An ultralow temperature vacuum lubricating coating and a method for producing the same

Abstract

This invention discloses an ultra-low temperature vacuum lubrication coating and its preparation method. The preparation involves adding a graphite-based lubricant with a specific layered structure to a low-temperature resistant binder, ultrasonically dispersing the mixture to obtain a dispersion, spraying it onto a substrate surface, and curing it to obtain a graphite-based composite coating. The coating utilizes ultra-low temperature friction-induced formation of a graphite roller structure to achieve a molecular rolling lubrication mechanism, resulting in low friction and wear performance. This is achieved under ultra-low temperature (20-200K) vacuum (vacuum degree <5×10⁻⁶) conditions. ‑4 Under an environment of (Pa), the coefficient of friction of the graphite-based composite coating is as low as 0.04-0.06, and the wear rate is 1.0×10⁻⁶. ‑8 -1.0×10 ‑ 7 mm 3 The graphite-based composite coating of this invention is on the order of N·m. It is applicable to the surface lubrication treatment of moving parts of cryogenic equipment in aerospace, superconducting, quantum computing, and polar regions. Moreover, the preparation method is simple and suitable for engineering promotion and use.

Description

Technical Field

[0001] This invention relates to an ultra-low temperature vacuum lubrication coating and its preparation method, belonging to the field of mechanical lubrication. Background Technology

[0002] With the rapid development of key areas such as my country's lunar exploration, deep space exploration, superconductivity, and quantum computing, the lubrication of moving parts at ultra-low temperatures has become a major technical challenge. The reliable service of materials in extreme ultra-low temperature environments is crucial for future breakthroughs in cutting-edge technologies. For example, the Chang'e 7 lunar rover will face the requirement of continuous operation at temperatures below 100 K during its lunar polar exploration mission, while its existing mobile subsystems are primarily in a dormant state at low temperatures. Currently, the material systems for ultra-low temperature friction mainly consist of space lubrication materials such as polymers, metals, solid adhesive coatings, and vacuum sputtered lubrication films. However, most of these materials suffer from deterioration in tribological properties at ultra-low temperatures. my country has a severe lack of targeted research in ultra-low temperature tribology, and there is a gap in the field of lubrication technology below -65°C, which seriously restricts the selection of lubrication materials and the reliability of equipment under ultra-low temperature service conditions. Therefore, the development of ultra-low temperature lubrication technology is urgently needed.

[0003] Graphite, as an important solid lubricant, has a typical layered structure with weak van der Waals forces binding the layers together. It exhibits excellent lubrication performance in air, but easily fails in a vacuum, leading to serious air disasters. However, the inventors of this patent discovered a unique phenomenon in their previous research: layered graphite materials self-roll to form graphite roller structures during ultra-low temperature friction. This ultra-low temperature friction-induced graphite roller structure formation achieves molecular rolling lubrication. Based on this discovery, this invention creatively introduces a graphite-based lubricant with a specific layered structure and combines it with a low-temperature resistant binder, inventing an ultra-low temperature (20-200K) vacuum lubricant (vacuum degree <5×10⁻⁶). -4 Composite coating technology with excellent lubrication and wear resistance under low temperature conditions (Pa) provides technical support for solving the low temperature lubrication problem of equipment in cryogenic service such as aerospace, superconducting, quantum computing, and polar regions. Summary of the Invention

[0004] The purpose of this invention is to provide a graphite-based composite coating with low friction and wear properties under ultra-low temperature vacuum conditions and its preparation method.

[0005] I. Preparation of Graphite-Based Composite Coatings

[0006] (1) Preparation of lubricant dispersion

[0007] A layered graphite-based material was added to a dispersion at a concentration of 400–4000 mg / L. The number of layers in the layered graphite-based material ranged from 1 to 100, and the lateral dimensions of the layers ranged from 0 to 100 µm. The dispersion was then ultrasonically dispersed to obtain a lubricant dispersion. The graphite-based material could be graphite, microcrystalline graphite, or graphene, and the dispersion could be deionized water, anhydrous ethanol, N,N-dimethylformamide, or N,N-dimethylacetamide. The ultrasonic power ranged from 500 to 2000 W, and the ultrasonic time ranged from 10 to 150 min.

[0008] (2) Preparation of the complex dispersion

[0009] In step (1), a low-temperature resistant binder is added to the dispersion. The low-temperature resistant binder can be polyamide-imide, polyimide, polyetheretherketone, polyurethane, or epoxy resin, and the mass ratio of binder to lubricant is in the range of 1:0.05 to 1:20. The mass content of solid components in the composite dispersion is 10%-50%. Then, ultrasonic dispersion is performed. The ultrasonic power is 500-2000 W and the ultrasonic time is 5-120 min.

[0010] (3) Preparation of graphite-based composite coating

[0011] The composite dispersion prepared in step (2) was sprayed onto the surface of the substrate under compressed air (oil-free) or compressed nitrogen. The substrate material was selected from metals such as bearing steel, stainless steel, aluminum, or titanium alloy. The substrate was surface-dried in a drying cabinet or air, and then placed in a blower box for curing. The curing procedure was as follows: the temperature was raised to 150-180℃ within 40-120 min, held for 60-180 min, then raised to 260-280℃ within 40-120 min, held for 60-120 min, and finally cooled naturally to obtain a graphite-based composite coating.

[0012] The lubrication mechanism of the graphite-based composite coating of this invention: Under vacuum and ultra-low temperature conditions, due to the temperature difference between the upper and lower surfaces of the frictionally exfoliated graphite nanosheets, a unique self-curling effect occurs at the edges of the sheets. Utilizing this effect, the frictional shear force further drives the curled-up sheets to roll up and form in-situ a graphite roll structure that is parallel to each other along the frictional sliding direction. Figure 1 These molecular rolls act like wheels, providing rolling lubrication. Therefore, the graphite-based composite coating of this invention exhibits low friction and wear characteristics in a vacuum cryogenic environment.

[0013] II. Microstructure of the Friction Interface of Graphite-Based Composite Coatings

[0014] Figure 1This is a high-resolution transmission electron microscope (TEM) image of the special graphite roller structure formed on the friction interface of the graphite-based composite coating in this invention under ultra-low temperature vacuum conditions. It can be seen that the layered graphite-based material forms a graphite roller structure, with its axial direction being a roll-like structure of several hundred micrometers. This structure can play a rolling lubrication role at the friction interface, which is crucial for the graphite-based composite coating to achieve low friction and wear performance in ultra-low temperature vacuum environments.

[0015] III. Tribological Properties of Graphite-Based Composite Coatings

[0016] Using the planar sample prepared according to this invention as the lower sample and a commercially available steel ball (Ф6 mm, GCr15, Ra≈20 nm) as the upper sample, under a vacuum degree <5×10 -4 The test was conducted on a ball-disc friction testing machine with a normal load of 1-5 N over a temperature range of 20-200 K and a unidirectional linear rotation mode. The rotation radius was 5-10 mm and the rotation speed was 60-120 rpm.

[0017] Figure 2 The figure shows the graphite-based composite coating prepared according to the present invention at an ultra-low temperature of 50 K and a vacuum degree of 1.0 × 10⁻⁶. -4 The coefficient of friction variation curves in a vacuum environment at Pa are shown in Table 1. -4 Under an environment of 20–200 K, the experimental results of the friction coefficient and wear rate of the graphite-based composite coating showed that the friction coefficient remained between 0.04 and 0.06, and the wear rate was within 1.0 × 10⁻⁶. -8 ~1.0 ×10 -7 mm 3 On the order of magnitude / (N·m).

[0018] Table 1. Experimental results of friction coefficient and wear rate of graphite-based composite coatings.

[0019]

[0020] In summary, this invention utilizes a special layered graphite-based material to prepare a graphite-based composite coating, and leverages ultra-low temperature friction to induce the formation of a graphite roller structure to achieve molecular rolling lubrication, thereby obtaining low friction and wear performance in an ultra-low temperature vacuum environment. This invention provides a new ultra-low temperature vacuum lubrication technology, and the graphite-based composite coating is applicable to the surface lubrication treatment of moving parts in cryogenic service equipment such as aerospace, superconducting, quantum computing, and polar regions. Furthermore, the coating preparation method of this invention is simple and easy to implement, and suitable for widespread application in engineered parts and under operating conditions. Attached Figure Description

[0021] Figure 1This is a high-resolution transmission electron microscope image of the special graphite roller structure formed on the friction interface of the graphite-based composite coating of the present invention.

[0022] Figure 2 The graphite-based composite coating of this invention is used at low temperature (50 K) and under vacuum (1.0 × 10⁻⁶ K) conditions. -4 Friction coefficient curve in an environment of Pa. Detailed Implementation

[0023] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Specific conditions and test methods not explicitly described in the following embodiments are generally performed under conventional conditions.

[0024] Example 1

[0025] (1) Layered microcrystalline graphite was added to a deionized water dispersion at a mass concentration of 600 mg / L, wherein the number of layers of microcrystalline graphite was about 60, and the transverse size of the layers was about 10 µm. Then, ultrasonic dispersion was performed for 20 min at a power of 500 W to obtain a deionized water dispersion of microcrystalline graphite.

[0026] (2) Add polyimide resin to the microcrystalline graphite deionized water dispersion obtained in step (1), wherein the mass ratio of polyimide to microcrystalline graphite is 1:1, and the mass content of solid components in the composite dispersion is 25%. Then perform ultrasonic dispersion for 120 min and ultrasonic power of 500 W.

[0027] (3) The composite dispersion prepared in step (2) is sprayed onto the surface of a stainless steel substrate under compressed nitrogen, dried in air, and then placed in a blower box for curing. The curing procedure is to raise the temperature to 160°C within 60 minutes, keep it at that temperature for 60 minutes, then raise the temperature to 260°C within 60 minutes, keep it at that temperature for 120 minutes, and then let it cool naturally to obtain a microcrystalline graphite composite coating.

[0028] Tribological performance testing: The coefficient of friction was evaluated on a ball-disc friction testing machine. The planar sample prepared in this example was used as the lower sample, and a commercially available steel ball (Ф6 mm, GCr15, Ra ≈ 15 nm) was used as the upper sample. The test was conducted under a vacuum of 3.0 × 10⁻⁶ mm. -5The test was conducted on a ball-disc friction testing machine at a temperature of 20K and a normal load of 1N using a unidirectional linear rotation mode. The results are shown in Table 1. During the experiment, the rotation radius was maintained at 5mm and the rotation speed was maintained at 120rpm.

[0029] Example 2

[0030] (1) Graphite with a lamellar structure was added to an N,N-dimethylacetamide dispersion at a mass concentration of 1000 mg / L, wherein the number of graphite layers was approximately 100 and the transverse size of the lamellar layers was approximately 15 µm. Then, ultrasonic dispersion was performed for 40 min at a power of 1000 W to obtain an N,N-dimethylacetamide dispersion of graphite.

[0031] (2) Add polyamide-imide resin to the graphite N,N-dimethylacetamide dispersion obtained in step (1), wherein the mass ratio of polyamide-imide resin to graphite is 2:1, and the mass content of solid components in the composite dispersion is about 15%. Then perform ultrasonic dispersion for 60 min and ultrasonic power of 500 W.

[0032] (3) The composite dispersion prepared in step (2) is sprayed onto the surface of M2 high-speed steel substrate under compressed air (oil-free), dried in air, and then placed in a blower box for curing. The curing procedure is to raise the temperature to 180°C within 120 min, keep it at that temperature for 120 min, then raise the temperature to 280°C within 120 min, keep it at that temperature for 60 min, and then let it cool naturally to obtain a graphite composite coating.

[0033] Tribological performance testing: The coefficient of friction was evaluated on a ball-disc friction testing machine. The planar sample prepared in this example was used as the lower sample, and commercially available alumina (Ф6 mm, Al2O3, Ra ≈ 10 nm) was used as the upper sample. The test was conducted under a vacuum of 4.0 × 10⁻⁶ mm. -4 The test was conducted on a ball-disc friction testing machine at a temperature of 80 K and a normal load of 1 N using a unidirectional linear rotation mode. The results are shown in Table 1. During the experiment, the rotation radius was maintained at 10 mm and the rotation speed was maintained at 60 rpm.

[0034] Example 3

[0035] (1) Graphene with a sheet-like structure was added to an N,N-dimethylformamide dispersion at a mass concentration of 800 mg / L, wherein the number of graphene layers was 8-10 and the transverse size of the sheets was approximately 0.5-5 µm. Then, ultrasonic dispersion was performed for 60 min at a power of 1000 W to obtain an N,N-dimethylformamide dispersion of graphene.

[0036] (2) Add epoxy resin to the graphene N,N-dimethylformamide dispersion obtained in step (1). The mass ratio of epoxy resin to graphene is 1:4, and the mass content of solid components in the composite dispersion is 30%. Then, ultrasonic dispersion is performed for 40 min at a power of 1000 W.

[0037] (3) The composite dispersion prepared in step (2) is sprayed onto the surface of the titanium alloy substrate under compressed nitrogen, dried in a drying cabinet, and then placed in a blower box for curing. The curing procedure is to raise the temperature to 170°C within 80 min, keep it at that temperature for 180 min, then raise the temperature to 270°C within 80 min, keep it at that temperature for 120 min, and then let it cool naturally to obtain the graphene composite coating.

[0038] Tribological performance testing: The coefficient of friction was evaluated on a ball-disc friction testing machine. The planar sample prepared in this example was used as the lower sample, and commercial silicon nitride (Ф6 mm, Si3N4, Ra ≈ 10 nm) was used as the upper sample. The test was conducted under a vacuum of 4.0 × 10⁻⁶ nm. -4 At a temperature of 160 K and a normal load of 2 N, the test was conducted on a ball-disc friction testing machine using a unidirectional linear rotation mode. The results are shown in Table 1. During the experiment, the rotation radius was maintained at 10 mm and the rotation speed was maintained at 60 rpm.

[0039] Example 4

[0040] (1) A layered graphene structure was added to an anhydrous ethanol dispersion at a mass concentration of 800 mg / L, wherein the graphene had 100 layers and the transverse size of the sheets was approximately 40 µm. Then, ultrasonic dispersion was performed for 120 min at a power of 2000 W to obtain an anhydrous ethanol dispersion of graphene.

[0041] (2) Add polyurethane resin to the graphite anhydrous ethanol dispersion obtained in step (1). The mass ratio of polyurethane resin to graphite is 1:0.5, and the mass content of solid components in the composite dispersion is 40%. Then, ultrasonic dispersion is performed for 60 min at a power of 1500 W.

[0042] (3) The composite dispersion prepared in step (2) is sprayed onto the surface of the aluminum alloy substrate under compressed nitrogen, dried in a drying cabinet, and then placed in a blower box for curing. The curing procedure is to raise the temperature to 160°C within 60 min, keep it at that temperature for 120 min, raise the temperature to 260°C within 80 min, keep it at that temperature for 100 min, and then let it cool naturally to obtain a graphite composite coating.

[0043] Tribological performance testing: The coefficient of friction was evaluated on a ball-disc friction testing machine. The planar sample prepared in this example was used as the lower sample, and commercially available tungsten carbide (Ф6 mm, WC, Ra ≈ 10 nm) was used as the upper sample. The test was conducted under a vacuum of 3.0 × 10⁻⁶ nm. -5 At a temperature of 200 K and a normal load of 5 N, the test was conducted on a ball-disc friction testing machine using a unidirectional linear rotation mode. The results are shown in Table 1. During the experiment, the rotation radius was maintained at 10 mm and the rotation speed was maintained at 100 rpm.

Claims

1. A method for preparing an ultra-low temperature vacuum lubrication coating, characterized in that, Includes the following steps: 1) Preparation of lubricant dispersion: Add the layered graphite-based material to the dispersion at a mass concentration of 400~4000 mg / L, and then ultrasonically disperse it evenly to obtain the lubricant dispersion. The number of layers in the layered graphite-based material is 8 to 100, and the lateral dimensions of the layers are distributed in the range of 0.5 to 100 µm. The graphite-based material is at least one of graphite or graphene; 2) Preparation of the complex dispersion: A low-temperature resistant binder is added to the lubricant dispersion obtained in step 1), and after ultrasonic dispersion, a complex dispersion is obtained. The binder is at least one selected from polyamide-imide, polyimide, polyetheretherketone, polyurethane, and epoxy resin, and the mass ratio of binder to lubricant is 1:0.05 to 1:20, and the total solid content in the composite dispersion is 10% to 50%. 3) Preparation of graphite-based composite coating: The composite dispersion prepared in step 2) is sprayed onto the surface of the substrate under compressed air or compressed nitrogen. After surface drying in a drying cabinet or air, it is placed in a blower box for curing. The curing procedure is as follows: first, the temperature is raised to 150-180℃ within 40-120 min and held for 60-180 min; then, the temperature is raised to 260-280℃ within 40-120 min and held for 60-120 min; finally, the temperature is allowed to cool naturally to obtain the graphite-based composite coating.

2. The method for preparing an ultra-low temperature vacuum lubricating coating as described in claim 1, characterized in that, In step 1), the dispersion is at least one of deionized water, anhydrous ethanol, N,N-dimethylformamide, and N,N-dimethylacetamide.

3. The method for preparing an ultra-low temperature vacuum lubricating coating as described in claim 1, characterized in that, In step 3), the substrate is one of bearing steel, stainless steel, aluminum or titanium alloy.

4. A cryogenic vacuum lubricating coating prepared by the method described in claim 1.

5. The application of an ultra-low temperature vacuum lubrication coating prepared by the method described in claim 1 on the surface of moving parts of equipment in cryogenic service.

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