UA77299C2 - Vacuum electroarc device with curved plasma channels - Google Patents

Abstract

Vacuum electric-arc device with curved plasma channels is assigned for application of composite coverings at the articles. In the device two contrary sources of plasma are connected with plasma-guide, which is wrapped with at least one electromagnetic-deflection coil. The convolutions of the electromagnetic-deflection coils are bended in such a way that a half of each convolution wraps the plasma-guide between one of the contrary sources of plasma and its outlet, and other half of the convolution wraps the plasma-guide between the second source of plasma and its outlet. The proposed convolution form allows synchronous creating two symmetric curved plasma channels, which do not prevent the plasma transporting from the third source of plasma placed in front of the outlet. Thus, three streams of plasma from three sources can be used synchronous for treating the surfaces.

Description

Description of the invention

The invention relates to vacuum plasma technology and is primarily intended for applying 2 composite coatings to products. It can be used in machine building, tool, electronic and other industries to modify the surfaces of materials irradiated by electrons, ions of metals and gases, as well as to deposit coatings on the elements of devices and machines.

Plasma vacuum installations, which use an electric arc discharge to vaporize materials, are widely used in the technological processes of applying coatings for various purposes. 710 The main advantage of these processes is due to the possibility of synthesis of many surface layers from various materials, including those that have unique properties and cannot be obtained by other methods.

New developments of vacuum-plasma installations are aimed at forming streams of filtered plasma without macroparticles and metal drops. An urgent task is to obtain composite coatings, for example, such as

TIAIM, TiSimM, TiAIatM, TiAaiMoOM and others with a certain component ratio. Composite materials 72 are those that are formed by the simultaneous deposition of various elements.

A vacuum electric arc device with a curved plasma channel |) is known, which contains a plasma source with a focusing electromagnetic coil connected to a plasma conductor. This plasma conductor is made in the form of a quarter of a torus and is surrounded by deflecting ring electromagnetic coils, which form a curved magnetic field inside it. The output hole of the plasma conductor is covered by the output electromagnetic coil. It 20 is outside the zone of direct vision from the cathode surface of the plasma source.

The plasma flow, which is generated during the evaporation of the cathode in the electric arc discharge, enters the toroidal magnetic field of the plasma conductor. Moving in this field, the plasma flow makes a 902 turn and through the outlet is directed to the products that are located in the vacuum chamber connected to the plasma conductor.

The charged components of the plasma, electrons and ions in such a device are transported to the exit opening c 25 of the plasma conductor, and heavy and weakly charged macroparticles almost do not react to magnetic and electric fields and do not pass through the curved channel without colliding with its walls. But not all macroparticles completely lose their kinetic energy even with several consecutive collisions with the walls of the plasma conduit. Many of them end up at the system output. The number of ricocheted particles is significantly reduced at the exit, if "intercepting" screens in the form of transverse ribs are located on the inner surfaces of the plasma conductor. The system of 30 such edges is a kind of trap for macroparticles |21. Gee)

The efficiency of cleaning plasma from macroparticles in such a curved filter is higher, the longer the plasma channel, the narrower it is and the greater the angle of its total bend. But at the same time, the losses of the ionic component of the plasma necessarily increase, and its flow at the output of the system decreases. The productivity of the system decreases, and the complexity of its production and cost increases. Currently, it is possible to use such systems in production

In practice, it is very limited. To obtain composite coatings, for example, such as TiIAIM in such a device, it is necessary to use a cathode made of an alloy of the appropriate metals for the electric arc source. Such cathodes are expensive and scarce. In addition, when using them, it is not possible to regulate the relative contribution of individual components in composite coatings in the process of their creation. "

It is known about another vacuum electric arc device with directed plasma channels for applying Z coatings, which is taken as a prototype (Z). It houses two opposing plasma sources with focusing electromagnetic coils that are connected to the plasma guide, and may be spanned by one or more deflecting electromagnetic coils. It also has an output electromagnetic coil that spans its exit opening. The plasma guide is parallelepiped-shaped at on the edges of which plasma sources are installed. In one version of this device, curved plasma channels are created only with the help of focusing coils of plasma sources and a coil covering the exit hole. This option allows, when using cathodes from different pure metals in different plasma sources, to obtain composite coatings without use of alloy -I cathodes. But the plasma flow transport coefficient in the magnetic field of such a device is very low, because the curved magnetic field has significant corrugation and areas with large gradients in the transverse and longitudinal directions. A very small part of the generated plasma reaches the output of the device, which causes ( se) 20 its unprofitability.

In another variant, in this device (ZI) deflecting electromagnetic coils can be installed in the form of frames in the form of rectangles, which cover the plasma conduit along the diagonals of the side faces between the plasma sources and the exit hole. The magnetic field created by such a deflecting coil forms a curved plasma channel , in which the transport of plasma to the outlet is greatly improved. But the 59 plasma sources in such a device cannot work simultaneously, but only alternately, according to the alternate

GF) by including diagonal deflection coils. This does not allow to obtain composite coatings when using monometallic cathodes.

The invention is based on the task of improving a vacuum electric arc device with curved plasma channels by changing the design of deflecting electromagnetic coils in order to more effectively transport plasma to the outlet of the device simultaneously from different plasma sources.

The coefficient of transport of plasma flows should not be worse than that in the case of using a deflection coil in the form of a frame in the shape of a rectangle.

The problem is solved in a patented vacuum electric arc device with curved plasma channels, which, like the device taken as a prototype, includes two counter plasma sources 65 with focusing electromagnetic coils, which are connected to a plasma conductor covered by one or more deflecting electromagnetic coils and which has an output solenoid coil that spans its output port.

The patented device differs from the prototype in that the turns of the deflecting coils are bent so that one half of each turn covers the plasma conductor between one of the oncoming plasma sources and the outlet of the plasma conductor, and the second half of the turn covers the plasma conductor between the second of the oncoming plasma sources and the outlet of the plasma conductor.

In one of the options, the turns of the deflecting coils have the shape of an equilateral triangle without a base in profile, and the top of the triangle faces the side opposite to the outlet opening of the plasma conductor. 70 In another version, the turns of the deflecting coils have in profile the shape of an equilateral trapezoid without a larger base, and the smaller base of the trapezoid faces the side opposite to the outlet of the plasma conductor.

There may also be such a variant, when the device is equipped with two groups of deflecting coils, one of which has the mentioned triangular turns, and the second has the mentioned trapezoidal turns, and the coils with triangular turns are located closer to the outlet of the device than the coils with trapezoidal turns. 15 In each of the options, the device can be equipped with a third plasma source with a focusing coil, which is connected to the plasma conductor on the opposite side of its outlet coaxially with it.

Let's consider how the features of the patented device make it possible to simultaneously create two curved channels for transporting plasma, which connect into one near the outlet.

Due to the fact that the coils of the deflecting electromagnetic coil in the patented device are bent so that one half of the coil covers the plasma conductor between one of the opposing plasma sources and the outlet, and the other half between the second of the opposing sources and the outlet, when such a coil is turned on, the electric current, which flows along the first half of the coil creates a magnetic flux, which, together with the magnetic fluxes of the first focusing and output coils, creates a curved channel for transporting plasma from the first source.

The same current, flowing along the second half of the coil, creates a magnetic flux, which, together with the magnetic fluxes of the second focusing and output coils, creates a channel for transporting plasma from the second source. Both channels are symmetrical and connect near the outlet on its axis. Since both channels are created by i) current flowing through the same deflection coil, they can operate simultaneously, directing plasma flows from both opposing plasma sources to the outlet. At the same time, it is possible to place a third plasma source with a focusing coil on the axis of the output hole opposite it, the plasma flow of which will not be bent by the Deflecting coil, i.e. it will flow straight along the axis to the output of the device.

The turns of the deflecting coil can be either triangular or trapezoidal in profile. Both Me halves of the turn must be symmetrical about the axis of the output hole, if the opposite sources are also symmetrical about this axis. If coils with both forms of turns are used, the coils of triangular shape in the profile should be closer to the output hole, for effective bending of the magnetic field near the axis of the output hole. uh-

Increasing the number of deflecting coils helps to create curved magnetic fields with smaller gradients at bend locations and improves plasma transport.

Thus, the proposed shape of the turns of the deflecting coils makes it possible to simultaneously create two symmetrical curved plasma channels that do not interfere with the transportation of plasma from the third source, " 40 located opposite the outlet, and to use plasma streams for processing the surfaces of products from three plasma sources at the same time.

The essence of the invention is explained by graphic materials. Fig. 1 shows an axial section of the patented;" electric arc device with two opposite plasma sources and with a third plasma source coaxial with the output hole. The dotted lines show the profiles of the deflecting coils. Fig. 2 shows a view 45 of a deflection coil, in which the turns in the profile have the shape of an equilateral triangle without a base. Fig. 3 shows the -I view of the deflecting coil, in which the turns in the profile have the shape of an equilateral trapezoid without a larger base.

We will consider the possibility of implementing the invention on a device that contains (see Fig. 1) a plasma conductor 1 with two

Ш - opposite plasma sources with evaporators 2 and З and with focusing electromagnetic coils 4 and 5. ко Evaporators 2 and З are located opposite each other at equal distances from the output hole 6, 5o covered by the output electromagnetic coil 7. The third plasma source is covered by the focusing ik electromagnetic coil 8 and has an evaporator 9, the axis of which coincides with the axis of the hole 6. The plasma conductor 1 is covered

Ge) deflecting electromagnetic coils, the profiles of which are shown in dotted lines. The turns of the deflection coils, bent so that one half of each turn covers the plasma conductor 1 between the first counter plasma source with the evaporator 2 and hole 6, and the second half of the turn covers the plasma conductor 1 between the second counter plasma source with the evaporator C and the hole 6. The profile of the turns of the nearest to the opening 6 of the deflecting coil, the external view of which is shown in Fig. 2, has the shape of an equilateral triangle without a base. Its top faces the side (Ф) opposite to hole 6. The other two deflecting coils, the general view of which is shown in Fig. 3, are located farther from hole 6 and their turns have the profile shape of an equilateral trapezoid without a larger base. All deflecting coils (see Fig. 1) are installed symmetrically relative to the plane containing the axis of the output coil 7. This plane is the plane of mirror symmetry for evaporators 2 and 3. This design ensures the formation of two curved magnetic fluxes that pass through the evaporators 2 and C and create the corresponding plasma channels, and one rectilinear magnetic flux, which passes through the evaporator 9 and creates, respectively, a rectilinear plasma channel. All three channels converge in the hole 6, covered by the output coil 7. The hole 6 of the plasma conductor 1 is connected to the vacuum chamber 11. in which the products (not shown in Fig. 1) are located, on the 65 surface of which plasma flows from all three plasma sources are directed. The directions of movement of the oncoming plasma sources are shown by curved trajectories 12, and the direction of movement from the source with the evaporator 9 is shown by the straight trajectory 13, which coincides with the axis of the exit hole 6.

Consider the operation of the device.

First, the internal volumes of the plasma pipe 1 and the chamber 11 (see Fig. 1) are pumped to a vacuum of up to 10 Pa. Next, the current is turned on in electromagnetic coils 4, 5, 8, and 10. After that, electric arc discharges are excited on evaporators 2 and Z from opposite plasma sources and on evaporator 9 a source coaxial with hole 6. The plasma generated in electric arc discharges spreads along the power lines three magnetic flows, which merge into one flow in the opening 6 at the entrance to the chamber 11, where the products whose surfaces are processed (not shown in Fig. 1) are installed. The plasma flows generated by counter sources with vaporizers 2 and 3, 70 pass along the curved plasma channels along the trajectories 12. At the same time, macroparticles and metal drops that arise during electric arc discharges go along straight paths and cannot enter the opening 6 without multiple collisions with the walls plasma type 17 in which they lose their energy. Therefore, their number, which can then pass into chamber 11, is insignificant. Macroparticles and droplets flying from the evaporator 9 can fall into the hole 6, because a significant number of them go along the trajectory 13. To prevent this, special screens (not shown in Fig. 1) are used and a refractory metal cathode is used in the evaporator 9.

By changing the currents of the vacuum arcs of evaporators 2, C and 9, as well as the strengths of the magnetic fields created by coils 4, 5 and 8, it is possible to change the intensities of the plasma flows from each of the evaporators and obtain composite coatings with different contents of its components. At the T00A arc current of each of the vaporizers 2 and Z 2 of the opposite plasma sources, the coating growth rate is 6-12 μm/h. depending on the material of the cathode.

From the third source, the growth rate of the coating can be 10-1bm/h.

Examples: 1. The synthesis of optically transparent compounds such as AIi 2Oz, AIM, TiOo and others is carried out using separated plasma streams, which are generated from opposite sources with vaporizers 2 and 3. The pressure of the reactive Ga gas Oo or Mo is 0.533-0.566Pa . The deposition rate of AI2O3 is 25 μm/h, AIM - 20 μm/h, TiO" - 20 μm/h. o 2. The synthesis of diamond-like coatings can also be carried out from separated streams, which are generated by counter sources with evaporators 2 and 3 with graphite cathodes.

C. The synthesis of TIAIM, TiSyM can be performed in two ways: a) only from separated flows created by) the first from opposite sources with a titanium cathode and the second from opposite sources with an aluminum (copper) cathode; b) from the separated streams of aluminum (copper) plasma, which is created by counter sources, and about titanium plasma from a source with an evaporator 9 with a titanium cathode. c 4. Application of composites TiAIitM, TiIAIIMOoM, TiStAIM can be carried out with the simultaneous deposition of separated streams of titanium and aluminum plasma from opposite sources and flow of zirconium, chromium or - molybdenum plasma from a third source. The deposition rate is 30-35 µm/h. -

Sources of information: 1. Aksenov I.I. etc. Transportation of plasma flows in a curvilinear plasma-optical system.

Physics of plasma, 1978, vol. 4, issue b, p. 756-763. « 2. Application PCT UMO 96/26531 dated 08/29/96 С23С14/32.

Z. US Patent Mo5 435 900 dated 07/25/95 С23С14/22 (prototype). - with "z

Claims (5)

The formula of the invention 1. A vacuum electric arc device with curved plasma channels, which includes two opposing -I plasma sources with focusing electromagnetic coils, which are connected to a plasma conductor covered by at least one deflecting electromagnetic coil, which has an output electromagnetic coil, which Ш- covers its output opening , which differs in that the turns of the deflecting coils are bent so that one half of each turn covers the plasma conductor between one of the opposing plasma sources and the outlet opening 5or of the plasma pipe, and the other half of the turn covers the plasma conductor between the second of the opposing plasma sources and the outlet opening of the plasma pipe . Gee) 2. The vacuum electric arc device according to claim 1, which is characterized by the fact that the mentioned turns of the deflecting coils have in profile the shape of an equilateral triangle without a base, and the top of the triangle is turned to the side opposite to the outlet opening of the plasma conductor. 3. The vacuum electric arc device according to claim 1, which differs in that the mentioned turns of the deflecting coils have in profile the shape of an equilateral trapezoid without a larger base, and the smaller base of the trapezoid is turned to the side, Ф) opposite the outlet of the plasma duct. ka 4. The vacuum electric arc device according to claim 1, which is characterized by the fact that it is equipped with two groups of deflecting coils, one of which has the mentioned triangular coils, and the second - the mentioned trapezoidal coils, because the coils with triangular coils are located closer to the outlet of the device , than coils with trapezoidal turns. 5. A vacuum electric arc device according to any one of claims 1-4, which is characterized in that it is equipped with a third plasma source with a focusing coil, which is connected to the plasma guide on the side opposite to its exit opening coaxially with it. b5