Plasma coating device and process for inner hole of pipe

Abstract

The pipe inner hole plasma coating device comprises a coating barrel and a barrel cover installed at the upper end of the coating barrel, a rotating clamp used for loading a pipe fitting is installed on the barrel cover, and an auxiliary vacuum chamber used for changing the phase position of the pipe fitting is arranged in the coating barrel. The lower end of the coating barrel is communicated with a first functional chamber, a second functional chamber and a functional vacuum chamber, an anode bar is arranged in the first functional chamber, a cathode bar is arranged in the second functional chamber, and the outer wall of the functional vacuum chamber is sleeved with a coil used for generating axial plasma in the pipe fitting; through the arrangement of the film coating device, etching cleaning, PVD film coating and PECVD film coating of the inner hole of the pipe fitting can be achieved in the same vacuum cavity, the situation that vacuum breaking and furnace discharging cause surface pollution to affect the coating adhesive force and the film layer quality is not needed, and film coating can be conducted on the inner holes of three or more pipe fittings at the same time.

Description

Technical Field

[0001] This invention belongs to the field of materials science and engineering technology, and specifically relates to a plasma coating device and process for the inner hole of a tube. Background Technology

[0002] Inner hole surface coating technology involves coating the inner wall of a pipe with a special material to extend the service life of the pipe and increase its corrosion resistance. Plasma coating technology is widely used in the field of surface treatment due to its advantages such as low temperature, high efficiency and environmental protection.

[0003] However, applying plasma coating technology to the surface of pipe boreholes still faces the following technical challenges: the limited space inside the pipe borehole makes it difficult to form a stable and uniform plasma, making plasma excitation and maintenance difficult; thus affecting the quality of the coating on the surface of the pipe borehole. Therefore, we need to propose a plasma coating device and process for pipe boreholes to solve the above-mentioned problems, so as to achieve a high-efficiency, uniform and environmentally friendly coating process and improve the quality of the coating. Summary of the Invention

[0004] The purpose of this invention is to provide a plasma coating apparatus and process for internal tube pores, which can achieve efficient, uniform and environmentally friendly coating processes, improve coating quality, and solve the problems mentioned in the background art.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A plasma coating apparatus for tube bores includes a coating tank and a tank cover mounted on the upper end of the coating tank. A rotating clamp for loading tubes is installed on the tank cover. An auxiliary vacuum chamber for changing the phase position of the tubes is provided inside the coating tank. A first functional chamber, a second functional chamber, and a functional vacuum chamber are connected to the lower end of the coating tank. An anode rod is provided in the first functional chamber, and a cathode rod is provided in the second functional chamber. A coil for generating axial plasma inside the tubes is sleeved on the outer wall of the functional vacuum chamber. A vent pipe is connected to one side of the coating tank.

[0007] A magnetron is sleeved on the outside of the cathode rod, and a metal target layer is provided on the outer wall of the magnetron.

[0008] Preferably, the rotating clamp includes a rotating shaft rotatably mounted at the center of the barrel lid, a lifting mechanism is mounted at one end of the rotating shaft, a fixing block is mounted at the lower end of the lifting mechanism, a connecting rod is fixed on one side of the fixing block, a sleeve for loading pipe fittings is mounted at one end of the connecting rod, and a driving mechanism for driving the rotating shaft to rotate is mounted at the other end of the rotating shaft.

[0009] Preferably, the lifting mechanism includes an electric telescopic rod, one end of which is connected to one end of a rotating shaft via a mounting base, and the other end of which is fixed to a fixing block. The electric telescopic rod drives the pipe fittings to move to the first functional chamber, the second functional chamber, and the functional vacuum chamber, respectively.

[0010] Preferably, the cathode rod is configured as a bar magnetic rod rotating cylindrical cathode or an annular magnetic rod reciprocating cylindrical cathode.

[0011] Based on the above-described tube-in-hole plasma coating apparatus, the present invention also provides a tube-in-hole plasma coating process, comprising the following steps:

[0012] S1. Load the pipe fittings onto the rotating clamp and place the pipe fittings in the coating barrel;

[0013] S2. Vacuum heating and degassing treatment is performed on the coating tank;

[0014] S3. Etching and cleaning of the inner wall of the pipe by exciting gas ions with an anode rod;

[0015] S4. A coating layer is formed on the inner wall of the pipe by magnetron sputtering of the cathode rod metal target.

[0016] Preferably, in step S2, when the coating tank is evacuated, the vacuum inside the tank is evacuated to 0.005-0.008 Pa, and the heating temperature is raised to 180-550℃. The time required for evacuation and heating is 90-120 min.

[0017] Preferably, in step S3, during the etching and cleaning of the inner wall of the pipe, the pipe is inserted into the first functional chamber, with the anode rod positioned in the inner hole of the pipe. Argon gas is then introduced, and after the argon gas is ionized, the oxide layer on the surface of the workpiece pipe wall is removed using argon ions. The argon gas flow rate is 80-120 sccm, the bias voltage is 200-600V, the anode current is 60-100A, the vacuum degree is 0.08-0.1Pa, and the time taken is 60-80min.

[0018] Preferably, in step S4, when magnetron sputtering the inner wall of the tube, the tube is inserted into the second functional chamber, the cathode rod is located in the inner hole of the tube, and the target material is one of Ti, Cr, Zr, W, Ta, Nb. A metal bonding layer is deposited first, and then the functional layer is deposited.

[0019] Preferably, in step S4, when magnetron sputtering the inner wall of the tube, firstly, a pure metal bonding underlayer of Cr or Ti is magnetron sputtered onto the inner wall of the tube using a cathode rod, then a WC:CH transition layer is reactively sputtered onto the inner wall of the tube using a WC target material of the cathode rod, and finally, a high-power pulsed bias voltage is input into the tube to pyrolyze C2H2 or CH4 gas to obtain hydrocarbon plasma, thereby depositing a DLC coating.

[0020] Preferably, when the WC target of the cathode rod reacts with the inner wall of the tube during magnetron sputtering, the cylindrical WC target is located in the inner hole of the tube, and a coil is wound outside the functional vacuum chamber to generate axial plasma inside the tube. The bias voltage is 500-800V, the vacuum degree is 0.7-1.0Pa, the coil current is 5-10A, the C2H2 / CH4 gas flow rate is 220-360sccm, and the time taken is 150-240min.

[0021] The plasma coating apparatus and process for pipe internal holes proposed in this invention have the following advantages compared with the prior art:

[0022] 1. The present invention, through the setting of the coating device, can realize the etching and cleaning, PVD coating and PECVD coating of the inner hole of the pipe in the same vacuum chamber, without breaking the vacuum to remove the furnace, which would cause surface contamination and affect the coating adhesion and film quality. Furthermore, it can perform coating of the inner hole of three or more pipes at the same time.

[0023] 2. This invention uses loading of pipe fittings, vacuuming, anode rod to excite gas ions to etch the inner wall of the pipe, and cylindrical cathode metal target to magnetron sputter the inner wall of the pipe to deposit functional coatings of metal and its alloys. It can also simultaneously introduce reactive gases to prepare various metal compound coatings.

[0024] 3. The DLC film layer coated on the inner hole of the tube in this invention has good adhesion and can reach the industrial application level. Secondly, due to the presence of a metal underlayer transition layer, defective products can be chemically stripped without damaging the substrate, so as to achieve process reversibility. Furthermore, the plasma coating process for the inner hole of the tube with a large aspect ratio of this application adopts a vacuum coating method, which can reduce environmental pollution and is more green and environmentally friendly. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the present invention;

[0026] Figure 2 This is a cross-sectional three-dimensional structural diagram of the present invention;

[0027] Figure 3 This is a cross-sectional structural diagram of the present invention;

[0028] Figure 4 This is a schematic cross-sectional view of the pipe fittings during coating according to the present invention;

[0029] In the diagram: 1. Coating tank; 2. Tank lid; 3. Rotating clamp; 31. Fixing block; 32. Electric telescopic rod; 33. Rotating shaft; 34. Connecting rod; 35. Sleeve; 4. Vent pipe; 5. First functional chamber; 51. Anode rod; 6. Functional vacuum chamber; 7. Second functional chamber; 71. Cathode rod; 72. Magnetron; 73. Target material layer; 8. Pipe fitting; 81. Coating. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] The present invention provides Figure 1-4 The device for plasma coating of pipe internal holes shown includes a coating tank 1 and a lid 2 installed on the upper end of the coating tank 1. The lid 2 and the coating tank 1 are detachably connected. Specifically, the lid 2 is provided with a buckle, and the coating tank 1 is provided with a groove that matches the buckle. A sealing ring is provided between the lid 2 and the coating tank 1 to ensure a sealed connection between the lid 2 and the coating tank 1. A rotating clamp 3 for loading a pipe 8 is installed on the lid 2. An auxiliary vacuum chamber for changing the phase position of the pipe 8 is provided inside the coating tank 1. The lower end of the coating tank 1 is connected to a first functional chamber 5, a second functional chamber 7 and a functional vacuum chamber 6. An anode rod 51 is provided in the first functional chamber 5, and a cathode rod 71 is provided in the second functional chamber 7. A coil for generating axial plasma inside the pipe 8 is sleeved on the outer wall of the functional vacuum chamber 6. A vent pipe 4 is connected to one side of the coating tank 1.

[0033] A magnetron 72 is sleeved on the outside of the cathode rod 71. A metal target layer 73 is provided on the outer wall of the magnetron 72. The magnetron 72 is composed of multiple ring magnets, which are arranged from top to bottom.

[0034] The rotating clamp 3 includes a rotating shaft 33 rotatably mounted at the center of the barrel cover 2. A lifting mechanism is installed at one end of the rotating shaft 33, and a fixing block 31 is installed at the lower end of the lifting mechanism. A connecting rod 34 is fixed on one side of the fixing block 31. A sleeve 35 for loading the pipe fitting 8 is installed at one end of the connecting rod 34. A driving mechanism for driving the rotating shaft 33 to rotate is installed at the other end of the rotating shaft 33. The sleeve 35 is T-shaped in side view. When loading the pipe fitting 8, the pipe fitting 8 can be sleeved on the T-shaped block, which is simple to operate.

[0035] The drive mechanism includes a bracket and a stepper motor. The bracket is fixed on the upper surface of the barrel cover 2, and the stepper motor is mounted on the bracket for support. The output shaft of the stepper motor is keyed to the upper end of the rotating shaft 33, so that the stepper motor can drive the rotating shaft 33 to rotate. The rotating shaft 33 drives the connecting rod 34 and the sleeve 35 to move in a circle, moving the tube 8 on the sleeve 35 to the first functional chamber 5, the second functional chamber 7, and the functional vacuum chamber 6 respectively. Then, the electric telescopic rod 32 drives the sleeve 35 to move downward, pushing the tube 8 into the first functional chamber 5, the second functional chamber 7, and the functional vacuum chamber 6 to change the relative position of the tube 8.

[0036] The lifting mechanism includes an electric telescopic rod 32. One end of the electric telescopic rod 32 is connected to one end of the rotating shaft 33 through a mounting base. The other end of the electric telescopic rod 32 is fixed to the fixing block 31. The electric telescopic rod 32 drives the pipe 8 to move into the first functional chamber 5, the second functional chamber 7 and the functional vacuum chamber 6 respectively.

[0037] The cathode rod 71 is configured as a bar magnetic rod rotating cylindrical cathode or an annular magnetic rod reciprocating cylindrical cathode.

[0038] With the coating device, etching and cleaning, PVD coating and PECVD coating of the inner hole of the pipe 8 can be achieved in the same vacuum chamber. There is no need to break the vacuum to remove the tube from the furnace, which would cause surface contamination and affect the adhesion and quality of the coating. Furthermore, coating of the inner hole of three or more pipes 8 can be performed simultaneously.

[0039] Based on the above-described tube-in-hole plasma coating apparatus, the present invention also provides a tube-in-hole plasma coating process, comprising the following steps:

[0040] S1. Load the pipe fitting onto the rotating fixture and place the pipe fitting in the coating tank; before loading the pipe fitting, the plasma coating process for the inner hole of the pipe also includes a pretreatment step of the pipe fitting, which involves ultrasonically cleaning the pipe fitting with organic solvent or deionized water to remove stains from the surface and inner wall of the pipe fitting.

[0041] S2. Vacuum treatment is performed on the coating tank. When vacuuming the coating tank, the vacuum inside the tank is evacuated to 0.005-0.008Pa, and the temperature is heated to 400-550℃. The time required for vacuuming and heating is 90-120 minutes.

[0042] S3. Etching of the inner wall of the pipe by stimulating gas ions through the anode rod; During the etching of the inner wall of the pipe, the pipe is inserted into the first functional chamber, the anode rod is located in the inner hole of the pipe, argon gas is filled in, and after the argon gas is ionized, the oxide layer on the surface of the workpiece and the pipe wall is removed by argon ions. The argon gas flow rate is 80-120 sccm, the bias voltage is 200-600V, the anode current is 60-100A, the vacuum degree is 0.08-0.1Pa, and the time taken is 60-80min.

[0043] S4. Magnetron sputtering is performed on the inner wall of the pipe using a cathode rod metal target to form a coating layer. During magnetron sputtering, the pipe is inserted into the second functional chamber, with the cathode rod located inside the pipe's inner hole. The target material is one of Ti, Cr, Zr, W, Ta, or Nb. Ar gas can be introduced to prepare functional coatings of metals and their alloys such as Ti, Cr, Zr, W, Ta, and Nb. Alternatively, reactive gases such as N2, C2H2, CH4, and O2 can be introduced to prepare various nitrides and carbides. For carbonitride and oxide wear-resistant coatings, a metal bonding layer must first be deposited with an argon gas flow rate of 60-80 sccm, a bias voltage of 50-100V, a vacuum degree of 0.2-0.5Pa, a target current of 10-15A, and a time of 5-10 minutes. Then, a functional layer is deposited with an argon gas flow rate of 60-80 sccm, a bias voltage of 50-100V, a vacuum degree of 0.3-0.6Pa, a target current of 10-15A, a reaction gas flow rate of 30-60 sccm, and a time of 100-120 minutes.

[0044] Functional coatings of metals and their alloys can be deposited by loading pipes, drawing a vacuum, using gas ions excited by an anode rod to etch the inner wall of the pipe, and using a cylindrical cathode metal target to magnetron sputter the inner wall of the pipe. Various metal compound coatings can also be prepared by simultaneously introducing reactive gases.

[0045] Example 2

[0046] The similarities will not be repeated here. Unlike Example 1, this invention also provides a plasma coating process for pipe internal holes, comprising the following steps:

[0047] S1. Load the pipe fitting onto the rotating fixture and place the pipe fitting in the coating tank; before loading the pipe fitting, the plasma coating process for the inner hole of the pipe also includes a pretreatment step of the pipe fitting, which involves ultrasonically cleaning the pipe fitting with organic solvent or deionized water to remove stains from the surface and inner wall of the pipe fitting.

[0048] S2. Vacuum treatment is performed on the coating tank; when vacuuming the coating tank, the vacuum inside the tank is evacuated to 0.005-0.008Pa, and the temperature is heated to 150-200℃. The time required for vacuuming and heating is 90-120min.

[0049] S3. Etching of the inner wall of the pipe by exciting gas ions with an anode rod;

[0050] S4. Magnetron sputtering of the inner wall of the pipe using a cathode rod metal target, and magnetron sputtering of Cr or Ti pure metal bonding underlayers on the inner wall of the pipe using a cathode rod.

[0051] S5. Reactive magnetron sputtering of WC:CH transition layer on inner wall of tube using WC target material with cathode rod; During reactive magnetron sputtering of inner wall of tube using WC target material with cathode rod, cylindrical WC target material is located in inner hole of tube fitting, coil is wound outside functional vacuum chamber to generate axial plasma inside tube fitting, bias voltage 500-800V, vacuum degree 0.7-1.0Pa, coil current 5-10A, C2H2 / CH4 gas flow rate 220-360sccm, time taken 150-240min;

[0052] S6. Input a high-power pulsed bias voltage into the tube to crack C2H2 or CH4 gas to obtain hydrocarbon plasma and deposit a DLC coating 81. The bias voltage is 700-800V, the coil current is 5-10A, the C2H2 / CH4 gas flow rate is 300-500sccm, and the time taken is 180-210min.

[0053] The process involves loading the tube, evacuating it, exciting gas ions with an anode rod to etch the inner wall of the tube, magnetron sputtering a Cr and Ti pure metal bonding layer onto the inner wall of the tube using a cylindrical cathode metal target, reactive magnetron sputtering a WC:CH transition layer onto the inner wall of the tube using a cylindrical cathode WC target, and then inputting a high-power pulse bias voltage into the tube (simultaneously activating a coil outside the functional vacuum chamber to generate axial plasma inside the tube) to create a hollow cathode effect in the inner hole of the tube, breaking down the C2H2 / CH4 gas that can enter the cavity to obtain hydrocarbon plasma, thereby depositing a diamond-like carbon (DLC) amorphous carbon film.

[0054] For example, NbN thin films are deposited on the inner wall of a 304 stainless steel tube. The specific process steps are as follows:

[0055] Pre-treat the pipe fittings by ultrasonic cleaning with organic solvents or deionized water to remove stains from the surface and inner wall of the pipe fittings and then dry them.

[0056] In the auxiliary vacuum chamber, load the tube onto a rotatable fixture; evacuate to a vacuum level of 0.005-0.008 Pa and heat to 400-550℃; insert the tube into the functional vacuum chamber containing the anode rod, with the anode rod positioned inside the tube bore, at a vacuum level of 0.08-0.1 Pa; fill with argon gas at a flow rate of 80-120 sccm; ionize the argon gas using an anolyte current of 60-100 A and a bias voltage of 200-600 V; use argon ions to remove the oxide layer from the workpiece and tube wall surface, etching for a total of 60-80 minutes; return the tube to the auxiliary vacuum chamber and adjust its position. Place the cylindrical Nb target into the functional vacuum chamber, with the target located in the inner hole of the tube. First, deposit an Nb binder layer with a vacuum of 0.2-0.5 Pa, an argon flow rate of 60-80 sccm, a bias voltage of 50-100 V, and a target current of 10-15 A for 5-10 min. Then, deposit an NbN layer with a vacuum of 0.3-0.6 Pa, an argon flow rate of 60-80 sccm, a bias voltage of 50-100 V, a target current of 10-15 A, and an N2 flow rate of 30-60 sccm for 100-120 min.

[0057] The resulting NbN film is uniform and dense, with good coating integrity on the inner wall of the tube. The film thickness is 2-3 μm, the scratch adhesion is 30-60 N, the coefficient of friction at room temperature (10 N) is 0.3-0.4, and the wear rate is 1-3 × 10⁻⁶. -6 mm 3 N -1 m -1 .

[0058] For example, the deposition of a Cr-WC-DLC thin film on the inner wall of a 304 stainless steel tube is carried out using the following specific process steps:

[0059] Pre-treat the pipe fittings by ultrasonic cleaning with organic solvents or deionized water to remove stains from the surface and inner wall of the pipe fittings and then dry them.

[0060] In the auxiliary vacuum chamber, load the tube onto a rotatable fixture; evacuate to a vacuum level of 0.005-0.008 Pa and heat to 150-200℃; insert the tube into the functional vacuum chamber containing the anode rod, with the anode rod positioned inside the tube's bore, maintaining a vacuum level of 0.08-0.1 Pa. Inject argon gas at a flow rate of 80-120 sccm, ionize the argon gas with an anolyte current of 60-100 A and a bias voltage of 200-600 V, and use argon ions to remove the oxide layer from the workpiece and tube wall surface, etching for a total of 60-80 minutes; retract the tube into the auxiliary vacuum chamber, adjust its position, and insert it into the functional vacuum chamber containing the cylindrical Cr or Ti target, with the cylindrical target positioned inside the tube's bore, depositing a pure Cr or Ti binder layer, maintaining a vacuum level of 0.2-0.5 Pa, an argon flow rate of 60-80 sccm, and a bias voltage of 50-100 V. Target current 10-15A, time 5-10min; retract the tube into the auxiliary vacuum chamber, adjust its position and insert it into the functional vacuum chamber with a cylindrical WC target material located in the inner hole of the tube. A coil is wound outside the functional vacuum chamber to generate axial plasma inside the tube and deposit a WC:CH transition layer. Vacuum degree 0.7-1.0Pa, bias voltage 500-800V, coil current 5-10A, C2H2 gas flow rate 220-360sccm, time 150-240min; retract the tube into the auxiliary vacuum chamber, adjust its position and insert it into the functional vacuum chamber without a cathode target material and with a coil wound outside to deposit a DLC layer. Bias voltage 700-800V, coil current 5-10A, C2H2 gas flow rate 300-500sccm, time 180-210min.

[0061] The resulting Cr-WC-DLC film is uniform and dense, with good coating integrity on the inner wall of the tube. The film thickness is 4-5 μm, and the scratch adhesion force is 30-40 N, which meets the industrial application level. The coefficient of friction at room temperature is 0.05-0.15 at 10 N, and the wear rate is 5-10 × 10⁻⁶. - 7 mm 3 N -1 m -1 It also has excellent corrosion resistance.

[0062] The DLC film coating applied to the inner hole of the tube has good adhesion and can reach the industrial application level. Secondly, due to the presence of a metal underlayer transition layer, defective products can be chemically stripped without damaging the substrate, thus achieving process reversibility. Furthermore, the plasma coating process for the inner hole of the tube with a large aspect ratio of this application adopts a vacuum coating method, which can reduce environmental pollution and is more green and environmentally friendly.

[0063] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A plasma coating apparatus for the inner hole of a tube, characterized in that: The coating includes a coating tank (1) and a lid (2) installed on the upper end of the coating tank (1). A rotating clamp (3) for loading a pipe (8) is installed on the lid (2). An auxiliary vacuum chamber for changing the phase position of the pipe (8) is provided inside the coating tank (1). A first functional chamber (5), a second functional chamber (7) and a functional vacuum chamber (6) are connected to the lower end of the coating tank (1). An anode rod (51) is provided in the first functional chamber (5). A cathode rod (71) is provided in the second functional chamber (7). A coil for generating axial plasma in the pipe (8) is sleeved on the outer wall of the functional vacuum chamber (6). A ventilation pipe (4) is connected to one side of the coating tank (1). A magnetron (72) is sleeved on the outside of the cathode rod (71), and a metal target layer (73) is provided on the outer wall of the magnetron (72).

2. The plasma coating apparatus for tube bores according to claim 1, characterized in that: The rotating clamp (3) includes a rotating shaft (33) rotatably mounted at the center of the barrel cover (2). A lifting mechanism is installed at one end of the rotating shaft (33), and a fixing block (31) is installed at the lower end of the lifting mechanism. A connecting rod (34) is fixed on one side of the fixing block (31). A sleeve (35) for loading pipe fittings (8) is installed at one end of the connecting rod (34), and a driving mechanism for driving the rotating shaft (33) to rotate is installed at the other end of the rotating shaft (33).

3. The plasma coating apparatus for tube bores according to claim 2, characterized in that: The lifting mechanism includes an electric telescopic rod (32), one end of which is connected to one end of a rotating shaft (33) via a mounting base, and the other end of which is fixed to a fixing block (31). The electric telescopic rod (32) drives the pipe (8) to move into the first functional chamber (5), the second functional chamber (7), and the functional vacuum chamber (6), respectively.

4. The plasma coating apparatus for tube bores according to claim 3, characterized in that: The cathode rod (71) is configured as a bar magnetic rod rotating cylindrical cathode or an annular magnetic rod reciprocating cylindrical cathode.

5. A plasma coating process for pipe internal holes, comprising a plasma coating apparatus for pipe internal holes according to any one of claims 1-4, characterized in that: Includes the following steps: S1. Load the pipe fitting (8) onto the rotating clamp (3) and place the pipe fitting (8) into the coating barrel (1); S2. Vacuum treatment is performed on the coating tank (1); S3. Etching of the inner wall of the pipe fitting (8) by gas ions excited by the anode rod (51); S4. A coating layer is formed on the inner wall of the tube (8) by magnetron sputtering of the metal target material of the cathode rod (71).

6. The plasma coating process for the inner hole of a tube according to claim 5, characterized in that: In step S2, when the coating tank (1) is evacuated, the vacuum inside the tank is evacuated to 0.005-0.008 Pa and the temperature is heated to 400-550℃. The time required for evacuation and heating is 90-120 min.

7. The plasma coating process for pipe internal holes according to claim 6, characterized in that: In step S3, when etching the inner wall of the tube (8), the tube (8) is inserted into the first functional chamber (5), so that the anode rod (51) is located in the inner hole of the tube (8), and argon gas is filled in. After the argon gas is ionized, the oxide layer on the surface of the workpiece and the tube wall is removed by argon ions. The argon gas flow rate is 80-120 sccm, the bias voltage is 200-600V, the anode current is 60-100A, the vacuum degree is 0.08-0.1Pa, and the time taken is 60-80min.

8. The plasma coating process for the inner hole of a tube according to claim 7, characterized in that: In step S4, when magnetron sputtering the inner wall of the tube (8), the tube (8) is inserted into the second functional chamber (7), the cathode rod (71) is located in the inner hole of the tube (8), and the material of the target layer (73) is one of Ti, Cr, Zr, W, Ta and Nb. A metal bonding layer is deposited first, and then the functional layer is deposited.

9. The plasma coating process for the inner hole of a tube according to claim 7, characterized in that: In step S4, when magnetron sputtering the inner wall of the tube (8), firstly, a pure metal bonding layer of Cr or Ti is magnetron sputtered onto the inner wall of the tube through the cathode rod (71), then a WC:CH transition layer is reactively sputtered onto the inner wall of the tube through the WC target of the cathode rod (71), and finally, the tube (8) is input with a high-power pulse bias voltage to crack C2H2 or CH4 gas to obtain hydrocarbon plasma and thus deposit a DLC coating.

10. The plasma coating process for the inner hole of a tube according to claim 9, characterized in that: When the WC target of the cathode rod (71) reacts with the inner wall of the tube during magnetron sputtering, the cylindrical WC target is located in the inner hole of the tube (8). A coil is wound around the outside of the functional vacuum chamber (6) to generate axial plasma in the tube (8). The bias voltage is 500-800V, the vacuum degree is 0.7-1.0Pa, the coil current is 5-10A, the C2H2 / CH4 gas flow rate is 220-360sccm, and the time taken is 150-240min.

Images