A high-load-bearing wear-resistant self-lubricating protective coating, its preparation method and application

Abstract

The present invention belongs to the technical field of self-lubricating protective coatings, and specifically relates to a high-load-bearing and wear-resistant self-lubricating protective coating, its preparation method, and application, 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 self-lubricating protective coating of the present invention has a 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 makes the magnetic bearing shaft and auxiliary bearing itself basically wear-free. At the same time, it ensures the long-term service of the self-lubricating protective coating, ensures the toughness, microhardness, and long-term lubrication performance of the self-lubricating protective coating, and can be reused many times.

Description

Technical Field

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

[0002] Magnetic bearings are a new type of high-performance bearing. Compared with traditional ball bearings, sliding bearings, and oil film bearings, magnetic bearings have no mechanical contact, and the rotor can reach very high operating speeds. They have the advantages of low mechanical wear, low energy consumption, low noise, long life, no lubrication, and no oil pollution. They are particularly suitable for special environments such as high speed, vacuum, and ultra-clean environments. They can be widely used in mechanical processing, turbomachinery, aerospace, vacuum technology, rotor dynamics characteristics identification and testing, and are recognized as a very promising new type of bearing. Among them, the auxiliary bearing unit is an indispensable and important component in the use of magnetic bearings. When the magnetic bearing suddenly loses power, the rotor loses stability, is overloaded, or is subjected to impact loads, the magnetic bearing rotor contacts the inner circle of the auxiliary bearing unit, supporting the rotor's rotation and bearing the load through the auxiliary bearing unit, preventing friction between the stator and rotor of the magnetic bearing. If the auxiliary bearing unit does not have high load-bearing and self-lubricating functions, when the magnetic bearing suddenly experiences power outages, rotor instability, overload or other faults, or is subjected to impact loads, the rotor will lose its suspension state, causing collision and wear between the shaft and bearing, damaging the bearing and other related equipment. In particular, under high speed and high load, the wear between the bearing shaft and the shaft sleeve of the auxiliary bearing unit (or auxiliary bearing) is severe, resulting in dynamic balance instability and ultimately causing the entire magnetic bearing system to fail. Wear pictures are shown below. Figure 1 shown.

[0003] At present, the existing technologies for solving the above-mentioned wear problem include:

[0004] 1. By creating holes in the part's base material (such as the area in contact with the shaft in the auxiliary bearing unit) and then sealing in oil, porous oil-containing lubrication is achieved. However, on the one hand, the porous metal loses strength and cannot withstand high loads; on the other hand, friction causes the metal to adhere, preventing further leakage of the lubricant in the hole.

[0005] 2. Use polymer-based oil-containing bearings, such as porous polyimide. A porous polyimide bearing material is prepared as a single piece and then enclosed in lubricating oil for lubrication. However, because the polyimide polymer is the primary load-bearing material, it can only withstand low loads and is unable to withstand medium or high loads. During actual testing, a drop can directly cause the polyimide bearing to completely break.

[0006] 3. Use porous metal-based oil-containing bearings. Directly prepare the porous metal integral auxiliary bearing material and then seal it with lubricating oil for lubrication. However, on the one hand, the porous metal's strength decreases, making it unable to withstand high loads; on the other hand, friction causes the metal to adhere, preventing further leakage of lubricating oil from the pores.

[0007] 4. A high-strength, low-friction gasket made of an 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 protects the magnetic bearing stator and rotor from colliding. The grooves on the inner side of the support ring can be used to strengthen the contact strength between the bushing and the support ring, improving the reliability of the auxiliary bearing. However, when subjected to repeated friction by external forces, fatigue will occur, causing fiber breakage; fibers can be easily pulled out, resulting in a loose fabric structure; slight cracks in the fiber surface make the fiber brittle; and the heat generated by friction can cause the fiber to melt or undergo plastic deformation, accelerating fabric wear.

[0008] 5. Coating the auxiliary bearing unit with a wear-resistant lubricating film, such as MoS2. However, MoS2 begins to oxidize at 200°C (temperatures exceeding 200°C during friction), causing a sharp decline in lubrication performance and even generating abrasive particles, negatively impacting the auxiliary bearing unit. Furthermore, it performs poorly in humid atmospheres, as molybdenum disulfide is easily affected by moisture, which compromises its lubrication effectiveness. Finally, because the coating is very thin (less than 10 microns), the "eggshell" effect is particularly pronounced, making the film easily shattered under high impact. Steam turbine magnetic bearings operate in high-temperature saturated steam. Furthermore, if the shaft falls, the auxiliary bearing unit can heat up to over 200°C due to high-speed friction, making it unreliable for repeated use.

[0009] 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 public known technology. Summary of the Invention

[0010] The purpose of the present invention is to overcome the defects of the prior art in that the wear-resistant lubricating coating used for large-scale high-speed magnetic bearing auxiliary units still suffers severe wear 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. A high-load and wear-resistant self-lubricating protective coating and its preparation method and application are provided. 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 makes 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.

[0011] 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 being filled with lubricating oil.

[0012] 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.

[0013] In some preferred embodiments of the present invention, the increase in porosity of the ceramic material layer satisfies the following requirement: along the surface normal direction of the self-lubricating protective coating, the absolute value of the difference in porosity between two adjacent layers with different gradients is between 5% and 15%.

[0014] 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.

[0015] In some preferred embodiments of the present invention, the penetration depth of the lubricating oil in the ceramic material layer is 50-300 μm.

[0016] 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.

[0017] 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.

[0018] 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 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.

[0019] Further preferably, the material of the ceramic material layer is selected from a mixture of aluminum oxide and titanium oxide, or is selected from a mixture of chromium oxide and titanium oxide.

[0020] In some preferred embodiments of the present invention, the surface roughness Ra of the self-lubricating protective coating is less than 0.5 μm.

[0021] In some preferred embodiments of the present invention, the average microhardness of the self-lubricating protective coating is 400-900 HV 0.3, and / or, the self-lubricating protective coating can withstand more than 10 impacts under the conditions that the magnetic bearing weighs not less than 1000kg and the rotation speed is not less than 5000rpm.

[0022] In a second aspect, the present invention provides a method for preparing a high-load-bearing, wear-resistant, self-lubricating protective coating, comprising the following steps:

[0023] S1, depositing a metal transition layer on the working surface of the substrate to be coated;

[0024] 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 increase gradually from the inside to the outside along the surface normal direction of the self-lubricating protective coating;

[0025] S3. Filling the pores of the ceramic material layer with lubricating oil.

[0026] 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.

[0027] In some preferred embodiments of the present invention, the filling lubricating oil adopts an immersion process, and the immersion conditions include: immersion temperature of 50-200° C., pressure of 1-100 Pa, single immersion time of 5-30 min, and immersion times of 1-5 times.

[0028] In some preferred embodiments of the present invention, the preparation method further comprises: after preparing the ceramic material layer in S2, grinding is performed to make the final roughness Ra of the coating surface less than 0.5 μm; and then performing S3.

[0029] In a third aspect, the present invention provides a high-load-bearing, wear-resistant, self-lubricating protective coating, which is prepared by the preparation method of the high-load-bearing, wear-resistant, self-lubricating protective coating described in the second aspect.

[0030] 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 described in the first aspect is provided, or the high-load-bearing and wear-resistant self-lubricating protective coating described in the third aspect is provided.

[0031] Beneficial effects:

[0032] The present invention adopts the above-mentioned technical scheme, especially 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 those of 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.

[0033] 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, significantly extending 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, through a cross-scale structural design characterized by a "sparse exterior and dense interior," overcomes the inherent "oil storage-strength" trade-off inherent in conventional uniformly porous coatings. This design achieves multifunctional integration, including on-demand lubricant release, stress gradient dissipation, and environmental adaptability. This allows the porous oil-containing coating to maintain its long-term performance in environments such as vacuum, high humidity, and high temperature (different lubricating media can be selected based on environmental conditions). The self-lubricating protective coating formed by the porous oil-containing coating and the metallic transition layer exhibits a high degree of toughness and damage tolerance, resisting significant cracking and flaking under high-speed impacts from rotating shafts. Furthermore, at the moment of impact, the internal lubricant is expelled, providing friction reduction. This lubricant can withstand prolonged use in these environments without failure, and the self-lubricating protective coating can withstand over 10 drops at various angles at an ultra-high load of 1000 kg and a rotational speed of 5000 rpm.

[0034] The method for preparing the self-lubricating protective coating of the present invention is simple, convenient, and highly practical. The ceramic material layer is preferably prepared by thermal spraying technology, which is more conducive to ensuring high bonding strength of the self-lubricating protective coating. The pore gradient distribution of the ceramic material layer is also easily controlled. Furthermore, the lubricating oil can be selected from different types of lubricating media according to environmental changes to meet the lubrication requirements of different application scenarios, while also facilitating long-term maintenance of its performance in various environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 This is a picture of the existing technology's suspended rotor motor showing severe sleeve wear after a single drop test at high speed and high load.

[0037] 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.

[0038] 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.

[0039] Figure 4 Surface morphology SEM image and element distribution map of the coating obtained after the ceramic material layer of Example 1 was impregnated with lubricating oil.

[0040] Figure 5 The cross-sectional morphology SEM image and element distribution diagram of the coating obtained after the ceramic material layer of Example 1 was impregnated with lubricating oil.

[0041] Figure 6 The graph is a test result graph of the friction coefficient of the pure ceramic coating and the self-lubricating protective coating of the present invention.

[0042] Figure 7 This is a graph showing the test results of the coefficient of friction of the self-lubricating protective coating of the present invention after 10 hours of long-term friction. DETAILED DESCRIPTION

[0043] In the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0044] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0045] The endpoints of the ranges and any values 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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein. The terms "optional" and "optional" both mean that a range may or may not be included (or may or may not be present).

[0046] 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.

[0047] In its first aspect, the present invention provides a high-load-bearing, wear-resistant, self-lubricating protective coating comprising a metal transition layer and a ceramic material layer disposed sequentially. The ceramic material layer has a plurality of pores, and the porosity of the ceramic material layer is distributed in a gradient increasing from the inside out along the surface normal of the self-lubricating protective coating. The pores of the ceramic material layer are filled with lubricating oil. The ceramic material layer with a gradient increasing porosity exhibits strong bonding with the metal transition layer. Combined with the gradient distribution of the lubricating oil, this overcomes the inherent "oil storage-strength" contradiction inherent in conventional uniformly porous coatings, achieving multifunctional integration such as on-demand lubricant release, stress gradient dissipation, and environmental adaptability.

[0048] In some preferred embodiments of the present invention, the porosity of the ceramic material layer is between 5% and 35%. Using a ceramic material layer with a suitable small porosity range is more conducive to achieving synergistic optimization of mechanical properties and oil storage capacity.

[0049] The porosity of the ceramic material layer of the present invention is distributed in a gradient increasing pattern from the inside out along the surface normal of the self-lubricating protective coating. This means that the porosity of the ceramic material layer can exhibit an overall increasing trend along the surface normal of the self-lubricating protective coating from the inside out. For example, the porosity can increase gradually in stages and thicknesses, or continuously increase along the thickness direction. For example, the porosity of a ceramic material layer within a certain thickness can change (gradually increase) or remain unchanged. When the porosity remains unchanged, the porosity of adjacent ceramic material layers of a certain thickness increases relatively. The magnitude of the increase can be uniform or non-uniform. A uniform increase in porosity is preferred.

[0050] In some preferred embodiments of the present invention, the porosity of the ceramic material layer is increased to such an extent that, along the surface normal of the self-lubricating protective coating, the absolute difference between two adjacent porosities with different porosity gradients is between 5% and 15%, preferably between 5% and 10%. Specifically, for example, the difference may be between 5%, 6%, 7%, 8%, 9%, 10%, 12%, 15%, or any range between these two values. Using this ceramic material layer with a suitable increase in porosity structure further enhances the impact resistance of the coating.

[0051] 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, can be 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, or any range between two values, and more preferably, 85%-100%. The present invention uses a lubricating oil with an appropriate penetration depth, which is more conducive to long-term lubrication.

[0052] In some preferred embodiments of the present invention, the penetration depth of the lubricating oil in the ceramic material layer is 50-300 μm.

[0053] The types of lubricants of the present invention include, but are not limited to, at least one of mineral lubricants, bio-lubricants, synthetic lubricants (such as methyl silicone oil, etc.), etc., which can be selected according to the actual application scenario with reference to the corresponding types of lubricants in the prior art, and can all be used in the present invention to meet the lubrication requirements in different application scenarios.

[0054] In some preferred embodiments of the present invention, the thickness of the ceramic material layer is 50-300 μm, preferably 100-300 μm.

[0055] In the present invention, preferably, the thickness of the metal transition layer is 20-60 μm.

[0056] 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, more preferably (2.5-3.0):1. The present invention utilizes a ceramic material layer and a metal transition layer with an appropriate thickness ratio, which is more conducive to relieving thermal stress in the metal transition layer and the ceramic material layer while ensuring the impact resistance of the coating.

[0057] In some preferred embodiments of the present invention, the ceramic material layer is oxide ceramic.

[0058] 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.

[0059] More 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 excellent hardness and toughness.

[0060] 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.

[0061] In some preferred embodiments of the present invention, the material of the metal transition layer is selected from an MCrAlY alloy (where M is Ni, Co, Fe, or any combination thereof) and / or an aluminum alloy. Further preferably, the aluminum alloy is selected from at least one of a nickel-aluminum (NiAl) alloy, a nickel-chromium-aluminum alloy, and a nickel-chromium (NiCr) alloy. The present invention provides a wide range of options for the specific content of each component of each alloy. Reference can be made to existing technologies, and all of these are applicable to the present invention, so this will not be detailed here.

[0062] In some preferred embodiments of the present invention, the surface roughness Ra of the self-lubricating protective coating is less than 0.5 μm. The surface roughness of the self-lubricating protective coating is controlled in an appropriate low range, which is more conducive to the rapid formation of a lubricating oil film on the friction interface.

[0063] In some preferred embodiments of the present invention, the average microhardness of the self-lubricating protective coating is 400-900 HV 0.3 .

[0064] HV 0.3 It refers to the micro-Vickers hardness under the test load of 0.3 kgf (kilogram force).

[0065] Preferably, the self-lubricating protective coating of the present invention can withstand more than 10 impacts under conditions where the magnetic bearing weighs no less than 1000 kg and rotates at no less than 5000 rpm. The self-lubricating protective coating of the present invention can withstand more than 10 impacts under ultra-high loads and ultra-high speeds without noticeable wear, and has a long-lasting self-lubricating effect.

[0066] In a second aspect, the present invention provides a method for preparing a high-load-bearing, wear-resistant, self-lubricating protective coating, comprising the following steps:

[0067] S1, depositing a metal transition layer on the working surface of the substrate to be coated;

[0068] 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 increase gradually from the inside to the outside along the surface normal direction of the self-lubricating protective coating;

[0069] S3. Filling the pores of the ceramic material layer with lubricating oil.

[0070] The method of depositing the metal transition layer in S1 can refer to existing technologies, such as 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.

[0071] In some preferred embodiments of the present invention, the ceramic material layer is prepared by thermal spraying technology.

[0072] Further preferably, the thermal spraying conditions include: a spray distance of 80-130 mm, a current of 450-650 A, a voltage of 60-80 V, and a substrate temperature of 100-150° C. In the present invention, the porosity gradient distribution of the ceramic material layer can be controlled by regulating key parameters in the thermal spraying process, such as the spray distance, current, and voltage.

[0073] In some preferred embodiments of the present invention, the filling of lubricating oil adopts an impregnation process. Impregnation processes include but are not limited to vacuum impregnation, hot impregnation, and vacuum hot impregnation, all of which can be used in the present invention.

[0074] Further preferably, the immersion conditions include: an immersion temperature of 50-200°C, a pressure of 1-100 Pa, a single immersion time of 5-30 minutes, and a number of immersions of 1-5 times. During the immersion process of the present invention, the penetration depth and amount of lubricating oil within the ceramic material layer can be controlled by regulating relevant immersion parameters such as immersion time, temperature, and pressure.

[0075] In some preferred embodiments of the present invention, the preparation method further comprises: after preparing the ceramic material layer in S2, grinding the coating so that the final surface roughness Ra of the coating is less than 0.5 μm; and then performing S3. The present invention can control the thickness and surface roughness of the prepared target coating through the grinding process.

[0076] In a third aspect, the present invention provides a high-load-bearing, wear-resistant, self-lubricating protective coating, produced by the method for producing a high-load-bearing, wear-resistant, self-lubricating protective coating described in the second aspect. The structure and properties of the self-lubricating protective coating of the third aspect are identical to those of the self-lubricating protective coating of the first aspect and are not further described herein.

[0077] 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 described in the first aspect is provided, or the high-load-bearing and wear-resistant self-lubricating protective coating described in the third aspect is provided.

[0078] 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 damage. 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. 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.

[0079] The embodiments of the present invention are described in detail below, which are exemplary and only used to explain the present invention, and are not to be construed as limiting the present invention.

[0080] Example 1

[0081] 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). The coating method is as follows:

[0082] 1. First, a metal transition layer (specifically nickel-chromium alloy) is deposited with a thickness of 30 μm.

[0083] 2. A 200 μm-thick gradient porous ceramic layer (specifically, an aluminum oxide-titania mixture with 13 wt% titanium oxide) was prepared by thermal spraying. The pore count increased gradually and uniformly along the surface normal of the ceramic layer, and the porosity varied continuously within a range of 5%-35% (corresponding to the minimum and maximum values). The absolute difference in porosity between two adjacent layers with different gradients along the surface normal of the self-lubricating protective coating was within 5%. Thermal spraying conditions included a substrate temperature of 120°C, a spray distance of 110 mm, and currents of 650 A, 611 A, 575 A, 541 A, 509 A, 479 A, and 450 A, respectively. The corresponding voltages were adjusted to 80 V, 76 V, 73 V, 70 V, 66 V, 63 V, and 60 V. These currents and corresponding voltage parameters (i.e., spray power) were adjusted in seven gradients to achieve gradient porosity control. This process resulted in a ceramic layer with a specific pore gradient distribution.

[0084] 3. The thickness and surface roughness of the corresponding coating are controlled through the grinding process. The final surface roughness Ra of the coating is reduced to less than 0.5 μm, and the thickness of the ceramic material layer is retained at 90 μm. The thickness ratio of the ceramic material layer to the metal transition layer is calculated to be 3:1.

[0085] 4. Lubricant (methyl silicone oil) was then filled into the gradient porous ceramic layer using a vacuum impregnation process. Vacuum impregnation conditions included a single immersion time of 10 minutes, an immersion temperature of 100°C, a pressure of 30 Pa, and three immersions. This controlled the lubricant's penetration depth within the coating to 90 μm. This penetration depth was calculated to be 100% of the ceramic layer's thickness.

[0086] The microscopic morphology of the coating obtained in Example 1 is as follows Figure 3 As shown in the figure, it can be seen that the coating consists of a metal transition layer and a ceramic material layer, and the coating presents a typical layered structure. The cross-sectional morphology test and analysis of the prepared self-lubricating protective coating are carried out, and the analysis results are shown in the figure. Figure 5 As shown, combined Figure 5 The distribution of Si in the silicone oil indicates that the coating exhibits a gradient distribution, suggesting a gradient in the porosity of the self-lubricating protective coating. This indicates that pores exist within the ceramic layer, and the porosity increases from the inside out along the normal line. Due to the presence of the underlying metal transition layer, the coating achieved an average bond strength of 42 MPa after five tests on a universal testing machine, ensuring its long-term service life.

[0087] 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 .

[0088] Table 1 Microhardness of coating

[0089]

[0090] The surface morphology of the self-lubricating protective coating was tested and analyzed. The 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.

[0091] The self-lubricating protective coating of the present invention was 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). After ten drop tests under ultra-high load (magnetic bearing weight 1000kg) and ultra-high speed (5000rpm), the self-lubricating protective coating was applied to the auxiliary bearing unit. 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.

[0092] The present invention also conducted a friction performance test on the self-lubricating protective coating obtained in Example 1 with the above-mentioned microstructural characteristics. By selecting a representative friction pair material YG6 (i.e., a tungsten-cobalt cemented carbide material, commercially available) to grind the target coating for 1 hour, the target coating included a pure ceramic coating without lubricating oil coating (i.e., no metal transition layer and no porosity gradient distribution) as a comparison 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 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.

[0093] Example 2

[0094] The process was carried out in accordance with Example 1, except that the gradient of the uniform porosity increase within the ceramic material layer was different. Specifically, along the surface normal of the self-lubricating protective coating, the absolute value of the difference in porosity between two adjacent layers with different gradients was within 15%, and the maximum and minimum porosity within the ceramic material layer remained unchanged. The process conditions required to achieve this porosity setting were: spray distance of 110 mm, currents of 650 A, 550 A, and 450 A, voltages of 80 A, 70 A, and 60 V, and a substrate temperature of 120°C. These currents and corresponding voltage parameters (i.e., spray power) were adjusted to achieve gradient control of the porosity.

[0095] Example 3

[0096] 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 range is 5%-25%.

[0097] Example 4

[0098] The same process as in Example 1 was performed, except that the penetration depth of the lubricating oil within the ceramic layer was adjusted to 80% of the ceramic layer thickness. The process conditions required to meet this requirement were: a single immersion time of 10 minutes, a temperature of 100°C, a pressure of 50 Pa, and a single immersion.

[0099] Example 5

[0100] The process was carried out in accordance with Example 1, except that the thickness of the metal transition layer was adjusted to 25 μm. The thickness ratio of the ceramic material layer to the metal transition layer was calculated to be 3.6:1.

[0101] Comparative Example 1

[0102] The process is carried out in accordance with Example 1, except that no metal transition layer is provided.

[0103] Comparative Example 2

[0104] The same process as in Example 1 was followed, except that the porosity within the ceramic material layer was set uniformly (not incrementally) to 10%, and the pores were filled with lubricant to the same penetration depth as in Example 1. The process conditions adjusted to achieve this porosity setting were: spray distance 110 mm, current 611 A, voltage 76 V, and substrate temperature 120°C.

[0105] Test Case

[0106] The coatings obtained in Examples 2-5 and Comparative Examples 1-2 were subjected to the same performance tests as in Example 1, with the results shown in Table 2. The number of impact withstand tests under the same ultra-high load and ultra-high speed refers to the number of times the shaft and auxiliary bearing sleeve exhibited significant wear, such as at least one of coating peeling, furrowing, and adhesion, after multiple drop tests under the same ultra-high load and ultra-high speed. This number is the average of multiple data sets.

[0107] Table 2 Test results of coating properties obtained from Examples 1-5 and Comparative Examples 1-2

[0108]

[0109] 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 and material matching, can withstand more than 10 impacts of the magnetic bearing under high speed and high load, and makes the magnetic bearing shaft and the auxiliary bearing itself basically wear-free. At the same time, it ensures the long-term service of the self-lubricating protective coating, ensures the toughness and microhardness of the self-lubricating protective coating, and can be reused many times.

[0110] Furthermore, according to Examples 1 and 2-5, it can be seen that by adopting the preferred solution of the present invention, a higher number of impact resistances 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.

[0111] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A high-load-bearing, wear-resistant, self-lubricating protective coating, characterized in that: The self-lubricating protective coating comprises a metal transition layer and a ceramic material layer arranged in sequence, wherein the ceramic material layer has a plurality of pores inside, 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 thickness of the ceramic material layer is 50-300 μm, the penetration depth of the lubricating oil in the ceramic material layer is 60%-100% of the thickness of the ceramic material layer, and the increase in the porosity of the ceramic material layer satisfies: along the surface normal direction of the self-lubricating protective coating, the absolute value of the difference between the porosities of two adjacent layers with different gradients is 5%-15%.

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

3. The high-load-bearing, wear-resistant, self-lubricating protective coating according to claim 1 or 2, characterized in that: The ceramic material layer is oxide ceramic.

4. The high-load-bearing, 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 50-300µm.

5. The high-load-bearing, wear-resistant, self-lubricating protective coating according to claim 1, characterized in that: 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, 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 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, 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, 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 weighs 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, wherein the ceramic material layer is prepared by thermal spraying technology, wherein the thermal spraying conditions include: a spray distance of 80-130 mm, a current of 450-650 A, a voltage of 60-80 V, and a substrate temperature of 100-150° C.; and controlling the porosity of the ceramic material layer along the surface normal direction of the self-lubricating protective coating by regulating at least one of the parameters of the spray distance, the current, and the voltage during the thermal spraying process to increase the porosity of the ceramic material layer in a gradient from the inside to the outside. S3. Fill lubricating oil into the pores of the ceramic material layer using a vacuum hot impregnation process.

10. The method for preparing a high-load-bearing and wear-resistant self-lubricating protective coating according to claim 9, characterized in that: The conditions for vacuum hot 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 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, 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 according to 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 claimed in any one of claims 1 to 8 or a high-load-bearing, wear-resistant, self-lubricating protective coating as claimed in claim 12 is provided on the inner circle and / or end face of the auxiliary bearing unit in the contact area with the rotating shaft.

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