Gradient nanocrystalline nitride coating structure with erosion resistance and fatigue resistance and preparation method

Abstract

The invention provides an anti-erosion and anti-fatigue gradient nanocrystalline nitride coating structure and a preparation method thereof, and aims to solve the problems that an existing gradient structure nitride coating easily causes fatigue failure of a base body under a fatigue load, and when an existing physical vapor deposition technology is used for preparing the gradient structure nitride coating, the fatigue failure of the base body is easily caused. And only nano-scale crystal grains of several nanometers to dozens of nanometers can be prepared, and micron-scale crystal grains cannot be prepared. According to the preparation method, the process of combining magnetic filtration ion plating and in-situ annealing is adopted, the grain sizes of the prepared nitride layers are sequentially reduced in a gradient mode from bottom to top, micron-sized grains on the bottommost layer have high plastic deformation resistance, formation of slippage steps on the surface of a base material can be restrained under low stress, and the fatigue limit of a metal matrix is improved; the nanoscale crystal grains on the topmost layer have high deformation coordination capacity, the anti-cracking capacity of the coating under high stress can be improved, and the sand and dust erosion resistance is enhanced.

Description

Technical Field

[0001] The present invention relates to a nitride coating structure and a preparation method thereof, and particularly to a gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance and a preparation method thereof. Background Art

[0002] Since the desertified, desert and sandy areas in China are vast, accounting for about 45% of the national land area, higher requirements are put forward for the environmental adaptability of aircraft. As the core component of an aircraft, when the compressor blades of an aeroengine serve in harsh environments such as deserts, they face severe sand erosion problems. Sand particles impact the blades at high speed, resulting in the destruction of the blade shape and structural integrity, seriously affecting the performance and reliability of the aeroengine. This problem is particularly prominent in aircraft such as helicopters and transport aircraft. For example, when a helicopter or transport aircraft performing tasks in desert areas takes off and lands, the engine will inhale high-concentration and high-hardness sand dust, causing damage to the compressor blades, with high maintenance costs and affecting flight safety. Therefore, sand erosion has become a key problem affecting the combat use of advanced aeroengines in sandy environments.

[0003] Currently, introducing a nitride coating on the surface of the compressor blades of an aeroengine has become an effective way to improve its sand erosion resistance. The nitride coating has high hardness and good strength and toughness, and although it can resist the impact of sand dust to a certain extent, existing research has found that there are differences in the elastic modulus and co-deformation performance between the nitride coating and the metal matrix. Under fatigue loads, the nitride coating is prone to crack prior to the metal matrix, accelerating the fatigue failure of the metal matrix. Under fatigue loads such as tension-tension, rotational bending or vibration generated by the high-speed rotation of the blades, the nitride coating will significantly reduce the fatigue resistance of the metal matrix, and different nitride coatings will cause different degrees of decline in the fatigue limit of the metal matrix under different loading forms. For example, in some tests, the fatigue limit of a titanium alloy matrix can be reduced by more than 50% under a certain number of cycles by a specific nitride coating. Although there are certain research results on the influence mechanism of the nitride coating on the fatigue resistance of the metal matrix, the existing nitride coatings still cannot ensure that the fatigue resistance of the metal matrix is not affected.

[0004] Currently, in the application of compressor blades of aeroengines, although research has shown that gradient structure nitride coatings based on different materials can improve the mechanical and erosion resistance of the coatings, this gradient structure nitride coating also has problems such as large differences in elastic modulus and co-deformation performance with the metal matrix and being prone to cause matrix fatigue failure under fatigue loads. In addition, when the existing physical vapor deposition technology is used to prepare gradient structure nitride coatings, only nanoscale grains with a size of a few nanometers to dozens of nanometers can be prepared, and micron-sized grains cannot be prepared. Therefore, it is extremely urgent to develop a coating structure with both erosion resistance and fatigue resistance. Summary of the Invention

[0005] The object of the present invention is to provide a gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance and a preparation method thereof, aiming at the technical problems existing in the existing gradient structure nitride coatings based on different materials, such as large differences in elastic modulus and co-deformation performance with the metal matrix, which are prone to cause matrix fatigue failure under fatigue loads, and the existing physical vapor deposition technology can only achieve the preparation of nanoscale grains from a few nanometers to dozens of nanometers when preparing gradient structure nitride coatings, and cannot achieve the preparation of micron-sized grains.

[0006] In order to achieve the above object, the technical solution provided by the present invention is as follows:

[0007] A preparation method of a gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance is characterized in that it includes the following steps:

[0008] Step 1, injecting metal ions on the roughened surface of the metal matrix to form a metal ion layer;

[0009] Step 2, using magnetron filtered vacuum cathodic arc deposition method to deposit nitride on the upper surface of the metal ion layer, and then performing annealing treatment to coarsen the grains of the nitride, forming a nitride layer with a grain size of nanoscale;

[0010] Step 3, using the method of Step 2 to prepare a new nitride layer on the upper surface of the currently formed nitride layer until the final grain size of the bottom nitride layer is coarsened to micron-scale, obtaining a gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance.

[0011] Further, in Step 2, the grain size of the nitride layer is 90 - 200 nm;

[0012] In Step 3, the final grain size of the bottom nitride layer is 1 - 2 μm.

[0013] Further, in Step 2 and Step 3, the deposition temperature of the nitride is 450 - 550 °C, the deposition time is 3.5 - 4 h, the annealing temperature is 400 - 500 °C, and the annealing time is 5 - 10 h.

[0014] Further, in Step 2 and Step 3, the deposition temperature of the nitride is 500 °C, the deposition time is 3.5 h, the annealing temperature is 500 °C, and the annealing time is 10 h.

[0015] Further, in Step 2, using magnetron filtered vacuum cathodic arc deposition method to deposit nitride on the upper surface of the metal ion layer specifically as:

[0016] Nitrogen is introduced into the vacuum coating chamber, and the nitrogen flow rate is controlled by a programmable flow controller to ionize it into N ions in a plasma environment. At the same time, the target metal forms metal ions through cathodic arc discharge; a bias voltage is applied to form nitrides on the upper surface of the metal ion layer by the metal ions and N ions.

[0017] Further, step 1 is specifically as follows:

[0018] The surface of the metal substrate is roughened by plasma etching technology, and metal ions are implanted into the roughened metal substrate surface by high-energy ion bombardment of a metal vacuum vapor ion source, so that a metal ion layer is formed on the metal substrate surface.

[0019] Further, in step 1, the vacuum degree of the metal vacuum vapor ion source is 1.0×10 -4 ~1.0×10 - 3 Pa, without heating, the implantation voltage is 6 - 15 kV, the beam current intensity is 4 - 10 mA, and the temperature in the furnace during implantation is 30 - 40 °C;

[0020] In step 2, when depositing nitrides by the magnetron filtered vacuum cathodic arc deposition method, the bias voltage is set to 250 V, the target current of the equipment is maintained at 110 ± 1 A, the duty cycle is maintained at 90 ± 0.1%, and the nitrogen flow rate introduced into the vacuum coating chamber is 30 sccm.

[0021] In addition, the present invention also provides a gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance, which is prepared by the above method.

[0022] Further, it includes a metal ion layer and a gradient cycle layer deposited on the upper surface of the metal ion layer;

[0023] The lower surface of the metal ion layer is used to contact the metal substrate surface, and its thickness is 60 - 200 nm;

[0024] The gradient cycle layer includes M nitride layers stacked in sequence from bottom to top on the upper surface of the metal ion layer, 1 < M ≤ 10;

[0025] The grain sizes of the M nitride layers gradually decrease from bottom to top, and the bottom nitride layer has micron-sized grains, and the top nitride layer has nano-sized grains.

[0026] Further, the grain size of the top nitride layer is 90 - 200 nm, and the grain size of the bottom nitride layer is 1 - 2 μm;

[0027] The nitride layer is a TiN layer, and the thicknesses of the nitride layers are the same;

[0028] The thickness of the metal ion layer is 100-160 nm, and the total thickness of the gradient circulation layer is 10-30 μm.

[0029] The beneficial effects of the present invention compared to the prior art are as follows:

[0030] 1. The present invention provides a method for preparing a gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance. The method adopts a process combining magnetic filtration ion plating and in-situ annealing. The grain sizes of the prepared multiple nitride layers decrease gradually from bottom to top. The bottom nitride layer is coarsened to micron-sized grains. This area has a high resistance to plastic deformation and can inhibit the formation of slip steps on the substrate surface under low stress, thereby improving the fatigue limit of the metal matrix. At the same time, the top nitride layer is nanometer-scale. This area has a strong coordinated deformation ability, which can effectively improve the coating's resistance to cracking under high stress and enhance the coating's resistance to sand and dust erosion. The two work together to achieve excellent erosion resistance and fatigue resistance. This process has high controllability and repeatability, and can stably prepare gradient nanocrystalline nitride coatings with excellent performance.

[0031] 2. The preparation method of the gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance provided by the present invention realizes precise control of the degree of grain coarsening of the nitride layer by precisely controlling the process parameters of magnetic filtration ion plating, such as deposition temperature, deposition time, and in-situ annealing temperature and time.

[0032] 3. The present invention introduces high-energy ion bombardment treatment of a metal vacuum steam ion source during the preparation of the metal ion layer, which further enhances the density and interface bonding strength of the coating and improves the overall performance of the coating.

[0033] 4. The present invention provides a gradient nanocrystalline nitride coating structure that is both erosion-resistant and fatigue-resistant. It innovatively reduces the grain size of multiple nitride layers from bottom to top in a gradient manner to achieve a gradient change in the coating. Compared with traditional single-structure or gradient-structured nitride coatings based on different materials, the gradient nanocrystalline nitride coating structure of the present invention can better coordinate deformation when subjected to sand and dust erosion and fatigue loads, reduce the initiation and expansion of cracks, and significantly improve the service life and protective effect of the coating. It can be widely used in fields such as aircraft engine compressor blades that have high requirements for material erosion resistance and fatigue resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic structural diagram of a gradient nanocrystalline nitride coating structure having both erosion resistance and fatigue resistance according to the present invention;

[0035] Figure 2Schematic diagram of the variation curves of the hardness and elastic modulus of the TiN coating with the grain size, where the solid black line represents the variation curve of the hardness with the grain size, and the dashed red line represents the variation curve of the elastic modulus with the grain size;

[0036] Figure 3 Cross-sectional morphology of the TiN coating with a grain size of 91.5 nm under the action of a nanoindentation load.

[0037] The specific reference numerals are as follows: 1, metal substrate; 2, metal ion layer; 3, nitride layer. Specific embodiments

[0038] To make the advantages and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] A preparation method of a gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance specifically includes the following steps:

[0040] Step 1, prepare a metal ion layer 2 on the surface of the metal substrate 1.

[0041] Before preparing the coating, first put the metal substrate 1 into propanol and alcohol in sequence and ultrasonically clean for 10 min respectively, and quickly dry it with high-purity nitrogen.

[0042] After the treatment of the metal substrate 1, use the plasma etching technology to etch the surface of the metal substrate 1 to roughen its surface to enhance the bonding force between the metal substrate 1 and the metal ion layer 2. Then, use the high-energy ions of the metal vacuum vapor ion source (MEVVA) to bombard, and inject a large dose of Ti ions onto the roughened surface of the metal substrate 1 to form a metal ion layer 2 on the surface of the metal substrate 1. When injecting ions, the vacuum degree of the metal vacuum vapor ion source is usually 1.0×10 -4 ~1.0×10 -3 Pa, without heating, the injection voltage is 6 - 15 kV, the beam current intensity is 4 - 10 mA, the thickness of the injected ions is 60 - 200 nm, and the temperature in the furnace during injection is 30 - 40 °C. In this embodiment, when injecting Ti ions, the injection voltage is 12 kV, the beam current is 5 mA, the thickness of the injected ions is 100 nm, and the temperature in the furnace is 30 °C. In other embodiments of the present invention, the metal ion layer 2 can also be arranged on the surface of the metal substrate 1 through other existing interfacial bonding methods.

[0043] The type of the injected metal ions is determined according to the type of the nitride deposited subsequently to strengthen the bonding force with the metal substrate 1; in this embodiment, the nitride deposited subsequently is TiN, so the injected metal ions are Ti ions. The thickness of the injected ions (i.e., the thickness of the formed metal ion layer 2) is usually 60 - 200 nm, preferably 100 - 160 nm.

[0044] In this embodiment, the material of the metal substrate 1 is TC4 titanium alloy used for machining compressor blades of aero-engines. In other embodiments of the present invention, it may also be other titanium alloys, composite materials and other commonly used materials for compressor blades of aero-engines.

[0045] Step 2: Prepare a gradient cycle layer by using a process combining magnetron filtered vacuum cathodic arc deposition and in-situ annealing.

[0046] The present invention uses magnetron filtered vacuum cathodic arc deposition to deposit nitrides, that is, magnetron filtered ion plating technology. The specific steps are as follows: Nitrogen is introduced into the vacuum coating chamber to be ionized into N ions in a plasma environment. At the same time, the target metal Ti forms metal ions Ti through cathodic arc discharge. At this time, a bias voltage is applied to form TiN on the upper surface of the metal ion layer 2 by the metal ions Ti and N ions, completing the deposition of one layer of nitride (TiN). When depositing TiN, the bias voltage is set to 250V, the target current of the equipment is maintained at 110±1A, the duty cycle is maintained at 90±0.1%, and the nitrogen flow rate is controlled at 30 sccm. Among them, the nitrogen flow rate can be controlled by a programmable flow controller.

[0047] Then, in-situ annealing treatment is carried out, that is, vacuum heat preservation annealing is carried out to coarsen the grains, forming a nitride layer 3 with a grain size of nanoscale. The nitride layer 3 obtained after the first deposition of nitrides and annealing is the bottommost nitride layer 3. Since the degree of grain coarsening is related to the annealing temperature and annealing time, different annealing temperatures will result in different grain coarsening rates, and different annealing times will result in different grain coarsening degrees. That is, when the annealing time is fixed, the higher the annealing temperature, the higher the crystal coarsening rate; when the annealing temperature is fixed, the longer the annealing time, the higher the grain coarsening degree. In the present invention, the deposition temperature of the nitride is preferably 450-550°C, the deposition time is preferably 3.5-4h, the annealing temperature is preferably 400-500°C, and the annealing time is preferably 5-10h. In this embodiment, the deposition temperature of the nitride is 500°C, the deposition time is 3.5h, the annealing temperature is 500°C, and the annealing time is 10h.

[0048] After the bottommost nitride layer 3 is formed, the above-mentioned process combining magnetron filtered ion plating and in-situ annealing is used to deposit nitrides and anneal on the bottommost nitride layer 3 to form a new nitride layer 3, and then deposit nitrides and anneal on the new nitride layer 3 to form a new nitride layer 3, and so on, until the final grain size of the bottommost nitride layer 3 is coarsened to the micron scale, obtaining a gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance.

[0049] When annealing the upper nitride, the lower nitride layer 3 also participates, resulting in a larger grain size for the lower nitride layer 3. The grain sizes of the multi-layer nitride layers 3 gradually decrease in a gradient from bottom to top. That is, a gradient cyclic layer with gradually decreasing grain sizes from bottom to top is prepared on the upper surface of the metal ion layer 2. The grain boundary density of the gradient cyclic layer changes in a gradient in space, and the grain size continuously increases from the nanoscale at the top layer to the macroscopic scale of the micron scale downward.

[0050] In this embodiment, the grain size of the nitride layer 3 formed after annealing the deposited nitride once is 90 - 200 nm. Therefore, the final grain size of the topmost nitride layer 3 is in the nanoscale of 90 - 200 nm. This region has a strong ability to coordinate deformation, which can effectively improve the anti-cracking ability of the coating under high stress and enhance the anti-sand erosion performance of the coating. The final grain size of the bottommost nitride layer 3 is coarsened to the micron scale of 1 - 2 μm. This region has a high ability to resist plastic deformation and can inhibit the formation of slip steps on the substrate surface under low stress, improving the fatigue limit of the metal matrix 1. In this embodiment, all six nitride layers 3 are TiN layers. In other embodiments of the present invention, the nitride layer 3 can also be a nitride layer formed by depositing other nitrides such as ZiN, CrN, TiAlN, etc.

[0051] The total thickness of the gradient cyclic layer is usually 10 - 30 μm. In the gradient cyclic layer, each nitride layer 3 is preferably set to the same thickness. The thickness of each nitride layer 3 is determined according to the total thickness of the entire gradient cyclic layer and the degree of grain coarsening caused by each deposition and annealing. In this embodiment, the target total thickness of the gradient cyclic layer is 30 μm, that is, the target total thickness of all the stacked nitride layers 3 is 30 μm. When the final grain size of the bottommost nitride layer 3 is coarsened to the micron scale of 1 - 2 μm, a total of six nitride layers 3 are formed, and the deposition thickness of each layer is the same, which is 5 μm.

[0052] Therefore, the gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance prepared by the above preparation method, as Figure 1 shown, includes a metal ion layer 2 and a gradient cyclic layer deposited on the upper surface of the metal ion layer 2. The lower surface of the metal ion layer 2 is bonded to the upper surface of the metal matrix 1. The gradient cyclic layer includes six nitride layers 3 stacked in sequence from bottom to top on the upper surface of the metal ion layer 2. The grain sizes of the six nitride layers 3 gradually decrease in a gradient from bottom to top, and the bottommost nitride layer 3 has micron-sized grains of 90 - 200 nm, and the topmost nitride layer 3 has nanometer-sized grains of 1 - 2 μm.

[0053] The erosion resistance and fatigue resistance of the coating structure of the present invention are further illustrated by specific test data below.

[0054] Using the magnetic filtration ion plating technique, TiN coatings with grain sizes of 54.8 nm, 68.8 nm, 91.5 nm, and 136.9 nm were prepared respectively. Combining finite element calculations, the mechanical and erosion-resistant properties of TiN coatings with different grain sizes under nanoindentation loading were evaluated. As Figure 2 shown, it is a schematic diagram of the curves of the hardness and elastic modulus of the TiN coating varying with the grain size. Among them, the black solid line represents the curve of the hardness varying with the grain size, and the red dashed line represents the curve of the elastic modulus varying with the grain size. It can be seen that there is a positive correlation between the hardness and elastic modulus of the TiN coating and the grain size. Under the action of shear stress, when the grain size is less than 70 nm, the mechanical response of the TiN coating is mainly grain boundary sliding. However, when the grain size increases to more than 90 nm, under the action of nanoindentation load, the mechanical response of the TiN coating changes to the formation of intragranular shear bands and transverse cracks, as Figure 3 shown. Therefore, in the present invention, the grain size of the topmost nitride layer 3 is limited within the range of 90 - 200 nm. On the one hand, the smaller the grain size, the stronger the erosion resistance, and at the same time, it is less likely to generate fatigue cracks. On the other hand, the introduction of the gradient structure effectively inhibits the formation of slip steps at the fatigue sources inside the substrate, resulting in system fatigue failure. At the same time, the topmost nanoscale grains can improve the coordinated deformation ability between the columnar grains of the nitride coating, increase the number of cycles of fatigue crack initiation on the coating surface, and are beneficial to improving the anti-cracking ability of the coating under high stress, alleviating the damage of the nitride coating to the fatigue life of the metal matrix. At the same time, the grains of the bottommost nitride layer 3 are micron-sized, increasing the anti-plastic deformation ability of the coating near the position of the metal matrix 1, inhibiting the formation of slip steps on the surface of the metal matrix 1, and improving the fatigue limit of the metal matrix 1.

[0055] The gradient nanocrystalline nitride coating structure of the present invention has both erosion resistance and fatigue resistance, and is not only applicable to the compressor blades of aeroengines, but also can be applied to other components that serve in harsh environments and need to bear alternating loads, such as gas turbine blades, automobile engine parts, etc., which can effectively improve the performance and reliability of related equipment, reduce maintenance costs, and have significant economic and social benefits.

[0056] The above is only used to illustrate the technical solution of the present invention, rather than limiting it. For ordinary professional technicians in the field, the specific technical solution recorded in the above embodiments can be modified, or some of the technical features can be equivalently replaced. These modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution protected by the present invention.

Claims

1. A preparation method of a gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance, characterized in that, It includes the following steps: Step 1: Inject metal ions onto the surface of the roughened metal substrate (1) to form a metal ion layer (2); Step 2: Adopt the magnetron filtered vacuum cathodic arc deposition method to deposit a nitride on the upper surface of the metal ion layer (2), and then perform in-situ annealing treatment to coarsen the grains of the nitride, forming a nitride layer (3) with a nanoscale grain size; Step 3: Adopt the method of Step 2 to prepare a new nitride layer (3) on the upper surface of the currently formed nitride layer (3) until the final grain size of the bottom nitride layer (3) is coarsened to the micron scale, obtaining a gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance.

2. The preparation method of a gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance according to claim 1, wherein: In Step 2, the grain size of the nitride layer (3) is 90 - 200 nm; In Step 3, the final grain size of the bottom nitride layer (3) is 1 - 2 μm.

3. The preparation method of a gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance according to claim 1 or 2, wherein: In Step 2 and Step 3, the deposition temperature of the nitride is 450 - 550 °C, the deposition time is 3.5 - 4 h, the annealing temperature is 400 - 500 °C, and the annealing time is 5 - 10 h.

4. The preparation method of a gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance according to claim 3, wherein: In Step 2 and Step 3, the deposition temperature of the nitride is 500 °C, the deposition time is 3.5 h, the annealing temperature is 500 °C, and the annealing time is 10 h.

5. The preparation method of a gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance according to claim 1, wherein: In Step 2, when depositing the nitride on the upper surface of the metal ion layer (2) by the magnetron filtered vacuum cathodic arc deposition method, specifically: Introduce nitrogen gas into the vacuum coating chamber, and control the nitrogen gas flow through a programmable flow controller to ionize it into N ions in a plasma environment. At the same time, form metal ions by cathode arc discharge of the target metal; Apply a bias voltage to form a nitride on the upper surface of the metal ion layer (2) with the metal ions and N ions.

6. The preparation method of a gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance according to claim 5, characterized in that, Step 1 is specifically: Adopt plasma etching technology to roughen the surface of the metal substrate (1), and inject metal ions onto the roughened metal substrate (1) surface through high-energy ion bombardment of the metal vacuum vapor ion source, forming a metal ion layer (2) on the metal substrate surface.

7. The preparation method of a gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance according to claim 6, wherein: In Step 1, the vacuum degree of the metal vacuum vapor ion source is 1.0×10 -4 ~1.0×10 -3 Pa, without heating, the injection voltage is 6 - 15 kV, the beam current intensity is 4 - 10 mA, and the temperature in the furnace during injection is 30 - 40 °C; In Step 2, when depositing the nitride by the magnetron filtered vacuum cathodic arc deposition method, the bias voltage is set to 250 V, the target current of the equipment is maintained at 110 ± 1 A, the duty cycle is maintained at 90 ± 0.1%, and the flow rate of nitrogen gas introduced into the vacuum coating chamber is 30 sccm.

8. A gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance, which is prepared by using the method according to any one of claims 1 - 7.

9. A gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance according to claim 8, characterized in that: It includes a metal ion layer (2) and a gradient cyclic layer deposited on the upper surface of the metal ion layer (2); The lower surface of the metal ion layer (2) is used to contact the surface of the metal substrate (1), and its thickness is 60-200 nm; The gradient cyclic layer includes an M-layer nitride layer (3) sequentially stacked on the upper surface of the metal ion layer (2) from bottom to top, where 1 < M ≤ 10; The grain size of the M-layer nitride layer (3) gradually decreases from bottom to top, and the bottom nitride layer (3) has micron-sized grains, and the top nitride layer (3) has nano-sized grains.

10. A gradient nanocrystalline nitride coating structure with both erosion resistance and fatigue resistance according to claim 8 or 9, characterized in that: The grain size of the top nitride layer (3) is 90-200 nm, and the grain size of the bottom nitride layer (3) is 1-2 μm; The nitride layer (3) is a TiN layer, and the thicknesses of the nitride layers (3) are the same; The thickness of the metal ion layer (2) is 100-160 nm, and the total thickness of the gradient cyclic layer is 10-30 μm.

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