Droplet Erosion of a Cathode in a High-Current Vacuum Arc

Technical Physics Letters - It is shown that high-current vacuum arcs accompanied by partial melting of the cathode surface and its droplet erosion can generate, in addition to the well-known...     

Development of a High-Current Vacuum Arc in a Rod Electrode System

The development of a high-current pulse electric discharge in a rod electrode system with the current amplitude changing from 10 to 100 kA is investigated using a sectional model of a vacuum chamber with the simultaneous recording of the electrical characteristics of the discharge, of the glow of discharge plasma, and of the spots on the electrodes. A phenomenon is revealed of a rapid transition of the discharge from the ignition unit to interrod gaps on reaching an instantaneous value of current from 5 to 9 kA. A correlation is established between the moment of appearance of an abrupt drop of voltage across the vacuum arc and the moment of formation of a new discharge channel in the interrod gap. It is demonstrated that various vacuum arc modes in the interrod gap and the multiplication of discharge channels in all interrod gaps are observed with increasing current. The effect of the rate of current increase on the development of the vacuum arc is investigated.     

Effect of the Angular Distribution of Cathode Ions on the Current Flow in a High-Current Vacuum Arc

The effect of the angular distribution of cathode ions on the parameters of a vacuum arc is investigated. It is shown that, at current densities characteristic of a high-current arc, collisions of flows of fast ions from different cathode spots may result in a high value of the ion temperature at the cathode plasma boundary. The boundary in current density of the region of a stable current flow as a function of the width of angular distribution of cathode ions is determined. It is found that, in the region of supersonic flow of ions, the permissible value of the current density drops rapidly as the angular distribution width increases, and in the subsonic region, it rises rapidly. An expression is obtained for the maximum possible ion sound velocity and for the equivalent critical ion velocity. Two- and three-fluid hydrodynamic models are used to perform calculations that illustrate characteristic distributions of parameters in the discharge gap. Analysis of the calculation results makes it possible to discuss the characteristic features of current flow in a vacuum discharge.     

纳米TiN颗粒在真空电弧反应中沉降的临界条件及其表征

研究了在真空电弧镀膜设备中产生纳米 Ti N颗粒沉降的临界条件。结果表明 ,当真空度P>8.7× 10 - 1 Pa,即 Knudsen数 Kn>110时 ,工作台中心几乎不能沉积 Ti N薄膜 ,而在真空反应气氛中有大量纳米 Ti N颗粒形成。增大反应气体的压力和提高负偏压 ,都可以进一步细化 Ti N颗粒。用 SEM和 XRD等测试方法对颗粒的形貌及结构进行了研究 ,在实验条件下纳米 Ti N颗粒的平均尺寸为 2 8～ 35 nm,其中有少量的 Ti颗粒存在     

真空电弧沉积技术中的弧源设计

讨论了真空电弧沉积中弧源设计的有关问题 ,如电弧运行模式、电弧极性、点火方式、电弧的约束方式以及宏观粒子抑制方式等。分析表明 ,合理选择电弧运行模式和电弧极性 ,以满足涂料粒子蒸发与离化的要求 ;选择合适的弧源结构 ,加强对电弧的约束与烧蚀的控制 ,或用过滤弧源 ,以抑制宏观粒子对涂层的污染 ,是成功设计弧源的关键     

电子式真空阴极弧离子镀引弧器的研制

研制了电子式真空阴极弧离子镀引弧器 ,分析了其工作原理及工作时序 ,给出了它的关键部分的电路 ,介绍了它的离子镀引弧器的性能及特点。     

真空阴极弧离子镀阴极斑点的移动研究

建立了真空阴极弧离子镀圆形平面靶侧面引弧时 ,阴极斑点的受力模型 ,分析了影响电弧运动的因素 ,改进了圆形平面靶侧面形状 ,大大提高了石墨靶阴极斑点从侧面到靶平面的过渡速度     

真空电弧放电稳定性

本文研究了真空阴极电弧放电过程中阴极电弧源工作稳定及其影响因素,研究了真空电弧斑的产生及运动规律。     

Cathode Spots of Vacuum Arc Discharges

Vacuum arc discharge is used for formation of pure metal and complex combined coatings, and also for the impact of the discharge on a surface to remove superficial contaminants. Physical processes observed in an arc discharge are mostly determined by the behavior of cathode spots, which are fundamentally unstable plasma formations and are characterized by a certain value of average lifetime. Reliable stabilization of the cathode spots and controlling their movements on the working surface grants the technology a grater importance in application.     

真空电弧炉动密封的设计及计算

介绍了宝鸡有色金属加工厂设计研制所自行研制的650 kg真空电弧炉和1 t真空电弧炉真空系统与炉室连接处的动密封结构、原理及其计算方法,在类似设备中可作参考.     

The Effect of External Magnetic Field on a Vacuum Arc

The effect of an external longitudinal magnetic field on the time required for anode spot formation in a high-current (5 to 12 kA) vacuum arc is experimentally studied, and the minimal value of a magnetic field inhibiting the anode spot formation is determined. The experimental results are compared with theory. The phenomenon of break of current in a low-current (100 to 300 A) vacuum discharge upon superposition of a magnetic field with transverse component on the discharge is investigated. The probability of break of current increases with the magnetic field. The possible mechanism of break of current is discussed.     

Anode Mode of Vacuum Arc in a Multirod Electrode System

The effect of the plasma of a high-current vacuum arc on the anode rods in a rod electrode system, which leads to the melting of the surface of copper anode rods and to the formation of droplets of the electrode material, is investigated. High-speed photography is used to register the formation of anode spots, and the sizes of the spots are determined at discharge currents from 30 to 100 kA. A one-dimensional nonstationary model of the melting of the anode and of the formation of droplets in the anode spot of a vacuum arc is proposed. The model is in satisfactory agreement with the results of observation of traces of melting on the anodes of used dischargers in a rod electrode system and with high-speed photographs of glow of the discharge plasma and spots on electrodes in a model of the rod electrode system.     

铝合金微弧氧化电流密度的临界条件研究

为了改进微弧氧化能耗高、处理效率低的问题,以6061变形铝合金为试验材料,2%磷酸盐溶液为导电介质,在25 ℃下,利用MAO200/750微弧氧化设备对微弧氧化的电流密度和起弧时间、起弧电压和试样面积、起弧电压与占空比以及起弧时间与占空比等之间的关系进行了研究.结果表明:本工艺条件下,铝合金微弧氧化的临界电流密度为0.2 A/dm2;起弧电压随试样面积的增加而呈正比增加;起弧时间随着占空比的减小而缩短;占空比越小,起弧电压越高.     

Technological Capabilities of Vacuum Arc Plasma Sources

Vacuum arc plasma sources based on the self‐maintained discharge developing in the cathode material vapor enable plasmochemical synthesis of nitride and carbide compounds. Reactive gas is injected in the metal plasma flux to implement the plasmochemical synthesis of compounds. By controlling the plasma flux parameters and taking into account the ion current density distribution in the active volume, properties of the formed coating may be managed. The development of plasma technology leads to possibility of fine controlling of gas pressure and reactive gas composition, degree of plasma flux focusing, flux separation from the drop fraction. If the plasma flux is free of droplets the composition and structure of a coating can be effectively controlled by varying technological parameters.     

Cathode Drop of the Potential of a Vacuum Arc of Metals

The basic mechanisms of ionization in the cathode spot of a vacuum arc are considered. It is shown that the singly charged positive ions formed here are a result of the collision ionization of the evaporated atoms of a metal by electrons. On this basis the assumption is made that the cathode drop of the potential of the vacuum arc of metals is determined by the energy of ionizing electrons at which the ionization section attains its maximum.     

真空触发开关的起弧稳定性分析

真空触发开关(triggered vacuum switch,TVS)是大功率脉冲技术领域的重要开关器件之一,它具有结构紧凑、介质恢复迅速、操作无噪声、工作可靠性高、环境适应性强等优点,在中压领域具有广泛的应用前景.TVS的开通过程本质上是电弧燃烧过程.针对TVS的起弧稳定性,搭建了一套场击穿型TVS的触发和实验系统,从电气特性和图像特性两个方面记录其起弧过程.实验和理论分析表明,触发系统的稳定延时大约40μs,起弧过程持续297μs左右;初始等离子体的不同发展决定着TVS的开通.只有充足的初始等离子体,才能产生一定的鞘层电压,从而不断产生新的阴极斑点,保障起弧的稳定性.     

Vacuum Arc Discharge on Integrally Cold Cathode

Initial researches of the existence of a cathode spot on the working surface were conducted in vacuum arc plasma sources of the coaxial design. The moving of the cathode spots on the limited sizes working surface does not give full picture of the development of the arc discharge. This article describes the vacuum arc plasma source of extended design generating the directed belt plasma stream and operating in pulse mode. The researches carried out give additional information about development of the cathode spots of the vacuum arc discharge. It is found that the speed of the cathode spots' motion depends on the cathode temperature.     

A Stationary Vacuum Arc with a Diffuse Spot on a Nonemitting Chrome Cathode

The results are given of experimental investigations of a stationary vacuum arc with a diffuse spot on a hot cathode of solid chrome in the current range from 20 to 220 A. The characteristics of the discharge are compared to those of a similar discharge on a thermionic gadolinium cathode. It is demonstrated that, in the case of a chrome cathode, mechanisms such as the thermionic emission, ion-electron emission, and photoemission are incapable of ensuring the charge transport on the cathode surface. Our results complement the experimental data obtained by other authors in investigations of arcs of this type and thereby contribute to clarifying the mechanism of charge transport on the surface of a chrome cathode.     

钛合金真空自耗电弧熔炼技术发展

目前,生产钛及钛合金铸锭的基本方法仍为真空自耗电弧熔炼方法.讨论了真空白耗电弧熔炼钛合金的常见铸锭缺陷和预防措施.回顾了近代真空自耗电弧熔炼(VAR)技术的发展.较详细地介绍了为获得更高质量的铸锭,当前对VAR熔炼过程控制技术所作的努力及取得的进展.指出了未来真空自耗电弧熔炼控制技术的发展方向.