Increase Of Arc Current Research Articles

Effects of arc current and bias voltage on properties of AlCrN coatings by arc ion plating with large target

The AlCrN hard coating was prepared by industrial grade Quark-M500B multi-arc ion plating equipment with large target. The arc current and substrate bias voltage were changed respectively to investigate the influence of deposition parameters on coating properties. The surface and cross-section morphology of coatings were observed by scanning electron microscope. The tribological properties were tested by UMT-2 friction and wear tester, and the corrosion resistance was evaluated by electrochemical workstation. The results show that AlCrN coatings with less macroparticles can be prepared when the arc current is 100 A. With the increase of arc current, the deposition rate of AlCrN coating increases, and the hardness and wear performance of the coating decrease due to the influence of macroparticles and coating compactness. The hardness reaches 2723 HV when the arc current is 100 A, and the friction factor is about 0.84. The wear rate is about 7.1 × 10–6 mm3 N−1·m−1. The bias of substrate does not affect the deposition rate of AlCrN coatings strongly. The hardness, wear resistance and corrosion resistance first increase and then decrease with the increase of substrate bias. The coating shows the best test performance when the bias voltage is −100 V with the hardness 2750 HV. The friction factor is about 0.74, and the wear rate is about 3.5 × 10–6 mm3 N−1·m−1.

Measurement of radial temperature distributions of the blown CO2 arcs under different conditions

In this paper, the radial temperature distributions of the blown CO2 arcs in a model gas circuit breaker were investigated by optical emission spectroscopy methods. The CO2 flows with different flow rates (50, 100 and 150 l min−1) were created to axially blow the arcs burning in a polymethyl methacrylate (PMMA) nozzle. Discharges with different arc currents (200 and 400 A) were conducted in the experiment. The absolute intensity method was applied for a carbon ionic line of 657.8 nm to obtain the radial temperature profiles of the arc columns at a cross-section 1 mm above the nozzle. The calibration for the intensity of the C II 657.8 nm line was achieved by the Fowler–Milne method with the help of an oxygen atomic line of 777.2 nm. The highest temperature obtained in the arc center was up to 19 900 K when the arc current was 400 A and the CO2 flow rate was 50 l min−1, while the lowest temperature in the arc center was about 15 900 K when the arc current was 200 A and the CO2 flow rate was 150 l min−1. The results indicate that as the arc current increases, the temperature in the arc center would also increase apparently, and a larger gas flow rate would lead to a lower central temperature in general. It can also be found that the influence of the CO2 flow rate on the arc temperature was much less than that of the arc current under the present experimental conditions. In addition, higher temperature in the arc center would cause a sharper temperature decrease from the central region towards the edge.

A plasma sprayed superhydrophobic coating prepared with Al@WO3 core-shell powder and photocatalytic degradation performance

The insufficient hydrophobicity due to difficulty in producing surface nanostructures hinders the application of thermal spraying technology for metal-based superhydrophobic coatings. In this paper, the hydrophobicity of an Al-based composite coating prepared by plasma spraying was innovatively improved by WO3 nanoparticles electroless plated on Al spraying powders and nano-oxides produced by chemical vapor deposition induced by plasma spraying (PS-CVD). Results showed that Al@WO3 core-shell powder was fabricated as feedstock. A mixture of two nano-products (Al2O3 and W) was formed on the surface of the coating and the reason may be that aluminum vapor reduced WO3 to W. The effects of plasma arc current and H2 flow rate on surface morphology and wettability of the as-prepared coating were investigated. It was found that the increase in H2 flow rate and plasma arc current enhanced the generation of surface nano-products by PS-CVD, and thus improved the coating hydrophobicity. However, extremely high temperature may result in the refusion of nano-products. The highest water droplet contact angle (WCA) reached 157.0 ± 1° and the lowest water droplet sliding angle (WSA) was 7.5 ± 1°. Finally, the photocatalytic activity of the coating was tested by its performance in the degradation of methyl orange, and it was found that acidic conditions facilitated the degradation performance. The superhydrophobicity and photocatalysis performance demonstrate the potential use of the as-prepared coating in antibacterial and antifouling fields.

Analysis of Electrical Characteristics of Inter-wire Arc in Cross-Coupling Arc

As a new composite welding heat source introduced in recent years, the cross-coupling arc uses a non-consumable electrode arc (plasma arc) and a consumable electrode arc (inter-wire arc) in cross-coupling, in which the plasma arc is the main arc and the inter-wire arc is the vice arc, to realize the separate control of the heat input to the workpiece, arc force, and droplet transfer. To reveal the electrical characteristics of the inter-wire arc under the action of the plasma arc, in this study, rotating probes are used to sweep across the plasma arc. When the probes rotate into the plasma arc, a circuit is formed, and the electrical characteristics of the inter-wire arc are indirectly analyzed according to the circuit: the probe centering current and input voltage are used as the physical quantities. The results show that at a certain wire feed rate, the inter-wire arc current increases with increasing input voltage. When the input voltage is low, the wire feed rate has no obvious effect on the inter-wire arc current. At a higher input voltage, where the wire feed rate is high, the inter-wire arc current decreases. With the increase in the plasma arc current, the inter-wire arc current first increases quickly and then increases slowly, and simultaneously, the striking arc time becomes longer. With the increase in the interval between the nozzle and the workpiece, the inter-wire arc current increases, but when the arc length increases to a certain limit, the slope of the welding current clearly declines.

Influence of nitrogen concentration on structure, composition and properties of nitride coatings deposited by vacuum arc plasma-assisted method

The coatings based on molybdenum nitride have been obtained by vacuum arc plasma-assisted method and have been investigated in a complex. For generation of gas-metal plasma two types of plazmagenerator were used: arc evaporator based on self-sustained arc discharge with cathode spot and a source of gas plasma on the basis of the non-self-sustained arc discharge with the combined hot and hollow cathode. The influence of the modes of plasma assistance on characteristics, composition and structure of MoN coatings was studied. It is revealed that the increase of arc current of a gas plasma source leads to increase in a share of nitrogen in gas-metal plasma, to increase the concentration of nitrogen in a coating, to increase in a share of molybdenum nitrides in coating and significant improvement of characteristics: to increase of hardness and wear resistance.

Simulation, Design, Construction of Duoplasmatron and Diagnostic Neutral Beam System for Alborz Tokamak

Diagnostic Neutral Beam (DNB) has been used for measuring plasma parameters of tokamaks such as ion and electron temperature, safety factor, impurity concentration and etc. Ion source and electrical power supply specification are the main part of DNB. Arc discharge current value is affected by filament current and anode voltage. Beam current changes with arc current signal in our experiment that agree with theoretical relations. Sixty milli-ampere (60 mA) pulse beam current is because of arc current of about 40 A and extraction voltage of about 20 kV. The increase of beam current with arc current has been reported experimentally and effect of arc current on beam current has been investigated for several high extraction voltages. Optimum condition, which means having a telescopic beam (minimum divergence) for specific parameters of duoplasmatron, has been simulated and verified with experimental test. The best extraction voltage for these parameters has been found to be about 16-kV. The ratio of the perpendicular velocity to parallel velocity has been calculated to be about 0.012. It has been shown experimentally with optical emission spectroscopy that increase in arc current and magnetic current increase proton content of beam.

Effect of arc\u2013current and spray distance on elastic modulus and fracture toughness of plasma-sprayed chromium oxide coatings

In this experimental study, chromium oxide powder was sprayed on a low-carbon steel substrate using the atmospheric plasma spray process. The current and standoff distances (SODs) were varied to study their effect on the fracture toughness of the coatings. Theoretically, as the arc current increases, the melting of the ceramic oxide should increase and this in turn should lead to the formation of a dense coating. However, it was observed that if the arc power is too high and because the particle size of the powder is small (approximately 30 μm), the particles tend to fly away from the plasma core. Similarly, an appropriate SOD should provide the particles with more melting time, thus resulting in a dense coating. On the other hand, a larger SOD leads to the solidification of the molten particles before the droplets can reach the substrate. All these effects may lead to substantial variation in the fracture toughness of the coating. The present paper attempts to correlate the plasma spraying parameters and microstructure of the coating with the fracture toughness and other primary coating properties.

Comparison of thermal and electric characteristic for free-burning arc using coupled and decoupled sheath models

A comparison of coupled and decoupled sheath models is performed to study the interaction between the arc column and the near cathode layer in this paper. The coupled model used in this paper is modified based on the previous work. The thermal conductions of the heavy particles and electrons between the arc column and the near cathode layer are added to the energy transport equation in the model, which is different from the decoupled model of cathode sheath and arc column. The simulation shows that: (1) The energy (due to thermal conductions) delivered from the arc column to the near cathode layer is always positive, and it increases as arc currents increase. (2) Compared with the decoupled model for free-burning arc (20–200 A currents) at the diffuse mode of the cathodic attachment, the total arc voltage of the coupled model is closer to the value of experiment. (3) The voltage drop of the near cathode layer calculated by the coupled mode is always lower than that calculated by the decoupled model. The differences increase as the arc current increases. The voltage drop of arc column calculated by the coupled mode is lower than that calculated by the decoupled model at low current, and the situation is opposite at high current. (4) The current distribution of coupled model along the cathode surface is more uniform. In additional, we compare our coupled model with another coupled sheath model. The results from the two coupled sheath models are in good agreement in high currents.

Modeling of mixing and interaction of multi-cathode spot vacuum arc jets

Vacuum arc consists of cathode spot and mixing zone, arc column and anode zone. The separate jets and the mixing zone should be considered in the model of diffuse arc. Moreover, the interaction between the plasma jets in multi-cathode spot vacuum arc also is very important. In this paper, mixing and interaction of multi-cathode spot vacuum arc jets were studied through simulation. To completely investigate the mixing and interaction of vacuum arc jets, a steady 3D Magneto-Hydro-Dynamic (MHD) modeling was established. In order to find out the influence of different parameters on mixing and interaction of vacuum arc jets, simulations with different parameters such as currents, angel of vacuum arc jets, with or without electromagnetic equations, tilted jets and different height of mixing zone were conducted. The simulation results show that the densities of ion number and plasma pressure as well as ion temperature increase with the increase of arc current, while the plasma velocity decreases. The jet center is more deviated from the cathode center with the increase of angle of tilted jets.

Hydrogen and carbon black nano-spheres production via thermal plasma pyrolysis of polymers

This work addresses the thermal plasma pyrolysis of four polymer waste samples to produce hydrogen rich gases and carbon black nano particles. Samples were treated in a furnace fitted with a twin dc thermal plasma torch. The resultant gases were analyzed to determine its composition by GC and OES analysis. These analyses showed that gas products consist of hydrogen and some hydrocarbons without any carbon monoxide. It was found that with an increase in arc current, the concentrations of hydrogen and hydrocarbons in gas products increases and decreases, respectively. Furthermore, by SEM, TEM and XRD analysis of solid products, it was found that the high purity carbon black nano spheres were synthesized successfully by pyrolytic decomposition of “Acrylonitrile Butadiene Styrene”.

Modeling of the anode surface deformation in high-current vacuum arcs with AMF contacts

A high-current vacuum arc subjected to an axial magnetic field is maintained in a diffuse status. With an increase in arc current, the energy carried by the arc column to the anode becomes larger and finally leads to the anode temperature exceeding the melting point of the anode material. When the anode melting pool is formed, and the rotational plasma of the arc column delivers its momentum to the melting pool, the anode melting pool starts to rotate and also flow outwards along the radial direction, which has been photographed by some researchers using high-speed cameras. In this paper, the anode temperature and melting status is calculated using the melting and solidification model. The swirl flow of the anode melting pool and deformation of the anode is calculated using the magneto-hydrodynamic (MHD) model with the volume of fraction (VOF) method. All the models are transient 2D axial-rotational symmetric models. The influence of the impaction force of the arc plasma, electromagnetic force, viscosity force, and surface tension of the liquid metal are all considered in the model. The heat flux density injected into the anode and the arc pressure are obtained from the 3D numerical simulation of the high-current vacuum arc using the MHD model, which gives more realistic parameters for the anode simulation. Simulation results show that the depth of the anode melting pool increases with an increase in the arc current. Some droplets sputter out from the anode surface, which is caused by the inertial centrifugal force of the rotational melting pool and strong plasma pressure. Compared with the previous anode melting model without consideration of anode deformation, when the deformation and swirl flow of the anode melting pool are considered, the anode temperature is relatively lower, and just a little more than the melting point of Cu. This is because of liquid droplets sputtering out of the anode surface taking much of the energy away from the anode surface. The azimuthal velocity of the anode melting pool for arc current 12.5 kA root-mean-square (rms) is larger than that for 17.5 kA (rms), which is likely to be caused by the thinner liquid layer, and also a smaller melting pool mass of 12.5 kA.

Current–voltage characteristics of hydrogen DC plasma torches with different sizes in an external axial magnetic field**Project supported by the Special Fund for Basic Scientific Research of Central Colleges, China (Grant No. 2012FZA4023).

Current–voltage (I–V) characteristics of hydrogen DC plasma torches with different sizes in an external axial magnetic field under atmospheric pressure are reported. Three anodes with different diameters are adopted in a 50-kW torch: 25 mm, 30 mm, and 35 mm, respectively. Two different diameters of anodes, that is, 100 mm and 130 mm, are adopted in a 1-MW plasma torch. The arc voltage shows a negative trend with the increase of arc current under the operating regimes. On the contrary, arc voltage shows a positive trend as the flow rate of carrier gas increases, and a similar trend is found with increasing the external magnetic flux density. A similarity formula is constructed to correlate the experimental data of the torches mentioned above. Linear fitting shows that the Pearson correlation coefficient is 0.9958.

Pulsed electrical discharge synthesis of red photoluminescence zinc oxide nanoparticles

Zinc oxide (ZnO) nanoparticles have been prepared using a pulsed electrical discharge in a liquid medium. The effects of the processing parameters, including liquid media, current, frequency of the electrical discharge and electrode gap distance exert significant effects on the characteristic and properties of ZnO nanoparticles. The synthesized ZnO nanoparticles are characterized using a combination of transmission electron microscopy (TEM), energy dispersive X-ray (EDS) and photoluminescence (PL) spectroscopy. The average size of ZnO nanoparticles varies between 10–25 nm depending on the processing parameters. It is found that an increase in the arc current plays a great role in particle growth and results in a significant increase in average particles size. Both frequency of discharge and electrode gap distance can influence the average particle size and distribution due to the variation in the cooling rate. The PL spectrum for all as-synthesized ZnO nanoparticles exhibits an ultraviolet emission (~3.4 eV) and a red visible emission (~1.98 eV). The blue shift is independent of the average size of the ZnO nanoparticles. However, the intensity of visible emission is significantly enhanced with the decrease of the particle sizes. The porous structure and irregular particle surface are suggested to contribute significantly to the visible red emission.

Mechanical and Structural Properties of Superhard TiAlSiN Coatings Deposited by Arc Ion Plating of Cylindrical Cathode

TiAlSiN coatings were deposited on WC-Co metal by using a cathodic arc ion deposition method of cylindrical cathode. We used Ti / Al (50 / 50 at.%) arc target and silicon sputter target. The influence of the nitrogen pressure, TiAl cathode arc current, bias voltage, and deposition temperature on the mechanical and the structural properties of the films were investigated. The structural features of the films were investigation in detail using X-ray diffraction. And coatings were characterized by means of FE-SEM, nanoindentation, Scratch tester, Tribology tester, XRD and XPS. The hardness of the film reached 43 GPa at the cathode arc current of 230 A and decreased with a further increase of the arc current. And the adhesion of the film reached 34 N. The results showed that the TiAlSiN coating exhibited an excellent mechanical properties which application for tools and molds.

Motion and Splitting of Vacuum Arc Column in Transverse Magnetic Field Contacts at Intermediate-Frequency

Arc motion and splitting of vacuum arc at intermediate frequency (400-800 Hz) were investigated under transverse magnetic field (TMF). The experiment was performed on cup-type TMF contacts with contact diameter of 40 mm and a contact gap of 4 mm in a single-frequency circuit. With high-speed photography we characterized the arc appearance at different arc currents from 3.3 kA-rms to 10 kA-rms at intermediate frequencies. As arc current increases from 3.3 kA-rms to 10 kA-rms the arc appearance changes obviously. When current value is 3.3 kA-rms (current frequency 400-800 Hz), there is almost no splitting arc; when the current exceeds 5 kA-rms (current frequency 400-800 Hz), the arc rotates at a speed above 20 m/s, accompanied by an observable splitting arc. The splitting arc could be observed at different frequencies and the arc-voltage had no noises when splitting occurred. The motion direction and the velocity of arc column were studied. Finally, the formation of a split arc was discussed.

Multiwalled Carbon Nanotube Synthesis Using Arc Discharge with Hydrocarbon as Feedstock

Synthesis of multiwalled carbon nanotube (MWCNT) by arc discharge process is investigated with methane (CH4) as background and feedstock gas. The arc discharge is carried out between two graphite electrodes for ambient pressures 100, 300, and 500 torr and arc currents 50, 70, and 90 A. Plasma kinetics such as the density and temperature for arc discharge carbon plasma is determined to find out the contribution of physical parameters as arc current and ambient pressure on the plasma dynamics and growth of MWCNT. With increase in applied arc current and ambient pressure, an increase in plasma temperature and density is observed. The synthesized samples of MWCNT at different experimental conditions are characterized by transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and X‐ray diffraction. A decrease in the diameter and improvement in structure quality and growth of MWCNT are observed with increase in CH4 ambient pressure and arc current. For CH4 ambient pressure 500 torr and arc current 90 A, the well‐aligned and straight MWCNT along with graphene stakes are detected.

The Theoretical and Experimental Investigation into Technological Parameters of High-Melting Metal Arc Spraying

The experimental study is done for technological parameters of high-melting metal arc spraying to study the influence of spraying current, spraying voltage and wire feed voltage on spraying arc and the influence of spraying current on coating temperature and analyze theoretically the distribution rules of spray gun jet speed field and temperature field and their influencing factors. The results showed that the arc current increases along with arc voltage increase. The lower the spraying voltage is, the smaller the molten grain size becomes. However, if the arc voltage is lower than the minimum critical arc voltage of the material, the arc could not keep smooth burning. The spraying current has correspondence relationship with wire feed speed. The spraying current could be adjusted through wire feed speed adjustment.

Numerical investigation of the swirl gas angle and arc current dependence on evaporation of hafnium cathode in a plasma cutting arc

The effects of arc current and swirl gas angle on a plasma cutting arc are investigated using a 2-D thermofluid model developed for arc plasma with consideration of hafnium (Hf) cathode evaporation. Numerical modeling is extremely important to predict the erosion amount of Hf cathode for different process parameters in plasma cutting arcs. Results show that a larger swirl gas angle causes a high-temperature plasma area in front of the cathode surface shrunken in the radial direction and that the flow patterns changed to the opposite direction in front of the cathode at swirl gas angles from 12° to 30°. This change in the gas flow pattern induces Hf vapor transport along the center-axis direction to the nozzle outlet. With the increase of arc current, the whole temperature field markedly increases, and the radius of arc plasma is expanded in the radial direction. The total amount of mass loss of Hf cathode evaporation was predicted to be enhanced with increasing arc current and swirl gas angle from 12°.

A Numerical Model with arc length variation of welding arc with constant voltage power source

In the present paper, Tungsten Inert Gas (TIG) arc with Constant Voltage (CV) power source is modelled if arc length changes. And TIG arc with Constant Current (CC) power source is also modelled if arc length changes. The TIG arc is assumed on base material of water-cooled copper. For the CV power source, maximum temperature of arc plasma and arc current increase with decrease of arc length. For the CC power source, arc voltage changes but maximum temperature of arc plasma is almost constant in spite of change of arc length. Arc power increases with decrease of arc length for the CV power source. On the other hand, arc power decreases with decrease of arc length for the CC power source. For the CV power source, arc power changes largely if arc length changes. However, for the CC power source, arc power changes little if arc length changes. Heat input from welding power source is more stable using a CC power source than a CV power source at TIG welding with a change of arc length.

Decomposition mechanism of phenol in water plasmas by DC discharge at atmospheric pressure

The decomposition mechanism of high concentration of phenol solution in water plasmas at atmospheric pressure was investigated at different arc currents. The results showed that the removal efficiencies of phenol, total organic carbon, and chemical oxygen demand were increased with the increase in arc current. The concentration of phenol was reduced from 52.8 g L −1 down to 1.0 × 10 −5 g L −1 at an arc current of 8 A with the energy yield of 8.12 g kWh −1. Major gaseous compounds were H 2, CO 2, CO, and CH 4. However, at a low arc current, trace levels of benzene (C 6H 6), and cyclopentadiene (C 5H 6) were detected in effluent gas, and formic acid (HCOOH) and formaldehyde (HCHO) were observed in liquid effluent. By the analysis of reaction intermediates and a calculation of carbon balance, the main reaction pathways were proposed as follows: firstly, electron dissociation in arc region to generate phenoxy (C 6H 5O) radical; second, chemical oxidation or reduction in plasma flame region to form C 6H 5O and C 6H 6. After phenol decomposition, the generated intermediate species would undergo complex reactions to form stable compounds in plasma flame region. The most favorable mechanism is the formation of CO, which is conducted by the ring open step of C 6H 5O and C 6H 6 by thermal decomposition or the attachment of active radicals such as O, H, and OH with respect to CO generation. In downstream region, the generated intermediate species were easily recombined with H or oxidized by OH to form unwanted products, such as HCOOH, HCHO, and H 2O 2.