Electrospark Deposition Technique Research Articles

Electrospark Cu[sbnd]Ti coatings on titanium alloy Ti6Al4V: Corrosion and wear properties

Nowadays, copper-titanium coatings have invited extensive attention from researchers in the surface modification of industrial and biomedical materials due to their excellent mechanical properties and biocompatibility. The electrospark deposition technique was used for CuTi coatings deposition on the Ti6Al4V alloy by processing in a mixture of copper and titanium granules at a copper concentration from 10 to 90 at.%. For the first time, electrospark CuTi coatings with a wide range of copper and titanium ratios are obtained on Ti6Al4V titanium alloy. It is revealed that both cathode mass gain and coatings thickness rise with the copper concentration increase in the mixture of granules. According to EDS analysis, the copper concentration in the coating linearly grew with a growth of its content in the mixture of granules. According to the data of X-ray analysis, intermetallic compounds were found in the structure of the coatings: CuTi3, CuTi, Cu4Ti3, and Cu3Ti. Detected phases provide the coating microhardness up to 6.7 GPa. Polarization tests in 3.5 % NaCl solution showed corrosion resistance growth with a copper content decrease in CuTi coatings. The oxidation resistance at a temperature of 900 °C grows with an increasing copper concentration in the coating structure. Cu-enriched sublayer is formed on upper layers of Ti6Al4V alloy after CuTi coating oxidation at 900 °C. The wear rate of the coated samples as a function of copper concentration had the form of a parabola, with a minimum for the coating made in an equimolar mixture of copper and titanium. The use of electrospark CuTi coatings makes it possible to increase the wear resistance of the Ti6Al4V alloy surface up to 11 times.

Technique for Comprehensive Assessment of the Quality of Coatings Synthesized by Electrospark Deposition Technique

Technique for Comprehensive Assessment of the Quality of Coatings Synthesized by Electrospark Deposition Technique

Advancements in Electrospark Deposition (ESD) Technique: A Short Review

The need to use components with improved surface characteristics in relation to severe operating conditions, together with the aim of cost reduction associated with the replacement of damaged components, has led to an increasing use of coatings and repairing processes. The most common deposition processes are generally characterized by high equipment costs and, sometimes, by long deposition time. Furthermore, some repair technologies, especially those characterized by high heat input, are not suitable for alloys used in aerospace applications due to the degradation of their mechanical characteristics. In the last decades, a novel eco-friendly method capable of overcoming the limits set out above emerged: the electrospark deposition (ESD) technology. Thanks to its efficiency, simplicity, cost-effectiveness, and low heat input, this technology has proved to be suitable both for improving surface properties, such as thermo and wear resistance, higher hardness and corrosion resistance, and for the repair of high-value components. The aim of this review is to describe in detail some aspects of the ESD technique to understand the ESD processing preparation of alloys normally considered difficult to weld by traditional processes and to give some important clues to the readers to contribute to the defect-free repair of damaged areas and coatings deposition.

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.

Tribological properties of electrospark depositing Ni-WS2 self-lubricating coating

A Ni-WS2 sintered electrode was used to prepare a coating on a CrNi3MoVA steel substrate by employing electrospark deposition technique. The nanomechanical and tribological properties of the coating were tested by using nanoindenter and tribometer, and the morphologies, composition and phase structure were obtained by utilizing scanning electron microscopy (SEM), energy dispersive X-ray spectrum (EDS) and X-ray diffraction(XRD). The results showed that the coating is even-distributed with nanostalline α-W strengthening phase dopants, and it has a strong metallurgical bonding with the substrate. The coating is composed of WS2, γ-Ni, α-W and Ni3S2 phases, and it exhibits outstanding tribological properties for its friction coefficient reduced about 79% and wear rate reduced about 96% in contrast to the CrNi3MoVA steel.

Investigation on Wear Behavior of Steels Coated with WC by ESD Technique

Electro-spark deposition (ESD) or low energy welding (LEW) technique allows the coating of metallic materials with different metal and alloys, conductive ceramics and conductive ceramic metal composites. It is also known as micro-joining process to improve the wear properties of the substrate or to obtain a more durable upper superficial coating. In this study, the surfaces of AISI 1040, AISI 4140 and AISI 5140 steels were coated with WC electrode at constant rotational speed and then characterized by a metallographic study. A homogeneous coating thickness was observed in microscopy studies and the formation of W2C phase in the coating layer was determined in XRD analysis. Hardness of WC coated samples increased approximately 5 times. Abrasion tests were carried out by ball-on disc method with WC–Co ball at 250 m under 5N load. In the abrasion tests with WC–Co ball, the best abrasion resistance is obtained with WC coated AISI 5140 steel, while the lowest strength is obtained with uncoated AISI 4140 steel.

Phase Evolution and Microstructure Analysis of CoCrFeNiMo High-Entropy Alloy for Electro-Spark-Deposited Coatings for Geothermal Environment

In this work, a CoCrFeNiMo high-entropy alloy (HEA) material was prepared by the vacuum arc melting (VAM) method and used for electro-spark deposition (ESD). The purpose of this study was to investigate the phase evolution and microstructure of the CoCrFeNiMo HEA as as-cast and electro-spark-deposited (ESD) coating to assess its suitability for corrosvie environments encountered in geothermal energy production. The composition, morphology, and structure of the bulk material and the coating were analyzed using scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The hardness of the bulk material was measured to access the mechanical properties when preselecting the composition to be pursued for the ESD coating technique. For the same purpose, electrochemical corrosion tests were performed in a 3.5 wt.% NaCl solution on the bulk material. The results showed the VAM CoCrFeNiMo HEA material had high hardness (593 HV) and low corrosion rates (0.0072 mm/year), which is promising for the high wear and corrosion resistance needed in the harsh geothermal environment. The results from the phase evolution, chemical composition, and microstructural analysis showed an adherent and dense coating with the ESD technique, but with some variance in the distribution of elements in the coating. The crystal structure of the as-cast electrode CoCrFeNiMo material was identified as face centered cubic with XRD, but additional BCC and potentially σ phase was formed for the CoCrFeNiMo coating.

Badania wpływu obróbki wibrościernej na warstwy nanoszone techniką ESD

The article presents the proposal of using abrasive treatment in vibrating containers for surface treatment applied with the Electro Spark Deposition technique. In tests on a carbon steel the layer was applied with a tungsten electrode. After the tungsten layers were applied, a vibro-abrasive treatment was carried out. Changes in the geometrical structure of the surface of the deposited layers before and after vibratory processing were investigated. In addition, the chemical composition and the thickness of the coatings were examined.

Surface Modification of 304 Stainless Steel by Electro-Spark Deposition

Electro-spark deposition (ESD) is a pulsed microwelding process that is used to apply surface coatings for the repair of damaged high value and precision products or modify their surfaces for specific properties. The low heat input, minimal heat-affected zone and the ability to form metallurgical bonding of coating to substrate are major advantages of the ESD process. Many applications require the components to have excellent surface performance, such as wear and corrosion resistance. ESD technique provides an approach to modify the component surface without compromising the bulk properties. In this study, surface modifications of 304 stainless steel by ESD were investigated. Titanium carbide (TiC), tungsten carbide (WC) and molybdenum (Mo) were employed as coating materials. Scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX) analysis were conducted to characterize the microstructure and composition of the coatings. The coatings thicknesses were all around 40 µm. The results showed that TiC and WC coatings showed a dramatic increase in the microhardness, up to 5 times. WC coating improved the wear resistance by more than 5 times, while TiC and Mo coatings also improved it by approximately 2.5 times. Electro-chemical tests were conducted to investigate the corrosion resistance of the coatings. Mo coating exhibited a significant improvement in the corrosion resistance in 5% NaCl solutions, corroding 350 times slower than stainless steel. Synchrotron x-ray diffraction was performed to investigate the microstructure changes of the Mo-coated sample. Heat treatment was also carried out to investigate the corrosion behavior of Mo-coated 304 stainless steel at elevated service temperature in air or argon.

Properties of NiCrAlY coatings fabricated on superalloy GH4169 by electrospark deposition

NiCrAlY coatings were deposited on superalloy GH4169 by electrospark deposition technique. Influences of the depositing parameters (100 V/40 μF, 100 V/80 μF, 100 V/120 μF, 150 V/40 μF, 150 V/80 μF, 150 V/120 μF) on the microstructure and the properties of the coatings were experimentally investigated. Results show that the depositing parameters affect defect density and consequent properties of coatings. The deposition voltage has greater influences on the deposition velocity and on the properties of the coatings than the deposition capacity. The weight gain per area of the coatings deposited under 150 V increases faster than that under 100 V. The coating deposited under 100 V/40 μF has the minimum defect density and the best properties.

Study of the Direct Metal Deposition of AA2024 by ElectroSpark for Coating and Reparation Scopes

ElectroSpark Deposition (ESD) is a pulsed micro-welding process that is capable of depositing wear and corrosion resistance deposit to repair, improve, and to extend the service life of the components and tools. Major new applications have taken place in gas turbine blades and steam turbine blade protection and repair, and in military, medical, metal-working, and recreational equipment applications. In this study, the ESD technique was exploited to fabricate 2024 aluminum alloy deposit on a similar substrate. The deposits were deposited using different process parameters. Heat input was varied on three levels. The outcoming microstructure was analyzed by optical and scanning electron microscopies. The deposit was characterized by the overlapping of layers with a mixed microstructure. The average hardness was independent from the process parameters. Both porosity inside the deposits and cracks at the deposit/substrate interface were detected. The porosity lowered with the heat input and increased the average length of cracks.

In Situ Synthesis and Characterization of Fe-Based Metallic Glass Coatings by Electrospark Deposition Technique

Crystalline FeWMoCrBC electrode materials were prepared by conventional powder metallurgy. Metallic glass (MG) coatings were produced by electrospark deposition onto AISI 1035 steel in argon atmosphere. X-ray diffraction and scanning electron microscopy verified the amorphous structure of the as-deposited coatings. The coatings have a thickness of about 40 microns and a uniform structure. The results of dry sliding wear tests against high-speed steel demonstrated that Fe-based MG coatings had a lower friction coefficient and more than twice the wear resistance for 20 km sliding distance with respect to AISI 1035 steel. High-temperature oxidation treatment of the metal glass coatings at 1073 K in air for 12 h revealed that the oxidation resistance of the best coating was 36 times higher than that for bare AISI 1035 steel. These findings are expected to broaden the applications of electrospark Fe-based MG as highly protective and anticorrosive coatings for mild steel.

FACILE SYNTHESIS OF Pt-/Pd-MODIFIED NiTi ELECTRODE WITH SUPERIOR ELECTRO-CATALYTIC ACTIVITIES TOWARD METHANOL, ETHANOL AND ETHYLENE GLYCOL OXIDATION

Surface functional modification of NiTi electrode with noble Pt and Pd metal has been successfully carried out by simple and cost effective electro-spark deposition technique (ESD). Thin-film X-ray diffraction (TF-XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and cyclic voltammetry (CV) have been carried out in order to investigate the structure, morphology, chemical composition and electrochemical behavior of the modified electrode surface. The modified Pt/NiTi and Pd/NiTi electrode surface exhibit a circular splash pattern with a tiny amount of Pt ([Formula: see text]5.30 at.% Pt) and Pd ([Formula: see text]5.71 at.% Pd) existence. The electrochemical results demonstrate that the Pt/NiTi and Pd/NiTi electrode possess an improved electro-catalytic activities toward methanol (MeOH), ethanol (EtOH) and ethylene glycol (EG) oxidation in alkaline media in comparison with the bare NiTi electrode. In acidic environments, the Pt/NiTi electrode exhibits even much better catalytic activities than the pure Pt sheet electrode due to the bi-functional mechanism. In the same way, the electro-catalytic activity of the modified Pd/NiTi electrode is also slightly larger than that of the pure Pd sheet electrode in alkaline environment. The electro-spark surface modification approach is rapid and environmentally-benign, being attractive to widen the application of traditional surface modification technique in the field of material surface/interface design and functionalization.

EFFECT OF La2O3 ADDITION ON MICROSTRUCTURE AND WEAR BEHAVIOR OF ELECTROSPARK DEPOSITED Ni-BASED COATINGS

La 2 O 3 doped Ni -based coatings have been prepared by electrospark deposition technique. The effect of La 2 O 3 on the microstructure, hardness and wear behavior of the as-prepared Ni -based coatings is investigated by using X-ray diffractometer, scanning electron microscope, wear tribometer and Vickers hardness tester. Results indicates that the microstructure, hardness and wear resistance of La 2 O 3 doped Ni -based coatings are effectively improved as compared to the undoped one, and the coating with the addition of 2.5 wt.% La 2 O 3 shows the optimal improvement effects. The addition of La 2 O 3 can reduce the defects, refine grains and increase hardness of the coating, which can inhibit the nucleation and propagation of cracking, consequently resist cutting and fracture during the wear process. Moreover, the addition of La 2 O 3 leads to changes in abrasion mechanism of the coatings, and the reasons resulting in different abrasion mechanisms are discussed.

Preparation and characterization of micro-arc-induced Pd/TM(TM = Ni, Co and Ti) catalysts and comparison of their electrocatalytic activities toward ethanol oxidation

Using the electro-spark deposition technique, a novel kind of Pd/TM (TM=Ni, Co and Ti) electrode was successfully prepared by arc-depositing Pd on the transition metal substrates. The structure, morphology and chemical composition of the arc-deposited films were investigated using thin-film X-ray diffraction (TF-XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The results show that, a coarsening topographical morphology can be obtained, being composed of numerous craters/spots with sizes ranging from nano-scales to several microns. The electrochemical measurements indicate that the arc-deposited Pd/TM electrodes exhibit distinct electrochemical behaviors and the catalytic activity toward ethanol electro-oxidation reaction (EOR) is highly dependent upon the nature of substrate. Among the Pd/TM electrodes investigated, the arc-deposited Pd/Co reveals the best activity and superior poisoning tolerance towards ethanol oxidation and will find promising applications as a candidate for the anode catalyst of direct ethanol fuel cells (DEFCs).

Preparation and mechanical properties of two nickel base alloy coatings achieved by electrospark deposition

Ni398 and Ni818 base alloy coatings were deposited on 1045 steel by electrospark deposition technique (ESD). Forming properties, thickness, microhardness and wear resistance of the coatings were investigated. The chemical composition and crosssection morphology were analyzed through energy dispersive spectrum (EDS) and metalloscope. The results show that the technological parameter window of Ni398 is larger than that of Ni818 electrode. However, other properties of the Ni818 coating, such as thickness and microhardness, were better than those of the Ni398 coating. Especially the wornout volume of Ni818 coating is only 1/6 of that for 1045 steel and 1/3 for Ni398 coating. Chemical composition analysis indicated that the addition of Mo promoted grain reflnement of nickel alloy. Metallographic analysis shows that the molten droplets of Ni398 coatings have an average structure thickness of 20{40 „m while the microstructure of Ni818 coatings is ∞at with width of 5{20 „m.

Tribological Behavior of Molybdenum Alloying Layer on H13 Steel by Electrospark Deposition Technique

Molybdenum alloying or modified layer was fabricated on the H13 steel substrate by electronic spark deposition technique (EDS). The microstructure, element distribution and microhardness of the modified layer were analyzed using metalloscope, X-ray diffraction (XRD), Glow Discharge Optical Emission Spectroscopy (GDOES) and microhardness tester, respectively. The modified layer is composed of white layer, diffuse layer and heat affected zone. The interdiffusion between Mo element and other elements in H13 substrate results in Metallurgical bonding. Microhardness of the coating is 1482HK0.025 which is 5 times higher than that of H13 steel base (280HK0.025). The ball-on-disc dry sliding test indicates that the friction coefficient of H13 substrate is decreased obviously by the molybdenum modified layer. The wear mass loss of Mo modified H13 substrate is only one seventh of that of the substrate. The wear resistance of H13 is improved significantly by the Mo modified layer.

Characterisations of electrospark deposition Stellite 6 alloy coating on 316L sealed valve used in nuclear power plant

In nuclear plant the protection of the H2BO4 solution seal areas of AISI 316L austenitic steel is accomplished by Stellite 6 plasma cladding layer. Wear defects created in service required the part to be replaced or repaired. No existing repair technologies were practical. Electrospark deposition (ESD) was to repair defects, enabling the parts to be placed back in service. In this paper the authors report the results obtained depositing directly a layer of Stellite 6 alloy onto a 316L austenitic stainless and Stellite 6 plasma cladding layer by using ESD technique. Electrospark deposition can apply metallurgical bonded coatings without the need of post-heat treatment. Structure, hardness, chemical composition and morphology of the ESD coating have been analysed. By electrochemical measurements it is inferred that the corrosion resistance of the ESD coating is comparable to that of the 316L and Stellite 6 plasma cladding layer. The hardness improvement was ascribed to the refine microstructure and the rapid solidification.

Process and properties of TiC0.7N0.3-based cermet coating deposition on steel by electrospark deposition technique

Process and properties of TiC0.7N0.3-based cermet coating deposition on steel by electrospark deposition technique

Epitaxial MCrAlY coating on a Ni-base superalloy produced by electrospark deposition

A novel electrospark deposition technique has been successfully developed to deposit epitaxially MCrAlY coating onto a directionally solidified nickel base superalloy. The coating is featured by cellular directionally solidified microstructure with primary γ phase. Its formation mechanism may be attributed to the facts that the alloy solidifies primarily with γ phase and solidification conditions of the tiny thin melt close to the limit of constitutional undercooling under the electrospark treatment condition.