Method for preparing gradient multi-stage multi-layer carbon film by co-doping Cr / Ti on fluoroether rubber surface

Abstract

The invention discloses a method for preparing a gradient multi-stage multi-layer carbon film by co-doping Cr / Ti on the surface of fluoroether rubber, which comprises the following steps: cleaning and blow-drying a substrate, putting the substrate into a magnetron sputtering cavity, pumping to a high vacuum condition, and introducing Ar gas to clean the substrate; and obtaining the modified metal micro-doped carbon film by adopting a cathode arc magnetic filtration technology. The friction performance of the obtained co-doped carbon film is obviously improved, hydrogenated amorphous carbon film components in the film are increased, and meanwhile the density and hardness of the film are kept; the cathode arc magnetic filtering technology enables the doped elements to be uniformly dispersed in the film, so that the performance of the film can be improved by a small amount of doped elements; the order degree of a friction interface of the thin film in the friction process is obviously improved, the thin film has a low friction coefficient and a low wear rate, and the tribological performance of the thin film is improved.

Description

Technical Field

[0001] The invention relates to the technical field of vacuum coating and thin film lubrication, and in particular to a method for preparing a gradient multi-level multi-layer carbon film on the surface of fluoroether rubber by co-doping Cr / Ti. Background Art

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

[0003] In order to overcome these shortcomings, the present invention proposes an innovative technical solution, which is to prepare a carbon film on the surface of fluoroether rubber by cathode arc magnetic filtration technology. This method can effectively improve the bonding force of the film, ensure the uniformity and stability of the film, thereby significantly improving the wear resistance of fluoroether rubber and reducing its friction coefficient. In this way, the present invention not only solves the limitations of traditional film preparation technology, but also provides a more reliable technical guarantee for the high-performance application of fluoroether rubber. Summary of the invention

[0004] In view of the problems existing in the above background technology, the present invention discloses a method for preparing a gradient multi-level multi-layer carbon film on the surface of fluoroether rubber by co-doping Cr / Ti.

[0005] 1. Preparation of Cr / Ti co-doped carbon film The Cr / Ti co-doped carbon film of the present invention comprises the following steps: 1) Ultrasonic clean the substrate with alcohol for 10-20 minutes to remove surface contaminants, blow dry and place it on the vacuum chamber sample holder; 2) Evacuate the chamber until the pressure is less than 5×10 -3 After the pressure reaches 0.3-0.5 Pa, high-purity argon gas is introduced, the pressure in the chamber is controlled to be 0.3-0.5 Pa, the bias power supply is adjusted to -500-800 V, and the surface of the substrate is bias cleaned to remove impurities on the surface of the substrate. The treatment time is 10-15 minutes; 3) Using cathode arc magnetic filtration technology to deposit metal micro-doped carbon film on the surface of the substrate, specifically: Deposition of Cr / Ti transition layer: Turn on Cr and Ti arc targets, 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 to 0.37Pa; adjust the bias voltage to 75V, the duty cycle to 60%, and the current to 7.5A; deposit for 60min; ②Deposition of CrTiN transition layer: increase the Ti arc target current, the current ratio reaches 160A / 160A, the voltage ratio reaches 31V / 30.8V; introduce nitrogen 100sccm, the argon flow rate remains unchanged, and the gas pressure reaches 0.34Pa; adjust the bias voltage to 75V, the duty cycle to 60%, and the current to 7.3A; deposit for 60min; Deposition of TiNC transition layer: turn off the Cr arc target, turn on the center column target C target, adjust the C target DC current to 4A, duty cycle 60%, voltage 395V; reduce the nitrogen flow rate to 50sccm, and keep the argon gas unchanged; adjust the bias voltage to 75V, duty cycle 60%, current 4.0A; deposit for 60min; Deposition of aC: Ti surface layer: keep the argon flow rate unchanged, stop the nitrogen flow, and deposit for 60 minutes; then introduce 15sccm methane gas, and the gas pressure reaches 0.34Pa; adjust the bias voltage to 50V, the duty cycle to 60%, the current to 3.3A, and the deposition time to 10min; increase the methane flow rate to 30sccm, adjust the central column target C target DC current to 6A, the duty cycle to 60%, the voltage to 510V, and other parameters remain unchanged, and deposit for 10min; continue to increase the methane flow rate to 45sccm, adjust the central column target C target DC current to 6A, the duty cycle to 60%, the voltage to 490V, and other parameters remain unchanged, and deposit for 10min; continue to increase the methane flow rate to 60sccm, adjust the central column target C target DC current to 6A, the duty cycle to 60%, the voltage to 470V; other parameters remain unchanged, and deposit for 10min; continue to increase the methane flow rate to 75sccm, adjust the central column target C target DC current to 6A, the duty cycle to 60%, the voltage to 460V, and other parameters remain unchanged, and deposit for 20min.

[0006] In the above-mentioned cathode arc deposition process, the Ti arc target and the Cr arc target are symmetrically arranged on the left and right sides of the vacuum chamber and connected to the vacuum chamber through a magnetic filtration elbow, wherein the magnetic field current on the magnetic filtration elbow close to the arc target is 70~80A, and the magnetic field current close to the vacuum chamber is 40~50A; the central column target C target is located in the center of the vacuum chamber.

[0007] 2. Structural Characterization and Performance Evaluation of Cr / Ti Co-doped Carbon Films 1. Structure of metal co-doped carbon film Figure 1The surface morphology of the metal co-doped carbon film prepared by the cathode arc magnetic filtration technology in the present invention. (a) The microstructure of the co-doped carbon film at 300 μm, (b) The microstructure of the co-doped carbon film at 50 μm. Here we can intuitively see the surface morphology of the co-doped carbon film, and the surface of the sample is regularly arranged.

[0008] Figure 3 This is a Raman spectrum image of the metal co-doped carbon film prepared by cathode arc magnetic filtering technology in 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 (located at about 1530 cm -1 ) represents the sp 2 The vibration mode of the C-C bond in the plane of hybrid carbon atoms is a typical characteristic peak of carbon materials such as graphene or graphite, indicating that the material has a highly ordered graphitized structure. The smaller shoulder peak D peak (located at about 1350 cm -1 The intensity of the carbon nanotubes (at 200 nm) is related to the defects or disorder in the carbon material, and its intensity can reflect the defect density of the material. Figure 3 The significance of the G peak and the relatively small D peak indicate that the carbon material has a high degree of graphitization and a low defect content.

[0009] 2. Mechanical and tribological properties of metal co-doped carbon films 1) Hardness and elastic modulus The microhardness and elastic modulus of the film were measured by continuous indentation method using a nanoindenter, and 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 to avoid the influence of the substrate on the hardness test). At the same time, in order to reduce the measurement error, 5 points were selected for each sample during the test, and the average value was taken as the final result of the experiment.

[0010] The measured hardness of the co-doped carbon film is between 32.52 and 34.31 GPa, and the elastic modulus is between 333.90 and 352.89 GPa.

[0011] 2) Tribological properties The friction and wear properties of metal micro-doped carbon films in dry atmospheric environment were measured using a ball-disc friction machine. The selected friction load was 30N, the rotation speed was 1000r / min, the friction pair was a Φ4 mm 440c stainless steel ball, and the rotation radius was 4mm; Figure 4 is the friction coefficient curve. Through the above friction test parameters, the friction coefficient of the metal-doped carbon film is stable between 0.30 and 0.35 ( Figure 4 a), compared with the fluoroether rubber without carbon film, the friction coefficient fluctuates around 0.75 ( Figure 4b) The lubrication performance and wear resistance of metal co-doped carbon films are significantly improved.

[0012] Compared with the prior art, the present invention has the following advantages: The co-doped carbon film obtained by the method of the present invention significantly improves the friction performance, the hydrogenated amorphous carbon film component inside the film increases, and the density and hardness of the film itself are also maintained; the cathode arc magnetic filtration technology allows the doping elements to be evenly dispersed inside the film, thereby ensuring that a small amount of doping elements can achieve film performance improvement; the order of the friction interface of the film during the friction process is significantly improved, with a low friction coefficient and low wear rate, and the tribological properties of the film are improved. This special metal co-doped carbon film method can significantly improve the deposition quality of the carbon film, the method is simple, the cost is controllable, and it has guiding significance for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The microstructure of the co-doped carbon film prepared by the present invention; a and b correspond to the SEM images of the prepared co-doped carbon film at 300 μm and 50 μm, respectively.

[0014] Figure 2 This is a schematic diagram of the structure of the co-doped carbon film prepared by the present invention.

[0015] Figure 3 This is a Raman spectrum image of a metal co-doped carbon film prepared by cathode arc magnetic filtering technology in the present invention.

[0016] Figure 4 The friction coefficient curve of the co-doped carbon film prepared in the present invention (a) and the friction curve of the original untreated rubber (b). DETAILED DESCRIPTION

[0017] The present invention is further explained below with reference to specific embodiments. Example

[0018] (1) Using commercially available Cr / Ti targets, the substrate (fluoroether rubber) was ultrasonically cleaned with alcohol for 20 min to remove surface contaminants, then dried with argon and placed on the sample holder of the magnetron sputtering chamber; the chamber was evacuated to a pressure of less than 5×10 -3 After 0.05 Pa, high-purity argon gas was introduced, and the argon gas flow rate was adjusted to control the pressure in the chamber to 0.3 Pa. The bias power supply was adjusted to -600 V, and the surface of the substrate was bias cleaned to remove impurities on the surface of the substrate. The treatment time was 15 min. (2) The transition layer can be selected according to the selected substrate; adjust the chamber pressure to 0.3~0.5Pa, adjust the pulse bias to -75V, and use the cathode arc magnetic filtration technology to deposit the metal micro-doped carbon film. The specific steps are as follows: Deposition of Cr / Ti transition layer: Turn on Cr and Ti arc targets, 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 to 0.37Pa; adjust the bias voltage to 75V, the duty cycle to 60%, and the current to 7.5A; deposit for 60min; ②Deposition of CrTiN transition layer: increase the Ti arc target current, the current ratio reaches 160A / 160A, the voltage ratio reaches 31V / 30.8V; introduce nitrogen 100sccm, the argon flow rate remains unchanged, and the gas pressure reaches 0.34Pa; adjust the bias voltage to 75V, the duty cycle to 60%, and the current to 7.3A; deposit for 60min; Deposition of TiNC transition layer: turn off the Cr arc target, turn on the center column target C target, adjust the C target DC current to 4A, duty cycle 60%, voltage 395V; reduce the nitrogen flow rate to 50sccm, and keep the argon gas unchanged; adjust the bias voltage to 75V, duty cycle 60%, current 4.0A; deposit for 60min; Deposition of aC: Ti surface layer: keep the argon flow rate unchanged, stop the nitrogen flow, and deposit for 60 minutes; then introduce 15sccm methane gas, and the gas pressure reaches 0.34Pa; adjust the bias voltage to 50V, the duty cycle to 60%, the current to 3.3A, and the deposition time to 10min; increase the methane flow rate to 30sccm, adjust the central column target C target DC current to 6A, the duty cycle to 60%, the voltage to 510V, and other parameters remain unchanged, and deposit for 10min; continue to increase the methane flow rate to 45sccm, adjust the central column target C target DC current to 6A, the duty cycle to 60%, the voltage to 490V, and other parameters remain unchanged, and deposit for 10min; continue to increase the methane flow rate to 60sccm, adjust the central column target C target DC current to 6A, the duty cycle to 60%, the voltage to 470V; other parameters remain unchanged, and deposit for 10min; continue to increase the methane flow rate to 75sccm, adjust the central column target C target DC current to 6A, the duty cycle to 60%, the voltage to 460V, and other parameters remain unchanged, and deposit for 20min.

[0019] The microhardness of the film was measured by a nanoindenter through continuous indentation method, and the elastic modulus was 4.3 GPa and 75.39 GPa; Raman spectroscopy showed that the carbon material had a high degree of graphitization and a low defect content. The friction coefficient of the co-doped carbon film was obtained to be stable at 0.32. The friction life measured in a vacuum environment was greater than 900,000 cycles, and the friction life measured in an atmospheric environment was greater than 300,000 cycles.

[0020] The method of preparing carbon film by Cr / Ti co-doping significantly improves the film quality of carbon film and the friction performance of fluoroether rubber, and at the same time promotes the orderly transformation of the friction interface during the friction process, thereby improving the tribological performance. The overall method is simple, cost-controllable, and has guiding significance for industrial production.

Claims

1. A method for preparing a gradient multi-level multi-layer carbon film on the surface of fluoroether rubber by co-doping Cr / Ti, characterized in that: The following steps are involved: 1) Ultrasonic clean the substrate with alcohol for 10-20 minutes to remove surface contaminants, blow dry and place on the sample holder in the vacuum chamber; 2) Evacuate to a pressure less than 5×10 -3 After the vacuum chamber reaches 0.3-0.5 Pa, high-purity argon gas is introduced, the pressure in the vacuum chamber is controlled to be 0.3-0.5 Pa, the bias power supply is adjusted to -500-800 V, and the surface of the substrate is bias cleaned to remove impurities on the surface of the substrate. The treatment time is 10-15 minutes; 3) Using cathode arc magnetic filtration technology to deposit metal micro-doped carbon film on the surface of the substrate, specifically: Deposition of Cr / Ti transition layer: Turn on Cr and Ti arc targets, 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 to 0.37Pa; adjust the bias voltage to 75V, the duty cycle to 60%, and the current to 7.5A; deposit for 60min; ② Deposition of CrTiN transition layer: increase the Ti arc target current, the current ratio reaches 160A / 160A, and the voltage ratio reaches 31V / 30.8V; 100 sccm of nitrogen was introduced, the argon flow rate remained unchanged, 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; Sedimentation 60min; Deposition of TiNC transition layer: turn off the Cr arc target, turn on the center column target C target, adjust the C target DC current to 4A, duty cycle 60%, voltage 395V; reduce the nitrogen flow rate to 50sccm, and keep the argon gas unchanged; Adjust the bias voltage to 75V, the duty cycle to 60%, the current to 4.0A, and deposit for 60 minutes; Deposition of aC: Ti surface layer: keep the argon flow rate unchanged, stop the nitrogen flow, and deposit for 60 minutes; then introduce 15sccm methane gas, and the gas pressure reaches 0.34Pa; adjust the bias voltage to 50V, the duty cycle to 60%, the current to 3.3A, and the deposition time to 10min; increase the methane flow rate to 30sccm, adjust the central column target C target DC current to 6A, the duty cycle to 60%, the voltage to 510V, and other parameters remain unchanged, and deposit for 10min; continue to increase the methane flow rate to 45sccm, adjust the central column target C target DC current to 6A, the duty cycle to 60%, the voltage to 490V, and other parameters remain unchanged, and deposit for 10min; continue to increase the methane flow rate to 60sccm, adjust the central column target C target DC current to 6A, the duty cycle to 60%, the voltage to 470V; other parameters remain unchanged, and deposit for 10min; continue to increase the methane flow rate to 75sccm, adjust the central column target C target DC current to 6A, the duty cycle to 60%, the voltage to 460V, and other parameters remain unchanged, and deposit for 20min.

2. A method for preparing a gradient multi-level multi-layer carbon film on the surface of fluoroether rubber by co-doping Cr / Ti as claimed 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 center column target C target is located in the center of the vacuum chamber.

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