Vacuum Arc Process Research Articles

Influence of the Metallic Sublayer on Corrosion Resistance in Hanks' Solution of 316L Stainless Steel Coated with Diamond-like Carbon.

The purpose of the study was to ascertain the corrosion resistance in Hanks' solution of Cr-Ni-Mo stainless steel (AISI 316L) coated with diamond-like carbon (DLC) coatings to establish its suitability for biomedical applications, e.g., as temporary implants. The influence of the carbon coating thickness as well as the correlated effect of the metallic sublayer type and defects present in DLC films on corrosion propagation were discussed. The results obtained were compared with findings on the adhesion of DLC to the steel substrate. The synthesis of carbon thin films with Cr and Ti adhesive sublayers was performed using a combined DC and a high-power-impulse vacuum-arc process. Evaluation of the corrosion resistance was carried out by means of potentiodynamic polarisation tests and scanning electron microscopy. Adhesive properties of the sublayer/DLC coating systems were measured using a scratch tester. It was found that systems with Ti sublayers were less susceptible to the corrosion processes, particularly to pitting. The best anti-corrosion properties were obtained by merging Ti with a DLC coating with a thickness equal to 0.5 μm. The protective properties of the Cr/DLC systems were independent of the carbon coating thickness. On the other hand, the DLC coatings with the Cr sublayer showed better adhesion to the substrate.

Effects of ion-plasma treatment temperature of the aluminium coating on the structure and phase composition of the VT6 titanium alloy

In this study, we studied the effects of aluminum coating treatment temperature on the microstructure and phase composition when applied to a VT6 titanium alloy substrate within a low-pressure arc discharge plasma environment. The ion-plasma treatment was conducted at 450 and 500 °C, employing argon shielding, while the aluminum coating was deposited using the vacuum-arc process, resulting in a coating thickness of ~3 μm. Microstructural analysis was performed using a scanning electron microscope, and the structural and phase composition were examined using X-ray diffraction (XRD) imaging in symmetric imaging mode with CuKα radiation. Our findings demonstrate that the application of the aluminum coating initiates the formation of a near-surface α-stabilized layer, extending up to 2.5 μm in thickness due to the heat generated during the ion cleaning process. Subsequent ion-plasma treatment further results in the development of a TiAl3 intermetallide site, reaching thicknesses of up to 1.5 μm, while the α-stabilized region expands to 5.5 μm. Higher temperatures during the treatment process contribute to an increase in the thickness of these aforementioned layers and also lead to the emergence of an intermediate TiAl intermetallic layer.

Investigation of the dielectric recovery process of vacuum arc in double breaks by planar laser-induced fluorescence

The multibreak vacuum circuit breaker uses multiple short gaps to interrupt the fault current, greatly improving the dielectric strength, and is a viable method to realize high-voltage interruption. The metal vapor distribution near the current zero is crucial for the dielectric recovery process in the multibreak vacuum circuit breaker. Due to the complicated dielectric construction and the interaction between the breakers, the vacuum arc inevitably deviates from the axisymmetric distribution during the interruption process. The traditional diagnosis method limited to 0D or 1D is not sufficient to study the real distribution of metal vapor near the current zero. To address these issues, we developed a planar laser-induced fluorescence method to measure the 2D distribution of copper vapor near the current zero by detecting 510.6 nm fluorescence intensity. The results indicate that for the butt contacts, the copper vapor is diffused in the gap of the high-voltage break and aggregated on the cathode surface of the low-voltage break. The axial magnetic field and transverse magnetic field affect the 2D copper vapor distribution and eliminate the inconsistency, which is achieved by affecting the motion of charged particles and the ionization-recombination process. Furthermore, the copper vapor density exhibits a positive dependence on the arc current, and the magnetic field impacts the density increase rate and distribution mode.

Vacuum Arc Plasma Coating for Polymer Surface Protection— A Plasma Enhanced In-Orbit Additive Manufacturing Concept

In-orbit additive manufacturing (AM) is a promising approach for fabrication of large structures. It allows to expand and accelerate human space exploration possibilities. Extrusion-based AM was demonstrated in zero gravity, while the realization of such a process in orbit-like vacuum conditions is currently under exploration. Still, a solution for protection of the UV and IR radiation sensitive polymers is needed in order to prevent their early mechanical failure under space conditions. Vacuum arc plasma based process is widely applied on earth for thin protective coating deposition. Its major advantage is its scalability—from tiny size used in electric propulsion to large scale coating devices. The usability of the vacuum arc process in space conditions was shown in electric propulsion applications in nano-satellites. In this work we discuss and demonstrate the integration of vacuum arc process as a post processing step after Fused Filament Fabrication (FFF) for additive manufacturing and functionalization of long polymer structures. Here we address the concept for technical realization, which integrates the vacuum arc into additive manufacturing process chain. More over we present a laboratory prototype, which implements this concept together with a use case, where a previously printed PEEK structure is coated with aluminum based coating suitable for UV radiation protection.

Simulating ion flux to 3D parts in vacuum arc coating: Investigating effect of part size using novel particle-based model

This work presents a novel particle-based computational model capable of predicting coating distribution and composition on real parts in ion-based physical vapor deposition (PVD) processes. The model treats ions as particles (using test particle Monte Carlo method) and electrons as a fluid (using Boltzmann's relation). This combination makes it possible to simulate a realistic plasma sheath around a coated part and locally enhanced electric field around the part's edges. This simulation tool is instrumental especially in predicting the so-called “antenna-effect” - i.e. changes in coating thickness and composition near sharp edges of coated parts. It can also be used for quantifying the effect of coater loading or fixture design, as illustrated by simulating the effect of a top-plate on the coating distribution. The model is validated by two experimental data sets - a milling tool and a drill bit, both coated by hard nitride coatings in a vacuum arc process.

Development of a Graphite Coating and Its Transfer from Batch to Coil Process for Application in PEMFC for Hydrogen-Powered Vehicles

In the present paper, coating systems consisting of a metallic corrosion barrier and a conductive graphitic carbon layer were deposited by a DC vacuum arc process. The coatings were developed in a batch process for application in the polymer electrolyte membrane fuel cell (PEMFC), and transferred to a continuous coil process to facilitate industrial mass production. The coating samples in the coil process had to achieve comparable results to the samples produced in the batch process, to meet the requirements of the environment prevailing in the fuel cell.The transfer to roll-to-roll processes is a crucial factor for commercial upscaling of PEMFC production. The experimental results showed that the electrical conductivity and corrosion resistance of the samples in the coil process were significantly improved compared to the uncoated base material and showed comparable performance to batch coated samples. X-ray photoelectron spectroscopy (XPS) was performed to determine the depth profile and the surface composition. Additional measurements were recorded for the contact resistances using the four-wire sensing method as well as corrosion resistance using potentiodynamic methods.

Influence of lithium and silicon coatings on tungsten erosion in arc plasma

• Arc erosion of W substrate can be effectively mitigated by Li and Si coatings. • Selective formation of spots on coatings is responsible for erosion mitigation. • Vapor shielding of Li coating provides effective mitigation of tungsten erosion. Arc spots formed on a plasma-facing component (PFC) have a stunning resemblance with the arc spots formed on a cathode of a vacuum arc. Hence, in this paper, a laboratory-scale vacuum arc process is used to get a better understanding of the arc erosion process of the tungsten (W) material. The performance of lithium (Li) and silicon (Si) coatings in erosion mitigation of W material is analyzed. The virgin W substrate was eroded significantly by arc spots and numerous W droplets were ejected into the interelectrode plasma from cathode with velocity of tens m/s. However, the W substrates can be effectively protected by Li and Si coatings from arc erosion. Preferential formation of arc spots on the coatings is responsible for the arc erosion mitigation. Compared with the virgin W substrate, no ejection of W droplets from the cathode was observed in the cases of coatings. Li and Si droplets were accidently ejected from the cathode and the ejected droplets were rapidly ablated in the arc plasma. For the case of Si coating, the W substrate was slightly melted and eroded due to the arc spots formed on the coating. By contrast, no obvious melting and erosion were observed on the W substrate for the case of Li coating, which is possibly due to the vapor shielding effect of Li between the W substrate and arc spots. These results confirm coatings served as a sacrificial protective layer and can reduce tungsten surface erosion caused by arcs, which provides a new reference for protecting first wall materials in future fusion devices.

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.

Quo Vadis: AlCr-Based Coatings in Industrial Applications

AlCr-based hard nitride coatings with different chemical compositions and architectures have been successfully developed and applied over the last few decades. Coating properties are mainly influenced by deposition conditions and the Al/Cr content. The fcc structure is dominant for an Al-content up to Al0.7Cr0.3N and is preferred for most cutting applications. Different (AlCrX)N alloying concepts, including X = Si, W, B, V, have been investigated in order to enhance oxidation resistance and wear behaviour and to provide tribological properties. AlCr-based oxynitrides and even pure oxides (Al1−xCrx)2O3 with different crystalline structures have been explored. Multi- and nanolayered coatings within the AlCr materials system, as well as in combination with (TiSi)N, for example, have also been implemented industrially. The dominant deposition technology is the vacuum arc process. Recently, advanced high-power impulse magnetron sputtering (HiPIMS) processes have also been successfully applied on an industrial scale. This paper describes basic coating properties and briefly addresses the main aspects of the coating processes as well as selected industrial applications.

Metal Droplet Evaporation in Post-Arc Breakdown Process of Aviation Variable Frequency Vacuum Arc

Metal Droplet Evaporation in Post-Arc Breakdown Process of Aviation Variable Frequency Vacuum Arc

Numerical Simulation and Analysis of Arc Anode Erosion Process with Electrode Rotation

A three-dimensional geometric model of anode contact of vacuum circuit breaker is established. Considering the influence of electrode rotation on vacuum arc and anode thermal process, a physical model of phase transformation process is established for the melting and evaporation of anode surface. The solid-liquid mixing area is treated by the description method of porous media, and the numerical simulation of anode thermal process is carried out. The conclusion is that with the increase of time, the anode surface temperature increases, molten pool development, molten pool depth deepening, in addition, with the increase of electrode speed, the highest temperature on the surface of the contact and the size of the molten pool were reduced, the temperature distribution more uniform. It provides theoretical basis for evaluating the breaking capacity of vacuum circuit breaker.

Study on the influence of metal particles on the characteristics of high-current vacuum arc plasma

In the arcing process of high-current vacuum arc, the metal particles spattered from the active anode will have a significant influence on the plasma characteristics of the arc column when they entrance the interelectrode area. In this paper, the characteristics of a high-current vacuum arc with metal particle are studied by modeling and simulation. The results show that the vapor produced by metal particle will obviously cool the arc plasma and reduce the current density in the vicinity area of the metal particle. In addition, the metal particle will hinder the movement of the cathodic plasma and complicate the ion density distribution and movement process near the metal particle. Finally, an obvious ionization layer will be formed around the metal particle. When the metal vapor passes through the ionization layer, the vapor will be ionized rapidly, and an abundance of ions will be produced at the same time. The research results are of great significance for the deep understanding of arcing process of high-current vacuum arc.

Tetrahedral amorphous carbon prepared filter cathodic vacuum arc for hole transport layers in perovskite solar cells and quantum dots LEDs

ABSTRACT (ta-C) films coated through the filtered cathodic vacuum arc (FCVA) process as a hole transport layer (HTL) for perovskite solar cells (PSCs) and quantum dot light-emitting diodes (QDLEDs). The p-type ta-C film has several remarkable features, including ease of fabrication without the need for thermal annealing, reasonable electrical conductivity, optical transmittance, and a high work function. X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy examinations show that the electrical properties (sp3/sp2 hybridized bond) and work function of the ta-C HTL are appropriate for PSCs and QDLEDs. In addition, in order to correlate the performance of the devices, the optical, surface morphological, and structural properties of the FCVA-grown ta-C films with different thicknesses (5 ~ 20 nm) deposited on the ITO anode are investigated in detail. The optimized ta-C film with a thickness of 5 nm deposited on the ITO anode had a sheet resistance of 10.33 Ω−2, a resistivity of 1.34 × 10−4 Ω cm, and an optical transmittance of 88.97%. Compared to the reference PSC with p-NiO HTL, the PSC with 5 nm thick ta-C HTL yielded a higher power conversion efficiency (PCE, 10.53%) due to its improved fill factor. Further, the performance of QDLEDs with 5 nm thick ta-C hole injection layers (HIL) showed better than the performance of QDLEDs with different ta-C thicknesses. It is concluded that ta-C films have the potential to serve as HTL and HIL in next-generation PSCs and QDLEDs.

Fatigue and Mechanical Behavior of Ti-6Al-4V Alloy with CrN and TiN Coating Deposited by Magnetic Filtered Cathodic Vacuum Arc Process

Coatings of 3 μm CrN and TiN were prepared by a magnetic filtered cathodic vacuum arc process (MFCVA) on Ti-6Al-4V substrates, respectively. Rotating bending tests and uniaxial tests were conducted for investigating the effect of the thin and uniformly distributed hard CrN and TiN coatings on the fatigue and mechanical properties of Ti-6Al-4V substrate. During both tests, no coating spallation phenomenon was observed, which indicated that the hard coating bound well with the substrate. The fatigue test results showed that the fatigue strength of the coated sample was decreased in both the low- and high-cycling fatigue regimes compared with the uncoated Ti-6Al-4V substrate. Compared with the TiN coating, the CrN coating caused a more significant reduction on the fatigue property of the uncoated Ti-6Al-4V substrate due to its inferior plastic deformation capacity. Furthermore, the tensile test results showed that the coated sample had a relative higher ultimate strength, yield strength, and lower elongation compared with the uncoated Ti-6Al-4V substrate. This may be due to the fact that the hard coating could suppress the initiation of cracks, and so higher stress was needed for crack initiating. During the crack propagation period, the hard coating cracked at a relative higher velocity, which led to cracking of the ductile substrate and elongation reduction.

Synthesis of Single-Layer ZrN-Coatings Using Vacuum-Arc Plasma-Assisted Deposition with Plasma Flow Filtering

The coatings based on ZrN are formed by the vacuum-arc plasma-assisted process under the conditions of plasma filtering from the droplet phase. A comprehensive investigation of the coating properties, elemental and phase compositions, and structure is performed by the methods of present-day materials science. The modes of deposition, at which the resulting coatings exhibit the lowest roughness (0.03 μm), the highest hardness (up to 30.5 GPa), a relatively low friction coefficient (0.39), and a low wear parameter (up to 2.2·10–6 mm3/(N·m)), are determined. Using the X-ray diffraction data, it is identified that the coatings consist of ZrN-crystallites with a cubic-lattice.

Study on transition process of vacuum arc under transverse magnetic field

The transverse magnetic field (TMF) drives the vacuum arc to move along the surface of the contacts to prevent the local overheating and melting of the contact surfaces. The arcing process has great influence on the breaking capacity of short‐circuit current. In this paper, the arcing process between three types of TMF contacts was investigated. The transition process of an arc from the ignition stage to the diffusion stage was discussed. The transition moment, transition gap distance, and transition current were obtained. It was found that the axial magnetic field component of TMF contacts affected the arc transition process.

Cylindrical hot refractory anode vacuum arc (CHRAVA)

We present a study of a novel vacuum arc deposition system composed of a water-cooled aluminum cathode and a hot refractory anode. The plasma of the arc system was diagnosed using a cylindrical electrostatic probe. It was found that the mean electron temperature was ∼2 eV, the plasma density could be varied in the range of 0.5-6 × 1016 m-3, and the ion flux was between 0.06 and 0.35 A m-2. Optical emission spectroscopy measurements showed the presence of emission lines corresponding to Al i and Al ii. The characterization of the coatings showed that the deposition rate varied from 0.8 to 4 nm/s and the surface roughness (Ra) of the films was as low as 25 nm. We demonstrated that it was possible to deposit films with low macroparticle densities, overcoming the principal disadvantage of the vacuum arc process. Measurements of the arc voltage and current were performed as a function of time and the applied magnetic field. The anode temperature was measured using a pyrometer through a ZnS window as a function of time and arc current, and the maximum value was 1800 °C with heating rates of up to 110 °C/s.

Surface Alloying of SUS 321 Chromium-Nickel Steel by an Electron-Plasma Process

The mechanisms of forming nanostructured, nanophase layers are revealed and analyzed in austenitic steel subjected to surface alloying using an electron-plasma process. Nanostructured, nanophase layers up to 30 μm in thickness were formed by melting of the film/substrate system with an electron beam generated by a SOLO facility (Institute of High Current Electronics, SB RAS), Tomsk), which ensured crystallization and subsequent quenching at the cooling rates within the range 105–108 K/s. The surface was modified with structural stainless steel specimens (SUS 321 steel). The film/substrate system (film thickness 0.5 μm) was formed by a plasma-assisted vacuum-arc process by evaporating a cathode made from a sintered pseudoalloy of the following composition: Zr – 6 at.% Ti – 6 at.% Cu. The film deposition was performed in a QUINTA facility equipped with a PINK hot-cathode plasma source and DI-100 arc evaporators with accelerated cooling of the process cathode, which allowed reducing the size and fraction of the droplet phase in the deposited film. It is found that melting of the film/substrate system (Zr–Ti–Cu)/(SUS 321 steel) using a high-intensity pulsed electron beam followed by the high-rate crystallization is accompanied by the formation of α-iron cellular crystallization structure and precipitation of Cr2Zr, Cr3С2 and TiC particles on the cell boundaries, which as a whole allowed increasing microhardness by a factor of 1.3, Young’s modulus – by a factor of 1.2, wear resistance – by a factor of 2.7, while achieving a three-fold reduction in the friction coefficient.

Arc development of triggered vacuum switch with multi-rod electrode system

Triggered vacuum switch (TVS) is one of the important switch apparatuses in the high pulsed power system, which takes the vacuum as insulation and arc-extinguishing medium of main gap. The conduction of TVS is the arcing process of vacuum arc in practice. So, it is meaningful to research on the vacuum arc characteristics for the high current application of TVS. A six-gap rod electrode system is studied in this paper. It is made up of 3 pairs of rod electrodes, i.e., spatially interleaved rods of opposite polarity on a ring. The arc development under different high currents is tested and discussed, based on the electrical characteristics of the vacuum arc voltage and arc resistance. The variety of arc voltage shows the parallel arcing and the transfer process in the multi-channel, which is benefit to maintain the diffusion of vacuum arc. A TVS sample based on multi-rod electrode has carried high current of 225 kA in peak and charge transfer of 45 C in a pulse.

Structural optimisation and synthesis of multilayers and nanocomposite AlCrTiSiN coatings for excellent machinability

In the present work, based on AlCrN coatings, AlTiSiN and AlCrTiSiN multilayer and nanocomposite coatings were designed and deposited on high-speed steel (HSS) specimens and cutters by cathodic vacuum arc process. The microstructures of these coatings were investigated by grazing incidence X-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and high-resolution transmission electron microscope (HRTEM), in association with mechanical property characterisation, and also with a cutting test used to check the service life of coated tools. The results showed that the AlTiSiN coating was composed of nanocrystalline TiN and hcp-AlN. The AlCrTiSiN multilayers and nanocomposite coating contained (111), (200), and (220) planes of TiN and CrN with a face-centred cubic structure (fcc) and nanocrystalline fcc-(Cr,Al)N phases. The AlCrTiSiN coating had a stronger diffraction (200) peak compared with the AlTiSiN coating. Those coatings were superlattice with nanocomposite structures containing nanocrystalline and amorphous phases. The modulation period (7nm) of the AlCrTiSiN coating was much smaller than the 12nm of AlTiSiN. A special Cr2N particulate phase existed in the AlCrTiSiN coating. The service life of an AlCrTiSiN coated tool increased by approximately 50% when compared with that with an AlCrN coating because of its excellent mechanical properties (41.14GPa hardness, 1.07GPa toughness, 60N LC2 adhesion strength, 0.2 average friction coefficient, and 36.5nm (Ra) roughness).