Preparation method and application of pure copper coating

Abstract

The invention provides a preparation method and application of a pure copper coating, and relates to the field of surface functional coatings, and the preparation method comprises the following steps: preparing pure copper powder, and carrying out sand blasting treatment on the surface of an aluminum alloy substrate; the aluminum alloy substrate is fixed in a closed cold spraying chamber, and pure copper powder is loaded into helium cold spraying equipment in the closed cold spraying chamber; vacuumizing until the pressure in the closed cold spraying chamber is lower than a preset pressure threshold value and the oxygen content in the chamber is lower than a preset value; helium in a buffer tank is adopted as main gas and powder feeding gas, and a pure copper coating is formed on the surface of the aluminum alloy substrate through spraying of helium cold spraying equipment; and the helium circulation system is synchronously started to recover helium in the cavity, and the helium is compressed into the buffer tank after being filtered and cooled, so that helium circulation is realized. The method adopts the circulating helium atmosphere to avoid the problem that the impurity content of the coating is increased due to high-temperature oxidation of the copper coating, the oxygen content of the coating is remarkably reduced, and the particle interface bonding is improved, so that the electric conduction and heat conduction performance of the pure copper coating is improved, and the helium use cost is reduced.

Description

Technical Field

[0001] This invention relates to a method for preparing a pure copper coating and its application, belonging to the field of material performance testing technology in complex environments. Background Technology

[0002] With the rapid development of modern electronic and electrical equipment towards high performance, miniaturization, and lightweight design, efficient thermal management and reliable electrical connections have become bottlenecks restricting technological progress. In the field of thermal conductivity, battery pack trays for new energy vehicles require highly efficient thermally conductive coatings to ensure temperature uniformity between cells, prevent thermal runaway, and improve fast-charging performance. Heat sinks for high-power lasers require coatings that can rapidly dissipate concentrated high heat flux densities to ensure stable laser output and lifespan. In electronic packaging, low thermal resistance thermal pathways are needed between chips and heat sinks to cope with continuously increasing power consumption. Furthermore, heat sinks for power equipment such as outdoor transformers also rely on long-lasting, weather-resistant thermally conductive coatings to maintain their operating efficiency and reliability. In the field of electrical conductivity, from electrode copper coatings to high-voltage switch contact surfaces, stringent requirements are placed on the conductivity, bonding strength, and arc resistance of the coatings.

[0003] Cold spraying technology, due to its low spraying temperature and high coating density, is considered an ideal process for preparing high thermal / electrical conductivity coatings. Currently, this technology mainly involves spraying pure copper or copper composite powder onto aluminum alloy substrates to construct functional coatings. To improve coating density and interparticle bonding strength, higher gas pressures and temperatures are often used in the process. However, when deposition is carried out under normal atmospheric conditions, the increased gas temperature exacerbates the oxidation of the deposited copper surface, leading to the formation of oxide impurities within the coating and weakening of the particle interface bonding. This significantly reduces the thermal and electrical conductivity of the coating, making it difficult to meet the actual needs of high-end applications. To improve powder deposition efficiency and coating metallurgical quality, some researchers have proposed using lighter helium instead of commonly used nitrogen or argon as the accelerating gas to achieve better powder particle acceleration. However, using helium as the accelerating gas significantly increases costs (20 times higher than nitrogen), severely limiting the application of helium in the field of cold spraying. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing and applying a pure copper coating. By implementing helium cold spraying technology in a circulating helium atmosphere, the technical problems of surface oxidation of pure copper coatings, insufficient particle deformation leading to a decrease in the electrical and thermal conductivity of the coating, and high cost of helium usage are solved.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution: In a first aspect, the present invention provides a method for preparing a pure copper coating, comprising: preparing pure copper powder; cleaning and sandblasting the surface of an aluminum alloy substrate; fixing the sandblasted aluminum alloy substrate in a sealed cold spraying chamber, and loading the pure copper powder into a helium cold spraying device within the sealed cold spraying chamber; evacuating the sealed cold spraying chamber until the pressure inside the chamber is lower than a preset pressure threshold and the oxygen content inside the chamber is lower than a preset value; using helium in a buffer tank as the main gas and powder feeding gas, and spraying and depositing the pure copper powder onto the surface of the aluminum alloy substrate through the helium cold spraying device to form a pure copper coating; simultaneously starting a helium circulation system to recover helium in the sealed cold spraying chamber, filtering and cooling the helium, and then compressing the helium into the buffer tank to achieve helium circulation.

[0006] Furthermore, the pure copper powder has a spherical or near-spherical morphology, an oxygen content of less than 200 ppm, and a particle size of 10-75 μm.

[0007] Furthermore, spherical or near-spherical pure copper powder is prepared using a gas atomization process, wherein the medium for the gas atomization process is high-purity argon gas.

[0008] Furthermore, during the helium cold spraying process, the pressure inside the sealed cold spraying chamber is maintained at 3-5 bar.

[0009] Furthermore, when the helium cold spraying equipment performs spraying, the powder feeding gas pressure is 1.8-4.5 MPa; the main gas pressure is 1.5-4.0 MPa; and the main gas temperature is 300-800℃.

[0010] Furthermore, it also includes: after the pure copper coating is deposited, the pure copper coating and the aluminum alloy substrate are subjected to low-temperature annealing treatment at 150-250°C.

[0011] Furthermore, the low-temperature annealing treatment is carried out in a vacuum furnace or under a protective atmosphere, and the low-temperature annealing time is 0.5-4 hours. After the annealing treatment, furnace cooling is adopted.

[0012] Furthermore, the aluminum alloy substrate is a 1-series, 2-series, 6-series, or 7-series aluminum alloy.

[0013] Secondly, the present invention provides an application of the method for preparing the pure copper coating described in the first aspect in reducing the oxygen content of the pure copper coating and improving the electrical and thermal conductivity of the pure copper coating.

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The method for preparing a pure copper coating provided by this invention involves solid-state deposition in a circulating helium atmosphere to prepare a pure copper coating on an aluminum alloy substrate. The cold spray deposition process uses high gas pressure and temperature, and the use of a circulating helium atmosphere avoids the problem of increased impurity content in the coating due to high-temperature oxidation of the copper coating during conventional cold spray deposition processes, significantly reducing the oxygen content of the coating and thus greatly improving the electrical and thermal conductivity of the pure copper coating. At the same time, the helium recovery and recycling can significantly reduce the cost of helium usage. This invention uses low-oxygen pure copper powder prepared by high-purity argon atomization as the raw material, and performs low-temperature annealing treatment after coating deposition. Recovery and recrystallization can be achieved in a short time at low temperature, reducing dislocation density and improving the electrical and thermal conductivity of the coating. Attached Figure Description

[0015] Figure 1 This is a flowchart of the method for preparing the pure copper coating in Example 1 of the present invention; Figure 2 This is a schematic diagram of high-purity argon gas atomizing pure copper powder used in Embodiment 1 of the present invention; Figure 3 The metallographic images are generated by metallographic analysis of the copper coatings obtained in Example 2 and the comparative example of the present invention. Figure 4 These are BSE images of the copper coatings obtained in Embodiment 2 and the comparative embodiment of the present invention; Figure 5 This is a physical image of the heat sink coating in Embodiment 3 of the present invention. Detailed Implementation

[0016] The terms “comprising” and “having”, and any variations thereof, in the specification, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or apparatus.

[0017] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0018] Example 1 This embodiment provides a method for preparing a pure copper coating, which is used to prepare a pure copper coating with low oxygen content and high electrical and thermal conductivity, such as... Figure 1 As shown, the method includes: Step 1: Prepare pure copper powder.

[0019] Specifically, the morphology of pure copper powder can be... Figure 2 The sphere shown can also be a near-spherical shape.

[0020] In this embodiment, a gas atomization process is used for preparation. Figure 1 The pure copper spherical powder shown was argon-atomized at a pressure of 3.0 MPa. The powder was sieved and stored under an argon or nitrogen atmosphere, with a particle size range of 10-75 μm. 50 The powder with a diameter of 34 μm was used as the raw material for cold spraying. The initial oxygen and nitrogen content of the powder was detected by a nitrogen-oxygen analyzer and was 180 ppm and 42 ppm, respectively.

[0021] Step 2: Clean and sandblast the surface of the selected aluminum alloy substrate.

[0022] Specifically, aluminum alloy substrates are made from 1-series, 2-series, 6-series, or 7-series aluminum alloys.

[0023] In this embodiment, a 6061 aluminum alloy substrate with dimensions of 100×100×5 mm is selected, and the surface roughness of the substrate after sandblasting is not less than 15μm.

[0024] Step 3: Fix the sandblasted aluminum alloy substrate in a sealed cold spraying chamber, and load pure copper powder into the helium cold spraying equipment inside the sealed cold spraying chamber.

[0025] The method for preparing the pure copper coating provided in this embodiment is carried out in a closed cold spraying chamber. The closed cold spraying chamber is equipped with a spraying bracket and a helium cold spraying device. After sandblasting, the 6061 aluminum alloy substrate is fixed on the spraying bracket, and the pure copper spherical powder prepared in step 1 is loaded into the helium cold spraying device in the closed cold spraying chamber, specifically into the powder feeder.

[0026] It should be noted that the helium cold spraying equipment used in this embodiment refers to a high-pressure cold spraying equipment that uses helium as the main gas and powder feeding gas, including: a high-pressure helium gas source, a gas heater, a powder feeder, and a Laval spray gun. The high-pressure helium gas source is provided by a buffer tank outside the sealed cold spraying chamber, and the detailed features of the gas heater, powder feeder, and Laval spray gun are the same as those in the prior art, and will not be described in detail here.

[0027] Step 4: Evacuate the sealed cold spraying chamber until the pressure inside the chamber is below 200 Pa and the oxygen content is below 500 ppm.

[0028] Step 5: Using helium in the buffer tank as the main gas and powder feeding gas, pure copper spherical powder is sprayed and deposited onto the surface of the aluminum alloy substrate through a helium cold spraying equipment to form a pure copper coating; at the same time, the helium circulation system is started to recover the helium in the sealed cold spraying chamber, and after filtration and cooling, the helium is compressed into the buffer tank to realize helium circulation.

[0029] Similar to existing cold spray equipment, the powder feeder uses the pressure of the powder feeding gas to send pure copper spherical powder into the Laval spray gun. The main gas inside the Laval spray gun, which is accelerated and heated, also uses the main gas pressure to spray the pure copper spherical powder onto the surface of the aluminum alloy substrate.

[0030] In this embodiment, the main gas pressure is 2.3 MPa, the powder feeding gas pressure is 2.6 MPa, and the main gas temperature is 600℃. The spraying distance is 30 mm, the spray gun moving speed is 100 mm / s, and the spraying angle is 90°, ultimately depositing a 2 mm thick pure copper coating on the 6061 aluminum alloy substrate.

[0031] Step 6: Perform low-temperature annealing on the deposited coating and substrate in a vacuum or protective atmosphere, and then cool them in the furnace.

[0032] Low-temperature annealing is a commonly used method for treating cold-sprayed copper coatings. It enables recovery and recrystallization in a short time at low temperatures, reducing dislocation density and improving the electrical and thermal conductivity of the coating.

[0033] In this embodiment, the annealing temperature is 200°C and the annealing time is 2 hours to reduce the impact on the microstructure and properties of the aluminum alloy matrix.

[0034] This embodiment uses high-purity argon gas to atomize pure copper powder as the initial raw material for cold spraying. A pure copper coating is deposited through solid-state cold spraying in a circulating helium atmosphere. By adjusting the pressure and temperature of the main gas, the pure copper powder particles are fully deformed, resulting in a highly dense pure copper coating. The entire cold spraying deposition process takes place in a helium atmosphere, isolating it from air and avoiding oxidation of the copper coating surface caused by high-temperature gases, thus reducing impurity content. Furthermore, the helium circulating cold spraying process significantly reduces helium usage costs.

[0035] Example 2 To highlight the effectiveness of the pure copper coating preparation method provided in Example 1, this example provides a comparative example of cold spray deposition under normal atmospheric conditions, and compares the performance of the copper coatings obtained in Example 1 and the comparative example from multiple aspects.

[0036] The difference between the comparative example and Example 1 is that, under normal atmospheric conditions, nitrogen is used as the main gas, the main gas pressure is 5.0 MPa, and the main gas temperature is 800℃. The other steps for preparing pure copper spherical powder, surface cleaning and sandblasting of the aluminum alloy substrate, and low-temperature annealing are exactly the same as in Example 1.

[0037] First, in this embodiment, metallographic analysis was performed on the copper coatings obtained in Example 1 and the comparative example, and image analysis software was used to statistically analyze the density of the copper coatings obtained in Example 1 and the comparative example.

[0038] Figure 3 Metallographic images of the copper coatings obtained in Example 1 and the comparative example are shown. In the figures, a is the metallographic image of the copper coating obtained in Example 1, and b is the metallographic image of the copper coating obtained in the comparative example. As can be seen from the figures, the copper coating obtained in Example 1 is dense and has no obvious porosity defects, while the copper coating obtained in the comparative example has micropore defects between the coating particles.

[0039] Density statistics show that the density of the copper coating obtained in Example 1 reaches 99.85%, while the density of the copper coating obtained in the comparative example is 99.64%.

[0040] Second, in this embodiment, the back-scattered electron (BSE) mode of scanning electron microscopy was used to observe the particle deformation and particle interface bonding of the copper coatings obtained in the two embodiments.

[0041] Figure 4 The BSE images of the copper coatings obtained in Example 1 and the comparative example are shown. In the figure, a is the BSE image of the copper coating in Example 1, and b is the BSE image of the copper coating in the comparative example. The comparison shows that the copper coating obtained in Example 1 has more complete particle deformation and good particle interface bonding, while the copper coating obtained in the comparative example has poor particle interface bonding and obvious gaps.

[0042] Third, the nitrogen and oxygen content of the copper coatings obtained in the two examples were tested according to ASTM E1019-24 and ASTM E1019-24 standards, respectively. The nitrogen and oxygen content of the copper coating in Example 1 was 32 ppm and 220 ppm, respectively, while the nitrogen and oxygen content of the copper coating in the comparative example was 82 ppm and 980 ppm, respectively.

[0043] Fourth, the conductivity of the copper coatings obtained in the two examples was tested using the GB / T 32791-2016 standard. The conductivity of the copper coating in Example 1 reached 98.8% IACS, while the conductivity of the copper coating in the comparative example was 93.2% IACS.

[0044] Fifth, the thermal conductivity and thermal diffusivity of the copper coatings obtained in the two examples at room temperature were tested according to GB / T 42919.4-2023 standard. The thermal conductivity of the copper coating in Example 1 was 364 W / (m·K), and the thermal diffusivity was 122 mm. 2 / s, while the thermal conductivity of the copper coating in the comparative embodiment is 335 W / (m·K) and the thermal diffusivity is 109 mm. 2 / s.

[0045] Sixth, the hardness of the copper coatings obtained in the two examples was tested according to ASTM-633 standard. The average hardness of the copper coating in Example 1 was 110 HV. 0.1 The average hardness of the copper coating in the comparative example was 84 HV. 0.1 .

[0046] The comparison results in the above six aspects all show that the method for preparing pure copper coating proposed in this application has obvious advantages. It can not only prepare pure copper coating with low oxygen and high density, but also improve the electrical and thermal conductivity of pure copper coating, as well as the coating hardness.

[0047] Example 3 This embodiment provides an application of the pure copper coating preparation method described in Embodiment 1 in reducing the oxygen content of the pure copper coating on the surface of a heat sink and improving the electrical and thermal conductivity of the pure copper coating on the surface of a heat sink.

[0048] In this embodiment, the heat sink measures 85×100×25 mm and is made of 6063 aluminum alloy. The preparation process of the surface coating of the heat sink includes: Step 1: Pure copper spherical powder was prepared using a high-purity argon atomization process at a pressure of 3.0 MPa. The atomized powder was then sieved and stored under an argon or nitrogen atmosphere, selecting a particle size range of 10-75 μm. 50 Pure copper powder with a diameter of 37 μm was used as the raw material for cold spraying. The oxygen and nitrogen contents of the initial pure copper powder were detected by a nitrogen and oxygen analyzer and were 182 ppm and 44 ppm, respectively.

[0049] Step 2: Use a sandblasting machine to sandblast the surface of the radiator. After sandblasting, the surface roughness of the radiator is 16μm.

[0050] Step 3: Solid-state cold spray deposition of pure copper coating is carried out in a circulating helium atmosphere as described in Example 1.

[0051] Specifically, both the main gas and the powder delivery gas were helium, with the main gas pressure set at 2.0 MPa, the powder delivery gas pressure at 2.3 MPa, and the main gas temperature at 550℃. The spraying distance was 35 mm, the spray gun moving speed was 80 mm / s, and the spraying angle was 90°. Finally, a 1.8 mm thick pure copper coating was deposited on the surface of the 6063 aluminum alloy heat sink.

[0052] Step 4: The deposited pure copper coating and the 6063 aluminum alloy substrate are subjected to low-temperature annealing in an argon atmosphere and cooled in the furnace. The annealing temperature is 220℃ and the annealing time is 2 hours.

[0053] Figure 5The prepared radiator coating is shown in the image. The conductivity of the radiator coating was tested according to GB / T 32791-2016 standard, and the conductivity reached 98.5% IACS. The thermal conductivity and thermal diffusivity of the radiator coating at room temperature were tested according to GB / T 42919.4-2023 standard, and the thermal conductivity was 359 W / (m·K), and the thermal diffusivity was 118 mm². 2 / s.

[0054] Compared with the prior art, the heat sink coating prepared in this embodiment has significantly improved the performance in terms of electrical conductivity, thermal conductivity and thermal conductivity, and further confirms the effectiveness of the method provided in this application through application examples.

[0055] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a pure copper coating, characterized in that, include: Preparation of pure copper powder; The surface of the aluminum alloy substrate is cleaned and sandblasted. The sandblasted aluminum alloy substrate is fixed in a sealed cold spraying chamber, and the pure copper powder is loaded into a helium cold spraying device in the sealed cold spraying chamber. The sealed cold spraying chamber is evacuated until the pressure inside the chamber is lower than the preset pressure threshold and the oxygen content inside the chamber is lower than the preset value. Helium gas in a buffer tank is used as the main gas and powder feeding gas. The pure copper powder is sprayed and deposited onto the surface of an aluminum alloy substrate using a helium cold spraying equipment to form a pure copper coating. The helium circulation system is started simultaneously to recover helium from the sealed cold spraying chamber. After filtration and cooling, the helium is compressed into the buffer tank to achieve helium circulation.

2. The method for preparing a pure copper coating according to claim 1, characterized in that, The pure copper powder has a spherical or near-spherical morphology, an oxygen content of less than 200 ppm, and a particle size of 10-75 μm.

3. The method for preparing a pure copper coating according to claim 2, characterized in that, Spherical or near-spherical pure copper powder is prepared using a gas atomization process, with high-purity argon gas as the atomization medium.

4. The method for preparing a pure copper coating according to claim 1, characterized in that, When the helium cold spraying equipment is used for spraying, the pressure in the sealed cold spraying chamber is maintained at 3-5 bar.

5. The method for preparing a pure copper coating according to claim 1, characterized in that, When the helium cold spraying equipment is used for spraying, the powder feeding gas pressure is 1.8-4.5 MPa; the main gas pressure is 1.5-4.0 MPa; and the main gas temperature is 300-800℃.

6. The method for preparing a pure copper coating according to claim 1, characterized in that, Also includes: After the pure copper coating is deposited, the pure copper coating and the aluminum alloy substrate are subjected to low-temperature annealing treatment at 150-250℃.

7. The method for preparing a pure copper coating according to claim 6, characterized in that, The low-temperature annealing process is carried out in a vacuum furnace or under a protective atmosphere, and the low-temperature annealing time is 0.5-4 hours. After annealing, furnace cooling is performed.

8. The method for preparing a pure copper coating according to claim 1, characterized in that, The aluminum alloy substrate is a 1-series, 2-series, 6-series, or 7-series aluminum alloy.

9. The application of the method for preparing a pure copper coating according to any one of claims 1-8 in reducing the oxygen content of the pure copper coating and improving its electrical and thermal conductivity.

Images