High-temperature self-lubricating wear-resistant nanocrystalline coating with bionic structure and preparation method of high-temperature self-lubricating wear-resistant nanocrystalline coating

Abstract

The invention relates to the technical field of nano-coatings, and discloses a high-temperature self-lubricating wear-resistant nanocrystalline coating with a bionic structure and a preparation method thereof.The preparation method comprises the steps that nickel-chromium alloy and pure aluminum serve as target materials, a plurality of basic unit layers are sequentially and repeatedly deposited on the surface of a base material from bottom to top through the magnetron sputtering technology, and the high-temperature self-lubricating wear-resistant nanocrystalline coating with the bionic structure is obtained; the plurality of basic unit layers form a coating, each basic unit layer comprises a first layer and a second layer, the first layer of the lowest basic unit layer is combined with the base material, the second layer of the uppermost basic unit layer forms a surface layer, the first layer of each basic unit layer comprises Ni and Cr elements, the second layer of each basic unit layer comprises Ni, Cr, Al and optionally O elements, and the surface layer of each basic unit layer comprises Ni, Cr, Al and optionally O elements. And the O element content of the second layer of the plurality of basic unit layers is gradually increased along with the increase of the number of deposited layers. The components and the structure of the coating are constructed in a gradient manner through oxygen element doping and aluminum element deposition time regulation and control, so that the coating has excellent tribological performance at the temperature of 600-800 DEG C, and the long-term anti-attrition and wear-resistant protection effect can be achieved.

Description

Technical Field

[0001] This application relates to the field of nanocoating technology, specifically to a high-temperature self-lubricating wear-resistant nanocrystalline coating with a biomimetic structure and its preparation method. Background Technology

[0002] As aero-engines increasingly evolve towards higher thrust-to-weight ratios, greater maneuverability, and longer range, transmission components such as bearings and bushings within the aero-engine power system constantly face critical challenges of high frictional resistance and rapid wear rates under complex conditions including high temperatures and high speeds. Therefore, protective coatings are widely used on the surfaces of these components. To meet the long service life and high stability requirements of transmission components, improving the strength and high-temperature wear resistance of the coatings is crucial.

[0003] In recent years, the research and application of multilayer nanocoatings have attracted much attention. For example, researchers have drawn inspiration from the multilayered "soft-hard" structure of organisms such as seashells to design multilayer wear-resistant coatings. They have used techniques such as magnetron sputtering and multi-arc ion plating to mimic and prepare multi-phase composite coatings, introducing soft metals and / or non-metallic elements to meet their friction-reducing and lubrication requirements. This type of coating not only avoids the problems of element interdiffusion and coating / alloy thermophysical property mismatch during service, which are common in traditional high-temperature protective coatings, but also synergistically improves its strength and toughness, maintaining good wear resistance and friction reduction characteristics at high temperatures, thus achieving the goal of long-term safe and stable operation of components.

[0004] CN111748719A discloses a VN-Ag2MoO4 composite material, which exhibits good self-lubricating properties from room temperature to 700℃. However, the preparation conditions are demanding, the preparation quality is unstable, and the coefficient of friction is higher than 0.25 from 500℃ to 700℃. Chinese patent CN111286701A discloses a multi-phase composite MeSiCN-Ag wear-resistant lubricating coating deposited using multi-arc ion plating technology. At high temperatures, it achieves lubrication by forming MAX hard nano-metal compounds and soft Ag phases. However, this coating structure also suffers from problems such as high-temperature lubrication stability and bonding strength.

[0005] It is evident that existing multilayer composite coating systems have made some progress in high-temperature wear resistance, but their practical application still faces many problems. For example, the performance of multilayer composite coatings is unstable in the high-temperature range, with significant fluctuations in the coefficient of friction (0.2~0.4) and varying wear rates, making it difficult to meet the precise transmission requirements of moving parts. Secondly, in order to achieve the preparation of multilayer composite coatings, the mainstream method in current research is to use multiple processes in combination or alternately, but the interfacial bonding strength is insufficient and the preparation process is complex. Summary of the Invention

[0006] The purpose of this application is to overcome the problems of significant fluctuations in friction coefficient, insufficient interlayer bonding strength, and complex preparation processes in existing multilayer composite coatings, and to provide a high-temperature self-lubricating wear-resistant nanocrystalline coating with a biomimetic structure and its preparation method. The biomimetic nanocrystalline coating provided by this invention has high bonding strength, excellent mechanical properties, and superior tribological properties at 600℃~800℃, achieving long-term wear reduction and wear-resistant protection effects. Furthermore, the preparation process is simple and suitable for industrial applications.

[0007] To achieve the above objectives, the first aspect of this application provides a method for preparing a high-temperature self-lubricating wear-resistant nanocrystalline coating with a biomimetic structure, wherein the preparation method includes: using nickel-chromium alloy and pure aluminum as target materials, and employing magnetron sputtering technology to repeatedly deposit multiple basic unit layers sequentially from bottom to top on the surface of a substrate, wherein the multiple basic unit layers form a coating; Each of the basic unit layers includes a first layer and a second layer located on the first layer, wherein the first layer of the bottommost basic unit layer is bonded to the substrate, and the second layer of the topmost basic unit layer forms a surface layer. The first layer of each basic unit layer includes Ni and Cr elements, and its second layer includes Ni, Cr, Al and optionally O elements. The O element content of the second layer of the plurality of basic unit layers gradually increases with the increase of the number of deposition layers, and the oxygen flow rate during the deposition of the second layer of the plurality of basic unit layers is 0-7 sccm.

[0008] Nanostructuring is beneficial for improving the hardness and wear resistance of coating materials. This application, by incorporating an appropriate amount of oxygen during the sputtering process, can generate dispersed nano-oxide particles in the microstructure, which can refine the grains and strengthen the dispersion, further improving the strength, hardness, and wear resistance of the coating. Utilizing this characteristic and the principle of selective oxidation, a nanocrystalline coating with an alternating "soft-hard" shell-like structure is constructed. The oxygen content of each layer gradually increases from bottom to top (or from the inside to the outside of the coating), constructing a gradient structure in which nano-oxide particles pin the grain boundaries, thereby improving the overall mechanical properties of the coating.

[0009] During high-temperature friction, the addition of surface oxygen promotes the formation of Cr and Ni oxides. Under the influence of frictional heat and ambient temperature, the oxides are repeatedly squeezed, crushed, and sintered by the friction pair to form a dense and uniform oxide lubricating layer. During high-temperature oxidation, the oxide layer preferentially nucleates in situ on the surface of nano-oxide particles and gradually grows outward, promoting the formation of a strongly adhesive "mosaic coherent" oxide / coating interface microstructure. This greatly enhances the adhesion strength of the oxide / coating interface and reduces the peeling of the oxide layer under frictional shear force. As high-temperature friction consumes the material, the nanograin boundaries can provide a large number of rapid channels for the diffusion of Cr and Ni elements from inside the coating to the surface, allowing them to be replenished and repaired in a timely manner. The selective oxidation of Al and Cr results in the formation of a continuous Al₂O₃ or Cr₂O₃ layer beneath, which hinders element interdiffusion, improves the coating's oxidation resistance, and alleviates oxidative wear. The gradient oxygen distribution creates a "soft-hard" alternating structure, forming a yield strength gradient in the subsurface layer of the coating. This expands the plastic deformation zone under frictional stress, eliminates strain localization, and effectively prevents or delays cracking and spalling of the friction layer during high-temperature friction, thereby reducing the coefficient of friction and improving the coating's tribological properties. The surface-formed oxide lubricating layer and the excellent toughness of the shell-like nanostructure work together to reduce friction and increase wear resistance, meeting the requirements for long-term stable service at high temperatures.

[0010] In the coating prepared in this application, the first layer (also known as the non-oxygen-doped aluminum layer) and the second layer (also known as the oxygen-doped aluminum layer) are alternately distributed. There are no special requirements for the oxygen flow rate when depositing the second layer of multiple basic unit layers, as long as it gradually increases with the increase of the number of deposited layers. For example, the oxygen flow rate of each layer can be 0, 2 sccm, 4 sccm, 6 sccm, 7 sccm, etc.

[0011] Preferably, the second layer of the lowest basic unit layer includes Ni, Cr, and Al elements, and the second layer of the other basic unit layers includes Ni, Cr, Al, and O elements.

[0012] Preferably, the oxygen flow rate during the deposition of the second layer of the uppermost basic unit layer is 5.5-6.5 sccm. An excessively high oxygen flow rate in the surface oxygen-doped aluminum layer will cause the oxide layer thickness to increase too quickly, while an insufficient flow rate will fail to achieve the goal of forming a continuously stable oxide layer during high-temperature friction. The oxygen flow rate during the deposition of the uppermost basic unit layer can be any value between 5.5 sccm, 5.8 sccm, 6 sccm, 6.2 sccm, 6.5 sccm, and any two of these values.

[0013] Preferably, the deposition time ratio of the first layer and the second layer of each basic unit layer is 1:1-5. The deposition time ratio of the first layer and the second layer affects their thickness. If the ratio of the second layer is too small, the coating will not be hard enough and will oxidize during high-temperature friction, resulting in insufficient oxidation resistance, reduced adhesion of surface oxides, and possibly no lubrication effect during friction. The deposition time ratio of the first layer and the second layer can be 1:1, 1:2, 1:3, 1:4, 1:5, or any value between any two of these numbers.

[0014] Preferably, based on the total amount of the nickel-chromium alloy, the nickel content in the nickel-chromium alloy is 75-85 wt.%, and the chromium content is 15-25 wt.%. When the Cr content is too low, the resulting coating will also have a low Cr content, which will lead to a significant reduction in the service life of the coating. If the Cr content is too high, it will lead to a serious decrease in the toughness of the coating, and the target material will change its conductivity, sputtering rate, etc. during the refining process.

[0015] Preferably, based on the total amount of the nickel-chromium alloy, the amount of nickel in the nickel-chromium alloy is 78-82 wt.%, and the amount of chromium is 18-22 wt.%.

[0016] Based on the total amount of nickel in the nickel-chromium alloy, the amount of nickel in the nickel-chromium alloy can be 75wt.%, 77wt.%, 78wt.%, 79wt.%, 81wt.%, 82wt.%, 83wt.%, 85wt.%, and any value between any two of them, and the amount of chromium can be 15wt.%, 16wt.%, 18wt.%, 20wt.%, 22wt.%, 25wt.%, and any value between any two of them.

[0017] Preferably, the total deposition time of the plurality of basic unit layers is 4-8 hours, such as 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, and any value between any two of them.

[0018] Preferably, the step of repeatedly depositing multiple basic unit layers sequentially from bottom to top on the substrate surface using magnetron sputtering technology includes: S1 connects the nickel-chromium alloy to the intermediate frequency power supply and the pure aluminum to the DC power supply. S2, the magnetron sputtering chamber is evacuated and heated until the vacuum level does not exceed 6×10⁻⁶. -3 At a temperature of 200℃, argon gas is introduced and the argon pressure is controlled at 0.1±0.02Pa, and the argon gas flow rate is 15±1sccm. S3, start the intermediate frequency power supply, set the output voltage to 1000±50V, the output current to 5.6±0.3A, and the duty cycle to 80±0.5%, and perform the deposition of the first layer of the first basic unit layer; S4, start the DC power supply, set the sputtering power to 800±10W, introduce oxygen and set the oxygen flow rate to the preset value, and perform the deposition of the second layer of the first basic unit layer. S5. Repeat steps S3 and S4 until all basic unit layers have been deposited.

[0019] Before deposition, the substrate is mounted on a rotating frame 15 cm away from the target. During deposition, the substrate is rotated using the rotating frame to ensure that the coating thickness formed on the substrate surface is uniform. The rotation speed of the substrate can be 20-25 rpm.

[0020] Preferably, the coating comprises four basic unit layers, with oxygen flow rates of 0 sccm, 2 sccm, 4 sccm and 6 sccm respectively when the second layer of each basic unit layer is deposited from bottom to top, and the deposition time ratio of the first layer and the second layer of the basic unit layer is 1:2.

[0021] Preferably, the preparation method further includes pretreatment of the substrate and the target material, the pretreatment step including: Sputter cleaning of the target material for 30-40 minutes is performed to remove the oxide layer and contaminants on the target surface; The substrate is sanded with SiC sandpaper, then mirror polished with polishing paste, and finally ultrasonically cleaned with a mixture of acetone and alcohol for 30-40 minutes before use.

[0022] There are two nickel-chromium alloy targets and one pure aluminum target. The base material can be stainless steel or other metal materials.

[0023] The second aspect of this application provides a coating prepared by the method described in the first aspect of the present invention.

[0024] The coating prepared by this invention exhibits an increasing trend in oxygen (O) content across each basic unit layer from the direction closest to the substrate towards the direction furthest from the substrate. Based on the total element content in the second layer of the outermost basic unit layer (the total element content in the corresponding layer of each basic unit layer is 100 wt.%), the second layer of the outermost basic unit layer contains 5-7 wt.% O, 50-60 wt.% Ni, 20-25 wt.% Cr, and 10-20 wt.% Al. The element content in the coating can be determined using methods commonly used in the art, such as using a SIGMA 500 field emission scanning electron microscope to perform surface scanning of each layer of the prepared coating cross-section to detect the element content.

[0025] Preferably, the thickness of the basic unit layer is 5-7 μm.

[0026] Preferably, the thickness of the coating is 20-25 μm.

[0027] Preferably, the bonding strength between the coating and the substrate is not less than 83N, the coefficient of friction of the coating at 600-800℃ is 0.2-0.25, and the wear amount does not exceed 4-7×10⁻⁶. -5 mm 3 / Nm.

[0028] The coating structure obtained by this invention is as follows Figure 1 As shown, multiple basic unit layers 2 are deposited sequentially from bottom to top on the surface of substrate 1. Figure 1 Specifically, there are 4 layers. Each basic unit layer 2 includes a first layer 2b located below and a second layer 2a located above the first layer. The multiple basic unit layers 2 are stacked sequentially from bottom to top to form a nanocrystalline coating.

[0029] This invention addresses the key issue of uneven strength, toughness, tribological properties, and oxidation resistance in existing high-temperature protective coatings by controlling oxygen doping and aluminum deposition time to gradient-construct the composition and structure of the coating. The resulting coating exhibits high bonding strength, excellent mechanical properties, and superior tribological properties at 600℃-800℃, achieving long-term wear-reducing and wear-resistant protective effects.

[0030] The preparation method provided by this invention uses magnetron sputtering technology, which is not limited by the substrate structure and can be used for surface coating of complex components. It does not require multiple processes to work together, the preparation process is simple and low in cost, and it is suitable for industrial application.

[0031] Other features and advantages of the embodiments of this application will be described in detail in the following detailed description section. Attached Figure Description

[0032] The accompanying drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the following detailed description to explain the embodiments of this application, but do not constitute a limitation on the embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without any inventive effort. In the drawings: Figure 1 This is a schematic diagram of the coating structure; Figure 2 SEM images of the coatings obtained in Examples 1-3; Figure 3 The graph shows the coefficient of friction of the coatings obtained in Examples 1-3 after ball-disc friction at 600°C for 30 minutes. Figure 4 The graph shows the coefficient of friction of the coatings obtained in Examples 1-3 after being subjected to ball-disc friction at 800°C for 30 minutes. Figure 5 The images show the wear marks of the coatings obtained in Examples 1-3 after being subjected to ball-and-disc friction at 600°C for 30 minutes. Figure 6 The images show the wear marks of the coatings obtained in Examples 1-3 after being subjected to ball-and-disc friction at 800°C for 30 minutes. Figure 7 The images show the morphology of the coatings obtained in Examples 1-3 after testing the film-substrate adhesion at room temperature. Detailed Implementation

[0033] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0034] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0035] 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 or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0036] Furthermore, the term "and / or" in the specification and claims is used to describe the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0037] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature.

[0038] In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise expressly and specifically limited.

[0039] The present invention will be further illustrated below with reference to embodiments and comparative examples. Unless otherwise specified, all reagents or instruments used in the following embodiments and comparative examples are commercially available conventional products. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply.

[0040] In the following examples, the nickel-chromium alloy target material contains 80 wt.% Ni and 20 wt.% Cr, while the pure aluminum target material contains 99.99 wt.% aluminum.

[0041] Film-substrate adhesion test method: The film-substrate adhesion of the prepared coating was tested using a WS-2005 scratch tester at room temperature (25℃), with a loading speed of 100N / min, a termination load of 100N, and a scratch length of 5mm.

[0042] Tribological performance testing method: The tribological performance of the prepared coating was tested at 600℃ and 800℃ using an HT-1000 high-temperature friction testing machine. The friction pair ball used was a Si3N4 ball with a diameter of 6mm. The normal load was 5N, the rotation speed was 300r / min, and the friction time was 30min. Example 1

[0043] Magnetron sputtering technology (medium frequency + DC) was employed, using 316L stainless steel as the substrate. The target materials included two nickel-chromium alloy targets and one pure aluminum target, with target dimensions of 382mm × 128mm × 8mm. During the preparation process, different gradient multilayer structures of shell-like nanocrystalline coatings were prepared by adjusting the Al target deposition time and the oxygen flow rate of the Al-containing layer. The specific preparation process is as follows: S1 Target Installation and Cleaning: Two nickel-chromium alloy targets are installed face-to-face and parallel to the cathode water-cooled target sleeve and connected to an AC power supply. A pure aluminum target is installed in the cathode water-cooled target sleeve and connected to a DC power supply. Then, the target was cleaned for 40 minutes using the same sputtering power as that used to prepare the coating, to remove the oxide layer and contaminants from the target surface.

[0044] S2 Sample Pretreatment: 316L stainless steel was cut into cylindrical samples with a diameter of φ20×10mm using wire EDM. The sample surface was then polished with 320~2000# SiC sandpaper to remove the surface oxide scale. The sample was then polished with 2.5μm polishing paste. Finally, the sample was ultrasonically cleaned for 30 minutes with a 1:3 mixture of acetone and alcohol. After drying, the sample was suspended parallel to the target on a rotating frame 15cm away, and the chamber of the magnetron sputtering equipment was closed.

[0045] Preparation of S3 coating: S31, before preparation, a vacuum is first evacuated using a mechanical pump and a vacuum pump until the vacuum level reaches 2×10⁻⁶. -5 Heating begins at a pressure of Pa, and continues until the chamber vacuum reaches 6 × 10⁻⁶. -3 When the temperature reaches 200℃, argon gas is introduced at a flow rate of 15 sccm, the grating is turned on, and the rotating frame is adjusted to rotate uniformly at a speed of 25 rpm. S32, turn on the medium frequency sputtering power switch, output voltage 1000V, output current 5.6A, duty cycle 80%, argon pressure 0.1Pa, start deposition, deposition time 45min, deposit the first layer of the first basic unit layer, namely the NiCr layer; S33, after completing the deposition of the first layer, turn on the DC power switch, sputtering power 800W, deposition time 45min, to prepare the second layer of the first basic unit layer, namely the NiCrAl layer (this layer is not oxygen-doped). S34, repeat S32 and S333 times to complete the deposition of the other three basic unit layers, with a total sputtering time of 6 hours. Unlike the first basic unit layer, oxygen needs to be introduced when depositing the second layer of the other three basic unit layers. The oxygen flow rates of the second layer of the other three basic unit layers from bottom to top are 2 sccm, 4 sccm, and 6 sccm, respectively. Example 2

[0046] The procedure is the same as in Example 1, with the only difference being: The deposition time in step S32 is 30 min, and the deposition time in step S33 is 60 min, that is, the deposition time ratio of the first layer and the second layer is 1:2. Example 3

[0047] The procedure is the same as in Example 1, with the only difference being: The deposition time in step S32 is 15 min, and the deposition time in step S33 is 75 min, that is, the deposition time ratio of the first layer to the second layer is 1:5.

[0048] SEM images of the coatings obtained in Examples 1-3 are shown below. Figure 2 As shown, Figure 2 (a)- Figure 2 (c) SEM images of the coatings obtained in Examples 1, 2 and 3 are shown in sequence. It can be seen from the images that the coatings obtained by the present invention have good bonding with the substrate interface, and no cracks, holes or other defects were found at the interface of each layer. The light and dark layers are obvious.

[0049] The coating prepared in Example 1 has a first layer (non-oxygen-doped aluminum layer) with a thickness of approximately 2.94 μm, a second layer (oxygen-doped aluminum layer) with a thickness of approximately 2.92 μm, a thickness of approximately 6 μm for each basic unit layer, and a total coating thickness of approximately 24 μm.

[0050] The coating prepared in Example 2 has a first layer (non-oxygen-doped aluminum layer) with a thickness of about 2 μm, a second layer (oxygen-doped aluminum layer) with a thickness of about 4.1 μm, a thickness of about 6 μm for each basic unit layer, and a total coating thickness of about 24.4 μm.

[0051] The coating prepared in Example 3 has a first layer (non-oxygen-doped aluminum layer) with a thickness of about 1 μm, a second layer (oxygen-doped aluminum layer) with a thickness of about 5.1 μm, a thickness of about 6 μm for each basic unit layer, and a total coating thickness of about 24.5 μm.

[0052] The coatings obtained in Examples 1-3 were subjected to film-substrate adhesion and tribological property tests, respectively. The friction coefficient curves after the tribological property test at 600℃ are shown below. Figure 3 As shown, the friction coefficient curve after tribological property testing at 800℃ is as follows. Figure 4 As shown in Table 1, the test results are as follows.

[0053] Table 1

[0054] As can be seen from Table 1, the coating prepared by the present invention has excellent adhesion to the substrate and small fluctuation in the coefficient of friction between 600℃ and 800℃. In particular, the coating prepared in Example 2 has an adhesion exceeding 90N and the best overall performance in terms of coefficient of friction and wear rate between 600℃ and 800℃.

[0055] The surface morphology of the coatings obtained in Examples 1-3 after friction performance testing at 600°C is as follows. Figure 5 As shown in the figure, the surface of the coating wear marks in Examples 1-2 is basically covered by the friction oxide layer, the contact area is relatively flat, and only local puddles formed by the cracking and peeling of friction products appear. In the wear marks of Example 3, only a small area has formed a compacted oxide layer, and large areas have flaky peeling, failing to form a continuous and dense glaze layer.

[0056] The surface morphology of the coatings obtained in Examples 1-3 after friction performance testing at 800°C is as follows. Figure 6As shown in the figure, the coatings of Examples 1-2 formed a dense and continuous friction oxide layer on the wear surface, with no obvious blocky peeling, furrows or cracks. Only a small amount of friction products fell off or there were incomplete bonding areas in some places, which effectively prevented direct contact between the friction pair and the coating surface, and showed good tribological properties. In Example 3, there was a partially compacted oxide layer in the wear mark, but the coverage ratio was low and there was obvious flaky peeling. There was a large amount of oxide abrasive particles accumulated in the uncompacted area. It can be seen that the coatings prepared in Example 3 did not form an effective oxide layer on the wear surface at 600℃ and 800℃. The reason is that the solid content of Al in the coating is too high, which consumes more oxygen elements at high temperature and inhibits the formation of the glaze layer.

[0057] The surface morphology of the coatings obtained in Examples 1-3 after film-substrate adhesion testing at room temperature is as follows: Figure 7 As shown, where Figure 7 Images (a), (b), and (c) are morphological images of the coatings after scratch tests in Examples 1-3, respectively. In Example 3, the oxygen-doped aluminum layer is too thick, has high hardness, but insufficient toughness. After scratching, the residual tensile stress is high, leading to surface cracks that propagate. Due to stress concentration at the edges and insufficient interfacial toughness, the cracks deflect and propagate along the layer-to-layer interface, evolving into island-like delamination and peeling, with a widened trajectory. In Example 1, the oxygen-doped aluminum layer is too thin, has low hardness, and exhibits significant plastic buildup in the middle and later stages. Stress concentration at the edges accelerates crack propagation, resulting in scattered peeling. In Example 2, the coating thickness is moderate, combining strength and toughness. This reduces interfacial stress concentration, passively blocks cracks, and delays the appearance of surface and edge cracks. Under the specific scheme of Example 2, the formation of "fishbone-like" cracks near the scratched area is effectively avoided.

[0058] The contents not described in detail in this specification are existing technologies known to those skilled in the art, and will not be elaborated upon here.

[0059] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. However, these simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a high-temperature self-lubricating wear-resistant nanocrystalline coating with a biomimetic structure, characterized in that, The preparation method includes: using nickel-chromium alloy and pure aluminum as target materials, and employing magnetron sputtering technology to repeatedly deposit multiple basic unit layers on the substrate surface from bottom to top, forming a coating; each basic unit layer includes a first layer and a second layer located on the first layer, wherein the first layer of the bottommost basic unit layer is bonded to the substrate, and the second layer of the topmost basic unit layer forms a surface layer, the first layer of each basic unit layer includes Ni and Cr elements, and its second layer includes Ni, Cr, Al and optionally O elements, the O element content of the second layer of the multiple basic unit layers gradually increases with the increase of the number of deposition layers, and the oxygen flow rate during the deposition of the second layer of the multiple basic unit layers is 0-7 sccm.

2. The preparation method according to claim 1, wherein, The second layer of the lowest basic unit layer includes Ni, Cr, and Al elements, while the second layer of the other basic unit layers includes Ni, Cr, Al, and O elements; And / or, the oxygen flow rate is 5.5-6.5 sccm when the second layer of the uppermost basic unit layer is deposited.

3. The preparation method according to claim 2, wherein, The deposition time ratio of the first and second layers of each basic unit layer is 1:1-5.

4. The preparation method according to any one of claims 1-3, characterized in that, Based on the total amount of the nickel-chromium alloy, the amount of nickel in the nickel-chromium alloy is 75-85 wt.%, and the amount of chromium is 15-25 wt.%.

5. The preparation method according to claim 4, wherein, Based on the total amount of the nickel-chromium alloy, the amount of nickel in the nickel-chromium alloy is 78-82 wt.%, and the amount of chromium is 18-22 wt.%.

6. The preparation method according to claim 4, wherein, The total deposition time for the multiple basic unit layers is 4-8 hours.

7. The preparation method according to claim 4, wherein, The step of repeatedly depositing multiple basic unit layers sequentially from bottom to top on the substrate surface using magnetron sputtering technology includes: S1 connects the nickel-chromium alloy to the intermediate frequency power supply and the pure aluminum to the DC power supply. S2, the magnetron sputtering chamber is evacuated and heated until the vacuum level does not exceed 6×10⁻⁶. -3 At a temperature of 200℃, argon gas is introduced and the argon pressure is controlled at 0.1±0.02Pa, and the argon gas flow rate is 15±1sccm. S3, start the intermediate frequency power supply, set the output voltage to 1000±50V, the output current to 5.6±0.3A, and the duty cycle to 80±0.5%, and perform the deposition of the first layer of the first basic unit layer; S4, start the DC power supply, set the sputtering power to 800±10W, introduce oxygen and set the oxygen flow rate to the preset value, and perform the deposition of the second layer of the first basic unit layer. S5. Repeat steps S3 and S4 until all basic unit layers have been deposited.

8. The preparation method according to any one of claims 1-3, wherein, The coating comprises four basic unit layers, with oxygen flow rates of 0 sccm, 2 sccm, 4 sccm and 6 sccm respectively when the second layer of each basic unit layer is deposited from bottom to top, and the deposition time ratio of the first layer and the second layer of the basic unit layer is 1:

2.

9. A coating prepared by the method according to any one of claims 1-8.

10. The coating according to claim 9, wherein, The thickness of the basic unit layer is 5-7 μm; And / or, the bonding strength between the coating and the substrate is not less than 83N, the coefficient of friction of the coating at 600-800℃ is 0.2-0.25, and the wear amount does not exceed 4-7×10⁻⁶. -5 mm 3 / Nm.

Images