A method of additive repair of metal damage

Abstract

This invention relates to the field of cold spray remanufacturing technology and discloses an additive repair method for metal damage, including steps such as pretreatment of the repair area, preparation of a porous transition layer, and spraying a filling deposit. The repair method prepares a porous transition layer on the surface of the area to be repaired. Utilizing the porous characteristics of the transition layer, an adhesion layer conducive to cold spray deposition is constructed. Micro-regions conducive to powder particle deposition are formed on the sidewalls of the area to be repaired, making it easier for powder particles to be captured and deposited by the porous transition layer when impacting the sidewalls, thereby achieving a high-strength bond and improving the overall bonding strength between the repair deposit and the area to be repaired. Furthermore, during the high-speed impact of the powder particles, the pores within the porous transition layer are compacted and compressed, ultimately forming a dense deposit filling body, greatly improving the repair quality and enhancing the secondary service performance and service life of the repaired metal component.

Description

Technical Field

[0001] This invention relates to the field of cold spray remanufacturing technology, and more particularly to an additive repair method for metal damage. Background Technology

[0002] Cold spraying is an emerging solid-state additive manufacturing technology. Its principle involves using gas propulsion to propel powder particles at supersonic speeds to impact a substrate, thereby achieving deposition and bonding. Due to its advantages such as unlimited deposition thickness and high manufacturing efficiency, cold spraying has gradually developed into a rapid additive manufacturing technology. Its low-temperature characteristic minimizes the thermal impact on metal materials during the spraying process, preventing problems such as oxidation, phase transformation, or crystallization. Furthermore, the deposits prepared by cold spraying have extremely low porosity, and the performance of some deposits can rival that of bulk materials. Therefore, cold spraying technology is highly suitable for the secondary repair of damaged components.

[0003] However, since the bonding strength between the deposited material and the metal substrate prepared by cold spraying is directly related to the impact velocity of the particles, the deposition quality of this process is highly sensitive to the spraying angle. When the spraying angle deviates from 90° (the spraying angle is 90° when the spraying direction is perpendicular to the deposition surface), the larger the deviation angle, the greater the impact velocity component, and the significantly reduced effective impact velocity, thus reducing the bonding strength between the deposited material and the metal substrate. When cold spraying technology is used in additive repair methods for metal damage, due to the randomness of the metal damage area and depth, it is inevitable that the actual spraying angle will deviate from the ideal angle (90°). This will lead to insufficient bonding strength between the deposited material and the sidewall of the area to be repaired (damaged area), relying mainly on bonding with the bottom surface of the area to be repaired to achieve additive deposition. The repair quality is poor, and cracks and pores are prone to occur at the deposition interface, affecting the service performance and lifespan of the repaired metal component.

[0004] To address the aforementioned issues, existing solutions typically involve enlarging the damaged area and using large chamfers or bevels (angles greater than 45°) to transition the sidewalls from the bottom to the surface of the damaged area. This minimizes the deviation of the effective spraying angle when spraying the sidewalls, allowing the powder particles generated by cold spraying to deposit at the chamfers or bevels to connect the bottom and sidewalls of the damaged area, thereby enhancing the adhesion between the deposit and the sidewalls.

[0005] However, for deeper metal damage, large-angle chamfering of the sidewalls of the damaged area will excessively expand the damaged area, causing additional losses during the repair process. In addition, it is difficult to achieve large-angle chamfering of the sidewalls of the damaged area for small-sized parts. As a result, there are still problems with excessive spraying angle and deposition surface during additive repair, which leads to insufficient bonding strength of the deposit in the horizontal direction. Summary of the Invention

[0006] The purpose of this invention is to provide an additive repair method for metal damage, which aims to solve the problem of insufficient lateral bonding strength in the damaged area of ​​the cold spray technology in additive repair, which affects the service performance and life of the repaired metal parts.

[0007] This invention provides an additive repair method for metal damage, comprising the following steps: S1. Pre-treat the area to be repaired; S2. Prepare a porous transition layer on the surface of the pretreated area to be repaired. S3. Based on the depth direction of the area to be repaired, the filling deposit is sprayed layer by layer from deep to shallow; S4. Based on the shape and size of the original metal parts, perform post-processing on the repair area to remove the redundant amount of deposits generated during the repair.

[0008] Furthermore, in the additive repair method for metal damage, step S1 includes: The sidewalls of the area to be repaired are sprayed with blind spots to remove them, so that the angle between each sidewall of the area to be repaired and the bottom of the area to be repaired is not less than 90°. Remove any burrs from the area to be repaired. After removing the burrs, clean the oil stains from the surface of the area to be repaired. After cleaning the oil stains, dry the area to be repaired.

[0009] Furthermore, in step S2, the porosity of the porous transition layer is 5-20%; the thickness of the porous transition layer is 200-500 μm.

[0010] Furthermore, in step S2, the porous transition layer is formed by first powder spraying or laser directional deposition onto the surface of the area to be repaired; the spraying process parameters are as follows: Main gas flow rate: 45-50 slm; Powder delivery airflow rate: 5-6 slm; Voltage 65-70V; Current 420-450A; Spraying distance: 120-150mm; Gun movement speed: 180~200mm / s.

[0011] Furthermore, in step S2, the first powder is at least one of copper powder, aluminum powder, iron powder, nickel powder, titanium powder, and alloy powder particles; the particle size range of the first powder is 45-75 μm.

[0012] Furthermore, in the additive repair method for metal damage, step S3 includes: Preheat the area to be repaired and the porous transition layer; After preheating, a filling deposit is formed by spraying and scanning layer by layer from deep to shallow based on the depth direction of the area to be repaired. Spraying is stopped when the height of the filling deposit reaches or exceeds the designed surface of the metal part before the damage.

[0013] Furthermore, in step S3, the filler deposit is formed by second powder spraying, with the following spraying process parameters: Main gas pressure 4-5 MPa; Main gas temperature 200–600℃; Powder delivery airflow rate: 200-220 slm; Powder feeding rate: 60-90 g / min; Spraying distance: 20-25mm; Gun movement speed: 80-100mm / s.

[0014] Furthermore, in step S3, the preheating temperature is 200–600°C.

[0015] Furthermore, in the additive repair method for metal damage, the second powder is at least one of copper powder, aluminum powder, iron powder, nickel powder, titanium powder, and alloy powder particles.

[0016] Furthermore, in the additive repair method for metal damage, the particle size of the second powder ranges from 15 to 45 μm.

[0017] The beneficial effects of this invention are: This invention provides an additive repair method for metal damage. A porous transition layer is prepared on the surface of the area to be repaired. Utilizing the porous characteristics of the transition layer, an adhesion layer conducive to cold spray deposition is constructed. Micro-regions facilitating powder particle deposition are formed on the sidewalls of the repair area. This allows powder particles to be more easily captured and deposited by the porous transition layer when impacting the sidewalls of the repair area, thereby achieving a high-strength bond and improving the overall bonding strength between the repair deposit and the repair area. Furthermore, during the high-speed impact of the powder particles, the pores within the porous transition layer are compacted and compressed, ultimately forming a dense deposited filler, which greatly improves the repair quality and enhances the secondary service performance and service life of the repaired metal component. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process of cleaning and removing blind spots in the spraying process.

[0019] Figure 2 This is a simplified flowchart of the additive repair method for metal damage provided by the present invention.

[0020] Figure 3 This is a schematic diagram of the metal damage repair process.

[0021] Figure 4 These are before-and-after comparison images of the aluminum alloy plate repaired in Example 1.

[0022] Figure 5 These are before-and-after comparison images of the copper alloy component repaired in Example 4. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Please see Figure 2 , Figure 3 This invention provides an additive repair method for metal damage, comprising the following steps: S1. Pre-treat the area to be repaired; S2. Prepare a porous transition layer on the surface of the pretreated area to be repaired. S3. Based on the depth direction of the area to be repaired, the filling deposit is sprayed layer by layer from deep to shallow; S4. Based on the shape and size of the original metal parts, perform post-processing on the repair area to remove the redundant amount of deposits generated during the repair.

[0025] Because randomly generated metal damage often has sharp inner corners and hidden blind spots (such as... Figure 1 As shown), such areas will form spray shadows and cannot be effectively treated by conventional processes. Therefore, in the above-mentioned additive repair method for metal damage, the area to be repaired is first pretreated to remove spray blind spots, thereby fully exposing the surface to be repaired (e.g., Figure 1 As shown in the figure, it provides an unobstructed, repairable interface for the subsequent preparation of porous transition layers and cold spray deposition.

[0026] After removing the spraying blind spots, a porous transition layer is prepared on the surface of the area to be repaired (damaged area). The porous nature of this transition layer allows for the creation of an adhesion layer conducive to cold spray deposition. Micro-regions facilitating powder particle deposition are formed on the sidewalls of the area to be repaired, making it easier for powder particles to be captured and deposited when impacting the sidewalls. This results in a high-strength bond and enhances the overall bonding strength between the repair deposit and the area to be repaired. Furthermore, during the high-speed impact of the powder particles, the pores within the porous transition layer are compacted and compressed, ultimately forming a dense deposit filling body. This significantly improves the repair quality and enhances the secondary service performance and lifespan of the repaired metal components.

[0027] Finally, after stopping the spraying of the filler deposit, the redundant amount of deposit generated during the repair process can be removed by post-processing the repaired area, thereby restoring the original size of the metal part and realizing additive repair of the damaged metal area.

[0028] It is understandable that the porous transition layer can be prepared on the sidewall surface of the area to be repaired, or it can be prepared on both the sidewall surface and the bottom of the area to be repaired.

[0029] In order to eliminate blind spots in the coating, in a preferred embodiment, step S1 specifically includes the following steps: The sidewalls of the area to be repaired are sprayed with blind spots to remove them, so that the angle between each sidewall of the area to be repaired and the bottom of the area to be repaired is not less than 90°. Remove any burrs from the area to be repaired. After removing the burrs, clean the oil stains from the surface of the area to be repaired. After cleaning the oil stains, dry the area to be repaired.

[0030] By processing the metal components near the damaged area, the angle between each sidewall of the area to be repaired and the bottom of the area to be repaired can be no less than 90°. This ensures that the damaged area is fully exposed within the spraying operation range, eliminating shadow areas during spraying. The effective spray deposition range under vertical spraying conditions can cover all surfaces within the damaged area. For deeper metal surface damage, where the sidewalls of the damaged area are too deep, to improve the bonding strength between the filler deposit and the sidewalls of the damaged area, multi-step circumferential grooving can be performed along the sidewall direction of the damaged area (e.g., ...). Figure 3 As shown in the figure, a porous transition layer is then prepared on each step and sidewall. Finally, stepwise cold spraying deposition is used to fill the layer, which can enhance the bonding force between the entire filled deposit and the surface of the damaged area.

[0031] After removing the blind spots in the spraying process, removing burrs from the area to be repaired, cleaning oil stains, and drying the repair area can eliminate adverse factors that affect the deposition bonding. This prevents burrs and oil stains from causing poor bonding between the porous transition layer and the damaged area surface, ensuring the uniform and stable preparation of the subsequent porous transition layer. It also improves the bonding strength and repair quality between the cold spray filling deposit and the area to be repaired, ensuring the service performance and service life of the repaired metal parts.

[0032] The porosity of the porous transition layer affects the bonding strength between the filler deposit and the damaged area surface. If the porosity is too high, effective compaction of the pores within the transition layer cannot be achieved during subsequent cold spray repair deposition, resulting in a slightly more porous intermediate layer at the interface between the transition layer and the filler deposit, which in turn affects the bonding strength between the filler deposit and the damaged area surface. Conversely, if the porosity is too low, it is difficult to form micro-deposition micro-regions on the transition layer surface that facilitate the capture and adhesion of cold spray powder particles. When powder particles impact the sidewall of the damaged area, they will still rebound due to the offset of the spray impact angle, failing to fully utilize the role of the porous transition layer in improving the lateral bonding strength between the filler deposit and the sidewall of the damaged area. Therefore, in a preferred embodiment, the porosity of the porous transition layer is preferably controlled between 5% and 20%, which can simultaneously ensure pore compaction and powder particle adhesion, maximizing the overall bonding strength between the repair deposit and the damaged area.

[0033] The thickness of the porous transition layer also affects the bonding strength between the filler deposit and the damaged area surface. If the porous transition layer is too thin, it is difficult to form a continuous and complete micro-deposition micro-region in the area to be repaired, making it difficult to effectively improve the lateral deposition bonding effect and failing to fully utilize the role of the porous transition layer in enhancing the lateral bonding strength between the filler deposit and the sidewall of the damaged area. On the other hand, if the porous transition layer is too thick, it will not only increase the spraying cost and process time, but also make it difficult to effectively compact the pores inside the porous transition layer during subsequent cold spray repair deposition, affecting the bonding strength between the filler deposit and the damaged area surface. Therefore, in order to improve the deposition repair effect, in a preferred embodiment, the thickness of the porous transition layer is controlled to be 200–500 μm.

[0034] In order to prepare a porous transition layer on the surface of the pretreated area to be repaired, in a preferred embodiment, the porous transition layer is formed by thermal spraying a first powder onto the surface of the area to be repaired, wherein the thermal spraying is plasma spraying, and the plasma spraying process parameters are as follows: Main gas flow rate: 45-50 slm; Powder delivery airflow rate: 5-6 slm; Voltage 65-70V; Current 420-450A; Spraying distance: 120-150mm; Gun movement speed: 180~200mm / s.

[0035] In the aforementioned thermal spraying process parameters, argon (Ar) can be used as the main gas, and hydrogen can be used as the powder feeding gas. For example, in addition to plasma spraying, the thermal spraying can also be flame spraying, arc spraying, laser spraying, supersonic flame spraying, etc. Besides the thermal spraying methods listed above, laser-directed deposition or other heat source additive manufacturing technologies can also be used to prepare a porous transition layer on the surface of the area to be repaired.

[0036] Among the aforementioned thermal spraying process parameters, the spraying distance significantly impacts the forming quality of the porous transition layer. When the spraying distance is too far, the powder particles travel too long, resulting in a substantial decrease in velocity and energy, and insufficient impact kinetic energy. This makes it difficult to form effective deposition and bonding on the surface of the area to be repaired, leading to poor density of the porous transition layer and low bonding strength with the surface of the area to be repaired. Furthermore, insufficient impact kinetic energy can cause powder particles to bounce back after impacting the surface of the area to be repaired, reducing deposition efficiency. Conversely, when the spraying distance is too close, the high-temperature airflow can easily cause erosion and thermal damage to the porous transition layer, disrupting its microstructure and morphology. This can also lead to uneven powder deposition, localized overheating, and increased internal stress, affecting interlayer bonding strength and repair stability. Therefore, to ensure the forming quality and interlayer bonding strength of the porous transition layer, the optimal distance for the thermal spraying gun during thermal spraying of the surface of the area to be repaired is controlled within the aforementioned range.

[0037] In the aforementioned thermal spraying process parameters, the power of the heat source also affects the forming quality of the porous transition layer and the bonding strength between the filler deposit and the area to be repaired. When the heat source power (the product of voltage and current) is too high, the powder particles are overheated, easily leading to oxidation, burning, splashing, and spheroidization. This results in a coarse porous transition layer structure, increased internal stress, and weakened bonding with the area to be repaired. Furthermore, it damages the pore structure of the porous transition layer, affecting the bonding between the filler deposit and the porous transition layer, and failing to effectively improve the overall bonding strength between the filler deposit and the area to be repaired. Conversely, when the heat source power is too low, the powder particles are insufficiently heated, melted incompletely, and lack impact kinetic energy, failing to form a continuous and dense porous transition layer on the surface of the area to be repaired. This leads to poor bonding strength between the porous transition layer and the surface of the area to be repaired, failing to provide a stable and effective adhesion interface for subsequent cold spraying, thus affecting the repair effect. Therefore, to improve the forming quality of the porous transition layer and further enhance the overall bonding strength between the filler deposit and the area to be repaired, the working voltage and current during thermal spraying are optimally controlled within the aforementioned ranges.

[0038] In step S2, the first powder is at least one of copper powder, aluminum powder, iron powder, nickel powder, titanium powder, and alloy powder particles. The selection of the first powder can be adjusted based on the material of the metal component to be repaired. In a preferred embodiment, the first powder and the metal component to be repaired are both made of the same metal material, which enables the porous transition layer and the metal component to maintain the same coefficient of thermal expansion, crystal structure, and interface compatibility, effectively reducing the internal stress and cracking risk at the interface, and improving the bonding strength between the porous transition layer and the area to be repaired; at the same time, matching materials can avoid electrochemical corrosion between dissimilar metals, ensuring the stability and service life of the repaired metal component in complex service environments, and further strengthening the overall bonding effect between the filling deposit and the damaged area.

[0039] In the process of preparing a porous transition layer, the particle size of the first powder affects the forming quality, microstructure, and bonding strength between the filling deposit and the area to be repaired. When the particle size of the first powder is too coarse, the powder particles do not melt sufficiently when heated, resulting in excessive impact kinetic energy. This easily leads to erosion of the surface of the area to be repaired, making it difficult to form a uniform porous transition layer and failing to provide an effective adhesion substrate for subsequent cold spraying. When the particle size of the first powder is too fine, the powder particles are prone to overheating, leading to oxidation, splashing, and spheroidization. This results in poor powder feeding, decreased process stability, and difficulty in forming micro-deposition micro-regions conducive to the capture and adhesion of cold spraying powder particles, thus reducing the bonding strength between the filling deposit and the porous transition layer. In a preferred embodiment, the particle size of the first powder is in the range of 45 to 75 μm. This ensures that the first powder is heated evenly and melts appropriately during the thermal spraying process, and can stably form a porous transition layer with porosity and layer thickness that meet the design requirements. This allows for the construction of an ideal micro-adhesion micro-region, thereby significantly improving the bonding strength between the porous transition layer and the surface of the area to be repaired and the filling deposit, ensuring the service performance and service life of the repaired metal parts.

[0040] To enhance the depositional bonding strength between the filling deposit and the porous transition layer and the area to be repaired, in a preferred embodiment, step S3 includes: Preheat the area to be repaired and the porous transition layer; After preheating, a filling deposit is formed by spraying and scanning layer by layer from deep to shallow based on the depth direction of the area to be repaired. Spraying is stopped when the height of the filling deposit reaches or exceeds the designed surface of the metal part before the damage.

[0041] Specifically, before the spraying repair, the area to be repaired and the porous transition layer are scanned and preheated using the temperature of the spraying gas without powder delivery. This increases the temperature of the area to be repaired and the porous transition layer, strengthening the bonding strength between the filler deposit and the area to be repaired and the porous transition layer, thus improving the repair quality. When the height of the filler deposit reaches or exceeds the designed surface of the metal component before damage, spraying is stopped. This ensures that the repaired area is restored to the original shape and dimensions of the metal component after machining, while also ensuring sufficient filling of the deposit without depressions or missing material. This improves the dimensional accuracy, structural integrity, and secondary service reliability of the repaired metal component.

[0042] To improve the density of the filler deposit and enhance its mechanical strength, structural stability, and service durability (increasing the service life of the repair layer), in a preferred embodiment, the filler deposit is formed by cold spraying a second powder. The cold spraying process parameters are as follows: Main gas pressure 4-5 MPa; Main gas temperature 200–600℃; Powder delivery airflow rate: 200-220 slm; Powder feeding rate: 60-90 g / min; Spraying distance: 20-25mm; Gun movement speed: 80-100mm / s.

[0043] In the above-mentioned cold spraying process parameters, nitrogen can be used for both the main gas and the powder delivery gas.

[0044] For example, the second powder can be at least one of copper powder, aluminum powder, iron powder, nickel powder, titanium powder, and alloy powder particles. In a preferred embodiment, the second powder, the first powder, and the metal part to be repaired are all made of the same metal material, which can ensure that the metal part, the porous transition layer, and the filling deposit maintain consistent material properties, coefficient of thermal expansion, and interfacial compatibility. This can reduce the internal stress and cracking tendency between interfaces, improve the overall bonding strength, and enhance the secondary service performance and service life of the repaired metal part.

[0045] In the cold spray deposition repair process, the particle size of the second powder directly affects the density, bonding strength, and forming stability of the filled deposit. When the particle size of the second powder is too coarse, the particle impact kinetic energy is too high, which easily causes erosion damage to the porous transition layer. Furthermore, the particles are difficult to fully plastically deform and interlock, leading to increased porosity, decreased density, and reduced interfacial bonding strength within the deposit. Conversely, when the particle size of the second powder is too fine, the particles are prone to overheating, agglomeration, splashing, and even ablation. This not only worsens the powder delivery stability but also causes the deposit layer to become loose and internal stress to increase, similarly failing to form a filled deposit with high density and high bonding strength. Therefore, in a preferred embodiment, the particle size range of the second powder is 15–45 μm. This allows the second powder particles to obtain moderate kinetic energy and plastic deformation capacity during the cold spray process, enabling the powder particles to be captured and deposited by the porous transition layer while avoiding erosion, agglomeration, and ablation. This effectively improves the density and interfacial bonding strength of the filled deposit, thereby enhancing the repair quality.

[0046] To simplify the process, in a preferred embodiment, the preheating temperature of the area to be repaired and the porous transition layer is 200–600°C. This preheating temperature can be consistent with the main gas temperature of the second powder spraying, allowing direct reuse of the gas heating system of the cold spraying equipment without the need for an additional independent heat source. This simplifies the process and reduces energy consumption and production costs. At the same time, temperature matching can prevent the concentration of interfacial thermal stress, cracking or deformation of the porous transition layer due to excessive temperature difference, ensuring uniform and sufficient preheating. This further enhances the bonding strength and density between the filler deposit, the porous transition layer, and the area to be repaired, resulting in more stable repair quality.

[0047] The present invention will be further illustrated by the following examples and comparative examples.

[0048] Example 1 This embodiment provides an additive repair method for metal damage, specifically targeting deep crack damage in aluminum alloy plates, including the following steps: S10. Based on the crack depth, V-groove processing is performed on the aluminum alloy plate to ensure that there are no hidden cracks inside the metal plate. Then, blind zone processing is performed on the sidewall of the area to be repaired to remove the blind zone, so that the angle between each sidewall and its bottom in the area to be repaired is not less than 90°. S11. Remove burrs from the area to be repaired. After removing the burrs, clean the oil stains on the surface of the area to be repaired. S12. After cleaning the oil stains, dry the area to be repaired. S20. Using plasma spraying technology, atomized Al6061 with a particle size range of 45-75μm is used as powder material and thermally sprayed onto the area to be repaired to form a porous transition layer; the porosity of the porous transition layer is 11% and the layer thickness is 240μm. S31. Preheat the area to be repaired and the porous transition layer at a preheating temperature of 350°C. S32. After preheating, a cold spraying process is used to spray and scan from deep to shallow in the longitudinal direction of the area to be repaired to form a filling deposit. Spraying is stopped when the height of the filling deposit reaches or exceeds the designed surface of the metal part before the damage. S40. Based on the shape and size of the original aluminum alloy plate, perform post-processing on the repair area to remove the redundant deposits generated during the repair process.

[0049] In step S20, the spraying process parameters are as follows: Main gas (argon) flow rate: 45 slm; The flow rate of the powder gas (hydrogen) is 6 slm. Voltage 70V; Current 450A; Spraying distance: 120mm; Gun movement speed: 180mm / s.

[0050] In step S32, the cold spraying uses gas-atomized Al6061 with a particle size range of 15–45 μm as the powder material. The cold spraying process parameters are as follows: Main gas (nitrogen) pressure: 4 MPa; Main gas (nitrogen) temperature 350℃; Nitrogen gas flow rate: 200 slm; Powder feeding rate: 60g / min; Spraying distance: 25mm; Gun movement speed: 80mm / s.

[0051] Example 2 This embodiment provides an additive repair method for metal damage, specifically targeting deep crack damage in aluminum alloy plates, including the following steps: S10. Based on the crack depth, V-groove processing is performed on the aluminum alloy plate to ensure that there are no hidden cracks inside the metal plate. Then, blind zone processing is performed on the sidewall of the area to be repaired to remove the blind zone, so that the angle between each sidewall and its bottom in the area to be repaired is not less than 90°. S11. Remove burrs from the area to be repaired. After removing the burrs, clean the oil stains on the surface of the area to be repaired. S12. After cleaning the oil stains, dry the area to be repaired. S20. Using plasma spraying technology, atomized Al6061 with a particle size range of 45-75μm is used as powder material and thermally sprayed onto the area to be repaired to form a porous transition layer; the porosity of the porous transition layer is 10% and the layer thickness is 200μm. S31. Preheat the area to be repaired and the porous transition layer at a preheating temperature of 350°C. S32. After preheating, a cold spraying process is used to spray and scan from deep to shallow in the longitudinal direction of the area to be repaired to form a filling deposit. Spraying is stopped when the height of the filling deposit reaches or exceeds the designed surface of the metal part before the damage. S40. Based on the shape and size of the original aluminum alloy plate, perform post-processing on the repair area to remove the redundant deposits generated during the repair process.

[0052] In step S20, the spraying process parameters are as follows: Main gas (argon) flow rate: 45 slm; The flow rate of the powder gas (hydrogen) is 6 slm. Voltage 70V; Current 450A; Spraying distance: 120mm; Gun movement speed: 180mm / s.

[0053] In step S32, the cold spraying uses gas-atomized Al6061 with a particle size range of 15–45 μm as the powder material. The cold spraying process parameters are as follows: Main gas (nitrogen) pressure 5 MPa; Main gas (nitrogen) temperature 350℃; Nitrogen gas flow rate: 200 slm; Powder feeding rate: 60g / min; Spraying distance: 25mm; Gun movement speed: 80mm / s.

[0054] Example 3 This embodiment provides an additive repair method for metal damage, specifically targeting deep crack damage in aluminum alloy plates, including the following steps: S10. Based on the crack depth, V-groove processing is performed on the aluminum alloy plate to ensure that there are no hidden cracks inside the metal plate. Then, blind zone processing is performed on the sidewall of the area to be repaired to remove the blind zone, so that the angle between each sidewall and its bottom in the area to be repaired is not less than 90°. S11. Remove burrs from the area to be repaired. After removing the burrs, clean the oil stains on the surface of the area to be repaired. S12. After cleaning the oil stains, dry the area to be repaired. S20. Using plasma spraying technology, atomized Al6061 with a particle size range of 45-75μm is used as powder material and thermally sprayed onto the area to be repaired to form a porous transition layer; the porosity of the porous transition layer is 13% and the layer thickness is 500μm. S31. Preheat the area to be repaired and the porous transition layer at a preheating temperature of 350°C. S32. After preheating, a cold spraying process is used to spray and scan from deep to shallow in the longitudinal direction of the area to be repaired to form a filling deposit. Spraying is stopped when the height of the filling deposit reaches or exceeds the designed surface of the metal part before the damage. S40. Based on the shape and size of the original aluminum alloy plate, perform post-processing on the repair area to remove the redundant deposits generated during the repair process.

[0055] In step S20, the spraying process parameters are as follows: Main gas (argon) flow rate: 45 slm; The flow rate of the powder gas (hydrogen) is 6 slm. Voltage 70V; Current 450A; Spraying distance: 120mm; Gun movement speed: 180mm / s.

[0056] In step S32, the cold spraying uses gas-atomized Al6061 with a particle size range of 15–45 μm as the powder material. The cold spraying process parameters are as follows: Main gas (nitrogen) pressure: 4 MPa; Main gas (nitrogen) temperature 350℃; Nitrogen gas flow rate: 200 slm; Powder feeding rate: 60g / min; Spraying distance: 20mm; Gun movement speed: 80mm / s.

[0057] Example 4 This embodiment provides an additive repair method for metal damage, specifically for friction damage on copper alloy components (CuCrZr), including the following steps: S10. According to the wear defects, the sidewalls of the area to be repaired are sprayed with blind spots to remove the wear defects, so that the angle between each sidewall and its bottom in the area to be repaired is not less than 90°. S11. Remove burrs from the area to be repaired. After removing the burrs, clean the oil stains on the surface of the area to be repaired. S12. After cleaning the oil stains, dry the area to be repaired. S20. A plasma spraying process is used, with gas-atomized CuCrZr powder with a particle size range of 45-75μm as the raw material, which is thermally sprayed onto the area to be repaired to form a porous transition layer; the porosity of the porous transition layer is 16%, and the layer thickness is 420μm. S31. Preheat the area to be repaired and the porous transition layer at a preheating temperature of 450°C. S32. After preheating, a cold spraying process is used to spray and scan from deep to shallow in the longitudinal direction of the area to be repaired to form a filling deposit. Spraying is stopped when the height of the filling deposit reaches or exceeds the designed surface of the metal part before the damage. S40. Based on the shape and size of the original copper alloy component, perform post-processing on the repair area to remove the redundant deposits generated during the repair process.

[0058] In step S20, the spraying process parameters are as follows: Main gas (argon) flow rate: 50 slm; The flow rate of the powder gas (hydrogen) is 5 slm; Voltage 65V; Current 420A; Spraying distance: 130mm; Gun movement speed: 180mm / s.

[0059] In step S32, the cold spraying uses gas-atomized CuCrZr with a particle size range of 15–45 μm as the powder raw material. The cold spraying process parameters are as follows: Main gas (nitrogen) pressure: 4 MPa; The temperature of the main gas (nitrogen) is 600℃; Nitrogen gas flow rate: 220 slm; Powder feeding rate: 90g / min; Spraying distance: 25mm; Gun movement speed: 100mm / s.

[0060] Comparative Example 1 This comparative example provides an additive repair method for metal damage, specifically for deep crack damage in aluminum alloy plates. The difference between this additive repair method and the additive repair method provided in Example 1 is that steps S20 and S31 are omitted. After the area to be repaired is dried, a cold spraying process is directly used to scan and spray the surface of the area to be repaired to form a filling deposit.

[0061] Comparative Example 2 This comparative example provides an additive repair method for metal damage, specifically targeting deep crack damage in aluminum alloy plates. The only difference between this additive repair method and the one provided in Example 1 is the plasma spraying process parameters in step 20, where the spraying distance is 90 mm. The porosity of the porous transition layer is 9.7%, and the thickness of the porous transition layer is 510 μm.

[0062] Comparative Example 3 This comparative example provides an additive repair method for metal damage, specifically targeting deep crack damage in aluminum alloy plates. The only difference between this additive repair method and the one provided in Example 1 is the plasma spraying process parameters in step 20, where the spraying distance is 160 mm. The porosity of the porous transition layer is 20.5%, and the thickness of the porous transition layer is 340 μm.

[0063] Comparative Example 4 This comparative example provides an additive repair method for metal damage, specifically targeting deep crack damage in aluminum alloy plates. The only difference between this additive repair method and the one provided in Example 1 is the plasma spraying process parameters in step 20: the spraying voltage is 50V and the spraying current is 400A. The porosity of the porous transition layer is 21.6%, and the thickness of the porous transition layer is 350μm.

[0064] Comparative Example 5 This comparative example provides an additive repair method for metal damage, specifically targeting deep crack damage in aluminum alloy plates. The only difference between this additive repair method and the one provided in Example 1 is the plasma spraying process parameters in step 20: the spraying voltage is 75V and the spraying current is 500A. The porosity of the porous transition layer is 10.8%, and the thickness of the porous transition layer is 530μm.

[0065] Comparative Example 6 This comparative example provides an additive repair method for metal damage, specifically for deep crack damage in aluminum alloy plates. The only difference between this additive repair method and the additive repair method provided in Example 1 is that in step 20, gas-atomized Al6061 with a particle size range of 15–45 μm is used as the powder raw material, the porosity of the porous transition layer is 11.2%, and the thickness of the porous transition layer is 520 μm.

[0066] Comparative Example 7 This comparative example provides an additive repair method for metal damage, specifically for deep crack damage in aluminum alloy plates. The only difference between this additive repair method and the additive repair method provided in Example 1 is that in step S32, the cold spray uses gas-atomized Al6061 with a particle size range of 45-65 μm as the powder material.

[0067] The metal parts repaired by the additive repair methods for metal damage provided in Examples 1-3 and Comparative Examples 1-7 were tested. Tensile tests were performed on the bonding area between the filler deposit (i.e., the deposited repair layer) and the metal parts. The tests were conducted in accordance with the provisions of standard GB_T6396-2008 "Metallic steel plates - Test methods for mechanical and technological properties" and standard GB / T228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature". The test results are shown in Table 1 below.

[0068] Table 1

[0069] As can be seen from the test results in Table 1, after repairing the metal parts using the additive repair methods for metal damage provided in Examples 1-3, the bonding strength between the filling deposit and the metal parts is significantly improved compared to Comparative Example 1. This indicates that by preparing a porous transition layer on the surface of the area to be repaired, the overall bonding strength between the repair deposit and the repair area can be improved.

[0070] from Figure 4 The comparison images before and after the repair of the aluminum alloy plate show that after the aluminum alloy plate is repaired and finely processed by the additive repair method provided by this invention, the damaged area is completely filled and smoothly transitions with the surface of the aluminum alloy plate. There are no defects such as cracks, pores, or dents on the surface. After the repair, the appearance and size of the aluminum alloy plate are restored to the design standard, and the overall structure is complete and uniform.

[0071] from Figure 5 The comparison images of the copper alloy component before and after repair show that before repair, the surface of the copper alloy component had obvious friction and wear, local pits and material loss. After repair using the additive repair method provided by this invention, the wear pits were fully filled and densified, the surface of the repaired area was smooth and flat, and the appearance, outline dimensions and surface quality of the copper alloy component could be restored to the service requirements.

[0072] Furthermore, comparing the tensile strength test results of Comparative Example 2 and Example 1, it was found that when the thermal spraying distance was closer, the tensile strength of the joint between the filler deposit and the metal part decreased. This is because when the spraying distance was closer, the forming quality of the porous transition layer decreased, which weakened the bonding strength between the filler deposit and the porous transition layer.

[0073] Furthermore, comparing the tensile strength test results of Comparative Example 3 and Example 1, it was found that when the thermal spraying distance was far, the tensile strength of the bonding area between the filler deposit and the metal component decreased. This is because when the thermal spraying distance was far, the impact kinetic energy of the first powder was insufficient, making it difficult to form an effective deposit and bond on the surface of the area to be repaired. This resulted in poor density of the porous transition layer (the porosity of the porous transition layer would increase), and low bonding force with the surface of the area to be repaired. Consequently, the filler deposit could not effectively bond with the metal component through the porous transition layer.

[0074] Furthermore, comparing the tensile strength test results of Comparative Example 4 and Example 1, it was found that when the heat source power of thermal spraying was low, the tensile strength of the bonding area between the filler deposit and the metal component decreased. This is because when the heat source power was low, the first powder particles were not heated enough, the melting was insufficient, and the impact kinetic energy was insufficient, so a continuous and dense porous transition layer could not be formed on the surface of the area to be repaired. This resulted in a poor bonding strength between the porous transition layer and the surface of the area to be repaired, which could not provide a stable and effective adhesion interface for subsequent cold spraying, thus affecting the bonding between the filler deposit and the metal component.

[0075] Furthermore, comparing the tensile strength test results of Comparative Example 5 and Example 1, it was found that when the heat source power of thermal spraying is high, the tensile strength of the joint between the filler deposit and the metal component decreases. This is because when the heat source power is high, the porous transition layer structure becomes coarse, the internal stress increases, and the bond with the area to be repaired weakens, so that the filler deposit cannot effectively maintain its bond with the metal component through the porous transition layer.

[0076] Furthermore, comparing the tensile strength test results of Comparative Example 6 and Example 1, it was found that when the particle size of the first powder particles was too fine, the tensile strength of the bonding area between the filler deposit and the metal component decreased. This is because when the particle size of the first powder particles is too fine, the first powder particles are easily overheated, making it difficult to form micro-deposition micro-regions that are conducive to the capture and adhesion of cold spray powder particles. As a result, the filler deposit cannot effectively maintain its bond with the metal component through the porous transition layer.

[0077] Furthermore, comparing the tensile strength test results of Comparative Example 7 and Example 1, it was found that when the particle size of the second powder particles was relatively coarse, the tensile strength at the junction of the filling deposit and the metal component decreased. This is because when the particle size of the second powder particles was relatively coarse, the impact kinetic energy of the particles was too large, which easily caused erosion damage to the porous transition layer. In addition, it was difficult for the particles to fully plastically deform and interlock, resulting in an increase in pores and a decrease in density inside the filling deposit, and a reduction in the interfacial bonding strength.

[0078] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method of additive repair of metal damage, characterized in that, Includes the following steps: S1. Pre-treat the area to be repaired; S2. Prepare a porous transition layer on the surface of the pretreated area to be repaired. S3. Based on the depth direction of the area to be repaired, the filling deposit is sprayed layer by layer from deep to shallow; S4. Based on the shape and size of the original metal parts, perform post-processing on the repair area to remove the redundant amount of deposition generated during the repair. In step S2, the porosity of the porous transition layer is 5-20%; the thickness of the porous transition layer is 200-500 μm. In step S2, the porous transition layer is formed by first powder spraying or laser directional deposition onto the surface of the area to be repaired; the spraying process parameters are as follows: Main gas flow rate: 45-50 slm; Powder delivery airflow rate: 5-6 slm; Voltage 65-70V; Current 420-450A; Spraying distance: 120-150mm; Gun movement speed: 180~200mm / s; The particle size range of the first powder is 45–75 μm; In step S3, the filler deposit is formed by second powder spraying, and the spraying process parameters are as follows: Main gas pressure 4-5 MPa; Main gas temperature 200–600℃; Powder delivery airflow rate: 200-220 slm; Powder feeding rate: 60-90 g / min; Spraying distance: 20-25mm; Gun movement speed: 80-100 mm / s; The particle size range of the second powder is 15–45 μm.

2. The method of additive repair of metal damage according to claim 1, characterized in that, Step S1 includes: The sidewalls of the area to be repaired are sprayed with blind spots to remove them, so that the angle between each sidewall of the area to be repaired and the bottom of the area to be repaired is not less than 90°. Remove any burrs from the area to be repaired. After removing the burrs, clean the oil stains from the surface of the area to be repaired. After cleaning the oil stains, dry the area to be repaired.

3. The method of additive repair of metal damage according to claim 1, characterized in that, In step S2, the first powder is at least one of copper powder, aluminum powder, iron powder, nickel powder, titanium powder, and alloy powder particles.

4. The method of additive repair of metal damage according to claim 1, characterized in that, Step S3 includes: Preheat the area to be repaired and the porous transition layer; After preheating, a filling deposit is formed by spraying and scanning layer by layer from deep to shallow based on the depth direction of the area to be repaired. Spraying is stopped when the height of the filling deposit reaches or exceeds the designed surface of the metal part before the damage.

5. The method of additive repair of metal damage according to claim 1, characterized in that, The second powder is at least one of copper powder, aluminum powder, iron powder, nickel powder, titanium powder, and alloy powder particles.

6. The method of additive repair of metal damage according to claim 4, characterized in that, In step S3, the preheating temperature is 200–600°C.

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