Laser cladding method for preparing copper-based composite material coating on copper alloy substrate

Abstract

The invention belongs to the technical field of metal material preparation, and particularly relates to a laser cladding method for preparing a copper-based composite material coating on a copper alloy substrate. Comprising the following steps that chromium diboride and graphite serve as strengthening phases and are mixed with Cu powder, and Cu-based composite powder is obtained in a powder mixing and ball milling mode in sequence; the Cu-based composite powder comprises the following components in percentage by volume: 0vol.%-1vol.% of graphite, 1vol.%-5vol.% of chromium diboride and the balance of Cu, and the total amount is 100%; and the Cu-based composite powder is cladded on the surface of the copper alloy in a laser cladding mode, and the copper-based composite material coating is obtained. According to the method, the copper-coated graphite powder, the chromium diboride powder and the Cu powder serve as raw materials, the copper-based composite material coating is successfully prepared on the copper alloy substrate through the laser cladding technology, the performance of the surface of the copper alloy can be improved, and a more economical scheme can be provided for repairing a damaged mobile electric contact part.

Description

Technical Field

[0001] This invention belongs to the field of metal material preparation technology, specifically relating to a laser cladding method for preparing a copper-based composite material coating on a copper alloy substrate. Background Technology

[0002] Copper alloys possess excellent thermal and electrical conductivity, making them ideal for current-carrying moving contact components. However, with the rapid development of high-speed railways and military electronic equipment, the requirements for the wear resistance of copper alloys are becoming increasingly stringent. Due to the low hardness and poor wear resistance of copper and its alloys, they are easily damaged in harsh environments with high relative speeds and current transmission densities. Although most damage to moving electrical contact components occurs within a few hundred micrometers to a few millimeters of the surface, they are often replaced entirely during maintenance, resulting in significant economic losses, resource waste, and even environmental pollution.

[0003] Laser cladding technology is becoming increasingly popular in many fields to extend the lifespan of current-carrying moving contact components, offering advantages such as operational flexibility, high efficiency, and high automation. During laser cladding, powder material and a thin substrate are melted by a high-power laser, forming a low-dilution metallurgical bond. Pure metal cladding layers are insufficient to improve the wear resistance of copper substrates, making the surface of current-carrying moving contact components prone to damage during use. Therefore, developing high-performance composite coating technology for laser cladding on copper substrates not only improves the performance of copper alloy surfaces but also provides a more economical solution for repairing damaged moving electrical contacts. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a laser cladding method for preparing copper-based composite material coatings on copper alloy substrates. Using chromium diboride and graphite as reinforcing phases, Cu-based composite powder was successfully used to prepare copper-based composite material coatings on copper alloy substrates via laser cladding. This not only improves the surface properties of the copper alloy but also provides a more economical solution for repairing damaged moving electrical contact components.

[0005] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0006] The purpose of this invention is to provide a laser cladding method for preparing a copper-based composite material coating on a copper alloy substrate, comprising the following steps: S1. Using chromium diboride and graphite as reinforcing phases, and mixing them with Cu powder, Cu-based composite powder is prepared by three-dimensional vibration mixing and high-energy ball milling. The Cu-based composite powder, by volume percentage, consists of 0 vol.% to 1 vol.% graphite, 1 vol.% to 5 vol.% chromium diboride, and the balance being Cu, totaling 100%.

[0007] S2. Using a copper alloy as a substrate, Cu-based composite powder is clad onto the surface of the copper alloy by laser cladding to obtain a copper-based composite material coating.

[0008] Furthermore, during the laser cladding process, the thickness of the copper-based composite material coating is 2.1 mm to 2.3 mm using a repetitive laser cladding method.

[0009] Furthermore, during the laser cladding process, argon gas is used as both the protective gas and the powder feeding gas. The flow rate of the protective gas is 4.2 L / min to 4.7 L / min, the flow rate of the powder feeding gas is 3.6 L / min to 3.7 L / min, the overlap rate is 44%, the defocusing amount is 8.3 mm, the scanning speed is 778 mm / min, and the laser power is 1780 W.

[0010] Furthermore, the preparation method of Cu-based composite powder includes the following steps: mixing copper powder, chromium diboride powder and copper-coated graphite powder, and then sequentially using vibration mixing and ball milling under protective gas to obtain Cu-based composite powder.

[0011] Furthermore, the particle size of the copper powder is 48μm to 50μm, the particle size of the chromium diboride powder is 1μm to 5μm, and the particle size of the copper-coated graphite powder is 48μm to 50μm.

[0012] Furthermore, during the vibration mixing process, the material-to-ball ratio is 3:1, the mixing frequency is 50Hz, and the mixing time is 3h.

[0013] Furthermore, during the ball milling process, anhydrous ethanol is added to the mixture at a concentration of 0.1 wt% to 0.5 wt% of the mixture. The ball milling is carried out under a protective gas for 4 to 8 hours, with a material-to-ball ratio of 1:5.

[0014] Furthermore, during the ball milling process, the ball milling is carried out in an alternating manner of forward rotation + stop + reverse rotation for 4 to 8 hours, with the forward rotation time being 30 minutes, the stop time being 12 minutes, and the reverse rotation time being 30 minutes.

[0015] Furthermore, before laser cladding, the copper alloy plate is subjected to sandblasting and blackening treatment. The blackening treatment involves placing the sandblasted copper alloy plate in carbon ink for 4 to 5 minutes and then holding it at 120°C for 10 minutes.

[0016] Furthermore, before laser cladding, the copper alloy plate is preheated to 50℃~80℃.

[0017] Compared with the prior art, the present invention has the following advantages: This invention provides a laser cladding method for preparing copper-based composite material coatings on copper alloy substrates. Using Cu-based composite powder with chromium diboride and graphite as reinforcing phases, a copper-based composite material coating was successfully prepared on the copper alloy substrate via laser cladding. During the laser cladding process, high-energy laser beam irradiation forms a localized high-temperature molten pool, resulting in a metallurgical bond between the coating and the substrate with high bonding strength. The hard phase of chromium diboride, distributed within the Cu matrix, acts as a "skeleton," effectively hindering plastic flow on the wear surface and improving wear resistance. The self-lubricating phase of graphite easily forms a lubricating film on the surface during wear, reducing the coefficient of friction and preventing adhesive wear, thereby improving the current-carrying tribological wear performance of the composite coating. The prepared copper-based composite material coating exhibits a conductivity of 58%–70% IACS, a coefficient of friction of 0.4–0.6, and a volumetric wear rate 70%–80% lower than that of the comparative sample QCr0.5 copper alloy. This invention provides a reliable process for preparing copper-based composite material coatings on copper alloy substrates. The preparation process is simple and highly automated, which not only improves the performance of copper alloy surfaces but also provides a more economical solution for repairing damaged moving electrical contact components. Attached Figure Description

[0018] Figure 1 This is a physical image of the copper-based composite material coating prepared in Example 2 of the present invention.

[0019] Figure 2 These are 5000x magnification microstructure images of the copper-based composite material coatings prepared in Examples 1 to 4 of this invention. Figure 2 (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4. Detailed Implementation

[0020] 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0022] This invention provides a laser cladding method for preparing a copper-based composite material coating on a copper alloy substrate, comprising the following steps: S1. Mix copper powder, chromium diboride powder and copper-coated graphite powder, and then use three-dimensional vibration mixing and high-energy ball milling under protective gas to obtain Cu-based composite powder. The Cu-based composite powder, by volume percentage, is 0 vol.% to 1 vol.% graphite, 1 vol.% to 5 vol.% chromium diboride, and the balance is Cu, totaling 100%.

[0023] In this invention, the copper powder has a particle size of 48μm to 50μm, the chromium diboride powder has a particle size of 1μm to 5μm, and the copper-coated graphite powder has a particle size of 48μm to 50μm. After mixing the electrolytic copper powder, chromium diboride powder, and copper-coated graphite powder, a vibratory mixing process is performed. During this process, zirconia balls are added, followed by the addition of 0.12wt% vacuum pump oil. The material-to-ball ratio is 3:1, the diameter of the zirconia balls is 5mm to 6mm, the mixing frequency is 50Hz, and the mixing time is 3 hours. A mixed powder was obtained; then, high-energy ball milling was used to mix the powder. During the high-energy ball milling process, anhydrous ethanol and zirconia balls with a diameter of 0.8 mm to 1 mm were added to the mixed powder at a mass fraction of 0.1 wt% to 0.5 wt% of the mixed powder. The protective gas argon was introduced, and high-energy ball milling was carried out for 4 h to 8 h under the protective gas. The material-to-ball ratio was 1:5 to obtain ball-milled powder. The ball-milled powder was dried at 50 °C for 6 h to obtain Cu-based composite powder.

[0024] In this invention, Cu-based composite powder is prepared by vibration mixing and high-energy ball milling. The advantages are that vibration mixing ensures uniform macroscopic distribution, and high-energy ball milling achieves microscopic uniformity. At the same time, it can also improve the powder morphology (tending to near spherical shape), improve flowability and powder feeding stability, thus laying the foundation for the preparation of high-quality composite coatings.

[0025] Vibratory mixing utilizes low-energy physical mixing to initially disperse the powder components, allowing different types of particles to come into contact and preventing severe agglomeration at the beginning of high-energy ball milling. Adding vacuum pump oil during the mixing process prevents metal powders from cold-welding and adhering to the zirconia balls or bottle walls, forming a very thin lubricating film on the surface. This reduces friction and cold-welding tendencies between powders and between powder and the balls. The zirconia balls used have a particle size of 5mm–6mm. The relatively large diameter of the zirconia balls, under vibration conditions, results in a relatively gentle force, achieving initial uniform dispersion and facilitating macroscopic uniform distribution.

[0026] High-energy ball milling utilizes mechanical impact and friction to subject powders to intense plastic deformation, crushing, and cold welding. This not only further homogenizes the powder but also alters its morphology. Through plastic deformation and crushing, the powder gradually becomes nearly spherical. Near-spherical powder exhibits better flowability and conveying stability in synchronous powder feeding laser cladding, reducing powder clogging issues. The zirconia balls used have a particle size of 0.8mm–1mm, which more effectively transmits impact and shear forces, causing intense plastic deformation and crushing of the powder, promoting a near-spherical shape. This avoids the problem of uneven crushing and the generation of coarse, blocky fragments during high-energy ball milling, which negatively impacts powder flowability.

[0027] In one specific embodiment, during the high-energy ball milling process, the high-energy ball milling is carried out in an alternating manner of forward rotation + stop + reverse rotation for 4h to 8h, wherein the forward rotation time is 30min, the stop time is 12min, and the reverse rotation time is 30min.

[0028] In this invention, the high-energy ball mill operates by alternating between forward rotation, stop, and reverse rotation. On the one hand, this avoids the relatively stable movement trajectory of the zirconia balls and powder under single forward rotation, which can easily create "dead zones" and lead to insufficient mixing of some powders. By reversing the rotation, the flow trajectory of the balls and powder is disrupted, and the dead zones are continuously "activated," thereby achieving more thorough mixing. On the other hand, the "stop" operation allows for brief heat dissipation, preventing excessively high temperatures and avoiding the rapid rise in the temperature of the ball mill jar caused by continuous high-speed forward rotation, which could lead to powder agglomeration.

[0029] S2. Using a copper alloy as a substrate, Cu-based composite powder is clad onto the surface of the copper alloy by laser cladding to obtain a copper-based composite material coating.

[0030] When designing the cladding powder composition, copper-based composite materials can retain the high conductivity of the coating to the maximum extent. Simultaneously, by selecting appropriate reinforcing phase materials, the coating can maintain excellent tribological properties even under current-carrying conditions. This invention uses chromium diboride and graphite as reinforcing phases. Chromium diboride (CrB2) possesses excellent chemical stability, good corrosion resistance, high melting point, and high hardness, making it an ideal reinforcing phase material. Graphite, with its layered structure and low shear strength, effectively reduces friction at the interface. During laser cladding, high-energy laser beam irradiation forms a localized high-temperature molten pool, creating a metallurgical bond between the coating and the substrate with high bonding strength. The hard phase of chromium diboride, distributed within the Cu matrix, acts as a "skeleton," effectively hindering plastic flow on the wear surface and improving wear resistance. The self-lubricating phase of graphite easily forms a lubricating film on the surface during wear, reducing the coefficient of friction and preventing adhesive wear, thereby improving the current-carrying tribological properties of the composite coating.

[0031] In this invention, QCr0.5 copper alloy is used as the substrate. Before laser cladding, the surface of QCr0.5 copper alloy is subjected to oxide layer removal and blackening treatment. The oxide layer removal is carried out by sandblasting the copper alloy plate with white corundum, followed by blackening treatment after drying. The blackening treatment involves placing the sandblasted copper alloy plate in carbon ink for blackening for 4 to 5 minutes, and then holding it at 120°C for 10 minutes.

[0032] In this invention, before laser cladding, the copper alloy plate is preheated to 50°C to 80°C using a heated bed device.

[0033] In this invention, during the laser cladding process, argon gas is used as both the protective gas and the powder feeding gas. The flow rate of the protective gas is 4.2 L / min to 4.7 L / min, and the flow rate of the powder feeding gas is 3.6 L / min to 3.7 L / min. The overlap rate is 44%, the defocusing amount is 8.3 mm, the scanning speed is 778 mm / min, and the laser power is 1780 W. During the laser cladding process, repetitive laser cladding is used until the copper-based composite material coating thickness reaches 2.1 mm to 2.3 mm.

[0034] In practical applications, there are various methods for adding materials in laser cladding. Through continuous optimization and improvement, the commonly used powder addition methods in the laser cladding process for copper alloy surfaces are the pre-positioning method and the synchronous powder feeding method. The synchronous powder feeding method adopted in this invention can be divided into coaxial powder feeding and lateral powder feeding methods depending on the setting of the powder feeding nozzle. Under the action of the airflow of the powder feeder, the cladding powder is transported to the laser spot irradiation area, and then melts and cools together with the substrate to form a cladding layer. In the synchronous powder feeding method, the cladding powder is heated by the laser just after leaving the nozzle before entering the molten pool, thus making more efficient use of laser energy and reducing the melting amount of the substrate of the processed part, thereby reducing the dilution rate and improving the quality of the cladding layer. The powder feeding amount can be precisely controlled, the process is simple, easy to automate, and has high working efficiency, making it suitable for surface processing of medium to large batches of parts.

[0035] The following specific examples will provide further explanation.

[0036] Example 1 A laser cladding method for preparing a copper-based composite material coating on a copper alloy substrate includes the following steps: S1. Weigh 2.33g of chromium diboride powder (CrB2 powder) and 131.06g of copper powder (Cu powder), respectively. The particle size of CrB2 powder is 1μm~5μm, and the particle size of Cu powder is 49μm±1μm. Place the powder and zirconia balls together into the mixing bottle of a three-dimensional vibrating powder mixer. The diameter of the zirconia balls is 5mm±1mm, and the powder to zirconia ball ratio is 3:1. Add 0.12wt% vacuum pump oil and perform vibration mixing. The frequency of the powder mixer is 50Hz, and the mixing time is 2h to obtain mixed powder.

[0037] S2. Place the mixed powder and zirconia balls in a ball mill jar. The ratio of the mixed powder to the zirconia balls is 1:5. The diameter of the zirconia balls is 0.9 mm ± 0.1 mm. Add 0.1 wt% anhydrous ethanol and purge with argon as a protective gas. Perform high-energy ball milling using a planetary ball mill at a speed of 150 r / min. The ball mill is operated in a forward + stop + reverse alternating manner for 8 hours. First, rotate forward for 30 minutes, stop for 12 minutes, and then rotate in reverse for 30 minutes. After the ball milling is completed, the ball milled powder is obtained. Then, the ball milled powder is placed in a vacuum oven at a temperature of 50℃ for 6 hours to dry, resulting in Cu-based composite powder. The Cu-based composite powder, by volume percentage, has CrB2 of 3 vol.% and the remainder being Cu, totaling 100%.

[0038] S3. The surface of QCr0.5 copper alloy is subjected to sandblasting and blackening treatment. Specifically, white corundum is placed in a sandblasting machine to remove the oxide layer from the copper alloy plate. Then, it is placed in a beaker, alcohol is poured into the beaker, and it is placed in an ultrasonic cleaner for 10 minutes to remove surface grit. The cleaned copper alloy plate is then immersed in 80% carbon ink for 10 minutes for blackening treatment. Finally, the copper alloy plate is placed in a 120℃ drying oven for 10 minutes to dry, obtaining the treated copper alloy plate.

[0039] S4. Using the treated copper alloy plate as the substrate, the copper alloy is preheated to 80°C using a heated bed device. Cu-based composite powder is used as the laser cladding powder, and argon is used as the protective gas and powder feeding gas with gas flow rates of 4.7 L / min and 3.6 L / min, respectively. Laser cladding is performed with a defocusing amount of 8.3 mm, a scanning speed of 778 mm / min, and a laser power of 1780 W. Each layer on the copper alloy substrate is clad using a reciprocating laser cladding method, and a total of 7 layers are clad to obtain a 2.1 mm thick CrB2 / Cu copper-based composite material coating, which is the copper-based composite material coating.

[0040] Example 2 A laser cladding method for preparing a copper-based composite material coating on a copper alloy substrate includes the following steps: S1. Weigh out 0.34g of copper-coated graphite powder, 0.78g of CrB2 powder, and 132.92g of Cu powder, respectively. The particle size of the copper-coated graphite powder is 49μm±1μm, the particle size of the CrB2 powder is 1μm~5μm, and the particle size of the Cu powder is 49μm±1μm. Place the powder and zirconia balls together into the mixing bottle of a three-dimensional vibrating powder mixer. The diameter of the zirconia balls is 5mm±1mm, and the powder-to-zirconia ball ratio is 3:1. Add 0.12wt% vacuum pump oil and perform vibration mixing. The frequency of the powder mixer is 50Hz, and the mixing time is 2h to obtain mixed powder.

[0041] S2. Place the mixed powder and zirconia balls in a ball mill jar. The ratio of mixed powder to zirconia balls is 1:5. The diameter of the zirconia balls is 0.9 mm ± 0.1 mm. Add 0.1 wt% anhydrous ethanol and purge with argon as a protective gas. Use a planetary ball mill to ball mill at a speed of 150 r / min. The ball mill is operated in a high-energy ball milling mode of alternating forward rotation, stop, and reverse rotation for 8 hours. First, rotate forward for 30 minutes, stop for 12 minutes, and then rotate in reverse for 30 minutes. After ball milling, the ball milled powder is obtained. Then, the ball milled powder is placed in a vacuum oven at a temperature of 50℃ for 6 hours to dry, obtaining Cu-based composite powder. The Cu-based composite powder, by volume percentage, consists of 0.5 vol.% graphite, 1 vol.% CrB2, and the balance Cu, totaling 100%.

[0042] S3. The surface of QCr0.5 copper alloy is subjected to sandblasting and blackening treatment. Specifically, white corundum is placed in a sandblasting machine to remove the oxide layer from the copper alloy plate. Then, it is placed in a beaker, alcohol is poured into the beaker, and it is placed in an ultrasonic cleaner for 10 minutes to remove surface grit. The cleaned copper alloy plate is then immersed in 80% carbon ink for 10 minutes for blackening treatment. Finally, the copper alloy plate is placed in a 120℃ drying oven for 10 minutes to dry, obtaining the treated copper alloy plate.

[0043] S4. Using the treated copper alloy plate as the substrate, the copper alloy was preheated to 80℃ using a heated bed apparatus. Cu-based composite powder was used as the laser cladding powder, and argon was used as the protective gas and powder feeding gas, with gas flow rates of 4.7 L / min and 3.6 L / min, respectively. Laser cladding was performed, with a defocusing amount of 8.3 mm, a scanning speed of 778 mm / min, and a laser power of 1780 W. Each layer on the copper alloy substrate was clad using a reciprocating laser cladding method, for a total of 7 layers, resulting in a 2.1 mm thick (C+CrB2) / Cu copper-based composite material coating, which is the copper-based composite material coating. Its macroscopic morphology is as follows. Figure 1 As shown.

[0044] Example 3 A laser cladding method for preparing a copper-based composite material coating on a copper alloy substrate includes the following steps: S1. Weigh out 0.34g of copper-coated graphite powder, 2.33g of CrB2 powder, and 130.22g of Cu powder, respectively. The particle size of the copper-coated graphite powder is 49μm±1μm, the particle size of the CrB2 powder is 1μm~5μm, and the particle size of the Cu powder is 49μm±1μm. Place the powder and zirconia balls together into the mixing bottle of a three-dimensional vibrating powder mixer. The diameter of the balls is 5mm±1mm, and the ratio of powder to zirconia balls is 3:1. Add 0.12wt% vacuum pump oil and perform vibration mixing. The frequency of the powder mixer is 50Hz, and the mixing time is 2h to obtain mixed powder.

[0045] S2. Place the mixed powder and zirconia balls in a ball mill jar. The ratio of mixed powder to zirconia balls is 1:5. The diameter of the zirconia balls is 0.9 mm ± 0.1 mm. Add 0.1 wt% anhydrous ethanol and purge with argon as a protective gas. Perform high-energy ball milling using a planetary ball mill at a speed of 150 r / min. The ball mill is operated in a forward + stop + reverse alternating manner for 8 hours. First, rotate forward for 30 minutes, stop for 12 minutes, and then rotate in reverse for 30 minutes. After ball milling, the ball milled powder is obtained. Then, place the ball milled powder in a vacuum oven at a temperature of 50℃ for 6 hours to dry, obtaining Cu-based composite powder. The Cu-based composite powder, by volume percentage, consists of 0.5 vol.% graphite, 3 vol.% chromium diboride, and the balance Cu, totaling 100%.

[0046] S3. The surface of QCr0.5 copper alloy is subjected to sandblasting and blackening treatment. Specifically, white corundum is placed in a sandblasting machine to remove the oxide layer from the copper alloy plate. Then, it is placed in a beaker, alcohol is poured into the beaker, and it is placed in an ultrasonic cleaner for 10 minutes to remove surface grit. The cleaned copper alloy plate is then immersed in 80% carbon ink for 10 minutes for blackening treatment. Finally, the copper alloy plate is placed in a 120℃ drying oven for 10 minutes to dry, obtaining the treated copper alloy plate.

[0047] S4. Using the treated copper alloy plate as the substrate, the copper alloy is preheated to 80°C using a heated bed device. Cu-based composite powder is used as the laser cladding powder, and argon is used as the protective gas and powder feeding gas with gas flow rates of 4.7 L / min and 3.6 L / min, respectively. Laser cladding is performed with a defocusing amount of 8.3 mm, a scanning speed of 778 mm / min, and a laser power of 1780 W. Each layer on the copper alloy substrate is clad using a reciprocating laser cladding method, and a total of 7 layers are clad to obtain a 2.1 mm thick (C+CrB2) / Cu copper-based composite material coating, which is the copper-based composite material coating.

[0048] Example 4 A laser cladding method for preparing a copper-based composite material coating on a copper alloy substrate includes the following steps: S1. Weigh out 0.34g of copper-coated graphite powder, 3.89g of CrB2 powder, and 127.51g of Cu powder, respectively. The particle size of the copper-coated graphite powder is 49μm±1μm, the particle size of the CrB2 powder is 1μm~5μm, and the particle size of the Cu powder is 49μm±1μm. Place the powder and zirconia balls together into the mixing bottle of a three-dimensional vibrating powder mixer. The diameter of the zirconia balls is 5mm±1mm, and the powder-to-zirconia ball ratio is 3:1. Add 0.12wt% vacuum pump oil and perform vibration mixing. The frequency of the powder mixer is 50Hz, and the mixing time is 2h to obtain mixed powder.

[0049] S2. Place the mixed powder and zirconia balls in a ball mill jar. The ratio of mixed powder to zirconia balls is 1:5. The diameter of the zirconia balls is 0.9 mm ± 0.1 mm. Add 0.1 wt% anhydrous ethanol and purge with argon as a protective gas. Perform high-energy ball milling using a planetary ball mill at a speed of 150 r / min. The ball mill is operated in a forward + stop + reverse alternating manner for 8 hours. First, rotate forward for 30 minutes, stop for 12 minutes, and then rotate in reverse for 30 minutes. After ball milling, the ball milled powder is obtained. Then, place the ball milled powder in a vacuum oven at a temperature of 50℃ for 6 hours to dry, obtaining Cu-based composite powder. The Cu-based composite powder, by volume percentage, consists of 0.5 vol.% graphite, 5 vol.% chromium diboride, and the balance Cu, totaling 100%.

[0050] S3. The surface of QCr0.5 copper alloy is subjected to sandblasting and blackening treatment. Specifically, white corundum is placed in a sandblasting machine to remove the oxide layer from the copper alloy plate. Then, it is placed in a beaker, alcohol is poured into the beaker, and it is placed in an ultrasonic cleaner for 10 minutes to remove surface grit. The cleaned copper alloy plate is then immersed in 80% carbon ink for 10 minutes for blackening treatment. Finally, the copper alloy plate is placed in a 120℃ drying oven for 10 minutes to dry, obtaining the treated copper alloy plate.

[0051] S4. Using the treated copper alloy plate as the substrate, the copper alloy is preheated to 80°C using a heated bed device. Cu-based composite powder is used as the laser cladding powder, and argon is used as the protective gas and powder feeding gas with gas flow rates of 4.7 L / min and 3.6 L / min, respectively. Laser cladding is performed with a defocusing amount of 8.3 mm, a scanning speed of 778 mm / min, and a laser power of 1780 W. Each layer on the copper alloy substrate is clad using a reciprocating laser cladding method, and a total of 7 layers are clad to obtain a 2.1 mm thick (C+CrB2) / Cu copper-based composite material coating, which is the copper-based composite material coating.

[0052] The laser cladding coatings prepared in Examples 1 to 4 were tested, and the results are shown in Table 1: Table 1. Test results of laser cladding coatings prepared in Examples 1 to 4 As shown in Table 1, the conductivity of the composite coatings prepared in Examples 1 to 4 is slightly lower than that of the comparative material QCr0.5 copper alloy. However, the test results all show that their conductivity is above 60% IACS, which meets the basic requirements for conductivity of electrical contact materials. Furthermore, the volumetric wear rate and average friction coefficient of the composite coatings under current-carrying friction conditions are significantly lower than those of QCr0.5 copper alloy, indicating that the comprehensive performance of the composite coatings prepared in Examples 1 to 4 is significantly better than that of QCr0.5 copper alloy. In summary, the composite coating prepared by this invention maintains good conductivity while also possessing the comprehensive performance advantages of wear resistance and arc erosion resistance brought by the reinforcing phase. By introducing a reasonable proportion of reinforcing phase into the copper matrix, this invention overcomes the defect of traditional composite coatings sacrificing conductivity due to the increased content of reinforcing phase, while ensuring the application potential of the coating under current-carrying friction conditions. Therefore, the composite coating prepared by this invention not only meets the application standards of electrical contact materials in terms of conductivity, but also achieves a balance between conductivity and wear resistance through composite design. It can not only improve the performance of copper alloy surfaces, but also provide a more economical solution for the repair of damaged moving electrical contact components.

[0053] Figure 2These are 5000x magnification microstructure images of the copper-based composite material coatings prepared in Examples 1 to 4 of this invention. Figure 2 (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4. Figure 2 (a) shows the microstructure of the composite coating prepared in Example 1, with the reinforcing phase CrB2 uniformly distributed on the Cu matrix. During the current-carrying friction process, frictional heat and Joule heat cause the temperature of the friction surface to rise rapidly. Due to its low hardness, QCr0.5 alloy is prone to softening at high temperatures, resulting in severe plastic deformation and adhesive peeling. In contrast, the CrB2 particles introduced into the composite coating of this example have high hardness and excellent chemical stability, which can improve the hardness of the coating at high temperatures and reduce adhesive wear, thereby resulting in a lower coefficient of friction and volumetric wear rate than QCr0.5 alloy.

[0054] Figure 2 (b) shows the microstructure of the composite coating prepared in Example 2, with C and CrB2 uniformly distributed on the Cu matrix. Compared with Example 1, the composite coating prepared in Example 2 has a lower content of reinforcing phase and a reduced "skeleton support" in the composite coating, thus slightly increasing the volumetric wear rate; however, the addition of graphite forms a lubricating film on the wear surface, thereby slightly reducing the coefficient of friction.

[0055] Figure 2 In Figure (c), the microstructure of the composite coating prepared in Example 3 is shown. The content of the reinforcing phase CrB2 is increased to 3 vol.%, and C and CrB2 are still uniformly distributed in the Cu matrix. The combined effect of graphite and CrB2 particles in the composite coating inhibits adhesive wear behavior, which is the reason for the significant reduction in both the friction coefficient and volumetric wear rate.

[0056] Figure 2 (d) shows the microstructure of the composite coating prepared in Example 4. With the reinforcing phase CrB2 content increased to 5 vol.%, the volumetric wear rate of the composite coating prepared in Example 4 was significantly higher than that of other examples. This is mainly because excessive CrB2 content causes a reduction in the interparticle spacing in the coating, enhancing interaction and resulting in a non-uniform distribution of reinforcing particles, including large, irregularly sized particles. This non-uniform particle distribution easily becomes a stress concentration zone during high-current wear, making it more prone to lubricant film rupture or peeling under high-load cycles, thus affecting the stability of the friction interface. However, the overall performance of the composite coating prepared in Example 4 is still superior to that of the QCr0.5 copper alloy.

[0057] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0058] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A laser cladding method for preparing a copper-based composite material coating on a copper alloy substrate, characterized in that, Includes the following steps: Using chromium diboride and graphite as reinforcing phases, and mixing them with Cu powder, Cu-based composite powder was prepared by sequentially vibratory mixing and ball milling. The Cu-based composite powder, by volume percentage, consisted of 0 vol.%–1 vol.% graphite, 1 vol.%–5 vol.% chromium diboride, and the balance being Cu, totaling 100%. Using a copper alloy as a substrate, Cu-based composite powder is clad onto the surface of the copper alloy by laser cladding to obtain a copper-based composite material coating.

2. The laser cladding method for preparing a copper-based composite material coating on a copper alloy substrate according to claim 1, characterized in that, During the laser cladding process, the thickness of the copper-based composite material coating is 2.1 mm to 2.3 mm by repeated laser cladding.

3. The laser cladding method for preparing a copper-based composite material coating on a copper alloy substrate according to claim 1, characterized in that, During the laser cladding process, argon gas is used as both the protective gas and the powder feeding gas. The flow rate of the protective gas is 4.2 L / min to 4.7 L / min, the flow rate of the powder feeding gas is 3.6 L / min to 3.7 L / min, the overlap rate is 44%, the defocusing amount is 8.3 mm, the scanning speed is 778 mm / min, and the laser power is 1780 W.

4. The laser cladding method for preparing a copper-based composite material coating on a copper alloy substrate according to claim 1, characterized in that, The preparation method of Cu-based composite powder includes the following steps: mixing copper powder, chromium diboride powder and copper-coated graphite powder, and then sequentially using vibration mixing and ball milling under protective gas to obtain Cu-based composite powder.

5. The laser cladding method for preparing a copper-based composite material coating on a copper alloy substrate according to claim 4, characterized in that, The particle size of copper powder is 48μm to 50μm, the particle size of chromium diboride powder is 1μm to 5μm, and the particle size of copper-coated graphite powder is 48μm to 50μm.

6. The laser cladding method for preparing a copper-based composite material coating on a copper alloy substrate according to claim 4, characterized in that, During the vibration mixing process, the material-to-ball ratio is 3:1, the mixing frequency is 50Hz, and the mixing time is 3h.

7. The laser cladding method for preparing a copper-based composite material coating on a copper alloy substrate according to claim 4, characterized in that, During the ball milling process, anhydrous ethanol is added to the mixture at a concentration of 0.1 wt% to 0.5 wt% of the mixture. The ball milling is carried out under a protective gas for 4 to 8 hours, with a material-to-ball ratio of 1:

5.

8. The laser cladding method for preparing a copper-based composite material coating on a copper alloy substrate according to claim 4, characterized in that, During the ball milling process, the ball milling is carried out in a way that alternates between forward rotation, stop, and reverse rotation for 4 to 8 hours, with the forward rotation time being 30 minutes, the stop time being 12 minutes, and the reverse rotation time being 30 minutes.

9. The laser cladding method for preparing a copper-based composite material coating on a copper alloy substrate according to claim 1, characterized in that, Before laser cladding, the copper alloy plate is subjected to sandblasting and blackening treatment. The blackening treatment involves placing the sandblasted copper alloy plate in carbon ink for 4 to 5 minutes and then holding it at 120°C for 10 minutes.

10. The laser cladding method for preparing a copper-based composite material coating on a copper alloy substrate according to claim 1, characterized in that, Before laser cladding, the copper alloy plate is preheated to 50℃~80℃.

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