A DLC self-lubricating film and a method for preparing the same

Abstract

The application provides a DLC self-lubricating film and a preparation method thereof, and relates to the technical field of surface modification treatment. In view of inherent defects and application bottlenecks of the diamond-like carbon film, the application combines material composition and structure gradient by using composite magnetic filter cathode arc deposition (FCVA) and plasma enhanced chemical vapor deposition (PECVD) film coating technology, adopts the method of adding a transition layer film to improve the thermal stability of the material, improve the internal stress of the material and improve the film base bonding force. The DLC self-lubricating film provided by the application has strong bonding force with the substrate, good wear resistance and thermal stability, long service life and high reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of surface modification treatment, in particular to a DLC self-lubricating film and a preparation method thereof. BACKGROUND

[0002] As a green energy technology, wind power generation has been widely concerned by countries around the world, and gradually becomes an important new energy generation method. In recent years, with the increase of installed capacity, the failure and reliability of wind turbine generators have been paid more and more attention. As a key component of wind turbine generators, the reliability of bearings will directly affect the service life of the generators.

[0003] According to existing data, 80% of the failures of various types of wind turbine bearings (yaw bearing assembly, wind blade spindle bearing, variable pitch bearing) are related to lubrication. At present, wind turbine bearings generally use high-performance lubricating grease for lubrication. In order to realize long service life (20 years) and stable and reliable operation of each component, domestic bearing manufacturers mostly use imported brands such as Shell and Mobil. The purpose of bearing lubrication is to reduce internal friction and wear of the bearing. However, the environment of wind turbines is complex (Gobi desert, mountain pass, seaside island, etc.), and working in extreme harsh environments is prone to problems such as deterioration and leakage of lubricating grease, resulting in serious friction, sticking and wear of wind turbine bearing components under the condition of oil shortage and oil leakage due to the lack of complete lubricating grease film.

[0004] In order to solve the bearing failure caused by the problem of lubricating grease, many research teams and manufacturers have adopted solid lubrication technology to improve the service life of bearings. Diamond-like carbon (DLC) film is a very excellent solid lubricant, and its excellent friction and wear performance makes it have broad application prospects in wind turbine bearing lubrication. Although gas deposition technology can generate DLC film in a large area, the problems of brittleness, high internal stress and poor film-substrate adhesion of DLC film not only limit the generation thickness of the film (difficult to exceed 2 μm), but also shorten the service life and reliability of the film. In addition, the thermal stability of DLC film is poor, and it will graphitize due to the precipitation of hydrogen at 250℃, thereby limiting its application in high temperature fields. SUMMARY

[0005] The purpose of the present application is to provide a DLC self-lubricating film and a preparation method thereof. The DLC self-lubricating film provided by the present application has strong adhesion to the substrate, good wear resistance and thermal stability, long service life and high reliability.

[0006] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0007] The present application provides a DLC self-lubricating film, characterized in that it comprises an ion-implanted Cr layer, a DLC transition layer and a hydrogen-containing DLC layer which are sequentially stacked on a steel substrate.

[0008] The Cr ions in the ion-implanted Cr layer exist in the form of C2Cr3;

[0009] The DLC transition layer is made of high-SP 3 The high-SP 2 The high-SP 2 The high-SP 3 The high-SP

[0010] The high-SP 3 The high-SP 3 The high-SP 2 The high-SP 2 The high-SP 2 The high-SP 3 The high-SP 2 The high-SP 3 The high-SP

[0011] Preferably, the thickness of the ion-implanted Cr layer is 0.4-0.6 μm.

[0012] Preferably, the thickness of the high-SP 3 The high-SP

[0013] The high-SP 2 The total thickness of the high-SP 2 The high-SP

[0014] The total thickness of the DLC transition layer is 0.2-0.5 μm.

[0015] Preferably, the thickness of the high-SP 3 The high-SP 3 The high-SP 2 The high-SP 2 The high-SP

[0016] Preferably, the thickness of the hydrogen-containing DLC layer is 0.7-1.3 μm.

[0017] The present application provides a preparation method of the DLC self-lubricating film as described above, which comprises the following steps:

[0018] Cr ions are implanted into the surface of a steel substrate using a magnetically filtered cathodic arc deposition method to form an ion-implanted Cr layer.

[0019] High SP content was sequentially deposited on the surface of the ion-implanted Cr layer using a magnetically filtered cathodic arc deposition method. 2 DLC films with valence bond structure and high SP 3 A DLC film with a valence bond structure is formed to create a DLC transition layer;

[0020] A hydrogen-containing DLC ​​layer was deposited on the surface of the DLC transition layer using plasma-enhanced chemical vapor deposition to obtain the DLC self-lubricating film.

[0021] Preferably, the preparation conditions for the ion-implanted Cr layer include: using a Cr target as the cathode, and the Cr ion implantation working gas pressure being 3.0 × 10⁻⁶. -1 ~6.0×10 -1 Pa, main arc voltage is 40-80V, main arc pulse width is 200-500μs, bias amplitude is 15-25kV, bias pulse frequency is 75-90Hz independently of main arc pulse frequency, and injection time is 0.5-1h.

[0022] Preferably, the high SP 2 The deposition conditions for DLC films with valence bond structures include: using a graphite target as the cathode, setting the substrate DC bias voltage to 1600–2000 V; the cathode arc source current to be 40–60 A; and a single layer of high SP... 2 The high-voltage power supply for growing DLC ​​films with valence bond structures operates in sinusoidal mode with a frequency of 3–6 Hz, a duty cycle of 40–60%, a peak height of 500–600 V, and a peak-to-valence value of 400–450 V. Multi-stage excitation coils are configured with voltages ranging from 4 to 60 V. Single-layer high SP... 2 The deposition time for DLC films with valence bonds is 120–200 s;

[0023] The high SP 3 The deposition conditions for the DLC film with valence bond structure include: increasing the DC bias voltage of the substrate to 1800–2200V, maintaining the cathode arc source current at 40–60A; the operating waveform of the high-voltage power supply is a sine wave mode with a frequency of 3–6Hz, a duty cycle of 40–60%, a peak height of 500–600V, and a peak-to-valley value of 400–450V; setting the voltage of the multi-stage excitation coil to 4–60V; after deposition for 25–30 minutes, adjusting the DC bias voltage of the substrate to 1400–1700V, increasing the cathode arc source current to 50–70A, and keeping other power supply parameters unchanged, continuing deposition for 60–120 minutes.

[0024] Preferably, the deposition conditions of the hydrogen-containing DLC layer include: a vacuum chamber base temperature of 100℃, a substrate direct current bias of -800 to -1200V, a duty cycle of 50%, an Ar flow rate of 10 to 20sccm, a C2H2 flow rate of 110 to 130sccm, a vacuum chamber internal vacuum degree controlled at 0.8 to 1.2Pa, an ion source voltage of 1200 to 1600V, a duty cycle of 50%, and a deposition time of 6 to 8h.

[0025] Preferably, before the Cr ion implantation on the steel substrate surface, the steel substrate is further subjected to argon ion sputtering cleaning.

[0026] The present application provides a DLC self-lubricating film, which comprises an ion-implanted Cr layer, a DLC transition layer and a hydrogen-containing DLC layer attached to a steel substrate in sequence; the Cr ion in the ion-implanted Cr layer exists in the form of C2Cr3; the DLC transition layer is formed by high SP 3 bond structure DLC films and a plurality of layers of high SP 2 bond structure DLC films in sequence; the high SP 2 bond structure DLC film is in contact with the ion-implanted Cr layer, the high SP 3 bond structure DLC film is in contact with the hydrogen-containing DLC layer; the content of SP 3 bond in the high SP 3 bond structure DLC film is higher than that of SP 2 bond; the content of SP 2 bond in the high SP 2 bond structure DLC film is higher than that of SP 3 bond; along the direction from the ion-implanted Cr layer to the hydrogen-containing DLC layer, the content of SP 2 bond in the DLC transition layer gradually decreases, and the content of SP 3 bond gradually increases.

[0027] The multi-layer transition layer of the present application can well relieve the internal stress of the DLC self-lubricating film, wherein the Cr element is doped in the form of ion implantation as a primer layer, which can form C2Cr3 with C in the steel substrate, the DLC transition layer adopts a gradient form, which can relieve the hardness difference between the primer layer and the hydrogen-containing DLC layer, and the different SP 2 and SP 3 structure contents make the hydrogen-containing DLC film stably attached to the substrate without falling off, enrich the tribological properties of the metal hard protective film, and expand the application field of the DLC self-lubricating film.

[0028] The Cr ion implanted by the present application exists in the form of carbide in the film, and the different SP 2 and SP 3The proportion content microstructure can improve the toughness of the DLC transition layer, further improve the bonding strength of the surface hydrogen-containing DLC film and the substrate, and generate Cr oxide protective film in high-temperature friction experiment, thereby improving the high-temperature tribological performance of the DLC self-lubricating film.

[0029] The prepared DLC self-lubricating film has high compactness, large hardness, good mechanical performance and low friction coefficient.

[0030] The film preparation process adopted by the application is appropriate, the film surface is uniform, and the film thickness can be more than 2 microns (the thickness of the DLC self-lubricating film is 1.5-2.5 microns), which is thicker than the common DLC film and has higher wear resistance.

[0031] The application adopts a composite multifunctional ion plating film equipment similar to the film plating equipment in industrial production, and simultaneously adopts a magnetic filter cathode arc deposition (FCVA) and a plasma enhanced chemical vapor deposition (PECVD) composite technology to prepare the target film, which is simple to operate and is conducive to large-scale batch production in industry.

[0032] The results of the embodiments show that the DLC self-lubricating film prepared by the application has high film-substrate bonding force, so that the DLC film can still maintain good interface bonding between the substrate and the film under high load (about 3 GPa) pressure stress. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 It is a physical diagram of a two-dimensional rotating hanger used in the film plating process of the application;

[0034] Figure 2 It is a structure schematic diagram of the DLC self-lubricating film prepared by the application;

[0035] Figure 3 It is a friction coefficient curve when the DLC self-lubricating film of the application embodiment 1 and the comparative example 1 is compounded with a conventional low-viscosity grease;

[0036] Figure 4 It is a wear scar profile curve of the DLC self-lubricating film of the application embodiment 1 and the comparative example 1 after the friction and wear test of the conventional high-viscosity grease and low-viscosity grease composite lubrication system;

[0037] Figure 5 It is a surface image and scratch curve of the nanometer gradient composite DLC self-lubricating film of the application embodiment 1 and the comparative example 1 after the scratch test;

[0038] Figure 6 It is the Raman spectrum of the DLC self-lubricating film of the application embodiment 1 before and after annealing. DETAILED DESCRIPTION

[0039] like Figure 2 As shown, the present invention provides a DLC self-lubricating film, comprising an ion-implanted Cr layer, a DLC transition layer and a hydrogen-containing DLC ​​layer sequentially stacked on a steel substrate;

[0040] The Cr ions in the ion-implanted Cr layer exist in the form of C2Cr3;

[0041] The DLC transition layer is made of high SP 3 DLC films with valence bond structure and several layers of high SP 2 The DLC film with valence bond structure is formed by sequentially stacking layers; the high SP 2 The DLC film with valence bond structure is in contact with the ion-implanted Cr layer, and the high SP 3 A DLC film with valence bond structure is in contact with a hydrogen-containing DLC ​​layer;

[0042] The high SP 3 SP in DLC films with valence bond structure 3 The content of valence bonds is higher than that of SP. 2 The content of valence bonds, the high SP 2 SP in DLC films with valence bond structure 2 The content of valence bonds is higher than that of SP. 3 Valence bond content; along the direction from the ion-implanted Cr layer to the hydrogen-containing DLC ​​layer, the SP content in the DLC transition layer. 2 The content of valence bonds gradually decreases, SP 3 The content of valence bonds gradually increases.

[0043] This invention does not have special requirements for the steel matrix; any steel matrix well known in the art can be used, such as high-speed steel, pre-hardened steel, hot work die steel, tool steel, and cold work die steel. In the embodiments of this invention, a GCr15 matrix is ​​specifically used.

[0044] The DLC self-lubricating film provided by this invention includes an ion-implanted Cr layer attached to a steel substrate, wherein Cr ions in the ion-implanted Cr layer exist in the form of C2Cr3. In this invention, the thickness of the ion-implanted Cr layer is preferably 0.4–0.6 μm, more preferably 0.45–0.55 μm.

[0045] The DLC self-lubricating film provided by the present invention includes a DLC transition layer attached to the surface of the ion-implanted Cr layer.

[0046] In this invention, the DLC transition layer is composed of high SP 3 DLC films with valence bond structure and several layers of high SP 2 The DLC film with valence bond structure is formed by sequentially stacking layers; the high SP 2The high SP 3 The high SP 2 The high SP 3 The high SP

[0047] In the present application, the high SP 3 The high SP 3 The high SP 2 The high SP 2 The high SP 2 The high SP 3 The high SP 3 The high SP 3 The high SP 2 The high SP 2 The high SP

[0048] In the present application, the high SP 2 The high SP 2 The high SP 2 The high SP 3 The high SP 2 The high SP 3 The high SP

[0049] The multi-layer transition layer of the present application can well relieve the internal stress of the DLC self-lubricating film, and the Cr element is incorporated in the form of ion implantation as the primer layer, which can form C2Cr3 with C in the steel matrix, the DLC transition layer adopts a gradient form, and the different SP 2 and SP 3 contents of structure make the hydrogen-containing DLC film stably adhere to the matrix without falling off, enrich the tribological properties of the metal hard protective film, and expand the application field of the DLC self-lubricating film.

[0050] The Cr ions of the ion implantation of the present application exist in the form of carbide in the thin film, and the microstructure of different SP 2 and SP 3 proportion content can improve the toughness of the DLC transition layer, further improve the bonding strength of the surface hydrogen-containing DLC film and the substrate, and generate Cr oxide protective film in high-temperature friction experiment, thereby improving the high-temperature tribological properties of the DLC self-lubricating thin film.

[0051] The DLC self-lubricating thin film provided by the present application comprises a hydrogen-containing DLC layer attached to the surface of the DLC transition layer. In the present application, the thickness of the hydrogen-containing DLC layer is preferably 0.7-1.3 μm, more preferably 0.8-1.2 μm, and further preferably 0.9-1.1 μm.

[0052] In the present application, the total thickness of the DLC self-lubricating thin film is preferably 1.5-2.5 μm, and more preferably 2.1-2.5 μm. Compared with common DLC thin films, the present application has a thicker film thickness and higher wear resistance.

[0053] The present application provides a preparation method of the DLC self-lubricating thin film described in the above scheme, comprising the following steps:

[0054] Cr ions are implanted on the surface of a steel substrate by a magnetic filter cathode arc deposition method to form an ion-implanted Cr layer;

[0055] A DLC film with high SP 2 and high SP 3 bond structure is deposited on the surface of the ion-implanted Cr layer by a magnetic filter cathode arc deposition method to form a DLC transition layer;

[0056] A hydrogen-containing DLC layer is deposited on the surface of the DLC transition layer by a plasma enhanced chemical vapor deposition method to obtain the DLC self-lubricating thin film.

[0057] The steel substrate is preferably cleaned first. The present application does not have special requirements for the cleaning, and the wax and oil stains on the substrate can be cleaned. In the embodiments of the present application, the cleaning is specifically divided into two steps: ① 3-6 wt% of oil removal powder is added to the cleaning tank, and the cleaning solution (industrial pure water as the solvent of the cleaning solution) is ultrasonically cleaned at 60°C for 60-300 s to remove the wax and oil protective film on the surface of the substrate; ② 3-8% of the volume of the rust inhibitor and industrial pure water (>Ⅳ grade) are added to the cleaning tank, and ultrasonic cleaning is performed at 30°C and 60°C for 30-200 s to further remove the residual cleaning agent on the surface of the substrate and achieve the surface rust prevention effect.

[0058] After the steel base is cleaned, the steel base is preferably dried in the present application. The drying process in the present application has no special requirements, and the water on the surface of the steel base can be dried. In the embodiment of the present application, the surface cleaned steel base is placed for water dripping, compressed air drying (30-120s), and then constant temperature drying at 80-85℃ for 150-300s. If there is still water on the surface of the steel base, the steel base can be re-washed with pure water or anhydrous ethanol, and then the drying process is repeated.

[0059] The present application adopts a composite multifunctional ion plating film equipment to prepare a DLC self-lubricating film. The composite multifunctional ion plating film equipment mainly comprises a vacuum chamber, two cathode arc ion injection sources, an ion source power supply, a heating source, a rotating unit, a gas inlet unit, a molecular pump, and a pulse bias power supply, etc. The rotating frame and the graphite cathode in the furnace cavity are respectively supplied with direct current power and radio frequency power. The direct current power and the radio frequency power can replace the connected element target. The vacuum chamber is provided with a base mounting frame (as shown in Figure 1 ) which can revolve around the sun and rotate by itself.

[0060] Before preparing the DLC film, the present application installs a Cr target and a graphite target on the cathode arc ion injection source, respectively, and installs the base on a special hanger. The hanger structure is as shown in Figure 1 .

[0061] The present application uses a magnetic filtering cathode arc deposition method to inject Cr ions on the surface of the steel base to form an ion injection Cr layer.

[0062] Before injecting the Cr ions on the surface of the steel base, the present application preferably further comprises argon ion sputtering cleaning of the steel base. Specifically, the cleaned and dried steel base is placed on the hanger in the vacuum chamber, vacuumized, and the sputtering cleaning equipment is started to perform argon ion sputtering cleaning of the steel base.

[0063] In the present application, the argon ion sputtering cleaning process parameters preferably comprise: after the base vacuum is lower than 1.0×10 -3 Pa, argon gas is filled into the vacuum chamber, the argon gas flow is controlled at 15sccm, the gate valve is controlled to adjust the vacuum air pressure to 1.0×10 -1 Pa, the radio frequency sputtering cleaning equipment is started to perform argon ion sputtering cleaning, the target table bias voltage amplitude is -2kV, the bias voltage pulse width is 80μs, the pulse frequency is 75Hz, the radio frequency power is 200W, and the processing time is 40min.

[0064] The present application performs argon ion sputtering cleaning of the steel base, and the argon ions generated by high-voltage discharge ionization can further remove the dirt and oxidation layer on the surface of the hanger and the steel base.

[0065] In the present application, the preparation conditions of the ion-implanted Cr layer preferably include: taking a Cr target as cathode, the working pressure of Cr ion implantation being 3.0x10 -1 ~6.0x10 -1 Pa, the main arc voltage being 40~80V, the main arc pulse width being 200~500μs, the bias voltage amplitude being 15~25kV, the bias pulse frequency and the main arc pulse frequency being independently 75~90Hz, and the implantation time being 0.5~1h. Further, the working pressure of Cr ion implantation is preferably 4.0x10 -1 ~5.0x10 -1 Pa, the main arc voltage is preferably 50~70V, the main arc pulse width is preferably 300~400μs, the bias voltage amplitude is preferably 18~22kV, the bias pulse frequency and the main arc pulse frequency are preferably independently 80~85Hz, and the implantation time is preferably 40~50min.

[0066] In the present application, a 90° magnetic filtering elbow is preferably used for filtering large particles.

[0067] After forming the ion-implanted Cr layer, the present application uses a magnetic filtering cathodic arc deposition method to sequentially deposit a high-SP 2 valence bond structure DLC film and a high-SP 3 valence bond structure DLC film on the surface of the ion-implanted Cr layer, forming a DLC transition layer.

[0068] In the present application, the deposition conditions of the high-SP 2 valence bond structure DLC film preferably include: taking a graphite target as cathode, setting the substrate direct current bias voltage to be 1600~2000V; the cathodic arc source current being 40~60A; the high-voltage power supply for growing the single-layer high-SP 2 valence bond structure DLC film being in a sine wave mode, specifically, the frequency being 3~6Hz, the duty cycle being 40~60%, the peak height being 500~600V, and the peak valley being 400~450V; the multi-stage excitation coil voltage being set to be 4V~60V; and the deposition time of the single-layer high-SP 2 valence bond structure DLC film being 120~200s. Further, the substrate direct current bias voltage is 1700~1800V; the cathodic arc source current is more preferably 50A; the high-voltage power supply for growing the single-layer high-SP 2 valence bond structure DLC film is in a sine wave mode, the frequency being more preferably 5Hz, the duty cycle being more preferably 50%, the peak height being more preferably 550V, and the peak valley being more preferably 420V; the multi-stage excitation coil voltage being more preferably set to be 10~50V; and the deposition time of the single-layer high-SP 2 valence bond structure DLC film being more preferably 140~180s. In the present application, when the high-SP 2When the DLC film of covalent structure comprises multiple layers, the present application preferably adopts intermittent growth, and the intermittent time is preferably 30 s.

[0069] In the present application, the high SP 3 The deposition conditions of the DLC film of covalent structure preferably include: the substrate direct current bias is adjusted to 1800-2200 V, the parameters of the cathode arc source and the excitation coil are kept stable (i.e. the cathode arc source current is kept at 40-60 A; the working waveform of the high voltage power supply is in a sine wave mode, the frequency is 3-6 Hz, the duty cycle is 40-60%, the peak height is 500-600 V, and the peak-to-valley value is 400-450 V; the multi-stage excitation coil voltage is set to 4-60 V), and after deposition for 25-30 min, the substrate direct current bias is adjusted to 1400-1700 V, the cathode arc source current is increased to 50-70 A, and the other power supply parameters are kept unchanged, and the deposition is continued for 60-120 min. As a further preferred scheme, the substrate direct current bias is adjusted to 1900-2100 V, the parameters of the cathode arc source and the excitation coil are kept stable, and after deposition for 25-30 min, the substrate direct current bias is adjusted to 1500-1600 V, the cathode arc source current is increased to 55-65 A, and the other power supply parameters are kept unchanged, and the deposition is continued for 80-100 min.

[0070] After the DLC transition layer is formed, the present application uses the plasma enhanced chemical vapor deposition method to deposit a hydrogen-containing DLC layer on the surface of the DLC transition layer, to obtain the DLC self-lubricating thin film.

[0071] In the present application, the deposition conditions of the hydrogen-containing DLC layer preferably include: the vacuum chamber background temperature is 100°C, the substrate direct current bias is -800 to -1200 V, the duty cycle is 50%, the Ar flow rate is 10-20 sccm, the C2H2 flow rate is 110-130 sccm, the vacuum degree in the vacuum chamber is controlled to be 0.8-1.2 Pa, the ion source voltage is 1200-1600 V, the duty cycle is 50%, and the deposition time is 6-8 h. As a further preferred scheme, the substrate direct current bias is more preferably -900 to -1100 V, the C2H2 flow rate is more preferably 115-125 sccm, the vacuum degree in the vacuum chamber is more preferably controlled to be 0.9-1.1 Pa, and the ion source voltage is more preferably 1300-1500 V.

[0072] In the present application, during the preparation of the argon ion sputtering cleaning, the ion implanted Cr layer, the DLC transition layer and the hydrogen-containing DLC layer, the substrate mounting frame simultaneously performs revolution and rotation, so that the transition layer of the DLC thin film is more uniformly formed and grown, the revolution speed of the substrate mounting frame is preferably 0.5-2 rpm, more preferably 1-1.5 rpm, and the rotation speed is preferably 5-10 rpm, more preferably 6-8 rpm.

[0073] The present application aims at the inherent defects and application bottleneck of the diamond-like carbon film, uses the composite magnetic filter cathode arc deposition (FCVA) and the plasma enhanced chemical vapor deposition (PECVD) film coating technology, combines the material composition and the structure gradient, uses the method of adding transition layer film to improve the thermal stability of the material, improves the internal stress of the material, and improves the film base adhesion; and uses the solid-liquid composite lubrication technology, realizes the synergistic effect between the solid lubricating material and the liquid lubricating material, improves the lubricating effect, and improves the material friction and wear problem under extreme working conditions, which can prolong the bearing life by 3 times, improve the durability of the sliding friction surface by 75%, reduce the lubricating grease usage by 80%, reduce the maintenance frequency by 2 / 3, and realize the maintenance-free of the wind power bearing.

[0074] The DLC self-lubricating film and the preparation method thereof provided by the present application will be described in detail below in combination with examples, but they cannot be understood as the limitation of the protection scope of the present application.

[0075] Example 1

[0076] (1) Metal substrate cleaning. First, the GCr15 bearing steel is cleaned by removing wax and oil, and the specific process is as follows: ① ultrasonic cleaning for removing wax and oil, 3wt% of oil removal powder (industrial pure water as cleaning solution solvent) is added to the cleaning tank, ultrasonic cleaning at 60℃ for 100s, which can remove the wax and oil protective film on the surface of the GCr15 bearing steel; ② cleaning and rust prevention, 5vol% of rust inhibitor and industrial pure water (>Ⅳ grade) are added to the cleaning tank, and ultrasonic cleaning is carried out at 30℃ and 60℃ for 100s respectively, which can further remove the residual cleaning agent on the surface of the GCr15 bearing steel and achieve the effect of surface rust prevention and protection;

[0077] (2) Metal substrate drying and rust prevention. The GCr15 bearing steel cleaned in step (1) is dried, and the specific process is as follows: after the GCr15 bearing steel cleaned and rusted is placed and drained, compressed air is used for drying (time 60s), and then constant temperature drying is carried out at 82℃ for 200s. If there is still water stain that is difficult to remove after constant temperature drying, the GCr15 bearing steel can be re-flushed with pure water or anhydrous ethanol, and then the drying and drying operation is repeated.

[0078] (3) Argon ion sputtering cleaning of metal substrate in the furnace. The GCr15 bearing steel cleaned and dried in step (2) is placed on the hanger in the vacuum chamber, and the argon ion sputtering cleaning equipment is started after the vacuum is extracted, and the specific sputtering cleaning process parameters are as follows: after the background vacuum is lower than 1.0×10 -3 Pa, argon gas is filled into the vacuum chamber, the argon gas flow is controlled at 15sccm, the vacuum air pressure is adjusted to the working air pressure of 1.0×10 -1Pa, the target table bias amplitude is -2 kV, the bias pulse width is 80 μs, the pulse frequency is 75 Hz, the radio frequency power is 200 W, and the processing time is 40 min;

[0079] (4) Metal substrate ion implantation Cr layer preparation. The GCr15 bearing steel after sputter cleaning in step (3) is subjected to Cr ion implantation to form an ion implanted Cr layer. The Cr plasma is generated by a 99.99% purity cast chromium cathode through a pulsed cathode arc source (90° magnetic filtering elbow for large particle filtering). The Cr ion implantation working pressure range is 4.0 x 10 -1 -6.0 x 10 -1 Pa, the main arc voltage is 80 V, the main arc pulse width is 500 μs, the bias amplitude is 25 kV, the bias pulse frequency is the same as the main arc pulse frequency, which is 80 Hz, the processing time is 1 h, and the thickness of the ion implanted Cr layer formed is 0.58 μm;

[0080] (5) DLC transition layer preparation. The GCr15 bearing steel after ion implantation in step (4) is subjected to DLC transition layer film preparation. The specific process is as follows: adjust the substrate direct current bias to 1600 V (duty cycle is 80%), use a high-purity graphite target (≥99.999%) as the cathode, ① form a high-SP 2 valence structure DLC film by using graphite target ion implantation and deposition. The process sets the cathode arc source current to 50 A, the working waveform to a sine wave mode (frequency is 5 Hz, duty cycle is 50%, peak is 560 V, and valley is 420 V), the multi-stage excitation coil voltage to 4 V-60 V (multi-stage excitation coil is three on each graphite cathode target, each can adjust the voltage parameter arbitrarily, in order to achieve good elbow magnetic filtering effect, the three coil voltages on the same cathode are set to different values), and the high-SP 2 valence structure DLC film is grown in an intermittent manner. Each layer is 40 nm thick, the total thickness is about 240 nm, the deposition time of a single layer of high-SP 2 valence structure DLC film is 150 s, and the next layer is grown after 30 s of stop; ② prepare a high-SP 2 valence structure DLC film on the surface of the formed high-SP 3 valence structure DLC film, increase the substrate direct current bias to 2000 V, keep the cathode arc and excitation coil parameters stable, deposit DLC film for 25 min, then adjust the substrate direct current bias to 1600 V, increase the cathode arc source current to 60 A, and keep other power parameters unchanged, deposit high-SP 3 valence structure DLC film for 60 min, the thickness of the high-SP 3 valence structure DLC film is 90 nm, and the thickness of the DLC transition layer is 0.33 μm.

[0081] (6) Hydrogen-containing DLC surface layer preparation. The high-SP 3 valence bond structure of the DLC film surface to prepare a hydrogen-containing DLC film, the specific process is as follows: set the vacuum chamber base temperature to 100°C, the substrate DC bias to -1000V (duty cycle 50%), control the Ar flow rate to 15sccm, the C2H2 flow rate to 110sccm, the vacuum degree in the vacuum chamber to 0.8-1.2Pa, the ion source voltage to 1400V (duty cycle 50%), the deposition time to 6h, and the deposition layer thickness to 1.0μm.

[0082] (7) In the film preparation steps (1)-(6), the GCr15 bearing steel target table mounting bracket can simultaneously perform revolution and rotation, so that the transition layer of the DLC film can be more uniformly formed and grown. The bracket revolution speed is 0.5rpm, and the rotation speed is 5rpm.

[0083] Example 2

[0084] (1) Metal substrate cleaning. First, the GCr15 bearing steel is cleaned to remove wax and oil, and the specific process is as follows: ① ultrasonic cleaning to remove wax and oil, add 5wt% oil removal powder (using industrial pure water as the solvent of the cleaning solution) to the cleaning tank, ultrasonic cleaning at 60°C for 200s to remove the wax and oil protective film on the surface of the GCr15 bearing steel; ② cleaning and rust prevention, add 6vol% rust inhibitor and industrial pure water (>Ⅳ grade) to the cleaning tank, ultrasonic cleaning at 30°C and 60°C for 120s respectively to further remove the residual cleaning agent on the surface of the GCr15 bearing steel and achieve the surface rust prevention effect;

[0085] (2) Metal substrate drying and rust prevention. The GCr15 bearing steel cleaned in step (1) is subjected to drying treatment, and the specific process is as follows: after the surface cleaned and rusted GCr15 bearing steel is allowed to stand and drain, compressed air is used for drying (time 80s), and then the GCr15 bearing steel is dried at 85°C for 200s. If there are still water stains that are difficult to remove after constant temperature drying, the GCr15 bearing steel can be re-flushed with pure water or anhydrous ethanol, and then the drying and baking operations are repeated.

[0086] (3) Metal substrate in-furnace argon ion sputtering cleaning. The GCr15 bearing steel cleaned and dried in step (2) is placed on the hanger in the vacuum chamber, vacuum is drawn, and the argon ion sputtering cleaning equipment is started to clean the GCr15 bearing steel by argon ion sputtering. The specific sputtering cleaning process parameters are as follows: after the base vacuum is lower than 1.0×10 -3 Pa, argon gas is filled into the vacuum chamber, the argon gas flow rate is controlled to 15sccm, the vacuum air pressure is adjusted to the working air pressure of 1.0×10 -1Pa, the target table bias amplitude is -2kV, the bias pulse width is 80μs, the pulse frequency is 75Hz, the radio frequency power is 200W, and the processing time is 40min;

[0087] (4) Metal substrate ion implantation Cr layer preparation. The GCr15 bearing steel after sputtering cleaning in step (3) is subjected to Cr ion implantation to form an ion implanted Cr layer. The Cr plasma is generated by a 99.99% purity cast chromium cathode through a pulsed cathode arc source (90° magnetic filtering elbow for large particle filtering). The Cr ion implantation working pressure range is 4.0x10 -1 -6.0x10 -1 Pa, the main arc voltage is 60V, the main arc pulse width is 300μs, the bias amplitude is 20kV, the bias pulse frequency is the same as the main arc pulse frequency, which is 80Hz, the processing time is 0.5h, and the thickness of the formed Cr ion primer layer is 0.4μm;

[0088] (5) DLC transition layer preparation. The GCr15 bearing steel after ion implantation in step (4) is subjected to DLC transition layer film preparation, and the specific process is as follows: adjusting the substrate direct current bias to 1800V (duty cycle is 80%), using a high-purity graphite target with purity ≥99.999% as the cathode, ① forming a high-SP 2 valence structure DLC film by using graphite target ion implantation and deposition. The process sets the cathode arc source current to 50A, the working waveform to sine wave mode (frequency is 5Hz, duty cycle is 50%, peak is 560V, valley is 420V), the multi-stage excitation coil voltage to 4V-60V, and the high-SP 2 valence structure DLC film is grown intermittently for 5 layers, each layer has a thickness of 50nm, the total thickness is about 250nm, the single layer deposition time is 180s, and the next layer is grown after stopping for 30s; ② high-SP 2 valence structure DLC film is prepared on the surface of the high-SP 3 valence structure DLC film. The substrate direct current bias is adjusted to 2000V, the cathode arc source and the excitation coil parameters are kept stable, the DLC film is deposited for 25min, the substrate direct current bias is adjusted to 1600V, the cathode arc source current is increased to 60A, and the other power parameters remain unchanged, the DLC film is deposited for 100min, and the thickness of the high-SP 3 valence structure DLC film is 130nm, and the thickness of the DLC transition layer is 0.38μm.

[0089] (6) Hydrogen-containing DLC surface layer preparation. The high-SP 3The preparation of hydrogen-containing DLC ​​films on the surface of DLC films with valence bond structures is carried out as follows: the background temperature of the vacuum chamber is set to 100℃, the DC bias voltage of the substrate is -1000V (duty cycle is 50%), the Ar flow rate is controlled at 15sccm, the C2H2 flow rate is controlled at 120sccm, the vacuum degree in the vacuum chamber is controlled at 0.8~1.2Pa, the ion source voltage is 1400V (duty cycle is 50%), the DLC film deposition time is 7h, and the deposition layer thickness is 1.2μm.

[0090] (7) In the thin film preparation steps (1) to (6), the GCr15 bearing steel target stage mounting bracket can simultaneously revolve and rotate, so that the transition layer of the DLC thin film can be grown more uniformly. The bracket revolve at a speed of 0.5 rpm and rotate at a speed of 5 rpm.

[0091] Comparative Example 1

[0092] The only difference from Example 1 is that step (5) of preparing the DLC transition layer is omitted.

[0093] Performance characterization:

[0094] Figure 3 The friction coefficient curves of the DLC self-lubricating film of Example 1 and Comparative Example 1 of this invention when combined with conventional low-viscosity grease are shown (using a CSM friction testing machine, the friction ball material is GCr15, the loading force is 20N, the sliding frequency is 3Hz, the stroke is 8mm, the friction time is 30min, and low-viscosity grease is added to the friction surface before the friction test). Figure 3 It can be seen that the friction coefficient of the DLC self-lubricating film without the DLC transition layer increases after 1100s of wear. This is because the hydrogen-containing DLC ​​film detaches. The DLC transition layer effectively enhances the bonding ability of the hydrogen-containing DLC ​​layer and has stronger wear resistance.

[0095] Figure 4 The images show the wear track profiles of the DLC self-lubricating films of Example 1 and Comparative Example 1 after friction and wear tests against conventional high-viscosity and low-viscosity grease composite lubrication systems. Specifically, a fully automated true-color confocal microscope was used to observe and measure the specimens after the friction and wear tests, and the wear track profiles were plotted. Observation of the wear track profiles reveals that the DLC self-lubricating film without a DLC transition layer exhibits a larger wear volume due to its higher coefficient of friction, while the DLC self-lubricating film with a DLC transition layer has a smaller wear volume and superior wear resistance.

[0096] Figure 5The surface images and scratch curves (using a scratch tester to test the surface of the composite DLC film, load is 0-30N, scratch length is 4mm) of the nanogradient composite DLC self-lubricating film of Example 1 and Comparative Example 1 after scratch test are shown in Figure 1. Figure 5 It can be seen that the critical load (Lc3) corresponding to the delamination of the coating and the substrate of Example 1 and Comparative Example 1 is 26.04N and 17.63N respectively, indicating that the DLC transition layer can enhance the adhesion of the hydrogen-containing DLC film and thus increase the failure force value.

[0097] The DLC film of Example 1 was subjected to high-temperature annealing treatment in an atmospheric environment using a box-type resistance furnace to study the effect of environmental temperature on the thermal stability of the DLC film. The annealing treatment was carried out at 200℃ in an atmospheric environment, and after reaching the set temperature, the temperature was maintained for 1h, and then the furnace was cooled to room temperature. The LabRAM HR800 laser confocal Raman spectrometer was used to analyze the Raman spectrum of the DLC film before and after annealing, and the changes of the surface SP 2 or SP 3 values were analyzed, and the results are shown in Figure 6 . As shown in Figure 6 , the A D / A G values before and after heat treatment were 0.606 and 0.614 respectively, with a small change before and after, proving that the DLC film layer has good thermal stability.

[0098] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A DLC self-lubricating film, characterized by, The DLC self-lubricating film comprises a steel substrate and a DLC self-lubricating film attached to the steel substrate, wherein the DLC self-lubricating film comprises, in sequence, an ion-implanted Cr layer, a DLC transition layer and a hydrogen-containing DLC layer attached to the steel substrate; Cr ions in the ion-implanted Cr layer exist in the form of C2Cr3; The DLC transition layer is formed of high SP 3 valence-bond structured DLC film and a plurality of layers of high SP 2 valence-bond structured DLC films are sequentially laminated; the high SP 2 valence-bond structured DLC film is in contact with an ion-implanted Cr layer, the high SP 3 valence-bond structured DLC film is in contact with a hydrogen-containing DLC layer; said high SP 3 content of sp3 3 content of sp3 2 content of sp3 2 content of sp3 2 content of sp3 3 content of sp3; the content of sp3 2 content of sp3 3 content of sp3 The high SP 3 The thickness of the sp3bonded DLC film is 50 to 250 nm. The high-SP 2 The total thickness of the DLC film of the sp3 structure is 0.1 to 0.25 μm, and the thickness of the single layer of the high-SP 2 The thickness of the DLC film of the sp3 structure is 10 to 50 nm. The total thickness of the DLC transition layer is 0.2-0.5 μm; said high SP 3 content of sp3 3 content of sp3 2 content of sp3 2 content of sp3 2. The DLC self-lubricating film according to claim 1, wherein The thickness of the ion-implanted Cr layer is 0.4-0.6 μm.

3. The DLC self-lubricating film according to claim 1, wherein The thickness of the hydrogen-containing DLC layer is 0.7-1.3 μm.

4. The method of producing a DLC self-lubricating film according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: implanting Cr ions on the surface of the steel substrate by a magnetic filtering cathode arc deposition method to form an ion-implanted Cr layer; A high-SP 2 valence bond structure DLC film and a high-SP 3 valence bond structure DLC film are sequentially deposited on the surface of the ion-implanted Cr layer to form a DLC transition layer. depositing a hydrogen-containing DLC layer on the surface of the DLC transition layer by a plasma enhanced chemical vapor deposition method to obtain the DLC self-lubricating film.

5. The preparation method according to claim 4, characterized in that, The preparation conditions of the ion-implanted Cr layer include: using a Cr target as a cathode, a working pressure of 3.0×10 -1 Pa, a main arc voltage of 40-80 V, a main arc pulse width of 200-500 μs, a bias voltage amplitude of 15-25 kV, a bias voltage pulse frequency independently of the main arc pulse frequency of 75-90 Hz, and an implantation time of 0.5-1 h. -1 ​ 6. The preparation method according to claim 4, characterized in that, The high SP 2 Deposition conditions of the DLC film with high SP 2 The working waveform of the high-voltage power supply for growing the DLC film with high SP 2 The deposition time of the DLC film with high SP The high SP 3 The deposition conditions of the sp3 bond structure DLC film include: adjusting the substrate direct current bias to 1800-2200 V, keeping the cathode arc source current at 40-60 A; the working waveform of the high-voltage power supply is a sine wave mode, the frequency is 3-6 Hz, the duty cycle is 40-60%, the peak height is 500-600 V, and the peak-to-valley value is 400-450 V; the multi-stage excitation coil voltage is set to 4-60 V; after depositing for 25-30 min, the substrate direct current bias is adjusted to 1400-1700 V, the cathode arc source current is increased to 50-70 A, and other power supply parameters remain unchanged, and the deposition is continued for 60-120 min.

7. The preparation method according to claim 4, characterized in that, The deposition conditions of the hydrogen-containing DLC layer comprise: a vacuum chamber base temperature of 100 ℃, a substrate direct current bias of -800 to -1200 V and a duty cycle of 50%, an Ar flow rate of 10-20 sccm, a C2H2 flow rate of 110-130 sccm, a vacuum degree in the vacuum chamber controlled at 0.8-1.2 Pa, an ion source voltage of 1200-1600 V and a duty cycle of 50%, and a deposition time of 6-8 h.

8. The preparation method according to claim 4, characterized in that, Before implanting Cr ions on the surface of the steel substrate, the method further comprises performing argon ion sputtering cleaning on the steel substrate.

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