Composite coating as well as preparation method and application thereof

Abstract

The invention provides a composite coating as well as a preparation method and application thereof, and belongs to the technical field of manufacturing of aviation parts. The composite coating comprises a WC-CrC-Ni layer, a CrN layer and a W-DLC layer which are arranged in a stacked mode. The WC-CrC-Ni layer has the advantages of high hardness, high toughness, high modulus and the like, and provides good support for the CrN layer and the W-DLC layer as a base coat; the CrN layer is a transition layer, plays a supporting role and can improve the bonding strength of the subsequent W-DLC layer; the W-DLC layer can greatly reduce the friction coefficient and the abrasion degree under the condition of grease, W can react with oxygen adsorbed on the surface to form a large amount of WO2 with the friction reducing effect, the tribological performance of the W-DLC layer under the poor lubrication condition is effectively enhanced, and therefore the abrasion resistance is improved; and meanwhile, the W-DLC layer is resistant to corrosion and can prevent the formation of a corrosion channel, so that the corrosion resistance is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of manufacturing of aviation components, and particularly relates to a composite coating, a preparation method thereof and an application thereof. Background Art

[0002] When an aircraft is in flight, the articulated bearing bears extremely high loads and needs to rotate frequently. At the same time, when flying in a marine environment, the aircraft also faces the corrosion of the marine atmosphere and the problem of poor lubrication effect of the grease. Under the action of the coupled working conditions of corrosion and wear, the wear rate of the articulated bearing is greatly accelerated, thereby affecting its service life and performance stability. Long-term wear will not only lead to the failure of the articulated bearing, but even cause the failure of the entire component, resulting in serious flight accidents.

[0003] By preparing antifriction materials on the surface of the articulated bearing, the tribological properties of the inner ring of the articulated bearing can be improved to a certain extent, such as methods of preparing dry film lubricants on the surface, electrospark deposition of bronze, etc. Although the preparation of antifriction materials on the material surface reduces the friction coefficient of the friction pair of the articulated bearing and thus improves the service life, due to the poor wear resistance and anti-corrosion properties of these antifriction materials, although the service life of the articulated bearing is improved to a certain extent, it still far from the designed service life. Therefore, how to improve the wear resistance and anti-corrosion properties of the antifriction materials to improve the service life of the articulated bearing has become a technical problem to be solved urgently in this field. Summary of the Invention

[0004] The purpose of the present invention is to provide a composite coating, a preparation method thereof and an application thereof. The composite coating provided by the present invention has excellent wear resistance and corrosion resistance, thereby improving the service life of the articulated bearing.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a composite coating, including a WC-CrC-Ni layer, a CrN layer and a W-DLC layer which are stacked.

[0007] Preferably, the thickness of the WC-CrC-Ni layer is 195-200 μm.

[0008] Preferably, the WC-CrC-Ni layer includes the following chemical components in mass percentage: Cr 20-22%, Ni 5-7%, C 4-6% and the balance W.

[0009] Preferably, the total thickness of the CrN layer and the W-DLC layer is 3-5 μm.

[0010] Preferably, the thickness of the W-DLC layer is 2-4 μm.

[0011] Preferably, the content of W in the W-DLC layer is 9-20 at.%.

[0012] The present invention also provides a method for preparing the composite coating described in the above technical solution, including the following steps:

[0013] (1) Adopt supersonic plasma spraying on the surface of the substrate to obtain a WC-CrC-Ni layer;

[0014] (2) On the surface of the WC-CrC-Ni layer obtained in the step (1), sequentially prepare a CrN layer and a W-DLC layer by chemical vapor deposition to obtain a composite coating.

[0015] Preferably, the process parameters of the supersonic plasma spraying in the step (1) include: argon gas flow rate of 170-260 slpm; current of 400-500 A; voltage of 100-160 V; powder feeding rate of 20-60 g / min; spraying distance of 100-120 mm.

[0016] Preferably, the process parameters of the chemical vapor deposition in the step (2) independently include: vacuum chamber pressure of 0.3-3.0 Pa, nitrogen gas flow rate of 0-2000 sccm, methane gas flow rate of 0-150 sccm, argon gas flow rate of 0-150 sccm, temperature of 90-400 °C, substrate bias voltage of -150 to -50 V, ion source power of 1.0-2.0 kW, and deposition time of 60-300 min.

[0017] The present invention also provides the application of the composite coating described in the above technical solution or the composite coating prepared by the preparation method described in the above technical solution in the inner ring of a spherical plain bearing.

[0018] The present invention provides a composite coating, including a WC-CrC-Ni layer, a CrN layer, and a W-DLC layer which are stacked. In the present invention, the WC-CrC-Ni layer has the advantages of high hardness, high toughness, and high modulus, etc. As a bottom layer, it provides good support for the CrN layer and the W-DLC layer, effectively preventing the problem of the "egg shell effect"; the CrN layer is a transition layer, playing a supporting role and capable of improving the bonding strength of the subsequent W-DLC layer; the W-DLC layer can greatly reduce the friction coefficient and wear degree under the condition of having grease, and improve the stability during the friction process. W can react with the adsorbed oxygen on the surface to form a large amount of WO2 with anti-friction effect, effectively enhancing the tribological performance of the W-DLC layer under poor lubrication conditions, thereby improving the wear resistance; at the same time, the W-DLC layer itself is corrosion-resistant and can prevent the formation of corrosion channels, thereby improving the anti-corrosion performance and further improving the service life of the component. Experimental results show that the service life of the composite coating provided by the present invention is increased by more than 5 times compared with the existing products. Description of the Drawings

[0019] Figure 1 Schematic diagram of the structure of the composite coating prepared in Example 1;

[0020] Figure 2 Scanning electron micrograph of the composite coating prepared in Example 1;

[0021] Figure 3 Physical photograph of the composite coating after the wear experiment prepared in Example 1;

[0022] Figure 4 For Figure 3 High-resolution laser image of the wear scar in the red box area;

[0023] Figure 5 For Figure 4 Contour curve of the red dashed part in

[0024] Figure 6 For Figure 3 3D topography image of the wear scar in the red box area;

[0025] Figure 7 Physical photograph of the existing product in Comparative Example 1 before the neutral salt spray test;

[0026] Figure 8 Physical photograph of the existing product in Comparative Example 1 after 24 h of corrosion;

[0027] Figure 9 Physical photograph of the composite coating prepared in Example 1 before the neutral salt spray test;

[0028] Figure 10 Physical photograph of the composite coating prepared in Example 1 after 240 h of corrosion;

[0029] Figure 11 Scanning electron micrograph of the composite coating prepared in Example 2;

[0030] Figure 12 Wear depth curve on the wear baseline after the wear resistance test of the existing product in Comparative Example 1;

[0031] Figure 13 Wear depth curve on the wear baseline after the wear resistance test of the composite coating prepared in Example 2;

[0032] Figure 14 Specific wear rate curve of the composite coating prepared in Example 2 and Comparative Example 1 after the wear resistance test;

[0033] Figure 15 Physical photograph of the composite coating prepared in Example 2 before the neutral salt spray test;

[0034] Figure 16The physical diagram of the composite coating prepared in Example 2 after 240 hours of corrosion. Detailed implementation manners

[0035] The present invention provides a composite coating, which includes a WC-CrC-Ni layer, a CrN layer, and a W-DLC layer that are stacked.

[0036] The composite coating provided by the present invention is applicable to any substrate, preferably applicable to the inner ring of a spherical plain bearing, and more preferably applicable to the inner ring of an aviation spherical plain bearing.

[0037] In the present invention, the composite coating includes a WC-CrC-Ni layer; the thickness of the WC-CrC-Ni layer is preferably 195-200 μm. As an implementation manner, the thickness of the WC-CrC-Ni layer can be 196 μm, 198 μm, or 200 μm. In the present invention, the WC-CrC-Ni layer has advantages such as high hardness, high toughness, and high modulus. As a primer layer, it provides good support for the CrN layer and the W-DLC layer, effectively preventing the problem of the "egg shell effect"; by limiting the thickness of the WC-CrC-Ni layer within the above range, the present invention can further improve the support effect.

[0038] In the present invention, the WC-CrC-Ni layer preferably includes chemical components with the following mass percentages: 20-22% of Cr, 5-7% of Ni, 4-6% of C, and the balance of W. As an implementation manner, the WC-CrC-Ni layer can be composed of chemical components with the following mass percentages: 21% of Cr, 6% of Ni, 5% of C, and the balance of W. By limiting the components in the WC-CrC-Ni layer within the above range, the present invention can further improve the support effect, thereby further improving the service life of the spherical plain bearing.

[0039] In the present invention, the composite coating further includes a CrN layer disposed on the surface of the WC-CrC-Ni layer. In the present invention, the CrN layer is a transition layer that plays a supporting role and can improve the bonding strength of the subsequent W-DLC layer.

[0040] In the present invention, the composite coating further includes a W-DLC layer disposed on the surface of the CrN layer. In the present invention, under the condition of having grease, the W-DLC layer can greatly reduce the friction coefficient and wear degree, and improve the stability during the friction process. W can react with the adsorbed oxygen on the surface to form a large amount of WO2 with a friction-reducing effect, effectively enhancing the tribological performance of the W-DLC layer under poor lubrication conditions, thereby improving the wear resistance; at the same time, the W-DLC layer itself is corrosion-resistant and can prevent the formation of corrosion channels, thereby improving the anti-corrosion performance and further improving the service life of the spherical plain bearing.

[0041] In the present invention, the thickness of the W-DLC layer is preferably 2 to 4 μm. As an embodiment, the thickness of the W-DLC layer can be 2.05 μm, 2.5 μm, 3 μm or 4 μm. Limiting the thickness of the W-DLC layer within the above range in the present invention can further improve the wear resistance and corrosion resistance.

[0042] In the present invention, the W content in the W-DLC layer is preferably 9 to 20 at.%. As an embodiment, the W content can be 10 at.%, 11 at.%, 12 at.%, 12.5 at.%, 13 at.%, 14 at.%, 15 at.%, 16 at.%, 17 at.%, 18 at.% or 19 at.%. By limiting the W content to 9 to 20 at.% in the present invention, the interaction between the W-DLC layer and the grease in the initial running-in stage of the friction pair can be improved, so that W can react with the adsorbed oxygen on the surface to form a large amount of WO2 with a friction-reducing effect, effectively enhancing the tribological performance of the W-DLC layer under poor lubrication conditions.

[0043] In the present invention, the total thickness of the CrN layer and the W-DLC layer is preferably 3 to 5 μm. As an embodiment, the total thickness of the CrN layer and the W-DLC layer can be 4.05 to 4.15 μm.

[0044] In the present invention, the WC-CrC-Ni layer has the advantages of high hardness, high toughness and high modulus, etc. As a bonding layer, it provides good support for the CrN layer and the W-DLC layer, effectively preventing the problem of the "eggshell effect"; the CrN layer is a transition layer, playing a supporting role and capable of improving the bonding strength of the subsequent W-DLC layer; the W-DLC layer can greatly reduce the friction coefficient and wear degree under the condition of having grease, and improve the stability during the friction process. W can react with the adsorbed oxygen on the surface to form a large amount of WO2 with a friction-reducing effect, effectively enhancing the tribological performance of the W-DLC layer under poor lubrication conditions, thereby improving the wear resistance; at the same time, the W-DLC layer itself is corrosion-resistant and can prevent the formation of corrosion channels, thereby improving the corrosion resistance and further improving the service life of the component.

[0045] Compared with the commonly used joint bearing strengthening technologies, the present invention can effectively improve the wear resistance, self-lubricity and corrosion resistance of the key parts of the aircraft. The service life of the inner ring of the joint bearing is increased by more than 5 times compared with the existing products.

[0046] The present invention also provides a preparation method of the composite coating described in the above technical solution, including the following steps:

[0047] (1) A WC-CrC-Ni layer is obtained by supersonic plasma spraying on the surface of the substrate;

[0048] (2) On the surface of the WC-CrC-Ni layer obtained in step (1), a CrN layer and a W-DLC layer are sequentially prepared by chemical vapor deposition to obtain a composite coating.

[0049] The present invention has no special limitation on the sources of the raw materials, and commercially available products well-known to those skilled in the art can be used.

[0050] In the present invention, a WC-CrC-Ni layer is obtained by supersonic atmospheric plasma spraying (SAPS) on the surface of the substrate.

[0051] In the present invention, the substrate is preferably the inner ring of a spherical plain bearing; the outer diameter of the inner ring of the spherical plain bearing is preferably 30.995 - 31.005 mm; the inner diameter of the inner ring of the spherical plain bearing is preferably 14.988 - 15.015 mm; the surface roughness Ra of the spherical surface of the inner ring of the spherical plain bearing is preferably 0.2.

[0052] In the present invention, the substrate is preferably pretreated before use; the pretreatment includes cleaning, sandblasting, blowing compressed air, and preheating in sequence. Cleaning and sandblasting treatments in the present invention can remove surface impurities and oxide layers.

[0053] The present invention has no special limitation on the operation of the cleaning, and an industrial ultrasonic cleaning line well-known to those skilled in the art can be used for cleaning.

[0054] In the present invention, the pressure of the sandblasting is preferably 0.3 - 0.7 MPa. The present invention has no special limitation on the degree of the sandblasting, as long as the surface roughness Ra of the substrate after sandblasting is not less than 3.8 μm.

[0055] The present invention has no special limitation on the operation of blowing compressed air, as long as the surface floating dust and the sand dust in the inner cavity of the substrate can be removed.

[0056] In the present invention, the temperature of the preheating is preferably 60 - 100 °C; the preheating is preferably carried out by a spray gun. The present invention has no special limitation on the time of the preheating, as long as the temperature reaches 60 - 100 °C. Preheating the substrate in advance in the present invention can improve the bonding performance between the composite coating and the substrate.

[0057] In the present invention, the process parameters of the supersonic atmospheric plasma spraying preferably include: argon gas flow rate 170 - 260 slpm, current 400 - 500 A, voltage 100 - 160 V, powder feeding rate 20 - 60 g / min, spraying distance 100 - 120 mm. The spraying process adopted in the present invention can make the stress distribution of the WC-CrC-Ni layer more uniform, enabling the CrN layer and the W-DLC layer to better exert their excellent tribological properties.

[0058] As an implementation method, the process parameters of the supersonic plasma spraying can be: argon gas flow rate of 180 - 250 slpm, current of 420 - 480 A, voltage of 110 - 150 V, powder feeding rate of 25 - 50 g / min, spraying distance of 110 - 115 mm; or it can be: argon gas flow rate of 200 - 220 slpm, current of 430 - 450 A, voltage of 120 - 140 V, powder feeding rate of 30 - 40 g / min, spraying distance of 110 - 112 mm.

[0059] After the supersonic plasma spraying is completed, the present invention preferably grinds and polishes the product obtained by the supersonic plasma spraying to obtain a WC-CrC-Ni layer. The present invention uses grinding and polishing to make the surface of the WC-CrC-Ni layer flat.

[0060] The present invention has no special limitation on the operation of the grinding and polishing. The process well-known to those skilled in the art can be adopted as long as the size and precision requirements are met.

[0061] After obtaining the WC-CrC-Ni layer, the present invention sequentially prepares a CrN layer and a W-DLC layer on the surface of the WC-CrC-Ni layer by physical vapor deposition to obtain a composite coating.

[0062] In the present invention, before sequentially preparing the CrN layer and the W-DLC layer on the surface of the WC-CrC-Ni layer, it is preferred to perform high-energy plasma cleaning on the WC-CrC-Ni layer. The present invention uses high-energy plasma cleaning to remove the oxide layer existing on the surface of the coating.

[0063] In the present invention, the process parameters of the high-energy plasma cleaning preferably include: when the air pressure in the vacuum chamber reaches 2×10 -3 Pa under the heating state, introduce argon gas at 100 - 300 sccm, the air pressure in the vacuum chamber is 1.5 - 3.0 Pa, the temperature is 90 - 110 °C, the substrate bias voltage is -800 - -500 V, the ion source power is 1.0 - 2.0 kW, and the time is 30 - 60 min.

[0064] As an implementation method, the process parameters of the high-energy plasma cleaning can be: when the air pressure in the vacuum chamber reaches 2×10 -3 Pa under the heating state, introduce argon gas at 150 - 200 sccm, the air pressure in the vacuum chamber is 2.0 - 2.5 Pa, the temperature is 100 - 105 °C, the substrate bias voltage is -800 - -500 V, the ion source power is 1.5 - 2.0 kW, and the time is 50 - 60 min.

[0065] In the present invention, the physical vapor deposition method is preferably PVD or PECVD.

[0066] In the present invention, the process parameters of the vapor deposition method independently preferably include: vacuum chamber pressure 0.3~3.0Pa, nitrogen flow rate 0~2000sccm, methane flow rate 0~150sccm, argon flow rate 0~150sccm, temperature 90~400℃, substrate bias -150~-50V, ion source power 1.0~2.0kW, and deposition time 60~300min.

[0067] In the present invention, the vapor deposition method preferably uses an arc target or a magnetron target; the current of the arc target is 90 to 130A; the current of the magnetron target is 4 to 15A.

[0068] As an implementation mode, when preparing the CrN layer, the process parameters of the vapor deposition method can be: vacuum chamber pressure 0.3~0.5Pa, nitrogen flow rate gradually increasing from 20sccm to 50sccm, chromium target current 6~8A, temperature 90~100°C, substrate bias -80~-60V, ion source power gradually increasing from 1.2kW to 1.5kW, deposition time 60min.

[0069] As an implementation mode, when preparing the W-DLC layer, the process parameters of the vapor deposition method can be: vacuum chamber pressure 0.4Pa, argon gas flow rate 150sccm, methane gas flow rate gradually increasing from 80sccm to 120sccm, tungsten target current gradually decreasing from 10A to 4A, temperature 90-100°C, substrate bias gradually increasing from -80V to -50V, ion source power 2.0kW, deposition time 240min.

[0070] The present invention combines supersonic plasma spraying and vapor deposition technology through process optimization, thereby being able to further improve the wear resistance and corrosion resistance of the composite coating, thereby increasing the service life of the spherical bearing.

[0071] The present invention also provides the use of the composite coating described in the above technical solution or the composite coating prepared by the preparation method described in the above technical solution in the inner ring of a spherical bearing.

[0072] The operation of applying the composite coating to the inner ring of the spherical bearing of the present invention is the same as the aforementioned preparation method, and will not be repeated here.

[0073] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0074] Example 1

[0075] The composite coating consists of a WC-CrC-Ni layer, a CrN layer, and a W-DLC layer that are stacked:

[0076] The thickness of the WC-CrC-Ni layer is 200 μm;

[0077] The WC-CrC-Ni layer is composed of chemical components with the following mass percentages: Cr 21%, Ni 6%, C 5%, and the balance W;

[0078] The total thickness of the CrN layer and the W-DLC layer is 4.05 μm;

[0079] The thickness of the W-DLC layer is 2.55 μm;

[0080] The W content in the W-DLC layer is 10.5 at.%;

[0081] The preparation method of the composite coating is as follows:

[0082] (1) Use an industrial 7-tank ultrasonic cleaning line to clean the inner ring of a spherical plain bearing with an outer diameter of 30.605 - 30.615 mm, an inner diameter of 14.988 - 15.015 mm, a spherical surface roughness Ra of 0.2, and a material of 9Cr18. Then, perform dry sandblasting with a sandblasting pressure of 0.4 MPa to make the surface roughness Ra not less than 3.8 μm. Subsequently, use clean and dry compressed air to remove the surface floating dust and the sand dust in the inner cavity. After that, preheat the inner ring of the spherical plain bearing to 80 °C with a spray gun, and then perform supersonic plasma spraying. After grinding and polishing, a WC-CrC-Ni layer with a spherical surface roughness Ra of 0.2 is obtained; among them, the parameters of the supersonic plasma spraying are: argon gas flow rate 200 slpm, current 450 A, voltage 120 V, powder feeding rate 40 g / min, and spraying distance 100 mm;

[0083] (2) Perform high-energy plasma cleaning on the WC-CrC-Ni layer obtained in step (1). Then, use chemical vapor deposition to sequentially prepare the CrN layer and the W-DLC layer to obtain a composite coating with a spherical surface roughness Ra of 0.2; among them, the process parameters of the high-energy plasma cleaning are: when the air pressure in the vacuum chamber reaches 2×10 -3After reaching 2.0 Pa, argon gas was introduced at 200 sccm, the pressure in the vacuum chamber was 2.0 Pa, the temperature was 100 °C, the ion source power was 2.0 kW, and the substrate bias voltage was gradually increased from -800 V to -500 V over 60 min; when depositing the CrN layer, the process parameters were: the pressure in the vacuum chamber was 0.3 Pa, the nitrogen gas flow rate was gradually increased from 20 sccm to 50 sccm, the chromium target current was 6 A, the temperature was 90 °C, the substrate bias voltage was -80 V, and the ion source power was gradually increased from 1.2 kW to 1.5 kW, with a deposition time of 60 min; when depositing the W-DLC layer, the process parameters were: the pressure in the vacuum chamber was 0.4 Pa, the argon gas flow rate was 150 sccm, the methane gas flow rate was gradually increased from 80 sccm to 120 sccm, the tungsten target current was gradually decreased from 10 A to 4 A, the temperature was 90 °C, the substrate bias voltage was gradually increased from -80 V to -50 V, the ion source power was 2.0 kW, and the deposition time was 240 min.

[0084] The inner ring of the aviation joint bearing prepared in Example 1 was subjected to an in-flight test. The test results showed that under the conditions of corrosion, fretting, and poor lubrication, the service life of the inner ring of the joint bearing was increased by more than 5 times compared to the original 100 hours.

[0085] The schematic diagram of the structure of the composite coating prepared in Example 1 is as Figure 1 shown; the scanning electron microscope image of the composite coating prepared in Example 1 is as Figure 2 shown.

[0086] It can be seen from Figure 1 that the composite coating is composed of a WC-CrC-Ni layer, a CrN layer, and a W-DLC layer arranged in layers; it can be seen from Figure 2 that the WC-CrC-Ni layer is a flaky structure and there are certain voids, and the W-DLC layer has a dense structure.

[0087] After the composite coating prepared in Example 1 was installed, a wear experiment was carried out. The physical photo of the composite coating after the experiment is as Figure 3 shown; then the Figure 3 red box area was photographed and analyzed using a LEXT OLS5100 laser confocal scanning microscope. The high-resolution laser image of the wear scar in the red box area is as Figure 4 shown. The red dotted line part in the high-resolution laser image of the wear scar was measured, and the contour curve obtained from the measured data using Origin software is as Figure 5 shown ( Figure 5 the un-worn contour fitting curve in is the composite coating without the wear experiment), and the 3D topography image of the wear scar in the red box area is as Figure 6 shown.

[0088] It can be seen from Figures 3 - 6It can be seen that the inside of the worn area is smoother than the unworn area, with slight abrasions, the contour of the wear marks has a uniform transition, and there are no obvious steps in the contour line. According to the calculation of the fitted curve, the maximum loss height of the contour of the wear mark area after wear is 2.63 ± 0.17 μm, and the width of the maximum wear area < 2 mm, indicating that the composite coating of the present invention has excellent wear resistance.

[0089] Comparative Example 1

[0090] Existing product: Inner ring of an aviation joint bearing without coating

[0091] The composite coating prepared in Example 1 and the existing product of Comparative Example 1 were subjected to a neutral salt spray test. (The neutral salt spray test was carried out in accordance with GB / T 6461-2002. After 24 hours of spraying, for each collector, the solution collected was 1 - 2 mL / h for a height of 2000px, with a sodium chloride concentration of 50 ± 10 g / L and a pH value of 6.5 - 7.2.) There were 3 parallel specimens, which were inspected every 24 hours. The test was stopped when red rust stains appeared, and the test time was recorded and the corrosion condition of the specimens was photographed. The results are as Figures 7 - 10 shown, Figure 7 Figure [number] is a physical picture of the existing product of Comparative Example 1 before the neutral salt spray test, Figure 8 Figure [number] is a physical picture of the existing product of Comparative Example 1 after 24 hours of corrosion, Figure 9 Figure [number] is a physical picture of the composite coating prepared in Example 1 before the neutral salt spray test, Figure 10 Figure [number] is a physical picture of the composite coating prepared in Example 1 after 240 hours of corrosion.

[0092] From Figures 7 - 10 it can be seen that serious corrosion occurred in the existing product after 24 hours, and there was basically no change on the surface of the composite coating after 240 hours, indicating that the composite coating prepared in Example 1 has excellent corrosion resistance.

[0093] Example 2

[0094] The composite coating is composed of a WC-CrC-Ni layer, a CrN layer, and a W-DLC layer arranged in layers:

[0095] The thickness of the WC-CrC-Ni layer is 200 μm;

[0096] The WC-CrC-Ni layer is composed of chemical components with the following mass percentages: Cr 21%, Ni 6%, C 5%, and the balance W;

[0097] The total thickness of the CrN layer and the W-DLC layer is 4.15 μm;

[0098] The thickness of the W-DLC layer is 2.05 μm;

[0099] The W content in the W-DLC layer is 12.5 at.%.

[0100] The preparation method of the composite coating comprises the following steps:

[0101] (1) Use an industrial 7-tank ultrasonic cleaning line to clean the inner ring of a spherical plain bearing with an outer diameter of 30.605 - 30.615 mm, an inner diameter of 14.988 - 15.015 mm, a spherical surface roughness Ra of 0.2, and a material of 9Cr18. Then, perform dry sandblasting with a sandblasting pressure of 0.4 MPa to make the surface roughness Ra not less than 3.8 μm. Subsequently, use clean and dry compressed air to remove the surface floating dust and the sand dust in the inner cavity. After that, preheat the inner ring of the spherical plain bearing to 80 °C with a spray gun, and then perform supersonic plasma spraying. After grinding and polishing, a WC-CrC-Ni layer with a spherical surface roughness Ra of 0.2 is obtained. Among them, the parameters of the supersonic plasma spraying are: argon gas flow rate 200 slpm, current 450 A, voltage 120 V, powder feeding rate 40 g / min, and spraying distance 100 mm;

[0102] (2) Perform high-energy plasma cleaning on the WC-CrC-Ni layer obtained in the step (1). Then, use the chemical vapor deposition method to prepare a CrN layer and a W-DLC layer in sequence to obtain a composite coating with a spherical surface roughness Ra of 0.2. Among them, the process parameters of the high-energy plasma cleaning are: when the air pressure in the vacuum chamber reaches 2×10 -3 Pa under the heating state, introduce 200 sccm of argon gas, the air pressure in the vacuum chamber is 2.0 Pa, the temperature is 100 °C, the ion source power is 2.0 kW, the substrate bias voltage gradually increases from -800 V to -500 V, and the time is 60 min; when depositing the CrN layer, the process parameters are: the air pressure in the vacuum chamber is 0.3 Pa, the nitrogen gas flow rate gradually increases from 20 sccm to 50 sccm, the chromium target current is 6 A, the temperature is 100 °C, the substrate bias voltage is -80 V, the ion source power gradually increases from 1.2 kW to 1.5 kW, and the deposition time is 60 min; when depositing the W-DLC layer, the process parameters are: the air pressure in the vacuum chamber is 0.4 Pa, the argon gas flow rate is 150 sccm, the methane gas flow rate gradually increases from 80 sccm to 120 sccm, the tungsten target current gradually decreases from 12 A to 7.5 A, the temperature is 100 °C, the substrate bias voltage gradually increases from -80 V to -50 V, the ion source power is 2.0 kW, and the deposition time is 240 min.

[0103] Perform an in-flight test on the inner ring of the aviation spherical plain bearing prepared in Example 2. The test results show that under the conditions of corrosion and friction, the service life of the slide rail is increased by nearly 2 times compared with the original 1000 h.

[0104] The process parameters of the cleaning using the industrial 7-tank ultrasonic cleaning line in Examples 1 - 2 are shown in Table 1.

[0105] Table 1 Process parameters for cleaning using an industrial 7-tank ultrasonic cleaning line

[0106]

[0107]

[0108] The scanning electron micrograph of the composite coating prepared in Example 2 is as Figure 11 shown.

[0109] From Figure 11 it can be seen that the WC-CrC-Ni layer has a flaky structure and there are certain voids, and the W-DLC layer has a dense structure.

[0110] The wear resistance of the composite coating prepared in Example 2 and the existing product of Comparative Example 1 was tested using a pin-on-disk test. Test load: contact stress 0.24 MPa, corresponding to a machine load of 180 g, friction distance 200000 m, friction radius 8 mm, test speed 1000 r / min, total duration 3960 min. For the existing product, at a test duration of 863 min, due to the friction coefficient exceeding 1, the system was protected and the test ended. The specific wear rate was 3.2463E-7 mm 3 N -1 M -1 ; for the composite coating, the test duration was 872 min and the specific wear rate was 4.78148E-8 mm 3 N -1 M -1 .

[0111] The results of the wear resistance test of the composite coating prepared in Example 2 and the existing product of Comparative Example 1 using a pin-on-disk test are as Figures 12 - 14 shown,[[]]END]] Figure 12 is the wear depth curve on the wear baseline after the wear resistance test of Comparative Example 1; Figure 13 is the wear depth curve on the wear baseline after the wear resistance test of the composite coating prepared in Example 2; Figure 14 is the specific wear rate curve after the wear resistance of the composite coating prepared in Example 2 and Comparative Example 1.

[0112] From Figures 12 - 14 it can be seen that the composite coating prepared in Example 2 has excellent wear resistance.

[0113] The composite coating prepared in Example 2 was subjected to a neutral salt spray test (the neutral salt spray test was carried out in accordance with GB / T 6461-2002. After 24 h of spraying, the solution collected by each collector was 1-2 mL / h for a height of 2000px, with a sodium chloride concentration of 50±10 g / L and a pH value of 6.5-7.2). There were 3 parallel specimens, which were inspected every 24 h. The test was stopped when red rust stains appeared. The test time was recorded and the corrosion condition of the specimen was photographed. The results are as Figures 15 - 16 shown, Figure 15 Figure Figures 15 - 16 is a physical picture of the composite coating prepared in Example 2 before the neutral salt spray test, Figure 16 and Figure Figure 15 is a physical picture of the composite coating prepared in Example 2 after 240 h of corrosion.

[0114] As can be seen from Figures 15 - 16 Figure Figure 16 , after 240 h, the surface of the composite coating prepared in Example 2 showed basically no change, indicating that the composite coating has excellent corrosion resistance.

[0115] From the above examples and comparative examples, it can be seen that the composite coating provided by the present invention has excellent wear and corrosion resistance, thereby improving the service life of the articulated bearing.

[0116] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A composite coating, comprising a WC-CrC-Ni layer, a CrN layer and a W-DLC layer which are stacked.

2. The composite coating according to claim 1, characterized in that, The thickness of the WC-CrC-Ni layer is 195 - 200 μm.

3. The composite coating according to claim 1 or 2, characterized in that, The WC-CrC-Ni layer comprises chemical components with the following mass percentages: 20 - 22% of Cr, 5 - 7% of Ni, 4 - 6% of C and the balance of W.

4. The composite coating according to claim 1, wherein The total thickness of the CrN layer and the W-DLC layer is 3 - 5 μm.

5. The composite coating according to claim 4, wherein The thickness of the W-DLC layer is 2 - 4 μm.

6. The composite coating according to claim 1 or 5, characterized in that The W content in the W-DLC layer is 9 - 20 at.%.

7. A method for preparing the composite coating according to any one of claims 1 - 6, comprising the following steps: (1) Using supersonic plasma spraying on the surface of the substrate to obtain a WC-CrC-Ni layer; (2) Sequentially preparing a CrN layer and a W-DLC layer on the surface of the WC-CrC-Ni layer obtained in step (1) by chemical vapor deposition to obtain a composite coating.

8. The preparation method according to claim 7, characterized in that, The process parameters of the supersonic plasma spraying in step (1) include: argon gas flow rate of 170 - 260 slpm, current of 400 - 500 A, voltage of 100 - 160 V, powder feeding rate of 20 - 60 g / min, and spraying distance of 100 - 120 mm.

9. The preparation method according to claim 7, wherein The process parameters of the chemical vapor deposition in step (2) independently include: vacuum chamber pressure of 0.3 - 3.0 Pa, nitrogen gas flow rate of 0 - 2000 sccm, methane gas flow rate of 0 - 150 sccm, argon gas flow rate of 0 - 150 sccm, temperature of 90 - 400 °C, substrate bias voltage of -150 - -50 V, ion source power of 1.0 - 2.0 kW, and deposition time of 60 - 300 min.

10. Application of the composite coating according to any one of claims 1 - 6 or the composite coating prepared by the preparation method according to any one of claims 7 - 9 in the inner ring of a spherical plain bearing.

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