Friction matching pair system, preparation method and method for realizing ultra-low friction of ultra-hard carbon film

Abstract

The invention relates to a friction matching pair system, a preparation method and a method for realizing ultra-low friction of an ultra-hard carbon film. The friction matching pair system comprises a superhard tetrahedron amorphous carbon film and a multi-element doped graphite-like carbon film which are coated on two contact surfaces of a friction pair respectively, and a nano solid lubricant located between friction interfaces, multi-element metals doped in the multi-element doped graphite-like carbon film are Ag, Ni and Cu, the total doping amount is 15 at%-25 at%, the general formula of the multi-element metals is AgxNiyCuz, and the sum of the total doping amount and the total doping amount is 15 at%-25 at%. Wherein 0 < x < = 4, 1 < = y < = 2, and 1 < = z < = 2. The invention aims to overcome the defects in the prior art, and stable and ultralow friction of the superhard ta-C carbon film is realized through the synergistic effect between the multi-metal doped amorphous carbon accessory spheres and the nano solid lubricant. The friction matching pair system and method are expected to solve the problems of large friction torque and short service life of mechanical moving parts in high-end equipment or precise instruments.

Description

Technical Field

[0001] This article relates to the fields of materials surface engineering and tribology, especially the method of achieving ultra-hard carbon films with ultra-low friction using multi-doped graphite carbon films and solid nano-lubricants. Background Technology

[0002] Tetrahedral amorphous carbon films (ta-C) have broad application prospects in mechanical seals, precision bearings, and cutting tools due to their extremely high hardness, excellent wear resistance, and good chemical inertness. However, under actual working conditions, especially under dry friction or insufficient lubrication, the coefficient of friction of superhard ta-C films is often high, resulting in large frictional torque and high energy consumption during component operation, and even premature component failure, which seriously limits the engineering application of superhard ta-C films. Currently, conventional methods to improve the tribological properties of ta-C films mainly include element doping, surface texturing, and the use of liquid lubricants. However, these methods have the following shortcomings: regardless of the choice of doping element, the wear resistance of the superhard ta-C film itself will be affected, and single-element doping often cannot simultaneously guarantee low friction and ultra-wear resistance; surface texturing is complex, costly, and may introduce stress concentration points; traditional liquid lubricants are prone to failure under vacuum, high temperature, and high pressure conditions, resulting in insufficient reliability.

[0003] Two-dimensional layered material MoS2 is considered an ideal solid lubricant due to its unique layered structure and low shear strength. However, MoS2, when used alone, suffers from poor oxidation resistance and weak adhesion to the substrate. On the other hand, in friction systems, the choice of mating materials has a decisive impact on the overall performance of the friction pair, but existing technologies lack mating systems for achieving ultra-low friction in ultrahard carbon films. Therefore, developing a mating system and its design method that can synergistically utilize the properties of mating materials and the advantages of solid nano-lubricants to achieve stable ultra-low friction and near-zero wear in ultrahard ta-C films has become a pressing technical problem in this field. Summary of the Invention

[0004] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of protection of this application.

[0005] The purpose of this application is to overcome the shortcomings of existing technologies and provide a method for designing mating pairs and systems to achieve low or even ultra-low friction in ultra-hard ta-C thin films. This is achieved through the synergistic effect between multi-metal-doped amorphous carbon dual spheres and nano-solid lubricants, forming a stable low-friction interface, thereby realizing ultra-low friction in ultra-hard ta-C carbon films. This friction mating system and method are expected to solve the problems of high frictional torque and short lifespan in mechanical moving parts of high-end equipment or precision instruments.

[0006] The first aspect of this application provides a multi-doped graphite carbon film, wherein the metals doped in the multi-doped graphite carbon film are Ag, Ni, and Cu.

[0007] In one exemplary embodiment, the total doping amount of Ag, Ni, and Cu in the multi-doped graphite carbon film is 15 at%-25 at%; for example, 15 at%-20 at% or 20 at%-15 at%.

[0008] In one exemplary embodiment, the multi-element doped graphite carbon film contains a multi-element metal of the general formula Ag. x Ni y Cu z , where 0 < x ≤ 4, 1 ≤ y ≤ 2, 1 ≤ z ≤ 2.

[0009] In one exemplary embodiment, the multi-element doped graphite carbon film contains a multi-element metal of the general formula Ag. x Ni y Cu z , where 1≤x≤4, 1≤y≤2, 1≤z≤2.

[0010] In one exemplary embodiment, the atomic percentages of Ag, Ni, and Cu in the multi-doped graphite carbon film are (0-4):(1-2):(1-2); preferably, they are (1-4):(1-2):(1-2).

[0011] In one exemplary embodiment, in the multi-element doped graphite carbon film, x=4, y=2, z=1, the general formula of the multi-element metal is Ag4Ni2Cu1, and the total doping amount of Ag, Ni, and Cu is 20 at%; or In the multi-component doped graphite carbon film, x=4, y=1, z=2, the general formula of the multi-component metal is Ag4Ni1Cu2, and the total doping amount of Ag, Ni and Cu is 25 at.

[0012] The second aspect of this application provides a friction pair system, which includes an ultrahard tetrahedral amorphous carbon film and a multi-doped graphite-like carbon film coated on the two contact surfaces of the friction pair, and a nano-solid lubricant located between the friction interfaces.

[0013] In one exemplary embodiment, the nano-solid lubricant is a dispersion of MoS2.

[0014] In one exemplary embodiment, the material of the friction pair is selected from one or more of bearing steel, high-temperature alloy steel, stainless steel, and titanium alloy steel.

[0015] In one exemplary embodiment, the friction pair may be a static friction pair or a dynamic friction pair; for example, a rolling friction pair or a sliding friction pair.

[0016] In one exemplary embodiment, the friction pair is a ball-disc contact friction pair, a point contact friction pair, a pin-disc friction pair, a ring-block friction pair, a ring-ring (double ring) friction pair, a ball-column friction pair, or a disc-disc friction pair, etc.

[0017] In one exemplary embodiment, the friction pair is a ball-disc contact friction pair.

[0018] In one exemplary embodiment, the superhard tetrahedral amorphous carbon film is deposited on the disk side of the ball-disc friction pair, and the multi-doped graphite carbon film is deposited on the ball side of the ball-disc friction pair.

[0019] In one exemplary embodiment, in the superhard tetrahedral amorphous carbon film, sp 3 The C content is 60%-80%; for example, 60%-65%, 65%-68%, 68%-70%, 70%-72%, 72%-75%, 75%-80%.

[0020] In one exemplary embodiment, the hardness of the superhard tetrahedral amorphous carbon film is 35-45 GPa.

[0021] In one exemplary embodiment, in the superhard tetrahedral amorphous carbon film, sp 3 The carbon content is 65%, and the hardness is 39 GPa.

[0022] In one exemplary embodiment, the superhard tetrahedral amorphous carbon film is prepared by high-power magnetron sputtering technology, and the thickness of the working layer is 500-800 nm; preferably, the thickness of the working layer is 620 nm.

[0023] In one exemplary embodiment, the superhard tetrahedral amorphous carbon film may further include a transition layer located on the surface of the substrate, and the working layer is deposited on the transition layer.

[0024] In one exemplary embodiment, the concentration of MoS2 in the nano-solid lubricant is 0.05-0.15 mg / mL, and the solvent is anhydrous ethanol; preferably, the concentration of MoS2 is 0.1 mg / mL.

[0025] In one exemplary embodiment, the MoS2 in the nano-solid lubricant is a two-dimensional nanostructure with a sheet diameter of 0.02-1.00 μm, 3-10 layers, and a thickness of 1-8 nm.

[0026] A third aspect of this application provides a method for preparing the above-mentioned friction pair system, comprising the following steps: 1) Coating the disk side of the ball-disc friction pair with an ultrahard tetrahedral amorphous carbon film; 2) Coating a multi-element doped graphite-carbon film onto the spherical side of the ball-disc friction pair; 3) Add nano solid lubricant to the surface of the disk side described in step 1) to obtain the friction pair system.

[0027] In one exemplary embodiment, step 3) includes: repeatedly dripping the nano-solid lubricant at the same position on the disk side surface, and drying it after each dripping.

[0028] In one exemplary embodiment, in step 3), the amount of liquid added is 3-10 μL / time; preferably, it is 5 μL / time.

[0029] In one exemplary embodiment, in step 3), the number of drops is 8-12, preferably 10.

[0030] In one exemplary embodiment, in step 3), the drying temperature is 40-60°C and the drying time is 5-15 minutes; preferably, the drying temperature is 45°C and the drying time is 10 minutes.

[0031] The fourth aspect of this application provides a method for achieving ultra-low friction of an ultrahard carbon film using the above-mentioned friction pair system, comprising: applying the friction pair system to mechanical moving parts in high-end equipment or precision instruments to achieve friction reduction and wear resistance under atmospheric conditions of relative humidity of 12±8% and under conditions of load of 1~10 N, frequency of 1~5 Hz and amplitude of 4~8 mm. Preferably, the conditions for achieving ultra-low friction of the ultrahard carbon film are: in an atmospheric environment with a relative humidity of 12±8%, a load of 1 N, a frequency of 5 Hz, and an amplitude of 4 mm.

[0032] Compared with existing related technologies, this application has the following technical effects: 1. In the friction pair system of this application, the high hardness and high sp2 of the superhard tetrahedral amorphous carbon film... 3 The C content ensures its near-zero wear characteristics, providing a guarantee for the formation of a stable low-friction transfer film in the friction pair system.

[0033] 2. A certain proportion of Ag is plated onto the spherical side (e.g., the paired spheres) of the ball-disc friction pair. x Ni y Cu zIn multi-component doped graphite carbon films, soft metal Ag can be precipitated during friction and provide a self-lubricating effect; catalytic Ni and Cu multi-component metals can enhance the lubricity of amorphous carbon in the ligand spheres. The composite doping of the three (total doping amount 15-25 at%) achieves an optimized combination of soft lubricating phase and catalytic phase.

[0034] 3. This application first designs and assembles a “superhard tetrahedral amorphous carbon film Vs Ag”. x Ni y Cu z Tribological pairings of "multi-doped graphite-like carbon films" were studied. A ball-disc tribological testing machine was selected for the tribological tests. Before friction, a two-dimensional nano-MoS2 dispersion was added dropwise to the friction interface. Under an air environment with a relative humidity of 12±8%, the load was set to 1 N, the frequency to 5 Hz, the amplitude to 4 mm, and the reciprocating cycle to 4500 revolutions. Different Ag values ​​were tested. x Ni y Cu z Tribological properties of a novel friction pair composed of metal-doped amorphous carbon dual spheres. Test results show that this application achieves a robust ultra-low friction state for an ultrahard tetrahedral amorphous carbon film, with a friction coefficient close to 0.01 and Ag... x Ni y Cu z The composite metal and the surface MoS2 lubricant work synergistically during friction to form a low-shear composite transfer film with MoS2 as the framework and embedded multi-lubricating phases (C, Ag, Ni, Cu). This film system combines low-shear performance in atmospheric environments with long-term anti-wear capabilities, which is key to improving the lubrication performance of ultrahard tetrahedral amorphous carbon films in low-humidity atmospheric environments. Simultaneously, due to the extremely low wear rate of the ultrahard tetrahedral amorphous carbon film, and the fact that the metal elements in the dual spheres can couple with the added MoS2 nano-lubricant to continuously replenish the transfer film, a stable ultra-low friction state is maintained.

[0035] 4. This application can achieve ultra-low friction of superhard tetrahedral amorphous carbon film without complex modifications to existing equipment, and has the characteristics of low cost and easy industrialization.

[0036] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the application. Other advantages of this application can be realized and obtained by means of the embodiments described in the description and the accompanying drawings. Attached Figure Description

[0037] The accompanying drawings are used to provide an understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0038] Figure 1 For the purposes of this application, “Superhard Tetrahedral Amorphous Carbon Film Vs Ag” x Ni y Cu z A schematic diagram of the friction pair system of "multi-doped graphite carbon film" and nano solid lubricant; Figures 2 to 3 The friction coefficient curves are for the friction pair systems in the embodiments and comparative examples of this application.

[0039] Explanation of reference numerals in the attached figures: 1—Substrate of ultrahard tetrahedral amorphous carbon film; 2—Dual spheres of multi-element doped graphite carbon film; 3—Nano-solid lubricant. Detailed Implementation

[0040] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this invention.

[0041] The raw materials used in this application are all conventional products on the market.

[0042] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0043] Experimental methods not specified in the examples are generally performed under standard conditions or as recommended by the manufacturer.

[0044] Example 1 like Figure 1 As shown, in the friction pair system: High-power magnetron sputtering technology was employed, and an ultrahard tetrahedral amorphous carbon film with a working layer thickness of 620 nm was selected as the disk-side fixed friction plane in the ball-disk friction pair. The ultrahard tetrahedral amorphous carbon film has a hardness of 39 GPa. 3 With a carbon content of 65%, these characteristics ensure the near-zero wear properties of the superhard tetrahedral amorphous carbon film, providing a guarantee for the formation of a stable low-friction transfer film in the friction pair system. A multi-element doped graphite carbon film of Ag4Ni2Cu1 was selected as the dual spheres coated on the surface of GCr15 steel sphere substrate, wherein the total doping of Ag, Ni and Cu is 20 at%, realizing the optimized combination of soft lubricating phase and hard bearing phase. In the nano-solid lubricant, the concentration of MoS2 is 0.1 mg / mL, the solvent is anhydrous ethanol, the addition amount is 5 μL / time, and a total of 10 times. After each addition, it is dried at 45℃ for 10 minutes. The two-dimensional MoS2 nano-solid lubricant has a sheet diameter of 0.02-1.00 μm, 3-10 layers, and a thickness of 1-8 nm.

[0045] Tribological performance testing: A ball-disc friction testing machine was selected. Before friction, a nano-solid lubricant was added dropwise to the friction interface. Under conditions of 12±5% relative humidity, a load of 1 N, a frequency of 5 Hz, an amplitude of 4 mm, and a reciprocating cycle of 4500 revolutions were set. The minimum coefficient of friction measured in the above system was 0.0015 (see...). Figure 2 ).

[0046] Example 2 like Figure 1 As shown, in the friction pair system: The same superhard tetrahedral amorphous carbon film as in Example 1 was selected as the disk-side fixed friction plane in the ball-disc friction pair. A multi-element doped graphite-carbon film, Ag4Ni1Cu2, was selected as the dual sphere coating on the surface of a GCr15 steel sphere substrate, wherein the total doping content of Ag, Ni, and Cu was 25 at%; The same nano-solid lubricant as in Example 1 was selected.

[0047] Tribological performance testing: A ball-disc friction testing machine was selected. Before friction, a nano-solid lubricant was added dropwise to the friction interface. Under conditions of 12±5% relative humidity, a load of 1 N, a frequency of 5 Hz, an amplitude of 4 mm, and a reciprocating cycle of 4500 revolutions were set. The minimum coefficient of friction measured in the above system was 0.021 (see...). Figure 2 ).

[0048] Comparative Example 1 In the aforementioned friction pair system: The same superhard tetrahedral amorphous carbon film as in Example 1 was selected as the disk-side fixed friction plane in the ball-disc friction pair. Bare steel balls without carbon coating on the surface of GCr15 steel balls were selected as the dual balls; In the nano-solid lubricant, the concentration of MoS2 is 0.1 mg / mL, the solvent is anhydrous ethanol, the addition amount is 5 μL / time, and a total of 10 times. After each addition, it is dried at 45℃ for 10 minutes. The MoS2 nano-solid lubricant has a sheet diameter of 0.02-1.00 μm, 3-10 layers, and a thickness of 1-8 nm.

[0049] Tribological performance testing: A ball-disc friction testing machine was selected. Before friction, a nano-solid lubricant was applied to the side surface of the mating disc. Under conditions of 12±5% relative humidity, a load of 1 N, a frequency of 5 Hz, an amplitude of 4 mm, and a reciprocating cycle of 4500 revolutions were set. The minimum coefficient of friction measured in the above system was 0.09 (see...). Figure 2 ).

[0050] Comparative Example 2 The same superhard tetrahedral amorphous carbon film as in Example 1 was selected as the disk-side fixed friction plane in the ball-disc friction pair. A multi-element doped graphite-carbon film of Ag4Ni0Cu0 was selected and coated on the surface of a GCr15 steel sphere substrate as the dual sphere, wherein the total Ag doping content was 23 at% The same nano-solid lubricant as in Example 1 was selected.

[0051] Tribological performance testing: A ball-disc friction testing machine was selected. Before friction, a nano-solid lubricant was added dropwise to the friction interface. Under conditions of 12±5% relative humidity, a load of 1 N, a frequency of 5 Hz, an amplitude of 4 mm, and a reciprocating cycle of 4500 revolutions were set. The minimum coefficient of friction measured in the above system was 0.08 (see...). Figure 2 ).

[0052] Comparative Example 3 In the aforementioned friction pair system: High-power magnetron sputtering technology was employed, and an ultrahard tetrahedral amorphous carbon film with a working layer thickness of 620 nm was selected as the disk-side fixed friction plane in the ball-disk friction pair. The ultrahard tetrahedral amorphous carbon film has a hardness of 39 GPa. 3 With a carbon content of 65%, these characteristics ensure the near-zero wear properties of the ultrahard tetrahedral amorphous carbon film, providing a guarantee for the formation of a stable low-friction transfer film. By selecting a graphite carbon film coated with Ag0Ni0Cu0 or without Ag, Ni, and Cu doping on the surface of a GCr15 steel ball substrate as a dual ball, an optimized combination of soft lubricating phase and hard load-bearing phase was achieved. This system does not contain nano-lubricants.

[0053] Tribological performance testing: A ball-disc friction testing machine was selected, and in an air environment with a relative humidity of 12±5%, the load was set to 1 N, the frequency to 5 Hz, the amplitude to 4 mm, and the reciprocating cycle to 4500 revolutions. The minimum coefficient of friction measured in the above system was 0.21 (see...). Figure 3 ).

[0054] Comparative Example 4 The same superhard tetrahedral amorphous carbon film as in Example 1 was selected as the disk-side fixed friction plane in the ball-disc friction pair. A graphite-carbon pair of Ag4Ni0Cu0 type was selected as the dual spheres coated on the surface of GCr15 steel sphere substrate, wherein the total Ag doping content was 9.36 at%; The same nano-lubricant as in Example 1 was selected.

[0055] Tribological performance testing: A ball-disc friction testing machine was selected, and in an air environment with a relative humidity of 12±5%, the load was set to 1 N, the frequency to 5 Hz, the amplitude to 4 mm, and the reciprocating cycle to 4500 revolutions. The minimum coefficient of friction measured in the above system was 0.20 (see...). Figure 3 ).

[0056] Comparative Example 5 In the aforementioned friction pair system: The same superhard tetrahedral amorphous carbon film as in Example 1 was selected as the disk-side fixed friction plane in the ball-disc friction pair. A multi-component doped graphite-carbon film, Ag4Ni2Cu1, was selected as the dual sphere coating on the surface of GCr15 steel spheres, with a total doping content of Ag, Ni, and Cu of 22.83 at%; No lubricant.

[0057] Tribological performance testing: A ball-disc friction testing machine was selected, and in an air environment with a relative humidity of 12±5%, the load was set to 1 N, the frequency to 5 Hz, the amplitude to 4 mm, and the reciprocating cycle to 4500 revolutions. The minimum coefficient of friction measured in the above system was 0.15 (see...). Figure 3 ).

[0058] Comparative Example 6 The same superhard tetrahedral amorphous carbon film as in Example 1 was selected as the disk-side fixed friction plane in the ball-disc friction pair. A multi-element doped graphite carbon, consisting of Ag4Ni1Cu2, was selected as the dual spheres and coated on the surface of a GCr15 steel sphere substrate. The total doping amount of Ag, Ni, and Cu was 27.67 at.

[0059] No lubricant.

[0060] Tribological performance testing: A ball-disc friction testing machine was selected, and in an air environment with a relative humidity of 12±5%, the load was set to 1 N, the frequency to 5 Hz, the amplitude to 4 mm, and the reciprocating cycle to 4500 revolutions. The minimum coefficient of friction measured in the above system was 0.13 (see...). Figure 3 ).

[0061] like Figures 2 to 3 As shown, when multi-metal-doped graphite-carbon sphere films coated with Ag4Ni1Cu2 and Ag4Ni2Cu1 are selected as the dual spheres, the tribological properties of the friction pair system are superior. Meanwhile, the break-in period in Example 1 is shorter, achieving a robust ultra-low friction state. In Example 2, the tribological properties in the steady-state stage are better, but the break-in period is longer than in Example 1.

[0062] In summary, 1) in the friction pair system of this application, the high hardness and high sp of the superhard tetrahedral amorphous carbon film... 3 The C content ensures its near-zero wear characteristics, providing a guarantee for the formation of a stable low-friction transfer film in the friction pair system. 2) A certain proportion of Ag is plated on the spherical side (e.g., the paired spheres) of the ball-disc friction pair. x Ni y Cu z In multi-component doped graphite carbon films, soft metal Ag can precipitate during friction and provide a self-lubricating effect; catalytic Ni and Cu multi-component metals can enhance the lubricity of amorphous carbon in the ligand spheres. The composite doping of these three (total doping amount 15-25 at%) achieves an optimized combination of soft lubricating phase and catalytic phase. 3) This application first designs and assembles "superhard tetrahedral amorphous carbon film Vs Ag". x Ni y Cu z The tribological pair of "multi-doped graphite-like carbon film" was studied. A ball-disc tribological testing machine was selected for the tribological test. Before friction, a two-dimensional nano-MoS2 dispersion was added dropwise to the friction interface. Under an air environment with a relative humidity of 12±8%, the load was set to 1 N, the frequency to 5 Hz, the amplitude to 4 mm, and the reciprocating cycle to 4500 revolutions. Ag was tested. x Ni y Cu z Tribological properties of a novel friction pair composed of composite metal-doped amorphous carbon films as dual spheres. Test results show that this application achieves a robust ultra-low friction state with an ultrahard tetrahedral amorphous carbon film, with a friction coefficient close to 0.01. x Ni y Cu zThe composite metal and the surface MoS2 lubricant work synergistically during friction to form a low-shear composite transfer film with MoS2 as the framework and embedded multi-lubricating phases (C, Ag, Ni, Cu). This film system combines low shear and long-term anti-wear capabilities in atmospheric environments, which is key to improving the lubrication performance of superhard tetrahedral amorphous carbon films under low humidity and light load atmospheric conditions. Simultaneously, due to the extremely low wear rate of the superhard tetrahedral amorphous carbon film, and the fact that the metal elements in the dual spheres can couple with the added MoS2 nano-solid lubricant to continuously replenish the transfer film, a stable ultra-low friction state is ensured for a long time. 4) This application achieves ultra-low friction of superhard tetrahedral amorphous carbon films without complex modifications to existing equipment, and is characterized by low cost and ease of industrialization.

[0063] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A friction pair system, the friction pair system comprising an ultrahard tetrahedral amorphous carbon film and a multi-doped graphite-like carbon film coated on two contact surfaces of the friction pair respectively, and a nano-solid lubricant located between the friction interfaces; The nano-solid lubricant is a dispersion of MoS2.

2. The friction pair system according to claim 1, wherein, The friction pair is a ball-disc friction pair; and / or The superhard tetrahedral amorphous carbon film is deposited on the disk side of the ball-disc friction pair, and the multi-doped graphite carbon film is deposited on the ball side of the ball-disc friction pair.

3. The friction pair system according to claim 1 or 2, wherein, The multi-component doped graphite carbon film contains Ag, Ni, and Cu as dopants, with a total doping amount of 15 at%-25 at%. The general formula of the multi-component metals is Ag. x Ni y Cu z Where 0 < x ≤ 4, 1 ≤ y ≤ 2, 1 ≤ z ≤ 2; and / or The atomic percentages of Ag, Ni, and Cu in the multi-doped graphite carbon film are (0-4):(1-2):(1-2).

4. The friction pair system according to claim 3, wherein, In the multi-component doped graphite carbon film, x=4, y=2, z=1, the multi-component metal is Ag4Ni2Cu1, and the total doping amount of Ag, Ni, and Cu is 20 at%; or x=4, y=1, z=2, the multi-metal is Ag4Ni1Cu2, and the total doping amount of Ag, Ni and Cu is 25 at.

5. The friction pair system according to claim 1 or 2, wherein, In the superhard tetrahedral amorphous carbon film, sp 3 The content of C is 60%-80%; and / or The hardness of the superhard tetrahedral amorphous carbon film is 35-45 GPa; and / or The thickness of the working layer of the superhard tetrahedral amorphous carbon film is 500-800 nm.

6. The friction pair system according to claim 1 or 2, wherein, In the nano-solid lubricant, the concentration of MoS2 is 0.05-0.15 mg / mL, and the solvent is anhydrous ethanol; and / or In the nano-solid lubricant, MoS2 is a two-dimensional nanostructure with a sheet diameter of 0.02-1.00 μm, 3-10 layers, and a thickness of 1-8 nm.

7. The friction pair system according to claim 1 or 2, wherein, The material of the friction pair is selected from one or more of bearing steel, high-temperature alloy steel, stainless steel, titanium alloy steel and monocrystalline silicon.

8. A method for preparing a friction pair system according to any one of claims 2 to 7, comprising the following steps: 1) Coating the disk side of the ball-disc friction pair with an ultrahard tetrahedral amorphous carbon film; 2) Coating a multi-element doped graphite-carbon film onto the spherical side of the ball-disc friction pair; 3) Add nano solid lubricant to the surface of the disk side in step 1) to obtain the friction pair system.

9. The method according to claim 8, wherein, Step 3) includes: repeatedly applying the nano-solid lubricant at the same position on the side surface of the disk, and drying it after each application; Optionally, the dripping volume is 3 μL / time to 10 μL / time; Optionally, the number of drops can be 8-12; Optionally, the drying temperature is 40-60℃ and the drying time is 5-15 minutes.

10. A method for achieving ultra-low friction of an ultrahard carbon film using a friction pair system according to any one of claims 1 to 7 or a friction pair system prepared by any one of claims 8 to 9, comprising: In an atmospheric environment with a relative humidity of 12±8%, and under conditions of load of 1~10 N, frequency of 1~5 Hz, and amplitude of 4-8 mm, the friction pair system is used in mechanical moving parts of high-end equipment or precision instruments to achieve friction reduction and wear resistance.

Images