A coating device and coating method for inner wall of a tube body

Abstract

The invention discloses a coating device for the inner wall of a tube body, comprising a furnace body, which is a double-layer vacuum furnace and serves as an anode, and the furnace wall is cooled by circulating water; a furnace bottom tray is arranged on the inner side of the bottom of the furnace body, and the furnace bottom tray is connected to a rod-shaped anode and a workpiece bearing tray, and a hollow target material and auxiliary tooling are arranged on the workpiece bearing tray, and the rod-shaped anode passes through the hollow target material, and the auxiliary tooling is used for heat preservation and support of the hollow target material, and a tubular workpiece is arranged on the outer side of the hollow target material and the inner side of the auxiliary tooling; a workpiece cathode and a target material cathode are also arranged in the furnace body, and the workpiece cathode is connected to the workpiece bearing tray, and the workpiece bearing tray is conductively connected to the tubular workpiece, and the target material cathode is connected to the hollow target material through a connecting guide rod; the workpiece cathode and the power supply 2 and the furnace body form a loop to generate glow discharge; the target material cathode and the power supply 1 and the furnace body form a loop to generate glow discharge. When the present invention processes tubular workpieces, the coating can be designed with strong designability, and the elements can be selected in a rich variety, such as metals and their alloys or conductive ceramics.

Description

Technical Field

[0001] The invention relates to a coating device and a method, in particular to a coating device for the inner wall of a tube and a coating method thereof. Background Art

[0002] The inner wall of metal pipes is prone to corrosion, wear, oxidation and other problems in its working environment. In actual use, it is necessary to prepare a protective coating on its inner wall. Due to the complex structural bending of such components, it is difficult to protect the inner wall surface. Large-scale protection is mainly based on electroplating or paint coating. For components in harsh environments, such as weapon barrels and automobile cylinders, not only does the protection effect of current methods need to be improved, but as environmental and energy problems become increasingly serious, it is increasingly necessary to develop green and efficient inner wall surface modification technologies and equipment for tubular components.

[0003] After decades of development, plasma surface modification technology has attracted much attention for its unique advantages. However, the technology currently known by relevant industry technicians still has certain problems and cannot be widely used. For example, plasma chemical vapor deposition has great restrictions on the types of coatings, and the uniformity of the coatings prepared on such components is poor; although magnetron sputtering can deposit a wide range of thin films, the bonding method between the film layer and the pipe wall is mechanical, which does not meet the requirements of use under stress; although arc ion plating has a fast rate and high deposition quality, as the pipe depth increases, the plasma decreases, it is difficult to coat the film, and there are strict restrictions on the length of the pipe.

[0004] The Chinese patent with application number 202210997864.X discloses a method for accelerating alloy powder sputtering coating in a slender metal tube by a spiral wave plume. The spiral wave plasma plume and molten droplets are sprayed onto the alloy sputtering target in the metal tube to produce negatively charged alloy droplets with a diameter of less than 35um and capable of sputtering 360°. A positive voltage is applied between the sputtering target and the metal tube to accelerate the alloy droplets so that the speed of the alloy droplets reaches 2000m / s. The high-speed alloy droplets melt the substrate on the inner wall of the metal tube and form a metallurgical molten alloy coating. However, the inner wall coating prepared by this method has a rough surface, insufficient overall uniformity, and large internal stress in the coating after the metal droplets solidify.

[0005] Therefore, it is an urgent problem to develop new surface modification technologies that have good bonding strength, are clean and efficient, and are suitable for uniform coating on the inner walls of tubular components, especially for coating on the inner walls of pipes that require high-quality coatings. Summary of the invention

[0006] Purpose of the invention: In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a green, efficient and uniformly coated tube inner wall coating device. Another purpose of the present invention is to provide a tube inner wall coating method with a fast coating rate.

[0007] Technical solution: The coating device for the inner wall of a tube body described in the present invention comprises a furnace body, which is a double-layer vacuum furnace and serves as an anode, and the furnace wall is cooled by circulating water; a furnace bottom tray is arranged on the inner side of the bottom of the furnace body, and the furnace bottom tray is connected with a rod-shaped anode and a workpiece load-bearing tray, and a hollow target material and auxiliary tooling are arranged on the workpiece load-bearing tray, and the rod-shaped anode passes through the hollow target material, and the auxiliary tooling is used for heat preservation and support of the hollow target material, and a tubular workpiece is arranged on the outer side of the hollow target material and the inner side of the auxiliary tooling; a workpiece cathode and a target cathode are also arranged in the furnace body, and the workpiece cathode is connected to the workpiece load-bearing tray. The workpiece load-bearing tray is connected to the tubular workpiece, which is conductively connected to the tubular workpiece and is used to carry and position the workpiece to prevent the workpiece electrode rod from being deformed by excessive force. The target cathode is connected to the hollow target through a connecting guide rod; the workpiece cathode and power supply 2 and the furnace body form a circuit to generate glow discharge for activating and heating the surface of the tubular workpiece; the target cathode and power supply 1 and the furnace body form a circuit to generate glow discharge for sputtering target elements and depositing them on the workpiece surface; the target cathode and the workpiece cathode produce a double glow hollow cathode effect to accelerate the sputtering of elements and the process.

[0008] Furthermore, the hollow target is a cylindrical tube formed by evenly winding the wire target, and each circle is spot welded on the outside with the same material as the hollow target. The hollow cathode effect is used to accelerate the coating rate. The material can be any metal element and its alloy, especially high melting point metal has obvious advantages. The wire diameter can be changed to adapt to the diameter of the tubular workpiece.

[0009] Furthermore, ceramic connection holes and electron channel holes are arranged on the surface of the hollow target material. The diameter of the electron channel hole is 1 to 2 mm, so that the plasma can be discharged evenly and the uniformity of the film layer can be improved. The ceramic connection hole is used to pass through the ceramic connection rod and connect to the auxiliary tooling. The ceramic connection rod is made of insulating ceramic.

[0010] Furthermore, the wall thickness of the hollow target is 3-5 mm, and the outer wall thereof is 5-25 mm away from the inner wall of the tubular workpiece. The hollow target is made of metal or conductive ceramic.

[0011] In order to avoid tip discharge, the workpiece cathode, target cathode and hollow target are all cylindrical.

[0012] To prevent material contamination, the connecting guide rod is made of the same material as the hollow target.

[0013] Furthermore, the lower bottom of the workpiece load-bearing tray is supported by insulating ceramics and placed on the furnace bottom tray, and the furnace bottom tray shields the exhaust port to prevent pollution.

[0014] Furthermore, the rod-shaped anode has a diameter of 3 to 5 mm and is made of one or more of Ta, W and Mo. The rod-shaped anode is used to absorb electrons, so that the target material is discharged uniformly and the coating quality is improved.

[0015] The coating method of the coating device for the inner wall of the tube body comprises the following steps:

[0016] Step 1: Use sandpaper to grind the inner wall of the tubular workpiece to 1500 mesh, and then use ethanol with a concentration greater than 95% to wipe and clean the tubular workpiece, the hollow target, the workpiece load tray, the rod-shaped anode, and the furnace bottom tray, and dry them;

[0017] Step 2: Load the cleaned components into the furnace body in sequence;

[0018] Step 3: Turn on the mechanical pump, pump the furnace pressure to below 1Pa, fill it with argon to above 200Pa, pump it to below 1Pa again, repeatedly perform gas washing, and maintain the pressure between 20 and 80Pa by injecting argon;

[0019] Step 4, slowly increase the cathode voltage of the workpiece to 300-500V, and use plasma glow to clean and heat the tubular workpiece for 30-60 minutes;

[0020] Step 5: Open and slowly increase the target cathode voltage to 600-950V, and at the same time increase the workpiece cathode voltage to 450-700V, so that the working gas pressure is 20-80Pa, the distance between the hollow target and the inner wall of the tubular workpiece is 5-25mm, and the insulation time is 3-6h;

[0021] Step 6. After the insulation is completed, the voltage of the hollow target and the tubular workpiece is reduced to 0V. This process takes more than 30 minutes. Then, the target is evacuated to below 0.1Pa and the target is taken out after cooling in the furnace.

[0022] Working principle: This device uses the grounded furnace body as the anode, and places two negative potential electrodes in the furnace as two cathodes, namely the target cathode and the workpiece cathode. The workpiece cathode connecting pipe is used to activate and heat the surface of the tubular workpiece; the target cathode is connected to the sputtering target material to sputter the coating elements and deposit them on the workpiece surface. During operation, the target cathode potential is more negative than the workpiece cathode (that is, the target electrode voltage is higher), and the ionized argon ions sputter more elements on the target surface; at the same time, due to the special hollow target structure, the electrons accumulated on the surface will be transferred to the rod-shaped anode through the electron channel, so that the overall discharge is uniform, achieving the effect of high-quality uniform coating on the inner wall. The target cathode and the workpiece cathode glow at the same time to produce a hollow cathode effect, which accelerates the sputtering of elements and the process.

[0023] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0024] 1. When processing tubular workpieces, the coating can be designed with strong designability and a wide variety of elements to choose from, which can be any metal and its alloy or conductive ceramic. In particular, it has obvious advantages in the selection of high melting point metals and conductive ceramics, which can be combined arbitrarily;

[0025] 2. The hollow target material can accelerate the coating rate by utilizing the hollow cathode effect, and the electron channel and rod-shaped anode structure can make the plasma discharge more uniform and controllable;

[0026] 3. The inner wall coating of the tubular workpiece is uniform and controllable, has strong bonding with the tubular workpiece, is metallurgical bonding, has a gradient distribution of coating components, has low stress, and has a good protection effect;

[0027] 4. The preparation method is green and efficient, has no environmental pollution, saves resources, has simple equipment and process, is clean and efficient, and is suitable for industrial promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structure of the present invention;

[0029] Figure 2 It is a schematic structural diagram of the first hollow target material 9 of the present invention;

[0030] Figure 3 is a schematic structural diagram of a second hollow target material 9 of the present invention;

[0031] Figure 4 is a scanning electron microscope image of a sampling cross section of Example 1 of the present invention;

[0032] Figure 5 is an element distribution diagram of the sampling cross section of Example 1 of the present invention;

[0033] Figure 6 is a scanning electron microscope image of a sampling cross section of Example 2 of the present invention;

[0034] Figure 7 It is the element distribution diagram of the sampling cross section of Example 2 of the present invention. DETAILED DESCRIPTION

[0035] like Figure 1The furnace body 3 of the coating device on the inner wall of the tube body is a double-layer vacuum furnace and is grounded as a whole as an anode, and the furnace wall is cooled by circulating water. The opening method of the furnace body 3 is not limited, and it can be manufactured into any shape according to needs. A furnace bottom tray 7 is provided on the inner side of the bottom of the furnace body 3 to block the exhaust port to prevent pollution. The furnace bottom tray 7 is connected to the rod-shaped anode 8 and is connected to the workpiece load-bearing tray 6 by ceramic insulation, which plays the role of connecting the rod-shaped anode 8 and supporting the workpiece load-bearing tray 6. A hollow target material 9 and an auxiliary tooling 11 are arranged on the workpiece load-bearing tray 6. The hollow target material 9 passes through the rod-shaped anode 8. The auxiliary tooling 11 is used for heat preservation and support of the hollow target material 9. A tubular workpiece 10 is arranged on the outside of the hollow target material 9 and the inside of the auxiliary tooling 11. There are also workpiece cathodes 4 and target cathodes 5 in the furnace body 3. The tubular workpiece 10 is conductively connected to the workpiece cathode 4 and the workpiece load-bearing tray 6. A cylindrical shape is adopted to avoid tip discharge. The workpiece load-bearing tray 6 is conductively connected to the tubular workpiece 10, and the target cathode 5 is conductively connected to the hollow target 9 through the connecting guide rod 12. To prevent material contamination, the connecting guide rod 12 is made of the same material as the hollow target 9. The workpiece cathode, power supply 2, and furnace body 3 form a loop to generate glow discharge for activating and heating the surface of the tubular workpiece 10; the target cathode 5, power supply 1, and furnace body form another loop to generate glow discharge for sputtering target elements and depositing them on the workpiece surface; the target cathode 5 and the workpiece cathode 4 produce a double glow hollow cathode effect to accelerate element sputtering and process. The workpiece cathode 4, target cathode 5, and hollow target 9 are all cylindrical. The lower bottom of the workpiece load-bearing tray 6 is supported by insulating ceramics and placed on the furnace bottom tray 7. The rod-shaped anode 8 has a diameter of 3 to 5 mm and is made of one or more of Ta, W, and Mo.

[0036] The wall thickness of the hollow target 9 is 3 to 5 mm, and the outer wall thereof is 5 to 25 mm away from the inner wall of the tubular workpiece 10. The hollow target 9 is made of conductive metal or ceramic. The hollow target 9 can be selected from two structures. Figure 2 The surface of the first hollow target material 9 is provided with a ceramic connection hole 901 and an electron channel hole 902. The diameter of the electron channel hole 902 is 1-2 mm, and the upper and lower spacing is 10-15 mm. The ceramic connection hole 901 is used to pass through the ceramic connection rod and connect to the auxiliary tooling 11. Figure 3 The second hollow target material 9 is a cylindrical tube formed by evenly winding a filamentary target material, and each circle is spot welded on the outside with the same material as the hollow target material 9. Figure 2 Hollow target 9.

[0037] Example 1

[0038] A coating method of the coating device for the inner wall of the tube body comprises the following steps:

[0039] Step 1: Use sandpaper to grind the inner wall of the tubular workpiece to 1500 mesh, and then use 95% industrial ethanol to wipe and clean the pure copper pipe with an inner diameter of 40 mm (99.99%), the pure Ta hollow target 4 with an outer diameter of 20 mm and a wall thickness of 3 mm (99.95%), the stainless steel workpiece load tray 6, the 3 mm diameter pure Ta rod anode 8, the stainless steel furnace bottom tray 7 and other components, and dry them;

[0040] Step 2: Load the cleaned components into the furnace body 3 from bottom to top, including the stainless steel furnace bottom tray 7, the workpiece cathode 4, the target cathode 5, the pure copper tubular workpiece 10, the pure Ta hollow target 9, the auxiliary tooling 11, and the pure Ta rod anode 8;

[0041] Step 3: Turn on the mechanical pump, pump the gas pressure of the furnace body 3 to below 1Pa, perform a gas washing operation, fill with argon gas with a purity of 99.999% to 200Pa, and then pump it to below 1Pa, repeat this process twice, and maintain the pressure of the argon gas at 35Pa;

[0042] Step 4, slowly increase the voltage of the workpiece cathode 4 to 300V, and use plasma glow to clean and heat the tubular workpiece 10 for 30 minutes;

[0043] Step 5, open and slowly increase the target cathode 5 voltage to 850V, and at the same time increase the workpiece cathode 4 voltage to 600V, so that the working pressure is 35Pa, the distance between the hollow target 9 and the inner wall of the tubular workpiece 10 is 10mm, and the holding time is 3h;

[0044] Step 6: After the insulation is completed, the voltage of the hollow target 9 and the tubular workpiece 10 is reduced to 0V. This process takes 40 minutes. Then, the vacuum is evacuated to below 0.1 Pa and the workpiece is taken out after cooling in the furnace for 8 hours.

[0045] Performance Test:

[0046] like Figure 4 The cross section of the tubular workpiece 10 after coating in this embodiment was sampled and photographed by scanning electron microscope. The results showed that the coating was very uniform and dense, and there were no defects inside the coating and at the transition between the coating and the substrate. Figure 5 The effective coating thickness is 17μm, and the coating elements are distributed in a gradient manner, which effectively improves the bonding strength of the coating.

[0047] In a vacuum environment of 1000°C, the inner wall of the pipe was in contact with molten cerium metal, and the pure copper component was severely corroded after 3 hours, while the coated component obtained in Example 1 was still intact after 60 hours, and the metal corrosion resistance was improved by more than 20 times.

[0048] Example 2

[0049] A coating method of the coating device for the inner wall of the tube body comprises the following steps:

[0050] Step 1: Use sandpaper to grind the inner wall of the tubular workpiece to 1500 mesh, and then use 95% industrial ethanol to wipe and clean the alloy steel pipe with an inner diameter of 40 mm (PCrNi3MoVA), the pure Ta hollow target 4 (99.95%) with an outer diameter of 20 mm and a wall thickness of 3 mm, the stainless steel workpiece load-bearing tray 6, the 3 mm diameter pure Ta rod-shaped anode 8, the stainless steel furnace bottom tray 7 and other components, and dry them;

[0051] Step 2: Load the cleaned components into the furnace body 3 from bottom to top, including the stainless steel furnace bottom tray 7, the workpiece cathode 4, the target cathode 5, the pure copper tubular workpiece 10, the pure Ta hollow target 9, the auxiliary tooling 11, and the pure Ta rod anode 8;

[0052] Step 3, turn on the mechanical pump, pump the gas pressure of the furnace body 3 to below 1Pa, perform a gas washing operation, fill with 99.999% purity argon gas to 200Pa, and then pump it to below 1Pa, repeat twice, and maintain the argon gas at 40Pa;

[0053] Step 4, slowly increase the voltage of the workpiece cathode 4 to 300V, and use plasma glow to clean and heat the tubular workpiece 10 for 40 minutes;

[0054] Step 5: Open and slowly increase the voltage of the target cathode 5 to 900V, and at the same time increase the voltage of the workpiece cathode 4 to 650V, so that the working pressure is 40Pa, the distance between the hollow target 9 and the inner wall of the tubular workpiece 10 is 10mm, and the holding time is 3.5h;

[0055] Step 6: After the insulation is completed, the voltage of the hollow target 9 and the tubular workpiece 10 is reduced to 0V. This process takes 40 minutes. Then, the vacuum is evacuated to below 0.1 Pa and the furnace is cooled for 8 hours before being taken out.

[0056] Performance Testing:

[0057] like Figure 6 The cross section of the tubular workpiece 10 after coating in this embodiment was sampled and photographed by scanning electron microscope. The results showed that the coating was very uniform and dense, and there were no defects inside the coating and at the transition between the coating and the substrate. Figure 7 The overall effective thickness of the coating is nearly 20μm, and the coating elements are distributed in a gradient, which effectively improves the bonding strength of the coating.

[0058] The pipe samples were tested for oxidation performance at 650℃ for 40h. The results showed that the uncoated samples were severely oxidized and finally gained 3.52mg / cm 2 , while the weight gain of the sample of the coated pipe is 1.26mg / cm 2 , and it is still intact, and its antioxidant performance has been improved to more than 2.8 times.

Claims

1. A coating device for the inner wall of a tube, characterized in that: The invention comprises a furnace body (3), wherein the furnace body (3) is a double-layer vacuum furnace and serves as an anode, and the furnace wall is cooled by circulating water; a furnace bottom tray (7) is arranged on the inner side of the bottom of the furnace body (3), the furnace bottom tray (7) is connected to a rod-shaped anode (8) and a workpiece load-bearing tray (6), a hollow target material (9) and an auxiliary tooling (11) are arranged on the workpiece load-bearing tray (6), the hollow target material (9) passes through the rod-shaped anode (8), the auxiliary tooling (11) is used for heat preservation and support of the hollow target material (9), and a tubular workpiece (10) is arranged on the outer side of the hollow target material (9) and the inner side of the auxiliary tooling (11); the furnace body (3) is also provided with a workpiece cathode (4) and a target cathode (5), the workpiece cathode (4) being connected to a workpiece load-bearing tray (6), the workpiece load-bearing tray (6) being conductively connected to the tubular workpiece (10), and the target cathode (5) being connected to the hollow target (9) via a connecting guide rod (12); the workpiece cathode (4) and the second power source (2) and the furnace body (3) forming a circuit to generate a glow discharge for activating and heating the surface of the tubular workpiece (10); the target cathode (5) and the first power source (1) and the furnace body (3) forming a circuit to generate a glow discharge for sputtering target elements and depositing them on the workpiece surface; A ceramic connection hole (901) and an electron channel hole (902) are provided on the surface of the hollow target material (9); the diameter of the electron channel hole (902) is 1 to 2 mm, and the upper and lower spacing is 10 to 15 mm; the ceramic connection hole (901) is used to pass through a ceramic connection rod and is connected to an auxiliary tooling (11); The target cathode (5) and the workpiece cathode (4) glow simultaneously to produce a hollow cathode effect.

2. The coating device for the inner wall of a tube according to claim 1, characterized in that: The hollow target material (9) is a cylindrical tube formed by evenly winding a filamentary target material, and each turn is spot-welded on the outside with the same material as the hollow target material (9).

3. The coating device for the inner wall of a tube according to claim 1, characterized in that: The wall thickness of the hollow target material (9) is 3 to 5 mm, and the outer wall thereof is 5 to 25 mm away from the inner wall of the tubular workpiece (10).

4. The coating device for the inner wall of a tube according to claim 1, characterized in that: The hollow target material (9) is made of metal or conductive ceramic.

5. The coating device for the inner wall of a tube according to claim 1, characterized in that: The workpiece cathode (4), the target cathode (5), and the hollow target (9) are all cylindrical.

6. The coating device for the inner wall of a tube according to claim 1, characterized in that: The connecting guide rod (12) is made of the same material as the hollow target material (9).

7. The coating device for the inner wall of a tube according to claim 1, characterized in that: The lower bottom of the workpiece load-bearing tray (6) is supported by insulating ceramics and is placed on the furnace bottom tray (7).

8. The coating device for the inner wall of a tube according to claim 1, characterized in that: The rod-shaped anode (8) has a diameter of 3-5 mm and is made of one or more of Ta, W and Mo.

9. A coating method for a coating device for the inner wall of a tube according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: grind the inner wall of the tubular workpiece (10) to a mesh size of 1500 or more with sandpaper, and then wipe and clean the tubular workpiece (10), the hollow target material (9), the workpiece load-bearing tray (6), the rod-shaped anode (8), and the furnace bottom tray (7) with ethanol having a concentration greater than 95%, and then dry them; Step 2: Place the cleaned components into the furnace body (3) in sequence; Step 3, turn on the mechanical pump, pump the furnace body (3) to below 1Pa, then fill it with argon gas to above 200Pa, then pump it to below 1Pa, repeatedly perform gas washing, and maintain the pressure of the furnace body (3) between 20 and 80Pa by injecting argon gas; Step 4, slowly increasing the voltage of the workpiece cathode (4) to 300-500V, and using plasma glow to clean and heat the tubular workpiece (10) for 30-60 minutes; Step 5, opening and slowly increasing the target cathode (5) voltage to 600-950V, and at the same time increasing the workpiece cathode (4) voltage to 450-700V, so that the working gas pressure is 20-80Pa, the distance between the hollow target (9) and the inner wall of the tubular workpiece (10) is 5-25mm, and the heat preservation time is 3-6h; Step 6: After the heat preservation is completed, the voltage of the hollow target (9) and the tubular workpiece (10) is reduced to 0V. This process takes more than 30 minutes. Then, the vacuum is evacuated to below 0.1 Pa and the workpiece is taken out of the furnace after cooling.

Images