Electrospark Treatment Research Articles

Effect of Ultrasonic Impact Electrospark Treatment on the Flexural Response of Welded Joints of Additively Manufactured Ti-6Al-4V Alloy

Effect of Ultrasonic Impact Electrospark Treatment on the Flexural Response of Welded Joints of Additively Manufactured Ti-6Al-4V Alloy

Improving the wear and heat resistance of niobium substrate via reactive electrospark treatment using fusible AlCaSiY electrode

Protective coatings with a heterophase layered structure were obtained by reactive electrospark treatment (EST) of niobium substrate with a fusible AlCaSiY electrode. The effect of the frequency–energy modes of EST on the phase composition, structure and properties of the coatings was studied. A combination of high discharge current values (400A) and long pulses (100 μs) yields a double-layer coating with the total thickness of 80 μm, which consists of the (Al) matrix strengthened with Nb2CaAl20 particles and a hard (10 GPa) NbAl3 layer. The results of pin-on-plate tribological testing revealed that this structure made it possible to reduce the coefficient of friction from 0.42 to 0.24 and increase wear resistance 3.5-fold compared to those of niobium. Oxidative annealing of Nb plates in air at 700 °C causes their fracture due to the formation of Nb2O5. Indeed, oxidative annealing of the samples subjected to EST leads to in situ formation of a dense Ca12Al10Si4O35-oxide based near surface layer that inhibits oxygen diffusion into the bulk, thus suppressing Nb2O5 formation. Mass gain of the sample having a protective coating after 300-min isothermal exposure was 2.54 mg/cm2, which is 3.6-fold lower than that for the Nb substrate (9.04 mg/cm2).

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.

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

Электроискровое модифицирование поверхности аддитивного сплава ВТ6 высокоэнтропийным и аморфным электродами

Unsatisfactory quality of the surface layer of additive products, in particular increased surface roughness, prevents the widespread use of electron beam powder bed fusion (EBPBF). Electrospark treatment (EST) is one of the methods for smoothing and hardening the surface layer. The work shows the possibility of modifying the surface of additive VT6 alloy samples by reactive EST with multicomponent electrodes. For this purpose, the authors used electrodes made of the Fe48Cr15Mo14Y2C15B6 bulk metallic glass forming alloy and the FeCoCrNi2 high-entropy alloy. Based on the results of scanning electron microscopy, it was identified that after EST, both modified layers have a thickness of about 16 μm. X-ray diffraction phase analysis showed that in the case of treatment with an amorphous electrode they contain carboborides of the Ti(B,C) type, and in the case of treatment with a high-entropy electrode – intermetallic of the Ti2(Fe,Ni) type. The modified layers have average hardness values of 19 and 10 GPa and elastic modulus of 234 and 157 GPa, respectively, which significantly exceeds the values of these parameters for the EBPBF-grown VT6 alloy. Electric discharge modification of the surface with multicomponent electrodes led to a decrease in roughness by 8...11 times due to the melting of the protrusions and filling of the dimples with the melt to a depth of more than 50 μm. A comparative analysis of the results of tribological tests showed a change in the wear mechanism as a result of EST of the additive VT6 alloy. Wear resistance increased by 4 and 3 orders of magnitude when using electrodes made of a bulk metallic glass and high-entropy alloy, respectively.

Residual Stresses in Coatings Formed by Electrospark Treatment

Residual Stresses in Coatings Formed by Electrospark Treatment

Residual Stresses in Coatings Formed by Electrospark Treatment

A review and analysis of the influence of electrospark treatment on the residual fatigue limit of parts as well as of the degree of influence of electrospark surfacing on the fatigue strength of automotive parts restored by electrospark treatment are given. We present rational technological regimes for electrospark coating deposition and rolling under plastic deformation of the surface of electrospark coatings used in the restoration of worn parts.

Transformations of the Microstructure and Phase Compositions of Titanium Alloys during Ultrasonic Impact Treatment Part III: Combination with Electrospark Alloying Applied to Additively Manufactured Ti-6Al-4V Titanium Alloy

Scanning electron microscopy, 3D optical surface profilometry, as well as X-ray diffraction and electron backscatter diffraction analysis were implemented for studying the effects of both ultrasonic impact treatment (UIT) and ultrasonic impact electrospark treatment (UIET) procedures on the microstructure, phase composition, as well as the mechanical and tribological properties of Ti-6Al-4V samples fabricated by wire-feed electron beam additive manufacturing. It was shown that he UIET procedure with the WC-6%Co striker enabled to deposit the ~10 µm thick coating, which consists of fine grains of both tungsten and titanium-tungsten carbides, as well as titanium oxide. For the UIET process, the effect of shielding gas on the studied parameters was demonstrated. It was found that the UIET procedure in argon resulted in the formation of a dense, continuous and thick (~20 µm) coating. After the UIET procedures in air and argon, the microhardness levels were 26 and 16 GPa, respectively. After tribological tests, wear track surfaces were examined on the as-built sample, as well as the ones subjected to the UIT and UIET procedures. It was shown that the coating formed during UIET in air had twice the wear resistance compared to the coating formed in argon. The evidence showed that the multiple impact of a WC-Co striker with simultaneous electrical discharges was an effective way to improve wear resistance of the Ti-6Al-4V sample.

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.

Analysis of Available Data and Estimation of Energy Supply of Mechanical Processing

The issue of energy efficiency of machining processes has been the focus of attention for the last 50 years. This is due to the fact that in comparison with other industries, metallurgy and mechanical engineering are characterized by a high level of energy intensity of products. Analysis of available in the literature indicators of energy costs of processing processes and determination of consistent data from these indicators. Establishing an analytical relationship between the grinding energy and the energy required for melting the finishing material. It is determined that the cutting energy of the material during chip for­mation is close to the energy required for melting the metal, and the excess amount of spent grinding energy is spent on friction between the chips and the grinding wheel. It is shown that in the literature there are data on the energy consumption of different treatments: turning - 2 kJ/cm3, milling - 9 kJ/cm3, grinding - 60 kJ/cm3, electrospark treatment - 3000 kJ/cm3. At the same time, the specific energy consumption of steel grinding is 60 kJ/cm3. And the specific heat of fusion of steel is 0.64 kJ/cm3. As a result, 100 times more heat is pumped into the steel during grinding than is needed to melt it. That is, there is a contradiction. To find ways to resolve this contradiction, it is more accurate to estimate the specific energy consumption of diamond-abrasive machining of superhard materials through additional consideration, in addition to productivity and effective machining power, wear of the working layer of the wheel.

Electro-Spark Treatment with Low-Melting Al–Si and Al–Ca Electrodes in Order to Improve Wear and Oxidation Resistance of EP741NP Alloy Prepared by Selective Laser Melting

Electro-Spark Treatment with Low-Melting Al–Si and Al–Ca Electrodes in Order to Improve Wear and Oxidation Resistance of EP741NP Alloy Prepared by Selective Laser Melting

Hydrothermal deposition of MoS2 on electrospark Ti – Al coatings on Ti6Al4V alloy and their characteristics

Antifriction layers on titanium alloy Ti6Al4V can be obtained by creating a developed structure of lubricant pockets, followed by the application of dry self-lubricating substances. The structure and tribological behavior of Ti – Al intermetallic coatings after hydrothermal deposition of molybdenum disulfide (MoS2) have been studied. Titanium aluminide coatings with a regular network of cracks were obtained by electrospark treatment of the Ti6Al4V alloy in an equimolar mixture of titanium and aluminum granules. To fill the lubricant voidnesses in the MoS2 coatings, the hydrothermal synthesis method was used in a solution of thiourea and sodium molybdate at 220 oC. The structure of the coatings was studied by X-ray diffraction analysis, scanning electron microscopy, X-ray microanalysis, and Raman spectroscopy. The wear resistance of the coatings was studied according to the ASTM G99 standard with dry sliding friction using counterbodies in the form of discs made of high-speed steel P6M5 at a speed of 0.47 m/s under a load of 25 N. It was found that intermetallic compounds Ti3Al, TiAl, TiAl3 and TiAl2 were overwhelming. In the structure of Ti – Al coatings, a regular network of cracks with a thickness of 0.77 ± 0.3 μm and a specific area on the coating surface of 2.2 ± 0.35% was established. It was shown that as a result of hydrothermal synthesis, a MoS2 layer is formed on the surface of the samples, consisting of spherical particles with a diameter of 3.09 ± 0.63 μm. Based on the data of energy dispersive spectroscopy (EDS) mapping, it was concluded that cracks in Ti – Al coatings are also filled with MoS2. According to the results of tribological tests, it was found that the hydrothermal deposition of MoS2 on Ti – Al coatings enables to reduce their friction coefficient by 30%, and the reduced wear in dry sliding friction by 2 times. The conducted studies show the promise of hydrothermal deposition of MoS2 on Ti – Al coatings in order to study tribotechnical properties.The study was supported by the Russian Science Foundation (No. 19-73-00031).

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.

Phase and Structural Transformations in the Fe-Based Alloys under the Combined High-Energy Treatment

Applying the x-ray, metallographic, and microdurometric methods, the phase composition and structural–stress state of the Fe-based alloys under the impact of electrospark treatment in combination with laser processing are studied and analysed. As shown, the structural–phase state of electrospark coating on the steel substrate is determined by several factors. They are the dissociation of WC carbide on the surface of alloying electrode on the W2C and W components followed by their erosion, an interaction of erosion products with elements of the interelectrode medium (C, N, O), an interdiffusion of the coating elements and a steel substrate, and the ascending diffusion of C from the substrate near-surface layers. As revealed, the heterophase coating and near-surface layers of substrate possess a complex structural–stress state. As shown, the residual stresses in different phase components have been formed through different regularities: the tensile stresses in the TiC-based compound, while the compressed stresses in the W2C, W, and Feα. The selective effect of laser heating of the coating on the stresses of different signs is revealed.

Surface Modification of Titanium VT6 Alloy Obtained by Additive Technologies Using Reactive Electrospark Treatment

Surface Modification of Titanium VT6 Alloy Obtained by Additive Technologies Using Reactive Electrospark Treatment

Microstructure, Phase Composition, Substructure and Residual Stress of AK5M7 Aluminum Alloy after its Electrospark Treatment

Microstructure, Phase Composition, Substructure and Residual Stress of AK5M7 Aluminum Alloy after its Electrospark Treatment

Упрочнение FeCrMoWCBSi аморфных электроискровых покрытий карбидом вольфрама

A new direction in the development of metal-matrix coatings are composites based on an amorphous matrix with reinforcing ceramic additives. In this work, composite coatings were prepared by electrospark treatment of AISI 1045 in a mixture of iron granules with a multicomponent composition CrMoWCBSi and the addition of tungsten carbide powder. According to X-ray analysis, with an increase in the concentration of WC in the mixture of granules up to 1.2 vol.%, the content of the WC phase in the coating composition increased. In addition, the X-ray analysis showed metallic tungsten, which is a product of the partial dissolution of WC particles in the iron melt. In the microstructure of the coatings, inclusions of tungsten carbide with a diameter of 1.8 ± 0.9 μm were observed. The oxidation resistance of the coatings at a temperature of 700°C decreased monotonically with an increase of WC additive in the mixture of granules. The microhardness of the coatings with tungsten carbide was in the range from 814 to 1118 HV, which is higher compared to a completely amorphous sample (743 HV). The average values of the coating friction coefficient with WC ranged from 0.60 to 0.67, which is 30 % lower than that of an amorphous coating. The wear rate of coatings with tungsten carbide was in the range of 0.5 –1.1×10−5 mm3 / Nm, which is lower than that of the sample without WC (1.8 ×10−5 mm3 / Nm). The optimal value of the addition of WC powder in the mixture of granules during the deposition of the coatings for tribotechnical applications is 1.2 vol.%. Thus, the use of amorphous coatings reinforced with tungsten carbide makes it possible to reduce the wear of steel 45 by up to 8 times.

Liquid-phase hydrothermal deposition of MoS2 into TiAl coatings on Ti6Al4V alloy

Antifriction layers on the Ti6Al4V alloy were obtained by creating a developed structure of lubricant pockets with dry self-lubricating substances. In this work, the structure and tribological behavior of TiAl intermetallic coatings after hydrothermal deposition of MoS 2 were studied. Coatings of titanium aluminides with a regular crack network were obtained by a Ti6Al4V alloy electrospark treatment in an equimolar mixture of titanium and aluminum granules . The etching in HF solutions significantly increases the crack width (from 0.77 to 4.8 μm). The liquid-phase hydrothermal synthesis was used to fill the cracks acting lubricant pockets in the coatings with MoS 2 . It was shown that a molybdenum disulfide layer consisting of spherical particles with a diameter of 3.09 ± 0.63 μm formed on the surface of the samples filling the cracks as a result of hydrothermal synthesis. The results of tribotechnical tests showed that the hydrothermal deposition of MoS 2 on TiAl coatings reduces their friction coefficient to 0.29 and the wear rate by 5.4 times. Cu-plating protects TiAl-layer during etching, increasing the capacity of lubricant pockets. Such treatment reduces wear rate and friction coefficient to 0.17. Lubricant working lifetime was 61 times longer on Cu-plated and etched TiAl coating than on Ti6Al4V polished surface. Studies have shown the promise of hydrothermal deposition of MoS 2 on the Cu-plated and etched TiAl coatings to improve tribological properties of the Ti6Al4V alloy. • TiAl/MoS 2 coating was prepared by ESD, Cu-plating, etching and hydrothermal coat. • The etching by HF acid converts the TiAl coating cracks into lubricant pockets. • The MoS2 presents in etched TiAl coating cracks after hydrothermal treatment. • The etching and MoS 2 deposition reduce COF of the TiAl coating from 0.97 to 0.29. • Cu-plating before etching increase the lubricant lifetime of TiAl/MoS 2 coating.

The Influence of the Working Conditions of the Electrospark Granules Deposition on the Formation of Cracks in Ti-Al Intermetallic Coatings

Electrospark treatment of a titanium alloy Ti6Al4V in a mixture of granules allows the formation of intermetallic Ti-Al coatings. The coating structure is penetrated by a network of cracks with a thickness of 0.46 to 1.19 microns and a specific area of 1.5 to 3.4%. A change in the ratio of Ti to Al in the mixture of granules does not lead to a monotonic change in the thickness and number of cracks. A decrease in the pulse duration from 200 to 20 μs leads to a slight decrease in the thickness of cracks and significantly increases their total area from 2.1 to 3.4%. An increase in the discharge pulse repetition rate can significantly increase the thickness of cracks in Ti-Al electrospark coatings.

Deposition of tantalum carbide on Ti6Al4V alloy by electric discharge treatment

Titanium alloys attract wide attention of researchers due to the unique combination of low density, high strength, corrosion resistance, biocompatibility, etc. Therefore, the study of new methods for processing titanium and the creation of protective coatings seems relevant. Metal-ceramic coatings were obtained by electrospark treatment of a titanium alloy Ti6Al4V in a mixture of titanium granules with tantalum carbide powder. Three mixtures of granules were prepared with a TaC content of 2.4; 4.6 and 6.7 vol.%. Coatings were deposited by rectangular pulses with an energy of 0.33 J and a frequency of 1 kHz for 8 minutes in an argon stream. The increase of the volume fraction of tantalum carbide powder in the mixture of granules from 2.4 to 6.7 vol.% does not lead to a significant increase in cathode gain. The average coating thickness ranged from 29 to 36 microns. Using scanning microscopy and energy dispersive analysis methods, it was found that the coating structure is represented by a metal Ti – Ta – C matrix with large ceramic grains. According to x-ray phase analysis, it was found that tantalum carbide TaC prevails in the coating composition. It content increases with increasing powder concentration in the mixture of granules. In addition to it, there are phases of titanium carbide and tantalum subcarbibide TaC0.6, which are the products of TaC decarburization during its interaction with the titanium melt. With an increase of the tantalum carbide concentration in the mixture of granules, the hardness of TaC/Ti coatings increased from 6.1 to 8.9 GPa, which is 2–3 times higher than that of the Ti6Al4V alloy. Coefficient of friction of coatings was in the range of 0.5–0.9. Dry sliding wear tests showed that TaC/Ti coatings had a wear rate ranging from 0.1·10–5 mm3/Nm to 1.7·10–5 mm3/Nm. Thus, the use of these coatings makes it possible to increase the wear resistance of the Ti6Al4V alloy up to 128 times.