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The equations for predicting the quality parameters of the coatings is proposed, which allow predicting structural parameters (thickness, continuity), mechanical properties (microhardness) and geometric parameters (roughness) based on the energy indicators of the electrospark alloying, such as discharge energy, as well as process productivity, and, therefore, to establish purposefully an algorithm for further governing of the surface properties of parts. The recommended algorithm allows determining the most rational way of forming of surface layers with a demand quality. The technique is tested for the fabrication of coatings on the cathode of steels 20 and 40 using aluminium as an anode. [ABSTRACT FROM AUTHOR]

The analysis of the defects of parts of the friction units of aviation equipment under the conditions of abrasive wear was carried out. Types of electrode materials for modification of parts by electrospark alloying are considered. The mechanisms of wear under the influence of free abrasive of electrospark coatings of 1.1645 and 1.3355 steels, HG30 alloy and ZLAB-1 ceramics on structural steels 30HGSA and 45 were analyzed. The dependence of the intensity of wear of electrospark coatings on the hardness of carbides and borides and the ratio of the strengthening phase in the matrix was determined. The low wear resistance of the ceramic coating ZLAB-1 is due to the presence of the boride component ZrB2 of increased microhardness in the matrix phase, which leads to the brittleness of the coating. The predominance of brittle fracture of ESC of 1.1645 steel is caused by the presence of iron carbide up to 16% in the structure of secondary cementite and pearlite of the steel. The increase in wear resistance of ESC made of 1.3355steel is due to the presence of a large amount of W, V and Mo carbides. The phase inhomogeneity of ESC made of HG30 alloy, established by X- ray structural and phase analysis of the coating diffractograms and the activation of oxidation processes during friction lead to an increase in the wear resistance of ESC due to the appearance of W2C tungsten semi-carbide and WC1-x tungsten semi-carbide phases. The obtained results indicate the prospects of ESC made of 1.3355 steel and HG30 alloy with the necessary level of properties to increase the wear resistance of structural steels. [ABSTRACT FROM AUTHOR]

The nature of the stress state arising under sliding friction loading is investigated on the model of a discretely processed material in which there is an annular transition zone between the inclusions (hardened area) and the matrix according to the known law of change in its mechanical properties. It is shown that local stresses in the material, depending on the type of loading of the elementary volume, can be predicted and calculated, taking into account the mechanical properties, appearance, and structure of the transition zone that occurs as a result of laser processing. The strength of the transition zone has a linear dependence and the stress concentration in the area after laser treatment decreases and smoothly transitions to the matrix, and then it decreases to the stresses in the matrix, which gives the advantage of discrete laser treatment of hardened steel. [ABSTRACT FROM AUTHOR]

The development of biocompatible materials is a multidisciplinary task and requires the interaction of physicists, chemists, biologists, and physicians, since the functional reliability of materials depends on their biochemical, cellular, tissue, and biomechanical compatibility. This area has been developing intensively in recent years, resulting in numerous research articles. As assumed, the composition of the biocompatible coating of the new generation should coincide as much as possible with the composition of natural human bone and be able to simulate bone tissue on its surface. As a result of the approximation of the phase-structural state and properties of the resulting coatings on implants to the parameters of bone tissue, improved compatibility between them can be achieved. When forming biocompatible coatings, special attention is paid to creating a definite relief (roughness) on the implant surface. There is a current search for new technological solutions for creating a biocompatible rough surface on implants that ensures reliable integration of the implant into bone tissue, since existing technologies do not fully meet state-of-the-art medical requirements.

The research results on the structure, phase composition, and properties of detonation coatings produced by spraying a mechanical mixture of Fe powders and AlMg and TiAl alloys, as well as composite powders of the same composition synthesized by the mechanochemical method, are presented. It was found that in the coatings produced with the use of mechanical mixtures of powders, the synthesis of intermetallic compounds does not occur and the coatings consist of initial components and their oxides. Therefore, it is advisable to use powders produced by the method of mechanochemical synthesis as spray materials. This results in the formation of coatings, in which the main phase is the Fe-Al intermetallic compound. Coatings of the Fe-AlMg and Fe-TiAl systems, produced by spraying of composite powders, are characterized by a dense lamellar structure consisting of alternating layers of metal and oxide components. The coatings exhibit high oxidation resistance in the temperature range of 700-800 °C, comparable to the oxidation resistance of cast iron-aluminium alloys, and allow increasing the oxidation resistance of carbon steels by 6–20 times. The corrosion resistance of Fe-AlMg and Fe-TiAl detonation coatings in a 3% NaCl solution exceeds the corrosion resistance of uncoated carbon steel by 13.3 and 28.0 times, respectively. The obtained results allow recommending to use the developed coatings for protection of parts operating in aggressive environments at temperatures of up to 800 °C. 19 Ref., 2 Tabl., 3 Fig. [ABSTRACT FROM AUTHOR]

For the first time, the effect of B2O3 additive on the IR transmission spectra of ZrF4 and HfF4 samples and the optical properties of the coatings obtained from them was investigated. A significant difference in the shape of the absorption bands and the position of the vibration peaks of the Zirconium tetrafluoride and Hafnium tetrafluoride bonds was revealed. An assumption is made about the influence of ZrF4 polymorphism on the ratio of the vapor pressures of the specified compounds in the region of the conditional temperature of evaporation in a deep vacuum. The positive effect of the B2O3 additive on the rate of evaporation of system samples and condensation on substrates is shown. The values of the refractive indices of the coatings are about 1.53. An exception is the refractive index of the HfF4 coating (1.57), which can be attributed to the alternative (monoclinic) syngony of its crystal structure.

The analysis of the influence of the parameters of electrospark alloying with an aluminium electrode on the quality (roughness, microstructure of the coating, its continuity, phase composition, and microhardness) of the aluminized layer is presented. The effect of finishing methods after aluminizing is evaluated. The heat resistance of the obtained coatings is studied. Metallographic analysis shows that the coating consists of three sections: a ‘white’ layer, a diffusion zone, and the base metal. With an increase in the discharge energy, such quality parameters of the surface layer as thickness, microhardness of both a ‘white’ layer and a transition zone, and roughness are increased. The continuity of a ‘white’ layer at the discharge energy Wp = 0.52 J is low (of 50–60%); with a subsequent increase in the discharge energy, it increases and, at Wp = 6.8 J, it is of 100%. An increase in the discharge energy during electric-spark alloying (ESA) leads to a change in the chemical and phase compositions of the layer: at low discharge energies, a layer is formed, consisting mainly of α-Fe and aluminium oxides. As Wp increases, the layer consists of iron and aluminium intermetallic compounds, as well as free aluminium, that is confirmed by the data of local x-ray microanalysis. For practical application, it is possible to recommend the process of aluminizing by the ESA method, using the modes (discharge energy in the range of 4.6–6.8 J and productivity of 2.0–3.0 cm2/min). Such process provides the formation of a ‘white’ layer with a thickness of 70–130 µm, microhardness of 5000–7500 MPa, roughness (Ra) of 6–9 µm, and continuity of 95–100%. In order to increase the thickness of the aluminized layer, it is recommended to preliminarily apply grease containing aluminium powder to the steel surface and, without waiting for it to dry, carry out ESA with an aluminium electrode. In this case, the coating continuity is of 100%, the layer thickness is of up to 200 µm, and the microhardness is of 4500 MPa. The paper presents the results of a study of the quality parameters of multicomponent aluminium-containing coatings of Al–S, Al–C–S, and Al–C–B systems. Replacing the aluminium electrode with graphite one leads to a decrease in the thickness and continuity of a ‘white’ layer, respectively, to 50 µm and 30%. In turn, the microhardness on the surface increases to 9000 MPa. The addition of 0.7 boron to the consistency substance leads to an increase in the thickness and continuity of a ‘white’ layer, respectively, up to 60 µm and 70%. The microhardness on the surface rises to 12000 MPa. In order to reduce the roughness of the surface layer and to obtain continuous coatings, it is recommended to carry out ESA with an aluminium electrode, but at lower modes.

The influence of the crystallographic texture of Co‒Fe coatings produced by the electron beam physical vapor deposition (EB PVD) on their damping capacity (DC) has been studied. It is found that the amplitude dependence of the DC of a coating with a fiber <111> texture exhibits a prominent maximum, while that of a coating with a multicomponent <100> + <111> + <110> fiber texture shows the blurred maximum which has shifted to the higher amplitude deformations. The effect of both the fiber texture type and the level of internal (residual) stresses in the Co‒Fe coatings on the amplitude dependence of the DC has been analyzed within the framework of the Smith‒Birchak model. It is shown that the transition from a single-component to a multi-component coating texture reduces the DC maximum value. In contrast, an increase in the internal stresses in the coatings leads to a shift and blurring of the DC maximum. On this basis, it is concluded that the maximum DC for Co–Fe coatings can be achieved provided that they have a fiber <111> texture and a minimum level of internal stresses. [ABSTRACT FROM AUTHOR]

Coatings from WC–Co–Cr AMPERIT®554.074 powder were deposited using a multichamber detonation device. Investigations of coating microstructure and phase composition were conducted, using scanning electron microscopy and X-ray structural analysis. Dense coatings form at spraying by this method which consist of inclusions of tungsten carbide phases, uniformly distributed in Co–Cr matrix. Coating porosity is equal to ~0.2 %, microhardness is – 10.4 ± 1.2 GPa. Experience of application of multichamber detonation device for deposition of wear-resistant coatings from WC–Co–Cr powder is shown, both at the stage of part reconditioning and at design of components of various mechanisms. [ABSTRACT FROM AUTHOR]

The advantages of cellulose and its derivatives as the latest materials for devices that generate, store, and convert electricity are their low cost, environmental friendliness, ease of recycling and the ability to be manufactured in various ways and from various raw materials, including agricultural waste. This predetermines the relevance of their study as materials for modern technology and electronics. The research aims to determine the luminescent characteristics of composite films made based on nanocellulose and polycrystalline oxide K3Tb0.9Eu0.1(PO4)2. Optical microscopy and the spectral-luminescence method were used to characterise the films and their initial components. It was found that crystallites with an average size of about 50mm are distributed quite evenly in the film “nanocellulose+K3Tb0.9Eu0.1(PO4)2”. A Raman scattering band with a maximum of 564 nm under laser excitation at 473 nm was observed for the investigated samples in the form of suspensions. The intensity of photoluminescence of nanocellulose in suspension and films is low compared to the luminescence of oxide as a filler. The luminescence of Eu3+ ions is intense in the red region of the spectrum. The calculated values of the degree of asymmetry indicate low symmetry of the positions occupied by europium ions in the oxide and the contribution of Tb3+ ion emission to the overall spectrum of the composite film. The study results show that the luminescence of Eu3+ ions is sensitised by Tb3+ ions, which absorb the excitation light and then transfer energy to europium ions. The position of the absorption bands of Eu3+ and Tb3+ ions in the ultraviolet region of the spectrum and the intense emission of Eu3+ in the red region indicates the prospects of using nanocellulose+ K3Tb0.9Eu0.1(PO4)2 films to improve the efficiency of solar panels. Testing of the films under the excitation of luminescence by ultraviolet radiation of an LED (λex=375 nm) showed the possibility of developing white LEDs on their basis. In particular, the chromaticity coordinates of the uncoated LED were (x=0.214; y=0.079), and the use of a film composite as a coating causes a shift in the coordinates to the red region: x=0.304, y=0.196. The obtained results on the morphology and luminescent properties can be used to optimise the composition and manufacturing conditions of composite films of the following types “nanocellulose+K3Tb0.9Eu0.1(PO4)2” for use as fluorescent converters in LEDs or solar panels

The reasons for the destruction of parts of the friction units of aircraft and ground aviation equipment, which are made of iron-based alloys, were analyzed, and it was established that during operation, various processes develop on their working surfaces, namely: abrasive wear, seizure, fretting - corrosion, fatigue wear. The analysis of modern technological methods of surface strengthening of machine parts was carried out, the prospects of electrospark alloying of iron-based alloys were determined. Research on the wear resistance of coatings was carried out using a complex methodology, which includes metallographic, electron microscopic, durometric, and other methods of analysis of physical and mechanical methods. The influence of electrode materials on the wear resistance of ESD coatings has been established. Practical recommendations for surface strengthening of parts of automatic transmission systems operating under conditions of abrasive wear are indicated. [ABSTRACT FROM AUTHOR]

The paper reports on the main physicochemical properties of zinc sulfide (ZnS) and the features of its application in optics, optoelectronics, and semiconductor technology, as well as the main synthesis methods (synthesis in a solution, self-propagating high-temperature synthesis, and chemical vapor deposition). The harmful effect of the ZnO admixture on the optical and operational properties of zinc sulfide as a starting material for optical ceramics and in a thin film coating is shown. Possible ways of zinc oxide entering the base material during synthesis, storage in air or subsequent heat treatment are considered. The possibility of detecting and estimating the content of oxide admixture (ZnO) in ZnS by methods of substantial chemical analysis has been established. For the first time, approaches were proposed and implemented aimed at weakening the harmful effect of oxide admixtures by binding them with the help of lanthanide sulfides and sulfofluorides, followed by the formation of lanthanide oxosulfides by exchange reactions. The use of the addition of boron oxide (B2O3) with the formation of complex compounds with significantly lower chemical activity and volatility compared to ZnO is considered more promising. The method developed by the authors implies the complete removal of the ZnO impurity by heat treatment of the material with a sulfurizing agent, Sb2S3, the excess of which is removed by heat treatment in a vacuum. This method seems to be more labor-intensive, but more attractive for consumers of zinc sulfide as a material for interference optics. [ABSTRACT FROM AUTHOR]

In the article, as a result of comparative tests, it is established that steel samples with a coating applying the electrospark alloying method (ESA) with a ВК6 hard-alloy electrode with the use of a special technological environment (STE) with a composition of 0.5%Si + 0.5%В + 2%Cr + 7%Ni + 90% vaseline, the wear of which after 24 hours of testing is of 221 mg that is 122% less than that for samples without coating and 15% and 31% for samples with coatings applying the nichrome-electrodes' wire Х20Н80 using STE composition of 0.5%Si + 0.5%B + 59%BK6 + 40% vaseline and STE composition of 5%Si + 5%B + 90% vaseline, respectively, and by 22% and 47% less than with coatings applying the electrodes made by the method of powder metallurgy (PM), the composition of which is of 90%B^ + 10%1M and 1M, respectively. For P6M5 steel, better resistance against hydroabrasive wear is possessed by samples with a coating applying the ESA method with an electrode made of hard alloy ВК6 using STE composition of 0.5%Si + 0.5%B + 2%Cr + 7%Ni + 90% vaseline, the wear of which after 24 hours of testing is of 188 mg that is 43% less than in samples without coating and by 6% and 15% in samples with a coating applying the ESA method with an electrode made of nichrome wire of the composition Х20Н80 using STE composition of 0.5%Si + 0.5%B + + 59%ВК6 + 40% vaseline and STE composition of 5%Si + 5%B + 90% vaseline, and by 24% and 27% less than with coatings applying the electrodes produced by the PM method with a composition of 90%ВК6 + 10%1M and 1M, respectively. In ESA with electrodes-tools made both by the PM method and by the new technology of wire Х20Н80 and hard alloy ВК6 and STE, parts made of steel 45 and steel Р6M5 have a decrease in the strength limit and yield limit, respectively, and both the relative elongation and the relative narrowing increase. With further abrasive-free ultrasonic finishing (AFUF), both the strength limit and the yield strength increase, and both the relative elongation and the relative narrowing decrease. For practical implementation, wear-resistant coatings formed according to the new technology, using tool electrodes made of Х20Н80 wire and hard alloy ВК6 and STE in two stages with the following AFUF are proposed, the growth of the strength limit and the yield limit of which increase for steel 45 and steel Р6M5 by 4.9% and 4.6% and 3.5% and 2.7%, respectively, and relative elongation and relative contraction decrease by 1.7% and 1.3% and 2.0% and 1.7%, respectively. At the same time, the surface roughness is Ra = 1.1 µm, and the integrity is of 100%. [ABSTRACT FROM AUTHOR]

The article describes a new method of forming the protective coatings of steel parts operating under conditions of abrasive wear both in general mechanical engineering, the composition of which is of 90% ВК6 + 10% 1М, and in industries, where there may be radiation exposure and the composition of 1М (70% Ni, 20% Cr, 5% Si, 5% B), by applying them by the method of electro- spark alloying (ESA) with compact electrodes-tools made of nichrome wire X20Н80 and ВК6 hard alloy and using special technological media (STM), which include the necessary alloying elements. As a result of these research, it is established that the surface layers of the 45 and Р6M5 steels after applying wear-resistant coatings have a structure that consists of three areas: the 'white layer', the transition zone below, and the base metal. When the discharge energy (Wp) increases from 0.52 to 2.6 J, the thicknesses of the 'white layer' and the transition zone, their microhardness and surface roughness increase, but the integrity of the applied coating decreases. The highest mi- crohardness of 9750-12800 and 14250-14600 MPa corresponds to the coating formed on steel 45 and P6M5, respectively, during ESA by means of both the compact electrodes-tools made of hard alloy ВК6 and the STM with the composition of 0.5% Si + 0.5% B + 2% Cr + 7% Ni + 90% Vaseline. [ABSTRACT FROM AUTHOR]

The adhesion of electric-spark chromium coatings on 30ХГСA steel parts is studied. As shown, the adhesion of coatings depends on internal stresses of different nature: the difference of coefficients of thermal expansion of contact materials, mismatch of crystal lattices of the coating and substrate, generating mismatch stresses, and the presence of structural defects in the coating and substrate. [ABSTRACT FROM AUTHOR]

In the article, a direct choice system of the most rational technology for applying a babbitt coating on the liners of sliding bearings (SB) is developed, which takes into account both economic and environmental requirements. On the basis of the performed research, a physically substantiated mathematical model of the babbitt-coatings' wear process (wear equation) is proposed, which allows solving both the direct problem of determining weight and linear wears based on the known work of friction, as well as the inverse problem of finding the necessary work of friction to obtain the required amount of weight or linear wears. With knowing the time to reach a certain amount of wear, it becomes possible to operate the products more rationally, timely assigning the repair time and friction-surface catastrophic-wear preventing. In the course of research, a methodology is developed for determining the constants of the wear equation: activation energy (ЕА) as well as maximum weight (Δmб.п.н) and linear (Δhб.п.н) wears, which can be used as selection criteria for the most rational technology of applying a babbitt coating. [ABSTRACT FROM AUTHOR]

The article substantiates the importance and relevance of increasing problem of the performance and service life of babbitt sliding bearings (SB), which are the rotors supports of a large number of centrifugal pumps, compressors, turbines and other dynamic equipment operating at high operating parameters (speeds, loads and temperatures), as well as in conditions of corrosive, abrasive and other types of working environment's influence. The analysis of the babbitt SBs production technology and operating conditions showed that the reason for the decrease in their durability are factors that are formed both at the stage of manufacture and during operation. SB failure under normal operating conditions is a consequence of wear various types: cavitation, abrasive wear, damage due to plastic deformations, fatigue damage, etc. The antifriction layer wear resistance depends on the mode of operation and design of the bearing, the physical properties of the connection between the layer and the base, the rigidity of the shaft and the bed under the bearings. As established, the bearing anti-friction layer quality must be evaluated according to the following criteria: adhesion strength of the coating to the base, cohesive strength of the anti-friction layer, porosity, and homogeneity of the structure. As established, during the production of SBs, the formation by the method of electrospark alloying (ESA) of a copper intermediate layer, firmly bonded with steel substrate, and tin layer (formation of solid substitution solutions) and babbitt provides a stronger (by 35%) of adhesion, compared to traditional technology (steel 20 + babbitt), steel substrate with babbitt, as well as more intensive removal of heat from the friction zone. As determined, a new technology in which all operations are carried out by the ESA method can be a reserve for improving the babbitt coatings formation quality, which significantly affects the durability of the SB. As determined, in order to determine a more rational technology for applying babbitt coatings, it is necessary to develop a physically based mathematical model that relates the wear of a certain amount of babbitt to the frictional work spent on it. [ABSTRACT FROM AUTHOR]

As it was mentioned in the first part of this work, to determine the modulus of elasticity of one of the layers of a double-layer beam during bending, it is necessary to know the modulus of elasticity of the other layer and the bending stiffness of the entire section. Therefore, the purpose of the presented part of the work is to experimentally establish the specified characteristics of coated samples of rectangular cross-section and substrate without coating during three-point bending. The results of experimental studies of elastic-geometric characteristics during bending of samples with coatings of VT1-00 and KTC-110 alloys, applied to a substrate of VT6 alloy by microplasma sputtering, with different degrees of porosity, are presented. Analytical calculations of the modulus of elasticity of the specified coatings were carried out, the results of which make it possible to establish the general regularities of its change depending on their degree of porosity. [ABSTRACT FROM AUTHOR]

In the production of pipes made of corrosion-resistant steels on pipe rolling plants, the current problem is the low stability of the pipe tool. Therefore, the creation of high-performance and durable tools is associated primarily with the production and processing of materials that could withstand harsh working conditions. The technology of heat hardening of a pipe tool (matrix rings of complex matrices) for pressing of corrosion-resistant pipes on horizontal pipe-profile presses made of steels Х40CrMoV5-1-1 and 30WCrV17-2 is offered, which provides carrying out, after hardening with tempering of combined processing, wear-resistant single- and multilayer nanocoatings at the ‘Bulat-6’ installation of the plasma technology laboratory of NSC ‘KhIPT’. As a result of the proposed technology, strength, wear resistance, and hardness increase (the value of microhardness on the surface of the nanocoating is of 23000–25000 MPa). A wide range of studies of the structure of the base metal and coating and industrial testing of the tool are carried out. As shown, the combined treatment of matrix rings after heat hardening of the tool (ion nitriding in the plasma of two-stage vacuum-arc discharge with simultaneous application of wear-resistant coatings) increases significantly the performance of the tool and its service life, as well as its surface quality, which significantly increases the quality of the inner surface of corrosion-resistant pipes. [ABSTRACT FROM AUTHOR]

The investigation of the formation process of pseudoalloy coatings of the copper-aluminium system under the conditions of electric arc spraying is performed. Regression equations reflecting the dependence of the average particle size of the products of wire spraying, the content of oxides and porosity of the coatings on the wire feed rate, voltage at the electrodes, compressed air consumption and spraying distance are obtained using mathematical planning of the experiment. As determined, the main ways to control the size of the sprayed particles during the simultaneous spraying of copper and aluminium wires is to change the compressed air consumption and heat input into the sprayed materials and gas jet. As a result of studying the structure and phase composition of the spraying products, it is found that in the process of simultaneous spraying of copper and aluminium wires as a result of the interphase interaction of their melts pseudoalloy particles are formed, which are a conglomerate of copper-aluminium. Analysis of the study's results of coatings formation during the spraying of copper and aluminium wires show that heterogeneous pseudoalloy coatings are formed for the entire selected range of electric arc spraying parameters. The coatings consist of lamellas of the initial components of copper and aluminium with the presence of oxide layers of copper. The coatings also contain admixtures of the intermetallic phases Cu9Al4 and CuAl2, which are formed during the formation of the coating layer on the substrate. The content of oxides in the coatings is in the range of 10-17% vol., the porosity of the coatings is 4-8% vol. As a result of the performed investigation, the ways of controlling the structure and consequently the properties of pseudoalloy copper-aluminium coatings by changing the parameters of electric arc spraying are established. [ABSTRACT FROM AUTHOR]

The structure and properties of amorphizing composite detonation coatings based on FeMoNiCrB alloy were studied. FeMoNiCrB + ZrB2, FeMoNiCrB + (Ti,Cr)C, FeMoNiCrB + FeTiO3 composite powders were used for coatings deposition, which were produced from a mixture of the composition powders by mechanical alloying. It is found that as a result of detonation spraying of all the powder compositions, the formed coatings have dense, lamellar multiphase structure. The coating composition includes Fe(Ni,Cr) solid solutions, Mo2FeB2 and Fe2B borides, dispersed inclusions of alloying additives (ZrB2, (Ti,Cr)C, FeTiO3) and oxides (ZrO2 and FeCr2O4 or Fe2O3, or Fe3O4), as well as an amorphous phase, the amount of which in the coating structure has increased, as a result of the detonation spraying process. The values of microhardness, corrosion resistance, fatigue life and wear resistance of the composite detonation coatings are given. [ABSTRACT FROM AUTHOR]

Purpose. The authors propose to develop a mathematical model for the calculated determination of residual stresses in arbitrary layer of a thermal gas coating based on the change magnitude in the base geometry (sample deflection) and the variation law of the layer thickness derivative, further regulation of these stresses by changing the technological parameters of spraying for each type of sprayed coating. Methodology. Based on known works on stress detection of in welded joints, the approach of determination of samples deflection after layer-by-layer spraying was developed. These deflection parameters are the basis for the developed mathematical model of influence on the stress state. The data on the study of the main types of residual (internal) stresses, as I type, distributed in the volume of the whole part (sample) with coating, and II type, localized in the volume of sprayed particles, are systematized. Findings. We presented investigations of the residual stresses arising in the applied layer, the magnitude and nature of the distribution of which depend on the type, base and sprayed materials, methods and parameters of spraying, the rigidity of the part, and other factors. The important role of evaluating residual stresses in a thermal gas coating by the calculation method is shown in connection with the complexity of the experimental determination of the kinetics of stress development in the coating-base composite. Originality. The authors of this work, on the basis of the first created mathematical model and software product Mathcad-Prime 6 2020, conducted a study of the level and principles of the formation of residual stresses in the coating during gas-thermal layer-by-layer spraying with various material, including the possibility of using a pulsating spraying air flow. Analytical studies have shown that the attention in the literature over the past five to seven years has been paid only to the study of residual stresses and deformations in welded joints, and only the growing interest in spraying technology opens up wide possibilities for studying the formation of stress fields in a thermal gas coating. Practical relevance. The results obtained in this paper confirm the formation of residual stresses in coatings and can be used as computational programs to solve design tasks, as well as for educational purposes during experts training in engineering fields.

From the great variety of methods to improve the efficiency of cutting tools, it is necessary to highlight the methods of applying wear-resistant coatings, which in recent years are increasingly used. Applying wear-resistant coatings on the cutting tool can significantly increase its efficiency and intensify machining modes. Mechanisms of strengthening the wear-resistant coating for materials have been analyzed under the impact of technological parameters of coating condensation process on its structure parameters and mechanical properties, formation of single and multi-element coatings based on titanium nitrides, aluminum, and silicon, the transformation of coating properties by obtaining complex coatings, and principles formation of complex coatings designed for different cutting tools. The influence of the coating on the mechanical properties of high-speed steel is shown. In the magnetron sputtering coatings on P6M5 steel samples, the microhardness of the coatings is TiN – 20–24 GPa, AlN – up to 16 GPa, TiAlN – up to 35 GPa, AlTiN – up to 32 GPa, TiAlSiN – 32–37 GPa, including while the microhardness of the substrate of steel P6M5 – 6–9 GPa. The microhardness of TiAlN and TiAlSiN coatings applied on an instrumental basis is 1,5 – 1,9 times higher than the microhardness of TiN, AlN coatings. It was found that the wear intensity of P6M5 steel without coating is 6 times higher than with AlTiN, TiAlN, and TiAlSiN coating, 3 times higher than with TiN and AlN coating. The coated tool is characterized by increased reliability and higher stability and allows the processing process with higher cutting modes.

The effect of V on the formation of the structure, phase composition, and microhardness of high-eltropy AlCoNiFeCrTiVx coatings obtained by electron-beam cladding on a steel substrate in vacuum is investigated. It has been established that AlCoNiFeCrTiV0 coatings consist of two bcc solid solutions with different lattice periods and a small amount of intermetallic σ-phase. An increase in V content from x = 0 to x = 1.5 changes the phase composition of the coatings and they consist of one bcc solid solution and σ-phases of different composition. With increasing content of V, the volume fraction of the σ-phase increases. The addition of V to AlCоNiFeCrTi shows the strengthening effect of the AlCоNiFeCrTiV0-1.5 coatings and the Vickers hardness increased from 8,4 to 11 GPa.

The mechanism of formation and structure of coatings based on the system iron-aluminum, sprayed by electric arc method using wires of solid cross-section and flux-cored wire were investigated. The grain-size composition, structure and microhardness of particles (spraying products of electrode wires of iron and aluminum) captured from the spraying jet, as well as the structure, phase composition and microhardness of electric arc coatings of the system iron-aluminum were studied. It was found that during spraying of Fe + Al and Fe + AlMg wires, the interaction of particles in the jet does not occur and the products of spraying represent particles of iron and aluminum with the appropriate hardness. In this case, the formation of intermetallics in the coatings also does not occur and they have a heterogeneous structure consisting of the components based on iron and aluminum. It was found that intermetallic FeAl structure is formed only after heat treatment of sprayed coatings at 650 °C. During spraying of flux-cored wire PD(Fe–Al) in the process of melting the sheath and the filler, the interphase interaction occurs, which results in the formation of coatings with a microhardness of 2460 ± 290 MPa, the main phase of which is intermetallic Fe3 Al. [ABSTRACT FROM AUTHOR]

Studies have been performed on the modification of triacetatecellulose soluble compositions tris[three(butoxy) (polyfluoroalkoxy)titaniumoxy]boranes by the laboratories in which the length of the polyfluoroalkoxyl radical changed. At the initial stage, experiments were conducted to study the effect on the viscous characteristics of the initial solutions of TAC compositions of different temperature ranges, the values of the velocities of the concussion as for the initial base composition and with the introduction into the composition of the solution of different number of initial components, on the basis of which the target additives are synthesized, namely, polyfluoropic alcohol or tris[three(butoxy)titanoxy] borane. When introduced into the basic soluble composition of small amounts of polyfluorine alcohol FFА-3 (up to 0,1 % of the mass. from the mass of TAC) and a shear rate of 0,99c-1 there is a sharp increase in viscosity to 1,56 P·s, that is connected, apparently, with the implementation of a new type of hydrogen bonds between electronegative fluorine atoms and positively charged carbon atoms in the structure of solvents and TAC links (in complexes, simple ethers, glycosidic bonds and methylene groups at free hydroxylates). The implementation of such connections is accompanied by an increase in the volume of assocites, which are formed, ie indicates an increase in the viscosity of the solution of the sample TAC - composition. This interaction, with the formation of associations, takes place, first of all, on the surface of small supramolecular formations of TAC, obtained in the previous initial crushing of large supramolecular groups in solution. In this case, in the basic solution of the TAC-composition, there is a process of reversal of the TAC, namely, consolidation of the sizes of supramolecular formations. It is shown that the studied series of bor-, titanium-, (butoxy(polyfluoroalkoxy)-containing products, are effective modifiers of triacetate-cellulose soluble composite materials, allowing at the outflow stage, such as film materials or artificial silk threads, to adjust in a wide range, in the direction of increase, viscosity of the solution and at the same time increase the strength of finished products to break. The achievement of the obtained positive effect is due to the implementation in the polymer matrix of a new type of physical interactions between the electronegative fluorine atoms in the additive and the electropositive carbon atoms of the TAC molecule, as well as the coordination bonds between B and Ti additives and oxygen links TAC polymer. At the same time, internal stresses in the polymer matrix are reduced or virtually disappeared. Thus, studies have shown that polyfluoropic alcohols, tris- [three (butoxy)titanoxy]borane and products of its transesterification by polyfluoropic alcohols of different molecular weight are effective modifiers of soluble TAC compositions (as regulators of viscosity of solutions at the stage of outflow of films), and additives that increase the relative strength of their films by 2-3 times the strength of the films to break; their relative hardness), it is most advisable to use such a number of compounds in quantities of up to 1,0 % of the mass. from the mass of TAC. The obtained results can be used to significantly improve the quality of products from triacetatecellulose or in the recycling of products and waste on its basis. [ABSTRACT FROM AUTHOR]

An investigation was conducted on the effect of sodium chloride concentration on corrosion inhibition efficiency of High-Density Polyethylene (HDP) coating on alloy steel in sodium chloride solutions of different degrees of salinity. In the study, four test media were used: the first is 20 l of distilled water in a rectangular base plastic container; the second is 20 l of distilled water in a rectangular base plastic container in which 200 g of sodium chloride (NaCl) was dissolved entirely, giving a concentration of 10 g/l (0.01 g/cm²). Similarly, the third medium is 20litres of distilled water in which 300 g of NaCl was dissolved entirely, having 15 g/l (0.015 g/cm²) concentration. The fourth medium is prepared by dissolving 400 g of NaCl in 20litres of distilled water, resulting in 20 g/l (0.02 g/cm²) concentration. The container used for each medium is a rectangular base plastic container. Twenty-eight (28) uncoated and twenty-eight (28) polyethylene-coated alloy steel coupons of dimension 5×30×50 mm with an 8 mm diameter hole each were used for this investigation. Seven coated coupons each were wholly immersed in 10, 15, and 20 g/l, and zero salinity distilled water. Similarly, seven uncoated coupons each were immersed entirely in 10, 15, and 20 g/l and zero salinity distilled water. The coupons in various test media were exposed to ambient temperature for a total of 49 days. One coupon from each of the media is reweighed on weekly bases and the weight loss (g), corrosion rate (mm/year), and corrosion inhibition efficiency were calculated and recorded. From the results obtained, the corrosion rate of the coupons increases with an increase in sodium chloride solution. It is also observed from the results obtained considering the variation of corrosion rates of polyethylene coated coupons with sodium chloride concentration and the variation of corrosion rates of uncoated coupons with sodium chloride concentration that the corrosion rate of the coupons is lesser with the polyethylene coating compared with the uncoated coupons. The results show that the corrosion rate of coupons falls over time, and more rapidly at an early time of exposure, say the first week. From the result of the variation of corrosion inhibition efficiencies of polyethylene coated coupons with sodium chloride concentration, it is observed that the corrosion inhibition efficiency of polyethylene decreases over time and decrease also with an increase in sodium chloride concentration.

It was established that the technology of electrospark alloying is a promising method of strengthening and restoration of parts and such technological and power equipment as shafts of pumps and electric motors, impellers, pump housings, centrifuges, etc. To increase the efficiency of the proposed technology, a number of electrode materials like FeNiSi – Cr3C5, WC – TiC – Mo2C – Co – Cr and WC – TiC – Co – Cr – Ni – Al, TiC– (Fe – Cr – Si – Al), NiCrBCuC – WC, FeNiCrBSiC – TiB2 and FeNiCrBSiC – CrB2 were created, which were tested at industrial enterprises of Ukraine. It was revealed that application of the developed electrodes provides a simultaneous increase in the manufacturability of the process of electrospark alloying with an increase in the life of parts of technological equipment by 2.0…2.5 times. 10 Ref., 4 Fig. [ABSTRACT FROM AUTHOR]

The results of investigations of the structure and phase composition of gas-thermal coatings based on Fe–Al intermetallics are presented. Fe-Al intermetallics were chosen as a material of protective coatings due to their high heat and corrosion resistance and cost effectiveness as compared to many modern heat resistant materials. As spraying materials, powders of mechanical mixtures of Fe and Al as well as powders produced by mechanochemical synthesis of Fe–Al intermetallics by the treatment of mixtures of powders Fe and Al in a high-energy ball mill were used. The content of powder components corresponds to the intermetallics Fe3Al, FeAl and Fe2Al5. For spraying, the alloyed powders were used having the composition corresponding to the intermetallic Fe3Al. To increase the mechanical and physicochemical properties of the intermetallic, as alloying elements Ti, Mg, Cr, Zr, and La were used. The coating was produced by plasma and supersonic air-gas plasma spraying. It was found that in plasma coatings with FeAl powders, in addition to the initial phase (Fe3Al, FeAl and Fe2Al5), Fe and Al oxides are also present, due to which the microhardness of the coatings increases by about 1300 MPa relative to the initial powders. The microhardness of the plasma coating of the alloying powder Fe–TiAl 2 times increases relative to the initial powder due to the formation of the intermetallic phase FeTi in the coating. During spraying of mechanical mixtures, due to a low probability of contact interaction of Fe and Al particles during flight and rapid cooling of melts particles on the surface of the base, the synthesis of intermetallics does not have a time to develop and in the coatings no intermetallic phases are revealed. In the coatings produced by supersonic air-gas plasma spraying, the main phase is α-Fe(Al)-solid solution, which is the result of a high rate of melt hardening. [ABSTRACT FROM AUTHOR]

A review of modern technologies for the deposition of protective wear-resistant coatings for tribotechnical purposes has being conducted. It is established that titanium carbide is widely used to strengthen surfaces as a component of such coatings. We can achieve not only an increase in wear resistance, but also to realize the effect of self-healing of the friction surface. This material is promising for the creation of metal-based composites for high temperature applications. Thus, the tribotechnical properties of the new alloy of the Co-TiC system of tribotechnical purpose are established. Sintered composite alloys based on cobalt matrix (Co alloyed with iron, aluminum and chromium) were made. Titanium carbide was used as a highmodulus strengthening phase. The TiC content was in the range of 30-50 vol. % Porosity was changing in a range of 3.1% to 28%. The melting point of alloys exceeds 1320 °C, and they can undergo all kinds of technological procedures together with the turbine blades, including soldering and degassing, without damage, changes in structure. The research of thermal and structural stability of alloys by methods of differential thermal analysis were carried out. Alloys do not have additional thermal effect, which confirms their structural stability. The study of their microstructure revealed three types of components - TiC particles, matrix solid solution (cobalt-based alloy) and pores - structural defects that have a negative impact on all studied properties. The influence of porosity on the properties of alloys is investigated. It was found that increasing the porosity from 3 to 28 percent reduces the heat resistance by 3 times, while the wear resistance at a temperature of 650 ° C is reduced twice. It is proved that an alloy based on cobalt with 50% vol. TiC and porosity 3.1% is prospective for the material application to the top shrouds of the blades of the gas turbine engine. [ABSTRACT FROM AUTHOR]

Purpose. The article is aimed to investigate the structure of the composite coating obtained by pulse-plasma treatment using cathodes of high-carbon material with higher amount of carbide-forming elements. Methodology. The coating was produced using electrothermal axial plasma accelerator with the following operating parameters: voltage applied to the electrodes is 4.0 kV; amplitude of the current is 18 kA; distance between electrodes of about 50 mm. The treatment was carried out according to the scheme: five pulses with electrode of steel T1 + five pulses with electrode of cast iron Cr28Mn3. The pulsed plasma treatment was followed by heat treatment as holding at 950 °C for 2 hours, followed by oil cooling. Optical (Nikon Eclipse L150) and electron (JEOL JSM-6510) microscopy, energy dispersive spectroscopy (X-Act, Oxford Instruments), the microhardness measurement (FM-300 Future-Tech Corp.) were used for microstructure studying. Findings. It is shown that pulsed-plasma treatment using various electrodes resulted in formation of laminated coating «P18 steel/cast iron 230Cr28Mn3» of 110-130 microns thick. The analysis of micro-hardness coating before and after the post-plasma heat treatment is carried out. It is found that quenching resulted in increase of coating microhardness from 4900-7300 МPа tо 10500-13500 МPа (layer “T1”) and 12000-16500 МPа (layer “230Cr28Mn3”). Originality. The distribution of the alloying elements within the coating is studied. The diffusion transition layer having variable tungsten and chromium content was revealed between the layer “T1” and layer “230Cr28Mn3”. It was shown that after plasma deposition an oversaturated solid solution is being formed in the coating. During post-heat treatment it decomposes with the precipitation of 45-70 % carbides of different shape resulting in sharp increase of microhardness. Carbides amount is proportional to content of carbon and carbide-forming elements in the electrode used for certain layer deposition. Practical value. It was shown the possibility of the formation of a composite layered pulsed-plasma coating with variable chemical composition and micro-hardness in cross-section by means of varying the cathode material and by use of post-plasma heat treatment.

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article reflects the results of research on influence of a number of fillers on weight loss of wood protected with a coating based on inorganic and organic substances in the process of thermal impact. A specific feature was the research of fire retardant efficiency of a coating composition. The solution to this problem was searched for by the standardized methods. The influence of the fillers under conditions of a high-temperature heat flux on the dynamics of weight loss of wood treated with fire retardants was revealed, and the mechanism of the kinetics of the influence of the filler was determined. The latter is characterized by lowering rate and weight loss. Inter alia, for a sample of wood with fire retardant coating containing high-temperature filler a gradual temperature decrease occurs, i.e., the functioning of the coating was noted, and hence, the lowering of smoke formation ability was revealed. To determine the fire retardant efficiency when using high-temperature fillers of coating, the combustibility groups of wood were established by loss of weight and increase of smoke fumes temperature. It was revealed that the treated wood has become a hardly combustible material. The loss of weight of coatings versus temperature was determined as a result of the thermogravimetric analysis. Based on the named analysis, the activation energy was studied under conditions of thermal decomposition of the coatings. It was found that the latter was equal to 21.87 kJ/mole for the coating based on organic and inorganic substances, but in case of introduction of high-temperature substances, it increased three times. This fact makes it possible to draw a conclusion on the expedience of application of fillers based on high-temperature substances for raising the efficiency of coatings based on organic and inorganic substances. [ABSTRACT FROM AUTHOR]

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of this investigation was obtaining of biocompatible coatings for medical implants based on biopolymer chitosan and hydroxyapatite, which is the main mineral component of bone tissue. Coatings were obtained by thermal substrate method, because it allows low temperature deposition and provides possibility to incorporate into coating structure biomolecules, unstable at high temperatures. As a way of chitosan incorporation into coating composition co-precipitation method was proposed. It allows obtaining uniform coatings with required composition and morphology. The obtained coatings were investigated by using of XRD, SEM with EDS, adhesion was tested by test-tape method. It was assigned that chitosan addition decreased hydroxyapatite crystallinity, so the range of concentrations from 0.01 to 0.1 g/L was chosen at pH = 6.5. It was determined that variation of chitosan concentrations in the initial solution influenced on morphology and structure of hydroxyapatite coatings as well as on the antibacterial properties and the use in orthopedics and dentistry. The best characteristics were obtained for hydroxyapatite-chitosan coatings deposited from solution with chitosan concentration 0.025 g/L.

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Machinery & Energetics is the property of National University of Life & Environmental Sciences of Ukraine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The role of certification tests in the assessment of the compliance of friction units of aviation and space technology is shown. Brief explanations are given on the explanation of the quality of triboelements and their controlled characteristics. On an example of evaluating the quality of coatings of friction units, the possibility of constructing a mathematical model for taking into account the corresponding groups of coating properties as components of quality indicators is shown. Analysis of types of quality control of friction surfaces, in particular their coatings, allows you to determine the specific significance and consumer properties of the monitored indicators. The methodical supply of the types of evaluation of the quality of the friction units is determined. Analytical dependencies that define the boundaries of the practical use of the constructed model, the estimation of the generalized quality index are presented. Identification of factors that affect the provision of established quality indicators and the establishment of ways to target these factors will reduce and optimize research on improving the quality of friction surfaces. [ABSTRACT FROM AUTHOR]

Copyright of Naukovi visti NTUU - KPI is the property of National Technical University of Ukraine KPI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The complex approach to estimation of efficiency of application of intumescent coating for wood, the peculiarity of which is investigation of flame retardant efficiency of a covering, installation of firehazardous properties and research of operational characteristics, is offered. The solution of this problem is carried out according to standard methods. It is revealed that for rough wood there is a rapid process of combustion of material and the release of a significant amount of heat, for fire-proof wood the temperature is lower than the temperature of ignition of wood. In order to establish fire protection efficiency in the application of coatings, studies have been carried out on determining the group of wood burning in terms of mass loss and increase in temperature of flue gases, and it was established that when the coating is treated, the wood passes into a group of heavy materials. Experimental studies have established that after placing a sample of wood in the test chamber, its ignition begins with the release of a significant temperature and the spread of the flame on the surface; instead, for a sample of fire-retarded wood there is a gradual decrease in temperature, that is, the work of the coating is fixed, and accordingly, the decrease in the smokeforming ability of the wood is flame retardant coating. It has been established that as a result of surface treatment with intuessent coating, products lose the ability to moisten and absorb water, which provides them with resistance to atmospheric factors and reduces the permeability of corrosion-resistant corrosion resistant sponge components several times. [ABSTRACT FROM AUTHOR]

Copyright of Naukovi visti NTUU - KPI is the property of National Technical University of Ukraine KPI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Nano- & Electronic Physics is the property of Sumy State University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)