Preparation method of high-temperature oxidation resistant coating for surface of turbine blade of aero-engine

Abstract

The invention relates to the technical field of high-temperature protective coatings, in particular to a preparation method of a high-temperature oxidation resistant coating for the surface of a turbine blade of an aero-engine, which is realized by cleaning an N5 alloy blade, depositing an oxygen-doped coating by multi-arc ion plating and performing vacuum annealing treatment. The thermal expansion coefficient difference between the coating and an oxidation film is reduced through oxygen doping, stress accumulation is reduced, meanwhile, an N5 alloy target homogenized with a matrix is adopted, element mutual diffusion is avoided, and the stability of a gamma / gamma'double-phase structure is maintained. The preferred process parameters comprise the flow ratio of Ar to O2, the deposition temperature and the annealing condition. The prepared coating is excellent in oxidation resistance at the temperature of 1000 DEG C, the weight increment is only 0.5 mg / cm, the peeling and cracking phenomena do not exist in circulating oxidation, the problem that a traditional coating is prone to failure is solved, and the method is suitable for large-scale industrial application.

Description

Technical Field

[0001] The present invention belongs to the technical field of protection of hot end components of aircraft engines, and in particular relates to a method for preparing a high-temperature oxidation resistant coating for the surface of an aircraft engine turbine blade. Background Art

[0002] High-temperature protective coatings provide effective protection against oxidative corrosion for components in high-temperature service and are widely used in aerospace, shipbuilding, energy, petrochemical, and other fields. For example, aircraft engine turbine blades are commonly coated with high-temperature protective coatings to improve performance, reliability, and service life. By utilizing a high-Al composition, high-temperature protective coatings generate a dense, thermodynamically stable, and slow-growing Al2O3 film on the surface, thereby reducing the corrosion rate of hot-end components.

[0003] The key to the oxidation resistance of high-temperature protective coatings lies in the ability to form a complete oxide film (typically composed of Cr2O3 and Al2O3, and typically α-Al2O3 at temperatures above 1000°C) on the coating surface to resist attack by external corrosive media. In a sense, the composition and structure of the coating determine the performance of the oxide film. As service temperatures and service life continue to rise, bondline failures fall into two main categories: one is thermomechanical failure caused by the external environment. For example, during thermal cycling, the mismatch in the thermal expansion coefficient between the oxide film and the coating leads to cracking and flaking of the oxide film, resulting in a loss of its ability to resist external corrosion. The other is failure caused by the loss of beneficial elements such as Al and Cr within the coating. The primary issue is interdiffusion caused by the compositional differences between the coating and the substrate. This process destroys the alloy's γ / γ' dual-phase structure, degrading the mechanical properties of the high-temperature alloy and shortening the service life of the alloy components, becoming a significant factor limiting the use of high-temperature protective coatings.

[0004] Existing coatings prepared using multi-arc ion plating can improve their antioxidant properties. However, due to compositional differences, some interdiffusion still occurs between the coating and the substrate, affecting the coating's long-term stability. Furthermore, the difference in thermal expansion coefficient between the coating and the oxide film can lead to internal stress accumulation, further degrading coating performance. Therefore, optimizing the coating's composition and preparation process to reduce the difference in thermal expansion coefficient between the coating and the oxide film, while also minimizing interdiffusion between the coating and the substrate, has become a pressing technical challenge. Summary of the Invention

[0005] In response to the problems in the prior art of significant thermal expansion coefficient difference between the high-temperature protective coating and the substrate, which leads to stress accumulation in the oxide film and causes spalling failure, as well as the shortcomings of element interdiffusion caused by the difference in composition between the coating and the substrate, which destroys the alloy's γ / γ' dual-phase structure and reduces mechanical properties, the present invention provides a method for preparing a high-temperature oxidation-resistant coating for the surface of aircraft engine turbine blades.

[0006] This method deposits an oxygen-doped coating on the surface of the N5 alloy, uses oxygen doping to regulate the coating composition, reduces the difference in thermal expansion coefficient between the coating and the oxide film (α-Al2O3), and combines the homogenization design of the target material and the substrate to avoid the occurrence of elemental interdiffusion, thereby improving the coating's oxidation resistance and long-term stability.

[0007] The technical solution of the present invention is: A method for preparing a high-temperature oxidation resistant coating on the surface of an aero-engine turbine blade comprises the following steps: 1) Clean the N5 alloy blades to remove dust, oil, and water stains from the surface, and then dry them to obtain clean prefabricated N5 blades; 2) placing the prefabricated N5 blade obtained in step 1) together with the N5 alloy target in a reaction chamber of a multi-arc ion plating apparatus, introducing a mixed gas of argon and oxygen, and performing a deposition operation under set process parameters to form an oxygen-doped coating; 3) Place the sample deposited in step 2) in a vacuum annealing furnace for annealing. During the annealing process, the vacuum degree is controlled to be less than 6×10⁻³-8×10⁻³Pa, the heating rate is 8℃ / min-10℃ / min, the holding temperature is 1000-1050℃, the holding time is 4-6 hours, and then the sample is cooled to room temperature in the furnace.

[0008] In the aforementioned steps, a mixed gas of Ar and O2 is introduced during the multi-arc ion plating process to achieve uniform distribution of oxygen in the coating, reducing the difference in thermal expansion coefficient between the coating and the oxide film, and thus reducing stress accumulation within the oxide film. Furthermore, the use of the same N5 alloy as the substrate as the target ensures consistent composition between the coating and the substrate, eliminating the possibility of interdiffusion and maintaining the stability of the γ / γ' dual-phase structure.

[0009] Preferably, in the above-mentioned method for preparing the high-temperature oxidation resistant coating, in step 2), the flow ratio of the argon and oxygen mixed gases is 20:1-10:1, wherein the flow range of the argon is 100-200 sccm, and the flow range of the oxygen is 10-20 sccm.

[0010] By adjusting the flow rate of O2, the oxygen content in the coating can be further optimized, thereby regulating the thermal expansion coefficient and antioxidant properties of the coating.

[0011] Preferably, in the above-mentioned method for preparing the high-temperature oxidation resistant coating, the process parameters of the deposition process in step 2) are set as deposition temperature of 50-200° C., negative bias voltage of 50-70 V, current of 90-100 A, and deposition time of 4-6 hours.

[0012] The selection of the above parameters ensures the density and continuity of the coating. The porosity of the oxygen-doped coating is controlled below 0.5%, effectively blocking the intrusion of external corrosive media.

[0013] Preferably, in the preparation method of the above-mentioned high-temperature oxidation-resistant coating, the specific operating steps of vacuum annealing in step 3) include: first placing the sample at the mouth of a quartz tube, sending it to the heating center of a tube furnace, closing the mouth of the tube and tightening the air valve; then starting the cooling water system, mechanical pump and diffusion pump, first using the mechanical pump to evacuate the vacuum in the tube to below 10⁻¹ Pa, and then using the diffusion pump to evacuate the vacuum to below 6×10⁻³ Pa; then raising the temperature to 1000-1050°C at a heating rate of 8-10°C / min, and keeping it at this temperature for 4-6 hours; after the insulation is completed, the diffusion pump is turned off when the sample cools to below 200°C with the furnace, and the mechanical pump is turned off after the diffusion pump cools to room temperature, and finally the air is released and the mouth of the tube is opened to remove the sample.

[0014] This annealing process not only removes any residual stress from the deposition process but also further improves the coating's density and adhesion. By controlling the annealing temperature and time, the interfacial bonding strength between the coating and the substrate is ensured, while also preventing degradation of the coating's performance due to excessively high temperatures or prolonged annealing times.

[0015] Preferably, in the above-mentioned method for preparing the high-temperature oxidation resistant coating, the thickness of the oxygen-doped coating formed in step 2) is 20-30 μm. Preferably, in the above-mentioned method for preparing the high-temperature oxidation resistant coating, the cleaning treatment in step 1) comprises ultrasonic cleaning with deionized water and anhydrous ethanol for 10-15 minutes respectively, and then drying with nitrogen.

[0016] Preferably, in the above-mentioned method for preparing the high-temperature oxidation resistant coating, in step 2), a N5 alloy target and a rotating bracket are provided in the reaction chamber of the multi-arc ion plating equipment, and the rotating bracket is driven by a motor to achieve uniform rotation.

[0017] Preferably, in the above-mentioned method for preparing the high-temperature oxidation resistant coating, in step 2), the distance between the N5 alloy target and the prefabricated N5 blade is 15-20 cm to ensure that the coating evenly covers the blade surface during the deposition process.

[0018] The present invention utilizes multi-arc ion plating technology combined with oxygen doping, offering significant advantages in simplicity and cost control over traditional electroplating of Pt layers and diffusion annealing. Traditional electroplating of Pt layers requires multiple steps, including substrate pretreatment, electroplating, and post-treatment (such as diffusion annealing). Diffusion annealing requires high temperatures (typically >800°C) and prolonged treatment to promote element diffusion, which can easily lead to substrate deformation and increased energy consumption. Multi-arc ion plating, on the other hand, directly deposits thin films using a high-energy ion beam in a vacuum environment, and oxygen doping can be achieved simultaneously through plasma treatment. Electroplating of Pt relies on the precious metal platinum, resulting in high material costs and complex wastewater treatment. Multi-arc ion plating, on the other hand, utilizes common metal targets (such as Ti and AlTi alloys) and produces high-performance compound films (such as TiN and AlTiN) through gas doping (such as N₂ and O₂), resulting in high material utilization and environmental friendliness. Furthermore, electromagnetic field-enhanced multi-arc ion plating achieves a deposition rate of up to 2.8 μm / h, far exceeding traditional processes and further reducing energy consumption per unit time. Furthermore, traditional Pt layers rely on thickness to improve performance, but are prone to insufficient bonding and uniformity issues. Multi-arc ion plating combined with oxygen doping can achieve film densification and composition gradient design by manipulating plasma parameters (such as bias voltage and gas ratio). For example, oxygen doping in AlTiN coatings promotes the formation of the Al2O3 phase, improving high-temperature oxidation resistance (oxidation increment is only 1.01 mg / cm² at 1100°C). Simultaneously, the film-to-substrate bonding strength reaches over 36N, resulting in overall performance superior to single metal coatings. Currently, multi-arc ion plating equipment (such as the PIS series) has achieved fully automated control, supporting rapid process recipe switching and real-time monitoring, making it suitable for large-scale production scenarios such as cutting tools and aeroengine blades. Traditional electroplating and annealing processes, on the other hand, are highly equipment-dependent and struggle to achieve uniform coating on complex workpieces.

[0019] Advantages and beneficial effects of the present invention: 1. The present invention introduces oxygen doping during the multi-arc ion plating process. The uniform distribution of oxygen in the coating significantly reduces the difference in thermal expansion coefficient between the coating and the oxide film (α-Al2O3), thereby reducing stress accumulation within the oxide film and improving spalling resistance. Furthermore, oxygen doping inhibits the growth rate of the coating's grains in high-temperature environments, slowing the degradation of the metal-ceramic coating and further enhancing the coating's oxidation resistance.

[0020] 2. This invention uses the same N5 alloy as the substrate as the target material, primarily to address the interdiffusion issues associated with conventional coatings due to compositional differences. By homogenizing the target and substrate, this eliminates these compositional differences, preventing the loss of beneficial elements such as Al and Cr, maintaining the stability of the γ / γ' dual-phase structure, and addressing the mechanical property degradation associated with interdiffusion in conventional coatings.

[0021] 3. The method of the present invention has the characteristics of simple process, strong operability and low production cost, and is suitable for large-scale industrial application.

[0022] 4. The examples show that the high-temperature oxidation-resistant coating prepared by the present invention exhibits excellent antioxidant properties at 1000°C. Specifically, in the constant-temperature intermittent oxidation experiment, the weight gain of the sample after oxidation at 1000°C for 20 hours is only 0.5 mg / cm²; in the cyclic oxidation experiment, the sample exhibits stable antioxidant properties under hot and cold cycling conditions, without obvious peeling or cracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the structure of the multi-arc ion plating equipment, which shows the arrangement of the reaction chamber, target material and substrate; Figure 2 This is a cross-sectional microstructure of the deposited high-temperature oxidation resistant coating, showing good interface bonding between the coating and the N5 alloy substrate; Figure 3 (a) The oxidation kinetic curves of the three composite coatings at 1000°C and the parabolic rate constant K p (b), C1 is the N5 coating without oxygen doping of comparative example 5, C2 is the coating with 10 sccm of oxygen introduced into example 1, and C3 is the coating with 20 sccm of oxygen introduced into example 2. DETAILED DESCRIPTION

[0024] The following examples are further detailed descriptions of the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Example 1

[0025] In this embodiment, an N5 blade and an N5 alloy target were placed together in the reaction chamber of a multi-arc ion plating apparatus. The distance between the N5 alloy target and the prefabricated N5 blade was 15 cm. A mixed gas of argon and oxygen was introduced, and a deposition operation was performed under set process parameters to form an oxygen-doped coating. The specific preparation parameters are as follows: 1) Clean the N5 alloy blades to remove dust, oil, and water stains from the surface, and then dry them to obtain clean prefabricated N5 blades; 2) Placing the prefabricated N5 blade obtained in step 1) together with the N5 alloy target in a reaction chamber of a multi-arc ion plating apparatus, introducing a mixture of argon and oxygen at a flow rate of 150 sccm and a flow rate of 10 sccm, with the following process parameters: deposition temperature of 150° C., negative bias voltage of 70 V, current of 92 A, and deposition time of 6 hours, to form an oxygen-doped coating; 3) The sample deposited in step 2) was placed in a vacuum annealing furnace for annealing. During the annealing process, the vacuum degree was controlled to be less than 6×10⁻³, the heating rate was 10°C / min, the holding temperature was 1000°C, the holding time was 6 hours, and then the sample was cooled to room temperature in the furnace. Step 4) Conduct a constant temperature intermittent oxidation experiment at a test temperature of 1000°C, and take out samples at regular intervals to measure the mass change; Step 5) Perform a cyclic oxidation experiment at a test temperature of 1000°C. Set the cycle time to 1 hour in the furnace and 10 minutes of air cooling outside the furnace. Weigh the sample after a certain number of cycles and record the mass change.

[0026] The coating prepared in this example has a uniform and dense surface and is well bonded to the N5 alloy substrate; its hardness is 455HV; and after oxidation at 1000°C for 500 hours, the oxidation weight gain is 1.06 mg / cm 2 . Example 2

[0027] In this embodiment, an N5 blade and an N5 alloy target were placed together in the reaction chamber of a multi-arc ion plating apparatus. The distance between the N5 alloy target and the prefabricated N5 blade was 20 cm. A mixed gas of argon and oxygen was introduced, and a deposition operation was performed under set process parameters to form an oxygen-doped coating. The specific preparation parameters are as follows: 1) Clean the N5 alloy blades to remove dust, oil, and water stains from the surface, and then dry them to obtain clean prefabricated N5 blades; 2) Placing the prefabricated N5 blade obtained in step 1) together with the N5 alloy target in a reaction chamber of a multi-arc ion plating apparatus, introducing a mixture of argon and oxygen at a flow rate of 150 sccm and a flow rate of 20 sccm, with the following process parameters: deposition temperature of 150° C., negative bias voltage of 70 V, current of 92 A, and deposition time of 6 hours, to form an oxygen-doped coating; 3) The sample deposited in step 2) was placed in a vacuum annealing furnace for annealing. During the annealing process, the vacuum degree was controlled to be less than 8×10⁻³, the heating rate was 8°C / min, the holding temperature was 1050°C, the holding time was 4 hours, and then the sample was cooled to room temperature in the furnace. Step 4) Conduct a constant temperature intermittent oxidation experiment at a test temperature of 1000°C, and take out samples at regular intervals to measure the mass change; Step 5) Carry out cyclic oxidation experiment, the test temperature is 1000℃, the cycle time is set to 1h in the furnace and 10min in air cooling outside the furnace, weigh the sample after a certain number of cycles, and record the mass change The coating surface is uniform and dense, and it bonds well with the N5 alloy substrate; the hardness is 455HV; after oxidation at 1000℃ for 500 hours, the oxidation weight gain is 0.85 mg / cm 2 . Comparative Example 1

[0028] The difference from Example 1 is that: Argon flow rate: 156 sccm; Oxygen flow rate: 12 sccm; Negative bias voltage: 72V; Current: 99A; Heating rate of vacuum annealing: 8℃ / min; The coating surface is uniform and dense, and it bonds well with the N5 alloy substrate; the hardness is 325HV; after oxidation at 1000℃ for 500 hours, the oxidation weight gain is 1.10 mg / cm 2 . Comparative Example 2

[0029] The difference from Example 1 is that: Argon flow rate: 160 sccm; Oxygen flow rate: 14 sccm; Negative bias voltage: 78V; Current: 97A; Heating rate of vacuum annealing: 9°C / min; The coating surface is uniform and dense, and has good bonding with the N5 alloy substrate; the hardness is 404HV; after oxidation at 1000℃ for 500 hours, the oxidation weight gain is 1.12mg / cm 2 . Comparative Example 3

[0030] The difference from Example 2 is that: Argon flow rate: 156 sccm; Oxygen flow rate: 22 sccm; Negative bias voltage: 72V; Current: 95A; Heating rate of vacuum annealing: 8℃ / min; The coating surface is uniform and dense, and it bonds well with the N5 alloy substrate; the hardness is 435HV; after oxidation at 1000℃ for 500 hours, the oxidation weight gain is 0.90 mg / cm 2 . Comparative Example 4

[0031] The difference from Example 2 is that: Argon flow rate: 160 sccm; Oxygen flow rate: 24 sccm; Negative bias voltage: 78V; Current: 100A; Heating rate of vacuum annealing: 9°C / min; The coating prepared in this example has a uniform and dense surface and is well bonded to the N5 alloy substrate; its hardness is 423HV; and after oxidation at 1000°C for 500 hours, the oxidation weight gain is 0.87mg / cm 2 . Comparative Example 5

[0032] The difference from Example 2 is that: Argon flow rate: 156 sccm; Oxygen flow rate: 0 sccm; Negative bias voltage: 72V; Current: 99A; Heating rate of vacuum annealing: 10℃ / min; The coating surface is uniform and dense, and it bonds well with the N5 alloy substrate. The hardness is 267HV. After oxidation at 1000℃ for 500 hours, the oxidation weight gain is 1.29 mg / cm 2 .

[0033] The results of the embodiments and comparative examples show that the composite coating prepared by the multi-arc ion plating method on the N5 alloy blade of the present invention is well bonded to the N5 alloy substrate, and the nano-scale Al2O3 particles generated inside the coating during the oxidation process reduce the difference in thermal expansion coefficient between the coating and the oxide film, thereby reducing the thermal stress inside the coating during the cyclic oxidation process.

[0034] Figure 3 The kinetic curves of the composite coatings after oxidation at 1000°C for 500 hours are shown in Figure 1. C1 represents the coating without oxygen doping during deposition, C2 represents the coating with 10 sccm of oxygen introduced during deposition, and C3 represents the coating with 20 sccm of oxygen introduced during deposition. The oxidation rates of the three coatings all follow a parabolic law, with the parabolic rate constant of C1 being 5.61×10 - 13 g 2 cm -4 s -1 , C2 coating is 5.95×10 -13 g 2 cm -4 s -1 , C3 coating is 3.98×10 -13 g 2 cm -4 s -1After 350 hours of oxidation, the oxidation rate of the C1 coating increased and deviated from the parabolic law. In comparison, the oxidation rates of the C2 and C3 coatings remained unchanged during the 500-hour oxidation process. Therefore, using multi-arc ion plating technology to introduce an Ar+O2 mixed atmosphere during the deposition process on the N5 alloy surface to prepare an oxygen-doped coating can reduce the mismatch in thermal expansion coefficients between the coating and the oxide film, thereby reducing the stress generated in the oxide film and improving the coating's resistance to high-temperature oxidation. At the same time, the coating structure is dense and continuous, with the same composition as the base alloy, and no interdiffusion occurs, which provides excellent high-temperature oxidation resistance. This solves the problems of existing methods for preparing aircraft blade surface coatings, such as easy interdiffusion with the base, poor performance, and easy fatigue shedding.

[0035] The application potential of the multi-arc ion plating technology combined with the oxygen doping process in high-temperature components is not limited to aircraft engine blades. Its excellent high-temperature resistance, wear resistance and corrosion resistance can be extended to a variety of high-temperature key components.

[0036] For example, it can be applied to turbine disks and blade rings, core components of aircraft engines subject to high temperatures and pressures, with operating temperatures exceeding 1000°C. Multi-arc ion plating technology deposits composite coatings such as TiAlN and CrTiAlN, significantly improving their resistance to high-temperature oxidation. For example, a GrTiAlN coating showed no signs of corrosion after 200 hours in a 900°C salt spray test. Its dense structure effectively blocks the penetration of oxidizing media. Furthermore, the coating's high hardness (30-35 GPa) reduces fretting wear at high temperatures, extending component life.

[0037] For example, it can be applied to combustion chamber liners and nozzle guide vanes, which are exposed to high-temperature combustion gases and corrosive gases for a long time. The Cr2AlC-based coating produced by multi-arc ion plating has excellent high-temperature oxidation resistance, with an oxidation weight gain of only 1.01 mg / cm² at 1000°C. Subsequent annealing can eliminate the columnar crystal structure and prevent the coating from degrading along the grain boundaries. The thermal expansion coefficient of this type of coating (13.3×10⁻ 6 / ℃) matches the high-temperature alloy substrate to reduce the risk of thermal stress cracking.

[0038] For example, it can be applied to aircraft engine bearings and transmission components, where high-speed bearings and gear transmission components require both wear resistance and fatigue resistance. Multi-arc ion plating technology can deposit TiN or TiAlN coatings on titanium alloy or steel substrates, achieving hardness exceeding 2500 HV and reducing the coefficient of friction by 30%-50%. For example, titanium alloy bearings coated with TiN can more than double their fatigue life, making them suitable for high-temperature and high-load conditions. Oxygen doping can also optimize the film's gradient structure, enhancing bonding strength (to over 36N).

[0039] For example, it can be applied to industrial gas turbines and energy equipment. Components such as gas turbine blades and combustion chamber inner walls are subject to high-temperature corrosion and erosion. Multi-arc ion plating technology can achieve multi-layer protection through gradient composite coatings (such as TiN / TiAlN): an outer TiAlN layer provides oxidation resistance, a middle TiN layer enhances hardness, and a bottom CrN layer improves adhesion. This type of coating exhibits oxidation weight gain of only one-third that of traditional coatings in a 900°C oxidizing environment, making it suitable for power plant turbine blades and the inner walls of petrochemical reactors.

[0040] For example, it can be applied to automotive turbochargers and exhaust systems. Turbocharger rotors are prone to creep failure in high-temperature exhaust gases. Multi-arc ion-plated AlTiN-O coatings (oxygen-doped AlTiN) significantly enhance oxidation resistance (stable at 1100°C) by regulating oxygen content to form an Al2O3 phase, while reducing coating brittleness, making them suitable for turbocharger blades.

Claims

1. A method for preparing a high temperature oxidation resistant coating on the surface of an aircraft engine turbine blade, characterized in that: The specific steps include: 1) Clean the N5 alloy blades to remove dust, oil, and water stains from the surface, and then dry them to obtain clean prefabricated N5 blades; 2) placing the prefabricated N5 blade obtained in step 1) together with the N5 alloy target in a reaction chamber of a multi-arc ion plating apparatus, introducing a mixed gas of argon and oxygen, and performing a deposition operation under set process parameters to form an oxygen-doped coating; 3) Place the sample deposited in step 2) in a vacuum annealing furnace for annealing. During the annealing process, the vacuum degree is controlled to be less than 6×10⁻³-8×10⁻³Pa, the heating rate is 8℃ / min-10℃ / min, the holding temperature is 1000-1050℃, the holding time is 4-6 hours, and then the sample is cooled to room temperature in the furnace.

2. The method for preparing a high temperature oxidation resistant coating according to claim 1, characterized in that: In step 2), the flow ratio of the argon gas to the oxygen gas mixture is 20:1-10:1, wherein the flow range of the argon gas is 100-200 sccm, and the flow range of the oxygen gas is 10-20 sccm.

3. The method for preparing a high temperature oxidation resistant coating according to claim 1 or 2, characterized in that: The process parameters of the deposition process in step 2) are set as a deposition temperature of 50-200° C., a negative bias voltage of 50-70 V, a current of 90-100 A, and a deposition time of 4-6 hours.

4. The method for preparing a high temperature oxidation resistant coating according to claim 1, characterized in that: The specific operating steps of vacuum annealing in step 3) include: first, place the sample at the mouth of a quartz tube, send it to the heating center of the tube furnace, close the mouth of the tube and tighten the air valve; then start the cooling water system, mechanical pump and diffusion pump, first use the mechanical pump to evacuate the vacuum in the tube to below 10⁻¹ Pa, and then use the diffusion pump to evacuate the vacuum to below 6×10⁻³ Pa; then, raise the temperature to 1000-1050℃ at a heating rate of 8-10℃ / min and keep it at this temperature for 4-6 hours; after the insulation is completed, turn off the diffusion pump when the sample cools to below 200℃ with the furnace, and then turn off the mechanical pump after the diffusion pump cools to room temperature. Finally, release the air and open the mouth of the tube to remove the sample.

5. The method for preparing a high temperature oxidation resistant coating according to claim 1, characterized in that: The thickness of the oxygen-doped coating formed in step 2) is 20-30 μm.

6. The method for preparing a high temperature oxidation resistant coating according to claim 1, characterized in that: The porosity of the oxygen-doped coating formed in step 2) is controlled to be below 0.5%.

7. The method for preparing a high temperature oxidation resistant coating according to claim 1, characterized in that: The cleaning treatment in step 1) includes ultrasonic cleaning with deionized water and anhydrous ethanol for 10-15 minutes respectively, and then drying with nitrogen.

8. The method for preparing a high temperature oxidation resistant coating according to claim 1, characterized in that: In step 2), a N5 alloy target and a rotating bracket are arranged in the reaction chamber of the multi-arc ion plating equipment, and the rotating bracket is driven by a motor to achieve uniform rotation.

9. The method for preparing a high temperature oxidation resistant coating according to claim 1, characterized in that: In step 2), the distance between the N5 alloy target and the prefabricated N5 blade is 15-20 cm to ensure that the coating is evenly covered on the blade surface during the deposition process.

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