High-bearing wear-resistant self-lubricating protective coating as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of self-lubricating protective coatings, and particularly relates to a high-bearing wear-resistant self-lubricating protective coating and a preparation method and application thereof.The high-bearing wear-resistant self-lubricating protective coating comprises a metal transition layer and a ceramic material layer which are sequentially arranged, and the ceramic material layer is provided with a plurality of pores; the porosity of the ceramic material layer is distributed in a gradient increasing mode from inside to outside in the surface normal direction of the self-lubricating protective coating, and holes of the ceramic material layer are filled with lubricating oil. The bonding strength of the self-lubricating protective coating and a base material is high, the excellent wear-resisting effect and material matching performance can be achieved, the self-lubricating protective coating can resist 10 times or more of impact of the magnetic bearing under the high-speed and high-load condition, a magnetic bearing rotating shaft and an auxiliary bearing are basically free of abrasion, meanwhile, long-time service of the self-lubricating protective coating is guaranteed, and the service life of the self-lubricating protective coating is prolonged. The toughness, microhardness and long-acting lubricating performance of the self-lubricating protective coating are guaranteed, and the self-lubricating protective coating can be repeatedly used.

Description

Technical Field

[0001] The present invention belongs to the technical field of self-lubricating protective coatings, and particularly relates to a high-load-bearing wear-resistant self-lubricating protective coating, a preparation method thereof, and an application thereof. Background Art

[0002] Magnetic bearings are a new type of high-performance bearings. Compared with traditional ball bearings, sliding bearings, and oil film bearings, magnetic bearings have no mechanical contact, and the rotor can reach a very high operating speed. They have the advantages of small mechanical wear, low energy consumption, low noise, long life, no need for lubrication, and no oil pollution. They are particularly suitable for special environments such as high speed, vacuum, and ultra-clean, and can be widely used in fields such as machining, turbomachinery, aerospace, vacuum technology, rotor dynamics characteristic identification and testing, etc. They are recognized as a very promising new type of bearing. Among them, the auxiliary bearing unit is an essential and important component during the use of magnetic bearings. When faults such as sudden power failure of the magnetic bearing, rotor instability, overload, etc. occur or when the magnetic bearing bears an impact load, the rotor of the magnetic bearing contacts the inner circle of the auxiliary bearing unit, and the rotor rotates and bears the load through the support of the auxiliary bearing unit, preventing the stator and rotor of the magnetic bearing from rubbing against each other. If the auxiliary bearing unit does not have the functions of high load-bearing and self-lubrication, when sudden power failure, rotor instability, overload, etc. occur to the magnetic bearing or when it bears an impact load, the rotor will lose its suspended state, resulting in collisions and wear between the shaft and the bearing, damaging the bearing and other related equipment. Especially under high speed and high load, the wear between the bearing shaft and the bushing of the auxiliary bearing unit (or called the auxiliary bearing) is serious, leading to the loss of dynamic balance and ultimately the failure of the entire magnetic bearing system. The wear pictures are as Figure 1 shown.

[0003] Currently, the ways to solve the above wear problems in the prior art are as follows: 1. By making holes in the part body material (such as the area of the auxiliary bearing unit in contact with the rotating shaft), and then sealing oil into the holes to form porous oil-containing lubrication. However, on the one hand, the strength of the porous metal decreases and it cannot bear high loads; on the other hand, the action of friction will cause the metal to adhere and block the further seepage of the lubricating oil in the holes.

[0004] 2. Using polymer-based oil-containing bearings represented by porous polyimide. Preparing a porous polyimide integral bearing material, and then sealing lubricating oil to achieve lubrication. But because the polyimide polymer material is the main load-bearing material, it can only bear low loads, so it cannot bear medium and high loads. During the actual test process, the polyimide bearing will be completely broken directly due to dropping.

[0005] 3. Using porous metal-based oil-containing bearings. Directly preparing a porous metal integral auxiliary bearing material, and then sealing lubricating oil to achieve lubrication. However, on the one hand, the strength of the porous metal decreases and it cannot bear high loads; on the other hand, the action of friction will cause the metal to adhere and block the further seepage of the lubricating oil in the holes.

[0006] 4. A high-strength, low-friction gasket made of organic polymer material, such as a PTFE fiber fabric gasket, is embedded inside the auxiliary bearing unit. The sliding friction between the shaft and the gasket can protect the magnetic bearing stator and rotor from colliding. The grooves set on the inner side of the support ring can be used to strengthen the contact strength between the bushing and the support ring, thereby improving the reliability of the auxiliary bearing. However, when subjected to repeated friction by external forces, fatigue will occur, leading to fiber breakage; the fibers will be easily pulled out, resulting in a loose fabric structure; slight cracks will appear on the fiber surface, causing the fibers to become brittle; the heat generated by friction will cause the fibers to melt or plastically deform, accelerating fabric wear.

[0007] 5. Plate a wear-resistant lubricating film such as MoS inside the auxiliary bearing unit. 2 But MoS 2 It starts to oxidize at 200°C (the temperature during friction will exceed 200°C), causing a sharp drop in lubrication performance and even producing abrasive particles, which will have a negative impact on the auxiliary bearing unit. Moreover, it is not effective in a humid atmosphere because molybdenum disulfide is easily affected by moisture, which affects its lubrication effect. Finally, because the coating thickness is very thin (<10 microns), the "eggshell" effect is particularly significant, and the film layer is very easy to break under high impact. The magnetic bearings of the steam turbine unit work under high-temperature saturated water vapor, and after the shaft falls, the temperature of the auxiliary bearing unit will rise to more than 200°C under high-speed friction, which cannot stably meet the conditions for repeated use.

[0008] It should be noted that this part of the present invention only provides background technology related to the present invention and does not necessarily constitute prior art or known technology. Summary of the invention

[0009] The purpose of the present invention is to overcome the defects of the prior art that the wear-resistant lubricating coating used for large-scale high-speed magnetic bearing auxiliary units is still severely worn between the magnetic bearing and the shaft sleeve of the auxiliary bearing unit under high speed and high load, and cannot meet the requirements of high load, high impact and repeated use under such conditions, and to provide a high-load and wear-resistant self-lubricating protective coating and its preparation method and application. The self-lubricating protective coating of the present invention has high bonding strength with the substrate, can achieve excellent wear resistance and material matching, can withstand more than 10 impacts of the magnetic bearing under high speed and high load, and make the rotating shaft and the auxiliary bearing itself basically wear-free. At the same time, the long-term service of the self-lubricating protective coating is guaranteed, and the toughness, microhardness and long-term lubrication performance of the self-lubricating protective coating are guaranteed, and it can be reused many times.

[0010] In order to achieve the above-mentioned objectives, in the first aspect, the present invention provides a high-load-bearing and wear-resistant self-lubricating protective coating, comprising a metal transition layer and a ceramic material layer arranged in sequence, the ceramic material layer having a plurality of pores, the porosity of the ceramic material layer being distributed in a gradient increasing manner from the inside to the outside along the surface normal direction of the self-lubricating protective coating, and the pores of the ceramic material layer are filled with lubricating oil.

[0011] In some preferred embodiments of the present invention, the porosity of the ceramic material layer is 5%-35%, and / or the ceramic material layer is oxide ceramic.

[0012] In some preferred embodiments of the present invention, the increase in porosity of the ceramic material layer satisfies that: in the surface normal direction of the self-lubricating protective coating, the absolute value of the difference between two adjacent porosities with different gradients is between 5% and 15%.

[0013] In some preferred embodiments of the present invention, the penetration depth of the lubricating oil in the ceramic material layer is 60%-100% of the thickness of the ceramic material layer.

[0014] In some preferred embodiments of the present invention, the penetration depth of the lubricating oil in the ceramic material layer is 50-300 μm.

[0015] In some preferred embodiments of the present invention, the thickness of the ceramic material layer is 50-300 μm, and the thickness of the metal transition layer is 20-60 μm.

[0016] In some preferred embodiments of the present invention, the thickness ratio of the ceramic material layer to the metal transition layer is (2.5-5):1.

[0017] In some preferred embodiments of the present invention, the material of the ceramic material layer includes at least one of aluminum oxide, titanium oxide, zirconium oxide, and chromium oxide, and / or the material of the metal transition layer is selected from MCrAlY alloy and / or aluminum alloy, M in the MCrAlY alloy is Ni, Co, Fe or any combination thereof, and the aluminum alloy includes at least one of nickel-aluminum alloy, nickel-chromium-aluminum alloy, and nickel-chromium alloy.

[0018] Further preferably, the material of the ceramic material layer is a mixture selected from aluminum oxide and titanium oxide, or a mixture selected from chromium oxide and titanium oxide.

[0019] In some preferred embodiments of the present invention, the roughness Ra of the surface of the self-lubricating protective coating is less than 0.5 μm.

[0020] In some preferred embodiments of the present invention, the average microhardness of the self-lubricating protective coating is between 400 and 900 HV. 0.3, and / or, the self-lubricating protective coating can withstand more than 10 impacts under the conditions that the magnetic bearing weight is not less than 1000kg and the rotation speed is not less than 5000rpm.

[0021] In a second aspect, the present invention provides a method for preparing a high-load-bearing and wear-resistant self-lubricating protective coating, comprising the following steps: S1, depositing a metal transition layer on the working surface of the substrate to be coated; S2. preparing a ceramic material layer having a plurality of pores outside the metal transition layer, and controlling the porosity of the ceramic material layer to be distributed in a gradient increasing manner from inside to outside along the surface normal direction of the self-lubricating protective coating; S3. Fill lubricating oil into the pores of the ceramic material layer.

[0022] In some preferred embodiments of the present invention, the ceramic material layer is prepared by thermal spraying technology, and the thermal spraying conditions include: spray distance of 80-130 mm, current of 450-650 A, voltage of 60-80 V, and substrate temperature of 100-150°C.

[0023] In some preferred embodiments of the present invention, the filling lubricating oil adopts an immersion process, and the immersion conditions include: an immersion temperature of 50-200° C., a pressure of 1-100 Pa, a single immersion time of 5-30 min, and a number of immersions of 1-5 times.

[0024] In some preferred embodiments of the present invention, the preparation method further comprises: after preparing the ceramic material layer in S2, grinding is performed so that the final roughness Ra of the coating surface is less than 0.5 μm; and then S3 is performed.

[0025] In a third aspect, the present invention provides a high-load-bearing and wear-resistant self-lubricating protective coating, which is prepared by the preparation method of the high-load-bearing and wear-resistant self-lubricating protective coating described in the second aspect.

[0026] In a fourth aspect, the present invention provides a magnetic bearing, comprising an auxiliary bearing unit, on the inner circle and / or end face of the auxiliary bearing unit in the contact area with the rotating shaft, the high-load-bearing and wear-resistant self-lubricating protective coating as described in the first aspect is provided, or the high-load-bearing and wear-resistant self-lubricating protective coating as described in the third aspect is provided.

[0027] Beneficial effects: The present invention adopts the above-mentioned technical scheme, especially by setting a ceramic material layer with a specific pore gradient increase distribution and filling the pores with lubricating oil. The ceramic material layer with a specific structure can enhance its wear resistance, and at the same time can achieve both lubrication effect and high impact and high load-bearing capacity; and a metal transition layer is set between the substrate (such as the working surface of a dense metal part) and the ceramic material layer. The metal transition layer can ensure that the self-lubricating protective coating and the substrate have excellent bonding strength, and the thermal expansion coefficient and mechanical properties of the metal transition layer match the ceramic material layer, achieving excellent wear resistance and material matching; thereby being able to withstand impacts under high speed and high load with basically no wear, while ensuring the long-term service of the self-lubricating protective coating, and ensuring the toughness, microhardness and long-term lubrication performance of the self-lubricating protective coating.

[0028] Among them, the pores of the ceramic material layer with a specific pore gradient distribution of the present invention are filled with lubricating oil to form a porous oil-containing coating. The pore gradient distribution can achieve coordinated optimization of mechanical properties and oil storage capacity, which is specifically reflected in: 1) The inner layer is a low-porosity area: the dense structure gives the coating high bonding strength (>40 MPa) and compressive strength (>1.5 GPa), effectively resisting the shear stress at the substrate-coating interface and avoiding coating peeling; 2) The outer layer is a high-porosity area: the high connected porosity provides a large oil storage capacity and significantly extends the lubricating oil replenishment cycle; 3) Gradient transition layer: the continuous gradient change of porosity can eliminate interface mutations, inhibit stress concentration, and improve the impact resistance of the coating. The porosity gradient distribution breaks through the inherent limitation of the contradiction between "oil storage and strength" in traditional uniform porous coatings through the cross-scale structural design of "sparse outside and dense inside", and realizes the multifunctional integration of lubricating oil release on demand, stress gradient dissipation, and environmental adaptation, so that the porous oil-containing coating can maintain its use effect for a long time in vacuum, high humidity, high temperature (different types of lubricating media can be selected according to environmental changes) and other environments. The self-lubricating protective coating formed by the porous oil-containing coating and the metal transition layer has a certain toughness and damage tolerance. Under the high-speed impact of the rotating shaft, it will not produce obvious cracks, peeling and other damage, and at the moment of impact, the internal lubricating oil is squeezed out to provide friction reduction. The lubricating oil can be used for a long time in the above environment without failure, and the self-lubricating protective coating can meet the drop impact of various angles at ultra-high loads of 1000kg and ultra-high speeds of 5000rpm for more than 10 times.

[0029] The preparation method of the self-lubricating protective coating of the present invention is simple and convenient to operate and has strong practicality. The ceramic material layer is preferably prepared by thermal spraying technology, which is more conducive to ensuring the high bonding strength of the self-lubricating protective coating; and the pore gradient distribution of the ceramic material layer is easy to control; and the lubricating oil can select different types of lubricating media according to environmental changes to meet the lubrication requirements in different application scenarios, and is conducive to maintaining its use effect for a long time in different environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 This is a picture showing that the sleeve of a prior art suspended rotor motor is severely worn after a single drop test at high speed and high load.

[0032] Figure 2 This is a picture showing that the sleeve of the suspended rotor motor of Example 1 of the present invention, which uses the self-lubricating protective coating of the present invention, still has no obvious wear after ten drop tests at high speed and high load.

[0033] Figure 3 This is an optical microscope image of the microscopic morphology of the self-lubricating protective coating of Example 1 of the present invention.

[0034] Figure 4 The surface morphology SEM image and element distribution map of the coating obtained after the ceramic material layer of Example 1 is impregnated with lubricating oil.

[0035] Figure 5 The cross-sectional morphology SEM image and element distribution map of the coating obtained after the ceramic material layer of Example 1 is impregnated with lubricating oil.

[0036] Figure 6 It is a curve chart of the friction coefficient test results of the pure ceramic coating and the self-lubricating protective coating of the present invention.

[0037] Figure 7 The graph is a test result graph of the coefficient of friction of the self-lubricating protective coating of the present invention after long-term friction for 10 hours. DETAILED DESCRIPTION

[0038] In the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0039] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0040] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article. Among them, the terms "optional" and "optional" all mean that they may be included or not included (or may be present or not).

[0041] In the present invention, the direction close to the metal transition layer and the inner substrate is considered as the inner side, and the opposite direction is considered as the outer side.

[0042] In the first aspect, the present invention provides a high-load-bearing and wear-resistant self-lubricating protective coating, comprising a metal transition layer and a ceramic material layer arranged in sequence, wherein the ceramic material layer has a plurality of pores, and the porosity of the ceramic material layer is distributed in a gradient increasing manner from the inside to the outside along the surface normal direction of the self-lubricating protective coating, and the pores of the ceramic material layer are filled with lubricating oil. The ceramic material layer with a gradient increasing porosity distribution has a strong bonding ability with the metal transition layer, and with the gradient distribution of the lubricating oil, it breaks through the inherent limitations of the "oil storage-strength" contradiction in the traditional uniform porous coating, and realizes the multifunctional integration of lubricating oil release on demand, stress gradient dissipation, and environmental adaptation.

[0043] In some preferred embodiments of the present invention, the porosity of the ceramic material layer is 5%-35%. Using a ceramic material layer with a suitable small range of porosity is more conducive to achieving coordinated optimization of mechanical properties and oil storage capacity.

[0044] The porosity of the ceramic material layer of the present invention is distributed in a gradient increasing manner from inside to outside along the surface normal direction of the self-lubricating protective coating, which means that the porosity of the ceramic material layer can be increasing as a whole along the surface normal direction of the self-lubricating protective coating from inside to outside, such as increasing in stages and gradients according to thickness or continuously increasing in the thickness direction, for example, the porosity of the ceramic material layer within a certain thickness can change (gradually increase) or remain unchanged, and when it remains unchanged, the porosity of the ceramic material layer of adjacent certain thickness increases relatively, and the increase can be uniform or uneven. Preferably, the porosity increases uniformly.

[0045] In some preferred embodiments of the present invention, the increase in porosity of the ceramic material layer satisfies: along the surface normal direction of the self-lubricating protective coating, the absolute value of the difference in porosity of two adjacent different gradients is 5%-15%, preferably 5%-10%, and specifically can be 5%, 6%, 7%, 8%, 9%, 10%, 12%, 15%, etc. and the range between any two values. The use of the ceramic material layer with the appropriate increase in amplitude structure is more conducive to improving the impact resistance of the coating.

[0046] In some preferred embodiments of the present invention, the penetration depth of the lubricating oil in the ceramic material layer is 60%-100% of the thickness of the ceramic material layer, and specifically, for example, it can be 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, etc., and the range between any two values, for example, it can be further preferably 85%-100%. The present invention uses lubricating oil with a suitable penetration depth ratio, which is more conducive to long-term lubrication.

[0047] In some preferred embodiments of the present invention, the penetration depth of the lubricating oil in the ceramic material layer is 50-300 μm.

[0048] The types of lubricating oils of the present invention include but are not limited to at least one of mineral lubricating oils, biological lubricating oils, synthetic lubricating oils (such as methyl silicone oil, etc.), etc., which can be selected according to the actual application scenarios with reference to the corresponding types of lubricating oils in the prior art, and can all be used in the present invention to meet the lubrication requirements in different application scenarios.

[0049] In some preferred embodiments of the present invention, the thickness of the ceramic material layer is 50-300 μm, preferably 100-300 μm.

[0050] In the present invention, preferably, the thickness of the metal transition layer is 20-60 μm.

[0051] In some preferred embodiments of the present invention, the thickness ratio of the ceramic material layer and the metal transition layer is (2.5-5): 1, more preferably (2.5-3.0): 1. The present invention uses a ceramic material layer and a metal transition layer with a suitable thickness ratio, which is more conducive to relieving the thermal stress of the metal transition layer and the ceramic material layer while ensuring the impact resistance of the coating.

[0052] In some preferred embodiments of the present invention, the ceramic material layer is oxide ceramic.

[0053] In some preferred embodiments of the present invention, the material of the ceramic material layer includes at least one of aluminum oxide, titanium oxide, zirconium oxide and chromium oxide.

[0054] Further preferably, the material of the ceramic material layer is a mixture of aluminum oxide and titanium oxide or a mixture of chromium oxide and titanium oxide. This preferred solution is more conducive to making the coating have both excellent hardness and toughness.

[0055] Further preferably, the mass proportion of titanium oxide in the ceramic material layer is 3-40wt%, which is more conducive to improving the hardness and toughness of the coating.

[0056] In some preferred embodiments of the present invention, the material of the metal transition layer is selected from MCrAlY alloy (wherein M is Ni, Co, Fe or any combination thereof) and / or aluminum alloy. Further preferably, the aluminum alloy is selected from at least one of nickel aluminum (NiAl) alloy, nickel chromium aluminum alloy, and nickel chromium (NiCr) alloy. The specific content of each component of each alloy has a wide range of options in the present invention, and can refer to the prior art, which can be used in the present invention and will not be repeated here.

[0057] In some preferred embodiments of the present invention, the roughness Ra of the surface of the self-lubricating protective coating is less than 0.5 μm. The roughness of the surface of the self-lubricating protective coating is controlled in a suitable low range, which is more conducive to the rapid formation of a lubricating oil film on the friction interface.

[0058] In some preferred embodiments of the present invention, the average microhardness of the self-lubricating protective coating is between 400 and 900 HV. 0.3 .

[0059] HV 0.3 It refers to the micro-Vickers hardness under the test load of 0.3 kgf (kilogram force).

[0060] Preferably, the self-lubricating protective coating of the present invention can withstand more than 10 impacts under the conditions that the weight of the magnetic bearing is not less than 1000kg and the speed is not less than 5000rpm. The self-lubricating protective coating of the present invention can achieve more than 10 impacts under ultra-high load and ultra-high speed without obvious wear, and has a good long-term self-lubricating effect.

[0061] In a second aspect, the present invention provides a method for preparing a high-load-bearing and wear-resistant self-lubricating protective coating, comprising the following steps: S1, depositing a metal transition layer on the working surface of the substrate to be coated; S2. preparing a ceramic material layer having a plurality of pores outside the metal transition layer, and controlling the porosity of the ceramic material layer to be distributed in a gradient increasing manner from inside to outside along the surface normal direction of the self-lubricating protective coating; S3. Fill lubricating oil into the pores of the ceramic material layer.

[0062] The method of depositing the metal transition layer in S1 can refer to the existing technology, such as using supersonic flame spraying, arc spraying, cold spraying and other technologies, which can all be used in the present invention as long as the target film layer can be obtained.

[0063] In some preferred embodiments of the present invention, the ceramic material layer is prepared by thermal spraying technology.

[0064] Further preferably, the conditions of thermal spraying include: spray distance of 80-130 mm, current of 450-650 A, voltage of 60-80 V, and substrate temperature of 100-150° C. In the present invention, the gradient distribution control of the porosity of the ceramic material layer can be achieved by regulating key parameters in the thermal spraying process, such as spray distance, current and voltage.

[0065] In some preferred embodiments of the present invention, the filling lubricating oil adopts an impregnation process. The impregnation process includes but is not limited to vacuum impregnation, hot impregnation and vacuum hot impregnation, all of which can be used in the present invention.

[0066] Further preferably, the conditions for the impregnation include: an impregnation temperature of 50-200°C, a pressure of 1-100 Pa, a single impregnation time of 5-30 min, and an impregnation frequency of 1-5 times. In the impregnation process of the present invention, the penetration depth and the amount of the lubricating oil in the ceramic material layer can be controlled by regulating the relevant parameters of the impregnation process, such as the impregnation time, temperature, and pressure.

[0067] In some preferred embodiments of the present invention, the preparation method further comprises: after preparing the ceramic material layer in S2, grinding is performed so that the final roughness Ra of the coating surface is less than 0.5 μm; and then S3 is performed. The present invention can control the thickness and surface roughness of the prepared target coating through the grinding process.

[0068] In a third aspect, the present invention provides a high-load-bearing and wear-resistant self-lubricating protective coating, which is prepared by the preparation method of the high-load-bearing and wear-resistant self-lubricating protective coating described in the second aspect. The structure and performance of the self-lubricating protective coating in the third aspect are the same as those of the self-lubricating protective coating in the first aspect, and will not be repeated here.

[0069] In a fourth aspect, the present invention provides a magnetic bearing, comprising an auxiliary bearing unit, on the inner circle and / or end face of the auxiliary bearing unit in the contact area with the rotating shaft, the high-load-bearing and wear-resistant self-lubricating protective coating as described in the first aspect is provided, or the high-load-bearing and wear-resistant self-lubricating protective coating as described in the third aspect is provided.

[0070] The self-lubricating protective coating of the present invention is particularly suitable for magnetic bearings. It has certain toughness and damage tolerance. Under the high-speed impact of a large-mass rotating shaft, it will not produce obvious cracks, peeling and other damages. At the moment of impact, the internal lubricating oil is squeezed out to provide a friction-reducing effect, and the long-term use effect is good and stable. Moreover, the lubricating oil can use different types of lubricating media according to environmental changes to meet the lubrication needs in different application scenarios, and at the same time it is beneficial to maintain its use effect for a long time in different environments.

[0071] The embodiments of the present invention are described in detail below, which are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0072] Example 1 A self-lubricating protective coating is applied to the inner circle and end surface of the auxiliary bearing unit in the magnetic bearing in the contact area with the rotating shaft (i.e., the corresponding bearing protective sleeve), and the coating method is as follows: 1. First, a metal transition layer (specifically nickel-chromium alloy) is deposited with a thickness of 30 μm.

[0073] 2. A gradient porous ceramic material layer with a thickness of 200 μm (specifically, a mixture of aluminum oxide and titanium oxide, in which titanium oxide accounts for 13wt%) is prepared by thermal spraying process. The number of pores gradually increases uniformly along the normal direction of the surface of the ceramic material layer, and the continuous change range of porosity is 5%-35% (corresponding to the minimum and maximum values). In the normal direction of the surface of the self-lubricating protective coating, the absolute value of the difference in porosity of two adjacent different gradients is 5%. The conditions of thermal spraying are: the temperature of the substrate is 120°C, the spray distance is 110 mm, the current is adjusted to 650 A, 611 A, 575 A, 541 A, 509 A, 479 A, ​​450A in sequence, and the corresponding voltage is adjusted to 80V, 76V, 73V, 70V, 66V, 63V, 60V, and the above multiple currents and corresponding voltage parameters (i.e., spraying power) are adjusted in seven gradients to achieve gradient control of porosity. In this process, a ceramic material layer with a specific pore gradient distribution is formed.

[0074] 3. Through the grinding process, the thickness and surface roughness of the corresponding coating are controlled; through the grinding process, the final roughness Ra of the coating surface is less than 0.5 μm, and the thickness of the ceramic material layer is retained at 90 μm. After calculation, the ratio of the thickness of the ceramic material layer to the metal transition layer is 3:1.

[0075] 4. Then, a vacuum impregnation process was used to fill the gradient porous ceramic material layer with lubricating oil (specifically methyl silicone oil). The vacuum impregnation conditions included: a single impregnation time of 10 minutes, an impregnation temperature of 100°C, a pressure of 30 Pa, and an impregnation number of 3 times, so as to control the penetration depth of the lubricating oil inside the coating to 90 μm. After calculation, the penetration depth was 100% of the thickness of the ceramic material layer.

[0076] The microscopic morphology of the coating obtained in Example 1 is as follows Figure 3 As shown, it can be seen that the coating is composed of a metal transition layer and a ceramic material layer, and the coating presents a typical layered structure. The prepared self-lubricating protective coating was tested and analyzed for cross-sectional morphology. The analysis results are shown in Figure 5 As shown, combined Figure 5 It can be seen that the distribution of Si elements in silicone oil shows that the coating presents a certain gradient distribution, which indicates that the number of pores in the self-lubricating protective coating is gradient distributed, that is, there are pores in the ceramic material layer and the porosity increases from the inside to the outside along the normal direction. Due to the existence of the base layer, that is, the metal transition layer, the average bonding strength of the coating after 5 tests by the universal testing machine is 42MPa, which ensures the long-term service of the coating.

[0077] The certain porosity in the coating also ensures the toughness and microhardness of the coating. The microhardness of 10 locations of the coating tested by a microhardness tester is shown in Table 1, and the average microhardness is calculated to be 659HV. 0.3 .

[0078] Table 1 Microhardness of coating

[0079] The surface morphology of the prepared self-lubricating protective coating was tested and analyzed. The analysis results are as follows: Figure 4 As shown, it can be seen that the pores on the surface of the self-lubricating protective coating are filled with lubricating oil.

[0080] The self-lubricating protective coating of the present invention is applied to the inner circle and end surface of the auxiliary bearing unit in the suspension rotor motor in the contact area with the rotating shaft (i.e., the corresponding bearing protective sleeve, referred to as the sleeve), and the self-lubricating protective coating is applied to the auxiliary bearing unit in the suspension rotor motor. After ten drop tests under ultra-high load (magnetic bearing weight 1000kg) and ultra-high speed (5000rpm), the self-lubricating protective coating is applied to the auxiliary bearing unit in the suspension rotor motor. Figure 2 As shown, it can be seen that after ten drop tests, there is still no obvious wear on the magnetic bearing shaft and the auxiliary bearing sleeve itself.

[0081] The present invention also conducted a friction performance test on the self-lubricating protective coating obtained in Example 1 having the above-mentioned microstructural characteristics. By selecting a representative friction pair material YG6 (i.e., a tungsten-cobalt hard alloy material, commercially available) to grind the target coating for 1 hour, the target coating included a pure ceramic coating not coated with lubricating oil as a comparison (i.e., no metal transition layer and no porosity gradient distribution) and a self-lubricating protective coating with a gradient distribution of lubricating oil according to the present invention. The friction coefficient COF results were as follows: Figure 6 As shown. Figure 6 It can be seen that the friction coefficient COF of the self-lubricating protective coating of the present invention is below 0.15. Compared with the friction coefficient COF of the pure ceramic coating of 0.6-0.7, the self-lubricating protective coating prepared by the present invention has better lubrication performance. At the same time, the self-lubricating protective coating of the present invention was also subjected to the same friction test for a long time of 10 hours. The friction coefficient results are as follows: Figure 7 As shown, it can be seen that the friction coefficient COF is below 0.15 and relatively stable during the whole process, indicating that the self-lubricating protective coating of the present invention has good long-term lubrication performance.

[0082] Example 2 The method is carried out with reference to Example 1, except that the gradient of the uniform increase of the porosity in the ceramic material layer is different. Specifically, in the direction of the surface normal of the self-lubricating protective coating, the absolute value of the difference between the porosities of two adjacent different gradients is 15%, and the maximum and minimum porosity in the ceramic material layer remain unchanged. The process conditions that need to be adjusted to meet the porosity setting are: the spray distance is 110 mm, the current is 650 A, 550 A, 450 A, the voltage is 80 A, 70 A, 60V, the temperature of the substrate is 120°C, and the above multiple currents and corresponding voltage parameters (i.e., spraying power) are adjusted during the process to achieve gradient control of the porosity.

[0083] Example 3 The method is carried out in accordance with Example 1, except that the porosity in the ceramic material layer increases uniformly at a constant rate, the maximum and minimum porosity values ​​change, and the porosity ranges from 5% to 25%.

[0084] Example 4 The process is carried out in accordance with Example 1, except that the penetration depth of the lubricating oil in the ceramic material layer is adjusted to 80% of the thickness of the ceramic material layer. The process conditions that need to be adjusted to meet this condition are: a single immersion time of 10 minutes, a temperature of 100°C, a pressure of 50 Pa, and a number of immersions of 1 time.

[0085] Example 5 The process is carried out in accordance with Example 1, except that the thickness of the metal transition layer is adjusted to 25 μm, and the thickness ratio of the ceramic material layer to the metal transition layer is calculated to be 3.6:1.

[0086] Comparative Example 1 The same process is carried out as in Example 1, except that no metal transition layer is provided.

[0087] Comparative Example 2 The process was carried out in accordance with Example 1, except that the porosity in the ceramic material layer was uniformly set (not incrementally set) and the porosity was 10%, and the pores were filled with lubricating oil with the same penetration depth as in Example 1. The process conditions that needed to be adjusted to meet the porosity setting were: spray distance of 110 mm, current of 611 A, voltage of 76 V, and substrate temperature of 120°C.

[0088] Test Case The coatings obtained in the above-mentioned Examples 2-5 and Comparative Examples 1-2 were subjected to the same performance tests as in Example 1, and the results are shown in Table 2. The number of impact resistances under the same ultra-high load and ultra-high speed refers to the number of times when the surfaces of the rotating shaft and the auxiliary bearing sleeve show obvious wear phenomena such as obvious coating peeling, furrowing, adhesion, etc. after multiple drop tests under the same ultra-high load and ultra-high speed, and is the average value of multiple groups of data.

[0089] Table 2 Test results of coating properties obtained from Examples 1-5 and Comparative Examples 1-2

[0090] It can be seen from the above results that, compared with the comparative example, the self-lubricating protective coating obtained by adopting the embodiment scheme of the present invention has a high bonding strength with the substrate, can achieve excellent lubrication and wear resistance effects and material matching, can withstand more than 10 impacts of the magnetic bearing under high speed and high load, and make the magnetic bearing shaft and the auxiliary bearing themselves basically wear-free. At the same time, the long-term service of the self-lubricating protective coating is guaranteed, and the toughness and microhardness of the self-lubricating protective coating are guaranteed, and it can be reused many times.

[0091] Furthermore, according to Example 1 and Examples 2-5, it can be seen that by adopting the preferred scheme of the present invention, a higher number of impact resistance times can be achieved under the same ultra-high load and ultra-high speed, which is more conducive to extending the service life of the high-power magnetic bearing.

[0092] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A high-load-bearing and wear-resistant self-lubricating protective coating, characterized in that: It comprises a metal transition layer and a ceramic material layer arranged in sequence. The ceramic material layer has a plurality of pores. The porosity of the ceramic material layer increases gradually from the inside to the outside along the surface normal direction of the self-lubricating protective coating, and the pores of the ceramic material layer are filled with lubricating oil.

2. The high-load-bearing and wear-resistant self-lubricating protective coating according to claim 1, characterized in that: The porosity of the ceramic material layer is 5%-35%, and / or the ceramic material layer is oxide ceramic.

3. The high-load-bearing, wear-resistant self-lubricating protective coating according to claim 1 or 2, characterized in that: The increase in porosity of the ceramic material layer satisfies that: in the surface normal direction of the self-lubricating protective coating, the absolute value of the difference in porosity of two adjacent different gradients is between 5% and 15%.

4. The high-load-bearing and wear-resistant self-lubricating protective coating according to claim 1, characterized in that: The penetration depth of the lubricating oil in the ceramic material layer is 60%-100% of the thickness of the ceramic material layer; and / or, The penetration depth of the lubricant in the ceramic material layer is 50-300µm.

5. The high-load-bearing and wear-resistant self-lubricating protective coating according to claim 1, characterized in that: The thickness of the ceramic material layer is 50-300 μm, and the thickness of the metal transition layer is 20-60 μm; and / or, The thickness ratio of the ceramic material layer and the metal transition layer is (2.5-5):

1.

6. The high-load-bearing and wear-resistant self-lubricating protective coating according to claim 1, characterized in that: The material of the ceramic material layer includes at least one of aluminum oxide, titanium oxide, zirconium oxide and chromium oxide; and / or, The material of the metal transition layer is selected from MCrAlY alloy and / or aluminum alloy, M in the MCrAlY alloy is Ni, Co, Fe or any combination thereof, and the aluminum alloy includes at least one of nickel-aluminum alloy, nickel-chromium-aluminum alloy and nickel-chromium alloy.

7. The high-load-bearing and wear-resistant self-lubricating protective coating according to claim 1, characterized in that: The material of the ceramic material layer is selected from a mixture of aluminum oxide and titanium oxide or a mixture of chromium oxide and titanium oxide, and / or the roughness Ra of the surface of the self-lubricating protective coating is lower than 0.5 μm.

8. The high-load-bearing and wear-resistant self-lubricating protective coating according to claim 1, characterized in that: The average microhardness of the self-lubricating protective coating is 400-900HV 0.3 , and / or, the self-lubricating protective coating can withstand more than 10 impacts under the conditions that the magnetic bearing weight is not less than 1000kg and the rotation speed is not less than 5000rpm.

9. A method for preparing a high-load-bearing and wear-resistant self-lubricating protective coating, characterized in that: The steps include: S1, depositing a metal transition layer on the working surface of the substrate to be coated; S2. preparing a ceramic material layer having a plurality of pores outside the metal transition layer, and controlling the porosity of the ceramic material layer to be distributed in a gradient increasing manner from inside to outside along the surface normal direction of the self-lubricating protective coating; S3. Fill lubricating oil into the pores of the ceramic material layer.

10. The method for preparing a high-load-bearing and wear-resistant self-lubricating protective coating according to claim 9, characterized in that: The ceramic material layer is prepared by thermal spraying technology, and the thermal spraying conditions include: spray distance of 80-130 mm, current of 450-650A, voltage of 60-80 V, and substrate temperature of 100-150°C; and / or, The filling lubricating oil adopts an impregnation process, and the impregnation conditions include: an impregnation temperature of 50-200°C, a pressure of 1-100 Pa, a single impregnation time of 5-30 minutes, and an impregnation number of 1-5 times.

11. The method for preparing a high-load-bearing and wear-resistant self-lubricating protective coating according to claim 9, characterized in that: The preparation method further includes: after preparing the ceramic material layer in S2, grinding is performed so that the final roughness Ra of the coating surface is less than 0.5 μm; and then S3 is performed.

12. A high-load-bearing and wear-resistant self-lubricating protective coating, characterized in that: The coating is prepared by the method for preparing a high-load-bearing, wear-resistant self-lubricating protective coating as described in any one of claims 9 to 11.

13. A magnetic bearing, comprising an auxiliary bearing unit, characterized in that: A high-load-bearing, wear-resistant, self-lubricating protective coating as described in any one of claims 1 to 8 is provided on the inner circle and / or end face of the auxiliary bearing unit in the contact area with the rotating shaft, or a high-load-bearing, wear-resistant, self-lubricating protective coating as described in claim 12 is provided.

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