A method for preparing gradient multi-level multi-layer carbon film on the surface of fluoroether rubber by Cr / Ti co-doping

Abstract

The application discloses a method for preparing gradient multistage multilayer carbon film on the surface of fluoroether rubber by Cr / Ti co-doping, wherein the substrate is washed, dried, and then placed into a magnetron sputtering cavity; Ar gas is introduced to clean the substrate under high vacuum condition; and then modified metal micro-doped carbon film is obtained by adopting cathode arc magnetic filtering technology. The obtained co-doped carbon film obviously improves the friction performance, the hydrogenated amorphous carbon film composition in the film is increased, and meanwhile, the film itself density and hardness are maintained; the cathode arc magnetic filtering technology makes the doping elements uniformly disperse in the film, so that the film performance is improved by a small amount of doping elements; the order degree of the friction interface of the film is obviously improved during the friction process, the film has low friction coefficient and low wear rate, and the tribological performance of the film is improved.

Description

Technical Field

[0001] This invention relates to the fields of vacuum coating and thin film lubrication technology, and in particular to a method for preparing gradient multi-level multilayer carbon thin films on the surface of fluoroether rubber using Cr / Ti co-doping. Background Technology

[0002] Fluoropolymer elastomer (FKM) is widely used as a sealing material in aerospace, automotive, and chemical industries due to its excellent chemical stability, superior oil resistance, and good sealing performance. However, when FKM slides relative to engineering materials such as ceramics and steel, it often experiences high coefficients of friction and severe wear. This problem limits its service life and reliability in high-performance applications. Existing modification methods typically involve the deposition of surface coatings or thin films, but these methods still have some technical drawbacks. For example, traditional thin film deposition techniques may result in insufficient film adhesion, uneven thickness, or unstable performance, thus affecting the tribological properties and wear resistance of FKM.

[0003] To overcome these shortcomings, this invention proposes an innovative technical solution: preparing a carbon film on the surface of fluoropolymer rubber using cathodic arc magnetic filtration technology. This method effectively improves the film's adhesion, ensures its uniformity and stability, thereby significantly enhancing the wear resistance of fluoropolymer rubber and reducing its coefficient of friction. In this way, this invention not only overcomes the limitations of traditional film preparation techniques but also provides a more reliable technical guarantee for the high-performance application of fluoropolymer rubber. Summary of the Invention

[0004] To address the problems existing in the above-mentioned background technology, the present invention discloses a method for preparing gradient multi-level multilayer carbon thin films on the surface of fluoroether rubber by using Cr / Ti co-doping.

[0005] I. Preparation of Cr / Ti co-doped carbon thin films

[0006] The Cr / Ti co-doped carbon thin film of the present invention includes the following steps:

[0007] 1) Clean the substrate with alcohol using ultrasonic cleaning for 10-20 minutes to remove surface contaminants, blow it dry, and then place it on the sample holder in the vacuum chamber;

[0008] 2) Evacuate the cavity until the internal pressure is less than 5 × 10⁻⁶. -3 After Pa, high-purity argon gas is introduced, and the pressure inside the chamber is controlled at 0.3~0.5Pa. The bias power supply is adjusted to -500~-800V to perform bias cleaning on the substrate surface to remove impurities. The processing time is 10~15min.

[0009] 3) Depositing a metal-doped carbon thin film on the substrate surface using cathode arc magnetic filtration technology, specifically:

[0010] Deposition of Cr / Ti transition layer: Turn on the Cr and Ti arc target, set the target current ratio to 160A / 120A and the voltage ratio to 30V / 30V; introduce argon gas at 100sccm and control the gas pressure at 0.37Pa; adjust the bias voltage to 75V, duty cycle to 60%, and current to 7.5A; deposit for 60min.

[0011] ② Deposition of CrTiN transition layer: Increase Ti arc target current to achieve a current ratio of 160A / 160A and a voltage ratio of 31V / 30.8V; introduce nitrogen gas at 100sccm, keep argon gas flow rate constant, and achieve a gas pressure of 0.34Pa; adjust bias voltage to 75V, duty cycle to 60%, and current to 7.3A; deposit for 60min.

[0012] Deposition of TiNC transition layer: Turn off Cr arc target, turn on central pillar target C target, adjust C target DC current to 4A, duty cycle to 60%, voltage to 395V; reduce nitrogen flow rate to 50sccm, keep argon unchanged; adjust bias voltage to 75V, duty cycle to 60%, current to 4.0A; deposition for 60min;

[0013] Deposition of aC:Ti surface layer: Keep argon flow rate constant, stop nitrogen supply, and deposit for 60 min; then introduce 15 sccm of methane gas, reaching a pressure of 0.34 Pa; adjust bias voltage to 50 V, duty cycle to 60%, current to 3.3 A, and deposit for 10 min; increase methane flow rate to 30 sccm, adjust the DC current of the central target C to 6 A, duty cycle to 60%, voltage to 510 V, keeping other parameters unchanged, and deposit for 10 min; continue to increase methane flow rate to 45 sccm, adjust the DC current of the central target C to 6 A, duty cycle to 60%, voltage to 490 V, keeping other parameters unchanged, and deposit for 10 min; continue to increase methane flow rate to 60 sccm, adjust the DC current of the central target C to 6 A, duty cycle to 60%, voltage to 470 V, keeping other parameters unchanged, and deposit for 10 min; continue to increase methane flow rate to 75 sccm, adjust the DC current of the central target C to 6 A, duty cycle to 60%, voltage to 460 V, keeping other parameters unchanged, and deposit for 20 min.

[0014] In the above-mentioned cathode arc deposition process, Ti arc targets and Cr arc targets are symmetrically arranged on the left and right sides of the vacuum chamber and connected to the vacuum chamber through magnetic filter bends. The magnetic field current near the arc targets on the magnetic filter bends is 70~80A, and the magnetic field current near the vacuum chamber is 40~50A. The central column target C target is located at the center of the vacuum chamber.

[0015] II. Structural Characterization and Performance Evaluation of Cr / Ti Co-doped Carbon Thin Films

[0016] 1. Structure of metal co-doped carbon thin films

[0017] Figure 1 These are surface morphology images of metal co-doped carbon thin films prepared using cathode arc magnetic filtration technology according to the present invention. (a) shows the microstructure of the 300 μm co-doped carbon thin film, and (b) shows the microstructure of the 50 μm co-doped carbon thin film. Here, we can directly observe the surface morphology of the co-doped carbon thin film; the surface of the sample exhibits a regular arrangement.

[0018] Figure 3 This is a Raman spectrum image of a metal co-doped carbon thin film prepared using cathode arc magnetic filtering technology according to the present invention. The image shows the typical Raman spectrum of the film deposited on the FKM substrate. For the co-doped carbon film, a prominent G peak is observed (located at approximately 1530 cm⁻¹). -1 (The location) represents sp in carbon materials 2 The vibrational modes of the in-plane C-C bonds of hybrid carbon atoms are typical characteristic peaks in carbon materials such as graphene or graphite, indicating that the material has a highly ordered graphitized structure. A smaller shoulder peak, the D peak (located at approximately 1350 cm⁻¹), is also present. -1 The strength of the material is related to defects or disorder in carbon materials, and its strength can reflect the defect density of the material. Figure 3 The significance of the G peak and the relatively small size of the D peak indicate that the carbon material has a high degree of graphitization and a low defect content.

[0019] 2. Mechanical and tribological properties of metal co-doped carbon thin films

[0020] 1) Hardness and elastic modulus

[0021] The microhardness and elastic modulus of the film were determined by a nanoindenter using a continuous indentation method. The maximum indentation depth was set to 100 nm (to ensure that the indentation depth of the indenter during the test was less than 1 / 10 of the film thickness, so as to avoid the influence of the substrate on the hardness test). At the same time, in order to reduce measurement error, five points were selected for measurement of each sample during the test, and the average value was taken as the final result of the experiment.

[0022] The hardness of the co-doped carbon film was measured to be between 32.52 and 34.31 GPa, and the elastic modulus was between 333.90 and 352.89 GPa.

[0023] 2) Tribological properties

[0024] The tribological properties of metal-doped carbon thin films in a dry atmospheric environment were determined using a ball-disc friction tester. The selected friction load was 30 N, the rotation speed was 1000 r / min, and the friction pair consisted of Φ4 mm 440c stainless steel balls with a rotation radius of 4 mm.

[0025] Figure 4The friction coefficient curve is shown. Based on the above friction test parameters, the friction coefficient of the metal-doped carbon film is consistently between 0.30 and 0.35. Figure 4 a) Compared to fluoropolymer rubber without a carbon film, the coefficient of friction fluctuates around 0.75 ( Figure 4 (b) The lubrication performance and wear resistance of metal co-doped carbon films are significantly improved.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] The co-doped carbon thin film obtained by the method of this invention significantly improves tribological performance. The increased content of hydrogenated amorphous carbon film within the film maintains its density and hardness. The cathode arc magnetic filtration technology ensures uniform dispersion of dopant elements within the film, guaranteeing performance enhancement even with minimal dopant. The improved orderliness of the friction interface during friction results in a low coefficient of friction and low wear rate, thus enhancing the tribological properties of the film. This unique metal co-doped carbon thin film method significantly improves carbon thin film deposition quality, is simple, and cost-effective, providing guidance for industrial production. Attached Figure Description

[0028] Figure 1 The image shows the microstructure of the co-doped carbon film prepared according to the present invention; where a and b correspond to the SEM images of the prepared co-doped carbon film at 300 μm and 50 μm, respectively.

[0029] Figure 2 This is a schematic diagram of the structure of the co-doped carbon thin film prepared in this invention.

[0030] Figure 3 This is a Raman spectral image of a metal co-doped carbon thin film prepared using cathode arc magnetic filtering technology according to the present invention.

[0031] Figure 4 Friction coefficient curves of the co-doped carbon thin film (a) prepared for this invention and friction curves of the original untreated rubber (b). Detailed Implementation

[0032] The present invention will be further explained and described below with reference to specific embodiments. Example

[0033] (1) Using commercially available Cr / Ti sputtering targets; ultrasonically cleaning the substrate (fluoroether rubber) with alcohol for 20 min to remove surface contaminants, then drying it with argon gas and placing it on the sample holder in the magnetron sputtering chamber; evacuating the chamber until the pressure inside is less than 5 × 10⁻⁶. -3After Pa, high-purity argon gas is introduced, and the argon gas flow rate is adjusted to control the pressure in the chamber to 0.3 Pa. The bias power supply is adjusted to -600 V to perform bias cleaning on the substrate surface to remove impurities. The processing time is 15 min.

[0034] (2) The transition layer can be selected according to the chosen substrate; adjust the chamber pressure to 0.3~0.5Pa, adjust the pulse bias voltage to -75V, and deposit a metal micro-doped carbon thin film using cathode arc magnetic filtering technology. The specific steps are as follows:

[0035] Deposition of Cr / Ti transition layer: Turn on the Cr and Ti arc target, set the target current ratio to 160A / 120A and the voltage ratio to 30V / 30V; introduce argon gas at 100sccm and control the gas pressure at 0.37Pa; adjust the bias voltage to 75V, duty cycle to 60%, and current to 7.5A; deposit for 60min.

[0036] ② Deposition of CrTiN transition layer: Increase Ti arc target current to achieve a current ratio of 160A / 160A and a voltage ratio of 31V / 30.8V; introduce nitrogen gas at 100sccm, keep argon gas flow rate constant, and achieve a gas pressure of 0.34Pa; adjust bias voltage to 75V, duty cycle to 60%, and current to 7.3A; deposit for 60min.

[0037] Deposition of TiNC transition layer: Turn off Cr arc target, turn on central pillar target C target, adjust C target DC current to 4A, duty cycle to 60%, voltage to 395V; reduce nitrogen flow rate to 50sccm, keep argon unchanged; adjust bias voltage to 75V, duty cycle to 60%, current to 4.0A; deposition for 60min;

[0038] Deposition of aC:Ti surface layer: Keep argon flow rate constant, stop nitrogen supply, and deposit for 60 min; then introduce 15 sccm of methane gas, reaching a pressure of 0.34 Pa; adjust bias voltage to 50 V, duty cycle to 60%, current to 3.3 A, and deposit for 10 min; increase methane flow rate to 30 sccm, adjust the DC current of the central target C to 6 A, duty cycle to 60%, voltage to 510 V, keeping other parameters unchanged, and deposit for 10 min; continue to increase methane flow rate to 45 sccm, adjust the DC current of the central target C to 6 A, duty cycle to 60%, voltage to 490 V, keeping other parameters unchanged, and deposit for 10 min; continue to increase methane flow rate to 60 sccm, adjust the DC current of the central target C to 6 A, duty cycle to 60%, voltage to 470 V, keeping other parameters unchanged, and deposit for 10 min; continue to increase methane flow rate to 75 sccm, adjust the DC current of the central target C to 6 A, duty cycle to 60%, voltage to 460 V, keeping other parameters unchanged, and deposit for 20 min.

[0039] The microhardness of the film was measured to be 4.3 GPa and the elastic modulus to be 75.39 GPa using a nanoindenter via continuous indentation. Raman spectroscopy indicated that the carbon material exhibited a high degree of graphitization and a low defect content. The friction coefficient of the co-doped carbon film was consistently 0.32. The friction life measured under vacuum conditions exceeded 900,000 cycles, and the friction life measured under atmospheric conditions exceeded 300,000 cycles.

[0040] The Cr / Ti co-doping method for preparing carbon thin films significantly improves the film quality and tribological properties of fluoroether rubber, while also promoting the ordered transformation of the friction interface during friction, thereby enhancing tribological properties. The overall method is simple, cost-effective, and has guiding significance for industrial production.

Claims

1. A method for preparing gradient multilayer carbon thin films on the surface of fluoroether rubber using Cr / Ti co-doping, characterized in that, Includes the following steps: 1) Clean the substrate with alcohol using ultrasonic cleaning for 10-20 minutes to remove surface contaminants, blow dry, and place it on the sample rack in the vacuum chamber; 2) Evacuate to a pressure less than 5 × 10⁻⁶ -3 After Pa, high-purity argon gas is introduced, and the pressure in the vacuum chamber is controlled at 0.3~0.5Pa. The bias power supply is adjusted to -500~-800V to perform bias cleaning on the substrate surface to remove impurities. The processing time is 10~15min. 3) Depositing a metal-doped carbon thin film on the substrate surface using cathode arc magnetic filtration technology, specifically: Deposition of Cr / Ti transition layer: Turn on the Cr and Ti arc target, set the target current ratio to 160A / 120A and the voltage ratio to 30V / 30V; introduce argon gas at 100sccm and control the gas pressure at 0.37Pa; adjust the bias voltage to 75V, duty cycle to 60%, and current to 7.5A; deposit for 60min. ② Deposit CrTiN transition layer: Increase Ti arc target current, current ratio reaches 160A / 160A, voltage ratio 31V / 30.8V; Nitrogen gas was introduced at 100 sccm, while the argon gas flow rate remained constant, and the gas pressure reached 0.34 Pa; the bias voltage was adjusted to 75 V, the duty cycle to 60%, and the current to 7.3 A. Deposition for 60 minutes; Depositing the TiNC transition layer: Turn off the Cr arc target, turn on the central column target C target, adjust the DC current of the C target to 4A, the duty cycle to 60%, and the voltage to 395V; reduce the nitrogen flow rate to 50sccm, and keep the argon flow rate unchanged. Adjust the bias voltage to 75V, duty cycle to 60%, and current to 4.0A; deposit for 60 minutes. Deposition of aC:Ti surface layer: Keep argon flow rate constant, stop nitrogen supply, and deposit for 60 min; then introduce 15 sccm of methane gas, reaching a pressure of 0.34 Pa; adjust bias voltage to 50 V, duty cycle to 60%, current to 3.3 A, and deposit for 10 min; increase methane flow rate to 30 sccm, adjust the DC current of the central target C to 6 A, duty cycle to 60%, voltage to 510 V, keeping other parameters unchanged, and deposit for 10 min; continue to increase methane flow rate to 45 sccm, adjust the DC current of the central target C to 6 A, duty cycle to 60%, voltage to 490 V, keeping other parameters unchanged, and deposit for 10 min; continue to increase methane flow rate to 60 sccm, adjust the DC current of the central target C to 6 A, duty cycle to 60%, voltage to 470 V, keeping other parameters unchanged, and deposit for 10 min; continue to increase methane flow rate to 75 sccm, adjust the DC current of the central target C to 6 A, duty cycle to 60%, voltage to 460 V, keeping other parameters unchanged, and deposit for 20 min.

2. The method for preparing gradient multi-level carbon thin films on the surface of fluoroether rubber using Cr / Ti co-doping as described in claim 1, characterized in that, In step 3), the Ti arc target and the Cr arc target are symmetrically arranged on the left and right sides of the vacuum chamber, and the central column target C target is located in the center of the vacuum chamber.

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