A wear-resistant and corrosion-resistant composite coating and preparation method thereof

Abstract

The present invention provides a wear-resistant and corrosion-resistant composite coating and a preparation method thereof, wherein the composite coating comprises n periodic coatings, each of which is sequentially stacked from bottom to top with Me1N x Layer and Me2N x layer, wherein Me1 is any one of Ti, Cr, and Nb, and Me2 is TiAl or CrAl. The method comprises: obtaining an alloy substrate to be protected; performing surface cleaning and etching on the alloy substrate to be protected; coating the surface of the alloy substrate to be protected by PVD technology to form a coating, wherein the coating comprises n periodic coatings; nitriding the composite area of ​​the film substrate by ion nitriding technology to form a gradient transition of the N element to obtain a composite coating. By using the composite treatment technology of first coating and then nitriding, the hardness of the coating is improved, the toughness of the coating is achieved, the bonding strength of the film substrate is further significantly improved, and the wear and corrosion resistance of the substrate is enhanced, while ensuring good toughness of the coating.

Description

Technical Field

[0001] The invention relates to the technical field of wear-resistant and corrosion-resistant protective manufacturing of engineering materials, and in particular to a wear-resistant and corrosion-resistant composite coating and a preparation method thereof. Background Art

[0002] Titanium alloys are widely used in aerospace and other fields due to their excellent comprehensive properties such as high specific strength, good thermal stability, and corrosion resistance. However, due to the low surface hardness, poor friction and wear resistance, and poor resistance to solid particle erosion, the scope of application of titanium alloys is severely limited. For example, when titanium alloys come into contact with other metals, micro-motion and adhesive wear are prone to occur, resulting in contact corrosion; when titanium alloy parts on aircraft are impacted by solid particles such as gravel and dust, the size and shape of the parts are easily damaged, resulting in reduced performance.

[0003] To address the above problems, plasma nitriding technology is currently used to form a high-strength, high-wear-resistant nitrided layer on the surface of titanium alloy. This technology has the advantages of high efficiency, good nitrided layer quality and no bonding problems. Then, physical vapor deposition (PVD) is used to prepare metal nitride hard coating, which can form a good hardness gradient.

[0004] However, the inventors of the present application discovered that the above-mentioned prior art has at least the following technical problems in the process of implementing the technical solution of the embodiment of the present application:

[0005] In the process of treating the titanium alloy surface in the existing technology, oxidation is unavoidable due to the process of nitriding first and then coating. In addition, alternating use of equipment is also prone to surface oxidation, thereby forming an oxide layer at the membrane-substrate interface, resulting in a technical problem of poor membrane-substrate bonding performance. Summary of the invention

[0006] The embodiment of the present invention provides a wear-resistant and corrosion-resistant composite coating and a preparation method thereof, which is used to solve the technical problem that in the process of treating the titanium alloy surface in the prior art, oxidation phenomenon is unavoidable due to the process of first nitriding and then coating, and the alternating use of equipment is also prone to surface oxidation, thereby forming a film-substrate interface oxide layer, resulting in poor film-substrate bonding performance. Through the composite treatment technology of first coating and then nitriding, the coating hardness is improved, the toughness of the coating is achieved, the film-substrate bonding strength is further significantly improved, and the wear and corrosion resistance of the substrate is enhanced.

[0007] In view of the above problems, on the one hand, the present invention provides a wear-resistant and corrosion-resistant composite coating, which is applied to the surface of a titanium alloy or other alloy substrate, characterized in that the composite coating comprises n periodic coatings, wherein each of the periodic coatings is sequentially stacked from bottom to top with Me1N x Layer and Me2Nx layer, wherein Me1 is any one of Ti, Cr, and Nb, and Me2 is TiAl or CrAl.

[0008] Preferably, the value range of x is 0-1.

[0009] Preferably, the value range of n is 20-120.

[0010] On the other hand, the present invention also provides a method for preparing a wear-resistant and corrosion-resistant composite coating, the method comprising: obtaining an alloy substrate to be protected; performing surface cleaning and etching on the alloy substrate to be protected; coating the surface of the alloy substrate to be protected by PVD technology to form a coating, wherein the coating comprises n periodic coatings; and performing nitriding treatment on the film-based composite area by ion nitriding technology to form a gradient transition of the N element to obtain a composite coating.

[0011] Preferably, the surface cleaning and etching of the alloy substrate to be protected comprises: performing ion bombardment cleaning on the alloy substrate to be protected for 25 minutes; and then performing metal ion and high-energy electron co-cleaning and etching on the alloy substrate to be protected for 25 minutes.

[0012] Preferably, the surface of the alloy substrate to be protected is plated by PVD technology to form a coating, including: using argon and nitrogen as reaction gases at the same time; reacting a small amount of N element with a metal target; and performing arc ion plating on the alloy substrate to be protected under certain conditions, wherein the arc ion plating treatment time is 120 to 3600 minutes.

[0013] Preferably, the method of nitriding the composite area of ​​the film base by ion nitriding technology to form a gradient transition of the N element to obtain a composite coating includes: using glow ion nitriding technology, the vacuum degree can be 5.0×10 -3 -2.0×10 -2 Pa; heating the coated alloy substrate to be protected to 400-800° C. by a heater; introducing ammonia gas and adjusting the gas pressure to 200-1000 Pa; applying a 300-800V DC power supply between the cathode and the anode; and the nitriding treatment time is 1-30 hours.

[0014] The above one or more technical solutions in the embodiments of the present application have at least one or more of the following technical effects:

[0015] The embodiment of the present invention provides a wear-resistant and corrosion-resistant composite coating and a preparation method thereof, the method comprising: obtaining an alloy substrate to be protected; cleaning and etching the surface of the alloy substrate to be protected; coating the surface of the alloy substrate to be protected by PVD technology to form a coating, wherein the coating comprises n periodic coatings; nitriding the composite area of ​​the film substrate by ion nitriding technology to form a gradient transition of the N element to obtain a composite coating. It is used to solve the technical problem that in the process of treating the titanium alloy surface in the prior art, oxidation is unavoidable due to the process of nitriding first and then coating, and the alternating use of equipment is also prone to surface oxidation, thereby forming an oxide layer at the film-substrate interface, resulting in poor film-substrate bonding performance. Through the composite treatment technology of coating first and then nitriding, the coating hardness is improved, the coating toughness is achieved, the film-substrate bonding strength is further significantly improved, and the wear-resistant and corrosion-resistant performance of the substrate is enhanced.

[0016] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of a wear-resistant and corrosion-resistant composite coating and a preparation method thereof provided in an embodiment of the present invention;

[0018] Figure 2 Schematic diagram of the structure of the composite coating in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The embodiment of the present invention provides a wear-resistant and corrosion-resistant composite coating and a preparation method thereof, which solves the technical problem that in the prior art, during the surface treatment of titanium alloy, oxidation is unavoidable due to the process of nitriding first and then coating, and the alternating use of equipment is also prone to cause surface oxidation, thereby forming an oxide layer at the membrane-substrate interface, resulting in poor membrane-substrate bonding performance.

[0020] The overall idea of ​​the technical solution provided by the present invention is as follows: obtain an alloy substrate to be protected; perform surface cleaning and etching on the alloy substrate to be protected; perform film coating on the surface of the alloy substrate to be protected by PVD technology to form a film coating, wherein the film coating comprises n periodic coatings; perform nitriding treatment on the composite area of ​​the film substrate by ion nitriding technology to form a gradient transition of the N element to obtain a composite coating. Through the composite treatment technology of first coating and then nitriding, the hardness of the coating is improved, the toughness of the coating is achieved, and the bonding strength of the film substrate is further significantly improved, and the wear and corrosion resistance of the substrate is enhanced, while ensuring good toughness of the coating.

[0021] The technical solution of the present invention is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present application and the specific features in the embodiments are detailed descriptions of the technical solution of the present application, rather than limitations on the technical solution of the present application. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments can be combined with each other.

[0022] The term "and / or" in this article is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0023] Embodiment 1

[0024] The embodiment of the present invention provides a wear-resistant and corrosion-resistant composite coating, which is applied to a titanium alloy or other alloy substrate surface, and is characterized in that the composite coating comprises n periodic coatings, wherein each of the periodic coatings is sequentially stacked from bottom to top with Me1N x Layer and Me2N x layer, wherein Me1 is any one of Ti, Cr, and Nb, and Me2 is TiAl or CrAl.

[0025] Furthermore, the value range of x is 0 to 1.

[0026] Furthermore, the value range of n is 20 to 120.

[0027] Specifically, the composite coating is applied to the surface of a titanium alloy or other alloy substrate to protect the basic surface of the alloy, wherein the composite coating comprises a plurality of stacked periodic coatings, each of which is stacked from bottom to top with Me1N x Layer and Me2N x layer, among which Me1N x and Me2N x The layers are all metal-rich layers, and the metal content is much higher than the N content. Not all nitride ceramic phases are formed in the layer structure. This type of structure has low hardness, so further nitriding treatment is required. After nitriding treatment, the composite coating and titanium alloy substrate form a concentration gradient of N atoms from the surface to the inside, which gradually decreases and transitions. The high hardness of the surface layer provides good wear resistance. The multilayer structure can resist erosion in the vertical direction, and plays a role in dispersing and consuming particle energy. The membrane-base interface also forms interface mixing and even mutual diffusion due to the infiltration of N atoms, thereby achieving the technical effect of significantly improving the membrane-base bonding strength.

[0028] In the present application, each of the periodic coatings contains the above-mentioned Me1N x and Me2N x In the double-layer structure, the position relationship between the layers is preferably to deposit the layer with lower hardness first, and then deposit the layer with higher hardness, so as to form a hardness gradient, so as to improve the bonding strength. x The hardness of the layer is lower than that of Me2N x layer, so it is preferred to form Me1N x -Me2N x The order of Me1N x Layer and Me2N x The x in the layer can take any value between 0 and 1, Me1 can be selected from any one of Ti, Cr, and Nb, and Me2 can be selected from any one of TiAl or CrAl. The hardness, wear resistance and high temperature resistance of the composite coating are effectively improved through the multilayer structure and the addition of Al element. At the same time, the nitriding technology can also be used to refine the grains of the deposited coating, optimize defects, and further improve the overall performance of the composite coating.

[0029] Specifically, the composite coating comprises 20 to 120 periodic coatings. Since each of the periodic coatings comprises Me1N x and Me2N x Double-layer structure, that is, the composite coating comprises 40 to 240 layers, wherein Me1N x The thickness of the layer may preferably be 50 to 1000 nm. x The thickness of the layer may preferably be 50 to 1000 nm. x Layer with Me2N x The thickness ratio of the layers can be preferably 1:6 to 6:1, so the thickness of each periodic coating is 100 to 2000 nm, the total thickness of the composite coating can be preferably 2 to 60 μm, and the thickness of the nitriding layer is calculated as a whole from the surface coating to the surface area of ​​the substrate such as titanium alloy, and its thickness can be preferably 50 to 250 μm. The above are all preferred ranges, and the actual values ​​are not limited to the preferred ranges. By limiting the thickness of each layer, the single-phase layer and the multi-phase layer cooperate with each other within a suitable hardness range, which, on the one hand, allows the composite coating to maintain good toughness, and on the other hand, it also achieves the technical effect of improving the bonding force between the film layers and reducing the internal stress.

[0030] It is known from a large amount of experimental data that the hardness of the composite coating can reach 2182~3221HV, the film-base bonding strength can reach 75~95N, the erosion rate of the composite coating at a 30° attack angle is 0.064~0.158μm / g, and the erosion rate at a 90° attack angle is 0.875~1.239μm / g. The embodiment of the present invention improves the strengthening and toughness of the coating by controlling the structure, elements and processes of the composite coating, and the internal stress is controlled, thereby achieving a reasonable match between the hardness and toughness of the composite coating. Under the premise of a thicker coating, the bonding strength between the coating and the substrate can be ensured to be above 75N, which is beneficial to improving the wear and corrosion resistance of the substrate, and further effectively improving the working efficiency and service life of the substrate material.

[0031] Embodiment 2

[0032] Figure 1 FIG. 1 is a schematic flow chart of a wear-resistant and corrosion-resistant composite coating and a preparation method thereof according to an embodiment of the present invention. Figure 1 As shown, an embodiment of the present invention provides a wear-resistant and corrosion-resistant composite coating and a preparation method thereof, the method comprising:

[0033] Step S110: obtaining an alloy substrate to be protected;

[0034] Step S120: cleaning and etching the surface of the alloy substrate to be protected;

[0035] Furthermore, the surface cleaning and etching of the alloy substrate to be protected includes:

[0036] The alloy substrate to be protected is cleaned by ion bombardment for 25 minutes;

[0037] The alloy substrate to be protected is then cleaned and etched by metal ions and high-energy electrons for 25 minutes.

[0038] Specifically, there may be rust, oil and other pollutants on the surface of the titanium alloy or other alloy substrate to be protected, so the surface of the alloy substrate to be protected needs to be cleaned and etched. The embodiment of the present invention adopts ion bombardment cleaning and metal ion cleaning technology. First, the alloy substrate to be protected is ion bombarded and cleaned for 25 minutes under the conditions of a pulse negative bias voltage of 700-1000V, a furnace pressure of 0.5-2Pa and an argon gas flow rate of 50-500sccm; then, the alloy substrate to be protected is metal ion cleaned for 25 minutes under the condition of a target current of 70-120A, so as to achieve the purpose of cleaning the surface of the alloy substrate.

[0039] Step S130: coating the surface of the alloy substrate to be protected by PVD technology to form a coating, wherein the coating includes n periodic coatings;

[0040] Step S140: performing nitriding treatment on the film-based composite area by ion nitriding technology to form a gradient transition of N elements to obtain a composite coating.

[0041] Specifically, PVD is the abbreviation of Physical Vapor Deposition, which means a surface treatment technology that uses low voltage and high current arc discharge technology under vacuum conditions, uses gas discharge to evaporate the target material and ionizes both the evaporated material and the gas, and uses the acceleration of the electric field to deposit the evaporated material and its reaction products on the workpiece. Due to the low surface hardness, poor friction and wear resistance and resistance to solid particle erosion of titanium alloys, the embodiment of the present invention first uses PVD technology to plate the surface of the alloy substrate to be protected to form a coating, wherein the coating includes a plurality of stacked periodic coatings, each of which is sequentially prepared with Me1N x Layer and Me2N x Layers are formed to form a multi-layered metal-rich layer, which is well bonded to the alloy substrate to be protected and has low stress, and can be prepared into an ultra-thick coating. Based on the excellent toughness of the metal-rich layer, the improvement of the erosion resistance requires the hardness and toughness of the coating to match. It is not easy to toughen the hard coating, but it is relatively simple to harden the tough layer. Figure 2 As shown, after the embodiment of the present application deposits the metal-rich toughness layer by PVD technology, the ion nitriding technology is used to harden the coating and the surface of the substrate, and finally the coating is strengthened and toughened. At the same time, through the nitriding treatment, N atoms can reach the substrate and form a nitriding diffusion layer on the surface of the substrate, thereby solving the "eggshell effect" of soft substrate-hard coating.

[0042] Arc ion plating is used in PVD technology, which has a high deposition rate, but it will inevitably form large particle defects on the surface. However, nitriding treatment can use the longitudinal channels of particle defects in the coating to diffuse to the substrate to form a deeper nitriding layer. Due to the characteristics of nitriding technology, the surface of the coating is bombarded to remove surface defects during the formation of nitrides, and it plays a role in squeezing large particles and refining grains inside the coating. Magnetron sputtering ion plating has a relatively low deposition rate, but the structure of the coating prepared is dense, which provides a good foundation for nitriding treatment. After nitriding treatment with these two technologies, the composite coating can obtain good surface quality and wear and corrosion resistance.

[0043] The above composite coating preparation technology is used to prepare the erosion-resistant coating, which can effectively alleviate the wear phenomenon on the surface of the substrate, especially the titanium alloy substrate, and improve the erosion resistance. The engineering material with the above composite coating on the substrate has good erosion and wear resistance, which can improve work efficiency and extend service life.

[0044] In step S130, the surface of the alloy substrate to be protected is plated by PVD technology to form a coating, including: using argon and nitrogen as reaction gases at the same time, wherein Me1N x The target material of the layer is Ti, Cr or Nb, Me2N x The layer uses TiAl or CrAl target as the target material, and a small amount of N element reacts with the metal target material. The metal content in the finally generated coating structure is higher than the N content, that is, the effect of the metal-rich phase in the layer structure is achieved. The alloy substrate to be protected is subjected to arc ion plating treatment under the conditions of gas pressure of 0.5-4Pa, pulse negative bias voltage of 60-150V, and target current of 70-120A, wherein the arc ion plating treatment time is 120-3600min. Under the deposition conditions, the alloy substrate to be protected and the coating can have a strong bonding force.

[0045] In step S140, the ion nitriding technology is used to nitride the composite area of ​​the film base to form a gradient transition of the N element to obtain a composite coating, including: using the glow ion nitriding technology at 5.0×10 -3 ~2.0×10 -2 Pa, the coated alloy substrate to be protected is heated to 400-800°C by a heater, ammonia is introduced, the gas pressure is adjusted to 200-1000Pa, a DC power supply of 300-800V is applied between the cathode and the anode, and the workpiece is treated for 1-30h.

[0046] After nitriding treatment, the hardness and film-base bonding performance of the coating can be effectively improved. The formation of nitrides will expand the volume of the coating, repair and fill the defects of the coating (such as gaps between large particles, microcracks, etc.). Modification of the coating can not only improve the hardness, toughness and adhesion of the coating, but also regulate and repair the structural defects of the coating, and improve the comprehensive performance of the composite coating.

[0047] Embodiment 3

[0048] The embodiment of the present invention provides a method for preparing a composite coating on a TC4 titanium alloy substrate, which is specifically as follows:

[0049] TC4 titanium alloy was used as the substrate. During the PVD coating preparation, the background vacuum was set to 3.0×10 -3 Pa, and the workpiece speed was set to 0.5 rpm.

[0050] Under the conditions of gas pressure of 1Pa and pulse negative bias voltage of 900V, ion bombardment cleaning was carried out for 25min; then metal ion and high-energy electron co-cleaning etching was carried out for 25min under the condition of target current of 90A.

[0051] Arc ion plating was performed for 900 min using Ti target and TiAl target as target materials, argon and nitrogen as reaction gases, and a gas pressure of 2 Pa, a negative bias voltage of 100 V, and a target current of 90 A.

[0052] Preparation of 33 Me1N x -Me2N x Periodic coating, where each periodic coating has a thickness of 450nm, and Me1N x The layer thickness is 150nm, Me2N x The layer thickness is 300 nm. Finally, a coating layer with a thickness of 15 μm is deposited on the substrate surface.

[0053] During nitriding treatment, the vacuum degree is set to 8×10 -3 Pa, turn on the heater to heat the workpiece to 500℃; introduce ammonia gas with a pressure of 500Pa; apply a 500V DC power supply between the cathode and anode; the nitriding treatment time can be 5h. Finally, a nitriding layer with a thickness of 50μm is obtained.

[0054] The hardness of the composite coating is 2782 HV, the bonding force is 86 N, the erosion rate is 0.092 μm / g at an attack angle of 30°, and the erosion rate is 1.036 μm / g at an attack angle of 90°.

[0055] At the same time, the erosion wear test was carried out under the same erosion conditions using the same titanium alloy substrate. The results showed that the erosion rate was 3.572μm / g at a 30° attack angle and 8.631μm / g at a 90° attack angle. This shows that the high-angle erosion resistance of the erosion-resistant coating is more than eight times higher than that of the titanium alloy substrate, thereby effectively improving the erosion and wear resistance of the substrate.

[0056] Embodiment 4

[0057] The embodiment of the present invention provides a method for preparing a composite coating on a nickel-based alloy substrate, which is specifically as follows:

[0058] When using nickel-based alloy as the substrate and PVD coating preparation, the background vacuum is set to 5.0×10 -3 Pa, and the workpiece speed was set to 3 rpm.

[0059] Under the conditions of gas pressure of 2Pa and pulse negative bias voltage of 800V, ion bombardment cleaning was carried out for 40min; then metal ion and high-energy electron co-cleaning etching was carried out for 20min under the condition of target current of 110A.

[0060] Arc ion plating was performed for 2700 min with Nb target and TiAl target as target materials and argon and nitrogen as reaction gases under the conditions of gas pressure of 4 Pa, negative bias voltage of 120 V and target current of 120 A.

[0061] Prepare 50 Me1N x -Me2N x Periodic coating, where each periodic coating has a thickness of 900nm, and Me1N x The layer thickness is 600nm, Me2N x The layer thickness is 300 nm. Finally, a coating layer with a thickness of 45 μm is deposited on the substrate surface.

[0062] During nitriding treatment, the vacuum degree is set to 2×10 -2 Pa, turn on the heater to heat the workpiece to 700℃; introduce ammonia gas with a pressure of 800Pa; apply a DC power supply of 800V between the cathode and anode; the nitriding treatment time can be 15h. Finally, a nitriding layer with a thickness of 150μm is obtained.

[0063] The composite coating has a hardness of 2451 HV, a bonding force of 79 N, an erosion rate of 0.126 μm / g at an attack angle of 30°, and an erosion rate of 1.239 μm / g at an attack angle of 90°.

[0064] At the same time, the erosion wear test was carried out under the same erosion conditions using the same nickel-based alloy substrate. The results showed that the erosion rate was 0.893 μm / g at a 30° attack angle and 10.953 μm / g at a 90° attack angle. This shows that the high-angle erosion resistance of the erosion-resistant coating is more than eight times higher than that of the nickel-based alloy substrate, thereby effectively improving the erosion and wear resistance of the substrate.

[0065] The above one or more technical solutions in the embodiments of the present application have at least one or more of the following technical effects:

[0066] The embodiment of the present invention provides a wear-resistant and corrosion-resistant composite coating and a preparation method thereof, the method comprising: obtaining an alloy substrate to be protected; cleaning and etching the surface of the alloy substrate to be protected; coating the surface of the alloy substrate to be protected by PVD technology to form a coating, wherein the coating comprises n periodic coatings; nitriding the composite area of ​​the film substrate by ion nitriding technology to form a gradient transition of the N element to obtain a composite coating. It is used to solve the technical problem that in the process of treating the titanium alloy surface in the prior art, oxidation is unavoidable due to the process of nitriding first and then coating, and the alternating use of equipment is also prone to surface oxidation, thereby forming an oxide layer at the film-substrate interface, resulting in poor film-substrate bonding performance. Through the composite treatment technology of coating first and then nitriding, the coating hardness is improved, the coating toughness is achieved, the film-substrate bonding strength is further significantly improved, and the wear-resistant and corrosion-resistant performance of the substrate is enhanced.

[0067] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0068] Obviously, those skilled in the art can make various changes and modifications to the embodiments of the present invention without departing from the spirit and scope of the embodiments of the present invention. Thus, if these modifications and variations of the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A wear-resistant and corrosion-resistant composite coating, the composite coating is applied on the surface of a titanium alloy or other alloy substrate, characterized in that: The composite coating comprises n periodic coatings, wherein each of the periodic coatings is sequentially stacked from bottom to top with Me1N x Layer and Me2N x layer, among which Me1N x The hardness of the layer is lower than that of Me2N x layer, forming Me1N x -Me2N x The order is, wherein Me1 is any one of Ti, Cr, and Nb, and Me2 is TiAl or CrAl; Among them, the value range of x is 0~1, excluding 0; The value range of n is 20~120.

2. A method for preparing a wear-resistant and corrosion-resistant composite coating, for preparing the wear-resistant and corrosion-resistant composite coating as claimed in claim 1, characterized in that: The method comprises: obtaining an alloy substrate to be protected; Performing surface cleaning and etching on the alloy substrate to be protected; The surface of the alloy substrate to be protected is plated by PVD technology to form a plated coating, wherein the plated coating comprises n periodic coatings; The composite area of ​​the membrane base is nitrided by ion nitriding technology to form a gradient transition of the N element to obtain a composite coating.

3. The method according to claim 2, characterized in that The surface cleaning and etching of the alloy substrate to be protected comprises: The alloy substrate to be protected is cleaned by ion bombardment for 25 minutes; The alloy substrate to be protected is then cleaned and etched by metal ions and high-energy electrons for 25 minutes.

4. The method according to claim 2, characterized in that The method of coating the surface of the alloy substrate to be protected by PVD technology to form a coating layer comprises: Argon and nitrogen are used as reaction gases at the same time; A small amount of N element reacts with the metal target; The alloy substrate to be protected is subjected to arc ion plating treatment under certain conditions, wherein the arc ion plating treatment time is 120 to 3600 minutes.

5. The method according to claim 2, characterized in that The method of nitriding the composite area of ​​the membrane substrate by ion nitriding technology to form a gradient transition of the N element to obtain a composite coating includes: Using glow ion nitriding technology, the vacuum degree can be 5.0×10 -3 -2.0×10 -2 Pa; The coated alloy substrate to be protected is heated to 400-800° C. by a heater; Introduce ammonia and adjust the pressure to 200~1000Pa; Apply a 300~800V DC power supply between the cathode and the anode; The nitriding treatment time is 1~30h.

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