Electrospark Deposition Research Articles

PRACTICAL USE OF THE SURFACE LAYERS OF LASER MODIFIED WC-Cu COATINGS

The article presents the study of the effect of laser treatment on the microhardness of WC-Cu coatings applied by electro spark deposition. Observations of friction resistance test results allowed the evaluation of the coatings after laser treatment. The studies were conducted using WC-Cu electrodes, produced by sintering of nanostructural powders. The anti-wear coatings were electro-spark deposited over C45 carbon steel by means of EIL-8A, while the laser processing was performed by electro coats applied using a Nd:YAG, BLS720. Model tests were carried on test mechanical seals for rings made of SiC and WC-Cu coatings before and after laser treatment.

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.

On conditions of bulk and surface glass formation of metallic alloys

Abstract This work is done to analyze the effect of glass forming compounds and melt processing on bulk and surface glass formation. Key factors of glass formation of metallic alloys including structure-phase state of solid precursor (i.e. master-ingot, spun ribbon, powder, etc.) and its melt, conditions of cooling melt and its ability for deep undercooling are considered. A ratio of crystalline glass forming compounds in annealed best BMG compositions is considered to develop a strategy of searching new alloys. Surface glass formation at electro-spark deposition of precursors with high and low GFA used as consumable electrodes is studied. It found that surface glass formation is possible due to both weak and strong chemical interaction of an electrode and a substrate. The former is due to mass transfer of high glass forming ability (GFA) precursor onto metallic substrate with local “drop-by-drop” anode melting stimulated by electric discharge and needs no chemical interaction. The latter goes with diffusion interaction between low GFA precursor and a metallic substrate by a local melting and it is other way to form amorphous surface layer. In both cases the solidification rate of molten drops by electro-spark deposition is enough to suppress crystallization and is compared to melt spinning.

Mechanical Characteristics of Pumimpeller Blades Surface Produced by Electro-Spark Deposition

Surface strengthening technology is an important mean to improve the surface or fatigue performance of material. The metallographic structure and microstructure of the coating were analyzed by electrospark deposition test, the hardness, microstructure and abrasion resistance of the pump blade were tested by selecting and controlling the process parameters. The experimental results manifest that EDM can significantly improve the hardness, wear resistance and corrosion resistance of the blade surface, and reduce the consumption of the underwater environment. In addition, in the case of the same electrical parameters, the thickness of the strengthened layer in the argon atmosphere is slightly lower than that in the air, and strengthened surface roughness is significantly reduced. Hence, the reason may be two aspects, one is due to the protection of argon atmosphere, eliminating the impact of oxidation, the droplet easier to spread in the substrate surface, the other hand is similar to the principle of welding. Consequently, the electrode material in the form of a transition to the workpiece in the form of transition to the surface. Due to the small droplets, it can get a relatively low enhanced surface roughness, which is to improve the reliability and extend the life of the pump is of great significance.

Combustion synthesis of Ti-C-Co-Ca3(PO4)2-Ag-Mg electrodes and their utilization for pulsed electrospark deposition of bioactive coatings having an antibacterial effect

This study aimed to obtain biocompatible ceramic materials in the Ti–C–Co–Ca3(PO4)2–Ag–Mg system in combustion mode. The influence of cobalt additive on the combustion parameters, as well as the structure and properties of the electrode materials, was studied. Compact ceramics consists of a rigid frame of nonstoichiometric titanium (TiC0,5–TiC0,6) carbide grains with titanium phosphate (Ti3PO(x)) phase evenly distributed along the grain boundaries and with local precipitations of calcium oxide (CaO). The addition of cobalt leads to the formation of TiCo intermetallide and a complex CoTiP phase. Introduction of silver and magnesium causes the formation of a silver-based solid solution. Particular attention was devoted to studying the erosive capacity of the electrode materials during the pulsed electrospark deposition (PED) onto a titanium surface. The as-deposited coatings, which were 10μm thick with a roughness Ra=5–6μm, exhibited high mechanical properties, as well as a sufficiently high level of biocompatibility and bioactivity. The silver additive enabled achieving a high antibacterial effect but resulted in a small inhibitory effect of osteoblastic proliferation and differentiation.

Mass transfer trends of AlCoCrFeNi high-entropy alloy coatings on TC11 substrate via electrospark − computer numerical control deposition

A new electrospark deposition (ESD) process, electrospark – computer numerical control deposition (ES-CNCD), was proposed based on an ES-computer integrated deposition system (ES-CIDS). The ES-CIDS integrated a 3-axis CNC milling machine with an ESD welder via a passive exsertile/retractable pattern special deposition holder. The ES-CNCD process employs high-current electrical pulses of short duration to modify the metal surface. In this work, an AlCoCrFeNi high-entropy alloy (HEA) was used as the electrode to prepare HEA coatings on TC11 titanium alloy substrate via weld-spot pattern deposition strategy. Three quantities of cathode mass gain (CMG), anode mass gain (AMG) and material transfer coefficient (MTC) were redefined for ES-CNCD process. The impact of process parameters on CMG, AMG, MTC was investigated via designing orthogonal experiments. The physical mode of mass transfer of ES-CNCD process has been proposed and confirmed by experiments.

Some aspects over the quality of thin films deposited on special steels used in hydraulic blades

The experimental research involved in this paper consists in the obtaining of superior physical, chemical and mechanical properties of stainless steels used in the construction of hydraulic turbine blades. These properties are obtained by deposition of hard thin films in order to improve the wear resistance, increasing the hardness but maintaining the tenacious core of the material. The chosen methods for deposition are electrospark deposition because it has relatively low costs, are easy to obtain, the layers have a good adherence to support and the thickness can be variable in function of the established conditions and the pulsed laser deposition because high quality films can be obtained at nanometric precision. The samples will be prepared for the analysis of the structure using optical method as well as for the obtaining of the optimal roughness for the deposition. The physical, chemical and mechanical properties will be determined after deposition using SEM and EDX, in order to emphasize the structure film-substrate and repartition of the deposition elements on the surface and in transversal section. The non-destructive testing has emphasized the good adherence between deposited layer and the metallic support, due to double deposition, spallation regions doesn't appear.

Analysis of microstructure in electro-spark deposited IN718 superalloy

The microstructure of electro-spark deposited (ESD) superalloy IN718 was studied by the use of scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) techniques. In converse to general assumption, the extremely high cooling rate involved in the ESD process did not produce partitionless solidification that is devoid of second phase microconstituents in the material, nano-sized Laves phase and MC carbide particles were observed within the deposited layer. Notwithstanding the several thermal cycles involved in the process, the extremely low heat input of the process produced a deposited region that is free of the main strengthening phase of the alloy, γ″ phase precipitates, which is in contrast to what have been reported on laser deposition. Nevertheless, application of the standard full heat treatment of the alloy resulted in extensive formation of the γ″ phase precipitates and δ phase precipitates, the most stable secondary phase of the alloy, with nearly, if not complete, dissolution of the Laves phase particles. Furthermore, the XPS analysis done in the study revealed the formation of nano-oxides within the deposited layer, which increased the microhardness of the superalloy in the as-deposited condition and inhibited its grain growth during post-process heat treatment. The microstructure analysis done in this work is crucial to the understanding of properties of the superalloy processed by the ESD technique.

Microstructure and wear resistant performance of TiN/Zr-base amorphous-nanocrystalline composite coatings on titanium alloy by electrospark deposition

Abstract To improve the wear resistance of titanium alloy, especially under high loading friction conditions, TiN/Zr-base amorphous-nanocrystalline composite coatings were prepared by Electrospark Deposition (ESD) on the surface of TC11. The microstructure of the coatings was examined and the fracture toughness and microhardness of the coatings were tested. The wear behavior and mechanism of the coatings under various loading conditions were investigated. The results show that the composite coating consists of two parts, one is a TiN substrate coating (coating I) and the other is Zr-base amorphous-nanocrystalline surface coating (coating II). The former is mainly composed of TiN and Ti 2 N phases while the latter is mainly composed of amorphous phases, within which a large number of nanoparticles exists with diameter between 2 nm and 4 nm. These nanoparticles mainly include CuZr 2 , Ni 2 Zr 3 , and NiZr 2 , etc. The composite coatings are dense and their thickness is approximately ranging from 90 μm to 95 μm, bonding with substrate metallurgically. The fracture toughness of composite coatings is approximately 9.36 MPa m 1/2 . The microhardness of the coating changes in a gradient trend. The average microhardness of coating I and coating II are 1221.5 HV 1.96 and 801.3 HV 1.96 , respectively. The wear tests results show that the composite coatings exhibit excellent wear resistance, especially under high loading friction conditions. The main wear mechanisms of the composite coatings are the micro-cutting wear and the multi-plastic deformation wear under low friction conditions. However, under high loading friction conditions (> 8 N), the main wear mechanism of the composite coatings changed to micro-cutting wear, accompanied with a portion of micro fracture wear. The average wear rate of the composite coating is approximately 1.2–1.5 times of that of the single TiN coating and 2.6–2.7 times of that of the TC11 substrate, respectively.

Wear resistance of electrospark WC–Cо coatings with different iron contents

The work presents the results of investigating the influence of the ion concentration in the WC‒Co electrode materials on the structure and properties of the coatings deposited by electrospark deposition (ESD) on low-carbon steel. It has also been shown that iron concentration affects the character of mass transfer and thickness of the deposited coating. The phase composition, roughness, and wear resistance of the obtained coatings were studied under the conditions of the dry microabrasive rubbing. The increased iron concentration in the electrode materials was found to intensify the decarbidization of tungsten carbide at ESA.

Quality Control of Thin Films Deposited on Special Steels Used in Hydraulic Blades

The hydraulic turbine blades are made from stainless steels having a hard layer for the improvement of the hydro abrasive wear, corrosion resistance, and resistance to mechanical impacts in order to increase the reliability of the turbine. The thin films from stellite and tungsten carbide were obtained by the method: electrospark deposition because it has relatively low costs, are easy to obtain, the layers have a good adherence to support and the thickness can be variable in function of the established conditions. In this paper, the physical, chemical and mechanical properties of the samples will be determined using Scanning Electron Microscope (SEM), in order to emphasize the structure film-substrate and repartition of the deposition elements on the surface and in transversal section. Also, the samples were nondestructively tested using the electromagnetic sensor with metamaterials in order to establish the adherence of the thin films to the steel, proving the potential of this NDT techniques. The complex signal delivered by the sensor has been stored while scanning a 6x6 mm area. The processing algorithm involve the use of the bidimensional Fourier transform after filtering the initial signal using Walsh-Hadamard numerical filter.

Laser welding of niobium to 410 steel with a nickel interlayer produced by electro spark deposition

Some combination of metals such as niobium to stainless steel cannot be joined directly by laser welding due to formation of deleterious phases. On the other hand placement of a narrow strip of a third alloy between the two metals can introduce many technical and availability limitations. In this work, a more versatile method is developed using electrospark deposition (ESD) for facilitation of subsequent Nb to 410 stainless steel dissimilar laser with minimum heat input successfully. The 1mm Nb plate edge was clad by Alloy 82 using a 4mm round electrode by ESD process. The layer has minimum dilution with Nb while having a metallurgical bond. It exhibited a fine cellular structure with Laves phase particles with 30–50nm in diameter. The Nb plate with edge built up was then laser welded to 410 stainless steel using a 1KW fiber laser machine. The presence of the interlayer material suppressed the formation of NbFe intermetallic in the laser fusion zone and increases weldability. Tensile test of dissimilar laser weld with the nickel base ESD interlayer exhibited an ultimate strength of 285MPa with the failure located at the Nb side and not in laser weld metal or at the ESD interface.

Structural transformations in TiC-CaO-Ti3PO(x)-(Ag2Ca) electrodes and biocompatible TiCaPCO(N)-(Ag) coatings during pulsed electrospark deposition

Abstract Thick (up to 30 μm) multicomponent biocompatible coatings with high surface roughness (R a > 6 μm) and hardness up to 11 GPa have been obtained by pulsed electrospark deposition (PED). The surface of Ti substrates (BT1-0 brand mark) was treated using TiC-CaO-Ti 3 PO (x) and TiC-CaO-Ti 3 PO (x) -Ag 2 Ca electrodes obtained by self-propagating high-temperature synthesis from the reaction mixtures of 90%(Ti + 0.5C) + 10%Ca 3 (PO 4 ) 2 and 81%(Ti + 0.5C) + 9% Ca 3 (PO 4 ) 2 + 10% Ag. The Ag was doped into the electrode composition in order to provide the antibacterial activity of the PED coatings. The different contents of O and N in the coatings were achieved through the treatment in various environments: Ar atmosphere, air, or distilled water. The PED was performed at single-discharge energies of 3 and 30 mJ. Depending on the PED mode and processing environments, the coatings with different phase compositions were obtained. Cell proliferation tests showed good biocompatibility of Ag-free and Ag-doped PED coatings with low Ag content. The present paper gives a detailed description of PED process and structural transformations at the tip of electrodes during the PED that affect final coating structure.

Evaluation of three kinds of MCrAlY coatings produced by electrospark deposition

Three kinds of MCrAlY coatings with different aluminum contents (5%, 8%, 12%) were prepared by electrospark deposition (ESD), their microstructure and oxidation behavior were studied by SEM and XRD. The results showed that the phase composition of the coatings changed from single γ-Ni to γ-Ni+β-NiAl hypoeutectic to γ-Ni+β-NiAl hypereutectic with increasing aluminum content, and their solidification morphologies changed from cluster of cellular structure to cellular dendrites to coarse dendrites with secondary arms. When exposed at 1000 °C, the coatings with higher Al content had a stronger tendency to form θ-Al2O3 in the initial several hours. After 100 h of oxidation, a dense and adherent α-Al2O3 scale formed on all of the three coatings but the thickness of α-Al2O3 scale and the amount of remaining θ-Al2O3 increased with increasing Al content. These results revealed different characteristics of ESD MCrAlY coatings which could provide scientific guidance for industrial application.

Fabrication of Nanostructured Coatings

The outstanding thermal, mechanical, electrical and electronic properties of nanocrystalline materials and carbon nanotubes hasattracted considerable research interests, and is now one of the major identifiable activities for material scientists. However, the practical and commercial use of these materials requires efficient processing methods, which needs to be compatible with the existing processes. One of the problems limiting their application is preparation of these materials. Currently, these materials have been prepared in the laboratory by traditional method of compacting the metallic powders which consist of particles at nanoscale. This method has many limitations to achieve properties required at nanoscale. The development of surface nanostructured coatings has been considered as potential industrial application. The nanostructured coatings can be formed by various methods such as physical vapour deposition (PVD), sputtering, chemical vapour deposition (CVD), electrochemical deposition, electrospark deposition. This study has reviewed the formation of nanocoatings by different processes, with emphasis on embedding carbon nanotubes in coating structure.

Conditions for formation of MAX phase Cr2AlC in electrospark coatings deposited onto titanium alloy

Abstract The technique of low-energy pulsed electrospark deposition (PED) with Cr 2 AlC electrodes was used to apply a protective layer onto the surface of Ti substrate. This was done in two ways: (a) thermal treatment of as-deposited coating and (b) preliminary creation of a TiC sublayer followed by PED. Upon annealing at 700 °С for 1 h in air, the coating was found to largely consist of MAX phase Cr 2 AlC. A TiC sublayer preliminary сreated onto the Ti surface was found to suppress the Ti diffusion into the coating and thus to hamper the reaction of Cr 2 AlC with Ti. The coatings were characterized by SEM/EDS, XRD, and XPS. After thermal treatment, the coatings showed high wear resistance and friction coefficients of 0.6 and 0.4 at 25 and 700 °С, respectively.

Characteristics of electrospark deposition of a nickel-based alloy on 410 stainless steel for purpose of facilitating dissimilar metal welding by laser

In this research, a new method is developed using the electrospark deposition (ESD) process for making an interlayer, which could be useful in welding dissimilar metals. Alloy 82 nickel-based alloy was deposited on the edge of a 410-stainless-steel plate and used as an interlayer for subsequent welding to a nickel Alloy 82 plate forming a dissimilar metal weld. Metallographic analysis showed that the ESD layer consisted of a γ phase, columnar grains oriented in {100} direction and cellular solidification morphology with 250–350 nm cell diameter. Neither Lave phase nor large carbide crystals were observed in the microstructure of ESD layer due to the high-cooling rate and the low tendency for segregation. Tensile test exhibited an ultimate strength in excess of 420 MPa, and failure of the joint occurred in the 410 stainless steel base metal indicating good weldability of the ESD interlayer to the base metal.

Feasibility of preparing Mo 2 FeB 2 -based cermet coating by electrospark deposition on high speed steel

Abstract In this study, Mo2FeB2-based cermet coating has been attempted to produce by electrospark deposition (ESD) process on a high speed steel substrate. Microstructural morphology, elementary distribution, phase constitute, microhardness, and wear resistance of the coating were investigated by scanning electron microscopy (SEM), electron probe microanalysis (EPMA), X-ray diffraction (XRD), microhardness measurement and tribological test. The SEM and EPMA results show that the coating is dense, metallurgically bonded to the substrate, and has an average thickness of 48.1 μm. Moreover, a discernible composition transition zone appeared between the coating and the substrate. The XRD patterns reveal a microstructural transformation from Mo2FeB2 phase and binder phase (ferrite) of the cermet to amorphous phase and martensitic phase of the coating during the deposition, and the martensitic phase has nanocrystalline structure (31.7 nm). Such microstructure of the coating results in higher microhardness, lower friction coefficient, and better wear resistance than the high speed steel substrate. The main wear types for the coating are abrasive wear and fatigue wear.

Impact of CrSiTi and NiSi on the Thermodynamics, Microstructure, and Properties of AlCoCuFe-Based High-Entropy Alloys

Aiming to solve the problem of spontaneous combustion on titanium via electrospark deposition (ESD), two AlCoCuFe-based high-entropy alloys (HEAs), AlCoCuFe-x (x = CrSiTi, NiSi), were produced by vacuum arc melting as electrodes in ESD process. The thermodynamic analysis of AlCoCuFe-based HEAs were carried out using the concept of mixing enthalpy matrix and a powerful thermodynamic calculation toolbox (HEA-Thermo-Calcu). The microstructure and mechanical properties of the two alloys were investigated. The AlCoCuFeCrSiTi alloy contains a body-centered cubic (BCC) phase and a face-centered cubic (FCC) phase. The AlCoCuFeNiSi alloy is composed of two BCC phases and an FCC phase. Addition of CrSiTi and NiSi to AlCoCuFe-based alloys makes the enthalpy of mixing to be sizably more negative than for the other AlCoCuFe-based HEAs. Notwithstanding the fact that the thermodynamic parameters do not agree with Yang’s proposition, the two alloys form simple solid solutions. The electronegativity difference (Δχ) favors a formation of the solid solution when Δχ ≤ 14.2. The hardness of AlCoCuFe-x (x = CrSiTi, NiSi) alloys reaches 935 HV and 688 HV, respectively. The yield strength, fracture strength, and ultimate strain of AlCoCuFeNiSi are larger, i.e., 29, 30, and 45%, respectively, than those of the AlCoCuFeCrSiTi alloy.

ELECTRO SPARK DEPOSITION OF TIB2 LAYERS ON TI6AL4V ALLOY

The electro spark deposition (ESD) method was used to create wear resistant layers of TiB2 ceramic onto Ti6Al4V titanium alloy. Various deposition parameters and ways of deposition were employed in this study. It was showed that the TiB2 layer on Ti6Al4Vcan be successfully created even using hand operating ESD equipment. Then, the microstructures of the obtained TiB2 layers on Ti6Al4Vwere investigated using scanning electron microscope. Finally optimal conditions of the electro spark deposition were determined with respect to the obtained microstructure. It was also demonstrated that by using of multiple runs dense layer of almost pore free TiB2 ceramic layer on Ti6Al4V titanium alloy can be successfully prepared.