Electro-spark Deposition Method Research Articles

Износостойкость и коррозионное поведение Cu-Ti-покрытий в растворе SBF

Introduction. Currently, titanium and its alloys have become the most popular metal implantable biomaterials. However, the main disadvantage of titanium alloys is low wear resistance due to high viscosity. It is known that copper-titanium coatings effectively improve the antibacterial properties of titanium alloy and at the same time increase its wear resistance. Purpose of the work is to study the effects of a solution simulating body fluid on corrosion properties, friction coefficient and the wear of copper-titanium coatings obtained by electrospark deposition method of the Ti-6Al-4V alloy. Method. A non-localized electrode consisting of copper and titanium granules in various ratios was used to form copper-titanium coatings on a titanium alloy by electrospark deposition. The structure of the coatings was examined using a DRON-7 X-ray diffractometer in Cu-Kα radiation and an X-max 80 energy dispersive spectrometer. The antibacterial activity of the deposited Cu-Ti coatings was studied on a non-pathogenic gram-negative culture of Escherichia coli. Polarization tests in SBF solution were carried out using a P-40X potentiostat with an impedance measurement module. The metal content in the SBF solution after immersion of the samples was measured using an ICP-MS 2000 mass spectrometer. The tribological characteristics of the coatings according to the ASTM G99-17 standard using the “ball-on-disk” scheme with sliding friction in the SBF solution at loads of 10 and 25 N were examined. Results and discussions. It is shown that the bactericidal activity of Cu-Ti coated samples to a non-pathogenic culture of Escherichia coli increased monotonously with an increase in copper content. With copper concentration increasing, the corrosion current density of the coatings increased from 3.455 to 17.570 μA/cm2. It is shown that the SBF solution accelerates the wear of a titanium alloy many times over due to its interaction with the electrolyte via the oxidative wear mechanism. The use of Cu-Ti coatings allows reducing the friction coefficient and greatly decreasing the wear of Ti-6Al-4V alloy in the presence of an electrolyte.

INVESTIGATION OF CORROSION BEHAVIOR OF AISI 304 AND AISI 316L STAINLESS STEELS COATED WITH FeAL AND NiAL INTERMETALLICS USING ELECTRO-SPARK DEPOSITION METHOD

Due to their superior corrosion resistance at high temperatures, stainless steels have a wide range of applications in numerous industries (including chemistry, the petrochemical industry, the paper industry, and nuclear engineering), it is also utilized in the medical industry as an implant material. To enhance the outstanding qualities of stainless steel such as high temperature corrosion, surface coating methods are also used. Boronizing, nitriding, thermal spray coating, physical vapor deposition, chemical vapor deposition, and electro-spark deposition procedures are used to apply these coating processes to steel surfaces. The electro-spark deposition (ESD) coating technology is one of the most promising approaches in this area. Using high-frequency and high-current electric pulses, the ESD micro-welding procedure bonds electrode material to the surface of a metallic substrate. In this study, AISI 304 and AISI 316L stainless steels were coated with FeAl and NiAl intermetallics using the ESD method. First, suitable experimental parameters for ESD coating were established. Second, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the microstructures and phases that formed on the coated surfaces. Then, the surface hardness of the resulting layers was determined. Finally, the corrosion properties of intermetallic-coated stainless steels were determined using electrochemical methods and compared with each other. As a result, both the hardness values and corrosion resistances of both stainless steel sheets have increased with intermetallic coatings.

Study on the effect of the crack closing of AlCoCrFeMnNi high entropy alloy electro-spark deposited coating by plasma nitriding on the corrosion resistance

The formation of cracks and porosities in the hard coatings is inevitable within the coating applied through the electro-spark deposition (ESD) method. However, applying post-treatment surface modification to alter and control surface defects is an effective method. In this study, the AlCoCrFeMnNi high entropy coating was applied to the structural steel using the electro-spark deposition method, followed by plasma nitriding at 550 °C. The results of the microstructural studies conducted using field emission scanning electron microscopy, showed that closing the cracks and porosities leaded to smoother surface. To evaluate the corrosion resistance, polarization and electrochemical impedance spectroscopy (EIS) were conducted in a 3.5 wt% NaCl solution at room temperature. Results showed that applying a plasma nitriding alters the crack network on the surface of the AlCoCrFeNiMn hard coating, which significantly increased the corrosion resistance of HEA coating. Additionally, the formation of the nitride phases on the surface of the coated layers caused the formation of the galvanic cells of nitride/oxides and reduced the corrosion rate of the samples after plasma nitriding; however, localized corrosion especially pitting corrosion occurred. Repairing the cracks network, formation of nitride phases and increasing the lattice distortion are three main outcomes of the diffusion of nitrogen that contribute to improve the corrosion resistance.

Characterization of Tin Bronze Substrates Coated by Ag + B83 through Electro-Spark Deposition Method

Characterization of Tin Bronze Substrates Coated by Ag + B83 through Electro-Spark Deposition Method

Economic Efficiency of High-Entropy Alloy Corrosion-Resistant Coatings Designed for Geothermal Turbine Blades: A Case Study

The aim of this paper is to establish the cost-effectiveness of high-entropy alloy coatings, using the electrospark deposition technique, designed for a geothermal turbine blade’s leading edge. The deposition of materials with high resistance to corrosion and erosion aims to increase the blade’s service life, reduce maintenance costs and improve production efficiency. According to our previous research on the CoCrFeNiMox high-entropy alloy system, the results showed a high corrosion resistance when in bulk or as a coating, and when tested in geothermal steam and in a saline solution. Based on the results, the high-entropy alloy was subjected to further analyses. The paper focused on two aspects of the research. The first direction was to explore the possibility of obtaining an effective, protective high-entropy alloy layer by the electrospark deposition method. To this end, various tests were performed to demonstrate that the new material possesses superior properties and is suitable for the geothermal environment’s demands. The second direction was to calculate the economic efficiency of coating the areas intensely subjected to wear, based on reports published by the geothermal power plants’ representatives. The final costs were compared with the commercially available equipment parts, and also with the general maintenance costs. From the calculation of the cost efficiency for the CoCrFeNiMo0.85 high-entropy alloy, it resulted that the deposition method and the properties of the material are suitable for the operating conditions, representing an efficient and easy to apply solution to reduce maintenance costs in the geothermal industry.

A Mechatronic System Design for The Coating of WC on Stainless Steel Using Electro Spark Deposition Method

Günümüzde Elektro Kıvılcım Biriktirme (EKB) sistemleri ile yapılan uygulamaların otomotiv, kimya, uzay, tıp, gıda ve askeri alanlardaki kullanımı giderek artmaktadır. Bununla birlikte EKB ile kaplama işlemleri manuel olarak yapılmakta ve bunun için el kuvveti ve becerisi kullanılmaktadır. Bu sebeple, kaplama sistemlerinin otomatik olarak yapılabilmesi için kontrol teknolojisi ekipmanları ile donatılması ve çeşitli yardımcı sistemlerle birlikte kullanılmasının gerekliliği ortaya çıkmaktadır. Bu çalışmada, Elektro Kıvılcım Biriktirme yöntemi kullanılarak paslanmaz çelik üzerine otomatik kaplama yapmak için çok eksenli bir Mekatronik sistem tasarımı uygulanmıştır. Ayrıca bu sistem için iki farklı yardımcı tasarım belirlenerek üretilmiştir. Bunlar; Z ekseninde yay geri beslemeli kaplama sistemi ve ağırlık dengesi kontrollü kuvvet ölçüm geri besleme sistemleridir. Geliştirilen sistemde AISI 304 paslanmaz çelik yüzeyine volfram karbür (WC) kaplaması gerçekleştirilmiştir. Paslanmaz çeliğin kaplanması sırasında bilgisayar kontrollü olarak 100 µF, 80V ve 80 Hz olarak belirlenen parametrede, P:50, I:1.2, D:0,6 PID değerlerinde üç farklı kaplama deseninde otomatik kaplama işlemi gerçekleştirmiştir. Çalışma sonucunda ağırlık-denge analizleri ile mikro ve makro yapı analizleri yapılmıştır. Çalışmalar sonucunda paslanmaz çelik yüzeyinde istenilen 100 gram ağırlık kuvvet hassasiyetinde kaplamanın otomatik olarak yapıldığı gözlemlenmiştir. Manuel kaplamaya göre sürekli zamanda daha fazla kaplama işleminin otomatik olarak yapıldığı ve birim zamanda daha fazla verim sağlandığı sonucuna varılmıştır.

High-temperature oxidation resistance of NiCrAlY columnar microcrystalline coating deposited by EDS

In this paper, the NiCrAlY coating is deposited on the surface of the NiCrAlY alloy substrate by the electrospark deposition method. The phase composition, morphology and element composition of the substrate and coating were characterized by XRD, SEM/EDS. The high-temperature oxidation resistance was tested. The results show that the weight gain of the coating is lower than that of the substrate alloy after high-temperature oxidation. The coating protects the substrate to some extent. And because of the formation of NiCrAlY columnar microcrystalline coating, rich grain boundaries, promoted the diffusion rate of metal ions, resulting in the formation of “pinning effect” of the film/metal interface, improve the anti-stripping performance of the coating.

Formation of Al2O3/MoS2 nanocomposite coatings by the use of electro spark deposition and oxidation

Grade 5 titanium is the most widely used titanium alloy, but it has low tensile and shear strength. Therefore, it is expected to have a high coefficient of friction, limiting the use of this alloy. In this study, to improve the properties of grade 5 titanium, Al2O3/MoS2 nanocomposite coating was applied to it using electro spark deposition method and further oxidation of Al/MoS2 coating. The coating operation was performed in the conditions of 5, 8, and 11 kHz frequencies, 15, 25, and 35 amps current limits, and 50, 60, and 70% duty cycles. XRD and SEM analysis were used to examine the structure of the coating. Examination of the electrode showed that the electrode contained high amounts of aluminum along with molybdenum disulfide dispersed in between. The results showed that Al2O3/MoS2 nanocomposite was formed on the substrate. The calculated minimum and maximum spark energies were 0.75 and 8.63 J, respectively. The maximum spark energy is related to the duty cycle of 70%, frequency of 11 Hz, and the current limit of 35 amps. The lowest efficiency of the coating process was 14.29%, and the highest efficiency was 75.86%. The highest efficiency is related to the duty cycle of 60%, frequency of 11 Hz and current limit of 25 amps. The sample had the highest thickness with a value of 21.3 μm, and the sample had the lowest thickness with a value of 2.3 μm. The highest thickness of the coating is related to the duty cycle of 70%, frequency of 5 Hz, and the current limit of 25 amps.

The Ceramic Composite Coating (TiC+TiB2) by ESD on Ti6AL4V Alloy and Its Characterization

Titanium based alloys or materials used for mechanical and constructional purposes can exhibit high corrosion and abrasion resistance with coatings made on their surfaces. In this study, the surface of Ti6Al4V plate substrate was coated with TiC+TiB2 composite electrodes at different volts and frequencies by Electro-Spark Deposition (ESD) method. The ESD method is a micro arc welding method that allows deposits of alloys and ceramics compounds that have electrical conductivity on the surface of metallic materials, with the plasma that brings about a better melting of base metal and electrode for producing good adhesion between the coating and base metal. In this study, the Ti6Al4V samples were coated with TiC+TiB2 electrodes, and the precoating, post-coating hardnesses, wear rates and coating layer thicknesses of the samples were examined. TiC + TiB2 composite coating on the surface of Ti6Al4V alloys by ESD method was achieved and the hardness increase was observed with the help of numerous hard ceramic phases.

Biocompatibility assessments of 316L stainless steel substrates coated by Fe-based bulk metallic glass through electro-spark deposition method

Metallic materials made of rather precious alloys are widely used in orthopedic surgery, circulatory system, and dentistry fields. Stainless steel coated by alloys with a variety of physiochemical properties can be an excellent candidate for making economical devices with superior biomedical compatibility. In this study, a Fe- based metallic glass alloy was applied on 316L stainless steel (316L SS) using the electro-spark deposition (ESD) method as an economic and easy handling method. The coated samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and atomic force microscopy (AFM). It was found that a metallic glass coating was uniformly formed on the stainless steel substrate. Cytocompatibility (MTT assay), hemocompatibility, and cell attachment assays of the fabricated biomaterials were carried out using bone and connective tissue cell lines. The samples with optimized coating were shown to exert lower cytotoxicity, better cell attachment, and higher blood compatibility than the stainless steel substrates.

Fabrication, microstructural characterization and mechanical properties evaluation of Ti/TiB/TiB2 composite coatings deposited on Ti6Al4V alloy by electro-spark deposition method

In this study, briquettes of Ti–TiB–TiB2 composite were produced by mixing Ti and B powders, performing self-propagating high-temperature synthesis process and by applying hydrostatic pressure on the reaction products with a high-capacity press. Ti–TiB–TiB2 was then coated to Ti6Al4V substrate by Electro-Spark Deposition (ESD) technique under two atmospheres of air and argon, single and double-layer coatings and in two energy levels of 40 W and 110 W as input powers. Coatings microstructure were examined by Scanning Electron Microscope (SEM) equipped with Energy Dispersive Spectroscopy (EDS) analyzer. Comparison of the coatings microstructure with the electrode microstructure shows that the coatings have a much finer microstructure than that of the electrode due mainly to the high solidification rate in the ESD process. Microstructural observations also revealed that the main phases in the coatings are needle-shaped TiB and particle-shaped TiB2 in the Ti matrix. The coating microstructure was much finer due to an increase in solidification rate by reducing the input power from 110 to 40 W. In such a situation, two phases of TiB2 and TiB with nanometer sizes were scattered in the Ti matrix. Also, due to the trapping of the gases in low input power of 40 W, a limited number of very small gas pores was created in the microstructure. Interface examination of the coating and the substrate by the Line Scan and X-ray Image show a good coherence of the coating with the substrate. Adhesion results showed that the bond strength between the coating and the substrate was higher than 50 MPa in all coatings. No crack was observed in the coatings after bending tests which were performed, in accordance with the intended standard, on the samples around a mandrel. The hardness of all coatings was increased with decreasing the input energy from 110 to 40 W.

Investigation of Wear and Corrosion Behaviour of AISI 316 L Stainless Steel Coated By ESD Surface Modification

AISI 316 L austenitic stainless steel is widely used in various sectors of the industry (chemical, petro-chemical industry, paper industry, nuclear engineering, dairy equipment and medical field) because of its good corrosion resistance and biocompatibility. In contrast to these superior properties, it has a low hardness and poor wear performance, thus, limiting its use in some areas of industry. As a result of progress in science and technology, the expectation of superior properties from materials has increased and the surface modification has become an important part of this development. Amongst many coating processes, Electro-spark Deposition (ESD) is a micro-bonding process that is used to deposit a stronger, more robust and durable coating layer on a metallic substrate. This method can also be used to repair damaged parts, tools or equipment or to extend the tool and equipment life. In this study, the surface of AISI 316 L stainless steel was coated with WC and Ti6Al4V by ESD method. Morphology and microstructure of the deposited layers were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Surface hardness distributions were determined with a micro hardness tester. XRD analysis revealed that Fe–α, Fe–γ, W2C, Cr–Ti, Al–Fe–Ti phases exist on the deposited layers. The wear behavior of the coated surfaces was carried out by ball-on-disc wear method using WC-Co ball bearing with a diameter of 8 mm for a sliding distance of 250 meters at a sliding rate of 0.3 m/s under a dry condition using a load of 5 N. Corrosion behavior of coated surfaces i.e. Tafel extrapolation and linear polarization methods were investigated for the duration of 1 h in the SBF (Simule Body Fluid) solution. Morphology of layers formed on steel surface was examined by SEM microscope. Wear tests showed that AISI 316 L stainless steel has a low surface hardness but wear resistant coatings improved this property. The wear rate of coated AISI 316 L stainless steel decreased by 3–10 times with respect to the type of coating. The electrochemical experiments showed that the expected improvement was not achieved due to the high corrosion resistance of AISI 316 L stainless steel. However, the weakness of the surface hardness was partly replaced by an acceptable compromise from corrosion resistance.

Comparative study of coatings obtained by ESD method using TiC–NiCr and TiC–NiCr–Eu2O3 electrodes

The study covers coatings obtained on 40Kh steel substrates by electro-spark deposition (ESD) using TiC–NiCr and TiC–NiCr– Eu2O3 electrodes. Coatings were deposited by the Alier-Metal 303 unit in argon environment under the normal pressure using direct and opposite polarity. The structure, elemental and phase composition of electrodes and coatings were studied using X-ray phase analysis, scanning electron microscopy, energy dispersive spectroscopy, glow discharge optical emission spectroscopy, and optical profilometry. Mechanical and tribological properties of coatings were determined by nanoindentation and testing according to the «pin-disk» scheme including high-temperature conditions in the range of 20–500 °C. The tests conducted include abrasive wear tests using the Calowear tester, impact resistance tests using the CemeCon impact tester, and tests for gas and electrochemical corrosion resistance. Test results showed that electrodes contain titanium carbide, nickel-chromium solid solution, and europium oxide in case of a doped sample. Coatings exhibit the same phase composition but solid solution is formed on the iron base. Coatings with the Eu2O3 additive do not differ significantly in structural characteristics, hardness, friction coefficient, and exceed the base coatings in terms of their abrasive resistance, repeated impact resistance, heat and corrosion resistance. There was an increase in impact resistance by 1.2–2.0 times, a decrease in corrosion current by more than 20 times, and an oxidation index by almost 2 times during the transition to doped coatings.

Wear Behavior of Pure Titanium Coated With WC-Co by the Use of Electrospark Deposition Method

Titanium is a highly interesting material in engineering because of its unique combination of high strength to weight ratio, excellent resistance to corrosion, and biocompatibility. However, the material’s low wear resistance, which is its inherent nature, limits its application in highly erosive conditions. In order to enhance the wear resistance of biomedical grade titanium with the help of a WC-Co coating, an electrospark deposition method was used in this work. The goal of this work is to investigate the effect of frequency and current upper limit in the electrospark deposition process on substrate properties. Hardness of the layers was measured by a microhardness tester. In order to study the morphology and microstructure of surface layers, scanning electron microscope was used. Tribological tests were conducted under technically dry friction conditions at a load of 12.5 N by a pin-on-disk tribometer. Titanium was observed in coating and metallurgical bonding between the coating and the substrate. The optimized sample's hardness was about 930 HV 0.1. Results showed that the presence of a carbide layer on the surface of titanium leads to a great enhancement of wear resistance of about 68% in the pin-on-disk test.

Characterization and bioactivity of hydroxyapatite-based coatings formed on steel by electro-spark deposition and micro-arc oxidation

The hydroxyapatite (HA); a bioactive and biocompatible; was formed on steel by electro-spark deposition (ESD) and micro-arc oxidation (MAO). At the first stage, Ti6Al4V alloy was coated on steel by ESD method under argon atmosphere. And then, the HA-based ceramic coatings were directly fabricated on ESD coated surface by MAO in an aqueous electrolyte containing calcium acetate and β-calcium glycerophosphate-based electrolyte at 30min. The phase structure, surface and cross-sectional morphology, surface topography and roughness, wettability, surface and cross-sectional elemental composition and functional groups of the coatings were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), surface profilometer, contact angle goniometer (CAG), energy dispersive spectroscopy (EDX-Mapping) and Fourier transformed infrared spectroscopy (FTIR), respectively. The highly crystalline HA structure was detected on ESD+MAO surface. The HA-based surface was rough and porous due to the existence of micro discharge channels through MAO. The elements such as Ca and P in the structure of HA were homogeneously distributed over the whole surface. The HA-based duplex coating had a low contact angle indicated a hydrophilic character due to the existence of porous and rough structure on the surface. The bioactivity of HA-based coatings was carried out by immersion test in simulated body fluid (SBF) at body temperatures up to 14days. After 14days, the HA-based surface was uniformly covered by secondary apatite structure. The HA-based coating on steel significantly contributed improving bioactivity.

Quality Surface Modification for Refractory Stainless Steel by Tungsten Deposition, Using Electro-Spark Deposition Method

In this paper were analyzed Tungsten electrode depositions using electro-spark deposition method, on stainless steel, used for hydraulic turbine vanes and blades of mixing blades for chemical industry, in order to achieve an improved wear resistance. This deposition method was chosen due to its relatively low cost, easy to achieve, and leads to obtaining thin layers with good adherence to the substrate, and with different thicknesses, depending on the number of deposited layers. The chosen electrode is an alpha character element and generates an increase of the mechanical properties at low and high temperatures for austenitic stainless steels. Tungsten does not modify the corrosion resistance for the stainless steels. The samples were analyzed on scanning electrons microscope (SEM) and also the chemical analysis (EDX) for distinguish the layer-support structure and the elements repartition on the surface and in line.

Interface behavior of tungsten coating on stainless steel by electro spark deposition

A new method of electro spark deposition method was put forward, which was based on the theory of electro spark deposition by changing the polarity in the liquid. Tungsten coating layers was produced on surface of Stainless Steel by electro spark deposition. The micro hardness, microstructure, chemical composition and phases of the coating layer were examined by means of hardness test, scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) analysis. The results showed that there was tungsten coating in the surface, which was discontinuous. Microhardness of the coating layer was about 3 times more than that of the substrate. The combination between coating layer and substrate was metallurgical bond.

Characterization and mechanical properties of the duplex coatings produced on steel by electro-spark deposition and micro-arc oxidation

In this study, the ESD (electro-spark deposition) and the MAO (micro-arc oxidation) processes were used to improve the mechanical properties and the tribological performance of steel. This study has focused on forming a duplex surface coating on the steel. The ESD method was carried out a titanium alloy (Ti6Al4V) deposit layer on the steel substrates at the first step, and then the MAO process was employed to improve properties of the titanium alloyed layer at the second step. Phase structure, surface morphology, elemental composition, hardness, adhesion strength and tribological property of the ESD and the ESD+MAO coating (the duplex coating) were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDX), micro Vickers tester, micro scratch tester and tribometer, respectively. The XRD results indicated that the duplex coating consists of α-Al2O3 (corundum) and γ-Al2O3 phases while AlFe3, TiN and AlTi3 phases were detected in the ESD coating. The hardness of the duplex coating was significantly improved compared to the uncoated steel and the ESD coating. The adhesion strength of the duplex coating was greater than the ESD coating due to the existence of high hardness and high thickness. In addition, the tribological properties of the ESD and the duplex coatings were significantly improved with compared to the uncoated steel.

Researches Regarding Ti/W/TiC Triple Layers Deposition on the Ferritic-Pearlitic Cast Iron Support, Obtained by Electro-Spark Deposition Method

This paper contains a layer characteristics analysis layer thickness, chemical analysis, surface quality-for the triple deposition with Ti, W and TiC on the ferritic-perlitic cast iron support, using electro-spark deposition method. The resulted surface quality by electro-spark deposition method is dependent by the quality and chemical composition of the electrode. The obtained layer was realized by multiple successive depositions, using different electrodes to combine the beneficial characteristics of the part surface with the appropriate succession.