Water-based lubricating fluid and method for realizing super lubrication

Abstract

The invention discloses a water-based lubricating fluid. The water-based lubricating fluid comprises deionized water and an ionic compound, the concentration of the ionic compound is 1-10 mol / L; positive ions of the ionic compound are selected from any one of lithium ions, sodium ions, iron ions and aluminum ions. The invention further discloses a method for achieving super lubrication, and the method comprises the steps that the surface of a friction pair is coated with the water-based lubricating liquid, and super lubrication is achieved after running-in; the friction conditions are as follows: the load is 2-5N, the temperature is 20-25 DEG C, the rotating speed is 100-250r / min, and the friction time is greater than or equal to 10s; and the friction pair is selected from any one of silicon nitride / silicon dioxide, silicon nitride / sapphire and silicon nitride / steel.

Description

Technical Field

[0001] The invention belongs to the field of lubricating fluids, and in particular relates to a water-based lubricating fluid and a method for achieving superlubrication. Background Art

[0002] Nowadays, with the continuous development of science and technology, the utilization rate of large machines and precision machinery is getting higher and higher, which greatly facilitates our lives. However, due to the existence of friction and wear, it not only consumes a lot of resources and causes pollution, but also reduces the operating efficiency of the machinery. Nowadays, oil-based lubricants are mainly used in industrial production and mechanical equipment operation. They are cheap and have excellent performance, but they consume a lot of energy in the production and preparation process and contain a large amount of phosphorus, sulfur, chlorine and other elements, which cause serious pollution to the environment. Moreover, its lubrication performance is poor (friction coefficient is greater than 0.1), which cannot meet the requirements of high-end precision equipment, and cannot effectively remove the heat during operation.

[0003] The preparation process of water-based lubricants is simple and environmentally friendly, and they have excellent lubrication properties. Since there is a low-shear free water layer sliding interface during the friction process, the friction coefficient is reduced, which greatly reduces the economic losses and energy consumption caused by the friction and wear of mechanical equipment, allowing some precision mechanical equipment to operate stably and well. For example, satellite solar telescopic panel slides, mechanical hard disk head needles, micro gears, and precision machine tool guides. Therefore, water-based lubricants are a very critical component for mechanical equipment and are indispensable. If a lubricant that is easy to prepare and has an extremely low friction coefficient can be obtained, the friction and wear of mechanical equipment can be reduced and the service life of the machine can be extended.

[0004] However, the water-based lubricants widely used at present still have the problems of cumbersome preparation, high friction coefficient and poor anti-friction and anti-wear performance. For example, the patent with patent number CN02145978.9 discloses a water-based lubricant and preparation method, which has the advantages of easy dispersion in water and easy extension into film, but also has the disadvantages of too many components and cumbersome preparation. Another example is the patent with patent number CN201310205488.7, which discloses a water-based lubricant for mechanical transmission, which has the advantages of good lubrication performance, no harm to the human body and can be absorbed by the human body, but also has the disadvantages of many preparation processes, long time consumption, uncontrollable cost, etc., which greatly restricts its large-scale production and use. Summary of the invention

[0005] Based on the above technical problems, the present invention provides a water-based lubricating liquid, which has few components and a simple preparation method, and can achieve macroscopic superlubrication through component selection and concentration adjustment.

[0006] The specific scheme of the present invention is as follows:

[0007] One of the objectives of the present invention is to provide an aqueous lubricant, comprising: deionized water and an ionic compound; the concentration of the ionic compound is 1 - 10 mol / L; the cation of the ionic compound is selected from any one of lithium ion, sodium ion, iron ion, and aluminum ion.

[0008] Preferably, the ionic compound is selected from any one of lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium nitrate, sodium hexafluoroantimonate, ferrous chloride, and aluminum chloride.

[0009] Preferably, the concentration of the ionic compound is 5 - 10 mol / L.

[0010] Preferably, the ionic compound is lithium bis(trifluoromethanesulfonyl)imide and the concentration of the ionic compound is 10 mol / L.

[0011] The components of the aqueous lubricant provided by the present invention include deionized water and an ionic compound, and the composition is simple; during application, the aqueous lubricant contains a sufficiently solvated cationic hydration shell, and there is a low-shear slip interface in the weak interaction region between the cationic hydration shell and free water, which can effectively reduce the shear resistance and provide a certain load-bearing capacity, playing a role in reducing friction and wear. Thus, the obtained lubricant has excellent tribological properties.

[0012] The present invention adjusts the concentration of the ionic compound in the aqueous lubricant to change the tribological properties of the lubricant. At high concentrations, especially when lithium bis(trifluoromethanesulfonyl)imide is used as the ionic compound and the concentration is 10 mol / L, the friction coefficient can be stably maintained below 0.01, achieving macroscopic superlubrication. In fact, not any ionic compound can achieve superlubrication through concentration adjustment. Most soluble salts belong to ionic crystals and break ionic bonds when dissolved in water; the greater the lattice energy, the greater the energy required to break the bonds when dissolved in water, so it is more difficult to dissolve in water. The CF3SO2 – group in the structure of lithium bis(trifluoromethanesulfonyl)imide has a strong electron-withdrawing effect, which intensifies the delocalization of negative charges and reduces ionic association pairing, making the ionic compound have a high solubility.

[0013] The preparation method of the aqueous lubricant of the present invention is not specifically limited. For example, using a conventional preparation method, the components are mixed, heated and stirred for 0.5 - 2 h, and ultrasonicated for 1 - 30 min to form a homogeneous and stable liquid.

[0014] Another objective of the present invention is to provide a method for achieving superlubrication, comprising: coating the above aqueous lubricant on the surface of a friction pair, and achieving superlubrication after running-in; the friction conditions include: a load of 2 - 5 N, a temperature of 20 - 25 °C, a rotational speed of 100 - 250 r / min, and a friction time ≥ 10 s; the friction pair is selected from any one of silicon nitride / silica, silicon nitride / sapphire, and silicon nitride / steel.

[0015] Preferably, the water-based lubricant is composed of deionized water and lithium bis(trifluoromethanesulfonyl)imide; the concentration of lithium bis(trifluoromethanesulfonyl)imide is 10 mol / L.

[0016] Preferably, the friction conditions include: a load of 2 N, a temperature of 20 - 25 °C, a rotational speed of 250 r / min, a friction time of ≥10 s; the friction pair is silicon nitride / silica.

[0017] When the water-based lubricant with lithium ions as cations is used for the silicon nitride / silica friction pair, during the friction process, a silica gel layer is formed on the surface of the friction pair, thereby adsorbing solvated Li + ions, providing load-carrying capacity, effectively inhibiting the direct contact between the friction pairs, and playing a role in reducing friction and wear; while the weak interaction region between the free water and the outermost layer water of the Li + ion hydration shell becomes an ultra-low shear sliding interface, reducing the friction coefficient. The resulting high-concentration water-based ionic compound lubricant has excellent tribological properties. When the friction pair is changed to silicon nitride / sapphire or silicon nitride / steel, since a silica gel layer cannot be formed to adsorb ions and provide part of the load-bearing effect, the friction coefficient is relatively high.

[0018] The beneficial effects of the present invention are as follows:

[0019] (1) The water-based lubricant provided by the present invention uses ionic compounds as anti-wear components, which helps to form a hydrated cation shell structure with a low shear slip interface during the friction process, plays a good lubricating role for the friction pair, and can effectively reduce the friction and wear of the friction pair;

[0020] (2) The preparation process of the lubricant of the present invention is simple. When the water molecules evaporate completely, the ionic compounds can be recovered and reused, which is suitable for large-scale industrial production;

[0021] (3) The present invention also provides a method for achieving superlubrication using the water-based lubricant. When the high-concentration water-based lubricant is used for the silicon nitride / silica friction pair, the friction coefficient can be stably maintained at 0.006, achieving macroscopic superlubrication. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the curve of the friction coefficient of the water-based lubricant described in Example 1 changing with time;

[0023] Figure 2 is the curve of the friction coefficient of the water-based lubricant described in Example 2 changing with time;

[0024] Figure 3 is the curve of the friction coefficient of the water-based lubricant described in Example 3 changing with time;

[0025] Figure 4 It is the change curve of the friction coefficient of the aqueous lubricant described in Example 4 over time;

[0026] Figure 5 It is the change curve of the friction coefficient of the aqueous lubricant described in Example 5 over time;

[0027] Figure 6 It is the change curve of the friction coefficient of the aqueous lubricant described in Example 6 over time;

[0028] Figure 7 It is the change curve of the friction coefficient of the aqueous lubricant described in Example 7 over time;

[0029] Figure 8 It is the change curve of the friction coefficient of the aqueous lubricant described in Example 8 over time;

[0030] Figure 9 It is the change curve of the friction coefficient of the aqueous lubricant described in Example 9 over time;

[0031] Figure 10 It is the change curve of the friction coefficient of the aqueous lubricant described in Example 10 over time. Detailed implementation manners

[0032] Next, the technical solutions of the present invention will be described in detail through specific examples. However, it should be clearly stated that these examples are for illustrative purposes only and are not construed as limiting the scope of the present invention.

[0033] The preparation method of the aqueous lubricant described in the following examples is as follows: Mix the ionic compound and deionized water in proportion, heat and stir, and sonicate to form a homogeneous and stable liquid.

[0034] The change curves of the friction coefficients of the following Examples 1-8 over time were all obtained through the following method: Use a high-temperature friction and wear testing machine (MPX-3G), with the upper specimen being a silicon nitride ball and the lower specimen being silicon dioxide. Drop the lubricant onto the lower specimen and conduct friction testing under the conditions of a load of 2 N, a temperature of 25 °C, a rotation speed of 250 r / min, and a friction radius of 5 mm.

[0035] Example 1

[0036] An aqueous lubricant, comprising: deionized water and an ionic compound; the ionic compound is lithium bis(trifluoromethanesulfonyl)imide, accounting for 74.4% of the lubricant, that is, 10 mol·L -1 .

[0037] A method for achieving superlubricity includes: coating the water-based lubricant described in this embodiment on the surface of the friction pair, and achieving superlubricity after running-in; the friction conditions include: a load of 2 N, a temperature of 25 °C, a rotational speed of 250 r / min, and a friction time ≥ 10 s; the friction pair is silicon nitride / silicon dioxide. Using a high-temperature friction and wear testing machine (MPX-3G), friction tests are carried out under these conditions, the friction radius is 5 mm, and the variation curve of the friction coefficient with time is as Figure 1 shown.

[0038] It can be seen that the running-in time is extremely short, only 10 s, and the friction coefficient can be stably maintained at about 0.006, indicating that the water-based lubricant described in this embodiment has the ability to quickly achieve superlubricity.

[0039] Example 2

[0040] A water-based lubricant includes: deionized water and an ionic compound; the ionic compound is sodium hexafluoroantimonate, accounting for 27.8% of the lubricant, that is, 1.5 mol·L -1 .

[0041] The variation curve of the friction coefficient of the lubricant described in this embodiment with time is as Figure 2 shown. It can be seen that the initial value of the friction coefficient is greater than 0.25, and then it continuously decreases. After running-in for a period of time, it can be stably maintained below 0.01, but it rises sharply after 1800 seconds, indicating that although this lubricant has a low friction coefficient and can achieve superlubricity under certain conditions, its lubrication life is poor.

[0042] Example 3

[0043] A water-based lubricant includes: deionized water and an ionic compound; the ionic compound is ferrous chloride, accounting for 12.1% of the lubricant, that is, 1.1 mol·L -1 .

[0044] The variation curve of the friction coefficient of the lubricant described in this embodiment with time is as Figure 3 shown. It can be seen that the friction coefficient is stably maintained at about 0.115.

[0045] Example 4

[0046] A water-based lubricant includes: deionized water and an ionic compound; the ionic compound is aluminum chloride, accounting for 39.9% of the lubricant, that is, 5 mol·L -1 .

[0047] The variation curve of the friction coefficient of the lubricant described in this embodiment with time is as Figure 4 shown. It can be seen that the friction coefficient rises slowly and is basically stable at about 0.089.

[0048] Example 5

[0049] An aqueous lubricating fluid, comprising: deionized water and an ionic compound; the ionic compound is lithium bis(trifluoromethanesulfonyl)imide, accounting for 22.2% of the lubricating fluid, i.e., 1 mol·L -1 .

[0050] The variation curve of the friction coefficient of the lubricating fluid in this example with time is as Figure 5 shown. It can be seen that the friction coefficient is basically stable at about 0.235.

[0051] Example 6

[0052] An aqueous lubricating fluid, comprising: deionized water and an ionic compound; the ionic compound is lithium bis(trifluoromethanesulfonyl)imide, accounting for 58.9% of the lubricating fluid, i.e., 5 mol·L -1 .

[0053] The variation curve of the friction coefficient of the lubricating fluid in this example with time is as Figure 6 shown. It can be seen that the average friction coefficient is 0.117 and finally stabilizes at 0.034.

[0054] Example 7

[0055] An aqueous lubricating fluid, comprising: deionized water and an ionic compound; the ionic compound is lithium hexafluorophosphate, accounting for 60.1% of the lubricating fluid, i.e., 1 mol·L -1 .

[0056] The variation curve of the friction coefficient of the lubricating fluid in this example with time is as Figure 7 shown. It can be seen that the friction coefficient is basically stable at about 0.334.

[0057] Example 8

[0058] An aqueous lubricating fluid, comprising: deionized water and an ionic compound; the ionic compound is lithium nitrate, accounting for 40.8% of the lubricating fluid, i.e., 1 mol·L -1 .

[0059] The variation curve of the friction coefficient of the lubricating fluid in this example with time is as Figure 8 shown. It can be seen that the friction coefficient is basically stable at about 0.341.

[0060] From the comparison of Example 5 with Example 7 and 8, it can be obtained that for lithium hexafluorophosphate and lithium nitrate with the same concentration of 1 mol·L -1 , their average friction coefficients are 0.334 and 0.341, which are greater than that of lithium bis(trifluoromethanesulfonyl)imide with a concentration of 1 mol·L -1 . There is the same amount of Li in the three solutions+ , at this time, the type of anion affects the stability of the hydration shell of Li + , indicating that compared with hexafluorophosphate anions and nitrate anions, bis(trifluoromethanesulfonyl)imide anions have better binding properties with the Li + hydration shell, making the hydration shell more stable, thus providing a stable low-shear slip interface, and therefore reducing the friction coefficient and achieving the effect of friction reduction and wear resistance.

[0061] Examples 9 - 10

[0062] This example explores the application of the water-based lubricant described in Example 1 on different friction pairs: (1) silicon nitride / sapphire (Example 9); (2) silicon nitride / steel (Example 10). The curve of the friction coefficient changing with time is tested. The specific method is only different from the methods described in Examples 1 - 8 in that the lower specimens are replaced with sapphire and steel respectively, and other parameters remain unchanged. The test results are shown in Figure 9 and 10 respectively.

[0063] It can be seen from Figure 9 that the friction coefficient drops from 0.201 at the beginning to 0.113 after 2 minutes and then stabilizes, but it is still far from superlubricity. It can be seen from Figure 10 that the friction coefficient rises from 0.052 to 0.098 and then stabilizes, and the lubrication effect is average. This is because when using silicon nitride / sapphire and silicon nitride / steel as friction pairs, it is impossible to generate a silica gel layer on the friction surface during the friction process like the silicon nitride / silica friction pair, and adsorb the solvated Li + ions to play a role in load-bearing and friction reduction.

[0064] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A water-based lubricant, characterized in that, Comprising: Deionized water and an ionic compound; the concentration of the ionic compound is 1-10 mol / L; the cation of the ionic compound is selected from any one of lithium ion, sodium ion, iron ion, and aluminum ion.

2. The water-based lubricating fluid according to claim 1, wherein, The ionic compound is selected from any one of lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium nitrate, sodium hexafluoroantimonate, ferrous chloride, and aluminum chloride.

3. The water-based lubricating fluid according to claim 1 or 2, characterized in that, The concentration of the ionic compound is 5-10 mol / L.

4. The aqueous lubricating fluid according to any one of claims 1-3, characterized in that, The ionic compound is lithium bis(trifluoromethanesulfonyl)imide, and the concentration of the ionic compound is 10 mol / L.

5. A method for achieving superlubricity, characterized in that, Comprising: Coating the water-based lubricant according to any one of claims 1-4 on the surface of the friction pair, and achieving superlubricity after running-in; the friction conditions include: a load of 2-5 N, a temperature of 20-25 °C, a rotational speed of 100-250 r / min, and a friction time ≥ 10 s; The friction pair is selected from any one of silicon nitride / silica, silicon nitride / sapphire, and silicon nitride / steel.

6. The method for achieving superlubricity according to claim 5, characterized in that, The water-based lubricant is composed of deionized water and lithium bis(trifluoromethanesulfonyl)imide; the concentration of lithium bis(trifluoromethanesulfonyl)imide is 10 mol / L.

7. The method for achieving superlubricity according to claim 5 or 6, characterized in that, The friction conditions include: a load of 2 N, a temperature of 20-25 °C, a rotational speed of 250 r / min, and a friction time ≥ 10 s; the friction pair is silicon nitride / silica.

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