Composite lubricating system used in space environment and preparation method

Abstract

The invention belongs to the technical field of lubricants, and particularly relates to a composite lubricating system used in a space environment and a preparation method, the composite lubricating system uses lubricating grease and a solid film as lubricating materials at the same time, and the lubricating grease and the solid film jointly achieve the anti-friction and anti-wear effects. Lubricating grease is coated on one friction surface of the friction pair, and the solid film is sprayed on the other friction surface of the friction pair; or the solid film is sprayed on one friction surface of the friction pair, and the lubricating grease is coated on the surface of the solid film. According to the invention, macroscopic super lubrication can be realized in a vacuum environment, a solid-liquid composite lubrication system in the vacuum environment is perfected, and macroscopic super lubrication under harsh conditions is also a huge progress.

Description

Technical Field

[0001] The present invention belongs to the technical field of lubricants, and particularly relates to a composite lubrication system used in a space environment and a preparation method thereof. Background Art

[0002] With the rapid development of space technology, the importance of space lubrication technology has become increasingly prominent. Research shows that the failure of many space mechanical components is closely related to the insufficient performance or functional degradation of the lubrication system. Therefore, achieving long-life and high-reliability lubrication for space moving components has become an important research direction. Currently, space lubrication methods are mainly divided into three types: solid lubrication, liquid lubrication, and composite lubrication. Solid lubricants have the characteristics of stable lubrication performance, no volatilization, and no creeping migration, but are prone to generating wear debris and have poor self-healing properties; liquid lubricants have the advantages of low friction coefficient and long service life, but are prone to volatilization at high temperatures, solidification at low temperatures, and easy creeping. To overcome the limitations of a single lubrication method, researchers have gradually turned their attention to the solid-liquid composite lubrication system, attempting to improve the overall lubrication performance by combining the advantages of both.

[0003] The solid-liquid composite lubrication system has shown great potential in a variety of preliminary studies, such as the combination of soft metal films (such as silver and gold) and liquid lubricants, the combination of diamond-like carbon (DLC) films and liquid lubricants, and the combination of layered solid lubricating materials (such as MoS 2 , WS 2 ) and liquid lubricants. However, this field is still in the initial stage of development, and there are many technical challenges to be solved, including the interaction between lubricants, the synergistic effect, and the stability under different environmental conditions. In-depth study of these key factors will provide a theoretical basis and technical support for achieving long-cycle and high-reliability lubrication, and is expected to meet the high standards of future spacecraft and space stations, providing more solid technical support for the development of the space industry. Liquid lubricants often have good fluidity, but may also cause problems such as creeping, leakage, and volatilization. In contrast, grease shows lower fluidity in the static state, or even no fluidity at all, and can effectively avoid these challenges faced by liquid lubricants. Therefore, grease, as a substitute material for liquid lubricants, has shown significant advantages. To further improve the performance of the solid-liquid composite lubrication system, a composite lubrication system has been designed. Compared with the traditional solid-liquid composite lubrication system, this system further improves the fluidity problem of the liquid lubricant, shows better stability and reliability, and has great application potential. Summary of the Invention

[0004] The present invention discloses a composite lubrication system and a preparation method thereof for use in a space environment. The present invention can achieve macroscopic superlubrication in a space environment, which not only improves the composite lubrication system in a space environment, but also represents a huge progress in achieving macroscopic superlubrication under harsh conditions. At the same time, the lubricant has shear thinning characteristics, showing fluid behavior under high-speed shearing and grease state under low shearing, effectively preventing the influence of the flow, creep and leakage of liquid lubricants on equipment.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A composite lubrication system for use in a space environment, wherein the composite lubrication system simultaneously uses grease and a solid film as lubricating materials to jointly achieve the effects of reducing friction and wear. The structure of the composite lubrication system includes: applying grease to one friction surface of the friction pair, and spraying the solid film on the other friction surface of the friction pair; or spraying the solid film on one friction surface of the friction pair and applying grease on the surface of the solid film.

[0007] Preferably, both friction surfaces of the friction pair are made of steel material.

[0008] Preferably, the solid film is one of a PAI (polyimide) solid film, a PFA (perfluoroalkoxy ethylene) solid film, an FEP (fluorinated ethylene propylene copolymer) solid film, a POM (polyoxymethylene) solid film, a UHMWPE (ultra-high molecular weight polyethylene) solid film, a PEEK (polyether ether ketone) solid film, a PI (polyimide) solid film, and a PTFE (polytetrafluoroethylene) solid film.

[0009] A preparation method of grease in a composite lubrication system for use in a space environment, including: the grease is prepared by a room-temperature stirring method, and the sample for stirring is a mixture of PTFE (polytetrafluoroethylene) powder and one or several of the following components; the components are perfluoropolyether PFPE or poly-α-olefin PAO or polyalkylated cyclopentane MACs or silicohydrocarbon SiHC or silicone oil or ionic liquid ILs; the stirring time is 30 min - 12 h.

[0010] Preferably, the stirring time is one of 30 min, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, and 12 h.

[0011] The beneficial effects of the composite lubrication system and the preparation method thereof for use in a space environment according to the present invention are as follows:

[0012] When the solid lubricating film and PTFE-based grease used in the present invention are used alone, although they have a certain anti-friction effect, it is difficult to achieve macroscopic superlubrication, and there is also wear phenomenon. Through their synergistic effect, macroscopic superlubrication is achieved in the space environment, and the wear is almost zero, showing a good synergistic effect. In addition, the prepared PTFE-based grease maintains zero loss within 25 hours at 1X10 -4 Pa and 100 °C, proving its space adaptability and application potential under harsh conditions. This lubricant has the characteristics of shear thinning, showing fluidity during high-speed shearing and grease state during low-speed shearing, effectively preventing the influence of the flow, creep and leakage of liquid lubricants on the equipment. This lubricating material has broad application prospects in the aerospace field, greatly promoting the practical application of the composite lubrication system.

[0013] In summary, the beneficial effects of the present invention are as follows: 1. It can achieve macroscopic superlubrication under space conditions. 2. It has excellent anti-wear effect, and near-zero wear can be achieved while achieving superlubrication. 3. After 300,000 rotation tests, the present invention can still remain stable and has broad application prospects. 4. Compared with the simple PAI film and PTFE-based grease used alone as lubricants, it has a good synergistic effect, further expanding the composite lubrication system. 5. The PTFE-based grease can also alleviate the problems caused by the creep and leakage of lubricating oil. Description of the Drawings

[0014] Figure 1 Illustration of the PTFE-based grease provided for Example 7;

[0015] Figure 2 Illustration of the optical microscope of the PAI film provided for Example 7;

[0016] Figure 3 Schematic diagram of the PAI solid lubricating film (PAl solid film Steel) on the steel surface and the PTFE-based grease (Steel PTFE-based lubricant) on the steel ball surface provided for Example 8 (the left half in the figure is the friction pair model, and the right half is the schematic diagram of the local friction state represented by the elliptical dotted line in the friction pair model);

[0017] Figure 4 Graph of the change of the friction coefficient of the PAI solid lubricating film and the PTFE-based grease provided for Example 9 with time;

[0018] Figure 5 Three-dimensional morphology of the PAI solid lubricating film and the PTFE-based grease after wear provided for Example 9. Detailed Description of the Invention

[0019] The following is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0020] The following embodiments can be understood as separately expressing a part of the local structure or method of the present invention, or can also be understood as the embodiments being combined with each other to explain the connotation of the structure or method of a larger scope of the present invention.

[0021] Embodiment 1

[0022] A composite lubrication system used in a space environment, as Figure 3 shown, the composite lubrication system simultaneously uses grease and a solid film as lubricating materials to jointly achieve the effects of reducing friction and wear. The structure of the composite lubrication system includes: applying grease to one friction surface in the friction pair, and spraying the solid film on the other friction surface of the friction pair; or spraying the solid film on one friction surface of the friction pair and applying grease on the surface of the solid film.

[0023] Embodiment 2

[0024] Based on Embodiment 1, this embodiment discloses that both friction surfaces of the friction pair are made of steel material.

[0025] Embodiment 3

[0026] Based on Embodiment 2, this embodiment gives several implementation manners of the solid film, specifically:

[0027] (A1) PAI (polyimide) solid film; (A2) PFA (perfluoroalkoxy ethylene) solid film; (A3) FEP (fluorinated ethylene propylene copolymer) solid film; (A4) POM (polyoxymethylene) solid film; (A5) UHMWPE (ultra-high molecular weight polyethylene) solid film; (A6) PEEK (polyetheretherketone) solid film; (A7) PI (polyimide) solid film; (A8) PTFE (polytetrafluoroethylene) solid film.

[0028] Among them, (A1)-(A8) are the numbers of specific implementation manners, and any one of the solid films can be selected according to needs.

[0029] Embodiment 4

[0030] Based on Embodiments 1-3, this embodiment discloses: A method for preparing a grease in a composite lubrication system used in a space environment, including: The grease is prepared by a room-temperature stirring method, and the sample for stirring is a mixture of PTFE (polytetrafluoroethylene) powder and one or more of the following components; The components include: (B1) perfluoropolyether (PFPE); (B2) polyalphaolefin (PAO); (B3) polyalkylated cyclopentane (MACs); (B4) silicohydrocarbon (SiHC); (B5) silicone oil (preferably using 114 # 、115 # silicone oil); (B6) ionic liquid (ILs). Among them, (B1)-(B6) are the serial numbers of specific embodiments respectively.

[0031] Example 5

[0032] The grease is prepared by a room-temperature stirring method. This embodiment gives 13 embodiments of the stirring time in the preparation of the grease, specifically as follows:

[0033] (B21) The stirring time is 30 min, (B22) The stirring time is 1 h, (B23) The stirring time is 2 h, (B24) The stirring time is 3 h, (B25) The stirring time is 4 h, (B26) The stirring time is 5 h, (B27) The stirring time is 6 h, (B28) The stirring time is 7 h, (B29) The stirring time is 8 h, (B210) The stirring time is 9 h, (B211) The stirring time is 10 h, (B212) The stirring time is 11 h, (B213) The stirring time is 12 h.

[0034] Example 6

[0035] The present invention also provides an experimental process of the solid-liquid composite lubrication system described in the above technical solution, including the following steps: On the solid-grease composite lubrication friction interface, the friction surface of the specimen is steel, the lower specimen is a PAI film sprayed on a steel substrate, and the middle is the prepared PTFE-based grease. The two lubricating materials, the PAI film and the PTFE-based grease, act together to achieve solid-grease composite lubrication at the interface.

[0036] Example 7

[0037] After sandblasting and ultrasonic cleaning with absolute ethanol three times on a GCr15 stainless steel block, the raw materials are sprayed and treated at 300 °C for 10 hours to obtain a PAI solid lubricating film. The PTFE-based grease is prepared by stirring 4 g of PTFE powder and 5 g of PAO30 for 2 hours. Figure 1 The prepared PTFE-based grease is shown, Figure 2 The optical diagram of the PAI solid film is shown.

[0038] Example 8

[0039] The PAI solid film was prepared by the spraying method; the PTFE-based grease was prepared by stirring 4 g of PTFE powder, 5 g of MACs and 0.2 g of 1-butyl-3-methylimidazolium hexafluorophosphate for 1 h.

[0040] The tribological properties of the prepared PAI solid lubricating film and PTFE-based grease were tested. Specifically, the friction performance was tested in the rotational mode of a CSM friction machine. The upper friction pair was a 9Gr18 steel ball with a diameter of 6 mm, and the lower friction pair was a 9Gr18 steel block with a PAI solid film. Before the experiment, the friction pairs needed to be ultrasonically treated in an ethanol and acetone solution for 10 minutes, then rinsed with deionized water, and finally dried in an oven. The test load was 2 N, the rotational speed was 200 rpm, and the radius was 7 mm. The schematic diagrams of the PAI solid film and PTFE-based grease used in this example are shown in Figure 3 shown.

[0041] Example 9

[0042] The PAI solid film was prepared by the spraying method; the PTFE-based grease was prepared by stirring 4 g of PTFE powder, 4 g of PFPE and 0.3 g of 1-butyl-3-methylimidazolium acetate for 1 h.

[0043] The tribological properties of the prepared PAI solid lubricating film and PTFE-based grease were tested. Specifically, the friction performance was tested in the rotational mode of a space friction machine. The upper friction pair was a 9Gr18 steel ball with a diameter of 6 mm, and the lower friction pair was a GCr15 steel block with a PAI solid film. Before the experiment, the friction pairs needed to be ultrasonically treated in an ethanol and acetone solution for 10 minutes, then rinsed with deionized water, and finally dried in an oven. The test load was 2 N, the rotational speed was 100 rpm, and the radius was 5 mm. The friction coefficients and three-dimensional morphologies after wear of the PAI solid lubricating film and PTFE-based grease used in this example are shown in Figure 4 and 5 shown.

Claims

1. A composite lubrication system for use in a space environment, characterized by: The composite lubrication system uses grease and solid film as lubricating materials to jointly achieve the effect of reducing friction and resisting wear. The structure of the composite lubrication system includes: coating grease on one friction surface of the friction pair, and spraying the solid film on the other friction surface of the friction pair; or spraying the solid film on one friction surface of the friction pair, and coating grease on the surface of the solid film.

2. A composite lubrication system for use in a space environment as claimed in claim 1, characterized in that: The two friction surfaces of the friction pair are both made of steel.

3. A composite lubrication system for use in a space environment as claimed in claim 2, characterized in that: The solid film is one of polyimide solid film, perfluoroalkoxyethylene solid film, fluorinated ethylene propylene copolymer solid film, polyoxymethylene solid film, ultra-high molecular weight polyethylene solid film, polyetheretherketone solid film, polyimide solid film and polytetrafluoroethylene solid film.

4. The method for preparing grease in a composite lubrication system for use in a space environment as claimed in claim 3, characterized in that: The grease is prepared by a room temperature stirring method, and the stirred sample is a mixture of PTFE polytetrafluoroethylene powder and one or more of the following components; the components are perfluoropolyether PFPE or polyα-olefin PAO or polyalkylated cyclopentane MACs or silane SiHC or silicone oil or ionic liquid ILs; the stirring time is 30min-12h.

5. The method for preparing grease in a composite lubrication system used in a space environment as claimed in claim 4, characterized in that: The stirring time is one of 30 min, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, and 12 h.

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