A gallium-based liquid metal grease-like lubricant, a preparation method and application thereof, and a lubricating system

Abstract

The present application relates to the technical field of lubricant, in particular to a gallium-based liquid metal greasy lubricant, a preparation method and application thereof, and a lubricating system, and provides a gallium-based liquid metal greasy lubricant, according to mass percentage, elements of gallium-based liquid metal for preparing the gallium-based liquid metal greasy lubricant include 70-72% of gallium, 14-16% of indium, 12-14% of tin and 0.8-1.2% of zinc; viscosity value of the gallium-based liquid metal greasy lubricant is greater than or equal to 6.0*10 6 mPa*s when shear rate approaches 0. The gallium-based liquid metal greasy lubricant is applied to a space atomic oxygen irradiation environment, and friction coefficient and wear rate of a friction pair do not change obviously before irradiation, that is, the gallium-based liquid metal greasy lubricant does not fail in the space atomic oxygen irradiation environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lubricants, in particular to a gallium-based liquid metal grease-like lubricant, a preparation method and application thereof, and a lubrication system. BACKGROUND

[0002] Space liquid lubricants mainly include synthetic lubricating oils represented by perfluoropolyether, polyalphaolefin, polyalkylated cyclopentane, polysiloxane, etc., and are widely used in spacecraft motion mechanisms. However, the space environment has a significant impact on the performance and service life of lubricating oils. Typical space environmental factors mainly include ultrahigh vacuum, solar ultraviolet, atomic oxygen erosion, charged particle irradiation, high-low temperature alternation, and debris dust, etc.

[0003] Atomic oxygen irradiation is a unique space environment in low earth orbit (200-700 km), which is generated by the photodissociation of oxygen under the irradiation of solar ultraviolet with a wavelength less than 243 nm. The relative speed between atomic oxygen and on-orbit spacecraft is 7-8 km·s, the atomic oxygen flux density can reach 10 13 ~ 10 15 atoms / (cm 2 ·s), and the average impact energy can reach 4-5 eV. At the same time, atomic oxygen has higher chemical activity than molecular oxygen, which can cause the chemical bond rupture and oxidation of organic molecules in space lubricating oils, resulting in the decline of lubricating performance, and even failure.

[0004] Currently, the methods for improving the atomic oxygen irradiation resistance of space lubricating oils mainly include two types. One is to change the molecular structure of organic matter in lubricating oils, and to modify or graft Si-containing components. The bond energy of C-F bond is higher than that of C-C bond and C-Si bond, so the new fluorine-containing trisilane lubricating oil molecule with 3,3,3-trifluoropropyl substituent grafted with C-F bond is more stable, and is not easy to break under the action of atomic oxygen irradiation, and has better atomic oxygen irradiation resistance (Chemical Letters 2014, 43: 1578-1580). The other is to compound other organic matters which are more prone to bond rupture and oxidation in lubricating oils. Chinese invention patent CN202311274917.6 compounds modified POSS additives in polyalkylated cyclopentane base oil, and the ring structure of the modified POSS additives will break under the action of space atomic oxygen irradiation, which can reduce the damage of atomic oxygen irradiation to the molecular structure of base oil, and indirectly protect the structural stability of base oil, thereby playing a role in resisting atomic oxygen irradiation. Although both methods can slow down the deterioration rate of lubricating oils under atomic oxygen irradiation, there is still a risk of deterioration and failure under long-term irradiation. SUMMARY

[0005] Therefore, the present application aims to provide a gallium-based liquid metal grease-like lubricant, a preparation method and application thereof, and a lubricating system.

[0006] The present application provides a gallium-based liquid metal grease-like lubricant, and elements of a gallium-based liquid metal used for preparing the gallium-based liquid metal grease-like lubricant include 70-72% of gallium, 14-16% of indium, 12-14% of tin, and 0.8-1.2% of zinc in terms of mass percentage.

[0007] The viscosity value of the gallium-based liquid metal grease-like lubricant is greater than or equal to 6.0*10 6 mPa·s when the shearing rate approaches 0.

[0008] Preferably, elements of the gallium-based liquid metal used for preparing the gallium-based liquid metal grease-like lubricant include 71% of gallium, 15% of indium, 13% of tin, and 1% of zinc in terms of mass percentage.

[0009] The present application also provides a preparation method of the gallium-based liquid metal grease-like lubricant, including the following steps.

[0010] The metal elements used for preparing the gallium-based liquid metal are mixed, and then subjected to a melting treatment in a protective atmosphere to obtain the gallium-based liquid metal.

[0011] The gallium-based liquid metal is stirred in an atmospheric environment to obtain the gallium-based liquid metal grease-like lubricant.

[0012] Preferably, the melting treatment is performed in a protective atmosphere.

[0013] The protective atmosphere is an argon atmosphere.

[0014] Preferably, the temperature of the melting treatment is 500-600°C, and the time is 1.5-2h.

[0015] Preferably, the stirring speed is 200-600rpm, and the temperature is 20-80°C.

[0016] Preferably, the metal elements used for preparing the gallium-based liquid metal include gallium blocks, indium wires with a length of 1-3mm, tin wires with a length of 1-3mm, and zinc wires with a length of 1-3mm.

[0017] The purity of the metal elements used for preparing the gallium-based liquid metal is greater than 99.99%.

[0018] Preferably, the mixing comprises melting the gallium block and mixing with the indium wire of 1-3mm in length, the tin wire of 1-3mm in length and the zinc wire of 1-3mm in length.

[0019] The application further provides application of the gallium-based liquid metal greasy lubricant or the gallium-based liquid metal greasy lubricant prepared by the preparation method in the lubrication field in a space atomic oxygen irradiation environment.

[0020] The application further provides a lubrication system suitable for a space atomic oxygen irradiation environment, comprising a gallium-based liquid metal greasy lubricant and a friction pair.

[0021] The material of the friction pair comprises an iron-based alloy, a nickel-based alloy or a titanium alloy.

[0022] The gallium-based liquid metal greasy lubricant is the gallium-based liquid metal greasy lubricant or the gallium-based liquid metal greasy lubricant prepared by the preparation method.

[0023] The application further provides a gallium-based liquid metal greasy lubricant, wherein elements of a gallium-based liquid metal used for preparing the gallium-based liquid metal greasy lubricant comprise 70-72% of gallium, 14-16% of indium, 12-14% of tin and 0.8-1.2% of zinc in terms of mass percentage; and the gallium-based liquid metal greasy lubricant has a viscosity value of ≥6.0*10 6 mPa·s when a shearing rate approaches 0. Since the gallium-based liquid metal greasy lubricant provides lubrication by adsorbing to generate a gallium-rich film on a friction interface in a friction process, the indium and the tin do not participate in the friction process basically. In addition, under the action of space atomic oxygen irradiation, the three elements of gallium, indium and tin mainly oxidize gallium, and the indium and the tin are precipitated to form solid particles, which can damage the lubrication to a certain extent. Meanwhile, the unit price of the indium wire of 1mm in diameter and 99.99% in purity is 4500 yuan / kg, the unit price of the gallium block of 99.99% in purity is 4000 yuan / kg, the unit price of the tin wire of 1mm in diameter and 99.99% in purity is 1300 yuan / kg, and the unit price of the zinc wire of 1mm in diameter and 99.99% in purity is 800 yuan / kg, so the unit price of the indium is relatively high, and the unit prices of the tin and the zinc are relatively low. Further, since the main role of the indium and the tin is to reduce the melting point of the gallium-based liquid metal, the indium and the tin are indispensable, and the gallium-based liquid metal with a small amount of zinc element has a lower melting point, so the lubricant with a lower melting point is more suitable for application in the scenario of the cold-hot alternating temperature change in the low earth orbit space environment. Therefore, the gallium-based liquid metal in the application is more suitable for application in the low earth orbit space environment than the conventional gallium-based liquid metal (Ga 75.5 In 24.5 (wt.%) binary eutectic alloy and Ga 68.5 In 21.5 Sn10 (wt.%) ternary eutectic alloy), reduces the amount of indium, increases the amount of tin, and increases zinc (reduces melting point), while taking into account the lubricating performance and cost; further, the gallium-based liquid metal is stirred in air to obtain a greasy lubricant, which can exhibit excellent lubricating performance on the surface of the friction pair, does not have the problems of crawling and leakage in a space microgravity environment, and can further reduce the amount of lubricant and greatly save the use cost.

[0024] The application provides application of the gallium-based liquid metal greasy lubricant in the lubricating field in a space atomic oxygen irradiation environment.

[0025] The application further provides a lubricating system suitable for a space atomic oxygen irradiation environment, which comprises the gallium-based liquid metal greasy lubricant and a friction pair; the material of the friction pair comprises an iron-based alloy, a nickel-based alloy or a titanium alloy. The gallium-based liquid metal greasy lubricant does not corrode the above-mentioned friction pair materials. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The friction coefficient curves of the gallium-based liquid metal greasy lubricant described in Embodiment 1 before and after atomic oxygen irradiation for lubricating a 9Cr18 steel ball / 9Cr18 steel disc friction pair and the wear rate of the 9Cr18 steel disc;

[0027] Figure 2 The actual photos and spreading conditions on the surface of a 9Cr18 steel disc of the gallium-based liquid metal, the insufficiently oxidized gallium-based liquid metal and the fully oxidized gallium-based liquid metal greasy lubricant described in Embodiment 1;

[0028] Figure 3 The viscosity change curves of the fully oxidized gallium-based liquid metal greasy lubricant and the insufficiently oxidized gallium-based liquid metal described in Embodiment 1 with the shear rate and the viscosity values when the shear rate approaches 0;

[0029] Figure 4The friction coefficient curve of the gallium-based liquid metal grease lubricant described in Comparative Example 1 before and after atomic oxygen irradiation lubricating a 9Cr18 steel ball / CuSn6 copper alloy disc friction pair and the wear rate of the CuSn6 copper alloy disc;

[0030] Figure 5 The friction coefficient curve of the space lubricating oil poly-alpha olefin (PAO) described in Comparative Example 3 before and after atomic oxygen irradiation lubricating a 9Cr18 steel ball / 9Cr18 steel disc friction pair and the wear rate of the 9Cr18 steel disc. DETAILED DESCRIPTION

[0031] The gallium-based liquid metal grease lubricant provided by the application is prepared from a gallium-based liquid metal, and the elements of the gallium-based liquid metal include 70-72% gallium, 14-16% indium, 12-14% tin and 0.8-1.2% zinc in terms of mass percentage.

[0032] The viscosity value of the gallium-based liquid metal grease lubricant is greater than or equal to 6.0*10 6 mPa·s when the shear rate approaches 0.

[0033] In the application, the elements of the gallium-based liquid metal used to prepare the gallium-based liquid metal grease lubricant more preferably include 71% gallium, 15% indium, 13% tin and 1% zinc, or 71.5% gallium, 14% indium, 13.3% tin and 1.2% zinc, or 70% gallium, 15% indium, 13.9% tin and 1.1% zinc in terms of mass percentage.

[0034] In the application, the gallium-based liquid metal grease lubricant can exhibit more excellent lubricating performance on the surface of a friction pair and does not have the problems of crawling and leakage in a space microgravity environment, and can further reduce the amount of lubricant used and greatly save the use cost.

[0035] The application further provides a preparation method of the gallium-based liquid metal grease lubricant.

[0036] The metal elements used to prepare the gallium-based liquid metal grease lubricant are mixed, and then subjected to smelting treatment in a protective atmosphere to obtain the gallium-based liquid metal.

[0037] The gallium-based liquid metal is stirred in an atmospheric environment to obtain the gallium-based liquid metal grease lubricant.

[0038] The metal elements used to prepare the gallium-based liquid metal grease lubricant are mixed, and then subjected to smelting treatment in a protective atmosphere to obtain the gallium-based liquid metal.

[0039] In the present application, the metal elements for preparing the gallium-based liquid metal are preferably gallium metal element, indium metal element, tin metal element and zinc metal element; the gallium metal element is preferably gallium block, the indium metal element is preferably indium wire with a length of 1-3 mm and a diameter of 1 mm, the tin metal element is preferably tin wire with a length of 1-3 mm and a diameter of 1 mm, and the zinc metal element is preferably zinc wire with a length of 1-3 mm and a diameter of 1 mm. In the present application, the purity of the gallium metal element, the indium metal element, the tin metal element and the zinc metal element is preferably greater than 99.99%.

[0040] In the present application, the mixing preferably comprises mixing the gallium metal element with the indium metal element, the tin metal element and the zinc metal element after melting the gallium metal element. In the present application, the melting preferably comprises placing a container containing gallium block into hot water for melting, and the present application does not have any special limitation on the temperature of the hot water, which is only required to be greater than the melting point of the gallium metal element.

[0041] In the present application, the protective atmosphere is preferably argon atmosphere.

[0042] In the present application, the temperature of the smelting treatment is preferably 500-600℃, and more preferably 500-550℃; and the holding time is preferably 1.5-2h, and more preferably 1.6-1.8h. In the present application, the smelting treatment preferably comprises placing the mixed mixture into an alumina crucible, and then placing the alumina crucible into a tube furnace under argon protection.

[0043] After the smelting treatment is completed, the present application further preferably comprises cooling, and the present application does not have any special limitation on the process of the cooling, which can be performed by using the process well known to those skilled in the art. In the embodiments of the present application, the cooling can be furnace cooling.

[0044] After the gallium-based liquid metal is obtained, the present application stirs the gallium-based liquid metal in an atmospheric environment to obtain the gallium-based liquid metal grease lubricant.

[0045] In the present application, the stirring speed is preferably 200-600rpm, and more preferably 400-600rpm; and the temperature is preferably 20-80℃, and more preferably 30-60℃. The present application does not have any special limitation on the time of the stirring, which can be the time well known to those skilled in the art to ensure that the gallium-based liquid metal grease lubricant with a viscosity value greater than or equal to 6.0×10 6 mPa·s at a shear rate close to 0 can be obtained.

[0046] The present application also provides a gallium-based liquid metal grease lubricant for use in the lubrication field in a space atomic oxygen irradiation environment.

[0047] The application also provides a lubricating system suitable for space atomic oxygen irradiation environment, comprising a gallium-based liquid metal grease lubricant and a friction pair.

[0048] The material of the friction pair comprises an iron-based alloy, a nickel-based alloy or a titanium alloy.

[0049] In the application, the material of the friction pair comprises an iron-based alloy, a nickel-based alloy or a titanium alloy; the iron-based alloy preferably comprises 9Cr18; the nickel-based alloy preferably comprises Inconel718; and the titanium alloy preferably comprises TC4. In the embodiments of the application, the material of the friction pair can be 9Cr18 steel / 9Cr18 steel (the upper friction pair is a 9Cr18 steel ball and the lower friction pair is a 9Cr18 steel disc), 9Cr18 steel / Inconel718 nickel-based alloy (the upper friction pair is a 9Cr18 steel ball and the lower friction pair is an Inconel718 nickel-based alloy disc) or 9Cr18 steel / TC4 titanium alloy (the upper friction pair is a 9Cr18 steel ball and the lower friction pair is a TC4 titanium alloy disc).

[0050] The technical solutions in the application will be described clearly and completely below in combination with the embodiments in the application. Obviously, the described embodiments are only some of the embodiments of the application, but not all the embodiments. Based on the embodiments in the application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0051] Embodiment 1

[0052] A container containing gallium blocks with a purity of 99.99% is put into hot water to melt the gallium blocks, and indium wires, tin wires and zinc wires with a purity of 99.99% and a diameter of 1 mm are cut into short wires with a length of 1-3 mm, weighed according to a mass ratio of 71:15:13:1, mixed, and then subjected to smelting treatment in an argon atmosphere, at a temperature of 500 ℃ and for a holding time of 1.6 h, and then sealed after cooling to room temperature in the furnace to obtain gallium-based liquid metal Ga 71 In 15 Sn 13 Zn1.

[0053] Then, the gallium-based liquid metal is stirred by a magnetic stirrer in an atmospheric environment, at a stirring speed of 550 rpm, a stirring temperature of 25 ℃ and for a time of 0.5 h, to obtain a gallium-based liquid metal grease lubricant (denoted as Ga 6 In 71 Sn 15 Zn1-Grease) with a viscosity of 6.6×10 13 mPa·s.

[0054] The friction pair material lubricated by the gallium-based liquid metal grease-like lubricant was 9Cr18 steel / 9Cr18 steel. The upper friction pair was a 9Cr18 steel ball with a diameter of 6 mm, and the lower friction pair was a 9Cr18 steel disc with a diameter of 30 mm and a height of 8 mm. The friction coefficient of the 9Cr18 steel / 9Cr18 steel friction pair and the wear rate of the 9Cr18 steel disc before and after atomic oxygen irradiation were investigated.

[0055] Example 2

[0056] A container containing gallium blocks with a purity of 99.99% was placed in hot water to melt the gallium blocks. In addition, indium wires, tin wires, and zinc wires with a purity of 99.99% and a diameter of 1 mm were cut into short wires with a length of 1-3 mm. The short wires were weighed according to a mass ratio of 71.5:14:13.3:1.2, and then the metal elements were mixed and subjected to a melting treatment in an argon atmosphere at a temperature of 520°C for 1.7 h. After cooling to room temperature in the furnace, the gallium-based liquid metal Ga 71.5 In 14 Sn 13.3 Zn 1.2 .

[0057] The gallium-based liquid metal was then stirred in an atmospheric environment using a magnetic stirrer at a stirring speed of 580 rpm and a stirring temperature of 28°C for 0.55 h. A gallium-based liquid metal grease-like lubricant with a viscosity of 6.8×10 6 mPa·s was obtained (denoted as Ga 71.5 In 14 Sn 13.3 Zn 1.2 -Grease).

[0058] The friction pair material lubricated by the gallium-based liquid metal grease-like lubricant was 9Cr18 steel / Inconel718 nickel-based alloy. The upper friction pair was a 9Cr18 steel ball with a diameter of 6 mm, and the lower friction pair was an Inconel718 nickel-based alloy disc with a diameter of 30 mm and a height of 8 mm. The friction coefficient of the 9Cr18 steel / Inconel718 nickel-based alloy friction pair and the wear rate of the Inconel718 nickel-based alloy disc were investigated.

[0059] Example 3

[0060] A container containing gallium blocks with a purity of 99.99% was placed in hot water to melt the gallium blocks. In addition, indium wires, tin wires, and zinc wires with a purity of 99.99% and a diameter of 1 mm were cut into short wires with a length of 1-3 mm. The short wires were weighed according to a mass ratio of 71.5:14:13.3:1.2, and then the metal elements were mixed and subjected to a melting treatment in an argon atmosphere at a temperature of 520°C for 1.7 h. After cooling to room temperature in the furnace, the gallium-based liquid metal Ga 70 In15 Sn 13.9 Zn 1.1 .

[0061] Then the gallium-based liquid metal is stirred in an atmospheric environment using a magnetic stirrer, the stirring speed is 600 rpm, the stirring temperature is 30℃, and the time is 0.52h, to obtain a gallium-based liquid metal grease-like lubricant (denoted as Ga 6 mPa·s (denoted as Ga 70 In 15 Sn 13.9 Zn 1.1 -Grease) with a viscosity of 6.7×10

[0062] The material of the friction pair lubricated by the gallium-based liquid metal grease-like lubricant is 9Cr18 steel / TC4 titanium alloy. The upper friction pair is a 9Cr18 steel ball with a diameter of 6mm, and the lower friction pair is a TC4 titanium alloy disc with a diameter of 30mm and a height of 8mm. The friction coefficient of the 9Cr18 steel / TC4 titanium alloy friction pair and the wear rate of the TC4 titanium alloy disc are investigated.

[0063] Comparative Example 1

[0064] The difference from Example 1 is that the material of the friction pair lubricated by the gallium-based liquid metal grease-like lubricant is 9Cr18 steel / CuSn6 copper alloy. The upper friction pair is a 9Cr18 steel ball with a diameter of 6mm, and the lower friction pair is a CuSn6 copper alloy disc with a diameter of 30mm and a height of 8mm. The friction coefficient of the 9Cr18 steel / CuSn6 copper alloy friction pair and the wear rate of the CuSn6 copper alloy disc are investigated.

[0065] Comparative Example 2

[0066] The difference from Example 1 is that the material of the friction pair lubricated by the gallium-based liquid metal grease-like lubricant is 9Cr18 steel / Al7075 aluminum alloy. The upper friction pair is a 9Cr18 steel ball with a diameter of 6mm, and the lower friction pair is an Al7075 aluminum alloy disc with a diameter of 30mm and a height of 8mm. The friction coefficient of the 9Cr18 steel / Al7075 aluminum alloy friction pair and the wear rate of the Al7075 aluminum alloy disc are investigated.

[0067] Comparative Example 3

[0068] The space lubricating oil polyalphaolefin (PAO) is used as a lubricant, and the material of the friction pair is 9Cr18 steel / 9Cr18 steel. The upper friction pair is a 9Cr18 steel ball with a diameter of 6mm, and the lower friction pair is a 9Cr18 steel disc with a diameter of 30mm and a height of 8mm. The friction coefficient of the 9Cr18 steel / 9Cr18 steel friction pair and the wear rate of the 9Cr18 steel disc are investigated.

[0069] Comparative Example 4

[0070] The space lubricant perfluoropolyether (PFPE) was used as lubricant, and the material of friction pair was 9Cr18 steel / 9Cr18 steel. The upper friction pair was a 9Cr18 steel ball with a diameter of 6 mm, and the lower friction pair was a 9Cr18 steel disc with a diameter of 30 mm and a height of 8 mm. The friction coefficient of the 9Cr18 steel / 9Cr18 steel friction pair and the wear rate of the 9Cr18 steel disc were investigated.

[0071] Test Example

[0072] The lubricating properties of the gallium-based liquid metal grease lubricants described in Examples 1 to 3 and the lubricants described in Comparative Examples 1 to 3 were tested before and after atomic oxygen irradiation, and the specific experimental conditions were as follows:

[0073] 1) Lubricant performance test before atomic oxygen irradiation: The lubricant was spread on the surface of the lower friction pair to a certain thickness, and the vacuum friction and wear test machine was used to test the lubricating behavior of the lubricant before atomic oxygen irradiation. The test parameters were: vacuum degree was 3.0 x 10 -2 Pa, normal load was 5 N, disc rotation speed was 200 rpm, friction time was 1 h, and friction radius was 5 mm. The vacuum friction and wear test machine automatically recorded the friction coefficient of the friction pair. The wear volume of the disc was measured by a non-contact surface profilometer, and the wear rate was calculated by dividing the wear volume by the normal load and the sliding distance.

[0074] 2) Lubricant performance test after atomic oxygen irradiation: The lubricant was spread on the surface of the friction pair to a certain thickness, and first, the simulated space atomic oxygen irradiation device was used to irradiate the lubricant with atomic oxygen. The vacuum degree of the simulated irradiation device was 3.0 x 10 - 2 Pa, the average impact energy of atomic oxygen irradiation was 5.0 eV, the flux was 18 x 10 15 atoms / (cm 2 ·s), the irradiation time was 1 hour, and the corresponding atomic oxygen irradiation dose was 6.48 x 10 19 atoms / cm 2 . Then, the vacuum friction and wear test machine was used to test the lubricating behavior of the lubricant after atomic oxygen irradiation. The test parameters were: vacuum degree was 3.0 x 10 -2 Pa, normal load was 5 N, disc rotation speed was 200 rpm, friction time was 1 h, and friction radius was 5 mm. The vacuum friction and wear test machine automatically recorded the friction coefficient of the friction pair. The wear volume of the disc was measured by a non-contact surface profilometer, and the wear rate was calculated by dividing the wear volume by the normal load and the sliding distance.

[0075] The test results are shown in Table 1 and Figures 1 to 5 . Figure 1The friction coefficient curves (a) and the wear rate (b) of the gallium-based liquid metal fatty lubricant described in Example 1 before and after atomic oxygen irradiation lubricating the 9Cr18 steel / 9Cr18 steel friction pair and the 9Cr18 steel disc are shown in the following figure: Figure 1 It can be seen that the average friction coefficient of the gallium-based liquid metal fatty lubricant lubricating the 9Cr18 steel / 9Cr18 steel friction pair before atomic oxygen irradiation is 0.26, and the wear rate of the 9Cr18 steel disc is (1.43±0.21)×10 -6 mm 3 / N·m; the average friction coefficient of the gallium-based liquid metal fatty lubricant lubricating the 9Cr18 steel / 9Cr18 steel friction pair after atomic oxygen irradiation is 0.30, and the wear rate of the 9Cr18 steel disc is (2.99±1.05)×10 -6 mm 3 / N·m. The atomic oxygen irradiation has little effect on the gallium-based liquid metal fatty lubricant lubricating the 9Cr18 steel / 9Cr18 steel friction pair, the average friction coefficient does not increase significantly, and the wear rate remains in the order of 10 -6 mm 3 / N·m.

[0076] Figure 2 The physical pictures and spreading on the surface of the 9Cr18 steel disc of the gallium-based liquid metal, the insufficiently oxidized gallium-based liquid metal fatty lubricant (insufficiently oxidized condition is that the viscosity value is less than 6.0×10 6 mPa·s when the shear rate approaches 0) and the fully oxidized gallium-based liquid metal fatty lubricant (fully oxidized condition is that the viscosity value is greater than or equal to 6.0×10 6 mPa·s when the shear rate approaches 0) described in Example 1 are shown in the following figure: Figure 2 It can be seen that the gallium-based liquid metal exhibits metallic luster and has fluidity, and does not wet the surface of the 9Cr18 steel disc; the insufficiently oxidized gallium-based liquid metal is composed of solid gallium oxide, indium / tin precipitates and liquid gallium-based liquid metal, has a certain fluidity, and the wettability on the surface of the 9Cr18 steel disc is improved to a certain extent, but the gallium-based liquid metal still exists and cannot completely wet the 9Cr18 steel; and the fully oxidized gallium-based liquid metal fatty lubricant exhibits a viscous state, the viscosity is greatly increased, loses fluidity, is composed of a large amount of gallium oxide, indium / tin precipitates and a small amount of gallium-based liquid metal wrapped inside, and can completely wet the 9Cr18 steel. The fully oxidized gallium-based liquid metal fatty lubricant can exhibit more excellent lubricating performance on the surface of the friction pair and will not have the problems of crawling and leakage in the space microgravity environment, and on the other hand can further reduce the amount of lubricant used and greatly save the use cost.

[0077] Figure 3The viscosity of the fully oxidized gallium-based liquid metal grease and the insufficiently oxidized gallium-based liquid metal as described in Example 1 changes with the shear rate (a) and the viscosity value when the shear rate approaches 0 (b). The results are shown in Table 1. Figure 3 It can be seen that the viscosity of the fully oxidized gallium-based liquid metal grease and the insufficiently oxidized gallium-based liquid metal both have the shear thinning characteristics, the viscosity value is the largest when the shear rate approaches 0, and the viscosity gradually decreases with the increase of the shear rate, and then tends to be stable. The viscosity value of the fully oxidized gallium-based liquid metal grease is 6.6 x 10 6 mPa·s, and has no flowability; the viscosity value of the insufficiently oxidized gallium-based liquid metal is 9.1 x 10 5 mPa·s, and has certain flowability.

[0078] Figure 4 The friction coefficient curve (a) and the wear rate of the CuSn6 copper alloy disc (b) of the gallium-based liquid metal grease as described in Comparative Example 1 lubricating the 9Cr18 steel / CuSn6 copper alloy friction pair before and after atomic oxygen irradiation are shown in Table 2. Figure 4 It can be seen that the average friction coefficient of the gallium-based liquid metal grease lubricating the 9Cr18 steel / CuSn6 copper alloy friction pair before atomic oxygen irradiation is 0.27, and the wear rate of the CuSn6 disc is (5.17 ± 0.91) x 10 -4 mm 3 / N·m; the average friction coefficient of the gallium-based liquid metal grease lubricating the 9Cr18 steel / CuSn6 copper alloy friction pair after atomic oxygen irradiation is 0.28, and the wear rate of the CuSn6 disc is (8.37 ± 0.43) x 10 -4 mm 3 / N·m. Compared with the wear rate of the 9Cr18 steel disc in Example 1, the wear rate of the CuSn6 copper alloy disc is increased by 2 orders of magnitude, because gallium has a strong corrosion effect on copper alloy at room temperature, and generates CuGa2 intermetallic compound, and in the process of friction, there is a synergistic effect between corrosion and friction, the friction has a destructive effect on the surface of the copper alloy, enhances the contact between gallium and copper, greatly accelerates the corrosion speed, and the corrosion product CuGa2 is easy to fall off under the action of friction, and the fresh copper alloy exposed will continue to corrode, so the wear rate of the CuSn6 disc is significantly increased.

[0079] Figure 5 The friction coefficient curve (a) and the wear rate of the 9Cr18 steel disc (b) of the space lubricating oil polyalphaolefin (PAO) as described in Comparative Example 3 lubricating the 9Cr18 steel / 9Cr18 steel disc friction pair before and after atomic oxygen irradiation are shown in Table 3. Figure 5It can be seen that the average friction coefficient of poly-alpha olefin (PAO) lubricating 9Cr18 steel / 9Cr18 steel friction pair before atomic oxygen irradiation is 0.11, and the wear rate of 9Cr18 disc is (2.74±0.54)×10 -7 mm 3 / N·m; the average friction coefficient of poly-alpha olefin (PAO) lubricating 9Cr18 steel / 9Cr18 steel friction pair after atomic oxygen irradiation is 0.45, and the wear rate of 9Cr18 disc is (1.43±0.33)×10 -6 mm 3 / N·m. It can be seen that the average friction coefficient of poly-alpha olefin (PAO) lubricating 9Cr18 steel / 9Cr18 steel friction pair after atomic oxygen irradiation increases obviously, and the wear rate of 9Cr18 disc increases by one order of magnitude, which is mainly due to the fact that the atomic oxygen irradiation causes the breakage and cross-linking of poly-alpha olefin (PAO) molecules, so that the poly-alpha olefin (PAO) lubrication fails, resulting in high friction and high wear.

[0080] Table 1 Lubricating properties of gallium-based liquid metal grease lubricants described in examples 1-3 and lubricants described in comparative examples 1-3 before and after atomic oxygen irradiation

[0081]

[0082] It can be seen from Table 1 that whether the gallium-based liquid metal grease lubricant is subjected to atomic oxygen irradiation or not, the friction coefficient and wear rate do not increase obviously when the gallium-based liquid metal grease lubricant lubricates 9Cr18 steel / 9Cr18 steel, 9Cr18 steel / Inconel718 nickel-based alloy and 9Cr18 steel / TC4 titanium alloy friction pairs, and a low shear stress gallium-rich film is formed at the friction interface to provide lubrication. It can be seen that the gallium-based liquid metal grease lubricant and the lubrication system composed of iron-based alloy, nickel-based alloy and titanium alloy will not fail under the action of atomic oxygen irradiation, and can be effectively applied to the atomic oxygen irradiation environment.

[0083] When the gallium-based liquid metal grease lubricant lubricates 9Cr18 steel / CuSn6 copper alloy and 9Cr18 steel / Al7075 aluminum alloy friction pairs, the gallium-based liquid metal grease lubricant will corrode the copper alloy and aluminum alloy, and there is a synergistic effect between corrosion and friction in the friction process, resulting in an order of magnitude increase in the wear rate of CuSn6 and Al7075 discs. Therefore, the friction pair materials of the lubrication system are not suitable for copper alloy and aluminum alloy.

[0084] For space commonly used lubricating oil polyalphaolefin (PAO) and perfluoropolyether (PFPE) lubrication 9Cr18 steel / 9Cr18 steel, atomic oxygen irradiation can destroy the molecular structure of lubricating oil, resulting in broken bond and crosslinking, thus causing lubrication failure, the friction coefficient and wear rate will increase significantly. After atomic oxygen irradiation, the average friction coefficient of 9Cr18 steel / 9Cr18 steel lubricated by polyalphaolefin (PAO) increases by 309.09%, and the wear rate of 9Cr18 steel disc increases by 421.59%; After atomic oxygen irradiation, the average friction coefficient of 9Cr18 steel / 9Cr18 steel lubricated by perfluoropolyether (PFPE) increases by 183.33%, and the wear rate of 9Cr18 steel disc increases by 727.16%.

[0085] The above only describes the preferred embodiments of the present application, and does not limit the present application in any form. It should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which should also be considered as the protection scope of the present application.

Claims

1. A lubrication system suitable for space atomic oxygen irradiation environment, characterized in that: including a gallium-based liquid metal grease lubricant and a friction pair; The material of the friction pair includes iron-based alloy, nickel-based alloy or titanium alloy; The gallium-based liquid metal grease lubricant comprises, in terms of mass percentage, 70-72% gallium, 14-16% indium, 12-14% tin, and 0.8-1.2% zinc in the gallium-based liquid metal used to prepare the gallium-based liquid metal grease lubricant. The viscosity of the gallium-based liquid metal grease lubricant is ≥6.0×10 6 mPa·s; The preparation method of the gallium-based liquid metal grease lubricant comprises the following steps: After mixing the metal elements for preparing the gallium-based liquid metal grease lubricant, smelting the mixture in a protective atmosphere to obtain the gallium-based liquid metal; The gallium-based liquid metal is stirred in an atmospheric environment to obtain the gallium-based liquid metal grease lubricant.

2. The lubrication system according to claim 1, wherein: Calculated by mass percentage, the elements of the gallium-based liquid metal used to prepare the gallium-based liquid metal grease lubricant include 71% gallium, 15% indium, 13% tin and 1% zinc.

3. The lubrication system according to claim 1, wherein: The smelting process is carried out in a protective atmosphere; The protective atmosphere is argon atmosphere.

4. The lubrication system according to claim 1 or 3, characterized in that: The smelting treatment is performed at a temperature of 500-600°C and for a time of 1.5-2 h.

5. The lubrication system according to claim 1, wherein: The stirring speed is 200-600 rpm and the temperature is 20-80°C.

6. The lubrication system according to claim 1, wherein: The metal element for preparing the gallium-based liquid metal includes a gallium block, an indium wire with a length of 1 to 3 mm, a tin wire with a length of 1 to 3 mm, and a zinc wire with a length of 1 to 3 mm; The purity of the metal element used to prepare the gallium-based liquid metal is greater than 99.99%.

7. The lubrication system according to claim 1 or 6, characterized in that: The mixing comprises melting the gallium block and mixing it with an indium wire with a length of 1 to 3 mm, a tin wire with a length of 1 to 3 mm, and a zinc wire with a length of 1 to 3 mm.

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