Method for cold spraying of hard repair coating on 7xxx-series ultrahigh-strength aluminum alloy

Abstract

The invention discloses a method for cold spraying of a hard repair coating on a 7xxx-series ultrahigh-strength aluminum alloy, and relates to a method for cold spraying of a repair coating. In order to improve the performance of a cold spraying repair coating of a high-strength aluminum alloy structural part, the invention provides a method for cold spraying of a hard repair coating of a 7xxx-series ultrahigh-strength aluminum alloy, the cold spraying coating deposition is assisted by utilizing the advantage of plasma rapid heating, online heat treatment is carried out on a matrix and the coating before, during and after particle deposition, and the cold spraying repair coating of the 7xxx-series ultrahigh-strength aluminum alloy is obtained. Deposited particles, a substrate and the surface of the coating are softened under the action of plasma arc light, so that particle deposition can reach critical heat and force conditions more easily, the metallurgical bonding proportion is increased, the bonding force and compactness of the coating are improved, online heat treatment is beneficial to regulation and control of the substrate and the coating structure, and the performance of the coating is improved.

Description

Technical Field

[0001] The invention relates to a method for cold spraying repair coating. Background Art

[0002] As an ultra-high-strength aluminum alloy, 7xxx series aluminum alloy is widely used in aerospace, automobile manufacturing and other fields, and has developed into the main structural material of military and civilian aircraft in various countries in the world. However, 7xxx series aluminum alloy products often serve in high-strength, high-stress, complex corrosion and other environments, and inevitably have a series of damages, such as superficial cracks, corrosion pits, wear, etc., which directly affect the safety and reliability of the product. Therefore, timely and effective repair of the surface of 7xxx aluminum alloy can not only restore and enhance its corrosion resistance, fatigue resistance and other properties, but also significantly extend the service life of the material. However, components such as aircraft wings and landing gear are not easy to disassemble and transport, so a reliable online repair technology is needed.

[0003] Cold spray technology is a powder particle cumulative forming method based on gas-solid two-phase fluid dynamics and high-speed collision dynamics. In the Laval nozzle, the particles collide with the substrate surface at a certain speed and temperature under the set gas temperature and pressure. When the particle speed exceeds a specific critical deposition speed, it will produce synergistic plastic deformation and combine with the substrate, thereby achieving particle deposition. Compared with repair technologies such as stir friction welding and laser cladding, cold spray repair has the advantages of low process temperature, fast deposition speed, and flexible repair structure, and is more suitable for online repair of parts.

[0004] However, based on the basic principle of severe plastic deformation and deposition of cold spray particles, the performance of cold spray deposits is not perfect, mainly manifested in: the plasticity of the sprayed deposits is extremely low; for some important structural materials, the density of the coating needs to be further improved; the particle interface inside the cold spray deposit is difficult to achieve metallurgical bonding, and the coating bonding strength needs to be improved. These factors make it difficult for the current high-strength aluminum alloy cold spray repair coating to meet the performance requirements of structural parts. In response to the above problems, domestic and foreign scholars have found that heat treatment after cold spraying can help significantly improve coating performance, but this method is difficult to apply to online repair of parts. Summary of the invention

[0005] In order to improve the performance of cold spray repair coatings for high-strength aluminum alloy structural parts, the present invention proposes a method for cold spraying hard repair coatings for 7xxx series ultra-high-strength aluminum alloys. The advantages of rapid plasma heating are utilized to assist cold spray coating deposition. The substrate and coating are subjected to online heat treatment before, during and after particle deposition, thereby improving coating performance.

[0006] The method for cold spraying hard repair coating of 7xxx series ultra-high strength aluminum alloy of the present invention is carried out according to the following steps:

[0007] Step 1: First, grind the surface of the aluminum alloy to be repaired to remove the defective parts; then, sandblast and ultrasonically clean the surface to be repaired with anhydrous ethanol to remove the aluminum oxide film and stains on the surface to be repaired, thereby facilitating cold spray repair deposition;

[0008] Step 2: Fill the aluminum alloy powder into the powder feeder of the cold spraying equipment; adjust the cold spraying device so that the cold spraying gun muzzle is perpendicular to the surface to be repaired, and adjust the plasma device so that the generated plasma arc acts on the surface to be repaired;

[0009] Step three, turn on the gas control system of the cold spray device to provide a nitrogen atmosphere, which helps to control the temperature of the area to be subsequently heat treated with plasma arc and prevent oxidation. Turn on the plasma device before cold spray particle deposition, and use plasma arc to heat treat the surface to be repaired for 30-60s; using plasma arc to heat treat the surface to be repaired before cold spray particle deposition can quickly heat up and soften the surface of the area to be repaired, making it easier for subsequent particle deposition to reach the critical thermal and mechanical conditions, thereby improving the bonding between the coating and the substrate. Then turn on the cold spray powder delivery system to deposit cold spray particles, and use plasma arc to heat treat the repaired surface while cold spraying particles; using plasma arc to heat treat the repaired surface while cold spraying can regulate the structure and properties of the coating, and soften the coating surface and deposited particles, thereby improving the density and performance of the coating. After the cold spray particle deposition is completed, the cold spray powder feeding is stopped, and the obtained coating is heat treated with plasma arc for 30-60s, and then the cold spray gun chamber temperature drops below 200°C, and the cold spray gas feeding system and plasma device are turned off. After the cold spray particle deposition is completed, the obtained coating is heat treated with plasma arc, which can promote the diffusion of the interface between particles in the coating, thereby increasing the metallurgical bonding ratio and improving the coating performance.

[0010] The principles and beneficial effects of the present invention are as follows:

[0011] 1. Due to the high hardness of 7xxx series aluminum alloy products and powder particles, the thermal and mechanical conditions required for powder deformation deposition are higher, resulting in the problems of weak interface bonding, large voids in the coating, and low density in the 7xxx series aluminum alloy coating deposited by single cold spraying.

[0012] The present invention uses the effect of plasma arc to soften the deposited particles, substrate and coating surface, which can quickly increase the substrate surface and powder temperature, thermally soften the substrate and coating surface, and make it easier for particle deposition to reach critical thermal and mechanical conditions. When high-speed metal particles collide with the substrate or the deposited coating, the metal particles undergo a large deformation and reach the critical thermal and mechanical conditions before adhering to the substrate and depositing. After the particle collision ends, due to the elastic deformation recovery, the extrusion effect between the deformed particles and the substrate (or deposited particles) causes local mechanical bite and metallurgical bonding (metal bonds). And thermal assistance can promote the formation of metal bonds between the deformed particles and the substrate (or deposited particles), increase the proportion of metallurgical bonding, and thus improve the coating bonding strength, density and overall performance.

[0013] 2. When cold spraying particles are deposited, most of the kinetic energy of the powder particles will be converted into heat energy at the moment of impact. However, due to the extremely short time, this heat energy cannot be transferred out in time, resulting in an adiabatic softening effect in the impact area. Due to the severe plastic deformation caused by particle impact and the heat generated in the process, it is difficult for the coating to reach the recovery or recrystallization temperature, so the coating is in a state of work hardening, which is manifested as increased coating hardness and extremely low plasticity. In addition, as an ultra-high-strength aluminum alloy, 7xxx series aluminum alloys are often in a work-hardening state in actual applications due to performance requirements, and the surface hardness is high, making the deposition of homogeneous ultra-high-strength aluminum alloy powder more difficult.

[0014] The online heat treatment of the present invention helps to quickly increase the surface temperature of the substrate and the coating, and the adiabatic softening effect of the cold spray particle deposition makes the deposition area short-term in the recovery or recrystallization temperature when subjected to severe plastic deformation, thereby promoting the bonding of the coating substrate and the coating while increasing the recovery and recrystallization ratio, so that the repaired area has high strength and plasticity that exceeds that of a single cold spray; therefore, online heat treatment helps to regulate the substrate and coating structure, thereby improving coating performance.

[0015] 3. The cold spraying of the present invention adopts a high-pressure nitrogen atmosphere, which helps to control the regional temperature of the online heat treatment and prevent oxidation. At the same time, since the plasma device and the cold spraying are separated, the action stage and position of the online heat treatment are more flexible, making it suitable for online repair of auxiliary cold spraying. On this basis, the reinforcing phase particles in the form of droplets can also be introduced through plasma spraying to further improve the coating density and mechanical properties by reinforcing the strengthening mechanism of the phase itself and its filling of the gaps. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a physical picture of the repair coating obtained in Example 1;

[0017] Figure 2 The temperature variation curves of the repair coating obtained in Example 1 and the coating obtained by single cold spraying in the comparative example;

[0018] Figure 3 The scanning electron microscope images of the cross section of the repair coating obtained in Example 1 and the coating obtained by single cold spraying in the comparative example;

[0019] Figure 4 This is a comparison chart of the Vickers hardness of the repair coating obtained in Example 1 and the coating obtained by single cold spraying in the comparative example. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any reasonable combination of the specific implementation modes.

[0021] Specific implementation method 1: In this implementation method, the method for cold spraying hard repair coating of 7xxx series ultra-high strength aluminum alloy is carried out according to the following steps:

[0022] Step 1: First, grind the surface of the aluminum alloy to be repaired to remove the defective parts; then, sandblast and ultrasonically clean the surface to be repaired with anhydrous ethanol to remove the aluminum oxide film and stains on the surface to be repaired, thereby facilitating cold spray repair deposition;

[0023] Step 2: Fill the aluminum alloy powder into the powder feeder of the cold spraying equipment; adjust the cold spraying device so that the cold spraying gun muzzle is perpendicular to the surface to be repaired, and adjust the plasma device so that the generated plasma arc acts on the surface to be repaired;

[0024] Step 3, start the gas control system of the cold spray device, start the plasma device before cold spray particle deposition, and use plasma arc to heat treat the surface to be repaired for 30-60s; then start the cold spray powder delivery system to deposit cold spray particles, and use plasma arc to heat treat the repair surface while cold spray particle deposition; after the cold spray particle deposition is completed, stop the cold spray powder delivery, and use plasma arc to heat treat the obtained coating for 30-60s, and then wait until the temperature of the cold spray gun chamber drops below 200°C, and then turn off the cold spray gas delivery system and plasma device.

[0025] 1. Due to the high hardness of 7xxx series aluminum alloy products and powder particles, the thermal and mechanical conditions required for powder deformation deposition are higher, resulting in the problems of weak interface bonding, large voids in the coating, and low density in the 7xxx series aluminum alloy coating deposited by single cold spraying.

[0026] The present embodiment utilizes the effect of plasma arc to soften the deposited particles, substrate and coating surface, which can quickly increase the substrate surface and powder temperature, thermally soften the substrate and coating surface, and make it easier for particle deposition to reach critical thermal and mechanical conditions. When high-speed metal particles collide with the substrate or the deposited coating, the metal particles undergo a large deformation and reach the critical thermal and mechanical conditions before adhering to the substrate and depositing. After the particle collision ends, due to the elastic deformation recovery, the extrusion effect between the deformed particles and the substrate (or deposited particles) causes local mechanical bite and metallurgical bonding (metal bonds). Moreover, thermal assistance can promote the formation of metal bonds between the deformed particles and the substrate (or deposited particles), increase the proportion of metallurgical bonding, and thus improve the coating bonding strength, density and overall performance.

[0027] 2. When cold spraying particles are deposited, most of the kinetic energy of the powder particles will be converted into heat energy at the moment of impact. However, due to the extremely short time, this heat energy cannot be transferred out in time, resulting in an adiabatic softening effect in the impact area. Due to the severe plastic deformation caused by particle impact and the heat generated in the process, it is difficult for the coating to reach the recovery or recrystallization temperature, so the coating is in a state of work hardening, which is manifested as increased coating hardness and extremely low plasticity. In addition, as an ultra-high-strength aluminum alloy, 7xxx series aluminum alloys are often in a work-hardening state in actual applications due to performance requirements, and the surface hardness is high, making the deposition of homogeneous ultra-high-strength aluminum alloy powder more difficult.

[0028] The online heat treatment in this embodiment helps to quickly increase the surface temperature of the substrate and the coating, and the adiabatic softening effect of the cold spray particle deposition makes the deposition area in a short period of time at the recovery or recrystallization temperature when subjected to severe plastic deformation, thereby promoting the bonding of the coating substrate and the coating while increasing the recovery and recrystallization ratio, so that the repaired area has high strength and plasticity that exceeds that of a single cold spray; therefore, online heat treatment helps to regulate the substrate and coating structure, thereby improving coating performance.

[0029] 3. The cold spraying of this embodiment uses a high-pressure nitrogen atmosphere, which helps to control the regional temperature of the online heat treatment and prevent oxidation. At the same time, since the plasma device and the cold spraying are separated, the action stage and position of the online heat treatment are more flexible, making it suitable for online repair of auxiliary cold spraying. On this basis, it is also possible to introduce droplet-shaped reinforcement phase particles through plasma spraying to further improve the coating density and mechanical properties by strengthening the strengthening mechanism of the reinforcement phase itself and its filling of the gaps.

[0030] Specific implementation method 2: The difference between this implementation method and specific implementation method 1 is that the aluminum alloy described in step 1 is a 7xxx series aluminum alloy.

[0031] Specific implementation method three: This implementation method is different from specific implementation methods one or two in that: the 7xxx series aluminum alloy is 7075-T6 aluminum alloy.

[0032] Specific implementation method 4: This implementation method is different from any one of specific implementation methods 1 to 3 in that: in step 2, the distance between the cold spray gun muzzle and the surface to be repaired is 25-40 mm.

[0033] Specific implementation method five: This implementation method is different from any one of specific implementation methods one to four in that: the distance between the plasma arc gun muzzle of the plasma device described in step two and the surface to be repaired is 50-150 mm.

[0034] Specific implementation method 6: The difference between this implementation method and any one of specific implementation methods 1 to 5 is that the aluminum alloy powder in step 2 is 7075 aluminum alloy powder, and the powder particle size is 30-50 μm.

[0035] Specific embodiment seven: This embodiment differs from any one of specific embodiments one to six in that: during the cold spraying process in step three, the atmosphere is a nitrogen atmosphere, the nitrogen pressure is 3-6 MPa, and the temperature of the cold spray gun chamber is 450-600°C.

[0036] Specific implementation eight: This implementation differs from any one of specific implementations one to seven in that: the plasma arc power in step three is 20-40KW.

[0037] Specific embodiment 9: This embodiment is different from the specific embodiments 1 to 8 in that: the powder feeding amount in the cold spraying process in step 3 is 10-50cm 3 / min.

[0038] Specific embodiment ten: This embodiment differs from any one of specific embodiments one to nine in that: in step three, before cold spray particle deposition, the plasma device is turned on, and the surface to be repaired is heat treated for 50 seconds using plasma arc; after the cold spray particle deposition is completed in step three, the cold spray powder feeding is stopped, and the resulting coating is heat treated for 50 seconds using plasma arc.

[0039] Example 1

[0040] The method for cold spraying hard repair coating of 7xxx series ultra-high strength aluminum alloy in this embodiment is carried out according to the following steps:

[0041] Step 1: First, grind the surface of the 7075-T6 aluminum alloy to be repaired to remove the defective parts; then, the surface to be repaired is successively treated with aluminum oxide sandblasting with a particle size of 18μm and ultrasonic cleaning with anhydrous ethanol to remove the aluminum oxide film and stains on the surface to be repaired, thereby facilitating cold spray repair deposition;

[0042] Step 2: Fill the aluminum alloy powder into the powder feeder of the cold spraying equipment; adjust the cold spraying device so that the cold spraying gun muzzle is perpendicular to the surface to be repaired, and the distance between the cold spraying gun muzzle and the surface to be repaired is 35 mm; adjust the plasma device so that the generated plasma arc acts on the surface to be repaired, and the distance between the plasma arc gun muzzle of the plasma device and the surface to be repaired is 120 mm;

[0043] The aluminum alloy powder is 7075 aluminum alloy powder, and the powder particle size is 30-50 μm;

[0044] Step 3: Turn on the gas control system of the cold spray device, turn on the plasma device before cold spray particle deposition, and use plasma arc to heat treat the surface to be repaired for 50 seconds; using plasma arc to heat treat the surface to be repaired before cold spray particle deposition can quickly heat up and soften the surface of the area to be repaired, making it easier for subsequent particle deposition to reach the critical thermal and mechanical conditions, thereby improving the bonding between the coating and the substrate. Then turn on the cold spray powder delivery system for cold spray particle deposition, with a powder delivery amount of 15cm 3 / min, cold spray particle deposition is carried out and the repaired surface is heat treated by plasma arc at the same time; during the cold spraying process, the atmosphere is a nitrogen atmosphere with a nitrogen pressure of 5MPa and a temperature of the cold spray gun chamber of 600°C; using plasma arc to heat treat the repaired surface during cold spraying can regulate the structure and properties of the coating, and soften the coating surface and deposited particles, thereby improving the density and performance of the coating. After the cold spray particle deposition is completed, the cold spray powder feeding is stopped, and the obtained coating is heat treated by plasma arc for 50s, and then the cold spray air supply system and plasma device are turned off when the temperature of the cold spray gun chamber drops below 200°C; after the cold spray particle deposition is completed, the obtained coating is heat treated by plasma arc, which can promote the diffusion of the interfaces between particles in the coating, thereby increasing the metallurgical bonding ratio and improving the coating performance. The plasma arc power is 36KW;

[0045] Comparative Example 1

[0046] The method for cold spraying hard repair coating of aluminum alloy in this comparative example is carried out according to the following steps:

[0047] Step 1: First, grind the surface of the 7075-T6 aluminum alloy to be repaired to remove the defective parts; then, the surface to be repaired is successively treated with aluminum oxide sandblasting with a particle size of 18μm and ultrasonic cleaning with anhydrous ethanol to remove the aluminum oxide film and stains on the surface to be repaired, thereby facilitating cold spray repair deposition;

[0048] Step 2: Fill the aluminum alloy powder into the powder feeder of the cold spraying equipment; adjust the cold spraying device so that the cold spraying gun muzzle is perpendicular to the surface to be repaired, and the distance between the cold spraying gun muzzle and the surface to be repaired is 35 mm;

[0049] The aluminum alloy powder is 7075 aluminum alloy powder, and the powder particle size is 30-50 μm;

[0050] Step 3: Turn on the cold spray powder feeding system for cold spraying, with a powder feeding volume of 15cm 3 / min, during the cold spraying process, the atmosphere is nitrogen atmosphere, the nitrogen pressure is 5MPa, and the temperature of the cold spray gun chamber is 600℃; after the cold spraying is completed, the cold spray powder feeding is stopped, and the cold spray gun chamber temperature drops below 200℃, and the cold spray gas supply system is turned off.

[0051] Figure 1 This is a physical picture of the repair coating obtained in Example 1; Figure 2 The temperature variation curves of the repair coating obtained in Example 1 and the coating obtained by single cold spraying in the comparative example; Figure 3 The scanning electron microscope images of the cross section of the repair coating obtained in Example 1 and the coating obtained by single cold spraying in the comparative example; Figure 4 This is a comparison chart of the Vickers hardness of the repair coating obtained in Example 1 and the coating obtained by single cold spraying in the comparative example. Figures 1 to 4 It can be seen that compared with the comparative example, the repair coating obtained in Example 1 has a significantly lower porosity and a significantly higher density in the repair coating obtained by cold spraying under the assistance of plasma, and the interface between the coating and the substrate is more compact. The average Vickers hardness of the repair coating obtained in Example 1 reaches 134.7 HV 0.5 .

[0052] Example 2

[0053] The method for cold spraying hard repair coating of 7xxx series ultra-high strength aluminum alloy in this embodiment is carried out according to the following steps:

[0054] Step 1: First, grind the surface of the 7075-T6 aluminum alloy to be repaired to remove the defective parts; then, the surface to be repaired is successively treated with aluminum oxide sandblasting with a particle size of 18μm and ultrasonic cleaning with anhydrous ethanol to remove the aluminum oxide film and stains on the surface to be repaired, thereby facilitating cold spray repair deposition;

[0055] Step 2: Fill the aluminum alloy powder into the powder feeder of the cold spray equipment; adjust the cold spray device so that the cold spray gun muzzle is perpendicular to the surface to be repaired, and the distance between the cold spray gun muzzle and the surface to be repaired is 30mm; adjust the plasma device so that the generated plasma arc acts on the surface to be repaired, and the distance between the plasma arc gun muzzle of the plasma device and the surface to be repaired is 100mm

[0056] The aluminum alloy powder is 7075 aluminum alloy powder, and the powder particle size is 30-50 μm;

[0057] Step 3: Turn on the gas control system of the cold spray device, turn on the plasma device before cold spray particle deposition, and use plasma arc to heat treat the surface to be repaired for 30 seconds; using plasma arc to heat treat the surface to be repaired before cold spray particle deposition can quickly heat up and soften the surface of the area to be repaired, making it easier for subsequent particle deposition to reach the critical thermal and mechanical conditions, thereby improving the bonding between the coating and the substrate. Then turn on the cold spray powder delivery system for cold spray particle deposition, with a powder delivery volume of 20cm 3 / min, cold spray particle deposition is carried out and the repaired surface is heat treated by plasma arc at the same time; during the cold spraying process, the atmosphere is a nitrogen atmosphere, the nitrogen pressure is 4MPa, and the temperature of the cold spray gun chamber is 550℃; using plasma arc to heat treat the repaired surface during cold spraying can regulate the structure and properties of the coating, and soften the coating surface and deposited particles, thereby improving the density and performance of the coating. After the cold spray particle deposition is completed, the cold spray powder feeding is stopped, and the obtained coating is heat treated by plasma arc for 30s, and then the cold spray air supply system and plasma device are turned off when the temperature of the cold spray gun chamber drops below 200℃; after the cold spray particle deposition is completed, the obtained coating is heat treated by plasma arc, which can promote the diffusion of the interface between particles in the coating, thereby increasing the metallurgical bonding ratio and improving the coating performance. The plasma arc power is 32KW;

[0058] In Example 2, the porosity of the repair coating obtained by cold spraying under plasma assistance is greatly reduced, the density is greatly improved, and the interface between the coating and the substrate is more compact. The average Vickers hardness of the repair coating obtained in Example 2 reaches 134.7 HV 0.5 .

Claims

1. A method for cold spraying hard repair coating on 7xxx series ultra-high strength aluminum alloy, characterized in that: The method for cold spraying hard repair coating of 7xxx series ultra-high strength aluminum alloy is carried out in the following steps: Step 1: First, grind the surface of the aluminum alloy to be repaired to remove the defective parts; Then the surface to be repaired is successively sandblasted and ultrasonically cleaned with anhydrous ethanol to remove the aluminum oxide film and stains on the surface to be repaired, thereby facilitating the cold spray repair deposition; Step 2: Fill the aluminum alloy powder into the powder feeder of the cold spraying equipment; Adjust the cold spray device so that the cold spray gun muzzle is perpendicular to the surface to be repaired, and adjust the plasma device so that the generated plasma arc acts on the surface to be repaired; Step 3: Turn on the gas control system of the cold spray device, turn on the plasma device before cold spray particle deposition, and use plasma arc to heat treat the surface to be repaired for 30-60 seconds; Then, the cold spray powder feeding system is turned on to perform cold spray particle deposition, and the repaired surface is heat treated by plasma arc at the same time; after the cold spray particle deposition is completed, the cold spray powder feeding is stopped, and the obtained coating is heat treated by plasma arc for 30-60s. Then, when the temperature of the cold spray gun chamber drops below 200°C, the cold spray gas supply system and the plasma device are turned off.

2. The method for cold spraying hard repair coating of 7xxx series ultra-high strength aluminum alloy according to claim 1, characterized in that: The aluminum alloy described in step 1 is a 7xxx series aluminum alloy.

3. The method for cold spraying hard repair coating of 7xxx series ultra-high strength aluminum alloy according to claim 1, characterized in that: The 7xxx series aluminum alloy is 7075-T6 aluminum alloy.

4. The method for cold spraying hard repair coating of 7xxx series ultra-high strength aluminum alloy according to claim 1, characterized in that: In step 2, the distance between the cold spray gun muzzle and the surface to be repaired is 25-40 mm.

5. The method for cold spraying hard repair coating of 7xxx series ultra-high strength aluminum alloy according to claim 1, characterized in that: In step 2, the distance between the plasma arc gun muzzle of the plasma device and the surface to be repaired is 50-150 mm.

6. The method for cold spraying hard repair coating of 7xxx series ultra-high strength aluminum alloy according to claim 1, characterized in that: The aluminum alloy powder in step 2 is 7075 aluminum alloy powder, and the powder particle size is 30-50 μm.

7. The method for cold spraying hard repair coating of 7xxx series ultra-high strength aluminum alloy according to claim 1, characterized in that: During the cold spraying process in step 3, the atmosphere is a nitrogen atmosphere, the nitrogen pressure is 3-6 MPa, and the temperature of the cold spray gun chamber is 450-600°C.

8. The method for cold spraying hard repair coating of 7xxx series ultra-high strength aluminum alloy according to claim 1, characterized in that: The plasma arc power in step 3 is 20-40KW.

9. The method for cold spraying hard repair coating of 7xxx series ultra-high strength aluminum alloy according to claim 1, characterized in that: During the cold spraying process in step 3, the powder feeding amount is 10-50cm 3 / min.

10. The method for cold spraying hard repair coating of 7xxx series ultra-high strength aluminum alloy according to claim 1, characterized in that: In step 3, the plasma device is turned on before cold spray particle deposition, and the surface to be repaired is heat treated for 50 seconds using plasma arc. After the cold spray particle deposition in step 3 is completed, the cold spray powder feeding is stopped, and the obtained coating is heat treated for 50 seconds using plasma arc.

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