Electrospark Alloying Research Articles

The Characterization of Soft Antifriction Coating on the Tin Bronze by Electro-spark Alloying

Soft materials such as silver, copper and Babbitt SnSb11Cu6 were deposited on the surface of tin bronze by electro spark alloying (ESA) to form the antifriction coating. The data of the antifriction coating were tested by electronic balance, three-dimensional optical profilometer, scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffractometer (XRD), Vickers microhardness tester and tribometer. The mass gain, roughness, thickness, surface morphology and phase composition, cross-section and element distribution, microhardness and tribological properties of the antifriction coating were analyzed. The results show that the grain size of the antifriction coating is fine and the metallurgical bonding between the coating and the substrate is good. The surface of each substrate is composed of three layers of coating. The optimal parameters of electro spark alloying are as follows: the discharge voltages of Ag, Cu and Babbitt alloy coatings are 60 V, 60 V and 30 V respectively, the energy storage capacitance is 150 μF, 150 μF and 90 μF respectively, and the working efficiency is 3 min/cm2, 3 min/cm2 and 4 min/cm2 respectively. Under the optimized parameters, the average mass transfer efficiency is 54.4 mg/cm2, the average surface roughness is 32.3 μm, and the maximum thickness is about 160 μm. The surface friction coefficient of the soft antifriction coating is 55.6 % of that of the tin bronze substrate. The main wear mechanisms of the soft antifriction coating prepared by electro spark alloying technique are plastic deformation accompanied by slight polishing.

Interrelation between the Composition of Steel Treated by Electrospark Alloying and the Properties of Resulting Composite Surface

Interrelation between the Composition of Steel Treated by Electrospark Alloying and the Properties of Resulting Composite Surface

STRUCTURE, MECHANICAL AND TRIBOLOGICAL PROPERTIES OF TI-CR-C-NI-FE COMPOSITE COATINGS

Here we discuss the use of composite cermet SHS electrodes from materials based on titanium carbide, chromium carbide, and nichrome obtained by SHS extrusion for the electrospark deposition of Ti-Cr-C-Ni-Fe composite coatings on metal substrates made of high-speed steel R6M5. Four electrospark alloying modes are considered which correspond to electric discharge energies of 0.2, 0.3, 0.6, and 1.0 J. The plotted experimental curves of the total anode erosion and the total cathode weight gain on the alloying time have a classical form. The effect of the electrospark alloying modes on the structure, mechanical (hardness) and tribological properties of the obtained composite coatings is studied. It is shown that the coating consists mainly of a matrix based on two Cr-Ni-Fe-Csolid and Fe0.7Ni0.3 phases and reinforcement complex carbide Ti0.8Cr0.2C particles, the size of which decreases to less than 100 nm with proximity to the substrate. The hardness of the resulting composite coatings is 10.6-13.5 GPa. The major fraction of carbide particles in the SHS electrode melts during electrospark alloying, and with increasing discharge energy the number of transferred grains in the solid phase increases by a factor of up to 9. Depending on the discharge energy of electrospark alloying, we determine the transfer coefficients of the SHS electrode, the run-in areas of the resulting coatings, and the amount of wear of the coating and counterbody.

Production of electrodes by spark plasma sintering method of secondary powder materials

The article considers the practical possibility of manufacturing electrodes from secondary powder materials. Obtaining electrodes with desired properties suitable for electrospark alloying processes. Bronze powder obtained from waste metal scrap by electroerosive dispersion was used. The following equipment was also used: spark plasma sintering system SPS 10-3 from Thermal Technology, drying cabinet ShS-80-01 SPU, set of sieves according to GOST 2715—75, analytical balance Acculab ALC-210d4, XRD-6000 Shimadzu diffractometer, X-ray fluorescence spectrometer Niton XL3t 900 GOLDD+. Secondary bronze fine powder was subjected to pressure sintering in an SPS 10-3 spark plasma sintering system from Thermal Technology. The maximum temperature was 910 °C, pressure — 40 MPa. Materials before and after were examined for elemental composition. The resulting briquette was cut into electrodes, and test surfacing was carried out by the method of electrospark alloying. Using spark plasma sintering, it is possible to obtain electrodes from secondary bronze powder materials suitable for electrospark alloying processes.

Study of combined method of electric spark alloying and ultrasonic burnishing

Article describe opportunity to increase effectiveness electro spark alloying (ESA) by means to create combined methods (ESA and ultra supersonic smoothing USS). Dates of metallographic researches, roughness surface measurements, wear resistance tests, tests of cyclic alternating characters, full — scale tests. Finally paper introduce optimal interval of technological parameters of ESA and USS.

Mass Spectrometric Study of the Chemical Composition of the Gas Environment in the Zone of Electrospark Alloying

Mass Spectrometric Study of the Chemical Composition of the Gas Environment in the Zone of Electrospark Alloying

Властивості поверхонь деталів із криці 12Х18Н10Т, які працюють в умовах радіяційного опромінювання, відновлених методою електроіскрового леґування. Ч. 2. Особливості структурного стану, відновлених поверхонь

Властивості поверхонь деталів із криці 12Х18Н10Т, які працюють в умовах радіяційного опромінювання, відновлених методою електроіскрового леґування. Ч. 2. Особливості структурного стану, відновлених поверхонь

Mathematical model of the heat distribution process in a steel part during surface modification by the electro-spark alloying method

Problem. Electro-spark alloying (ESA) is a promising process of surface modification, which allows obtaining a high-quality coating, is environmentally safe and energy efficient. Wide application in production is hindered by the need to develop the technology, as well as the lack of a mathematical model for predicting the properties of coatings depending on materials and processing modes. It is known that the high adhesive bond of the coatings obtained by the ESA method with the base is explained both by the intensive mixing of the electrode materials in the liquid phase and by the diffusion of the anode material into the cathode in the solid phase. The goal is to develop the mathematical model that allows describing the process of heat propagation in the coating during electro-spark alloying of the metal surface. Methology. The direction of technological thermal physics of N.M. Rykalin is widely known, it is based on the theory of thermal conductivity of the method of heat sources. Regarding the thermal conductivity of solid bodies, the most universal Green's function is the Kelvin solution - the fundamental solution of the heat conduction equation, which describes the temperature distribution in an unbounded solid body, which occurs after the release of a finite amount of heat in the form of an instantaneous point source. The mathematical model of the process of heat propagation in the product during ESA was described using the Laplace operator. It is taken into account that the temperature of the surface of the strengthened part depends on the thermophysical characteristics of the anode and cathode, the diameter of the electrode, as well as the speed of movement of the alloying electrode. Results. The original mathematical model that allows describing the process of heat propagation in the coating during electro-spark alloying of the metal surface is developed. It is shown that the larger the diameter of the electrode, the higher the temperature at the coating-base interface, and therefore the better the adhesion of the coating. The optimal speed of moving the electrode is 0.5-1.5 m/s. Practical value. To obtain the best adhesion of the coating to the base, it is necessary to use an electrode with the largest diameter of 4.5 mm in combination with a low speed of moving the electrode.

INCREASING THE DURABILITY OF CENTRIFUGAL PUMP SHAFTS BY COMBINED METHODS

The article analyzes the literature, which showed that in recent years there have been new technological methods of strengthening the surface layers of the centrifugal pumps shafts necks. They are based on the use of environmentally friendly method of electrospark alloying (ESA) (cementation, application of combined coatings with molybdenum disulfide (MoS2), coatings of Al-C-B) and without comparative tests for wear resistance is difficult to prefer one method or another. Studies on the friction machine СМЦ -2 found that the weight wear of round specimens of polished steel 40X, in contact with lubrication of turbine oil T-22 with babbitt inserts of the sliding bearing according to the scheme "disk-insert", 1.15 times greater than steel 30X13 and, respectively, 2.50 and 4.41 times than 40X steel after cementation by ESA (CESA) + non-abrasive ultrasonic finishing (NAUF) and ESA (Mo + S) + NAUF. In turn, the linear wear of polished steel 40X round samples is greater than steel 30X13 1.09 times and, respectively, 2.83 and 5.85 times than steel 40X after CESA + NAUF and ESA (Mo + S) + NAUF. The lowest coefficient of friction was recognized as 0.025 and 0.030, which belongs to the coating of MoS2, formed, respectively, on samples of steel 30X13 and 40X and treated with NAUF.
 Analysis of the linear wear change nature of steel 40X and 30X13 round samples, both hardened and not hardened, showed that all samples first have more intense wear, which after 2 hours of abrasion slows down, becomes more stable and at first glance resembles exponential dependence. Samples reinforced in the sequence ESA (Mo + S) + NAUF have the best wear resistance, the wear of which after 8 h of tests is 0.9 and 1.1 μm, respectively, of steel 30X13 and 40X.
 Weight and linear wear of 40X steel specimens without hardening is higher compared to non-reinforced 30X13 steel specimens tested in pair with BK8 counterbody under conditions of abundant lubrication with I40A industrial oil, by 21.7 and 14.2%, respectively; in comparison with samples of 40X steel with a coating applied by the method of ESA composition (Al-C-B) followed by NAUF, respectively, 77.8 and 84.7%; and 30X13 steel with similar treatment of ESA (Al-C-B) + NAUF, 98.0 and 71.8%, respectively.

Technological Features for Controlling Steel Part Quality Parameters by the Method of Electrospark Alloying Using Carburezer Containing Nitrogen-Carbon Components.

A new method of surface modification based on the method of electrospark alloying (ESA) using carburizer containing nitrogen—carbon components for producing coatings is considered. New processes have been proposed that include the step of applying saturating media in the form of paste-like nitrogenous and nitrogenous-carbon components, respectively, onto the surface without waiting for those media to dry, conducting the ESA process with the use of a steel electrode-tool, as well as with a graphite electrode-tool. Before applying the saturating media, an aluminium layer is applied onto the surface with the use of the ESA method at a discharge energy of Wp = 0.13–6.80 J. A saturating medium in the form of a paste was applied to the surfaces of specimens of steel C22 and steel C40. During nitriding, nitrocarburizing and carburization by ESA (CESA) processes, with an increase in the discharge energy (Wp), the thickness, micro hardness and continuity of the “white layer” coatings, as well as the magnitude of the surface roughness, increase due to saturation of the steel surface with nitrogen and/or carbon, high cooling rates, formation of non-equilibrium structures, formation of special phases, etc. In the course of nitriding, nitrocarburizing and CESA processing of steels C22 and C40, preliminary processing with the use of the ESA method by aluminum increases the thickness, microhardness and continuity of the “white layer”, while the roughness changes insignificantly. Analysis of the phase composition indicates that the presence of the aluminum sublayer leads to the formation of the aluminum-containing phases, resulting in a significant increase in the hardness and, in addition, in an increase in the thickness and quality of the surface layers. The proposed methods can be used to strengthen the surface layers of the critical parts and their elements for compressor and pumping equipment.

PHYSICAL AND MECHANICAL CHARACTERISTICS OF ADDITIVE COATINGS

The article presents the results of a study of the physical and mechanical characteristics of additive coatings obtained by a combination of methods of electrophysical surfacing and electrospark alloying. The issues of structural transformations during the creation of coatings by the method of additive technologies are considered. It has been established that the chemical composition of the electrodes used has a fundamental influence on the strength and tribotechnical characteristics of the coatings. The formation of both superhard phases in the resulting hybrid coatings and phases with a layered structure characterized by high tribotechnical characteristics is observed. The composition of the coatings, the technological modes of their production have a significant impact on the values of the specific surface energy. When using the proposed technology for obtaining coatings, it is possible to form nanostructures in the matrix of additive coatings. The use of this technological method can significantly improve the physical and mechanical characteristics of superhard coatings.

Research of the regularities of the processes of formation of the surface layer in electric spark alloying

Purpose. Determination of rational parameters of the process of electrospark alloying of 40X steel parts with different types of electrodes. Measurement of the applied layer thickness using the Mora Primus 564 coordinate measuring machine at the customer's plant. To give recommendations on the use of electrospark alloying processing modes in the production process when restoring parts. Research methods are based on effective methods of treatment of metal surfaces and technology of obtaining modified layers by electrospark treatment. Measurements were based on theoretical metrology in modeling instrumental errors of measuring instruments, theoretical principles of instrumentation and mechanical engineering technology. The Mora Primus 564 coordinate measuring machine was used during the measurements. Research results. Electrospark alloying is one of the most common technologies for working with metal, which is characterized by high accuracy and productivity. In addition, high adhesion strength of the applied layer with the base material is provided, and the process itself is easy to perform technological operations and has low energy consumption. The analysis of the main factors influencing the quality of the surface layer during processing is carried out. The process of electrospark alloying of a 40X steel sample was investigated experimentally. During the experiments, modern control and measuring equipment and measurement methods were used. Scientific novelty. For the first time, rational modes of electrospark alloying with vanadium, titanium and tungsten of 40X steel parts have been determined. The dependence of the thickness of the applied layer on the modes of treatment with different electrode material is established. Recommendations for alloying modes in the production process for 40X steel are given. Practical meaning. The experimental researches on electrospark alloying of the 40X steel sample carried out in the production conditions allowed to reveal the basic regularities of the formation of the surface layer and to formulate recommendations for obtaining a coating of a certain thickness. This will restore the worn surface of the part or strengthen the new one.

ПОЛУЧЕНИЕ МЕТАЛЛОМАТРИЧНЫХ СПЛАВОВ ДЛЯ ИЗНОСОСТОЙКИХ ЭЛЕКТРОИСКРОВЫХ ПОКРЫТИЙ

The study objective is to obtain and study metal matrix alloys based on NiAl intermetallic compound with different concentrations of Ni for forming wear-resistant coatings on steel 45. 
 The problems to which the paper is devoted are: obtaining electrode materials based on NiAl intermetallic compound with different concentrations of Ni and studying their structure; studying the mass transfer during electrospark deposition on steel 45; studying the comparative wear resistance of the coatings obtained. 
 Research methods: electrode alloys are obtained by the method of liquid-phase self-propagating high-temperature synthesis; electro spark alloying is used to create wear-resistant coatings; the microstructure of the obtained alloys is studied by the method of metallographic analysis.
 The novelty of the work: for the first time, the influence of different Ni concentration values on the wear resistance of NiAl electrospark coatings on steel 45 is studied.
 Study results: the microstructure of the obtained alloys consists of doped Cr and Co grains of NiAl matrix with a different Ni/Al ratio, along the boundaries of which the compounds of all alloy components are located. When forming coatings by electrospark method, time dependences of changes in anode erosion, cathode gain and mass transfer coefficient are obtained. 
 Conclusions: NiAl metal-based alloys with different concentrations of Ni were smelted using a liquid-phase SHS method using charge consisting of metal oxides and mineral concentrates containing tungsten and zirconium; the microstructure of the obtained alloys consists of doped Cr and Co grains baseds on NiAl, along which boundaries compounds of all the constituent components of the alloy are concentrated, including Zr and W. Experimental results of anode erosion, cathode gain, and mass transfer coefficient were obtained while forming the coatings with the alloys using electrospark method, and it was found during wear resistance tests that with an increase of Ni concentration in the alloy, the wear resistance increases.

Electric-Spark Alloying of Metal Surfaces with Graphite

The article reviews and analyses the current scientific research in the field of surface treatment of metal surfaces with concentrated energy fluxes (CEF) — the electric-spark (in the literature, known also as electrospark) alloying (ESA), which makes it possible to obtain surface structures with unique physical, mechanical and tribological properties at the nanoscale. The ESA method with a graphite electrode (electrospark carburizing — EC) is based on the process of diffusion (saturation of the surface layer of a part with carbon), and it is not accompanied by an increase in the size of the part. In this article, the influence of the EC parameters on the quality of the carburized layer is investigated. The microstructural analysis shows that the three characteristic zones could be distinguished in the structure: the carburized (‘white’) layer, the finely dispersed transition zone with fine grain, and the base metal zone. The analysis of the results of the durometric studies of the coatings is carried out. To achieve the required parameters of dimensional accuracy and roughness of the working surface of the part after the EC process, it is necessary to use the method of non-abrasive ultrasonic finishing (NAUF). In addition, because of applying the NAUF method, the surface roughness is decreased, the tensile stresses are changed to the compressive ones, and the fatigue strength is increased too. In addition, to reduce the roughness of the treated surface, it is proposed to apply the EC technology in stages, reducing the energy of the spark discharge at each subsequent stage. In order to increase the quality of the carburized layer obtained by the EC process, it is proposed to use a graphite powder, which is applied to the treated surface before alloying. The comparative analysis shows that, after the traditional EC process at Wp = 4.6 J, the surface roughness of steel 20 is Ra = 8.3–9.0 μm, and after the proposed technology, Ra = 3.2–4.8 μm. In this case, the continuity of the alloyed layer increases up to 100%; there increases the depth of the diffusion zone of carbon up to 80 μm as well as the microhardness of the ‘white’ layer and its thickness, which increase up to 9932 MPa and up to 230 μm, respectively. The local micro-x-ray spectral analysis of the obtained coatings shows that, at the EC process carried out in a traditional way, the applying Wp = 0.9, 2.6, 4.6 J provides the formation of the surface layers with high-carbon content depths of 70, 100, 120 μm, respectively, and with the use of a graphite powder, they are of 80, 120, 170 μm. While deepening, the amount of carbon is decreasing from 0.72–0.86% to the carbon content in the base metal — 0.17–0.24%. In the near-surface layer formed with the use of the new technology, the pores are filled with free graphite, which could be used as a solid lubricant to improve the operating characteristics of the friction-pairs parts processed thereby.

On the Issue of Combining Electrospark and Thermodiffusion Methods for Hardening the Machine Parts Surfaces in the Agribusiness

The processes of obtaining wear-resistant coatings during electrospark alloying of steel 40 followed by high-frequency boronizing under a charge layer based on boron carbide with aluminide additives are considered. The thickness of the coatings reaches 600-1000 microns, the surfacing time is 1-2 minutes. The results of metallographic studies are presented, as well as tests for enduring quality under abrasive wear conditions of specimens made of steel 40 with and without hardening coatings.

Improving tribological properties of TC4 strengthened by tungsten using ESA

ABSTRACT In this paper, TC4 titanium alloy surfaces were strengthened by electro-spark alloying (ESA) with the tungsten rod as an electrode to investigate the effects of voltage and pulse frequency on tribological properties of tungsten-strengthened layers. It was shown that the surface morphology of strengthened TC4 possesses a main tungsten phase with a typical characteristic of sputtering. The maximum average thickness and microhardness of strengthened layers had been achieved at 50 μm and 21.6 GPa, respectively. The latter had been found to be 6–7 folds higher as opposed to that of TC4. In the friction tests conducted, the friction coefficient and wear loss of strengthened layers appeared to be reduced by approximately 76.2% from 0.45 to0.11, as well as 89.47% from 3.8 to 0.4 mg accordingly. Overall, this study offers an effective preparation method of wear-resistant tungsten-strengthened layers with the resulting low friction coefficient on TC4 surfaces via ESA.

Interrelation of the Composition of Steel Treated by Electrospark Alloying and the Properties of Obtained Composite Surface

Basing on the study of the elemental composition of surface composites obtained on 45, 65G, and St3 steels by electrospark alloying using processing electrode from T15K6, VK8 hard alloys, as well as 45 and St3 steels (the “steel on steel” option), it was shown that the resulting surface layers are ~70% composed of the material steel substrate modified by electro-discharge treatment. The influence of the steel composition on the coefficients of the processing electrode material transfer on the substrate, on the roughness, microhardness, and wear resistance of the resulting surfaces has been studied. It is shown that the wear resistance of the resulting composites is determined mainly by the nature of the treated surface and, to a much lesser extent, by the processing electrode material, roughness, and microhardness of the surface.

ДОСЛІДЖЕННЯ ТОЧНОСТІ ОТВОРІВ У ВОЛОКНИСТИХ ПОЛІМЕРНИХ КОМПОЗИЦІЙНИХ МАТЕРІАЛАХ ПРИ ОБРОБЦІ СВЕРДЛАМИ З ДИСКРЕТНИМИ ПОКРИТТЯМИ ГЛОБУЛЯРНОГО ТИПУНА РОБОЧІЙ ПОВЕРХНІ

The article considers the main brands of tool materials used for cutting tools used for processing fibrous polymer com-posite materials (FIC) and sets requirements for them. The analysis of advantages and disadvantages of their application is carried out. It is noted that to increase the wear re-sistance of cutting tools made of high-speed steels and carbide alloys for processing fibrous polymeric composite materials are currently used continuous coatings based on TiC, TiN, TiCN, TiALON, AlCrN and others, however, the use of such coatings does not significantly increase resistance due to the impossibility of providing in the process of cutting a small radius of rounding of the cutting edge. It is shown that diamond coatings are predominant for the processing of fibrous polymeric composite materials, but there is a problem of creating the necessary adhesion and high cost of the tool with this coating. Competitive and promising method of applying wear-resistant coatings is the method of electrospark alloying (ESA), which in comparison with other methods has both a significantly lower magnitude of energy consumption and a cost of equipment. The article presents the results of re-search to determine the accuracy of holes in parts made of fibrous polymeric composite materials, namely fiberglass STEF-U when processing drills from high-speed steel with the discrete covering of globular type put on its working surfaces in comparison with drills with a diamond covering. The obtained research results showed that the obtained values of deviation from the roundness of machined holes meet the requirements for holes for fasteners, and this indicates the possibility of equivalent replacementof drills with polycrystalline diamond coating on drills made of high-speed steel type, which will reduce the cost of the tool and therefore the cost of the finished product without losing the accuracy of processing.

Complex study of protective Cr3C2–NiAl coatings deposited by vacuum electro-spark alloying, pulsed cathodic arc evaporation, magnetron sputtering, and hybrid technology

Coatings were obtained by vacuum electro-spark alloying (VESA), pulsed cathodic arc evaporation (PCAE), magnetron sputtering (MS) techniques and VESA-PCAE-MS hybrid technology using Cr3C2–NiAl electrodes. The structure of the coatings was analyzed using scanning and transmission electron microscopy, X-ray diffraction and energy-dispersive spectroscopy. Mechanical properties were determined by nanoindentation, while tribological properties were assessed using pin-on-disk tribometer. Corrosion resistance was estimated by voltammetry in 1 N H2SO4 and 3.5%NaCl solutions. Oxidation resistance tests were performed at 800°С in air. The VESA coating had the highest thickness, low friction coefficient and high wear resistance. PCAE coating demonstrated the highest hardness (24 GPa) and elastic recovery (59%), oxidation resistance and superior corrosion resistance both in 1 N H2SO4 (icorr = 70 μА/cm2) and 3.5%NaCl (icorr = 0.74 μА/cm2) solutions. The MS coating had average mechanical properties and low corrosion current density (71 μА/cm2) in 1 N H2SO4. Deposition of coatings using VESA-PCAE-MS hybrid technology led to an increase in corrosion and oxidation resistance at least by 1.5 times in comparison with the VESA coating.

A new method for restoring worn surfaces of steel parts of pumping equipment, nuclear power plants

The paper proposes a new method of restoring worn surfaces of steel parts of pumping equipment used at nuclear power plants and subjected to radiation irradiation. The method belongs to the field of electrophysical and electrochemical treatment, in particular to electrospark alloying (ESA), and is applicable to repair parts of machines of nuclear power plants. The EBS method has a number of specific features: the anode material (alloyed material) can form a coating layer on the cathode surface (alloyed surface) that is extremely strongly bonded to the surface; the alloying can be performed in strictly specified places without protecting the rest of the part surface; the ESA technology for metal surfaces is very simple, and the necessary equipment is compact and transportable. The method includes coating of the worn surface of the part by electroplating with the same metal electrode - an instrument made of material (steel 12X18H10T or nickel) without special additives of cobalt and other elements that form long-lived isotopes in the active working environment. The electrodeposition is carried out in two stages. Before the first stage of coating with metallic electrode-tool a layer of coating with graphite electrode-tool with discharge energy Wp = 0.02 J and capacity 0.3 cm2/min is applied to the worn-out steel surface by ESA method, Then the first stage of coating layer application by ESA method by the metal electrode/tool at discharge energy 0.20-0.55 J and productivity 1.6-2.5 cm2/min ensuring surface thickness 0.09-0.16 mm and its continuity 100% , after that the surface obtained is subjected to the second stage of coating layer application by ESA method by the same metal electrode/tool with discharge energy 0.55-0.90 J and productivity 2.5-3.4 cm2/min.