Surface processing by arc discharge in vacuum. RU patent 2509824.
 Method of processing part surface by arc discharge in vacuum and device to this end / 2457282Proposed method comprises exciting the discharge, processing the surface by vacuum arc cathode spots and displacing them along processing area. Note here that arc cathode area is displaced along processing area by varying current strength via negative potential current leads connected to two and more points of processed surface with concurrent continuous or discrete relative displacement of positive electrode and processed surface. Proposed device comprises arc supply source, positive electrode and processed article placed in vacuum that makes cathode. Note here that negative potential current leads are connected to processed surface at two and more points via current controller. |
| Method of removing organic residue from piezoelectric substrates / 2406785 Method involves evacuation and treating substrates in oxygen-containing plasma. Substrates are treated in a plasma mixture of oxygen and inert gas containing 5-12 vol. % oxygen and 88-95 vol. % inert gas. The inert gas is helium, neon or argon and treatment is carried out at temperature in the reaction chamber equal to 80-140 Pa, radio-frequency power equal to 0.02-0.06 W/cm3 and exposure time of 3-15 minutes. |
 Method for surface cleaning of large-size metal items with arc discharge and device for its realisation / 2374046Method and device are related to the field of cleaning and treatment of surfaces in large-size metal items in vacuum and in atmosphere of protective gases at various stages of technological process and make it possible to expand functional capabilities of arc discharge cleaning of surface in metal items of any large dimensions. Method includes vacuum pulling or creation of protective atmosphere in vacuum chamber, excitation of electric discharge between one or several electrodes arranged in vacuum chamber, and cleaned surface of item, and movement of cathode spots along cleaned surface of item with the help of created magnetic field of various configuration. Vacuum chamber is made in the form of box, and vacuum is pulled in its volume, surface of covered section is cleaned with arc discharge in vacuum, and in process of treatment box is gradually moved along surface of large-size item. Device comprises vacuum chamber, system of vacuumising or vacuum chamber filling with protective gas, electrodes arranged inside vacuum chamber, electromagnetic coils for arcs displacement along cleaned surface of item, vacuum chamber is arranged in the form of box with open part with the possibility of its gradual tight application onto cleaned sections of large-size item and is equipped with a pressurising device along perimetre of box open part, mechanism or accessory for box movement along surface of cleaned large-size item in process of its treatment, at the same time pressurising device is made in the form of suction cap or combination of suction caps equipped with a system of air pumpdown from them. |
| Method of removing rust from surfaces / 2361708 Thermite type mixture with layer thickness of 1.5-4.0 mm is put onto a processed surface. Combustion of the mixture is initiated. As a result of exothermal reaction, the reducing agent of the mixture reacts with rust. During the redox reaction, a large amount of heat energy is released, which provides for burning, including organic compounds on welding surfaces. The surface of the component is reduced to pure iron. |
| Method of electroarc surface treatment of metal works / 2355520 Invention relates to electroarc surface treatment of metal works in vacuum and can be used in ferrous and non-ferrous metallurgy, and also in machine building branch of productions. Method includes location of product in vacuum chamber, feeding on it negative potential, electrode installation over the product surface, on which it is fed positive potential, stimulation between them voltaic arc and movement of product relative to electrode or the electrode relative to product. In vacuum chamber it is created pressure in the range 10 - 10-3 mm column of mercury, it is installed interelectrode distance between the electrode and the nearest point of the product surface in the range 2.0 - 70.0 mm, which corresponds to the length of mean free path of arc plasma with mentioned range of pressure in vacuum chamber, and it is kept electric arc and specified interelectrode distance during the process of all the treatment of product's surface. |
| Method for electroarc cleaning of metal product surfaces / 2347010 Invention is related to the field of metal products cleaning, such as rolled wire, wire, strip, forged pieces, foundry and others, in particular, to method for electroarc processing of metal products surfaces and may find application in different branches of machine building industry. Prior to arc discharge treatment, surface is previously coated by thin layer of alkaline, alkali-earth or rare-earth metals or their compounds in process of hot processing or in cold condition. Prior to processing, at atmospheric pressure processed surface is previously coated by material, which is gasified by cathode spots of arc, creating protective or restorative medium above cleaned surface. Result achieved is considerable reduction of metal products processing cost, higher efficiency of processing and lower heating of processed product metal. |
 Application of antifriction wear-proof coat on titanium, alloys / 2502828Proposed method comprises pre-cleaning and activation of titanium alloy surface by bombardment with argon ions using gas plasma generator and ion plasma deposition of composite coat by magnetron sputtering of cathode containing titanium carbide and molybdenum disulfide combined with application of negative potential to the article, deposition and bombardment being combined as well. Coat is deposited on pre-doped surface layer of titanium alloy formed by magnetron sputtering of cathode material combined with application of negative potential exceeding that used at coat deposition. Initial ratio of sputtered cathode material is as follows: titanium carbide - 40-60 wt %, molybdenum disulfide making the rest. |
 Method for obtaining single-phase titanium nitride films / 2497977Pre-cleaning of a substrate by ionic bombardment in a glow discharge in argon atmosphere is performed at the temperature of 45-50°C during 10-15 minutes. A submicron film is formed of two components: TiN and Ti in vacuum by electric-arc sputtering of a titanium target in reaction gas-nitrogen atmosphere. The obtained submicron film is subject to bombardment with nitrogen ions at displacement on the substrate of up to - 600 V and temperature of 50-60°C during 15-20 minutes. |
| Method of ion-bombardment processing of compressor vanes made of nickel-based high-alloy steels and alloys / 2496910 Proposed method comprises creation of required vacuum by turbo molecular pump, ion purification by argon ions and ion-bombardment of part surface by nitrogen ions. Vacuum is created to 10-5 to 10-7 mm Hg. Ion purification is performed at energy of 8 to 10 keV, current density of 130 mA/cm2 to 160 mA/cm2 for 0.3 to 1.0 h. Said ion-bombardment of part surface is carried out in either continuous or pulse mode at 25 to 30 keV in dose of 1.6·1017 cm-2 to 2·1017 cm-2, at dose accumulation rate of 0.7·1015 s-1 to 1·1015 s-1. |
 Application method onto metal part of complex coating for protection of part against hydrogen corrosion, which consists of many microlayers / 2495154Method involves degreasing of a part, arrangement of a part in a vacuum chamber, pumping of the chamber till vacuum, pre-cleaning in inert gas medium, ionic cleaning/etching of surface, deposition of layers by condensation with ionic bombardment and cooling in vacuum, and then, in inert gas medium. The part is arranged at a flow focusing point of at least two vacuum arc plasma sources. Pre-cleaning is performed in environment of ionised inert gas. Ionic cleaning/etching of surface is performed by supplying to a substrate first of voltage in the range of 200-500 V; and then, it is smoothly or step-by-step increased to 1-1.5 kV. At that, for application of the coating microlayers there used are alloys on the basis of combinations of metals chosen from the group of Cr, Ni, W, Nb, Zr, Ti, Al, Mo by their simultaneous sputtering at the part rotation. |
| Method of applying sandwich coatings on substrate / 2492276 Coating is applied on substrate of high-carbon steel in atmosphere of inert gas. First, substrate surface is cleaned by the flow of inert gas ions in condensation process with ion bombardment (CIB) at 550-600°C. Nickel coating is applied by CIB process at 550-600°C. The, said coating is annealed at temperature increase to 650-700°C and chromium carbide coat is applied. |
 Method for obtaining wear-resistant coating based on intermetallic compound of ti-al system / 2489514Treated part is arranged in a vacuum chamber of the plant containing a plasma source with an incandescent cathode and two electric arc evaporators in the form of cathodes from aluminium and titanium, which are located in one plane opposite each other. Ionic cleaning of the part surface with the plasma source with the incandescent cathode and ionic cleaning with the electric arc evaporator in inert gas medium is performed at heating of the surface to the temperature of 300-350°C. Titanium underlayer is applied to surface of the part by means of a titanium cathode. A layer on the basis of intermetallic compound nitride of Ti-Al system is applied by means of two cathodes. A layer on the basis of intermetallic compound of Ti-Al system is applied by means of two cathodes. Application of the coating layers is performed at assistance with the plasma source with the incandescent cathode. At application of the layer based on intermetallic compound, the change of its phase composition is performed by changing the position of the treated part in the vacuum chamber. |
 Ion implantation method of surfaces of parts from structural steel / 2482218Method involves implantation into the steel surface of copper ions, and then lead ions. Prior to the implantation, the part surface shall be treated with a laser beam that is focused at the spot in the form of a circle with specific emission density of 260-800 W/mm2; after that, the spot is moved along the treated surface at the speed of 25-40 mm/s. |
| Method of and device for coating of substrates / 2468120 At least one substrate is loaded into a vacuum chamber. The vacuum chamber is closed and exhausted. The substrate is cleaned by introduction of a gaseous reducing agent into the chamber. The substrate surface is increased by deposition of a vapour-like component on it, which is preferably identical to a substrate material. The coating is applied by the method selected from the group of processes of plasma hardening, physical deposition from a gas phase and processes of spraying, at the same time one or more metals or their oxides are applied onto the substrate surface. The chamber is filled with air, and the coated substrate is withdrawn from it. |
| Method of processing part surface by arc discharge in vacuum and device to this end / 2457282 Proposed method comprises exciting the discharge, processing the surface by vacuum arc cathode spots and displacing them along processing area. Note here that arc cathode area is displaced along processing area by varying current strength via negative potential current leads connected to two and more points of processed surface with concurrent continuous or discrete relative displacement of positive electrode and processed surface. Proposed device comprises arc supply source, positive electrode and processed article placed in vacuum that makes cathode. Note here that negative potential current leads are connected to processed surface at two and more points via current controller. |
| Method for vacuum ion-plasma coating application / 2451770 Invention relates to mechanical engineering, in particular, to methods for vacuum ion-plasma coating application, and can be used for applying coating to details of a difficult configuration. The method includes creation of potential drop between a detail and a cathode, cleaning of the detail surface by ion current, lowering of the potential drop and coating application, and annealing of the coating by means of increasing potential drop. After annealing, the detail is cooled to the indoor temperature, placed into a furnace and subjected to homogenising annealing in vacuum environment. The ion current and evaporating material current coming from the cathode to the detail are exposed during cleaning. Cleaning is done by noble gas ions, after cleaning shields are withdrawn and coating is applied while the detail is rotating on its axis. Cleaning, coating application and annealing are done within one cycle, and homogenising annealing of the coating is done stepwise at T=100±5, 340±10, 730±10 and 900±50 °C in vacuum 1·10-3 mm Hg. |
 Precision bearing washing machine / 2492002Invention relates to machine building, particularly, to production of precision bearings. Cavitation washing efficiency is upped by modification of activator that excited resonance oscillations consisting in making the activator mirror composed of alternating equidistant ring-like stiff and retarded shifting elements. Delay of shifting elements in activator oscillations creates vertical layer-by-layer shift of washing fluid to up the cavitation effect. |
 Method of treatment / 2447958Invention relates to degreasing surfaces and cavities by solvents, preparing to high-sensitivity tightness tests, and may be used in space engineering, aircraft engineering, instrument making, etc. Proposed method comprises placing rocket to be cleaned on rotary device to revolve rocket body about horizontal lengthwise axis, filling rocket tanks partially with solvent to revolve the rocket about said horizontal axis. Rocket body bottom zone in contact with solvent is heated while surface of tanks is cooled. Proposed method differs from prior art in that MINIMUM amount of solvent Ms makes where CF is initial (before cleaning) mean-statistical specific amount of soluble impurities on inner surface of tanks, kg/m2; CFtol is tolerable residual amount (after cleaning) of soluble impurities, kg/m2; F is total area of inner surface of tanks, m2; δ is mean thickness of solvent film on aforesaid said inner surfaces in cleaning tanks, m; pv,pf are densities of vapor and fluid phases of solvent in cleaning, respectively, kg/m3; V is free inner volume of tanks, m3, while linear rotational speed of rocket cylindrical shell about axis is set to allow evaporation per unit time of maximum amount of solvent Gmax(kg/s): where v is linear rotational speed of rocket cylindrical shell about axis, (m/s); λ is factor of heat transfer from shell outer wall to solvent, kJ/m2 s K; tSMmax is maximum tolerable temperature of tank structural material heating, °C; Fc is total area of contact of solvent with tank inner surface, m2; r is solvent specific evaporation heat, kJ/kg; cSM is heat capacity of rocket tank material, kJ/kg K; ts is solvent temperature in tank necessary for efficient washing effect, °C; tH is tank shell temperature in area not in contact with solvent ( equal to ambient temperature), °C; A is mean thickness of tank shell, m; V is linear speed of tank wall rotation, m/s; L is tank cylindrical section length, m; ρsm is density of tank structural material, kg/m3. |
 Method of deactivating solid organic substrate contaminated with solid radioactive dispersed inorganic contaminants using densely compressed co2 / 2423191Invention relates to a method of removing radioactive contaminants. The method of deactivating and cleaning a solid organic substrate contaminated with solid radioactive dispersed inorganic contaminants, in which the substrate is brought into contact with a water-free extraction medium, containing: densely compressed CO2; non-halogenated surfactant selected from block-copolymers of polyethylene oxide PEO and polypropylene oxide PPO, such as double-block copolymers (EO)x-(PO)y, tri-block copolymers (EO)x-(PO)y-(EO)x and tri-block copolymers (PO)x-(EO)y-(PO)x, where x and y are integers from 2 to 80, where x is not equal to y, and polydi(from 1 to 6 C)alkylsiloxane, such as polydimethylsiloxane (PDMS); a complexing agent selected from tributylphosphate (TBP), crown ethers, tributylphosphine oxide, triphenylphosphine oxide; and tri(n-octyl)phosphine oxide; and a substrate and/or extraction medium are subjected to mechanical action simultaneously with the contact operation. |
 Device for cleaning long hollow parts / 2417848Invention relates to ultrasound processes relates with intensification of treatment processes, in particular, of cleaning long capillary tubes. Proposed device comprises vessel with process solution and support to locate said vessel in the bundle of processed tubes. Vessel casing inner surface accommodates sources to generate vibrations in treatment fluid layers. Proposed device incorporates also outer source to feed generated pulses to said fluid layers. Note here that support base is inclined to horizon at 10-60°. |
 Method of hydro cavitation treatment of parts and device to this end / 2414308Invention relates to cleaning parts in liquid, and pertains to method of hydro cavitation cleaning of parts and device to this end. Parts to be cleaned are placed in bath with detergent at the depth of, at least, 1 m, and are revolved. At least, two high-pressure cavitation pulsating jet flows are generated to be directed to the part at different angles. The part is revolved at 1-10 rev/s. Parts are cleaned by cavitation pulsating jet flows in flow pulsation frequency range of 10 to 10000 Hz. Proposed device comprises bath with washing fluid, accumulating reservoir, washing fluid feed gate valve, pump, pipeline, washing fluid heating temperature control device, cavitation exciter, cavitator adjustment mechanism, control unit and motor with its axle supporting cleaned part. Control unit outputs are connected with cavitator adjustment mechanism control inputs and with pump control input. Besides, proposed device comprises temperature pickup, contaminated fluid settler, fluid coarse and fine filters. |
FIELD: metallurgy.
SUBSTANCE: arc discharge cathode spots are initiated at processed surface, arc discharge being initiated between anode and cathode in the mode of voltage-current characteristic of increasing section, said cathode being a processed surface. Region of cathode spot location on processed surface is localised and processed surface is shifted by anode displacement. Anode with current-collecting surface area smaller than that of cathode is used and placed at the distance from cathode that ensures a positive anode voltage drop.
EFFECT: stabilised cathode spots on processed surface, fast surface cleaning and higher surface quality.
2 dwg
The claimed invention relates to the technique of surface treatment products arc discharge in vacuum to remove surface dirt.
Currently, cleaning products are widely applied to various mechanical, chemical and electrochemical methods. Depending on the nature, type and degree of contamination primarily used aqueous detergents and solvents, an organic liquids of different polarity (benzene, kerosene, acetone, ethylene dichloride, and others). Used for this purpose production line treatment, require large areas. Released during the etching of evaporation is not only harmful for staff, but also destructive influence on production equipment at shop design. In addition, the use of acids and alkalis requires their disposal, subject to measures preventing the environment pollution.
To clean the surface of the material from residues of lubricants, descaling, oxide films and other types of contaminants are widely used arc discharge in a vacuum. In comparison with other methods, this method is attractive because of its absolute environmental safety and because of the number of benefits arising from the effect of the discharge on the surface.
The electric arc is established form of electric current passing through the discharge gap and bordering electrodes, low cathode voltage drop (about potential excitation or ionization of atoms plasma environment) and large bit currents.
Arc categories differ in the character of physical processes at the cathode, the state plasma positive column, and also by the nature and pressure of plasma-forming medium through which the current flows.
For all types of arc discharge regardless of the pressure plasma environment width of the region of the cathode voltage drop d to significantly shorter than the mean free path of electrons λe , because what is the latest cross it in the collisionless regime.
In [Lisenkov A.A. Cathode spot of vacuum arc discharge // Vacuum equipment and technology, 2004. T. №4. S-226] it is shown that in case of vacuum-arc discharge, at the initial moment of time on crude cathode surface occurs uncontrollable, chaotic and moving very quickly covering the entire surface of the discharge.
The presence of surface impurities and defects even at low concentrations has a significant influence on thermal emission properties of metals and leads to a noticeable variation output (more than 0.1 eV). These conditions significantly facilitate the maintenance of an emerging category that can exist at a lower value of the discharge current than the discharge cathode material.
Discharge current determines the number of spots simultaneously existing on the working surface of the cathode. So thin-film coatings pollution, current, mud at each cathode spot, can be supported by a current of a few amps, what with the increase of the discharge current is increasing simultaneously existing stains.
Under the high density of energy released in the cathode spots, is local heating of the surface, explosive evaporation layer of dirt and formation generated from treated surfaces plasma flows.
The number of known ways of processing of a surface of products arc discharge in a vacuum:
- the impact of the arc discharge on the surface in vacuum at a pressure of 10 -5 ...10 -3 mm Hg [speaker of the Russian Federation №476041. B08B 1/00. Esteros - and other The way to remove the oxide film and dirt from the details lei; application №1695276, 30.08.1971. Publ. 05.07.1975, bul. №25];
- the impact of the arc discharge to the surface being treated in a protective gas environment [speaker of the Russian Federation №171056. H05B. Finland L.A., leschev E.N. The method of purification of arc wire arc welding; application №818848/25-27, 19.11.1963. Publ. 11.05.1965].
When burning arc discharge observable physical processes are determined by the behavior of cathode spots, which are fundamentally unstable plasma formations and are characterized by some average life time. The main task for the removal of surface dirt is the creation of devices managed by the nature of the movement of cathode spots on the working surface.
In [RF Patent 2180472. H05H 1/50, C23C 14/35. Lisenkov A.A. and other Vacuum-arc plasma source; application №20001103758/06, 07.02.2000. Publ. 10.03.2002] it is shown that at operation of control devices on the cathode surface arise velocity of cathode spots, which, despite the presence of an external magnetic field, carry out the chaotic movement across the surface of the cathode with the purpose of cleaning, including its outside part where and created the ideal conditions for maintaining discharge between the cathode and the anode.
In [ASF №1695704. C23C 14/02. Esteros - and other Method of surface treatment products arc discharge in a vacuum; application №4339958, 21.12.1987. Publ. 23.12.1992] for removal from a surface of details oxide films and pollution, hardening or leave the near-surface layer machined parts, remove Burr, moving cathode spots on the surface, is performed by moving the screen with a hole, located between the cathode and the anode.
The use of the screen with aperture, requires a significant increase in power is invested in the discharge. The intensity of the plasma flows from the diaphragm exceeds the intensity of the cathode and anode jets, which shifts the region of their interaction to the electrodes and contributes to the formation of diffuse binding arc to the electrodes. The screen in the process of work intensively heated, which requires cooling, which is hard to arrange in a vacuum. Move the screen above the surface very difficult to operate and requires creation of complex systems of electrical insulation.
The method of cathodic treatment of details sustainable arc discharge [A.S. the Russian Federation №719710. B08B 3/10, H05B 7/00. Esteros - and other application 2569061, 01.12.1977. Publ. 05.03.1980] - discharge is burning between the anode and the cathode (the workpiece) mode of declining area of volt-ampere characteristics. To improve the speed and quality of treatment in the process of surface treatment changes the potential along the treated surface. Thereby provides directional movement cathode spot. The disadvantage of this method is the low quality of surface cleaning products and low productivity due to the possibility of existence of two types of sustainable arc discharge in vacuum, depending on the nature of physical processes in the field of cathode and anode spots.
The closest to the claimed method on a set of attributes is the method of surface treatment products arc discharge in vacuum, is presented in [RF Patent №2144096. C23C 14/02, C23F 4/04. Of Antibes B.F. and. other The method of surface treatment products arc discharge in a vacuum; application №981100036/02, 18.05.1998. Publ. 10.01.2000].
Localization of cathode spots of the arc discharge on the treated surface in vacuum is achieved by imposing a constant magnetic field. Arc discharge excite mode growing area of volt-ampere characteristics, which distinguish between the cathode and anode region and nestled in between the positive pole.
To control the movement of cathode spots on the electric arc is applied external magnetic field, while, due to changes in the magnitude and direction of the magnetic induction vector.
Moving cathode spots on a processed surface requires the creation of complex mechanical systems and control systems for moving magnetic systems. Besides these conditions significantly limit the field of practical application of the method for machining of complex components.
Task the claimed invention is a method of surface treatment products arc discharge in vacuum with reliable fixation and managed nature move cathode spots on the surface that would be easy to use and versatile in application for surface treatment any geometric forms.
The solution of this problem will allow to achieve the following technical results:
- to simplify the stabilization of cathode spots on the treated surface;
- reducing the time of technological process of purification;
- to improve the quality of the surface.
Specified the technical result is achieved due to the fact that the method of surface treatment products arc discharge in vacuum, including initiation on the treated surface of the cathode spots of the arc discharge, which excite mode growing area of volt-ampere characteristics between the anode and cathode, which is treated surface, for the implementation of the localization region of existence of cathode spots on the treated surface and its offset by moving the anode, while using the anode area tokopriemnye surface, the smaller area of the cathode, and install it on the distance from the cathode providing positive anode voltage drop.
The implementation of the stabilization of the discharge on the surface of treated using the selected combustion conditions of discharge is quite simple and does not require more complex design solutions, and to process the products of any shape, including sample plots available hard surfaces.
Summary of the invention is illustrated by drawings.
Fig 1. - Vacuum-arc device for surface treatment products cathode spots of the arc discharge in vacuum and distribution voltage between the electrodes.
2. - Photo of the processed surface.
The device that implements the method of surface treatment products cathode spots of the arc discharge in vacuum, presented in (Fig 1, a).
The expansion of the plasma flow in the area of the anode 2 is in the direction, first of all perpendicular to the surface of the cathode 1, which formed the cathode spot 3, the longer the distance from the cathode 1 to the anode 2, the greater the receiving surface shall to have the anode 2.
To initiate the cathode spots of the arc discharge pulse is used scheme of control electrode 4, which with the specified frequency and amplitude pulses U under . Depending on the implemented design might as moving anode 2 regarding processed surface 1, and move the cathode 1 regarding the anode 2.
The minimum distance between the electrodes (L CA ) is determined by the region of localization of the arc discharge and conditions effective electronic circuit current from the cathode to 1 on the anode 2 (in the process of work, provided move the electrodes relative to each other, the distance L CA remains unchanged). The distribution of the electric field in such a system is determined by the voltage at the electrodes, the specific conductivity of plasma and spatial distribution of the space charge in the near-electrode regions. The presence of non-compensated charge shall determine the existence of near-cathode (U ) and anode (U a ) potential drop (Figure 1, b).
The General decline in arc voltage (L arcs ) is the sum of the voltage on the arc column (U V. ), cathode (U ) and an anode (U and - a potential difference between the edge the area undisturbed anode phenomena positive post and anode): U Doug =U +U a +U V.
Under the condition of homogeneity of the arc column, U article is defined as the product of the electric field strength E on the length of the channel arc l U St =El. In the vacuum-arc plasma sources used for formation of coatings, the distance between the cathode and the anode (CA L ) reaches 0.5 m For effective as cleaning the surface of the cathode spots and stable combustion discharge, the distance between the electrodes does not exceed a few centimetres.
Between the unperturbed plasma and anode 2, is formed near-electrode layer of the space charge (Figure 1, b) - anode voltage drop (U a )regulating the flow of charged particles on the anode:
U a = - k T e e ln j e j a ,where k - Boltzmann constant; T e - e-temperature; 1/2 j e =0,25en(8kT e /πm e ) 1/2 - density chaotic current of electrons from the plasma; j a =I bit /S a is the density of the discharge current on the anode; S a reception surface of the anode; I time - discharge current.
As you can see, the sign of the anode voltage drop (U a ) depends on the ratio of currents j e /j a, and can be both positive and negative.
If the total current, resulting integrating current density of chaotically moving plasma electrons across the surface of the anode, was equal to the required current (j e =j (a ), then this is the ideal case U a =0.
Negative drop is implemented, provided j e S a >I once (j e >j a ) and is provided at the discharge current I (for all the considered cases believe that I =const), and the developed surface of the electrode (S <<S a ), which adjoins dense, strongly ionized plasma. These conditions are implemented in a vacuum-arc plasma sources used for coating. In this case, the negative anode drop is small at (-1 -3...) Century
With the reduction of the area of the anode (S & GE; S a ), if / once and the corresponding change of density currents j and e j a , this shell first disappears (while I, a =j e S a a U a =0), and then is replaced by electronic.
The change of sign anode potential drop occurs when J e S a <I times : reception of the surface of the anode S a reduced ('s to >>S a ), and the current density j a is equal to or greater j e . Involved in the way the area of the electrode is selected from the following conditions:
S a < 4 I R and C e n e 8 k T e / PI m e exp ( - e U a k T e )Thus, the anode potential drop (U a ), its sign and magnitude are to control that supports the concentration of charged particles before the anode at the level providing summing to it the discharge current.
The sign and magnitude of anode voltage drop (U a ) depend on the shape and size of the receiving surface of the anode 2, the distance between the electrodes (L CA ), on the degree of vacuum in a vacuum chamber, the presence of gas, the discharge current (I ) and some other factors.
In the discharge anode small square near the anode there is a strong electric field, dilatory from him ions. When the rate of formation of ions is the same as in the post, negative space charge cannot be compensated for and installed the positive anode drop of this magnitude, which accelerated during the electrons produce additional ionization, supplying the required amount of ions.
In addition to electrons hitting the anode 2 with energy corresponding to the anode potential drop (U a ), condensed and release energy neutral atoms of metal, and also reported to the radiation energy cathode and plasma flow. All incoming energy must be balanced by the heat sink deep into the anode 2, reverse radiation in the category and evaporation anode or other materials, condensing metals.
For calculation of the power, generated at the anode (P (a ), the expression
where I once discharge current, reaching the anode; eφ - the work of an electron exit of the anode material; 2kT e /e is the average kinetic energy of the electrons produced in the anode region of plasma; U a - anode voltage drop.
The cleaning mode on the contaminated areas of the working surface of the cathode exists independent, chaotic and fast-moving category. At the moment of time t=0 (Fig 1, a) for initiating the electrode 4 is served pulse voltage U under , contributing to the formation on the cathode surface 7 source primary electron - cathode spots 3, which is the basis of post arc discharge. Number of simultaneously existing cathode spots is determined by the discharge current I , the degree and type of soiling of the surface.
After excitation - cathode spot 3, moving in an external electric
E →and self-magnetic
B →the fields are retained on the part of the surface cathode 7, where there is a minimum voltage of burning discharge, i.e. in the field with a minimum distance of anode-cathode L CA , and provide the most favorable conditions for the closure of the discharge current on the surface of the anode 2.
Thus, the movement of cathode spots on 3 processed surface (S ) is determined by the place of arranging the anode 2 regarding cathode 7 and localization of cathode spots limited to geometric size of the receiving surface of the anode S a .
Moving cathode spots 3 on the treated surface is chaotic and therefore the reduction of the receiving surface of the anode 2 limits the surface of the containment area is equivalent ~ S a . Narrowing the field of existence increases as the speed of rise of temperature on the treated area of the cathode 1, and the rate of removal of dirt from the surface.
The time spent anode relative to the treated surface is determined by the density of the heat flux q emitted by cathode spots, and a level surface contamination at the site. In the result of the cathode spot 3 (temperature exceed boiling temperature, the material on where they exist) provide as evaporation of the surface layer (layer of dirt), and heat the surface up to the temperatures at which in the areas adjacent to its location, there is the chemical decomposition of dielectric films and flaking scale.
When considering heat problems, the unknown quantities are temperature distribution in the cathode 1, depth change warmed layer and the law of the time variation of the phase transitions. When considering the effects of moving cathode spot 3 on the surface in the presence of the processes of melting, crystallization and sublimation solution of the heat problem is reduced to the problem with moving boundary (Stefan problem).
At the moment of time t 1 warranty 0 (Figure 1, b), provided move anode 2 with speed V a relatively cathode 7, observed motion of the cathode spots 3 on a processed surface in the direction appropriate to the offset of the anode. The velocity of an anode (V a ) with respect to the cathode 1 determined from the conditions of existence of the discharge on the cathode: discharge current (I ), thermophysical properties of the surface layer of the processed surfaces and conditions of heat removal.
Anode shape 2 in the implementation of treatment is determined by the size and geometry of the processed surface 1 and at any point of the path, the distance between the surface 1 and anode 2 remains constant.
The voltage drop across the discharge gap in the process of surface treatment in the presence of contamination and the existence of discharge purified cathode material is different. So the end of the treatment process is determined by the output on a stationary state of the voltage drop across the discharge gap.
The technology was tested on the unit for removal of the outer surface of the steel cylinder (diameter 20 cm, length 50 cm) from contamination. Procurement is permanently attached to the structure, providing her forward motion of the anode, made in the form of water-cooled copper ring (inner diameter 22...25 cm, length 1,5...2,5 cm) and covering the surface.
Procurement connected to the negative (grounded) terminal of the power source. The anode is connected to the positive terminal of the power source. Treatment in a vacuum chamber is carried out at a pressure of 1...10 PA. The voltage drop across the discharge gap for untreated surface was 17...20 In, and treated for more than 20 Century
The created system allows you to modify the reception area of the surface of the anode 2 and the speed of travel of electrodes relative to each other, as well as current arc discharge, which allowed to study the relationship between the temperature of the arc and the temperature of the treated surface.
Technology of cleaning of metal surfaces used for cleaning of large-size products, as well as in the restoration of various containers and pipelines gaseous and liquid media. The special importance of this technology gets when working with hazardous substances, as in the plasma flow is to decompose into less dangerous components.
Thus, the proposed technology of processing of the surfaces with the arc discharge in vacuum improves quality, productivity and efficiency of the process, and most importantly, it meets the ecological requirements of modern manufacture.
The method of surface treatment products arc vacuum discharge, including initiation on the treated surface of the cathode spots of the arc discharge, which arouse in the mode of increasing land-voltage characteristics between the anode and cathode, which is processed surface, wherein exercise localization region of existence of cathode spots on the treated surface and its offset by moving the anode, while using the anode area tokopriemnye surface, the smaller area of the cathode, and set him at a distance from the cathode providing positive anode fall voltage.