Electric-spark Coatings Research Articles

Features of the Formation of Electric Spark Coatings on the Alloy CompoNiAl-M5-3 of Nickel Monoaluminide Using an Electrode of Eutectic Alloy Zr-18% Ni

To improve the service properties of the CompoNiAl-M5-3 nickel monoaluminide alloy, protective coatings were applied by electrospark deposition using electrodes from the Zr-18%Ni eutectic alloy. Coatings were applied in an argon atmosphere using vibration and rotation type manual processing tools with both direct and reverse polarities connected. It was established that the maximum total weight gain on the cathode of 11.17×10-4 cm3 was achieved in the case of using a rotary tool with direct polarity connected. The resulting coatings are characterized by 100% continuity with a thickness of 20–25 µm, a hardness of 11.6–14.6 GPa, and an elastic modulus of 162–174 GPa. The use of the electric spark processing contributes to an increase in the hardness of the CompoNiAl-M5-3 alloy by 1.4–1.8 times, wear resistance from 3.3 to 16.2 times, heat resistance at a temperature of 1150 °C for 5 h, and a decrease in the friction coefficient.

Characteristic Features of Structure and Analysis of Friction Behavior of Electric-Spark Coatings from Powder Wires

Characteristic Features of Structure and Analysis of Friction Behavior of Electric-Spark Coatings from Powder Wires

Modification of anode material VK8 by silicon for electric spark alloying of steel 35

Metal-ceramic coatings on steel 35 were obtained by the method of electric spark processing with different duration of control pulses, using a new electrode material WC—7.5 % Co—7.5 % Si for applying electric spark coatings on steel 35. It is shown that WC particles were deposited into the coating as a result of solid-phase transfer, which intensified with increasing discharge duration. The addition of silicon to WC—Co electrode materials can significantly reduce the coefficient of friction of the formed coatings. In general, the use of WC—Co—Si coatings can increase the heat resistance of steel up to 5 times, reduce the coefficient of friction of steel 35 to 47 %, and increase the wear resistance of its surface from 3 to 10 times.

Application of AlB$_{12}$–Al Electric Spark Coatings to Protect Titanium Alloys During Wear Under Fretting Corrosion

Application of AlB$_{12}$–Al Electric Spark Coatings to Protect Titanium Alloys During Wear Under Fretting Corrosion

Formation of electric spark WC-Co coatings with modifying Cr2O3 additives

Tungsten carbide coatings are widely used on steels due to their high hardness and wear resistance, but they have low high-temperature oxidation resistance and therefore need to be modified with oxidation resistance compounds. Electrode materials based on WC-8 %Co with addition of 1, 3 and 6 wt.% Cr2O3 were prepared by powder metallurgy for the deposition of electric spark coatings on steel 1035. An increase in the content of Cr2O3 in electrodes led to a rise in the thickness of the coatings from 18.2 to 28.3 µm. The tungsten semicarbide phase dominated in the structure of the coatings. The concentration of chromium in the coatings is a function of it in the electrodes. Polarization tests of coated samples showed an increase in the corrosion potential and a decrease in the corrosion current density with an increase of Cr2O3 concentration in WC-Co electrodes. The Cr2O3 additions into the WC-8 %Co electrode allow increasing the oxidation resistance of coatings at a temperature of 700°C. The coating microhardness increased monotonically from 9.6 to 13 GPa, the friction coefficient decreased from 0.7 to 0.58, and wear rate decreased with increasing Cr2O3 content. Electric spark deposition of the WC-8 %Co electrode with addition of Cr2O3 on steel 1035 allows increasing its wear resistance up to 14 times.

Электроискровое осаждение порошка диборида хрома на нержавеющую сталь AISI 304

Introduction. Austenitic stainless steel AISI 304 is the most widely used type of stainless steel. However, it is subject to wear due to relatively low hardness, and also begins to oxidize intensively in air at a temperature above 800 °C. The use of coatings based on chromium boride can improve its tribotechnical properties and oxidation resistance. The purpose of the work: to study the effect of chromium diboride concentration in the anode mixture on the structure, wear behavior, oxidation resistance and corrosion properties of electric spark coatings on AISI 304 steel. The research methods. Electric spark treatment of AISI 304 steel was carried out in a mixture of iron granules with the addition of CrB2 powder in amount of 5, 10 and 15 vol.%. The structure of the coatings was studied by X-ray analysis, scanning electron microscopy, and electron dispersion spectroscopy analysis. The wear resistance of the coatings was studied under dry friction condition at a load of 10 N. The oxidation resistance test was carried out at a temperature of 900 °C for 100 hours. Results and Discussion. According to X-ray analysis, it is shown that under the conditions of electric spark exposure, CrB2 interacts with iron melt; this has resulted in the formation of chromium and iron borides. Corrosion properties, microhardness, coefficient of friction and wear are investigated in comparison with AISI 304 steel. Samples with coatings showed a lower corrosion potential and corrosion current density compared to the substrate in 3.5% NaCl solution and from 5 to 15 times higher oxidation resistance. The microhardness of the coatings increased from 6.25 to 7.60 GPa with an increase in the addition of chromium diboride in the electrode mixture. The coefficient of friction and the wear rate of all coatings were lower than that of AISI 304 stainless steel, while the coating prepared with the addition of 5 vol.% chromium diboride had the best tribotechnical characteristics.

Влияние добавки Al2O3 в анодный материал WC – 8 Co на формирование покрытий, полученных электроискровым легированием

WC – Co coatings are widely used due to their high hardness and wear resistance, however, they have low resistance to high-temperature oxidation and therefore need modification with heat-resistant compounds. Anode materials based on WC – 8 % Co with the addition of 1, 3 and 6 wt. % Al2O3 for applying electric spark coatings on steel 35 were prepared. During the deposition of coatings, the erosion of the anode, of the total cathode weight gain the and the mass transfer coefficient were investigated. X-ray phase analysis of coatings showed the predominance of tungsten subcarbide in their composition. According to scanning electron microscopy and energy dispersion analysis, aluminum oxide was found in the structure of coatings in the form of micron and fine inclusions. Moreover, its amount in the coatings increased with an increase in the content of Al2O3 in the anodes. Potentiodynamic tests of the samples showed an increase in the corrosion potential and a decrease in the corrosion current density with an increase in the Al2O3 content in the coatings. The heat resistance of coatings at a temperature of 700 °C increased monotonically with an increase in the concentration of aluminum oxide. For 100 hours of testing, the weight gain of the samples with coatings was from 4 to 11 times less than that of uncoated steel 35. The microhardness of the alloyed layers ranged from 13 to 15.6 GPa, which is 4.6 to 5.4 times higher than steel 35. The coating with the highest concentration of aluminum oxide had the highest hardness. The wear rate of the coatings was 3.9 to 12.5 times lower compared to steel 35. With an increase in the concentration of Al2O3 in the anode material, the wear of electric spark coatings monotonically decreased from 1.45·10–5 to 0,45·10–5 mm3·N–1·m–1.

Thickness of electric spark coatings depending on the number of layers and the duty ratio

Thickness of electric spark coatings depending on the number of layers and the duty ratio

Properties of AlB$_{12}$–Al Electric Spark Coatings on D1 Aluminium Alloy

Properties of AlB$_{12}$–Al Electric Spark Coatings on D1 Aluminium Alloy

Research of properties of AlB<sub>12</sub>-Al electric spark coatings on VT1-0 titanium alloy

Research of properties of AlB<sub>12</sub>-Al electric spark coatings on VT1-0 titanium alloy

Influence of Continuity of Electric Spark Coatings on Wear Resistance of Aluminum Alloy

Influence of Continuity of Electric Spark Coatings on Wear Resistance of Aluminum Alloy

Tribotechnical Tests of Electric Spark Coatings

Tribotechnical Tests of Electric Spark Coatings

МЕТОДОЛОГИЧЕСКИЕ АСПЕКТЫ ПРИМЕНЕНИЯ ЭЛЕКТРОИСКРОВОГО ЛЕГИРОВАНИЯ. ЧАСТЬ 2: РАЗРАБОТКА МЕТОДОЛОГИИ ИССЛЕДОВАНИЯ, КРИТЕРИЕВ И ПОКАЗАТЕЛЕЙ ЭФФЕКТИВНОСТИ

There is no systematic information in the literature about the methodology for achieving the required functional properties of the executive surfaces of various objects: machine parts, tools and technological equipment for mechanical processing of materials in cold and hot conditions. (Research purpose) The research purpose is in developing a methodology for creating executive surfaces of parts for various purposes using electric spark alloying and justifying the criteria and parameters for evaluating this method. (Materials and methods) The authors created a methodological base by using the deductive method with gradual level specification and addition of the developed topics. The basis of the development was the four-link paradigm of G. V. Samsonov “composition-technology-structure-properties”, supplemented by a feature of the functional purpose of the material and extended features of the composition and technology. Authors used a hypothetical-deductive model for obtaining scientific knowledge to develop a methodology for creating executive surfaces of parts using the ESA method. (Results and discussion) The article shows the role of hardness, melting temperature, and elastic modulus of materials in the formation of electric spark coatings and their properties, identifies technological variants of the doped layer macrostructure, reveals the wettability of the anode material with the cathode material, the mutual solubility of the materials of the "anode-cathode-medium" system, and their chemical affinity. (Conclusions) The article presents the methodological schemes for the study and selection of the anode material, which largely determines the desired properties of the doped layer. Authors proposed a methodological approach to the development of criteria and indicators for the effectiveness of electric spark alloying, analysis and generalization of the main methodological provisions for strengthening and restoring the executive surfaces by this method, taking into account their functional purpose. The article considers a number of dominant factors that affect the efficiency of electrospark doping, as well as the selection and development of performance criteria in the field of surface materialology.

Evaluation of the wear resistance and resource hardened by electrospark machining of the cutting surfaces of the fingers of the headers of combine harvesters

The article presents the technology of hardening the fingers of the reapers of combine harvesters by electrospark processing. To strengthen the cutting surfaces of the fingers, it is recommended to use an amorphous alloy grade 84KXSR. The operational tests presented in the work showed that wear and dulling of both serial products and experimental parts with electric spark coatings is characterized by two stages: running-in and natural wear. The running-in occurs during the running time of the fingers in 1 ha. The results of operational tests showed that the application of a wear-resistant electrospark coating of amorphous alloy grade 84KXSR with a thickness of 30 μm and a track width of 2 mm on the cutting surfaces of the fingers of the headers of grain harvesters makes it possible to increase the resource from 1.4 to 2 times.

Frictional Strength of Electric Spark Coatings from Powder Wires under Friction without Lubrication

Frictional Strength of Electric Spark Coatings from Powder Wires under Friction without Lubrication

Causes of gear pump fails and methods for their elimination

Gear pumps are an important element of many production systems and their replacement in case of failure can be quite expensive, so it is important to have a modern and well-tuned technology for their recovery. There are many methods for restoring the pump's performance, depending on the reason that led to its failure. (Research purpose) The research purpose is in determining what causes most often lead to loss of pump performance, and developing a recovery method that provides the greatest post-repair service life of the pump and low cost of repair. (Materials and methods) Authors took into account that the applied coatings must have sufficient adhesion strength and resistance to mechanical, thermal and corrosion loads during operation. It was found that most often significant leaks of the working fluid, leading to failure, occur due to an increase in the gap between the inner surface of the housing and the gears due to active wear of the housing wells. Authors determined that the method of electric spark treatment of worn-out housing wells is best suited to perform the task (a large post-repair resource and low costs). (Results and discussion) It was found by laboratory studies of the adhesion strength of electric spark coatings with various electrodes that the best transfer of the material to the substrate is provided by bronze electrodes BrMKts3-1. It was noted that the coatings applied using the BrMKts3-1 electrode have high strength properties. (Conclusions) Research conducted in the center for collective use "Nano-Center" VIM confirmed the possibility of effective recovery of the gear pump by electric spark treatment.

Study of electric spark coatings of nanocrystal structure

The article presents the results of studies of new electrospark coatings having an amorphous and nanocrystalline structure. The results of metallographic and X-ray diffraction studies are analyzed. The microhardness and thickness of the coatings were studied. For the formation of a nanostructure, a plasma spraying method is used, in which materials are formed upon separate solidification of particles, most often disk-shaped. When the thickness of the sprayed particles is up to 10 μm, they quench from the liquid state at a cooling rate of 108 K / s. Nonequilibrium structures in sprayed particles with a nanocrystalline and amorphous structure have high mechanical properties. However, the use of plasma spraying in some cases is not advisable, due to the relatively high cost of equipment and materials. Therefore, this article will present the results of studies on the creation of amorphous and nanocrystalline coatings using electrospark processing (ESP), which is a cheaper way to obtain them.

Increasing the thickness of electric-spark coatings

The work is devoted to the urgent problem of increasing the thickness of the electro — spark coatings. The analysis of published papers related to the study , the reasons cheniem restrictions thickness of coatings and methods of increasing it.

Friction Behavior of Electric-Spark Coatings Under the Conditions of Boundary Lubrication

Friction Behavior of Electric-Spark Coatings Under the Conditions of Boundary Lubrication

Restoration of cylinder liners for automotive tractors engines in modern conditions

One of the most promising technologies for restoring machine parts and cylinder liners is electric spark treatment as the most versatile technology that provides high-quality restoration of worn parts with wear up to 0.5 mm. (Research purpose) The research purpose is in developing a technology for restoring various cylinder liners by means of electric spark processing, selecting optimal modes and electrode materials that allow improving the quality of repair and increasing the post-repair life of the sleeve. (Materials and methods) It was taken into account when conducting research aimed at restoring the geometric parameters of the sleeve, that the coating must have sufficient adhesion strength to the surface of the sleeve under mechanical, thermal loads and long-term operation. Laboratory studies of the adhesion strength of electric spark coatings on the separation (adhesive) and on the cut, as well as tribotechnical studies of interfaces were conducted. Authors have found by analyzing the results of operational tests of restored and new cylinder liners the prospects for using electric spark treatment of worn parts, including diesel engine liners. (Results and discussion) It was shown by laboratory studies of the adhesion strength of electric spark coatings with a 0.2 mm thick BrMKc 3-1 electrode to the working surface of cylinder liners that their separation strength (adhesive) was 20-40 megapascals, and the shear strength (cohesive) was 50-80 megapascals. It was found that this provides the required functional strength of coatings with maximum operational load. The article presents the results of comprehensive research in graphs and tables. (Conclusions) The research conducted in the CCP "Nano-Center" of the FSAC VIM and operational tests in the 2nd bus fleet of Moscow confirmed the principal possibility of effectively restoring cast iron liners (blocks) using the technology of electric spark processing.