Increase Of Arc Current Research Articles

Effect of arc deposition process on mechanical properties and microstructure of TiAlSiN gradient coatings

In order to successfully prepare a new advanced TiAlSiN gradient coating with Ti content gradually decreased but Al content gradually increased from the cemented carbide substrate to the outermost coating surface by arc ion plating, we deeply investigated the influence mechanisms of two important process parameters. These parameters include substrate bias voltage and arc current, which affect the mechanical properties and microstructure of the gradient coating. The results show that bias voltage and arc current directly affect the particle accumulation effect on the coating surface and the re-sputtering effect caused by high-energy ion bombardment, thus affecting the deposition efficiency of the coating and the formation of defects such as macro-particles and pits on the coating surface. The increase of bias voltage is conducive to the increase of the density of columnar crystals and nanocrystals. While the increase of arc current makes the coating with high Al content transform from columnar crystals to nanocrystals. The hardness and interfacial adhesion of the gradient coatings showed a tendency of firstly increasing and then decreasing with the increase of both bias voltage and arc current. When the bias voltage and arc current are -80 V and 160 A respectively, the coating has the best mechanical properties, its surface hardness reaches 36.94 GPa, and the interfacial adhesion exceeds 120 N. In addition, with the increase of bias voltage and arc current, particles are deposited on the surface of the coating with higher energy, which leads to the preferential orientation transition from (111) to (200) plane. The high hardness of TiAlSiN coating is mainly due to the formation of high Al content of fcc-TiAlN crystals and amorphous Si3N4 in the gradient-coated surface layer. The results have important theoretical and practical significance for developing new high-performance gradient coating tools.

Fabrication and Characterization of Nickel‐Aluminide Cladding by Dual‐Wire Arc Additive Manufacturing

Nickel aluminide is a widely utilized intermetallic compound, prized for its high strength, low density, and resistance to both corrosion and creep. This study investigates the impact of heat input during the fabrication of nickel‐aluminide intermetallic compounds using the dual‐wire gas tungsten arc welding process. The results indicate that an increase in clad layer dilution from 28.9% to 33.4% reduces the amount of aluminum in the molten pool from 32.46 to 21.96 wt% while increasing the presence of the Ni3Al phase. Additionally, the NiAl phase decreases when moving from the upper side of the coating to the fusion line. When the arc current is increased from 110 to 150 A, a coarse dendritic structure forms, and the dendritic arms increase from 2.6 ± 0.4 to 5.5 ± 0.3 μm. This increase in current also results in yield strength and tensile strength values of 500.21 ± 14.56 and 752.32 ± 25.12 MPa, respectively, representing decreases of 15.2% and 5.1%. Furthermore, as the arc current increases from 110 to 150 A, both the friction coefficient and the wear rate increase to 0.43 and 0.29 ± 0.02 μg m−1, respectively. However, corrosion resistance improves by 66.3%.

Experimental study on the full cycle evolution of high-intensity atmospheric dc arc discharge from breakdown to extinguishment.

In this study, the spatiotemporal evolution of full cycle of high-intensity dc argon arc discharge at atmospheric pressure is investigated by using a transferred arc device, which is easy to be directly observed in the experiment. Combining the voltage and current waveforms with high-speed images, the full cycle evolution process of high-intensity atmospheric dc arc can be divided into five different stages: breakdown pulse stage, cathode heating stage, current climbing stage, stable arc discharge stage, and finally arc extinguishing stage. The characteristics of each different stage are analyzed in detail through the electrical properties, high-speed pictures, and spectroscopic measurements. The results show that the strong luminescence region develops from the vicinity of cathode and anode to the middle in the breakdown pulse stage, which is explained from the spatiotemporal evolution of distributions of excited argon atom and ions. The development velocity of emission intensity of argon ions is mainly determined by the dominant stepwise ionization process. Then the cathode heating stage appears with many bright and nonuniformly distributed light spots on the cathode surface, and the electron emission mechanism of cathode gradually changes to the thermionic emission as the surface temperature rises. With the increase of arc current, the discharge channel significantly expands, then becomes stable due to the increment of the Lorentz force. The characteristics of arc extinguishing stage are clarified in terms of the decay of charged particles density.

Research on the Influence of Pantograph Catenary Contact Loss Arcs and Zero-Crossing Stage on Electromagnetic Disturbance in High-Speed Railway

During train travel, various factors, such as body vibration, uneven contact lines, and hard spots on carbon sliding plates and over electric neutral zones, often lead to brief separation between the pantograph and the contact line, i.e., the pantograph catenary contact loss phenomenon. With the continuous increase in train speed and traction power, the probability of pantograph catenary contact loss occurrences rises with a gradual increase in the energy of electromagnetic radiation, making the pantograph catenary arc a primary source of interference affecting the electromagnetic safety of high-speed railways. Understanding the mechanism, characteristics, and influencing factors of electromagnetic interference caused by pantograph catenary contact loss discharges is of utmost importance for analyzing and resolving on-site equipment interference faults. Our analysis of the physical process of pantograph catenary contact loss reveals that when the distance between the pantograph and catenary is significant and the duration is lengthy, high-voltage breakdown occurs within the pantograph catenary gap as it comes close again after the complete extinguishing of the arc. To investigate the electromagnetic radiation characteristics resulting from high-voltage breakdown discharge arcs in the pantograph catenary contact loss process, we established a laboratory test platform for assessing the electromagnetic disturbance characteristics of high-voltage pantograph discharge. We designed a test procedure utilizing fixed-gap breakdown discharge to evaluate the impact of the arc zero-crossing stage on electromagnetic radiation disturbances. Our research indicates that when the pantograph catenary spacing remains constant, an increase in voltage level leads to an elevation in the current within the discharge circuit, resulting in an increased intensity of impulse radiation generated during pantograph catenary contact loss events. During the moment of gap breakdown, the antenna records the highest amplitude of electromagnetic radiation. Also, during the steady-state arc ignition phase of the pantograph catenary gap, the zero-crossing stage generates pulsed discharge currents within the circuit, accompanied by substantial electromagnetic radiation. As the arc current increases, the zero-crossing time shortens, and the pulse current during the zero-crossing process decreases, accompanied by a reduction in the excited electromagnetic radiation. These observations reveal novel characteristics of electromagnetic radiation disturbances during steady-state arc ignition. The outcomes of our study provide valuable insights that can contribute to our understanding of the characteristics and influencing factors of electromagnetic radiation in pantograph catenary contact loss discharges and offer theoretical guidance for the resolution of pantograph catenary contact loss interference faults.

Numerical analysis of low-current arc characteristics in micro-TIG welding

A semi-empirical two-temperature (2-T) arc model is developed to study the near-electrode regions and thermal non-equilibrium characteristics of low-current arcs that employ pin-to-pin electrodes in micro‑tungsten inert gas (TIG) welding. Special emphasis is given to accurately depict the electrodes-arc attachment area and the spatial distributions of plasma temperature in 1–4 A argon arcs. The conditions of thermal non-equilibrium, as well as the coupling of the arc plasma and the cathode, are considered. The simulated electron temperature distributions are in good agreement with the arc appearances captured by the high-speed camera, and the predicted arc voltage is only 1.8 V lower than the experimental data. In contrast to TIG welding arcs that operate at higher currents, the temperature contours of the low-current arc column are parallel but slightly expanded in the vicinity of the electrodes. As the arc current decreases, the near-cathode voltage drop increases substantially. The electron temperature in the center of the arc column is almost constant, while the heavy particle temperature drops significantly, causing the arc column to contract. The heat flux at the center of the anode surface does not change as the arc current increases, but it increases significantly outside the 0.25 mm radius.

Effect of multi-arc current on the microstructure and properties of TiAlSiN coating on zircaloy-4 alloy

TiAlSiN coatings are deposited on zircaloy-4 by multi-arc ion plating at 50 A, 60 A and 70 A, respectively. The macro-morphology, micro-morphology, chemical composition and phases of the prepared coatings are observed and analyzed, and the high temperature oxidation behavior and adhesion strength of coatings are tested. The results demonstrate that the quantity of large particles on TiAlSiN coating increases gradually as the arc current increases, the coating becomes denser and denser with the porosity decreases gradually, and the content of Al elements in the coating increases gradually with the increase of multi-arc current. The phases of TiAlSiN coatings deposited at different multi-arc currents before oxidation mainly includes Ti3AlN, AlN, Ti2N. Meanwhile, the high temperature oxidation behavior of the coating is also improved gradually and the adhesion strength increases first and then decreases. When the arc current is 60 A, the adhesion strength is up to 23 N which is relatively large. The coatings deposited at 70 A shows the best high temperature oxidation resistance behavior, mainly due to the generation of a large amount of Al2O3 oxide in the coating after oxidation.

Research on the Energy Characteristics of a Transferred Arc Plasma-Chemical Reactor for Waste Treatment

This study has been performed to reveal the main characteristics of operating a direct current (DC) plasma-chemical reactor (PChR) designed for hazardous waste treatment. The PChR employs thermal plasma as the operating environment. The investigations presented in this paper were conducted to study the electrical and energy characteristics of the plasma torch and plasma-chemical reactor during the destruction of inorganic waste. The PChR is equipped with a plasma torch with a nominal capacity of 50 kW and a free-burning arc. The zone of heat release from the atmospheric pressure DC arc cathode and arc anode (melted waste) spot is combined with the area of chemical reactions. The plasma torch (PT) parameters vary in the range of arc current I = 120–180 A, arc voltage U = 250–280 V, arc length x = 0–100 mm, and gas flow rate G = 1–3 g/s at atmospheric pressure, using air as the plasma-forming gas. The experimental results confirmed that plasma technology has several advantages over conventional incineration, including higher temperatures, heat source independence from the waste being processed or additional fuel, and a shorter exposure time in the high-temperature area. It was determined that the arc current increases with increasing arc length. With increasing arc length, the initial part begins to operate in a turbulent regime. This study determines the dependence on the heat flux transferred by electrons to the anode on the arc current. The convective heat flux density distribution over the anode heating spot was measured and discussed.

Wire electrode of 5754 aluminum modified by PVD-thin film depositions

Manufacturers of welding wire electrodes for GMAW welding adapt the alloy compositions of welding wire electrodes in order to adjust the weld pool behavior and the properties of the weld. Additively manufactured components in various sizes and with complex structures and multi-axial stress states place diverse demands on the material. The filler wire can significantly influence the material properties. The approach shown here describes the possibility of coating welding wire electrodes by physical vapor deposition, which enables flexible adjustment of the welding material composition. The element content in the weld metal can be adjusted within certain limits via the coating thickness. In the arc, applied thin-film coatings with coating thicknesses < 1 µm pass into the molten phase together with the substrate wire electrode according to ISO 18273—S Al 5754 (AlMg3). Microalloying elements such as TiB2 or Ti added to the weld pool in this way change the composition and thus influence the microstructure in the weld metal. This results in a grain refinement of up to 46%, which in turn has a positive effect on hot cracking susceptibility. PVD-coated welding electrodes also show changes in arc characteristics. With increasing TiB2 layer thickness, the arc length decreases by up to 44%, while the arc current increases. The fusion penetration behavior changes from a narrow finger-shaped to a round fusion penetration.

Metallurgical characterisation of multi-track Stellite 6 coating on SS316L substrate

ABSTRACT This article attempts to investigate the root cause of the possible failure of the cobalt-based Stellite 6 coating deposited on SS316L substrate using plasma-transferred arc welding through an extensive metallurgical and mechanical analysis by considering parameters such as contact angle, dilution and aspect ratio. The chosen sample with optimum input parameters, such as weld current 100–180 A, travel speed 100–180 mm/min, etc., having good mechanical properties but with traces of minor coating irregularities is thoroughly investigated for its metallurgical performance. Studies revealed that the Stellite 6 coating is dominated by the FCC cobalt and HCP cobalt along with carbides of different elements such as M7C3, M6C and M23C6 phases where M is tungsten and Chromium. Stellite 6 microstructure shows a hypoeutectic structure of dendrites rich in cobalt and interdendrites rich in chromium increasing microhardness. As arc current increases, percentage dilution increases, leading to a decrease in weld coating contact angle.

Effect of the structure and properties of welded zones made of Sv-AK5 welding wire at robotic surfacing

The study covers the effect of welding arc current (47, 57, and 67 A) on the structure and properties of deposited samples obtained by robotic electric arc surfacing. Sv-AK5 (ER4043) welding wire of the Al-Si system was used as a filler material. Surfacing was carried out on a substrate in the form of a 6 mm thick plate made of AMg6 alloy (Al-Mg system). During surfacing, a typical two-phase structure of a hypoeutectic composition is formed in samples typical for Al–Si alloys with a silicon content of 5 %. Along the height of deposited layers, there is a tendency to structure enlargement in the direction from the substrate, which is associated with the accumulation of heat in layers deposited along the height. As welding arc current increases, α-Al-based dendrites and eutectic silicon crystals are refined with an increase in the density and a decrease in the microhardness of deposited samples. The increase in density is due to the reduced proportion and size of gas pores, as well as refined structural components. The decrease in microhardness is associated with the increased proportion of the soft phase (α-Al dendrites) and decreased quantity of hard eutectic silicon crystals. The average content of silicon in samples deposited in three modes is in the range of 5.46–5.91%, which corresponds to the chemical composition of Sv-AK5 (ER4043) welding wire. Higher welding arc current contributes to an increase in the tensile strength and a slight decrease in the offset yield strength and relative elongation. The features of changes in the mechanical properties of deposited samples are determined by of the specific cast structure of deposited layers formed under conditions of directional solidification in the direction from the substrate.

Investigation on anode modes of vacuum arc under different contact opening speeds

This paper aims to investigate the anode modes of vacuum arc at different opening speeds, especially at a high opening speed that exceeds 3 m/s. The butt contacts made of CuCr30 and CuCr50 with a diameter of 15 mm are used. Experiments are conducted at the current of 3.3, 4.4, 5.5, and 6.3 kA with a frequency of 50 Hz. An electromagnetic repulsion actuator provides the average opening speed from 1.7 to 3 m/s. The experimental results show that the number of droplets splashing into electrodes increases as the arc current increases, while a higher opening speed decreases the droplets. A higher opening speed will reduce the transferred charge before the anode spot type 2, and a higher Cr content increases the transferred charge before the anode spot type 2. Increasing opening speed will decrease the starting time of anode spot type 2, but it increases the gap distance when anode spot type 2 appears. Meanwhile, the increase in Cr content delays the formation of anode spot type 2.

Arc Characteristics and Welding Process of Laser K-TIG Hybrid Welding

The Q235 steel plate butt joint was successfully welded by the laser K-TIG hybrid welding method. The effects of hybrid welding process parameters such as welding current, the distance between heat sources, laser power, laser defocusing amount, and welding speed on the coupled arc profile and welding process stability were studied. The results indicated that the laser deflects the K-TIG arc, and the deflection angle becomes smaller as the arc current increases. After K-TIG generates small holes, if the laser beam acts on the bottom of the keyhole, the welded depth can be further increased; however, the laser power has little effect on the welded depth. The distance between heat sources is the main factor affecting the state of laser-arc coupling. Optical microstructures of welded joints showed that the grains in the arc zone were coarser than those in the laser zone, and there are more columnar crystals in the fusion zone. The microhardness of the weld center is significantly higher than that of the base metal, up to 220 HV. At the same time, the change of tensile strength of the weld under the influence of a single parameter was analyzed, and it was found that tensile properties of the weld first increased and then decreased with the increase of K-TIG arc current I, heat source distance D, and welding speed V, respectively. With the increase of laser power P, it first decreased and then increased, and with the increase of laser defocusing amount δf, it showed a downward trend.

Wear Properties of Iron-Based Alloy Coatings Prepared by Plasma Transfer Arc Cladding

Plasma transfer arc cladding technology has been widely utilized in surface engineering, repairing and remanufacturing. In the present work, multiple cladded thick claddings were prepared on compacted graphite cast iron (CGI) substrates with iron-based powders through plasma transfer arc cladding technology using different plasma arc currents to improve the surface wear resistance. The coatings’ phase and microstructure were analysed through XRD, SEM and EDS. The coatings’ microhardness and wear resistance were characterized. There were pearlite, graphite, austenite and secondary carbides in the iron-based alloy coatings. Due to the heat influence during the multiple cladding process, a spheroidal graphite transition zone appeared between the substrate and the coating. The microhardness of the claddings varied from 363 to 402 HV as the plasma arc current was changed from 45 to 60 A. With the increase of plasma arc current, the cladding’s microhardness increased. The iron-based coating’s minimum friction coefficient and wear mass loss were about 0.48 and 4.2 mg, respectively, when the plasma arc current was 60 A, which are lower values than those of the compacted graphite iron substrate with the friction coefficient and wear mass loss of 0.55 and 8.2 mg. Compared with the substrate, the iron-based alloy claddings achieved the effect of reducing friction and wear resistance simultaneously, which resulted from the self-lubricating effect of graphite and high wear-resistance of carbides in the claddings. The iron-based coatings had a similar abrasive wear mechanism to the CGI, which should be helpful to repair or remanufacture CGI workpieces.

Improvement of the Tribological Properties of Alumina Coatings by Zirconia Addition

Al2O3 and Al2O3-ZrO2 coatings were deposited on stainless steel using atmospheric plasma spraying. The influence of arc current and zirconia addition on the surface morphology of the coating, phase composition and tribological properties under dry sliding conditions were investigated. The addition of zirconia reduced the surface roughness of the coatings. The X-ray diffraction measurements indicated that the Al2O3 coatings were composed of β-Al2O3, α-Al2O3, and γ-Al2O3 phases. The addition of zirconia led to the formation of tetragonal and monoclinic phases of zirconia in the as-sprayed coatings. The friction coefficients of Al2O3 and Al2O3-ZrO2 coatings were similar and varied in the range of 0.72–0.75. The specific wear rates of the as-sprayed coatings were reduced with the increase of arc current. It was obtained that the wear rates of the Al2O3-ZrO2 coatings were at least three times lower compared to Al2O3 coatings.

Numerical Simulation of Temperature Field and Temperature Control of DC Arc Plasma Torch

In order to study and analyze the internal heat transfer process of DC arc plasma torch, a two-dimensional axisymmetric model of DC arc plasma torch was established based on magnetohydrodynamics and heat transfer theory. The finite element analysis software COMSOL was used to simulate the temperature field under different conditions. The results show that when the terminal current is constant, the DC plasma arc voltage and the average temperature of the torch outlet increase with the increase of nitrogen standard flow rate, and the maximum temperature in the plasma torch decreases with the increase of nitrogen standard flow rate. When the standard flow rate of nitrogen is constant, the arc voltage decreases with the increase of arc current, and the average temperature of plasma torch exit and the maximum temperature in the torch increase with the increase of arc current. The analysis of simulation data provides theoretical guidance for the temperature control of experimental DC plasma torch.

Numerical simulation of anode heat transfer of nitrogen arc utilizing two-temperature chemical non-equilibrium model* *Project supported by the National Natural Science Foundation of China (Grant Nos. 11735004 and 12005010).

A detailed understanding of anode heat transfer is important for the optimization of arc processing technology. In this paper, a two-temperature chemical non-equilibrium model considering the collisionless space charge sheath is developed to investigate the anode heat transfer of nitrogen free-burning arc. The temperature, total heat flux and different heat flux components are analyzed in detail under different arc currents and anode materials. It is found that the arc current can affect the parameter distributions of anode region by changing plasma characteristics in arc column. As the arc current increases from 100 A to 200 A, the total anode heat flux increases, however, the maximum electron condensation heat flux decreases due to the arc expansion. The anode materials have a significant effect on the temperature and heat flux distributions in the anode region. The total heat flux on thoriated tungsten anode is lower than that on copper anode, while the maximum temperature is higher. The power transferred to thoriated tungsten anode, ranked in descending order, is heat flux from heavy-species, electron condensation heat, heat flux from electrons and ion recombination heat. However, the electron condensation heat makes the largest contribution for power transferred to copper anode.

Experimental Study on the Restrike Mode of a DC Arc Anode Attachment

The restrike mode is an important arc anode attachment mode under the cross flow in DC arc device, which often causes a large amplitude of arc voltage fluctuations and therefore has an important impact on the performance of arc thermal plasma device. A transferred arc device with planar anode parallel to gas flow direction is used to experimentally study the restrike mode characteristics under different operating conditions. It is found that for the case of a fixed gas flow, the arc restrike frequency increases while the amplitude of arc voltage jump decreases with the increase of arc current. For the case of a fixed arc current, both arc restrike frequency and amplitude of arc voltage jump increase with the increase of gas flow rates. Further analysis shows that the restrike process in one period can be divided into two phases. The first phase corresponds to the generation and development of upstream new arc roots and the disappearance of downstream old root, and its time scale is less than the order of 1 ms. The second phase corresponds to the newly formed, single arc root moving downstream under the combined action of gasdynamic drag force and Lorentz force until new arc root appears upstream. The time-resolved temperature field measurement based on the relative intensity of emission spectrum method shows that the temperature at the junction of the arc column and the anode arc root is relatively low, while it still able to maintain the current conduction, which indicates the significant deviation from thermodynamic equilibrium state.

Generation of a Pulsed Electron Beam by a Forevacuum Plasma-Cathode Source Based on a Constricted Arc Discharge

We describe the features of electron emission from the plasma formed by a constricted arc discharge, and the generation of a pulsed (100–150 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> ) low-energy (up to 10 keV) electron beam by a plasma-cathode electron source based on this type of arc in the forevacuum pressure range (5–20 Pa). The electron beam current pulse is delayed relative to the arc discharge current pulse. Limitation of the discharge current to the cylindrical part of the anode, increasing the gas pressure, and increasing the beam accelerating voltage all serve to reduce this delay time and provide a sharper rise time of the electron beam current pulse. The emission of electrons from the plasma formed by the constricted arc discharge is accompanied by a decrease in arc voltage and a corresponding increase in arc current. These characteristics are due to the specifics of operating the constricted arc discharge in the forevacuum pressure range and also the influence of backstreaming ions penetrating into the discharge system from the downstream electron beam region.

Numerical investigation on the influence of metal particles on the characteristics of a high-current vacuum arc

In the arc-burning process of a high-current vacuum arc (HCVA), the metal particles (MPs) splashed from the active anode will have a significant influence on the plasma characteristics of the arc column. In this paper, the influence of varying MPs on the characteristics of HCVA are studied by establishing a HCVA model containing single or multiple MPs. The simulation results show that when the MPs vaporized metal vapor (MV) enters the interelectrode region and once the arc column plasma cannot ionize all atoms immediately, the ionization layer and the neutral atom vapor area (NAVA) will be formed in the adjacent region of the MPs. When the MP diameter and temperature increase, the number of vaporized metal atoms increases, so that the influence range of MV increases, and the area of ionization layer and the NAVA increases. In addition, when the arc current increases or the MPs are closer to the cathode surface, the greater the ion number density and ion pressure around the MPs are, the stronger the compression on the MV will be, resulting in the decrease of the area of ionization layer and the neutral atom vapor, and the increase of the net ionization rate of the ion number density. When multiple MPs exist in the interelectrode region at the same time, the MV from the MPs will affect each other. In the central region of multiple MPs, the density of MV becomes the largest, while the net ionization rate of ion number density is distributed in the periphery region of the MP group.

Luminous spot distribution of vacuum arc discharge with deuteride cathode

Vacuum arc discharges with deuteride cathode have many applications, such as nondestructive examination, oil logging, and neutron activation analysis. Deuteride cathode releases many gases during discharge, which is quite different from metal cathode. The discharges display some unique characteristics. A maguifying lens and an ICCD camera are used to observe the luminous spots of vacuum arc discharge. The space resolution of this system is about 5 μm, and the time resolution is about 2 ns. The arc current has a full width at half maximum (FWHM) of about 0.9 μs, and its waveform is half cycle sinusoidal. The results show that the luminous spots merge together into a big one in most cases. Sometimes there are two or more luminous spots due to droplets. The area of the luminous spot grows as arc current increases. The cathode spots’ merging is helpful to increase plasma density and improve discharge efficiency.