steel samples was carried out by surface quenching with rapid concentrated heating of the surface by plasma action and subsequent rapid cooling by heat removal from the depth of the sample by electrolyte jet. Plasma electrolytic hardening was carried out in the cathode mode in an electrolyte made from an aqueous solution containing 20 % sodium carbonate and 10 % carbamide. To study the structural-phase states of the modified layer, we used the method of transmission diffraction electron microscopy on thin foils. The study of steel samples was carried out before and after the plasma electrolytic hardening. Initially, the steel was a mixture of pearlite and ferrite grains. Surface hardening of 0.34C–1Cr– 1Ni–1Mo–Fe ferrite-pearlite steel led to a change in the structural-phase state and the formation of a packet-lamellar martensite structure. It was found that PEH leads to distortion of the crystal lattice and the formation of long-range internal stresses, as well as to the release of small particles of cementite and carbide of M23C6 type, uniformly distributed throughout the volume of the material. Surface hardening led to the increase in all quantitative parameters of the fine structure (ρ, ρ±, χ, σL, σd).

In order to obtain the modified surface structure of the 20Cr2Ni4A steel plasma electrolytic hardening (PEH) method was used. The surface hardening process was conducted in the aqueous electrolyte solution of 20% sodium carbonate and 20% urea. The sample consists of a ferritic-pearlitic structure, i.e. the part retains its viscous core, and the surface layer contains carbide particles. Hardening process induces martensite transformation and creation of carbide particles in the surface layer. The presence of carbide particles in the surface layers has a positive effect on the tribo-mechanical performance. Hardened structure 600 μm long was obtained with hardness increase up to 520 HV and 2.5 times higher wear resistance. Tribological test results showed the difference of the coefficient of friction as a function of surface roughness determined by plasma-electrolytic hardening process.

This paper examines the influence of electrolyte-plasma surface hardening on the structure and microhardness of wheel steel mark 2. In the work electrolyte-plasma surface quenching was carried out in an electrolyte made from an aqueous solution of 10% carbamide (NH2)2CO+20% sodium carbonate Na2CO3 . The work investigated the strength limit, fluidity and wear intensity of the wheeled steel after electrolyte-plasma surface quenching. After electrolytic-plasma surface quenching, a batch, high-temperature plate and low-temperature plate martensit is formed on the surface of the sample. Investigations have been carried out on microhardness determination on cross-section of wheel steel samples after quenching in aqueous solution of electrolyte. It is found that after electrolytic-plasma surface quenching, the microhardening values of this hardened surface layer increased on ≈ 3 times compared to the steel matrix, and the thickness of the hardened layer is 1000-1500 µm. According to the results of the scanning transmission electron microscopy, the electrolyte-plasma surface quenching caused a change in the morphological constituents of steel mark 2. In the initial state, the matrix of steel is a α -phase, the morphological components of which are fragmented ferrite, unfragmented ferrite and pearlite.

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.

The article examines the changes of the structural-phase states and the microhardness of the R6M5 steel surface layer after electrolytic-plasma nitriding. It is found that after electrolytic-plasma nitriding of the R6M5 steel surface, diffusion layer is formed, which is a nitrogen martensite. The phase composition of the diffusion layer varies depending on the nitriding temperature. An increase of R6M5 steel microhardness, depending on structural-phase state, is found out. The main factor, influencing the increase of microhardness of R6M5 high-speed steel with electrolytic-plasma nitriding, is the formation of nitrogen martensite with monophasic nitride Fe4N ( γ′- phase), as well as the formation of fine inclusions, hardening phases in the surface layers.

In this work, bioceramic coatings were formed on Ti6Al4V titanium alloy using a combined technique of plasma electrolytic oxidation followed by gas detonation spraying of calcium phosphate ceramics, based on hydroxyapatite. Plasma electrolytic oxidation was carried out in electrolytes with various chemical compositions, and the effect of electrolytes on the macro and microstructure, pore size and phase composition of coatings was estimated. Three types of electrolytes based on sodium compounds were used: phosphate, hydroxide, and silicate. Plasma electrolytic oxidation of the Ti–6Al–4V titanium alloy was carried out at a fixed DC voltage (270 V) for 5 min. The sample morphology and phase composition were studied with a scanning electron microscope and an X-ray diffractometer. According to the results, the most homogeneous structure with lower porousness and many crystalline anatase phases was obtained in the coating prepared in the silicate-based electrolyte. A hydroxyapatite layer was obtained on the surface of the oxide layer using detonation spraying. It was determined that the appearance of α-tricalcium phosphate phases is characteristic for detonation spraying of hydroxyapatite, but the hydroxyapatite phase is retained in the coating composition. Raman spectroscopy results indicate that hydroxyapatite is the main phase in the coatings.

In the article the formation peculiarities of the modified layer at R9, R6M5 R18 high-speed steels (HSS) after electrolytic-plasma nitriding are shown. It is established that in the result of electrolytic-plasma nitriding on the of high-speed steels samples surfaces formed modified layers with higher hardness. Hardness of HSS increased to 11.9-12.8 HPa after electrolytic-plasma nitriding, mainly depends to the formation of a diffusion layer of nitrogen martensite with Fe4N (γ’-phase) monophasic nitride. It is determined that a modified layer consists of nitrogenous martensite with Fe4N monophasic nitride. Perspectivity of use an electrolytic-plasma nitriding method to improve performance cutting tools made of high speed steels is shown.

In the article changes in the structure and mechanical properties of R6M5 steel surface layer after electrolytic-plasma nitriding are shown. The optimal mode of electrolytic-plasma nitriding of R6M5 high-speed steel in electrolyte based on carbamide, which allows saturation of the surface with nitrogen from low-temperature plasma and get the modified layer of high hardness and wear-resistance. It is established, that after electrolytic-plasma nitriding reduced R6M5 steel wear rate and increases its resistance to abrasive wear. Perspectivity of use an electrolytic-plasma nitriding method to improve performance cutting tools made from R6M5 steel is shown.

Developed a new method of electrolytic-plasma nitriding, which enable to carry out surface modification of high-speed steels and provide the high kinetic energy efficiency of diffusion saturation process. . Implementation of electrolytic-plasma nitriding of high-speed steel R6M5 in the optimal mode was determined, which leads to a significant increase in hardness and wear-resistance of the high-speed steel surface layer. It is experimentally established, that after nitriding of electrolytic-plasma heating on the surface of high-speed steel R6M5 formed the modified layer, which has high abrasive wear resistance as compared with the source material.

This paper presents research of influence electrolyte plasma carbonitriding on tribological properties of R6M5 high-speed steel. Shows perspectiveness of carbonitriding high-speed steels in electrolyte plasma. The results of research demonstrated increasing wear-resistance of R6M5 steel after carbonitriding in electrolyte plasma. Under the same test conditions by the method of scratch-test have been determined that the depth of the scar of a modified layer has become less in comparison with the original sample, which indicates a significant increase of wear-resistance and hardness of the surface carbonitriding layer R6М5 steel. It was set that after electrolytic-plasma carbonitriding abrasive wear-resistance of the surface layers of R6M5 steel is increased by 25%. Introduction

Mechanical characteristics of nitrated and carbonitriding in electrolyte plasma steel Р6М5 surface layers are investigated in the research. It shows perspectiveness of the cutting tool electrolyte-plasma treatment technology. Comparative research of structure, phase composition of fast-cutting P6M5 steel modified surface layers after electrolyte plasma treatment was carried out by scanning-electron and light microscopy, and X-ray structure analysis methods.

Microhardness of nitrated and carbonitriding in electrolyte plasma steel Р6М5 surface layers are investigated in the research. It shows perspectiveness of the cutting tool electrolyte-plasma treatment technology. Operating conditions for the technology realization are defined. It was also indicated the desired content of components in saturating mixtures by nitriding and carbonitriding. Comparative research of structure, phase composition of fast-cutting P6M5 steel modified surface layers after electrolyte plasma treatment was carried out by scanning-electron and light microscopy, and X-ray structure analysis methods. The way of electrolytic plasma nitriding in cathodic mode, to provide fast-cutting steels which allows for modification the surface and high kinetic efficiency the process diffusion saturation. It was established that as a result of nitriding and nitrocarburizing in plasma electrolyte has been a significant increase in microhardness in the surface layers of steel Р6M5.

This work is devoted to formation of modified surface layers in 65G and 20GL steels which using for the manufacture of railway transport parts, as well as the study of influence of the parametersof electrolyte-plasma surface hardening methodon the changes in structural-phase states, improving of wear-resistance. The process of electrolyte-plasma surface hardening of 65G and 20GL steels samples conducted in the electrolyte from water solution of 20% sodium carbonate, in the mode ~850°C - 2 seconds, ~1200°C - 3 seconds. It is established that in the initial state 20GL steel has ferrite-pearlite structure, and the 60G steel consists of pearlite and cement structure. After application of electrolyte-plasma surface hardening is observed the formation of carbides particles and martensite phase components in the structure of 20GL and 60G steels. It is determined that after electrolyte-plasma surface hardening with heating time - 2 seconds, the abrasive wear-resistance of 65G and 20GL steels increased to 1.3 times and 1.2 times, respectively, and the microhardness is increased to 1.6 times and 1.3 times, respectively.