RU2544729C1 - Device for thermochemical treatment of parts in non-self-maintained glow discharge - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: device for thermochemical treatment of parts in non-self-maintained glow discharge comprises vacuum chamber and substrate for placement of parts, power supply source connected by negative pole to the substrate and by positive pole to the chamber body, thermionic-emission electrode, the second power supply source connected by negative pole to thermionic-emission electrode and by its positive pole to the chamber body, hollow cylindrical electrode having inner diameter exceeding geometrical dimensions of the treated part, and thermionic-emission electrode placed coaxially to the cylindrical electrode. Device comprises additional hollow cylindrical electrode placed coaxially to the first one and forming electrostatic lens with the first electrode. Symmetry axis of hollow cylindrical electrodes is oriented under angle equal to maximum angle of ion flow incidence to the treated part surface. Thermionic-emission electrode is placed at focus of electrostatic lens.

EFFECT: improved fatigue range for parts and reduced energy costs for thermochemical treatment.

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Description

The device relates to electrothermal engineering, in particular to vacuum installations for coating in the discharge. This invention can find wide application in mechanical engineering, automotive, chemical industry.

A device for cathodic-plasma nitriding of products (Cathodic-plasma nitriding of products based on the upgraded Bulat unit, information leaflet No. 300-88, Krasnodar, Central Scientific and Technical Research Institute, 1988), containing a vacuum chamber and a substrate for accommodating parts, a power source connected by a negative a pole with a substrate, a positive one with a camera body, a thermionic electrode, a second power source connected by a negative pole with a thermionic electrode, a positive one with a camera body.

The disadvantage of this device is the relatively long duration of the process of chemical-thermal treatment of parts and the high temperature of the process.

Closest to the proposed device is a chemical-thermal treatment of parts in a non-self-contained glow discharge (Device for chemical-thermal treatment of parts in a non-self-contained glow discharge. Patent No. 2355817 of July 4, 2007) containing a vacuum chamber and a substrate for accommodating parts, source power supply connected to the negative pole with the substrate, positive to the camera body, thermionic electrode, a second power source connected to the negative pole to the thermionic electrode, positive one with a camera body, an additional hollow cylindrical electrode coaxially located between the thermionic electrode and the workpiece, and an additional adjustable constant voltage source, the negative pole of which is connected to the substrate, and the positive one with an additional electrode having an internal diameter exceeding the geometric dimensions of the workpiece and providing the angle of incidence of the ion flux on the surface of the workpiece from zero to critical.

The disadvantage of this device is the relatively long duration of the process of chemical-thermal treatment of parts and the high temperature of the process.

The objective of the present invention is to reduce the duration of the process of chemical-heat treatment of parts and lowering the temperature of the process.

In a device containing a vacuum chamber and a substrate for placing parts, a power source connected by a negative pole to the substrate, a positive one with a camera body, a thermionic electrode, a second power source connected by a negative pole with a thermionic electrode, a positive one with a camera body, a hollow cylindrical electrode having an inner diameter exceeding the geometrical dimensions of the workpiece and a thermionic electrode located coaxially with the cylindrical electrode, solutions This problem is achieved by introducing a second hollow cylindrical electrode, similar to the first and located coaxially to it with the formation of an electrostatic lens with the first, while the axis of symmetry of the hollow cylindrical electrodes is oriented at an angle equal to the critical angle of incidence of the ion flux on the surface of the workpiece, and thermionic the electrode is located at the focus of the electrostatic lens.

This device has a significant difference, since it involves the use of a second hollow cylindrical electrode, similar to the first and located coaxially with it to form an electrostatic lens with the first, while the axis of symmetry of the hollow cylindrical electrodes is oriented at an angle equal to the critical angle (for a given material) of the ion flow to the surface of the workpiece, and the thermionic electrode is located in the focus of the electrostatic lens, which allows you to form a parallel ion flux, i.e. provides the fall of all ions on the treated surface at an angle equal to the critical, reducing the duration of the process of chemical-thermal treatment of parts and lowering the temperature of the process.

As is known, nitriding (a special case of chemical-thermal treatment) in a discharge involves two competing processes: cathodic surface sputtering, accompanied by the formation of nitride of the atomized material in the atmosphere of nitrogen and condensation, adsorption (reverse cathodic sputtering on the surface of the formed nitrides, as well as nitrogen ions, accompanied by diffusion of nitrogen into the matrix).

The efficiency of cathodic sputtering in a discharge substantially depends on the angle (α) of the ion flow incidence. At incidence angles other than critical, the sputtering coefficient decreases, while at an incidence angle equal to critical, the sputtering coefficient is 1.25-2.5 times higher than with normal incidence of ions (I.A. Abroyan , A. Andronov, A. Titov, Physical Foundations of Electronic and Ion Technology: Textbook for Special Electronic Technology of Universities, Moscow: Vyssh. Shk., 1984. - p. 214-215). Such an increase in the cathode sputtering coefficient is achieved only if all the rays of the ion flux fall on the surface to be treated at an angle equal to the critical, i.e. in the case of their parallelism, in contrast to the prototype, where the angle of incidence of the ion flux on the surface of the workpiece (in a converging stream) from zero to critical. The cathode sputtering coefficient substantially depends on the cathode temperature, and therefore, ceteris paribus, optimization of the angle of incidence of the ion flux allows one to lower the temperature of chemical-thermal treatment. And, as you know, the higher the temperature of nitriding, the lower the endurance limit of the parts. This is due to softening of the core and a decrease in residual compressive stresses.

The drawing shows a diagram of a device for chemical-thermal treatment of parts in a non-self-contained glow discharge, where: 1 - a vacuum chamber, 2 - thermionic electrode, 3 - hollow cylindrical electrodes, 4 - workpiece, 5 - substrate for placing parts, 6 - power source , 7 - a second power source, 8 - an alternating current source, 9, 10 - power sources of hollow cylindrical electrodes.

The device operates as follows. A thermionic electrode (2) heated to a high temperature emits electrons, which, moving in the electrostatic field created by the power source (7), ionize the space in the vacuum chamber, generating (mainly) positive ions. Positive ions move in the direction of the negative potential relative to the chamber of the workpiece (4) in the electrostatic field created by the power source (6). Hollow cylindrical electrodes (3) form an electrostatic lens, the focal length of which will depend on the ratio between the potentials U1 and U2 of the first and second hollow cylindrical electrodes (3) (L. A. Artsimovich, S. Yu. Lukyanov. Motion of charged particles in electric and magnetic fields. M., 1972, p.15-16). By exposing U2 / U1≥16 using power sources (9) and (10), we position the thermionic electrode at a distance equal to the double inner diameter of the hollow cylindrical electrode, counted from the middle of the gap between the hollow electrodes, i.e. in focus electrostatic lens. This makes it possible to form a parallel stream of ions at the exit of hollow cylindrical electrodes that fall on the surface of the workpiece at an angle α equal to the critical one, which ensures the maximum sputtering coefficient of the workpiece at a given temperature. The temperature of the process of chemical-thermal treatment of the part (4) is adjusted by changing the voltage on the substrate (5) using a power source (6).

Using the proposed device for processing parts in a non-self-contained glow discharge allows you to:

1) increase the endurance limit of parts by lowering the temperature of chemical-thermal treatment,

2) reduce energy costs by reducing the time of chemical-thermal treatment.

Claims (1)

A device for chemical-thermal treatment of a part in a non-self-contained glow discharge, containing a vacuum chamber and a substrate for accommodating parts, a power source connected to a negative pole with a substrate, a positive one to the camera body, a thermionic electrode, a second power source connected to a thermionic electrode with a negative pole, positive - with the camera body, a hollow cylindrical electrode having an inner diameter exceeding the geometric dimensions of the workpiece, and thermionic a second electrode located coaxially with a cylindrical electrode, characterized in that it contains a second hollow cylindrical electrode located coaxially with the first electrode and forming an electrostatic lens with the first electrode, while the axis of symmetry of the hollow cylindrical electrodes is oriented at an angle equal to the critical angle of incidence of the ion flux at the surface of the workpiece, and the thermionic electrode is located in the focus of the electrostatic lens.

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