Electrospark Coatings Research Articles

Influence of manganese alloying on the structure and properties of electrospark coatings of EP741NP heat-resistant nickel LPBF alloy

The paper investigates the impact of Mn content (Mn = 0; 0.5; 0.6; 1; 1.5 at.%) in the composition of the electrodes of the Al–Ca–Mn system on the structure and properties of electrospark coatings formed on LPBF substrates made of EP741NP alloy. It was found that the highest weight gain of the substrate (5.8·10–4 g) was recorded when the Al–7%Ca–1%Mn electrode with a low degree of supercooling of the melt (Δt = 5 °C) was subject to electrospark treatment (EST). EST with this electrode with a fine eutectic structure enables the formation of coatings with minimal surface roughness (Ra = 3.51±0.14 μm). The nanocrystalline structure of the coatings was confirmed by transmission electron microscopy, including HRTEM. Comparative tribological tests revealed that the coating with maximum hardness (10.7±0.8 GPa) formed during EST with an electrode containing 1.5 at.% Mn had the minimal wear rate (1.86 ·10–5 mm3/(N· m)). We proved that EST with Al–Ca–Mn electrodes enables to reduce the specific weight gain of the LPBF EP741NP alloy during isothermal (t = 1000 °C) curing in air due to in situ formation of a complex thermal barrier layer consisting of oxides (α-Al2O3, CaMoO4) and intermetallides (γ ′-Ni3Al and β-NiAl). We determined the concentration limit of Mn (1.0 at.%) in the electrode, at which the barrier layer retains its integrity and functionality.

Features of Electrospark Coatings Formation on a Chromium Substrate Using Ceramic ZrSi2-MoSi2-ZrB2 and HfSi2-MoSi2-HfB2 Electrodes

The work is devoted to the study of the features of mass transfer, structure and properties of electrospark coatings on substrates made of the chromium alloy grade VKh1-17A using SHS-electrode ceramics of the compositions ZrSi2-MoSi2-ZrB2 and HfSi2-MoSi2-HfB2. The coatings were studied using X-ray diffraction, scanning electron microscopy, energy-dispersive analysis, and tribological tests using the “pin-on-disk”; nanoindentation was also carried out. The kinetics of the mass transfer and heat resistance of coatings were determined by the gravimetric method. In accordance with the Palatnik criterion, the formation of coatings occured in the form of an alloy of an anode (electrode) and a cathode (substrate) materials, which ensures high adhesion of the surface layer. The maximum weight gain on the cathode was observed after the first minute of treatment, and subsequently a decrease in the mass of the cathode was noted. As a result of electrospark deposition, coatings with 100% continuity and a thickness of 10–20 µm were deposited on the surface of the chrome alloy VKh1-17A. Zirconium-containing coatings are characterized by a hardness of 18.2 GPa and an elastic modulus of 274 GPa, and coatings obtained using the HfSi2-MoSi2-HfB2 electrode were characterized by a hardness of 16.9 GPa and an elastic modulus of 332 GPa. The use of SHS-electrodes made it possible to increase the hardness of the surface layer of the chromium alloy by 4 times, wear resistance by 1.5 times, and oxidation resistance by 1.6 times at t 1000 °C for 30 hours of testing.

Physical and Mechanical Properties of Electrospark Coatings Applied by Electrospark Treatment with a Composite Electrode

Physical and Mechanical Properties of Electrospark Coatings Applied by Electrospark Treatment with a Composite Electrode

Features of the Formation of Electrospark Coatings on the CompoNiAl-M5-3 Alloy Produced from Nickel Monoaluminide Using an Electrode Made of Zr–18% Ni Eutectic Alloy

Features of the Formation of Electrospark Coatings on the CompoNiAl-M5-3 Alloy Produced from Nickel Monoaluminide Using an Electrode Made of Zr–18% Ni Eutectic Alloy

Influence of Electrospark Coatings of Tool on Force Indices of Milling of Wooden Materials

Influence of Electrospark Coatings of Tool on Force Indices of Milling of Wooden Materials

Investigation of the Lubricated Tribo-System of Modified Electrospark Coatings

This work presents the results of tribological tests of Mo and combined coatings TiAlC formed using electrospark alloying (ESA) technology and additionally processed using thermochemical electrolyte anodic heating (TEAH). ESA makes it possible to form 15–20 µm thick coatings on the friction surface, characterized by a high hardness and wear resistance. Tribological studies were performed by testing the block-on-roll friction pair under 300 N and 600 N loads. The duration of the tests was 180 km of friction path, and the constant rotation rate of the disk was 600 rpm. It was observed that the friction torque during the 300 N loading tests was stable for all samples and throughout the entire testing period, whereas at 600 N loading, the pair with the Mo coating had a decreasing trend, and the pair with the TiAlC coating, friction torque slightly increased. For a reference sample without the coating trend of friction torque became drastically unstable. At both loads (300 N and 600 N), the friction pair with the reference sample had the highest cumulative wear, and the pair with the Mo coating had the lowest. At both loads, the cumulative wear of the friction pair with Mo coating is about 2 times lower than the TiAlC, and ≥1.8 times lower than the control (not coated) version. This study shows that at lower loads, the friction pair formed by the TiAlC coating and steel C45 is more matched than the friction pair with Mo coating.

Properties of Electrospark Coatings

Properties of Electrospark Coatings

Assessment of Tribotechnical Properties of Consolidated Materials Obtained by Electrospark Processing

Abstract Introduction. The bakery industry is an agricultural industry of high-level processing of raw materials focuses on the end-consumer. In the production of bakery products one of the operations of the technological process is performed by dough dividers of vacuumpiston type, whose service life is 30‒40% lower than the normative. The most promising method for restoration of worn parts of the suction mechanism is electrospark processing. When selecting the electrode material, it is important that they have not only low erosion resistance, but also high tribotechnical properties. Aim of the Article. The article deals with problem of selecting electric coatings to reduce wear of working surfaces of suction mechanism parts during repair of vacuum piston-type dough dividers. Materials and Methods. The analysis of the properties of electropark coatings was carried out by nondestructive testing methods using modern research equipment; the results were processed using the Compass-3D program. Results. There are determined the values of physical, mechanical, frictional and tribotechnical properties of electrospark coatings made of BrOS10-10 bronze and Kh15N60 alloy. The total wear rate for BrOS10-10 bronze coating was 8,3 ∙ 10‒12, and for Kh15N60 alloy 15 ∙ 10‒12. Discussion and Conclusion. Total wear rate on the friction machine of bronze coated samples is lower than that of basic friction pair in 1.4 times, and of alloy coated samples ‒ higher in 1.26 times. Adding of MODENGY solid-lubricant coating to the coating from the alloy reduces its abrasion ability by 3 times, and the total wear rate ‒ by 1.34 times in comparison with the base friction pair. The used calculation-experimental method showed low wear rate of electrospark coatings of bronze and alloy in relation to the material of parts of the suction mechanism of vacuum-piston-type dough dividing machines.

Synthesis of Multicomponent Coatings by Electrospark Alloying with Powder Materials

The results of systematic studies of the electrospark alloying process with the introduction of dispersed materials into plasma of low-voltage pulsed discharges are presented. Technological methods have been developed for supplying the powder material straight into the treatment zone through a hollow electrode of an anode or from the side, with the electrode-anode periodically contacting the substrate of cathode. It has been established that under the same energy regimes, when powder materials were introduced into the discharge zone, the increase in the mass of the cathode per time unit increases from 10 to 15 times or more. This study presents the process of synthesis of carbide phases (TiC and WC) during electrospark alloying of steel substrates with electrodes made of Ti, W, and graphite, with additional supply powders of these materials into the processing zone. A process has been developed for the synthesis of ternary compounds, so-called MAX-phases: Ti2AlC, Ti2AlN and Ti3SiC2 by electrospark alloying with powder compositions TiAlC, TiAlN and TiSiC. These MAX phases exhibit a unique combination of properties that are characteristic of both metals and ceramics. Energy modes of the processing were optimized, which resulted in high-quality coatings with the maximum content of carbide phases and ternary compounds. It has been established that the energy of electrical pulses during electrospark alloying, when powders of materials are fed into the interelectrode gap, ranges from 0.8 to 3.0 J, depending on their thermal physical properties. High wear and corrosion resistant characteristics of C45 structural steel with such electrospark coatings are obtained. The wear of steel with coatings in comparison with uncoated steel decreased by an average of 5.5–6.0 times. It was estimated the high corrosion resistance of 40X13 steel coated with TiC and WC in 3% NaCl solution. The corrosion current for these coatings is 0.044 and 0.075 A/cm2, respectively, and is significantly less than for coatings made of TiAlC, TiAlN, and TiSiC compositions. X-ray phase and optical metallographic microscopy analyses enabled the display of the amorphous-crystalline nature of the coatings.

Increasing the Wear Resistance of Restored Car Parts by Using Electrospark Coatings

The work scientifically substantiates the application of effective technology for the restoration of worn car parts by applying new electrospark coatings based on electroerosion nanomaterials. The developed technology is characterized by technological flexibility, cheapness, simplicity, does not require the use of expensive and scarce materials and equipment, and also meets the requirements of environmental safety. The proposed technology can be used to restore a wide range of parts for cars, tractors and other machines. Experimentally established dependences of the effect of the properties of electroerosive materials on the properties of electrospark coatings of restored car parts. It is shown that the content of nano-sized particles in the electrode material contributes to the improvement of the physical and mechanical properties of electrospark coatings. The dependences of the influence of the properties of electrospark coatings on the resource of restored car parts were experimentally established. It is shown that the resource of the shafts of turbocompressors restored according to the recommended technology is higher than the resource of new shafts by an average of 1.5 times. Experimentally established rational modes of applying wear-resistant coatings to worn shafts of turbocompressors, which provide the necessary complex of physical and mechanical properties of the coating and the given resource of the shafts as a whole (rotation frequency of the part, min - 1 - 50; electrode feed, mm/min - 0.4 ... 0.5). The characteristics of wear resistance of electrospark coatings of turbocompressor shafts, obtained using electroerosion nanomaterials, were studied. It is shown that the average value of the coefficient of friction of the electrospark coating was 0.146 instead of 0.486 without coating, which is 3.3 times lower. According to the results of production tests, it was found that the duration of operation of the turbocharger, with the restored method of electrospark treatment with a nanostructured electrode shaft, increased by 2.1 times compared to a new industrially manufactured shaft. Thus, when abrasive material containing a fraction of 0.1...0.4 mm was introduced, the operating time of the turbocompressor with a restored shaft was 12.8 hours, and the operating time of the turbocompressor with a new shaft without wear of the nominal size was 8.1 hours.

Influence of TiC Addition on Corrosion and Tribocorrosion Resistance of Cr2Ti-NiAl Electrospark Coatings

Marine and coastal infrastructures usually suffer from synergetic effect of corrosion and wear known as tribocorrosion, which imposes strict requirements on the structural materials used. To overcome this problem, novel composite wear- and corrosion-resistant xTiC-Fe-CrTiNiAl coatings with different TiC content were successfully developed. The coatings were obtained by the original technology of electrospark deposition in a vacuum using xTiC-Cr2Ti-NiAl (x = 0, 25, 50, 75%) electrodes. The structure and morphology of the coatings were studied in detail by XRD, SEM, and TEM. The effect of TiC content on the tribocorrosion behavior of the coatings was estimated using tribological and electrochemical (under stationary and wear conditions) experiments, as well as impact testing, in artificial seawater. The TiC-free Fe-Cr2Ti-NiAl coating revealed a defective inhomogeneous structure with transverse and longitudinal cracks. Introduction of TiC allowed us to obtain coatings with a dense structure without visible defects and with uniformly distributed carbide grains. The TiC-containing coatings were characterized by a hardness and elastic modulus of up to 10.3 and 158 GPa, respectively. Formation of a composite structure with a heavily alloyed corrosion-resistant matrix based on α-(Fe,Cr) solid solution and uniformly distributed TiC grains led to a significant increase in resistance to stationary corrosion and tribocorrosion in artificial seawater. The best 75TiC-Fe-CrTiNiAl coating demonstrated the lowest corrosion current density values both under stationary (0.03 μA/cm2) and friction conditions (0.8 μA/cm2), and was characterized by both a 2-2.5 times lower wear rate (4 × 10−6 mm3/Nm) compared to AISI 420S steel and 25TiC-Fe-CrTiNiAl and a high fracture toughness.

Research of physical and mechanical properties of electrospark coatings

Brief information about the method of electrospark processing and the results of studies of the properties of electrospark coatings are given. The prospects of using electrospark machining for high-quality restoration of parts are shown. Keywords: electrospark processing, technology, electrode, part, restoration, coating, microstructure, adhesion. valpal-1938@mail.ru

ИССЛЕДОВАНИЯ ВЛИЯНИЯ ЧАСТОТЫ ВРАЩЕНИЯ ЭЛЕКТРОДА НА ТОЛЩИНУ ЭЛЕКТРОИСКРОВЫХ ПОКРЫТИЙ ПРИ РАЗЛИЧНЫХ РЕЖИМАХ ЭЛЕКТРОИСКРОВОЙ ОБРАБОТКИ ПОВЕРХНОСТЕЙ

The article presented actual problems studies of the thickness of electro spark coatings depending on the specified processing modes of the electro spark installation with a change in the frequency of rotation of the electrode. We propose to optimize the values of the parameters of the electro spark installation model SZ-8100, current frequency, current cycle pulse duration and frequency of rotation of the electrode to increase the thickness of the electro spark coating. As a result of experimental studies, the following results were obtained: the most thickness of the electro spark build up obtained at a pulse duration timp = 100 microseconds, voltage U = 60V, current frequency f = 300 Hz, at an electrode rotation frequency n = 260 min–1 and it is 1.88 mm (along the roughness vertices). In experimental studies, it was found that the current frequency parameter has a significant effect on the temperature regime of heating the surfacing electrode. Electro erosive destruction of particles by an electro spark processing, with an increase in the current frequency parameter, occurs. An increase in the pulse duration timp from 50 microseconds to 100 microseconds contributed to an increase in the thickness of the electro spark build up by 0.84 mm. It was found that in the case of an increase in the rotation frequencies of the electrode on the electrode holder, the tops of the formed electro spark grind polished, cooled faster and the thicknesses of electro spark coatings obtained with lower productivity. The smallest thicknesses of the electro spark build up formed at low values of the current frequency at f = 50 Hz, in both modes of the current duty cycle timp = 50 microseconds, timp = 100 microseconds and the formation of the thickness of the electro spark build up in the aisles varies from 0.04 mm to 0.45 mm. This study will help to choose the optimal values of the parameters of the electro spark installation, and increase the productivity of the process obtaining an effective thickness of the electro spark coating.

Structural composition of electrospark coatings obtained by Ni—Al alloys on steels

Coatings were obtained by electrospark deposition using anode materials based on the Ni-Al system. According to the research results it is most expedient to use two alloys based on Ni3Al and NiAl with an additional content of the Ni5Al3 phase for the coatings formation. The microstructure of the resulting coatings consists of columnar crystallites, in which the concentration of the anode components (Ni, Al) increases, and the content of the cathode component (Fe) decreases along the height of the coating from the surface to the base. It has been established that the content of Fe in crystallites in different areas of the coating changes most significantly.

Determining the Young Modulus of Electrospark Coatings by Instrumental Indentation

Determining the Young Modulus of Electrospark Coatings by Instrumental Indentation

Structure Formation and Tribological Properties of Mo-Si-B-Hf Electrospark Coatings Based on Mo2Ni3Si Laves Phase.

Coatings were produced on the EP741NP nickel alloy substrates by electrospark deposition (ESD) in argon using an MoSi2-MoB-HfB2 electrode. In situ high-resolution transmission electron microscopy and X-ray diffraction analysis studies have identified the temperature above which the strengthening Mo2Ni3Si Laves phase is formed in the coatings. At 25 °C, the coatings with a predominant content of the Laves phase are characterized by enhanced wear resistance, as well as a lower coefficient of friction compared to the non-annealed coatings containing binary silicides. At 700 °C, the EP741NP substrate was characterized by the lowest friction coefficient (Ktr = 0.35), and its wear was approximately at the same level as the wear of both coatings.

Improvement of electrospark deposition technology of steel units for drilling rigs and mining equipment

Introduction. The development of modern equipment and technologies for geological exploration and mining processes raises the problem of ensuring the reliability and durability of mechanic units operating under the conditions of elevated temperatures and pressures in the presence of aggressive external environments. In this regard, there is a need to create functional coatings with unique physical, mechanical and operational properties.Aim. To improve the performance of electrospark coatings based on an analysis of a cause-andeffect diagram and a regression study of the technological modes of processing steel units of geological exploration equipment (on the example of hydraulic cylinder rods of drilling pumps).Materials and methods. To harden the steel surfaces of hydraulic equipment parts, the technology of electrospark deposition (ESD) was used on an IMES-1001 mechanized installation using carbide electrodes and various gas media. In order to identify causal relationships between the factors affecting the hardened surface and to establish the most important factors affecting the quality of the formed coating, the Ishikawa diagram method was used and a regression analysis was performed. The adhesion activity of the obtained coatings was assessed by atomic force microscopy on a Solver PRO scanning probe microscope in a semi-contact air scanning mode using NSG10probe sensors with a resonance frequency of 219 kHz and a radius of curvature of the probe tip of 10 nm. When determining the strength of the adhesive interaction of the probe and the surface at one point, the absolute error was 15 nN. Tribological tests were carried out on a 2070-СМТ-1 standard friction machine according to the “disk-shoe” scheme.Results. The obtained cause-and-effect diagram showed that the technological modes of an electrospark deposition installation comprise a determining factor affecting the quality of the formed layers and coatings. In order to identify those process parameters that had the greatest effect, a regression analysis was carried out. The capacitance of the unit capacitors was found to have the greatest impact on the adhesion force formed by the ESD coating. Therefore, in order to reduce the strength of the adhesive interaction of surfaces and, as a result, increase their wear resistance, it is necessary to increase the capacitance of capacitors while reducing the voltage and processing time when implementing the ESD technology. On the basis of tribological tests, it is concluded that the minimum wear rate of coatings can be obtained by alloying the steel surface in an oxygen environment with a carbide electrode based on tungsten carbide with additives of elements that form unlimited solid solutions with the surface material and perform the role of fluxes (Ni-Cr-B-Si).Conclusion. Due to strict requirements to the performance of metal surfaces of units that enter into frictional interaction during the implementation of mining and exploration processes, there is a need to improve existing technologies for creating functional (wear-resistant) coatings.

Abrasive Wear Resistance of Electrospark Coatings on Titanium Alloys

Abrasive Wear Resistance of Electrospark Coatings on Titanium Alloys

Effect of current pulse duration on the thickness and roughness of electrospark coatings

The effect of the current pulse time on the roughness and surface continuity of the electrospark coating is studied. It is established that in the coating mode: the current pulse time is 2•10–5 s, the frequency is 250 Hz, the stress is 50 V, the roughness parameter is Rz = 80 µm, the continuity is high, but the disadvantage is the low productivity of the process.

Особенности формирования фазового и элементного состава при электроискровом легировании ручным вибратором повышенной частоты

The phase and elemental compositions of electrospark coatings of nickel and titanium deposited on steel, nickel, and titanium, that is, coatings from TiNiMo-20 and WC92-Co8 on steel at high-frequency electrospark alloying are investigated. It is established that the material of the electrode, of the substrate, and the mode of deposition have the main impact on physical and chemical properties of the formed coatings. A positive influence of high-frequency alloying on quality indicators of the processed surfaces is shown. Both the phase and chemical analyses showed availability of the compounds considerably improving corrosion resistance of the processed surfaces. Alloying with WC92-Co8 electrodes at a high frequency makes it possible to obtain an increased content of tungsten carbide in the deposited layer.