Vacuum Arc Discharge Research Articles

Вольт-амперные характеристики начальной стадии дугового разряда в высоковольтном вакуумном диоде

AbstractThe process of electron instability development and propagation of a cathode electron beam and anomalous ion beam, followed by outburst of current in the initial stage of arc discharge was observed in rarefied plasma cloud of high-voltage vacuum diode. These events are consistent with the model of anomalous ion acceleration in interelectrode plasma at the spark stage of vacuum arc discharge.

Vacuum Arc Plasma Heated by Sub-Terahertz Radiation as a Source of Extreme Ultraviolet Light

This paper presents the results of the first experimental studies of the interaction of a powerful sub-terahertz radiation with expanding highly inhomogeneous plasma of vacuum arc discharge. The tantalum plasma of a vacuum arc discharge additionally heated by the focused sub-terahertz radiation of a gyrotron, the radiation power is up to 250 kW, and the wavelength is 1.2 mm. Characteristics of the light emission in the extreme ultraviolet range are presented.

Structure and Microporosity of Ion-Plasma Condensed Coatings Deposited from a Two-Phase Vacuum-Arc Discharge Plasma Flow Containing Evaporated Material Microdroplets

The structure of “thick” (up to 100 μm) condensed ion-plasma multicomponent coatings deposited from a two-phase vacuum-arc metallic plasma flow containing “liquid” and “solid” microdroplets of an evaporated material has been studied. The structure of the coatings is shown to be dependent on the operating conditions of the vacuum-arc evaporator cathode (radiative or forced cathode cooling), the evaporator current, the bias voltage, and the substrate temperature. The existence of solid microdroplets of the evaporated material in a plasma flow leads to the formation of growth defects in the condensate and, hence, open microporosity in the coatings. A number of techniques, which enable a significant decrease in the microporosity of the ion-plasma coatings, have been proposed.

Experimental Study of the Accelerator of a Pulsed High-Current Radially Converging Electron Beam

A new cylindrical electron accelerator with a revised design (1-m long cathode, new plasma cathode concept) was built and a first experimental study of its operation was performed. The cathode plasma is generated by uniformly distributed vacuum-arc discharge gaps and its expansion is limited by a stabilizing grid. From the timescale of cathode plasma formation, a plasma temperature of about 40 eV is estimated. Electrons are emitted from the cylindrical cathode and radially accelerated toward the tube anode located along the accelerator axis. Due to the small anode radius of only 0.5 cm and the rather large azimuthal velocities of the electrons at emission, about 20% of the beam electrons miss the anode and circulate in the accelerator volume. This process significantly increases the current to the control grid of the triode-type accelerator at the expense of a reduced current delivered to the anode. The effect of circulating electrons is much less pronounced for an anode with radius 1 cm.

Research and development of anti-adhesive coatings deposited by vacuum-arc discharge plasma

In works devoted to the view of resistance against adhesion, as protective coatings of a coating based on zirconium (ZrN), since Zr has the least tendency to interact with an aluminum melt. A new technique for the quantitative determination of the adhesion of anti-adhesion coatings has been developed. On the basis of experimental data, it was found that among the selected types of coatings, the best result, from the point of view of enhancing the properties against adhesion, was a coating of zirconium nitride.

Evolution of structure and phase composition of vacuum plasma coatings alloyed by aluminium

The paper presents the investigation results of the structure and properties of coatings deposited from separated vacuum-arc discharge flows based on TiN alloyed with aluminum. The influence of the coatings elemental composition on the structure, phase composition and their mechanical properties was established. It is determined that coatings containing in the hexagonal phase Ti3Al2N2 are characterized by high hardness, low friction coefficient, maximum values of elastic recovery and plastic deformation resistance.

15th International Scientific and Technical Conference Rapid Solidification Materials and Coatings (RSMC-2018)

A A Lozovan1 and D K Kostrin21 Department of Materials and Materials Technology, Moscow Aviation Institute (National Research University) “MAI”, 121552, Orshanskaya, 3, Moscow, Russia2 Department of Electronic Instruments and Devices, Saint Petersburg Electrotechnical University “LETI”, 197376, Professora Popova, 5, Saint Petersburg, RussiaE-mail: alexandr.lozovan@yandex.ru. This review discusses the key features and main results of the 15th International Scientific and Technical Conference Rapid Solidification Materials and Coatings, which took place on October 16–17, 2018 in Moscow.Figure 1. Working sessions of the Conference.Plenary reports of the Conference were devoted to theoretical and practical aspects of rapid solidification, surface modification and coatings deposition technologies. The issues of development of technologies and equipment for vacuum-plasma surface modification for the creation of highlyreliable precision friction units of a new generation, the laws of carbon fiber surface corrugation by high-dose ion irradiation, the study of the structure of magnesium alloys obtained by rapid solidification of the melt on a rotating heat sink were discussed. Reports on the analysis of materials under ion-beam excitation of X-ray fluorescence and the study of nanostructured gradient coating with an upper layer of hafnium oxide aroused great interest.In a number of reports new variants of magnetron sputtering systems were presented, including inverted, the characteristics and principles of coatings deposition on their basis were given, including the application of composite multi-layer coatings on substrates of complex shape. Thermal processes in hot-target magnetron assemblies and conditions of operation of the magnetron with a sandwich target were discussed. A number of reports were devoted to the study of the parameters of oxide layers formed by plasma-electrolytic oxidation.Considerable attention was paid to reports on the use of vacuum-arc discharge for the application of wear-resistant coatings, as well as ion-plasma modification of various carbon materials, in particular – modification of carbon fabric Busofit T-040. The features of graphite erosion under high-temperature ion irradiation were presented.In part of the reports on improving the efficiency of metallurgical technologies, the processes of high-temperature interaction of the liquid metal phase with the surface of a solid body and solid-phase interaction in the creation of metal-ceramic composites were considered.Great interest of participants was aroused by the reports on the analysis of layered inhomogeneous samples by spectroscopy of reflected electrons and modeling the generation of flows of neutral atoms in the channel rays of the glow discharge.Figure 2. Summing up the results of the 15th International Scientific and Technical Conference Rapid Solidification Materials and Coatings.In summing up the results of the conference (figure 2), the participants noted the high level of reports on topical issues of the formation of physical and physico-chemical methods of surface layers of products with desired properties, the creation of industrial equipment and the development of new technological processes. Thus, the 15th International Scientific and Technical Conference Rapid Solidification Materials and Coatings (RSMC–2018) contributed to the further development of this scientific and applied area of research and expansion of professional relations of the participating scientists.

Radiographic Investigation of Metal-Puff Plasma Jets Generated by Vacuum Arcs

The structure of the plasma jet of a vacuum arc discharge was investigated using different experimental arrangements for jet formation. To examine the external shape and internal structure of the plasma jet, optical imaging and pulsed X-ray radiography were used. The latter is the most informative method for investigating the density distribution in a dense plasma jet. This diagnostic, combined with a step wedge, provides a way of analyzing quantitatively the plasma jet structure. As the X-ray source for radiography, an X-pinch was used. The measured surface density of an aluminum plasma jet ranged up to $340~\mu \text{g}$ /cm2. The arc discharge current and the plasma jet current were measured with Rogowski coils. The experiment has shown that in the case of a plasma gun with return current posts; a pinch effect arises which provides for the formation of a confined plasma jet.

Generation of High-Intensity Aluminum-Ion Beams at Low Energy

High-intensity repetitively pulsed beams of low-energy aluminum ions are generated in experiments. A continuous vacuum–arc discharge is used as a generator of metal plasma. Aluminum-ion beams with a current density of up to 0.47 A/cm2 are generated owing to the plasma immersion extraction of ions with subsequent ballistic focusing in the drift space of potential electrodes. Regularities of the generation of high-intensity ion beams are studied at a pulse repetition rate of 105 pulses per second versus bias voltage ranging from 1.2 to 3 kV, pulse duration ranging from 2 to 8 μs, and residual gas pressure. Transport efficiency and beam focusing are determined by the conditions for neutralization of the space charge. Even under complete filling of the drift space with preliminary injected plasma, the conditions for neutralization of space charge are dynamically varied due to an increase in the space charge upon ballistic focusing. Experimental results are presented to prove formation of a virtual anode under conditions for insufficient plasma injection in the drift space of the beam. It is shown that the transport efficiency of the high-intensity beam may substantially be increased in the presence of argon in the experimental chamber.

Two-dimensional electron density visualization over plasma flare in vacuum breakdown process

Spatiotemporal evolution of plasma flares in a vacuum breakdown process was characterized by various optical techniques including Shack-Hartmann type laser wavefront sensors for two-dimensional electron density imaging, high-speed framing photography for speed determination of flare expansion, and optical emission spectroscopy for plasma composition assessment. The experimental results showed that the plasma flares with high electron densities of 1025 m−3 and gas temperature of 2 eV were initiated on the copper anode and expanded to the vacuum gap with a propagation speed of 6 × 103 m/s. Subsequently, the electron densities in the anode flare tips demonstrated a drastic decrease in a short time scale of 50 ns due to a three-body recombination reaction. The anode flare tips combined with the cathode plasma flares initiated on the copper cathode, and the conductive plasma channels containing flare-induced copper vapor were established in the interelectrode gap. In the final stage of the vacuum breakdown, the copper-vapor-contaminating plasmas were deconstructed and they transformed into the vacuum arc discharges.

Formation of coatings from the flow of metal plasma of a vacuum-arc discharge

Modification of the surface properties of a material or application of a protective coating are the most effective ways to improve the service life and reliability of parts. For the production of coatings vacuum-arc discharge with integrally cold cathode is widely used. The advantages of this method are high degree of purity of the coating, the possibility of changing the structure of the coating and obtain complex multicomponent coatings. In this paper, we consider the production of anti-emission coating based on titanium; the results of metallographic studies of this coating are presented.

Application of a vacuum-arc discharge for the production of biocompatible coatings

Vacuum-arc discharge is an effective method of forming pure metal and metal-like coatings of complex composition. In this paper, the possibility of its use for the production of biocompatible coatings on the example of synthesis of titanium nitride and titanium carbide on metal substrates is evaluated.

Improvement of performance properties of products by surface treatment of materials with cathode spots of vacuum arc discharge

It is shown that the impact of cathode spot of vacuum-arc discharge on the plastically deformed surface may be partially or fully recovered her form. This effect was detected during vacuum-arc cleaning of the inner surface of the cylinder. Mathematical and experimental modeling of the process of restoring the inside diameter of the cylinder confirmed the effect of shape recovery upon exposure of the cathode spots of a vacuum arc on the surface.

Improving the adhesive strength of the babbit layer of sliding bearings

The possibility of increasing the adhesion of the babbit coating applied by means of casting on the bearings inserts by preparing of the surface of the bearings inserts by processing with help of cathode spots of vacuum arc discharge is shown. At the same time, the vacuum purity of the surface is provided and a roughness with a partially-regular micro relief is created. In addition, it is possible to increase the adhesive properties of the coating by applying a vacuum arc method of deposition of a thin sublayer of the coating material.

Investigation of physical and mechanical properties of coatings based on intermetallics of the Ti-Al system obtained in acetylene environment from vacuum-arc discharge plasma

At the present time, protective coatings have found wide application in various branches of industry: mechanical engineering, aircraft engine building and also in the tool manufacture. In this work presented the results of the researches of the physico-mechanical properties of coatings based on the intermetallics of the Ti-Al system, obtained in the acetylene environment from vacuum-arc discharge plasma. The thickness, microhardness, and phase composition of the coatings were investigated when samples were placed at various distances from the table axis and rotation speeds.

Influence of intermetallide coatings on the high-temperature corrosion resistance of martencite steel in various structural conditions

The effect of coatings deposited from a vacuum-arc plasma on the high-temperature corrosion resistance of martensitic steel in ultrafine-grained and coarse-grained state is studied. It is proved that coatings obtained from a vacuum-arc discharge plasma increase the high-temperature corrosion resistance of martensitic steel. The analysis of high-temperature corrosion resistance was carried out using the method of accelerated cyclic tests developed by the All-Russian Institute of Aviation Materials

Plasma diagnostic and microstructural study of WCN coatings growth by pulsed vacuum arc discharge

In this work, we present a study of the plasma evolution during tungsten carbon nitride (WCN) coatings production using the repetitive pulsed arc technique. For the coatings production, a tungsten carbide (WC) target, and a mixture of argon and nitrogen as the filled gas were used. The study was carried out for discharges generated with one, two, three, and four pulses. The WCN coatings were characterized by X‐ray diffraction (XRD) to identify the phases present in this material. The plasma was experimentally studied by optical emission spectroscopy (OES). A correlation was found between the spectral lines behavior and the material composition evolution. As the number of pulses increased, the intensity of the spectral lines also increased, especially in the case of the atomic lines of nitrogen, NI. The results were analysed to obtain information regarding the reactions in the plasma, as well as the electron temperature and density.

Depth profiling of titanium nitride thin films deposited on stainless steel utilizing combined EBS and NRA techniques

Abstract Composition and depth profiling of titanium nitride thin films deposited on stainless steel using vacuum arc discharge device have been determined. A combination of two ion beam analysis techniques has been applied to allow accurate quantification of nitrogen in the prepared titanium nitride thin films. These include elastic backscattering (EBS) spectrometry together with nuclear reaction analysis (NRA) technique utilizing 14N(α,p0)17O nuclear reaction, both performed at resonance energy for incident alpha beam of 4500 keV. They were applied simultaneously, using two independent charged particle detectors, one is dedicated for combined EBS/NRA measurements and the other for pure NRA one. Experimental conditions have been carefully optimized to avoid overlapping of peaks of the two spectra correspond to each reaction. Novel Multi-SIMNRA software has been utilized to enable simultaneous elemental depth profile determination of both data sets. Experimental setup of the in-vacuum system has been carefully characterized. Independent complement measurements utilizing scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX) were also applied to verify the experimental findings obtained by combined EBS and NRA techniques. The results have revealed N/Ti ratio of around 1 for the prepared films, with low levels of contamination elements. Finally, X-ray diffraction (XRD) measurements have demonstrated TiN structure with low oxygen contamination.

Modification of the surface layers with plasma of a vacuum-arc discharge by controlling the energy of precipitating particles

In this paper we consider one of the most effective ways to improve the performance properties of metals – their treatment by intense flows of metal plasma generated by a vacuum-arc discharge. The change in the thermal regime and the duration of the plasma treatment allows controlling both the thickness of a modified layer and the distribution of implanted ions into its depth. At the first stage of part processing the preliminary cleaning of the surface is carried out using a glow discharge in argon. In the second stage, vacuum-arc plasma sources are used, that provide surface treatment with ions of the sprayed material. To weaken and purify the plasma flow special separation systems were used to ensure the creation of an impassable barrier for the droplet fraction. Modification of the treated surface layer is achieved either due to the high energy of the deposited particles, or due to the implementation of the diffusion processes deep into the substrate. The presence of a modified surface layer allows improving the quality of the working coating that is deposited further.

On the Fractality of Microparticles from the Plasma Flow of a Vacuum Arc Discharge

Structures, namely, powder and films, deposited onto vacuum-chamber walls from low-temperature vacuum arc discharge and tokamak plasma are investigated. The fractal parameters of the given structures are compared. The possible mechanisms of their formation are discussed.