A method for depositing DLC by direct current magnetron hollow cathode plasma

Abstract

The application discloses a hollow tube DLC coating method by using a direct current magnetic control strong stretching arc, belongs to the technical field of surface coating, and aims at the problems of poor film uniformity, low adhesion, slow deposition rate and the like in the deposition of a DLC film on the inner wall of a hollow tube in the prior art. A low-pressure environment is established by using a vacuum cavity and a vacuum pump system, and a gas supply system is used to control a deposition atmosphere. A strong stretching arc source with a plurality of magnetic field coils is used to deposit a high-density DLC film on the inner wall of the hollow tube, so that the uniformity and adhesion of the DLC film are improved. Meanwhile, a bias voltage is applied to the hollow tube to enhance the adsorption capacity of carbon plasma on the surface of the substrate, improve the ion bombardment effect, make the DLC structure more dense, and significantly improve the adhesion between the coating and the substrate. The application is especially suitable for the inner wall area which is difficult to be coated. The application can effectively improve the uniformity, adhesion and deposition rate of the DLC coating, and is suitable for surface modification of hollow tube parts with high wear resistance and low friction requirement.

Description

Technical Field

[0001] This invention relates to the fields of surface coating technology and vacuum thin film deposition technology, and specifically to a DC magnetron high stretch arc deposition method for depositing diamond-like carbon (DLC) thin films on the inner wall of hollow tubes. Technical Background

[0002] Diamond-like carbon (DLC) films are thin-film materials composed of carbon elements, possessing excellent properties such as diamond-like hardness, low coefficient of friction, wear resistance, and corrosion resistance. Due to their unique physical and chemical properties, DLC films are widely used in various industrial fields, especially in machinery, electronics, and automotive, as friction surfaces, tool surface protection, wear-resistant coatings, and optical windows. However, despite these outstanding properties, the fabrication process of DLC films still faces many technical challenges, particularly in terms of film adhesion, uniformity, and hardness. Currently, the deposition methods for DLC coatings mainly include magnetron sputtering, plasma-enhanced chemical vapor deposition, radio frequency plasma deposition, hot-wire chemical vapor deposition, and DC arc deposition. These methods have mature applications in planar or external surface coatings, but depositing high-quality, uniform, and dense DLC films on hollow tube workpieces with complex morphologies and narrow internal cavities still faces many challenges. On the one hand, because the inner cavity of a hollow tube is a closed structure, uneven plasma density distribution and insufficient ion energy often lead to problems such as coating discontinuity, poor adhesion, and localized peeling. On the other hand, thermal field control during deposition is challenging, and temperature gradients can easily cause stress concentration within the coating, leading to film cracking or delamination. Furthermore, traditional equipment lacks effective internal temperature control mechanisms and bias regulation methods when depositing hollow structures, making it impossible to precisely control film growth kinetics and further limiting its application in micro-hollow structures. Therefore, there is an urgent need for a novel DLC deposition method that can balance internal plasma distribution, temperature control, and enhanced ion bombardment, particularly suitable for the inner wall surfaces of high aspect ratio hollow tubes, to improve coating density, adhesion, and overall uniformity, thereby meeting the high-performance surface functionalization requirements of precision structural components.

[0003] Advantages of using a DC magnetron-controlled high-stretch arc for DLC deposition on hollow tubes: This method employs a high-stretch arc to bombard the substrate surface with high-energy ions, effectively enhancing the adhesion between the film and the substrate, thereby improving film adhesion and preventing film detachment or peeling. The arc discharge provides high-energy ion bombardment, which facilitates rapid nucleation and densification of the film, thus improving its hardness, wear resistance, and corrosion resistance. Compared to traditional methods, DLC films have a more compact structure, making them more suitable for applications under high loads and high temperatures, especially for substrates with complex or fine structures. It can deposit thicker DLC films in a shorter time, improving production efficiency and reducing production costs. Applying a bias voltage to the deposited hollow tube workpiece increases the active sites on the substrate surface, promoting adhesion between the film and the substrate, resulting in stronger DLC film adhesion and preventing film detachment or peeling. Furthermore, the semi-circular temperature control system, covering the outer wall of the hollow tube and combined with thermocouple feedback control, stabilizes the substrate temperature, ensures uniform heating of the inner wall, reduces thermal stress, and improves coating uniformity and adhesion. Simultaneously, during the annealing cooling stage, the system precisely controls the low cooling rate, preventing cracks or residual stress in the film due to sudden temperature drops. In summary, this technology not only improves film performance but also enhances deposition quality, making it particularly suitable for substrates with complex shapes and applications requiring high film performance.

[0004] Therefore, the method of coating DLC ​​using DC magnetron-controlled high-stretch arc hollow tubes can not only improve the quality of the film and solve the problems of poor film adhesion, insufficient hardness, uneven coating and low deposition rate in traditional methods, but also has high process stability and repeatability while meeting high performance requirements, making it suitable for large-scale industrial production applications. Summary of the Invention

[0005] This invention provides a method for depositing DLC ​​coatings on the inner wall of hollow tubes using a DC magnetized high-stretch arc. This method optimizes the deposition temperature by setting a semi-circular temperature control system on the outer wall of the hollow tube and applying a bias voltage to the hollow tube to enhance ion bombardment, thus achieving the preparation of high-quality DLC coatings. This method can improve the adhesion, density, and uniformity of the DLC film, and is particularly suitable for high-performance wear-resistant and corrosion-resistant coating applications on cylindrical inner wall structures. Its key features include a self-designed DC magnetized high-stretch arc hollow tube DLC coating equipment: 1. Stable control of the DC magnetized high-stretch arc. An optimized magnetized control system ensures uniform distribution of the arc plasma and effective entry into the hollow tube, avoiding the coating unevenness problems caused by traditional methods. 2. Precise regulation of the double semi-circular temperature control system on the outer wall of the hollow tube. The temperature of the hollow tube is precisely controlled by two semi-circular temperature control systems to ensure uniform substrate temperature during DLC ​​deposition, preventing local overheating or undercooling, thereby optimizing film density and reducing stress. 3. A bias voltage control system on the outer wall of the hollow tube. Applying an appropriate bias voltage to the hollow cylinder enhances the bombardment effect of the carbon plasma, improves the adhesion of the DLC film, and enables it to form a stronger bond with the substrate. Specifically, this includes the following steps:

[0006] Step 1: Matrix Selection

[0007] DLC coating is suitable for a variety of metals and alloys, with common substrates including stainless steel, titanium alloys, aluminum alloys, and cemented carbide. DLC can improve surface hardness and wear resistance. The substrate should have a certain degree of conductivity to optimize the ion bombardment process under bias voltage. Furthermore, a hollow tubular shape is required.

[0008] Step 2: Substrate surface pretreatment:

[0009] For rough substrates or substrates with surface defects, mechanical treatment is recommended to improve coating adhesion and uniformity.

[0010] 1.1 First, the substrate surface is sandblasted to remove surface oil, oxide layer and base metal.

[0011] 1.2 The pretreated substrate was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water to remove surface impurities until no watermarks remained after drying.

[0012] 1.3 Place the workpiece in the center of the chamber of the DC magnetron high-strength arc device, and turn on the vacuum pump to pre-evacuate to 10. - 2The process involves removing air and contaminants from the cavity. Argon and hydrogen are introduced, maintaining a pressure of 500-1000 Pa. The power supply is activated at 300-500 V. An electric arc is formed between the anode and cathode, breaking down the gas to create plasma. The hollow cylinder is grounded to create a bias voltage, and plasma cleaning is performed for 10-30 minutes. Ar ion bombardment [plasma cleaning] aims to remove residual oxides from the surface and improve adhesion.

[0013] Step 3: DLC coating deposition

[0014] After plasma cleaning, the power supply voltage is reduced to 100-200V, and the semi-circular temperature control system is activated to maintain the sample temperature between 100-500℃, ensuring uniform temperature on both the inner and outer walls and reducing internal stress in the film. The bias power supply is then turned on, applying a 30-100V bias voltage to the hollow cylinder via an external power source. This enhances the adsorption capacity of carbon plasma onto the substrate, improves the ion bombardment effect, makes the DLC film denser, and strengthens its adhesion to the substrate. Acetylene is then introduced into the chamber to adjust the chamber pressure. This allows a diamond-like carbon film to form on the inner wall of the hollow cylinder.

[0015] Step 4: Annealing and Cooling

[0016] The current is gradually reduced to prevent coating cracking caused by sudden temperature changes. Gas flow is shut off to maintain a vacuum environment and reduce oxidation contamination. The temperature control system gradually lowers the temperature to avoid rapid cooling that could increase internal stress. Because this method uses a semi-circular temperature control system, the substrate temperature can be precisely adjusted to ensure a uniform temperature drop on the inner wall during annealing, thereby reducing stress caused by temperature gradients. The temperature control system remains operational during the cooling phase to control the cooling rate. Feedback control (such as thermocouple monitoring) ensures a uniform temperature decrease. This method is particularly suitable for long hollow tubes because the temperature gradient between the ends and the middle of a long tube is large, easily leading to localized thermal stress.

[0017] This method successfully deposits a DLC coating on the inner wall of hollow tubes. It optimizes temperature uniformity through a semi-circular temperature control system, enhances ion bombardment intensity through bias voltage regulation, and combines this with a DC magnetron-controlled high-stretch arc to achieve high uniformity, strong adhesion, and low internal stress in the DLC film. This method successfully solves the problems of poor deposition uniformity, low adhesion, and easy cracking of coatings on the inner wall of hollow tubes, providing a new technical solution for high-end manufacturing.

[0018] The technical solution of this invention is:

[0019] This invention provides a method for depositing DLC ​​coatings on hollow tubes based on a DC magnetized high-stretching arc. This method optimizes the deposition temperature by incorporating a semi-circular temperature control system on the outer wall of the hollow tube and applies a bias voltage to the hollow tube to enhance ion bombardment, thereby improving the coating's uniformity, adhesion, and wear resistance. The technical solution mainly includes the following steps:

[0020] 1. Equipment Structure

[0021] The equipment used in this method includes the following key components:

[0022] 1) Optimized design of DC magnetically controlled high-extension arc

[0023] This invention enhances the arc plasma density and improves the deposition rate by employing an external electrode structure to generate a strong, extended arc outside the hollow cylinder. A magnetic field is used to optimize the arc morphology, allowing high-energy carbon plasma to uniformly enter the hollow cylinder's inner cavity and form a high-quality DLC coating on the inner wall surface. Traditional arc deposition methods often suffer from uneven coating on the inner wall of the hollow tube; however, this invention, through magnetic control design, maintains arc stability over a longer distance, improving deposition uniformity. The interaction between the arc and the substrate is optimized by using a temperature control system to adjust the temperature, ensuring the substrate surface is optimal for DLC deposition. Simultaneously, bias control enhances ion bombardment, ensuring strong coating adhesion. An optimized gas mixing ratio (e.g., H2 / CH4) is used to adjust plasma activity, improving the physicochemical properties of the DLC film.

[0024] 2) Double semi-circular temperature control system on the outer wall of the hollow cylinder

[0025] Precise temperature control improves deposition quality. Two semi-circular temperature control systems are arranged on the outer wall of the hollow cylinder to precisely control the temperature of the workpiece during the deposition process, avoiding stress concentration or film quality degradation caused by overheating or uneven local temperature distribution. This temperature control system can dynamically adjust the temperature according to the needs of different stages in the DLC deposition process, ensuring the optimal performance of the DLC film. 3 / sp 2 A reasonable ratio improves the mechanical properties of the film. Optimized DLC coating stress prevents cracking. Precise temperature control of the hollow cylinder surface temperature allows for gradual stress release during DLC ​​film deposition, avoiding cracking or peeling caused by high-temperature gradients. Low-stress DLC films improve wear resistance and service life, making them suitable for high-load conditions.

[0026] 3) Applying a bias voltage to the hollow cylinder enhances ion bombardment.

[0027] Optimizing DLC ​​deposition kinetics enhances film adhesion. Applying a suitable bias voltage to the hollow cylinder via an external power source strengthens the adsorption capacity of carbon plasma onto the substrate, improves the ion bombardment effect, resulting in a denser DLC film and stronger adhesion to the substrate. Proper bias voltage control accelerates the nucleation process of DLC, improves film uniformity, reduces porosity, and enhances wear and corrosion resistance. Bias voltage also modulates the film structure and improves mechanical properties; appropriate bias voltage can optimize the spp of the DLC film. 3 / sp 2The increased carbon bond ratio improves film hardness and reduces residual stress, resulting in superior wear resistance. Excessive bias voltage may enhance sputtering effects, negatively impacting film quality. Therefore, this invention experimentally optimizes bias voltage parameters to enhance adhesion while preventing film damage.

[0028] 2. Specific sedimentation steps

[0029] Step 1: Matrix Selection

[0030] DLC coating is suitable for a variety of metals and alloys, with common substrates including stainless steel, titanium alloys, aluminum alloys, and cemented carbide. DLC can improve surface hardness and wear resistance. The substrate should have a certain degree of conductivity to optimize the ion bombardment process under bias voltage. Furthermore, a hollow tubular shape is required.

[0031] Step 2: Substrate surface pretreatment:

[0032] For rough substrates or substrates with surface defects, mechanical treatment is recommended to improve coating adhesion and uniformity.

[0033] 1.1 First, the substrate surface is sandblasted to remove surface oil, oxide layer and base metal.

[0034] 1.2 The pretreated substrate was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water to remove surface impurities until no watermarks remained after drying.

[0035] 1.3 Place the workpiece in the center of the chamber of the DC magnetron high-strength arc device, and turn on the vacuum pump to pre-evacuate to 10. - 2 The process involves removing air and contaminants from the cavity. Argon and hydrogen are introduced, maintaining a pressure of 500-1000 Pa. The power supply is activated at 300-500 V. An electric arc is formed between the anode and cathode, breaking down the gas to create plasma. The hollow cylinder is grounded to create a bias voltage, and plasma cleaning is performed for 10-30 minutes. Ar ion bombardment [plasma cleaning] aims to remove residual oxides from the surface and improve adhesion.

[0036] Step 3: DLC coating deposition

[0037] After plasma cleaning, reduce the power supply voltage to 100-200V and activate the semi-circular temperature control system to maintain the sample temperature between 100-500℃, ensuring uniform temperature on both the inner and outer walls and reducing internal stress in the film. Connect the hollow cylinder to the bias power supply side and turn on the bias power supply. Apply a 30-100V bias voltage to the hollow cylinder through an external power supply to enhance the adsorption capacity of carbon plasma onto the substrate, improve the ion bombardment effect, make the DLC film denser, and enhance its adhesion to the substrate. Subsequently, acetylene is introduced into the chamber to adjust the chamber pressure. This allows a diamond-like carbon film to form on the inner wall of the hollow cylinder.

[0038] Step 4: Annealing and Cooling

[0039] The current is gradually reduced to prevent coating cracking caused by sudden temperature changes. Gas flow is shut off to maintain a vacuum environment and reduce oxidation contamination. The temperature control system gradually lowers the temperature to avoid rapid cooling that could increase internal stress. Because this method uses a semi-circular temperature control system, the substrate temperature can be precisely adjusted to ensure a uniform temperature drop on the inner wall during annealing, thereby reducing stress caused by temperature gradients. The temperature control system remains operational during the cooling phase to control the cooling rate. Feedback control (such as thermocouple monitoring) ensures a uniform temperature decrease. This method is particularly suitable for long hollow tubes because the temperature gradient between the ends and the middle of a long tube is large, easily leading to localized thermal stress.

[0040] 3. Technological advantages

[0041] The temperature control system optimizes temperature uniformity, reduces thermal stress, and improves DLC film quality. Bias voltage enhances adhesion, improves film durability, and reduces peeling. Magnetic field optimization and rotating electrodes achieve ultra-uniform DLC film deposition, suitable for hollow tubes. This method is applicable to precision manufacturing (medical, aerospace, etc.), broadening the application fields of DLC. Compared to existing DLC ​​deposition technologies, this method optimizes temperature control and ion bombardment mechanisms, effectively improving the quality, uniformity, and durability of the coating on the inner wall of hollow tubes, meeting the needs of high-end industrial applications.

[0042] The key to the implementation of this invention lies in:

[0043] The key to implementing this invention lies in precisely controlling the temperature, optimizing the distribution of the electric arc plasma, and rationally adjusting the workpiece bias voltage to ensure that the DLC film layer is uniformly deposited on the inner wall of the hollow cylinder, with high adhesion and low stress. Specifically, it includes the following core points:

[0044] 1. Stable control of DC magnetron-controlled strong-extension arc. An optimized magnetron system ensures uniform arc plasma distribution and effective penetration into the hollow cylinder, avoiding the uneven coating problems associated with traditional methods. By rationally adjusting the arc current, magnetic field strength, and working gas flow rate, the deposition rate and quality of the DLC film are optimized.

[0045] 2. Precise temperature control via a double semi-circular temperature control system on the outer wall of the hollow cylinder. Two semi-circular temperature control systems precisely regulate the temperature of the hollow cylinder, ensuring uniform substrate temperature during DLC ​​deposition and preventing localized overheating or undercooling, thereby optimizing film density and reducing stress. The temperature control system can dynamically adjust the temperature to ensure uniform spline temperature of the DLC film. 3 / sp 2 The proportions are reasonable, which improves hardness and wear resistance, while reducing residual stress and preventing the film from cracking or peeling.

[0046] 3. Proper setting of bias voltage for the workpiece [hollow cylinder]. Applying an appropriate bias voltage enhances the bombardment effect of carbon plasma, improves the adhesion of the DLC film, and enables it to form a stronger bond with the substrate. By adjusting the bias voltage, the microstructure of the DLC film is optimized, film uniformity is enhanced, and film defects caused by excessive sputtering are prevented.

[0047] 4. Optimize deposition process parameters to ensure uniform DLC film coverage. Combine temperature control and bias control to form a uniform and highly dense DLC coating on the inner wall of the hollow cylinder, avoiding localized areas of excessive thickness or thinness, thus improving overall wear resistance and service life. Employing appropriate workpiece rotation or axial scanning methods further enhances the uniformity of the DLC film, making it suitable for hollow cylinder parts of various shapes.

[0048] The key to implementing this invention lies in the comprehensive regulation of temperature control, bias voltage, and optimized arc plasma deposition to ensure stable, uniform, and high-quality deposition of DLC film on the inner wall of the hollow cylinder, providing an efficient and reliable method for the industrial application of high-performance wear-resistant coatings.

[0049] The advantages of this invention compared to the prior art are as follows:

[0050] This invention offers significant advantages over existing technologies, primarily in improving the uniformity, adhesion, and deposition rate of DLC coatings, while also optimizing the coating's mechanical properties and durability. By arranging a double semi-circular temperature control system on the outer wall of the hollow cylinder, the substrate temperature during the deposition process can be precisely controlled, avoiding localized overheating or undercooling, thereby optimizing the spline properties of the DLC film. 3 / sp 2The proportions are improved to enhance hardness, wear resistance, and crack resistance, while reducing residual stress in the coating, making it more stable and reliable. Furthermore, applying an appropriate bias voltage to the hollow cylinder enhances the bombardment effect of carbon plasma, improving the density and adhesion of the DLC film, ensuring uniform coating coverage of the entire inner wall, and preventing film peeling or cracking. Simultaneously, an optimized DC magnetron-controlled high-stretch arc technology is employed, enabling high-density carbon plasma to stably penetrate the hollow cylinder, effectively overcoming the uneven coating problem of traditional arc deposition methods, increasing the deposition rate, and allowing the DLC coating to form a high-quality, uniform coverage in a short time. Compared to traditional CVD and PVD methods, this invention can form a dense and uniform DLC film on the inner wall of a hollow cylinder, making it more widely applicable in precision machinery, automotive parts, aerospace, and medical devices, breaking through the limitations of existing technologies in coating complex structures. In summary, this invention, through the synergistic effect of temperature control, bias voltage regulation, and optimized arc plasma technology, enables DLC coatings to possess higher quality, superior mechanical properties, and wider applicability, providing an efficient and reliable technical solution for the industrial production of high-performance wear-resistant coatings. This invention, through the innovative combination of a dual semi-circular temperature control system, bias optimization, and DC magnetically controlled strong extension arc technology, enables DLC coatings to achieve higher uniformity, stronger adhesion, lower stress, and faster deposition rates on the inner wall of hollow cylinders. This effectively overcomes the shortcomings of existing technologies and improves the performance and industrial application value of DLC coatings. Attached Figure Description

[0051] Figure 1 It is a DC magneto-controlled high-stretch arc deposition device;

[0052] The components include: anode 1, cathode 2, bias voltage control system 3, semi-circular temperature control system 4, hollow cylinder 5, magnetic field coils 6, 7 and 8, DC power supply 9, vacuum pump system 10, vacuum chamber 11, and DC extended arc 12.

[0053] Figure 2 This is a schematic diagram of the semi-circular temperature control system in this device. Detailed Implementation

[0054] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0055] Example 1: Depositing a DLC film layer on the inner wall of a hollow metal cylinder

[0056] In this embodiment, a high-quality DLC film layer is deposited on the inner wall of a metal hollow cylinder (such as stainless steel or titanium alloy) using the DC magnetron high-stretch arc deposition method of the present invention.

[0057] 1. Experimental setup

[0058] like Figure 1 As shown, the experimental setup mainly includes an anode 1, a cathode 2, a bias voltage control system 3, a semi-circular temperature control system 4, a hollow cylinder 5, magnetic field coils 6, 7, and 8, a DC power supply 9, a vacuum pump system 10, a vacuum chamber 11, and a DC extended arc 12. The DC magnetized extended arc 12 generates high-density carbon plasma, which is compressed inside the hollow cylinder by the multi-stage magnetic field coils 6, 7, and 8, achieving deposition on the inner wall. The bias voltage system 3 applies a bias voltage to the hollow cylinder to enhance plasma bombardment and improve coating quality. The semi-circular temperature control system 4 precisely controls the temperature of the hollow cylinder, ensuring uniform substrate temperature during DLC ​​deposition and preventing localized overheating or undercooling, thereby optimizing film density and reducing stress.

[0059] 2. Coating process flow

[0060] This method is applicable to conductive substrates such as stainless steel, titanium alloys, aluminum alloys, and hard alloys. First, the substrate is sandblasted to remove the oxide layer and increase surface roughness to enhance adhesion. Then, ultrasonic cleaning is performed using acetone, anhydrous ethanol, and deionized water to ensure no residual impurities remain. After cleaning, the substrate is placed in the chamber of a DC magnetron-controlled high-intensity extension arc device and pre-evacuated to 10°C. -2 The process begins with plasma cleaning at 10-30 minutes. Argon and hydrogen are introduced, maintaining a pressure of 500-1000 Pa. A DC voltage of 300-500 V is applied, and the hollow cylinder is grounded to create a bias voltage. This removes residual oxides, optimizes surface activity, and improves DLC adhesion. After plasma cleaning, a semi-circular temperature control system is activated to stabilize the substrate temperature at 100-500℃, ensuring uniform heating of the inner and outer walls and reducing stress caused by temperature gradients. Simultaneously, the DC power supply voltage is maintained at 100-200 V, and a 30-100 V bias voltage is applied to the hollow cylinder to enhance the adsorption capacity of carbon plasma onto the substrate, improve the ion bombardment effect, and make the deposited film denser and more cohesive. Subsequently, acetylene (C2H2) is introduced, and the chamber pressure is controlled. Under the action of plasma, carbon atoms form a DLC film on the inner wall of the hollow tube. By optimizing the gas flow rate, plasma power, and deposition time, uniform film thickness is ensured, while also achieving low friction, high hardness, and good wear resistance. After deposition, the current is gradually reduced to prevent rapid temperature drops that could cause film cracking. Gas flow is shut off to maintain a vacuum environment and reduce oxidation contamination. A temperature control system is used to gradually lower the temperature at a low rate, avoiding high residual stress caused by rapid cooling. The temperature control system operates continuously and is combined with thermocouple feedback regulation to ensure a uniform temperature decrease, which is particularly suitable for long hollow tubes and avoids localized thermal stress caused by temperature differences between the ends and the middle. After the temperature drops below 100°C, argon gas is slowly introduced to atmospheric pressure, and finally, the material is allowed to cool naturally to room temperature to stabilize the DLC structure and improve coating durability and adhesion.

[0061] Technical Advantages Summary: This invention employs a dual semi-circular temperature control system, substrate bias regulation, and a DC magnetron-controlled high-stretch arc plasma deposition method to achieve uniform deposition of high-quality DLC films on the inner walls of metal and ceramic hollow cylinders. Compared to traditional methods, this invention has significant advantages in the following aspects:

[0062] 1) Precise temperature control reduces thermal stress and improves film quality;

[0063] 2) Bias voltage enhances ion bombardment, improving the bonding strength and density of DLC;

[0064] 3) Optimized distribution of magnetron arc plasma ensures uniform coating deposition, suitable for workpieces with complex structures;

[0065] 4) It is applicable to hollow cylindrical materials, thus broadening the application range of DLC coating.

[0066] In summary, the technical solution of this invention, through optimization of temperature control, bias voltage, and plasma deposition methods, has achieved the industrial feasibility of preparing high-performance DLC coatings on the inner wall of hollow cylinders, and has broad application prospects.

Claims

1. A method for DLC plating of a DC magnetron-controlled high-stretch arc hollow tube, characterized in that: This device employs a self-designed DC magnetically controlled high-stretch arc device, comprising an anode, cathode, power supply, vacuum chamber, vacuum pump system, high-stretch DC arc, multiple magnetic field coils, a semi-circular temperature control system, and a bias power supply. Compared to existing technologies, the core innovations lie in the semi-circular temperature control system and the application of bias voltage to the hollow tube. The semi-circular temperature control system covers the outer wall of the hollow tube and, combined with thermocouple feedback control, stabilizes the substrate temperature, ensuring uniform heating of the inner wall, reducing thermal stress, and improving coating uniformity and adhesion. Simultaneously, during the annealing cooling stage, the system can precisely control the cooling rate, preventing cracks or residual stress in the film layer due to sudden temperature drops. Applying bias voltage to the hollow tube enhances the adsorption capacity of carbon plasma on the substrate surface, improves the ion bombardment effect, makes the DLC structure denser, and significantly improves the adhesion between the coating and the substrate. It is particularly suitable for difficult-to-coat inner wall areas, improving coating uniformity and stability. It is applicable to hollow tubes of different materials, especially for difficult-to-coat inner wall areas, improving coating uniformity and stability. The operating steps are as follows: 1) Substrate preparation: Select a conductive metal hollow tube as the substrate, sandblast it to remove the oxide layer, and then ultrasonically clean it in sequence with acetone, anhydrous ethanol and deionized water. After drying, place it in the deposition equipment chamber. 2) Plasma cleaning: Pre-evacuate to 10 -2 Pa, argon and hydrogen are introduced, the cavity pressure is controlled at 500-1000Pa, a DC voltage of 300-500V is applied, an electric arc is formed between the anode and cathode to break down the gas and form plasma, the hollow cylinder is grounded to form a bias voltage, plasma cleaning is performed to remove residual oxides on the surface and improve the bonding force. 3) DLC film deposition: The semi-circular temperature control system is activated to stabilize the substrate temperature at 100-500℃, ensuring uniform heating of the inner and outer walls and reducing thermal stress; a bias voltage of 30-100V is applied to the hollow tube to enhance the adsorption capacity of carbon plasma to the substrate surface, improve the ion bombardment effect, and make the DLC film denser; acetylene [C2H2] is introduced to control the chamber pressure, so that the DLC film is uniformly deposited on the inner wall of the hollow tube. 4) Annealing and cooling: Gradually reduce the current, shut off the gas flow, maintain a vacuum environment, and use a semi-circular temperature control system to cool down at a low rate to reduce the internal stress of the film. Finally, slowly fill with nitrogen or argon to atmospheric pressure and allow it to cool naturally to room temperature to improve the durability of the coating.

2. The method for DLC plating of a DC magnetron-controlled high-stretch arc hollow tube according to claim 1, characterized in that: The semi-circular temperature control system includes a thermocouple feedback control module, which keeps the temperature of different parts of the hollow tube uniform during the deposition process, and is particularly suitable for coating deposition on long hollow tubes.

3. The method for DLC plating of a DC magnetron-controlled high-strength arc hollow tube according to claim 1, characterized in that: The aforementioned DC magnetically controlled high-stretching electric arc utilizes multi-stage magnetic field coils to confine the elongated arc inside the hollow tube, making it particularly suitable for long hollow tubes.

4. The method for DLC plating of a DC magnetron-controlled high-stretch arc hollow tube according to claim 1, characterized in that: The bias voltage applied to the hollow cylinder is in the range of 30-100V. By optimizing the voltage to regulate the plasma energy, the density and adhesion of the DLC structure are improved.

5. The method for DLC plating of a DC magnetron-controlled high-stretch arc hollow tube according to claim 1, characterized in that: A semi-circular temperature control system is used during the cooling process to precisely adjust the base temperature and ensure that the inner wall temperature drops uniformly during annealing, thereby reducing the stress caused by the temperature gradient.

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