A method for cold spraying and use of the method for producing an aluminium alloy coating with high strength at cold conditions

Abstract

The application relates to a method for preparing an aluminum alloy coating with high strength under cold conditions by cold spraying and application. The application belongs to the field of cold spraying coating and repair. The application aims to solve the technical problem of low hardness and tensile strength of the existing cold spraying repair aluminum alloy coating under cold conditions. The method of the application: using gas-atomized high-strength aluminum alloy powder as the raw material, through the high-pressure cold spraying deposition technology, using argon, nitrogen or helium as the main gas, depositing the gas-atomized aluminum alloy powder on the preheated substrate, and adjusting the pressure and temperature of the accelerating gas according to the selected gas type to promote the second-phase dynamic precipitation and recrystallization process of the deposition process. The application has great advantages in the repair and remanufacturing field of high-strength aluminum alloy key components in aerospace and the like, and can solve the problems that the cold spraying high-strength aluminum alloy coating has no nano precipitates, the repaired parts cannot be heat treated as a whole, and the strength and hardness of the coating are difficult to meet the repair requirements of high-strength aluminum alloy structural parts.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of cold spraying coating and repair, and particularly relates to a method for preparing an aluminum alloy coating with high strength under cold conditions by cold spraying and application. BACKGROUND

[0002] High-strength aluminum alloys, including 2-series and 7-series aluminum alloys, are a kind of aluminum alloys that can be strengthened by heat treatment. The series of alloys have high specific strength, good toughness, easy processing and other advantages, and are widely used in light-weight high-strength structural parts in important fields such as aerospace and rail transportation. For example, the high-strength structural parts of the wing skin, keel beam, fuselage stringer and internal support of Boeing 777 aircraft all use 7xxx series aluminum alloys. The surface of aluminum alloy structural parts is easily damaged in shape and size by mechanical and corrosion effects during long-term service. Traditional repair and remanufacturing technologies such as surfacing, laser cladding and thermal spraying face great challenges in repairing high-strength aluminum alloy structural parts, and are prone to cause problems such as oxidation, thermal deformation and cracking. Therefore, it is urgent to develop a new repair and remanufacturing technology for high-strength aluminum alloy components.

[0003] Cold spraying technology is a new type of remanufacturing technology that uses preheated high-pressure gas to carry micron-sized (10-70 μm) metal particles, which are accelerated through a Laval nozzle and collide with the surface of the substrate at high speed. The particles are combined with the substrate through severe plastic deformation, and the coating is prepared by layer-by-layer deposition or the parts are quickly repaired. As a new type of remanufacturing technology, its unique low-temperature characteristics can avoid problems such as thermal deformation and cracking. Therefore, it has a very broad application prospect in the repair of large, thin-walled aluminum alloy and other metal components, especially in the field of aerospace remanufacturing. The hardness and tensile strength of the cold sprayed aluminum alloy coating are still at a low level (70-130 HV and 200-340 MPa), which limits the application of cold spraying technology in the repair and remanufacturing of high-strength aluminum alloy structural parts. Although subsequent heat treatment can promote the precipitation of the second phase of cold sprayed high-strength aluminum alloy and improve its mechanical properties. However, many parts are not allowed to be subjected to subsequent heat treatment due to material organization degradation, thermal deformation, assembly and other reasons. Therefore, it is very important to control the microstructure of 7xxx series aluminum alloy under cold conditions, improve the hardness and strength of the cold sprayed repair coating, and meet the service requirements, so as to apply cold spraying technology to the repair and remanufacturing of key high-strength aluminum alloy structural parts in the aerospace field. SUMMARY

[0004] The purpose of the present application is to solve the technical problem of low hardness and tensile strength of cold sprayed aluminum alloy coating under cold conditions, and to provide a method for preparing an aluminum alloy coating with high strength under cold conditions by cold spraying and application.

[0005] The purpose of the present application is achieved by the following technical solutions:

[0006] One of the purposes of the present application is to provide a method for preparing an aluminum alloy coating with high strength under cold conditions by cold spraying, which is carried out in the following steps:

[0007] S1: first sandblasting the substrate, and then preheating to a specified temperature;

[0008] S2: using cold spraying technology, depositing gas-atomized aluminum alloy powder on the preheated substrate with argon or nitrogen as the main gas, the main gas pressure being 3.0-5.0 MPa, the powder feeding gas pressure being 3.5-5.5 MPa, and the main gas temperature being 500-550℃.

[0009] Preferably, the substrate in S1 is selected from aluminum and its alloys or magnesium alloys.

[0010] More preferably, the aluminum alloy includes 2-series, 3-series, 4-series, 5-series, 6-series, and 7-series aluminum alloys.

[0011] More preferably, the magnesium alloy includes AZ31B, AZ91D, and ZK61M magnesium alloys.

[0012] Preferably, the sandblasting in S1 reaches a surface roughness of 12 μm or more.

[0013] More preferably, the sand is 80-220 mesh white corundum alumina sand, and the sandblasting air pressure is 0.7-1.5 MPa.

[0014] Preferably, the substrate in S1 is preheated to 180-300℃.

[0015] Preferably, the gas-atomized aluminum alloy powder in S2 is prepared by gas atomization of 2-series, 6-series, or 7-series aluminum alloys.

[0016] More preferably, the gas-atomized aluminum alloy powder has a particle size range of 5-75 μm, and a D50 of 20-45 μm.

[0017] Preferably, the nozzle in S2 is a SiC or WC-Co Laval nozzle.

[0018] Another purpose of the present application is to provide a method for preparing an aluminum alloy coating with high strength under cold conditions by cold spraying, which is carried out in the following steps:

[0019] S1: first sandblasting the substrate, and then preheating to a specified temperature;

[0020] S2: using cold spraying technology, depositing gas-atomized aluminum alloy powder on the preheated substrate with helium as the main gas, the main gas pressure being 2.6-3.5 MPa, the powder feeding gas pressure being 2.8-3.8 MPa, and the main gas temperature being 200-350℃.

[0021] Preferably, the substrate in S1 is selected from aluminum and its alloys or magnesium alloys.

[0022] More preferably, the aluminum alloy comprises 2-series, 3-series, 4-series, 5-series, 6-series, 7-series aluminum alloy.

[0023] More preferably, the magnesium alloy comprises AZ31B, AZ91D, ZK61M magnesium alloy.

[0024] Preferably, the grit blasting in S1 reaches a surface roughness of 12 μm or above.

[0025] More preferably, the grit is 80-220 mesh white corundum alumina grit, and the blasting pressure is 0.7-1.5 MPa.

[0026] Preferably, the substrate in S1 is preheated to 180-300℃.

[0027] Preferably, the gas atomized aluminum alloy powder in S2 is prepared by gas atomization of 2-series, 6-series or 7-series aluminum alloy.

[0028] More preferably, the gas atomized aluminum alloy powder has a particle size range of 5-75 μm, and a D50 of 20-45 μm.

[0029] Preferably, the nozzle in S2 is a PBI nozzle.

[0030] The third object of the present application is to provide an aluminum alloy coating with high strength under cold conditions, obtained by the above method, wherein the dynamic precipitates in the coating are uniformly distributed, with a size of 10-200 nm and a content reaching or approaching that of the T6 heat treatment state.

[0031] Preferably, the grain size in the coating presents a gradient distribution, with a grain size of 5 nm-300 nm at the interface of the powder particles and a grain size of 500 nm-5 μm inside the powder particles.

[0032] The fourth object of the present application is to provide an application of the above method in the repair of high-strength aluminum alloy components.

[0033] The present application has the following remarkable effects compared with the prior art:

[0034] The application adopts gas atomized high-strength aluminum alloy powder as raw material, realizes rapid deposition preparation of high-strength aluminum alloy coating through high-pressure cold spraying deposition technology. The coating deposition process is mainly promoted by preheating the substrate and improving the temperature of the main gas to promote the thermal accumulation, and the particle plastic deformation in the aluminum alloy powder deposition process is accurately controlled to promote the in-situ precipitation and dynamic recrystallization of the second phase under the strong thermal-mechanical coupling effect, so that the hardness and strength of the aluminum alloy coating are greatly improved. The application has great advantages in the field of repair and remanufacturing of high-strength aluminum alloy key parts in aerospace and other fields, and can solve the problems such as no nano precipitates in the cold sprayed high-strength aluminum alloy coating, and the repaired parts cannot be heat treated as a whole, so that the strength and hardness of the coating cannot meet the repair requirements of high-strength aluminum alloy structural parts. The specific advantages are as follows:

[0035] (1) The application adopts a new method of cold spraying to prepare high-strength aluminum alloy coating in-situ strengthening, compared with the conventional cold spraying technology, the second phase dynamic precipitation and grain refinement of the high-strength aluminum alloy coating can be realized by accurately controlling the cold spraying parameters, and the strength and hardness of the coating are significantly improved.

[0036] (2) According to different types of main gas, the application adjusts the main gas pressure and temperature and cooperates with the use of different material spray guns when high-strength aluminum alloy is cold sprayed and deposited, so that continuous deposition of high-strength aluminum alloy coating can be realized, the deposition efficiency is high, and the gun blocking phenomenon does not occur.

[0037] (3) The application is suitable for cold spraying rapid repair of aluminum alloy or magnesium alloy parts, and high-strength aluminum alloy coating can be obtained through in-situ precipitation strengthening and fine-grain strengthening effect, which can avoid the influence of subsequent heat treatment process on the original organization of the repaired parts, and at the same time simplify the repair process and reduce the cost.

[0038] (4) Compared with the repair process of thermal spraying and laser cladding, the prepared coating has high density and high bonding strength, which can avoid problems such as oxidation and stress cracking, and has excellent comprehensive performance. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 Figure 1 is a SEM image of the microstructure and morphology of the 7-series high-strength aluminum alloy coating in Example 3 and the comparative example; a-Example 3, b-Comparative example;

[0040] Figure 2 Figure 2 is a TEM photo of the 7-series high-strength aluminum alloy coating in Example 3; a-Intense deformation area at the powder particle interface, b-Powder particle interior;

[0041] Figure 3 Figure 3 is a TEM photo of the 7-series high-strength aluminum alloy coating without optimized parameters in the comparative example;

[0042] Figure 4The hardness and mechanical properties of the high-strength aluminum alloy coating in Example 3 and the comparative example 7 are compared in the following chart. DETAILED DESCRIPTION

[0043] In one embodiment of the present application, a method for preparing an aluminum alloy coating with high strength under cold conditions by cold spraying is provided, and the method is performed according to the following steps:

[0044] (1) Using 80-220 mesh white corundum alumina sand as sand, the substrate is sandblasted at a jet pressure of 0.7-1.5 MPa, and the surface roughness is greater than 12 μm after sandblasting, and then preheated to 180-300 °C;

[0045] The substrate is selected from aluminum and its alloys or magnesium alloys, and the aluminum alloy includes 2 series, 3 series, 4 series, 5 series, 6 series, and 7 series aluminum alloys, and the magnesium alloy includes AZ31B, AZ91D, and ZK61M magnesium alloys.

[0046] (2) The gas-atomized aluminum alloy powder is prepared by high-purity argon or nitrogen atomization method, the aluminum alloy powder is in a near-spherical shape, and the particle size range is 5-75 μm after screening, and the D50 is 20-45 μm, and then the powder is dried at 150 °C for 6 hours, and used as a cold spraying raw material, and the alloying elements in the gas-atomized powder are in a completely solid solution state;

[0047] The gas-atomized aluminum alloy powder is made of 2 series, 6 series, and 7 series aluminum alloys.

[0048] (3) The cold spraying technology is used to deposit the gas-atomized aluminum alloy powder on the preheated substrate using argon, nitrogen, or helium as the main gas, and the pressure and temperature of the accelerating gas can be adjusted according to the type of the selected gas, and the particle velocity and temperature of the metal powder particles after being accelerated by the high-pressure and high-temperature gas are required to be above 650 m / s and 150 °C, respectively;

[0049] When argon or nitrogen is used as the main gas, the main gas pressure is 3.0-5.0 MPa, the powder feeding gas pressure is 3.5-5.5 MPa, the main gas temperature is 500-550 °C, SiC or WC-Co Laval nozzles are selected, and the nozzles are cooled during the experiment to reduce the phenomenon of gun plugging caused by excessive temperature of the powder.

[0050] When helium is used as the main gas, the main gas pressure is 2.6-3.5 MPa, the powder feeding gas pressure is 2.8-3.8 MPa, and the main gas temperature is 200-350 °C, and PBI nozzles are used.

[0051] In the specific embodiments of the present application, the gas atomized high-strength aluminum alloy powder is used as the initial material, the heat accumulation of the deposition process is promoted by preheating the substrate and adjusting the temperature of the main gas, and the plastic deformation of the aluminum alloy powder particles is regulated, thereby promoting the in-situ precipitation strengthening and fine-grain strengthening of the cold sprayed aluminum alloy coating, greatly improving the strength and hardness of the aluminum alloy. On the one hand, the aluminum alloy coating can be rapidly deposited on the surface of the aluminum alloy or magnesium alloy substrate, and on the other hand, the cold spraying can be used as a repair and remanufacturing means to rapidly repair the damaged aluminum alloy or magnesium alloy parts, thereby prolonging the service life of the parts.

[0052] In the specific embodiments of the present application, the plastic deformation of the particles is mainly achieved by regulating the pressure, temperature and type of the accelerating gas, so as to change the collision speed and temperature of the particles. The heat accumulation regulation is mainly achieved by regulating the preheating temperature of the substrate and the temperature of the main gas.

[0053] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0054] The experimental methods used in the following examples are all conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained by commercial channels by those skilled in the art.

[0055] The terms "comprising", "including", "having", "containing", or any other similar forms, used in the following examples, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article or device that comprises the listed elements does not necessarily limit those elements to only those elements, but can include other elements not explicitly listed or inherent to such composition, step, method, article or device.

[0056] When an equivalent, concentration, or other value or parameter is expressed in a range, a preferred range, or a range having an upper preferred value and a lower preferred value, it is understood that all ranges formed by any pair of an upper limit or a preferred value and a lower limit or a preferred value, whether or not the range is expressly disclosed, are specifically disclosed. For example, when the range "1 to 5" is disclosed, the described range should be interpreted to include the range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values and all integers and fractions within the range. In the specification and claims of the present application, the range definitions can be combined and / or interchanged, unless otherwise stated, and these ranges include all sub-ranges contained therein.

[0057] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0058] In this invention, "an embodiment" or "embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments.

[0059] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0060] Example 1: A method for preparing a high-strength aluminum alloy coating under cold conditions by cold spraying is carried out according to the following steps:

[0061] (1) Using 200-mesh alumina white corundum sand as abrasive, the 2024 aluminum alloy substrate (100×100×5mm) was sandblasted under a jet pressure of 1.2MPa until the surface roughness reached more than 12μm. Then, it was placed in alcohol for ultrasonic cleaning for 10 minutes, then dried, and then preheated to 240℃.

[0062] (2) High-purity argon gas atomization method was used to prepare gas atomized 2024 aluminum alloy powder. The aluminum alloy powder was nearly spherical, and the particle size range after sieving was 5-75μm, with D50 of 37μm. The powder was then dried at 150℃ for 6 hours and used as raw material for cold spraying. The alloy elements in the gas atomized powder were in a completely solid solution state.

[0063] (3) Cold spraying technology was adopted, using nitrogen as the main gas to deposit atomized 2024 aluminum alloy powder onto a preheated 2024 aluminum alloy substrate. The main gas pressure was 3.5 MPa, the powder feeding pressure was 3.8 MPa, the main gas temperature was 500℃, the powder flow rate was 80 g / min, the spraying distance was 35 mm, the spray gun moving speed was 50 mm / s, and the coating was applied in 10 passes. A SiC spray gun was used, and cooling water was used to cool the spray gun during the spraying process. Finally, a 600 μm thick 2024 aluminum alloy coating was deposited on the 2024 aluminum alloy substrate.

[0064] After spraying, the microstructure of the cold sprayed coating was observed by TEM. A large number of Al2Cu nano phases were found to precipitate in the aluminum alloy substrate. The coating was tested for hardness according to ASTM-633 standard, and the average hardness of the coating was 125 HV 0.1 The interfacial bonding strength of the coating and the substrate was tested according to ASTM-C633 standard, and the interfacial bonding strength reached 36 MPa.

[0065] Example 2, a method for preparing an aluminum alloy coating with high strength under cold conditions by cold spraying was carried out according to the following steps:

[0066] (1) 160-mesh alumina white corundum sand was used as sand, and the AZ91D magnesium alloy substrate (100x100x5mm) was sandblasted at a jet pressure of 1.5 MPa. The surface roughness was greater than 12 μm after sandblasting, and then the substrate was ultrasonically cleaned in alcohol for 10 minutes, followed by drying and preheating to 200°C.

[0067] (2) High-purity argon gas atomization method was used to prepare gas-atomized 6061 aluminum alloy powder. The aluminum alloy powder was nearly spherical, and the particle size range was 5-75 μm after sieving, and D50 was 35 μm. The powder was then dried at 150°C for 6 hours and used as the original material for cold spraying. The alloying elements in the gas-atomized powder were in a completely solid solution state.

[0068] (3) The cold spraying technology was used to deposit the gas-atomized 6061 aluminum alloy powder on the preheated AZ91D magnesium alloy substrate using argon as the main gas. The main gas pressure was 3.0 MPa, the powder feeding gas pressure was 3.5 MPa, the main gas temperature was 550°C, the spraying powder flow rate was 80 g / min, the spraying distance was 35 mm, the spraying gun moving speed was 50 mm / s, the coating spraying number was 10, a WC-Co spraying gun was used, and cooling water was used to cool the spraying gun during the spraying process. Finally, a 6061 aluminum alloy coating with a thickness of 700 μm was deposited on the AZ91D magnesium alloy substrate.

[0069] After spraying, the microstructure of the cold sprayed coating was observed by TEM. A large number of Mg2Si nano phases were found to precipitate in the aluminum alloy substrate. The coating was tested for hardness according to ASTM-633 standard, and the average hardness of the coating was 110 HV 0.1 The interfacial bonding strength of the coating and the substrate was tested according to ASTM-C633 standard, and the interfacial bonding strength reached 32 MPa.

[0070] Example 3, a method for preparing an aluminum alloy coating with high strength under cold conditions by cold spraying was carried out according to the following steps:

[0071] (1) The 7075 aluminum alloy substrate (100x100x5mm) was sandblasted with 200 mesh alumina white corundum sand under a jet pressure of 1.2 MPa, and the surface roughness reached more than 12 μm. Then the substrate was ultrasonically cleaned in alcohol for 10 minutes, and then dried and preheated to 180°C.

[0072] (2) The gas-atomized 7075 aluminum alloy powder was prepared by high-purity argon gas atomization method. The aluminum alloy powder was nearly spherical, and the particle size range was 10-70 μm after screening, and D50 was 39 μm. Then the powder was dried at 150°C for 6 hours, and used as the original material for cold spraying. The alloying elements in the gas-atomized powder were in a completely solid solution state.

[0073] (3) The gas-atomized 7075 aluminum alloy powder was deposited on the preheated 7075 aluminum alloy substrate by cold spraying technology using helium as the main gas. The main gas pressure was 2.8 MPa, the powder feeding gas pressure was 3.2 MPa, the main gas temperature was 320°C, the spraying powder flow rate was 100 g / min, the spraying distance was 35 mm, the spraying gun moving speed was 50 mm / s, and the coating was sprayed for 10 passes. A PBI spraying gun was used, and finally a 7075 aluminum alloy coating with a thickness of 900 μm was deposited on the substrate.

[0074] The difference between this comparative example and Example 3 is that argon is used as the main gas, the main gas pressure is 3 MPa, the main gas temperature is 500°C, and the substrate is not preheated. The other steps and parameters are the same as those of Example 3.

[0075] After spraying, the microstructure of the cold sprayed coating was observed by SEM and TEM, and the results are shown in Figures 1-2 From Figure 1 it can be seen that, compared with the unoptimized parameters of the comparative example, the powder particles undergo more severe plastic deformation, and the grain size at the particle interface is significantly refined. From Figure 2 (a) it can be seen that recrystallization occurs at the particle interface, and the grain size is about 10-120 nm. From Figure 2 (b) it can be seen that a large number of η precipitates are formed inside the deformed particles, the size of the precipitates is 5-30 nm, and the content is 1.8 vol%. From Figure 3 it can be seen that, using the unoptimized parameters of the comparative example to deposit the 7075 Al coating, no nano-precipitates are observed inside the deformed grains.

[0076] The coating was tested for hardness according to ASTM-633 standard, and the average hardness of the coating was 148 HV 0.1The hardness is obviously higher than that of the comparative example before optimization. The bonding strength between the coating and the substrate is tested according to the ASTM-C633 standard, and the interface bonding strength reaches 42 MPa. The tensile strength of the coating is tested according to the ASTM-E8M standard, and the tensile strength reaches 452 MPa, which is obviously higher than that of the comparative example before optimization, as shown in Table 1. Figure 4

[0077] The above merely provides the preferred embodiments of the present application, which are different implementations based on the overall concept of the present application, and the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.​

Claims

1. A method for cold spraying to produce an aluminum alloy coating having high strength under cold conditions, characterized by, The steps are as follows: S1: first sandblasting the substrate, and then preheating to 180-300℃; S2: using cold spraying technology, argon or nitrogen as the main gas, depositing gas-atomized aluminum alloy powder on the preheated substrate, the main gas pressure is 3.0-5.0 MPa, the powder feeding gas pressure is 3.5-5.5 MPa, and the main gas temperature is 500-550℃; The gas-atomized aluminum alloy powder is prepared by gas atomization of 2 series, 6 series or 7 series aluminum alloy.

2. The method of claim 1, wherein, The nozzle in S2 is a SiC or WC-Co Laval nozzle.

3. A method for cold spraying to produce an aluminum alloy coating having high strength under cold conditions, characterized by, The steps are as follows: S1: first sandblasting the substrate, and then preheating to 180-300℃; S2: using cold spraying technology, helium as the main gas, depositing gas-atomized aluminum alloy powder on the preheated substrate, the main gas pressure is 2.6-3.5 MPa, the powder feeding gas pressure is 2.8-3.8 MPa, and the main gas temperature is 200-350℃; The gas-atomized aluminum alloy powder is prepared by gas atomization of 2 series, 6 series or 7 series aluminum alloy.

4. The method according to claim 1 or 3, characterized in that, The substrate in S1 is selected from aluminum and its alloys or magnesium alloys, and the sandblasting is to a surface roughness of 12 μm or more.

5. The method of claim 4, wherein, The aluminum alloy of the substrate includes 2 series, 3 series, 4 series, 5 series, 6 series, and 7 series aluminum alloys, the magnesium alloy of the substrate includes AZ31B, AZ91D, and ZK61M magnesium alloys, the sand is 80-220 mesh alumina white corundum sand, and the sandblasting air pressure is 0.7-1.5 MPa.

6. The method according to claim 1 or 3, characterized in that, The gas-atomized aluminum alloy powder in S2 has a particle size range of 5-75 μm, and a D50 of 20-45 μm.

7. The method of claim 3, wherein, The nozzle in S2 is a PBI nozzle.

8. The aluminum alloy coating having high strength under cold conditions obtained by the method of claim 1 or 3, characterized in that, The precipitated phase in the coating is uniformly distributed, with a size of 10-200 nm, and a content reaching or close to the T6 heat treatment state.

9. The aluminum alloy coating of claim 8, wherein, The grain size in the coating presents a gradient distribution, with a grain size of 5 nm-300 nm at the powder particle interface and a grain size of 500 nm-5 μm inside the powder particle.

10. The method of claim 1 or 3 for repairing high-strength aluminum alloy components.

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