Electrospark Deposition Process Research Articles

In-situ formation of ultra-hard titanium-based composite coatings on carbon steel through electro-spark deposition in different gas media

In the current study, ultra-hard TiC, TiN, and Ti(C,N) layers were in-situ formed on carbon steel substrate using pure titanium electrode via electro-spark deposition (ESD) in argon, nitrogen, argon/nitrogen, and air atmospheres. The synthesized coatings were characterized using various techniques, including FE-SEM/EDS, X-ray diffractometry, Raman spectroscopy, microhardness and nanoindentation tests, and surface roughness measurement. Also, a thermodynamic simulation was executed to estimate the phase-stability. Fe5C2, TiN, Fe3N, and Ti2O3 were determined as the major phases formed under the argon, nitrogen, Ar/N2, and air atmospheres, respectively. The formation of martensite at the interface of the coating and substrate in all atmospheres indicates the capability of the ESD process for surface hardening. The observed discrepancies between the empirically formed phases and the thermodynamics prediction can be related to the non-equilibrium conditions of the ESD process. It was revealed that gaseous media such as argon and nitrogen serve as a protective/active environment in the titanium/steel system. It is proposed that the electro-sparking of titanium under the active nitrogen medium follows an avalanche plasma regime. Under the argon flow, FeTi intermetallic layer is formed. Whilst, electro-sparking in ambient air leads to the formation of various Fe-Ti-O compounds, as well as different TiOn oxides. On the other hand, the utilization of nitrogen gas during the ESD increases the surface roughness and the thickness of the coating, rather than the deposition under the argon flow, due to the extra heat of reactions. The dynamic reactions occur between pure titanium, nitrogen, carbon, and oxygen, leading to the initial formation of Ti(C,N) at the top surface, followed by the production of titanium oxides in the middle layer. The coexistence of the super-hard Ti(C,N) with a hardness of 3130 HV at the top surface and titanium nitrides beneath it in a gradient mode effectively impedes the crack propagation.

PROCESS OPTIMIZATION OF ELECTRO-SPARK DEPOSITION USING LASER POWDER BED FUSION PROCESSED AlSi10Mg TOOL ELECTRODE THROUGH BOX-BEHNKEN DESIGN

Several researchers have recently expressed interest in additively manufactured electrodes for machining and surface modification applications. The additively manufactured AlSi10Mg tool electrode is one of the promising candidate materials for non-conventional processes. This research investigates the process parameters of laser powder bed fusion (L-PBF) processed AlSi10Mg tool electrodes for the electro-spark deposition process (ESD). The selected deposition parameters, namely, peak current (Pc), pulse-on time (Pon) and deposition time (DT) with various levels and experimentation, are based on the box-behnken design (BBD) of the response surface methodology. The deposition was carried out to analyze the output responses of material deposition rate (MDR), additive tool wear rate (ATWR) and surface roughness (SR). The multi-objective optimization was performed to minimize the ATWR and SR and maximize the MDR. The optimized ESD parameters of Pc = 6 A, Pon = 20[Formula: see text]s, and DT = 5 min were found with predicted responses of MDR = 0.019 mg/min, ATWR = 0.095 mg/min and SR = 3.86 [Formula: see text]m. The deposited surface witnessed the formation of debris, microcracks, and a solidified surface with a dark region and accumulated worn debris that has an elongated and flat shape. The workpiece substrate was exposed to a significant amount of additive tool electrode material (Si, Al, O, Mg, S), and different intermetallic ([Formula: see text] Si) 0.148, Al2O3, and Al2S3 formations have been recognized. This finding corroborates the efficient usage of L-PBF AlSi10Mg electrodes for ESD processes.

Performance analysis of GO gel composite coating on electro-spark deposited surfaces

The uneven surface roughness observed in the electro-spark deposition (ESD) process can be attributed to the unsteady pulsed electrical energy. ESD coating frequently needs to be processed in order to achieve higher surface quality. The surface of the coating undergoes processing techniques such as grinding, ultrasonic processing, and rolling. Because some coatings are hard and the surface hardness is uneven, surface processing is complicated. When a grinder is used for processing, the coating thickness is not easy to control. The product performance is uneven. When non-metallic coatings are used, it can enhance the surface quality of the coating. This study used a composite coating of sodium silicate and lubricating particles. Three coating schemes were studied. Graphene oxide (GO) gel and sodium silicate composite coating have the best overall performance. It can effectively improve the surface quality of the coating, with less roughness and better wear resistance. Graphene oxide gel is used to solve the problem of lubricating particle agglomeration. When it was actually applied to the SKH51 layer, the surface roughness Ra was reduced from 1.086µm to 0.113µm. It is effective in reducing friction and wear.

Synthesis, Wear and Corrosion of Novel Electrospark and Electrospark–Electrochemical Hybrid Coatings Based on Carbon Steels

The electrospark deposition (ESD) technique is a low-heat-input process that has great potential for coating applications and the restoration of damaged high-value parts. Carbon steels are commonly used as a substrate material for ESD coatings. However, we demonstrated that carbon steels could be used successfully as the electrode tool for the ESD process. Furthermore, ESD coatings commonly have a high as–deposited roughness. In view of this, in order to reduce the roughness of the ESD coatings, electrodeposition as a tool to alter surface morphology was investigated. Hence, the micro-leveling power of several electrolytes for Ni, Fe-W, Fe, and Cr electrodeposition were evaluated. The maximum leveling effect was detected for Ni electroplated from the Watts electrolyte. Thus, the novel hybrid coatings based on an ESD layer and a subsequent layer of electrodeposited Ni were obtained. ESD layers were obtained by using the following electrode tools as anodes: several types of carbon steels (St20, St30, and St45), alloys T15K6 (WC + TiC + Co), CuNiZn; and NiCr. The morphology and structure of the obtained hybrid coatings with an electrodeposited Ni top-layer was analyzed and compared to ESD coatings from the point of view of their wear and corrosion behavior. The wear rate of the novel ESD coatings based on carbon steels was comparable with coatings obtained using the NiCr electrode tool. Moreover, for all the studied cases, the corrosion resistance of the hybrid coatings was higher than for their ESD counterparts and close to electrolytic chromium.

Multi-Criteria Optimization of Automatic Electro-Spark Deposition TiCrNiVSi0.1 Multi-Principal Element Alloy Coating on TC4 Alloy

In this work, TiCrNiVSi0.1 coatings were prepared on TC4 alloy by CNC-controlled automatic electro-spark deposition (ESD). The TOPSIS-based Taguchi method was applied for multi-criteria optimization of ESD coating quality. Frequency (f), capacitance (c), and electrode moving speed (v) were considered process parameters for optimizing the coating quality criteria, which included coating thickness, coating coverage, and porosity in the coating. The optimized parametric setting of the ESD process (f = 700 Hz, c = 270 μF, v = 150 mm/min) was obtained. MPEA coatings with a thickness of about 70 um, a coverage rate almost reaching 100%, and porosity as low as about 1% were prepared. The wear- and burn-resistance functions of the TiCrNiVSi0.1 ESD coatings were investigated. The wear rates of the coating at room temperature and 400 °C are one-sixth and one-fourth of the TC4 alloy, respectively. A TiCrNiVSi0.1 alloy coating was deposited and significantly improved the burn resistance of the TC4 alloy.

Abrasive and Erosive Wear of TI6Al4V Alloy with Electrospark Deposited Coatings of Multicomponent Hard Alloys Materials Based of WC and TiB2

In the present work, abrasive and erosive wear of wear-resistant composite coatings with a complex structure and different phase compositions deposited on titanium surfaces was studied. The coatings were obtained by electrospark deposition (ESD) using two types of hard-alloy compositions: WC–TiB2–B4C–Co–Ni–Cr–Si–B and TiB2–TiAl reinforced with dispersed nanoparticles of ZrO2 and NbC. The influence of the ESD process parameters on the roughness, thickness, composition, structure and coefficient of friction of the coated surfaces was investigated, and their role in protecting the titanium surfaces from wear was clarified. Dense coatings with the presence of newly formed wear-resistant phases and crystalline-amorphous structures were obtained, with roughness, thickness and microhardness that can be varied by the ESD modes in the range Ra = 2.5 ÷ 4.5 µm, δ = 8 ÷ 30 µm and HV 8.5 ÷ 14.0 GPa. The new coatings were found to reduce the abrasive and erosive wear of the coated surfaces by up to four times. The influence of the geometric characteristics, composition and structure of coatings on the wear intensity and wear resistance of coatings was studied.

Experimental investigations on optimizing manufacturing parameters for electrospark deposition diamond wire saw

The third generation of superhard semiconductor materials, represented by single-crystal SiC, is used widely in microelectronics due to their excellent physical and mechanical properties. However, their high hardness and brittleness have become bottlenecks in their development. A diamond wire saw (DWS) has become the mainstream tool for sawing hard and brittle crystal materials. However, the diamond abrasive is consolidated on the core wire through resin or electroplated nickel, and the holding strength is not high. When sawing superhard crystal materials, the efficiency is low. To improve the sawing efficiency of superhard crystal materials, it is of great significance to improve the wear resistance of the wire saw and the holding strength of abrasive particles. Electrospark deposition (ESD) can deposit electrode materials on the substrate with low heat input to achieve metallurgical bonding between metal materials. It can effectively improve the gripping strength of the abrasive grains. The sawing ability of the wire saw to make the consolidated DWS by the ESD process. In this paper, ESD equipment was designed according to the characteristics of the ESDDWS process. The discharge gap size and electrode consumption are monitored in real time by a single-chip microcomputer (SCM). Orthogonal experiments were carried out for the two motion modes. The effects of process parameters, such as (A) grain size, (B) abrasive content, (C) pulse duration time, (D) compacting pressure, (E) current, (F) electrode diameter, (G) pulse interval time, (H) reciprocating times, and (I) wire feed speed, on the quality of ESDDWS were analyzed. Through extreme difference analysis (EDA), the optimal parameter combinations of ESDDWS were obtained. In motion mode 1, a combination of grain size W10, abrasive content 1 wt%, pulse duration time 20 μs, compacting pressure 400 MPa, current 19 A, electrode diameter 3 mm, and pulse interval time 2 ms can obtain the optimal value of the number of deposition points and protrusion abrasive particles at the same time. The sequence of manufacturing parameters affecting the two indicators is F > A > G > E > B > D > C. In motion mode 2, the combination of grain size W40, abrasive content 4 wt%, pulse duration time 20 μs, compacting pressure 300 MPa, current 23 A, electrode diameter 3 mm, reciprocating times 1, and wire feed speed 2 mm/step can obtain the optimal value of the number of deposition points and protrusion abrasive particles at the same time. The sequence of manufacturing parameters affecting the two indicators is C > I > F > E > B > H > D > A.

Thermal simulation of the continuous pulse discharge for electro-spark deposition diamond wire saw

Due to their excellent physical and mechanical properties, third-generation super-hard semiconductor materials (such as SiC, GaN) are used widely in the field of microelectronics. However, due to its ultra-high hardness, the machining is very difficult, which has become the bottleneck of its development. Slicing is the first machining procedure that directly affects the subsequent process. Fixed abrasive diamond wire saw (DWS) has been widely used in cutting hard and brittle materials. However, the diamond abrasives are attached to a core wire by resin or electroplated, that slicing super hard crystals is very difficult and inefficient. In order to improve the slicing efficiency, it is necessary to improve the holding strength and wear resistance of the DWS. The electro-spark deposition (ESD) process can deposit electrode materials on the substrate under the condition of low heat input to achieve metallurgical bonding between metal materials. And it can improve the wear resistance, corrosion resistance, and repair the size of the workpiece. It has been widely used in the field of surface modification engineering. It can effectively improve the bonding strength of the abrasive grains, and the sawing ability of the wire saw to make the consolidated DWS by the ESD process. Due to its thin matrix and poor thermal properties, the saw wire is easy to burning or even breaking in the manufacturing process. At present, the selection of pulse interval time in the ESD process is generally determined by the duty factor. However, the pulse interval time selected according to duty factor is difficult to meet the heat dissipation requirements of electro-spark deposition DWS (ESDDWS). In this paper, two kinds of motion modes of ESDDWS manufacturing are put forward, according to the manufacturing characteristics of ESDDWS. The boundary conditions of the continuous pulse discharge of ESDDWS are established. The thermal simulations of continuous pulse discharge of ESDDWS under two motion modes are analyzed. According to the simulation results, the basis of the value of pulse interval in the ESDDWS process is put forward. The effect of pulse interval time on the mechanical performance of the wire saw is analyzed experimentally. The results show that selected the discharge interval time base on the simulation results can ensure the continuous production of the ESDDWS.

Anode Materials for Electrospark Alloying of Aluminium-matrix Alloys

This paper describes the optimum compositions of four aluminium matrix alloys (A, B, C, D) obtained from oxides (NiO, TiO2, ZrO2, Cr2O3) by means of aluminothermy (self-propagating high-temperature synthesis, or SHS metallurgy). These compositions were developed in order to enhance the wear resistance of coatings on steel 45 during electrospark deposition. Depending on the composition of synthesized alloys, the authors obtained different combinations of the structural components — i.e. aluminides of Ni, Zr, Cr, Ti, complex alloyed solid solution and eutectic. The above structural components of the aluminium matrix alloys were identified by means of electron microscopy and electron probe microanalysis. The authors established and substantiated how the alloy composition can impact the structure and the distribution of elements (segregation). The synthesized alloys A, B, C and D were used as anode materials to enhance the wear resistance of coatings on steel 45. Rows of gain (∑Δк·10–4, g), erosion (∑Δа·10–4, g), transport coefficient (∑Кp, %) and wear factor (∑Иls·10–4, g) were obtained. For all of the above mentioned parameters, mathematical expressions were obtained for the polynomial equations of the trend showing kinetic dependencies on the electrospark deposition time when the studied anode materials were used in the process. A test of validity was also defined to analyze the resultant polynomial lines of the Rл trend showing the kinetic dependencies ∑Δк, ∑Δа, ∑Кp, ∑Иls. High wear resistance values could be observed in all cases when the anode material D was used in the electrospark deposition process – % (wt.): 33.29 Al; 41.6 Ni; 10.27 Cr; 4.6 Zr; 7.23 Ti; 2.98 Fe. The material D showed optimum values in all the studied modes. Correspondingly, the value ∑Иls increased by 3.27 times. Lower wear resistance values were obtained for the alloy A – % (wt.): 36.52 Al; 47.65 Ni; 15.83 Ti. The wear factor ∑Иls increased by 1.85 times. At the same time, the wear factor of steel 45 without coating when it was subjected to similar wear conditions was as follows: ∑И(st.45) = 72·10–4 g.The research was carried out under financial support of the RF Ministry of Science and Higher Education within the Government Order No. FEME-2020-0010 "Physical-chemical and technological base of metallothermic metal synthesis in metal alkali melts and complex alloyed nickel aluminides via SHS metallurgy". Investigations were conducted using equipment of the common use center "Applied materials science"of the Pacific National University.

Preparation and Properties of Mo Coating on H13 Steel by Electro Spark Deposition Process.

H13 steel is often damaged by wear, erosion, and thermal fatigue. It is one of the essential methods to improve the service life of H13 steel by preparing a coating on it. Due to the advantages of high melting point, good wear, and corrosion resistance of Mo, Mo coating was fabricated on H13 steel by electro spark deposition (ESD) process in this study. The influences of the depositing parameters (deposition power, discharge frequency, and specific deposition time) on the roughness of the coating, thickness, and properties were investigated in detail. The optimized depositing parameters were obtained by comparing roughness, thickness, and crack performance of the coating. The results show that the cross-section of the coating mainly consisted of strengthening zone and transition zone. Metallurgical bonding was formed between the coating and substrate. The Mo coating mainly consisted of Fe9.7Mo0.3, Fe-Cr, FeMo, and Fe2Mo cemented carbide phases, and an amorphous phase. The Mo coating had better microhardness, wear, and corrosion resistance than substrate, which could significantly improve the service life of the H13 steel.

Comparative research of electrospark deposited Tungsten alloy coating in two kinds of gas

A W alloy was used as an electrode to prepare a coating on a CrNi3MoVA steel substrate by means of electrospark deposition (ESD) technique. The mass transfer coefficient (MTC) from the electrode to the substrate was calculated through measuring the mass change by employing an electronic balance in air and in argon, respectively, and the morphologies, composition and phase structure were analyzed by utilizing scanning electron microscopy (SEM), energy dispersive X-ray spectrum (EDS) and X-ray diffraction(XRD). The results showed that the ambient gas has an obvious influence on the surface morphology, microstructure, phase structure and MTC of the ESD W alloy coating. Although the MTC in argon has a high value in the ESD process, the whole W alloy coating can’t keep thickening as the ball-like bulges grow up on the surface, which will make the coating rough with the deposition time goes on.

Parametric Study of Automated Electrospark Deposition for Ni-Based Superalloys

Conventional electrospark deposition (ESD) processes used in industry are well suited to the coating and repair of small areas for the purpose of hardfacing, corrosion resistance, or dimensional restoration. Although significant advances have been made in the range of materials that can be processed, the comparatively slow deposition rate limits the potential applications of a traditional manually operated ESD process. In this study, an automated ESD system was demonstrated for the application of Ni-based superalloy (Inconel 718) coatings on Ni- and Fe-based substrates. A preliminary study was used to determine the influence of process parameters on an automated system, with capacitance, voltage, electrode force, and electrode travel speed parameters chosen to provide higher deposition rates while maintaining high deposition quality. A comparison of Inconel 718 and 316L stainless steel substrates found that the influence of substrate composition on coating hardness and coating composition was limited to the first 40um. These results pave the way for ESD of larger-area coatings and longer-duration repairs without the need for human operators.

Thermal simulation of the single discharge for electro-spark deposition diamond wire saw

Due to their excellent physical and mechanical properties, third-generation super hard semiconductor materials (such as SiC, GaN) are widely used in the field of microelectronics. From the crystal bar to electronic devices, slicing is the first machining procedure that directly affects the subsequent process. Fixed diamond wire saw has been widely used in cutting hard and brittle materials. However, the diamond grits of wire saw are bonded through the binding agent’s mechanical embedding that slicing super hard crystal is very difficult and inefficient. In order to improve the slicing efficiency, it is necessary to improve the holding strength and wear resistance of the diamond wire saw. The electro-spark deposition (ESD) process can form metallurgical bonding between metal materials at low heat input. The holding strength and wear resistance of the diamond wire saw can be effectively improved. In this paper, the mechanism of the manufacturing process of ESD diamond wire saw (ESDDWS) is introduced, and the conditions of the manufacturing process of ESDDWS are put forward. A model of the surface heat source of saw wire is established considering the wire shape. The transient thermal analysis of the single discharge of ESDDWS is carried out in ANSYS, and the effect of material compaction on material physical properties is considered. According to the simulation results, the parameter range of the manufacturing process of ESDDWS is predicted. The predictions agreed with experiment observation.

Structure and Wear Resistance of FeNiCrBSiC–MeB2 Electrospark Coatings

The structurization of coatings produced by electrospark deposition (ESD) from the commercial selffluxing FeNiCrBSiC alloy and FeNiCrBSiC-based composites, such as FTB20 (FeNiCrBSiC–20 wt.% TiB2) and FCB20 (FeNiCrBSiC–20 wt.% CrB2), on a steel 45 substrate was studied. The electrospark FeNiCrBSiC coating about 70 μm thick has a globular surface and the FTB20 and FCB20 coatings form a continuous layer up to 50 μm thick over the entire samples. The microhardness does not change across the deposited coating thickness and is 10–14 GPa. The chemical compositions of the ESD coatings and the electrodes are the same, which indicates that the electrode material does not mix with the steel substrate. The structure of the FeNiCrBSiC, FTB20, and FCB20 electrodes and coatings differs significantly because chromium boride and/or titanium boride inclusions refine from 20–25 μm to 1 μm in the ESD process. The heterophase structure of the ESD coatings represents a nickel–iron-base matrix reinforced with fine boride and carboboride particles. The effect of speeds and loads on the wear rate of ESD coatings in dry friction conditions was examined. Electrospark coatings produced from the WC–6% Co hardmetal were tested as wear resistance reference. The wear rate of the FeNiCrBSiC, FTB20, and FCB20 coatings decreases and that of the WC–6% Co coating increases when the speed rises from 4 to 12 m/sec. The wear rate of the ESD coatings becomes one order of magnitude higher when the load increases from 0.1 to 0.4 MPa. Analysis of the friction surfaces showed that wear of the FeNiCrBSiC coating was caused by failure of the globules and that of the FCB20 coating by brittle fracture of the deposited layer. The ESD FTB20 coating has two to three times higher wear resistance than the FeNiCrBSiС coating because of the oxidative wear mechanism whereby protective oxide films develop on the friction surfaces and act as a solid lubricant.

Enhancing fatigue life of additive manufactured parts with electrospark deposition post-processing

Metal additive manufacturing processes allow for the production of highly dense parts with increased geometric freedom and less waste than traditional manufacturing techniques. However, one of the biggest challenges in using these parts is the relatively high surface roughness inherent to the manufacturing process. This roughness negatively affects fatigue properties and necessitates the use of post-processing surface treatments. Several methods are presented for improving local surface properties of laser powder bed fusion parts using electrospark deposition (ESD), hammer peening and heat-treatment processes. An optimized surface roughness reduction of 82% and near-surface hardness increase of 85% is obtained. Post-processed Hastelloy X parts reach > 107 cycles during fatigue testing at 350 MPa, in comparison to failure at 105 cycles in the as-built condition. The improvement in mechanical properties obtained with a combined ESD and peening process shows potential for the selective enhancement of critical surface regions in additive manufactured parts.

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.

Electro spark deposition of WC–TiC–Co–Ni cermet coatings on St52 steel

The electro spark deposition (ESD) technique has been successfully applied to deposit a cermet layer of WC/TiC/Co/Ni at room temperature on a St52 carbon steel substrate and the electrochemical properties of the bare and coated samples were evaluated. Influence of ESD process parameters on electrochemical properties of coatings were examined by using of potentiodynamic polarization and impedance spectroscopy (EIS) techniques. It has been possible to obtain a dense coating with adjusting the ESD process as the current limit of 15 A, frequency of 11 KHz, duty cycle of 50%, rotating speed of 200 rpm and spark energy of 1.46 mJ. The results confirmed that the sample with these fabrication parameters had higher ESD efficiency with the value of 64% and the dense coating without holes and micro cracks could be fabricated through the process. The electrochemical tests also confirm the good quality of the optimized coated sample. According to the results, the largest corrosion resistance with maximum Rcoat 76.16 Ω cm2 was observed in optimized coating condition.

A novel method to fabricate composite coatings via ultrasonic-assisted electro-spark powder deposition

To improve traditional electro-spark deposition (ESD) technology and meet the requirements for special applications, a novel ultrasonic-assisted electro-spark powder deposition (UEPD) process is developed in this study. The unique electrode tool in this new method consists of a NiCrBSi alloy powder as a deposition material and a Cu electrode core as a support component, which are bonded to each other by means of a silver-containing conductive adhesive. By using this UEPD process, a metal matrix composite (MMC) coating is successfully fabricated on ASTM 1045 steel. The coating has an average thickness of approximately 52.3 μm and exhibits efficient metallurgical bonding with the substrate as well as good continuity. The microstructure in the coating mainly presents submicron-columnar dendrites that epitaxially grow perpendicular to the substrate surface, which mainly contain a Ni-rich γ-(Ni, Fe) solid solution, intermetallic FeNi3 and Cr-rich carbide and boride precipitates. These refined grains and hard reinforcements significantly increase the hardness and tribological properties of the coating. Combining the discharge morphology, microstructure and chemical composition of the UEPD electrode and coating, the formation process of the UEPD coating is analysed and discussed in detail. The adhesive NiCrSiB powder layer was melted and transferred to the surface of the substrate during the UEPD process. The separation of the powder tends to start from the interface of the powder layer and electrode core due to weak connectivity. This behaviour is considered beneficial to the quantitative control of powder deposition. In addition, the introduction of ultrasonication can promote dispersion of the metal droplets to obtain a better quality coating.

Al0.5CrCoFeNi high entropy alloy for Geothermal Environment

Al0.5CoCrFeNi high entropy alloy was processed by mechanical alloying and investigated in term of powders characteristics and microstructures. The obtained power was pressed and sintered resulting in a bulk material that will be further processed to obtain electrodes that will be deposited on the substrate by electro spark deposition process, in an attempt to obtain a corrosion resisting coating. High Entropy Alloys are known due to their corrosion and wear resistant properties, which makes them the perfect candidates in numerous domains as marine, geothermal, oil and gas industries, where the aggressive environment tends to corrode the in work components of the equipment. The cocktail effect is characteristic to the high entropy alloys, where every component concurs in an alloy with predetermined properties.

Application of Electrospark Deposition Process and Modified SHS Electrode Materials to Improve the Endurance of Hot Mill Rolls. Part 1. Features of Coating Formation on SPHN-60 White Cast Iron Substrates

Application of Electrospark Deposition Process and Modified SHS Electrode Materials to Improve the Endurance of Hot Mill Rolls. Part 1. Features of Coating Formation on SPHN-60 White Cast Iron Substrates