Composite solid lubricant for sprocket shaft group and preparation method thereof

Abstract

The invention belongs to the field of lubricants, and relates to a composite solid lubricant for a sprocket shaft group and a preparation method thereof. The composite solid lubricant for the sprocket shaft group is prepared from the following raw materials in percentage by weight: 2-15% of graphite fluoride, 1-4% of terbium-thulium co-doped molybdenum disulfide, 1-3% of organic graphene, 0.07-0.4% of tin powder, 1-11% of polyethylene glycol, 1-7% of a thickening agent and the balance of basic lubricating oil. According to the preparation method, molybdenum disulfide is co-doped with rare earth thulium and terbium, thulium and terbium ions are embedded into molybdenum disulfide layers or replace molybdenum sites through electrostatic adsorption in the hydrothermal reaction process, the layered structure is more compact, oxygenolysis of molybdenum disulfide at high temperature is effectively inhibited, and better oxidation resistance is achieved. The talcum powder is introduced to modify the lithium-based soap, and zinc ions are adopted to modify the talcum powder, so that the dispersibility of the talcum powder is improved, and the thermal stability, wear resistance and water resistance of the lubricant are improved after the talcum powder is compounded with the lithium-based soap.

Description

Technical Field

[0001] The invention belongs to the field of lubricants, and in particular relates to a composite solid lubricant for a sprocket shaft assembly and a preparation method thereof. Background Art

[0002] Sprocket assemblies are core components in industrial transmission systems. They consist of precision-assembled sprockets, shafts, and bearings, specifically designed for power transmission and chain meshing. They are commonly found in heavy equipment such as mining machinery and conveying equipment. Traditional lubricants for sprocket assemblies are typically oil or conventional solid lubricants. Oils are prone to leakage under high loads and strong vibration conditions, leading to lubrication failure. Conventional solid lubricants have limited lubrication properties, making it difficult to form a continuous, effective lubricating film on the complex friction surfaces of the sprocket assembly, thus failing to meet the demands of long-term, high-intensity operation. Furthermore, during operation, the sprocket assembly generates intense friction and wear between the sprocket and chain, and between the bearings and journals. Conventional lubricants lack sufficient wear resistance and are unable to effectively reduce the coefficient of friction and minimize wear. This wear is exacerbated by the combined effects of high loads and vibration, leading to significant wear and tear on sprocket assembly components and a shortened service life. Frequent replacement of sprocket assemblies not only increases equipment maintenance costs but also causes equipment downtime, impacting coal mine production efficiency. Furthermore, the underground environment of coal mines is humid, dusty, and subject to significant temperature fluctuations. Traditional lubricants are susceptible to deterioration and hardening in such harsh environments, resulting in a loss of lubricating properties. Furthermore, traditional lubricants have poor adaptability to diverse operating conditions and struggle to maintain adequate performance under challenging conditions such as high temperatures, high loads, and low speeds. Performance degradation is particularly pronounced under high vibration conditions.

[0003] Existing common lubricants often focus on a single performance aspect, such as lubricity or wear resistance, while neglecting the comprehensive improvement of other properties. For example, some lubricants offer good lubrication but poor wear resistance, while others suffer from issues such as poor oxidation resistance, thermal stability, and a short service life. Therefore, further research on solid lubricants for sprocket shaft assemblies is needed. Summary of the Invention

[0004] A first object of the present invention is to provide a composite solid lubricant for a sprocket shaft assembly, wherein the composite solid lubricant for a sprocket shaft assembly has excellent antioxidant performance, thermal stability, and wear resistance.

[0005] A second object of the present invention is to provide a method for preparing a composite solid lubricant for a sprocket shaft assembly, wherein the preparation method has a simple process and is suitable for industrial production and popularization and application.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The invention provides a composite solid lubricant for a sprocket shaft assembly. The composite solid lubricant is composed of the following raw materials in percentage by weight: 2-15% of graphite fluoride, 1-4% of terbium-thulium co-doped molybdenum disulfide, 1-3% of organic graphene, 0.07-0.4% of tin powder, 1-11% of polyethylene glycol, 1-7% of a thickener, and the balance being base lubricating oil.

[0008] Furthermore, the preparation method of terbium-thulium co-doped molybdenum disulfide comprises the following steps:

[0009] (1) dissolving molybdenum pentachloride in a mixed solution of ethanol and deionized water to obtain solution A;

[0010] (2) Sodium sulfide, thulium chloride and terbium chloride are dissolved in deionized water, and then solution A and sodium oleate are added, dispersed evenly and subjected to hydrothermal reaction, and separated, washed and dried after the reaction to obtain the product.

[0011] Furthermore, in step (1), the usage ratio of molybdenum pentachloride, ethanol and deionized water is 0.1-0.2 mol:1L:1L.

[0012] Furthermore, in step (2), the molar ratio of molybdenum pentachloride, thulium chloride, terbium chloride, sodium sulfide and sodium oleate is 1:(0.1-0.15):(0.1-0.15):(5-5.5):(4-8); the concentration of sodium sulfide after being dissolved in deionized water is 0.4-0.6 mol / L; the temperature of the hydrothermal reaction is 180-220°C and the time is 10-15h.

[0013] Furthermore, the thickener is talc-modified lithium soap; the base lubricant is perfluoropolyether; and the organic graphene is ethylenediamine-functionalized graphene oxide.

[0014] Furthermore, the preparation method of the talc-modified lithium soap comprises the following steps:

[0015] (1) adding talc and sodium hydroxide to a zinc chloride solution, reacting, filtering, washing, and drying to obtain modified talc;

[0016] (2) mixing the modified talc and 12-hydroxystearic acid and ball-milling them to obtain a modified talc-12-hydroxystearic acid complex;

[0017] (3) Adding the modified talc-12-hydroxystearic acid complex to a lithium hydroxide solution to carry out a saponification reaction, followed by dehydration to obtain the product.

[0018] Furthermore, in the step (1), the dosage ratio of sodium hydroxide, talc and zinc chloride solution is 1g:3-5g:30-50mL; the concentration of zinc chloride solution is 0.2-0.3mol / L; and the reaction time is 0.5-1h.

[0019] Furthermore, in the step (2), the mass ratio of modified talc to 12-hydroxystearic acid is 1:3-7; the ball milling speed is 500-600 r / min, and the ball milling time is 20-25 h.

[0020] Furthermore, in step (3), the mass ratio of the modified talc-12-hydroxystearic acid complex to lithium hydroxide is 8-13:1-5; the mass concentration of the lithium hydroxide solution is 9-12%; the saponification reaction temperature is 85-100°C and the time is 10-20h; and the dehydration temperature is 220-240°C.

[0021] The present invention provides a method for preparing the composite solid lubricant for the sprocket shaft assembly, comprising the following steps:

[0022] (1) According to the raw material composition, terbium-thulium co-doped molybdenum disulfide, organic graphene, graphite fluoride, tin powder, polyethylene glycol and a thickener are mixed and ground to obtain a mixed material;

[0023] (2) After heating the mixture to 150-160° C., add base lubricating oil, stir at a speed of 500-1000 r / min for 80-120 min, and then cool to room temperature to obtain the product.

[0024] Compared with the prior art, the beneficial effects of the present invention are mainly:

[0025] The composite solid lubricant for sprocket shaft assemblies of the present invention is prepared by introducing terbium and thulium co-doped molybdenum disulfide and talc-modified lithium soap into the raw material composition. The resulting composite solid lubricant for sprocket shaft assemblies has excellent antioxidant properties, thermal stability, and wear resistance. The specific analysis is as follows:

[0026] (1) The present invention utilizes rare earth thulium and terbium to co-dope molybdenum disulfide, wherein the rare earth ions are embedded in the molybdenum disulfide interlayer or replace the molybdenum site through electrostatic adsorption during the hydrothermal reaction, so that the edge sites of molybdenum disulfide are reduced and the layered structure is denser. This structural reinforcement can effectively inhibit the oxidative decomposition of molybdenum disulfide at high temperatures. Furthermore, rare earth has an oxygen affinity and can form an oxide before molybdenum. It acts as a protective layer to prevent the oxidation of molybdenum disulfide, and terbium and thulium are both variable valence rare earths, and their oxide layers can achieve self-repair at high temperatures. Therefore, compared with adding antioxidants alone to lubricants, the rare earth mixed doped molybdenum disulfide of the present invention has better antioxidant capacity.

[0027] (2) Lithium soap is a commonly used high-efficiency thickener in lubricants. It forms a three-dimensional network structure by interweaving soap fibers, thickening the base oil into a stable paste-like grease. The synergistic effect with the base oil can significantly reduce the direct contact of the metal surface and reduce the friction coefficient. When compounded with additives such as molybdenum disulfide, it can form a more stable lubricating film to prevent the metal surface from being scratched or adhesively worn. In addition, lithium soap has good water resistance and rust resistance, can be applied to complex working conditions, and plays a role in sealing and shock absorption. However, the high-temperature stability of lithium soap is poor. The present invention introduces talcum powder to modify the lithium soap. Among them, talcum powder is a layered silicate configuration with excellent lubricity and thermal stability. It has a large number of hydrophilic hydroxyl groups on the surface. Under the action of alkaline conditions, it can undergo coordination or ion exchange reaction with zinc ions, thereby expanding the interlayer spacing and increasing the porosity. The combination of talc and lithium soap can improve the thermal stability of the thickener and enhance the overall lubricity, wear resistance and water resistance of the lubricant. At the same time, the increased porosity can improve the dispersibility of talc, adsorb and slow-release lubricants, and maintain the thermal stability of the lubrication network.

[0028] The preparation method of the composite solid lubricant for the sprocket shaft assembly of the present invention has simple process and is suitable for industrial production and popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a scanning electron microscope image of terbium and thulium co-doped molybdenum disulfide obtained in Example 1 of the present invention.

[0030] Figure 2 This is a scanning electron microscope image of the talc-modified lithium soap obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be further described below in conjunction with specific embodiments. However, it should be understood by those skilled in the art that the following examples are only intended to illustrate the present invention and should not be construed as limiting the present invention. Specific conditions not specified in the examples are to be followed according to conventional conditions or the conditions recommended by the manufacturer. All reagents or instruments used, unless otherwise specified, are conventional products obtained from commercial channels.

[0032] In the embodiment of the present invention, the organic graphene is ethylenediamine-functionalized graphene oxide, and its preparation method is as follows: 0.1 g of graphene oxide is added to 100 mL of aqueous solution, and after ultrasonic treatment, a graphene oxide dispersion is obtained; 3 mL of the graphene oxide dispersion is added to 100 mL of N,N-dimethylformamide, mixed and stirred for 30 minutes, and then ultrasonically treated at 40°C for 2 hours to obtain a graphene oxide / dimethylformamide suspension; then 60 mL of ethylenediamine is added while stirring, and ultrasonically treated at 30°C for 2 hours. After the reaction, the mixture is washed and dried to obtain ethylenediamine-functionalized graphene oxide.

[0033] Example 1

[0034] This embodiment provides a composite solid lubricant for a sprocket shaft assembly, which is composed of the following raw materials in percentage by weight: 10% graphite fluoride, 3% terbium-thulium co-doped molybdenum disulfide, 2% organic graphene, 0.2% tin powder, 6% polyethylene glycol, 5% thickener (talc-modified lithium soap), and the balance as base lubricant (perfluoropolyether).

[0035] The preparation method of terbium-thulium co-doped molybdenum disulfide in this embodiment comprises the following steps:

[0036] (1) dissolving molybdenum pentachloride in a mixed solution of ethanol and deionized water, wherein the ratio of molybdenum pentachloride to ethanol to deionized water is 0.15 mol:1 L:1 L, to obtain solution A;

[0037] (2) Sodium sulfide, thulium chloride and terbium chloride are dissolved in deionized water, and the concentration of sodium sulfide in the deionized water is 0.5 mol / L after dissolution; solution A and surfactant sodium oleate are then added to disperse them evenly; the molar ratio of molybdenum pentachloride, thulium chloride, terbium chloride, sodium sulfide and sodium oleate is 1:0.12:0.12:5.3:6; heating to 200°C, carrying out hydrothermal reaction for 12 hours, separating, washing and drying after the reaction to obtain terbium-thulium co-doped molybdenum disulfide.

[0038] The scanning electron microscope image (SEM image) of terbium and thulium co-doped molybdenum disulfide obtained in this embodiment is as follows Figure 1 shown.

[0039] The preparation method of talc-modified lithium soap in this embodiment comprises the following steps:

[0040] (1) Add talc powder and sodium hydroxide to a 0.25 mol / L zinc chloride aqueous solution, with the ratio of sodium hydroxide, talc powder, and zinc chloride solution being 1 g:4 g:40 mL; react under ultrasonic stirring for 0.5 h, filter, wash, and dry to obtain modified talc powder;

[0041] (2) Modified talc and 12-hydroxystearic acid were mixed in a mass ratio of 1:5 and ball-milled at a ball-milling speed of 550 r / min for 22 h to obtain a modified talc-12-hydroxystearic acid complex;

[0042] (3) Adding the modified talc-12-hydroxystearic acid complex to a lithium hydroxide aqueous solution, wherein the mass ratio of the modified talc-12-hydroxystearic acid complex to lithium hydroxide is 10:3, and the mass concentration of lithium hydroxide in the lithium hydroxide aqueous solution is 10%; heating to 90°C, stirring for saponification reaction for 15 hours, and then heating to 230°C for dehydration to obtain talc-modified lithium soap.

[0043] The scanning electron microscope image (SEM image) of the talc-modified lithium soap obtained in this embodiment is as follows: Figure 2 shown.

[0044] This embodiment provides a method for preparing a composite solid lubricant for a sprocket shaft assembly, comprising the following steps:

[0045] (1) According to the raw material composition, terbium-thulium co-doped molybdenum disulfide, organic graphene, graphite fluoride, tin powder, polyethylene glycol and a thickener are ground and mixed uniformly, and the particle size after grinding is ≤80 μm to obtain a mixed material;

[0046] (2) Heat the mixture to 160°C, slowly add the base lubricating oil, stir at a speed of 800 r / min for 100 minutes, and then cool to room temperature to obtain the product.

[0047] Example 2

[0048] This embodiment provides a composite solid lubricant for a sprocket shaft assembly, which is composed of the following raw materials in percentage by weight: 15% graphite fluoride, 1% terbium-thulium co-doped molybdenum disulfide, 1% organic graphene, 0.4% tin powder, 1% polyethylene glycol, 3% thickener (talc-modified lithium soap), and the balance as base lubricant (perfluoropolyether).

[0049] The preparation method of terbium-thulium co-doped molybdenum disulfide in this embodiment comprises the following steps:

[0050] (1) dissolving molybdenum pentachloride in a mixed solution of ethanol and deionized water, wherein the ratio of molybdenum pentachloride to ethanol to deionized water is 0.1 mol:1 L:1 L, to obtain solution A;

[0051] (2) Sodium sulfide, thulium chloride and terbium chloride are dissolved in deionized water, and the concentration of sodium sulfide in the deionized water is 0.4 mol / L after dissolution; solution A and surfactant sodium oleate are then added to disperse them evenly; the molar ratio of molybdenum pentachloride, thulium chloride, terbium chloride, sodium sulfide and sodium oleate is 1:0.1:0.1:5:4; heating to 180°C, carrying out hydrothermal reaction for 15 hours, separating, washing and drying after the reaction to obtain terbium-thulium co-doped molybdenum disulfide.

[0052] The preparation method of talc-modified lithium soap in this embodiment comprises the following steps:

[0053] (1) Add talc powder and sodium hydroxide to a 0.2 mol / L zinc chloride aqueous solution, with the ratio of sodium hydroxide, talc powder, and zinc chloride solution being 1 g:3 g:30 mL; react under ultrasonic stirring for 1 h, filter, wash, and dry to obtain modified talc powder;

[0054] (2) Modified talc and 12-hydroxystearic acid were mixed in a mass ratio of 1:3 and ball-milled at a ball-milling speed of 500 r / min for 25 h to obtain a modified talc-12-hydroxystearic acid complex;

[0055] (3) Adding the modified talc-12-hydroxystearic acid complex to a lithium hydroxide aqueous solution, wherein the mass ratio of the modified talc-12-hydroxystearic acid complex to lithium hydroxide is 13:1, and the mass concentration of lithium hydroxide in the lithium hydroxide aqueous solution is 9%; heating to 85°C, stirring for saponification reaction for 10 hours, and then heating to 220°C for dehydration to obtain talc-modified lithium soap.

[0056] This embodiment provides a method for preparing a composite solid lubricant for a sprocket shaft assembly, comprising the following steps:

[0057] (1) According to the raw material composition, terbium-thulium co-doped molybdenum disulfide, organic graphene, graphite fluoride, tin powder, polyethylene glycol and a thickener are ground and mixed uniformly, and the particle size after grinding is ≤80 μm to obtain a mixed material;

[0058] (2) Heat the mixture to 150°C, slowly add the base lubricating oil, stir at a speed of 600 r / min for 120 minutes, and then cool to room temperature to obtain the product.

[0059] Example 3

[0060] This embodiment provides a composite solid lubricant for a sprocket shaft assembly, which is composed of the following raw materials in percentage by weight: 8% graphite fluoride, 4% terbium-thulium co-doped molybdenum disulfide, 3% organic graphene, 0.1% tin powder, 11% polyethylene glycol, 7% thickener (talc-modified lithium soap), and the balance as base lubricant (perfluoropolyether).

[0061] The preparation method of terbium-thulium co-doped molybdenum disulfide in this embodiment comprises the following steps:

[0062] (1) dissolving molybdenum pentachloride in a mixed solution of ethanol and deionized water, wherein the ratio of molybdenum pentachloride to ethanol to deionized water is 0.2 mol:1 L:1 L, to obtain solution A;

[0063] (2) Sodium sulfide, thulium chloride and terbium chloride are dissolved in deionized water, and the concentration of sodium sulfide in the deionized water after dissolution is 0.6 mol / L; then solution A and surfactant sodium oleate are added to disperse them evenly; wherein, the molar ratio of molybdenum pentachloride, thulium chloride, terbium chloride, sodium sulfide and sodium oleate is 1:0.15:0.15:5.5:8; heating to 220°C, carrying out hydrothermal reaction for 10 hours, separating, washing and drying after the reaction to obtain terbium-thulium co-doped molybdenum disulfide.

[0064] The preparation method of talc-modified lithium soap in this embodiment comprises the following steps:

[0065] (1) Add talc powder and sodium hydroxide to a 0.3 mol / L zinc chloride aqueous solution, with the ratio of sodium hydroxide, talc powder, and zinc chloride solution being 1 g:5 g:50 mL; react under ultrasonic stirring for 1 h, filter, wash, and dry to obtain modified talc powder;

[0066] (2) Modified talc and 12-hydroxystearic acid were mixed in a mass ratio of 1:7 and ball-milled at a ball-milling speed of 600 r / min for 20 h to obtain a modified talc-12-hydroxystearic acid complex;

[0067] (3) Adding the modified talc-12-hydroxystearic acid complex to a lithium hydroxide aqueous solution, wherein the mass ratio of the modified talc-12-hydroxystearic acid complex to lithium hydroxide is 8:3, and the mass concentration of lithium hydroxide in the lithium hydroxide aqueous solution is 12%; heating to 100°C, stirring for saponification reaction for 20 hours, and then heating to 240°C for dehydration to obtain talc-modified lithium soap.

[0068] This embodiment provides a method for preparing a composite solid lubricant for a sprocket shaft assembly, comprising the following steps:

[0069] (1) According to the raw material composition, terbium-thulium co-doped molybdenum disulfide, organic graphene, graphite fluoride, tin powder, polyethylene glycol and a thickener are ground and mixed uniformly, and the particle size after grinding is ≤80 μm to obtain a mixed material;

[0070] (2) Heat the mixture to 160°C, slowly add the base lubricating oil, stir at a speed of 1000 r / min for 80 minutes, and then cool to room temperature to obtain the product.

[0071] Comparative Example 1

[0072] The difference between this comparative example and Example 1 is that terbium and thulium co-doped molybdenum disulfide is replaced by molybdenum disulfide.

[0073] Comparative Example 2

[0074] The difference between this comparative example and Example 1 is that thulium chloride is removed during the preparation of terbium and thulium co-doped molybdenum disulfide.

[0075] Comparative Example 3

[0076] The difference between this comparative example and Example 1 is that step (1) and step (2) in the preparation method are omitted, and the modified talc-12-hydroxystearic acid complex in step (3) is replaced by 12-hydroxystearic acid.

[0077] Comparative Example 4

[0078] The difference between this comparative example and Example 1 is that the step of preparing modified talc powder in the preparation process of talc-modified lithium soap is removed, that is, the modified talc powder is replaced by talc powder.

[0079] Test example

[0080] The properties of the lubricants obtained in Examples 1-3 and Comparative Examples 1-4 were measured, and the results are shown in Table 1.

[0081] (1) The dropping point is determined according to GB / T 3498 “Determination of the dropping point of lubricating greases over a wide temperature range”.

[0082] (2) The water spray loss (38°C, 1h) was determined according to SH / T 0109 “Determination of water spray resistance of lubricating greases”.

[0083] (3) According to SH / T 0325 “Test Method for Oxidation Stability of Lubricating Greases”, the lubricant was subjected to oxidation test (100 h) in an oxygen environment at 99°C and 758 kPa, and the degree of oxidation resistance was evaluated by the oxygen pressure drop value (oxidation stability).

[0084] (4) According to SH / T 0189 “Determination of Anti-wear Performance of Lubricating Oils”, a four-ball testing machine was used to evaluate the anti-wear performance of the steel ball by measuring the wear spot diameter under the following test conditions: load: 392 N, speed: 1200 r / min, test time: 60 min, test temperature: 75°C.

[0085] Table 1

[0086]

[0087]

[0088] According to Table 1, the high temperature resistance, oxidation resistance, wear resistance and water resistance of Examples 1-3 of the present invention are all better than those of Comparative Examples 1-4. Wherein, Comparative Example 1-2 is significantly worse than the oxidation resistance of Example 1, and the reason for analysis is that the present invention utilizes rare earth thulium and terbium to co-dope molybdenum disulfide, and thulium and terbium ions are embedded in the interlayer of molybdenum disulfide or replace molybdenum sites by electrostatic adsorption during the hydrothermal reaction, making the layered structure more compact, effectively suppressing the oxidative decomposition of molybdenum disulfide at high temperatures, with better antioxidant capacity. Comparative Examples 3-4 are significantly worse than the water resistance, thermal stability and wear resistance of Example 1, and the reason for analysis is that the present invention introduces talcum powder to modify lithium soap, and zinc ion is used to modify talcum powder. Wherein, talcum powder reacts with zinc ion under alkaline conditions, so that the interlayer spacing is expanded and the porosity is increased, the dispersibility of talcum powder is improved, and then the thermal stability and wear resistance of lubricant are improved after compounding with lithium soap, and the water resistance of lubricant is improved.

[0089] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the same. The basic principles and main features of the present invention have been described above using specific implementation schemes. Modifications or substitutions may be made based on the present invention, but such modifications or substitutions do not detract from the essence of the corresponding technical solutions from the scope of protection claimed by the present invention.

Claims

1. A composite solid lubricant for a sprocket shaft assembly, characterized in that: The invention is composed of the following raw materials in percentage by weight: 2-15% of graphite fluoride, 1-4% of terbium-thulium co-doped molybdenum disulfide, 1-3% of organic graphene, 0.07-0.4% of tin powder, 1-11% of polyethylene glycol, 1-7% of thickener, and the balance being basic lubricating oil.

2. The composite solid lubricant for a sprocket shaft assembly according to claim 1, wherein: The preparation method of terbium-thulium co-doped molybdenum disulfide comprises the following steps: (1) dissolving molybdenum pentachloride in a mixed solution of ethanol and deionized water to obtain solution A; (2) Sodium sulfide, thulium chloride and terbium chloride are dissolved in deionized water, and then solution A and sodium oleate are added, dispersed evenly and subjected to hydrothermal reaction, and separated, washed and dried after the reaction to obtain the product.

3. The composite solid lubricant for a sprocket shaft assembly according to claim 2, wherein: In the step (1), the usage ratio of molybdenum pentachloride, ethanol and deionized water is 0.1-0.2 mol:1 L:1 L.

4. The composite solid lubricant for a sprocket shaft assembly according to claim 2, wherein: In the step (2), the molar ratio of molybdenum pentachloride, thulium chloride, terbium chloride, sodium sulfide and sodium oleate is 1:(0.1-0.15):(0.1-0.15):(5-5.5):(4-8); the concentration of sodium sulfide after being dissolved in deionized water is 0.4-0.6 mol / L; the temperature of the hydrothermal reaction is 180-220° C. and the time is 10-15 hours.

5. The composite solid lubricant for a sprocket shaft assembly according to claim 1, wherein: The thickener is talc-modified lithium soap; and the base lubricant is perfluoropolyether.

6. The composite solid lubricant for a sprocket shaft assembly according to claim 5, wherein: The preparation method of the talc-modified lithium soap comprises the following steps: (1) adding talc and sodium hydroxide to a zinc chloride solution, reacting, filtering, washing, and drying to obtain modified talc; (2) mixing the modified talc and 12-hydroxystearic acid and ball-milling them to obtain a modified talc-12-hydroxystearic acid complex; (3) Adding the modified talc-12-hydroxystearic acid complex to a lithium hydroxide solution to carry out a saponification reaction, followed by dehydration to obtain the product.

7. The composite solid lubricant for a sprocket shaft assembly according to claim 6, wherein: In the step (1), the dosage ratio of sodium hydroxide, talc and zinc chloride solution is 1g:3-5g:30-50mL; the concentration of zinc chloride solution is 0.2-0.3mol / L; and the reaction time is 0.5-1h.

8. The composite solid lubricant for a sprocket shaft assembly according to claim 6, wherein: In the step (2), the mass ratio of modified talc to 12-hydroxystearic acid is 1:3-7; the ball milling speed is 500-600 r / min, and the ball milling time is 20-25 h.

9. The composite solid lubricant for a sprocket shaft assembly according to claim 6, wherein: In the step (3), the mass ratio of the modified talc-12-hydroxystearic acid complex to lithium hydroxide is 8-13:1-5; the mass concentration of the lithium hydroxide solution is 9-12%; the saponification reaction temperature is 85-100°C and the time is 10-20h; and the dehydration temperature is 220-240°C.

10. The method for preparing the composite solid lubricant for a sprocket shaft assembly according to any one of claims 1 to 9, wherein: The following steps are involved: (1) According to the raw material composition, terbium-thulium co-doped molybdenum disulfide, organic graphene, graphite fluoride, tin powder, polyethylene glycol and a thickener are mixed and ground to obtain a mixed material; (2) After heating the mixture to 150-160° C., add base lubricating oil, stir at a speed of 500-1000 r / min for 80-120 min, and then cool to room temperature to obtain the product.

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