Pipe barrel inner wall coating preparation method and device based on bipolar magnetron sputtering

Abstract

The invention provides a method and a device for preparing a coating on the inner wall of a pipe barrel based on bipolar magnetron sputtering, and the uniform and continuous coating on the inner wall of the pipe barrel is prepared on the inner wall of the deep pipe barrel by improving a magnetic field structure on the basis of existing magnetron sputtering equipment. Specifically, the device comprises a tube barrel and a tubular target arranged in the tube barrel, and the tube barrel and the tubular target are insulated. In the preparation process of the coating on the inner wall of the pipe barrel, the pipe barrel and the tubular target can be mutually positive and negative electrodes and can also be respectively connected with a direct-current power supply, a pulse power supply or a radio-frequency power supply according to the requirements of a coating process, and the tubular target must have the time when the potential is negative relative to the pipe barrel. At least two closed magnetic fields with magnetic induction lines distributed in an arch shape and penetrating through the target surface are constructed on the surface of the tubular target through a permanent magnet or an electromagnetic coil or a combination of the permanent magnet and the electromagnetic coil, at least one divergent magnetic field mainly perpendicular to the target surface component exists between two annular runways, and magnetic lines of the divergent magnetic field on the surface of the tubular target are dense. And the inner wall of the pipe barrel far away from the target surface is loosened. And part of high-energy electrons are guided to move towards the inner wall of the pipe barrel through magnetic induction lines, so that the density of ions reaching the inner wall of the pipe barrel is improved, and high-speed and high-quality preparation of the inner wall coating of the pipe barrel is realized.

Description

Technical Field

[0001] The present invention belongs to the field of vacuum physical vapor deposition (PVD) coating technology, and relates to a method and device for preparing inner wall coating of a tube based on magnetron sputtering. It can be used for inner wall coating of metal tubes, including but not limited to military gun barrels, cannon barrels, offshore drilling and natural gas transmission systems, tubes and valves for conveying corrosive materials, and inner surface modification treatment of automobile engine cylinders and piston parts. Background Art

[0002] In industrial production, there are a large number of inner walls of pipes that need coating protection, especially for tubular workpieces, such as oil pump barrels, chemical pipelines, and oil pipelines in the oil industry, as well as in the military field, especially the inner walls of naval gun barrels and torpedo launch barrels configured on naval ships, which work in harsh environments. Ordinary treatment methods cannot meet the internal surface strengthening requirements. These workpieces fail early due to wear, corrosion, and oxidation of the inner wall. Therefore, the development of a surface coating method and device with anti-wear, anti-corrosion, and anti-oxidation properties is a problem that urgently needs to be solved in the field of inner wall coating of pipes.

[0003] Compared with the outer surface of the workpiece, the preparation of the inner wall coating of the tubular workpiece mainly has the following technical difficulties: 1. Since the area to be treated is located inside the tube, some treatment methods are difficult to implement. 2. Even if the method is implemented, it is difficult to get a good effect, and the uniformity of the film thickness and the bonding strength of the film base cannot be guaranteed. For the inner wall coating of metal tubes, people first proposed to use electroplating and chemical plating for treatment. However, chemical plating often uses harmful chemicals and pollutes the environment; although electroplating reduces the use of harmful chemicals and the coating effect is improved to a certain extent, there is still a problem of poor bonding and easy peeling during use.

[0004] Ma Zhibin, Wang Jianhua, Wan Jun, He Aihua, and Zhang Lei from Wuhan University of Technology invented a method and device for coating (like) diamond film inside or outside of a quartz tube (invention patent: 200710051833.0). The method first uses microwaves to excite the working gas discharge to generate a cylindrical plasma between two coaxially placed quartz tubes, and then uses plasma chemical vapor deposition technology to plate diamond or diamond-like film on the outer wall of the inner quartz tube or the inner wall of the outer quartz tube. Zhao Yanhui, Yu Baohai, and Xiao Jinquan from the Institute of Metal Research, Chinese Academy of Sciences, invented a method for depositing a film on the inner surface of a long tube by plasma enhanced chemical vapor deposition (PECVD) (invention patent: 201310329125.4). The method places the slender metal tube to be processed in a tube-shaped vacuum chamber, places a tungsten wire electrode in the central axis of the metal tube-shaped workpiece, introduces working gas into the metal tube, applies a DC pulse or radio frequency signal between the tungsten wire electrode and the vacuum chamber wall, and excites the discharge to generate plasma. This method uses the inner wall of the tube as an electrode to generate plasma. The tube must be a conductor, so deposition can only be performed on the inner wall of the metal tube. Ralf Stein of Germany invented a plasma-assisted chemical vapor deposition method and device (a method and device for plasma-assisted chemical vapor deposition on the inner wall of a hollow body. Patent of this invention: 200780026008.3). The hollow body to be processed is placed in a vacuum chamber, a large-area RF electrode is placed inside the vacuum chamber, and a gas-fired spray gun is placed in the hollow body. After the gas is introduced, a radio frequency electric field is applied to the RF electrode to ignite the plasma cavity, and a plasma cloud is formed at the tip of the gas-fired spray gun to achieve coating on the inner wall of the hollow body. The device can deposit coatings such as DLC, TiOx, and SiO2. Li Zhifang and others from Guangdong Huicheng Vacuum Technology Co., Ltd. (CN202410746324.3) proposed a magnetron sputtering target for coating the inner wall of a slender tube with water entering and exiting the upper and lower ends respectively. The invention directly distributes gas to the upper, middle and lower positions of the slender tube through the gas distribution duct inside the target tube assembly. At the same time, the target tube assembly also rotates to make the gas distribution more uniform, thereby solving the problem of uniform coating on the inner wall of the slender tube.

[0005] Although the above technology solves the problem of whether or not to coat the inner wall of the tube, it is still not able to achieve the optimal level in terms of more fully utilizing the electromagnetic confinement of the plasma. The bonding strength and density of the inner wall coating of the tube still need to be improved, and a new inner wall coating method is urgently needed. Summary of the invention

[0006] The purpose of the present invention is to improve the magnetic field structure design on the basis of the existing magnetron sputtering equipment, so as to prepare a uniform and continuous tube inner wall coating on the inner wall of a deep tube.

[0007] Technical solution: To achieve the above-mentioned purpose, the present invention provides a method and device for preparing a coating on the inner wall of a tube. Specifically, by designing a magnetic field structure, some electrons are bound in a plasma region close to the target surface, thereby increasing the plasma density in the near-target region and making full use of the electric field energy. At the same time, the divergent magnetic field generates field lines pointing to the inner wall of the tube, guiding another part of the secondary electrons to follow the field lines and flow out to the inner wall of the tube, thereby extracting a higher ion flow from the plasma, thereby achieving the purpose of fast and high-quality magnetron sputtering film preparation on the inner wall of the tube.

[0008] As a preferred solution, the tube and the tubular target are insulated.

[0009] As a preferred solution, the tube can be a straight tube, a U-shaped tube, or a special-shaped tube with uneven thickness.

[0010] As a preferred solution, the tube and the tubular target can be each other's positive and negative poles or connected to a power source separately according to coating requirements.

[0011] As a preferred solution, the power source connected to the tube and the tubular target can be a DC power source, a pulse power source, a radio frequency power source, etc., or a combination of several power sources.

[0012] As a preferred solution, during the process of preparing the inner wall coating of the tube, the tubular target must have a time when the potential relative to the inner wall of the tube is negative.

[0013] As a preferred solution, the surface of the tubular target has at least two closed magnetic fields with arc-shaped magnetic flux lines passing through the target surface. The magnetic field can be formed by a permanent magnet, an electromagnetic coil, or a combination of the two.

[0014] As a preferred embodiment, the magnetic field forms at least two annular tracks parallel to the target surface on the surface of the tubular target, and there is at least one divergent magnetic field mainly composed of a magnetic field perpendicular to the target surface between the two annular tracks. The magnetic lines of force of the divergent magnetic field are denser at the target surface and looser when away from the target surface.

[0015] As a preferred embodiment, the method for preparing the tube inner wall coating based on magnetron sputtering is carried out under vacuum, and the vacuum degree during the preparation process is between 1x10-2Pa and 100Pa.

[0016] As a preferred solution, the tube can be placed in a large vacuum chamber, or the tube itself can serve as a vacuum chamber.

[0017] Effects and benefits of the present invention: The method and device for coating the inner wall of a tube of the present invention solves the problem that the opening of a tube with a small diameter has a natural electromagnetic shielding effect on the electric field, thereby preventing the tube from shielding the plasma during the coating process. It solves the problem of uneven coating thickness deep inside the inner wall of the tube and at the entrance caused by uneven plasma distribution.

[0018] The method and device for coating the inner wall of a tube of the present invention further improve the ionization of the gas on the inner wall of the tube through the cooperation of a bipolar power supply and a magnetic field, increase the density and energy of ions in the plasma, and the high-density plasma can greatly improve the deposition efficiency of the coating, solving the problem of insufficient bonding strength of the coating.

[0019] The method and device for coating the inner wall of a tube of the present invention can realize the switching of reciprocating polarity between the inner wall of the tube and the target material through a bipolar power supply, can neutralize the charge accumulation on the surface of the insulating coating, prevent sparking, and realize high-performance coating preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 1 is a radial cross-sectional schematic diagram of a magnetic field configuration embodiment 1 of a method and apparatus for preparing a tube inner wall coating based on magnetron sputtering, wherein 101 is the inner wall of the tube, 102 is the surface of a cylindrical target, 103 is a permanent magnet with an S pole at the upper end and an N pole at the lower end, and 104 and 105 are permanent magnets with an N pole at the upper end and an S pole at the lower end; Figure 2 201 is an axial cross-sectional schematic diagram of a magnetic field configuration embodiment 2 of a method and apparatus for preparing a tube inner wall coating based on magnetron sputtering, wherein 203 is an inner wall of a tube, 202 is a tubular target surface, 203 is a permanent magnet with an N pole at the upper end and an S pole at the lower end, and 204 and 205 are permanent magnets with an S pole at the upper end and an N pole at the lower end; Figure 3 It is a schematic axial cross-sectional view of the method for preparing the inner wall coating of a tube under the magnetic field configuration embodiment 2, wherein 301 is the inner wall of the tube, 302 is the tubular target, 303 is the magnetic pole, 304 is the DC bias power supply, and 305 is the magnetron sputtering power supply.

[0021] Figure 4 Schematic diagram of power supply discharge waveform of an embodiment of a method for preparing inner wall coating of a tube based on magnetron sputtering, wherein (a) is a schematic diagram of power supply discharge waveform connected to a cylindrical target, and (b) is a schematic diagram of power supply discharge waveform connected to a tube DETAILED DESCRIPTION

[0022] The following is a further description of a method and device for preparing a tube inner wall coating based on magnetron sputtering according to the present invention in conjunction with specific embodiments. It should be noted that these embodiments are only used to illustrate the concept of the present invention and are not used to limit the scope of this patent. In addition to the real-time method described herein, those skilled in the art may also adopt other obvious technical methods based on the contents disclosed in the claims and the specification of this application, and these equivalent forms also fall within the scope defined by the claims attached to this application.

[0023] This embodiment relates to a method and device for preparing a tube inner wall coating based on magnetron sputtering, which mainly includes a tube and a tubular target placed in the tube and insulated from the tube. By designing the magnetic field structure, two closed magnetic fields with arc-shaped magnetic flux lines passing through the target surface are constructed on the surface of the tubular target. There is a divergent magnetic field with a component magnetic field perpendicular to the target surface as the main component between two circular tracks parallel to the target surface, and the magnetic flux lines of the divergent magnetic field are denser at the target surface and looser when away from the target surface. Figure 1 The figure shows a radial cross-sectional view of the tube and tubular target of Example 1, wherein 101 is the inner wall of the tube, 102 is the surface of the tubular target, 103 is a permanent magnet with an S pole at the upper end and an N pole at the lower end, and 104 and 105 are permanent magnets with an N pole at the upper end and an S pole at the lower end. There is a vacuum environment between the inner wall 101 of the tube and the surface 102 of the tubular target, and the two are insulated. The permanent magnets 103, 104, and 105 are arranged along the circumference of the tubular target on the radial plane of the tubular target, wherein 103 and 104, 105 respectively constitute two closed magnetic fields, with circular tracks between them; the magnetic flux lines at 104 and 105 are denser when they are close to the surface of the tubular target, and are sparser when they are away from the target surface and close to the inner wall of the tube. Figure 2 The figure shows an axial cross-sectional view of the tube and tubular target of Example 2, wherein 201 is the inner wall of the tube, 202 is the surface of the tubular target, 203 is a permanent magnet with an N pole at the upper end and an S pole at the lower end, and 204 and 205 are permanent magnets with an S pole at the upper end and an N pole at the lower end. The inner wall 201 of the tube and the tubular target 202 are in a vacuum environment and are insulated from each other. The permanent magnets 203, 204, and 205 are arranged along the axial direction of the tubular target on the axial plane of the tubular target, wherein 203 and 204, 205 respectively form two closed magnetic fields, and there are circular runways between them; the magnetic flux lines at 204 and 205 are denser when they are close to the surface of the tubular target, and are sparser when they are far away from the target surface and close to the inner wall of the tube.

[0024] Figure 3 Schematic diagram of the method for preparing the inner wall coating of the tube in the magnetic field of Example 2, wherein 301 is the inner wall of the tube, 302 is the tubular target, 303 is the magnetic pole, 304 is the DC bias power supply, and 305 is the magnetron sputtering power supply. The bias power supply 304 is connected to the tube, the magnetron sputtering power supply 305 is connected to the tubular target, and the tube is insulated from the tubular target. In this embodiment, the magnetron sputtering power supply is a bipolar pulse power supply, and its discharge waveform is as follows: Figure 4As shown in (a), the bias power supply is a DC power supply, and its discharge waveform is as follows Figure 4 (b) After assembly, the pipe is pumped to 1×10 -3 Pa background vacuum, argon is introduced, and the deposition pressure is adjusted to 0.5Pa. During the negative bias period, the voltage of the tubular target is lower than the DC negative bias on the tube. The free electrons collide with the argon atoms between the two, causing the argon to ionize and produce ions and electrons. The argon ions are accelerated to the target surface under the action of the electric field, bombarding the target surface to cause the target atoms to escape. The magnetic flux lines parallel to the target surface in the runway area can limit the movement of some electrons near the surface of the tubular target, increase the probability of ionization caused by collision between electrons and atoms on the target surface, increase the plasma density on the target surface, further increase the bombardment of ions on the surface of the tubular target, increase the sputtering rate, and provide a higher deposition rate for the preparation of the inner wall coating of the tube. Since there is a divergent magnetic field dominated by the vertical target surface component magnetic field between the two circular runways, and it is dense when close to the target surface and sparse when away from the target surface and close to the inner wall of the tube, some secondary electrons can follow the field lines to flow to the inner wall of the tube, thereby extracting a larger ion current and further increasing the deposition rate. At the same time, the bipolar pulse power supply switches to a positive pulse after a negative pulse, and the ions obtain higher energy under the electric field, accelerating their movement toward the inner wall of the tube, thereby improving the bonding force of the prepared coating.

Claims

1. A method and device for preparing inner wall coating of a tube based on magnetron sputtering, characterized in that: The invention comprises a tube and a tubular target arranged inside the tube, wherein the tubular target is insulated from the tube.

2. The method and device for preparing inner wall coating of a tube based on magnetron sputtering according to claim 1, characterized in that: The tube can be placed in a large vacuum chamber, or the tube itself can serve as a vacuum chamber.

3. The method and device for preparing inner wall coating of a tube based on magnetron sputtering according to claim 1, characterized in that: The tube can be a straight tube, a U-shaped tube or a special-shaped tube with uneven thickness.

4. The method and device for preparing inner wall coating of a tube based on magnetron sputtering according to claim 1, characterized in that: The surface of the tubular target has at least two closed magnetic fields in which magnetic flux lines are distributed in an arc shape and pass through the target surface.

5. The method and device for preparing inner wall coating of a tube based on magnetron sputtering according to claim 1, characterized in that: The coating preparation method is carried out under vacuum, and the vacuum degree during sputtering is 1x10 -2 Between Pa and 100Pa.

6. The method and device for preparing inner wall coating of a tube based on magnetron sputtering according to claim 1, characterized in that: The tube and the tubular target can be positive and negative electrodes to each other, and can also be connected to a DC power supply, a pulse power supply or a radio frequency power supply according to the coating requirements, wherein the tubular target must have a time when the potential relative to the tube is negative.

7. The closed magnetic field with arc-shaped distribution of magnetic flux lines according to claim 4, characterized in that: It can be formed by a permanent magnet, an electromagnetic coil, or a combination of the two.

8. The closed magnetic field in which the magnetic flux lines are distributed in an arc shape and pass through the target surface according to claim 4, characterized in that: At least two circular tracks are formed on the target surface.

9. The circular runway according to claim 6, characterized in that: There is at least one divergent magnetic field dominated by a component magnetic field perpendicular to the target surface between the two annular runways, and the divergent magnetic field has dense magnetic lines of force at the target surface and is sparse at a location far from the target surface and close to the inner wall of the tube.

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