Method for preparing high-strength compact Cu-based coating through cold spraying

Abstract

The invention discloses a method for preparing a high-strength compact Cu-based coating through cold spraying, and relates to a method for preparing a Cu-based coating through cold spraying. The technical problems that the microstructure of an existing Cu-based coating prepared through cold spraying cannot be controlled, and the coating is low in bonding strength, poor in compactness and low in porosity are solved. According to the method, a cold spraying process is used, Cu-based metal powder is sprayed to the surface of a base body, and a magnetic field is used below the base body to assist and control the flying-spreading-stacking behavior of Cu-based coating particles, so that the coating particle beams are more concentrated, the spreading and stacking quality is better, the whole coating is compact, the porosity is reduced, and the coating quality is improved. And good bonding strength and wear resistance are achieved. According to the method, the Lorentz force of the pulsed magnetic field is used for restraining the particle trajectory, the Joule heating effect is used for increasing the spreading wetting characteristic, and electromagnetic oscillation is used for discharging stacked bubbles to reduce pores, so that various service performance of the Cu-based coating during cold spraying of the base body is comprehensively improved.

Description

Technical Field

[0001] The invention relates to a method for preparing a Cu-based coating by cold spraying. Background Art

[0002] Copper and copper alloy coatings are common wear-resistant materials and are often used in mechanical equipment for surface protection of equipment in extreme service environments such as aerospace and marine turbine blades, oilfield pipelines, and automotive electronic devices. Their excellent self-lubrication and friction resistance play a key role in the service process of parts. In order to make the copper-based coating retain its own characteristics while more conveniently adhering to the surface of mechanical parts, the cold spraying method is often used to prepare copper-based wear-resistant coatings. Compared with traditional preparation processes (thermal spraying, laser cladding, etc.), it can maintain the characteristics of the Cu-based material itself, including excellent self-lubrication and wear resistance, as well as excellent electrical conductivity and high corrosion resistance. However, compared with traditional methods, the cold spraying method for preparing Cu-based coatings cannot control the microstructure of the coating, and the coating has low bonding strength, poor density, and low porosity. Pulsed magnetic field assisted treatment can just make up for these shortcomings. Pulsed magnetic field acts on various metal hot forming processes through Lorentz force control, electromagnetic oscillation and Joule heating effect. It has a good effect on improving the quality of metal materials and enhancing the comprehensive properties of alloys. It is especially suitable for refining the material structure, reducing component segregation, promoting the formation of amorphous nanocrystalline structure and regulating internal stress structure during metal hot forming. Summary of the invention

[0003] The present invention aims to solve the technical problems that the microstructure of the existing cold sprayed Cu-based coating cannot be controlled, the coating has low bonding strength, poor density and low porosity, and provides a method for cold spraying to prepare a high-strength and dense Cu-based coating.

[0004] The method for preparing a high-strength and dense Cu-based coating by cold spraying of the present invention is carried out according to the following steps:

[0005] 1. Pre-treat the substrate;

[0006] 2. cold spraying the pretreated substrate under the action of an external magnetic field to obtain a Cu-based coating with a thickness of 300 μm to 500 μm;

[0007] The magnetic field device for applying an external magnetic field is located directly below the substrate.

[0008] The present invention uses a cold spraying process to spray Cu-based metal powder onto the surface of a substrate, and uses a magnetic field to assist under the substrate to control the flight-spreading-stacking behavior of the Cu-based coating particles, so that the coating particle beam is more concentrated, the spreading and stacking quality is better, the coating is dense as a whole, the porosity is reduced, and it has good bonding strength and wear resistance. The present invention utilizes the Lorentz force of the pulsed magnetic field to constrain particle trajectories, the Joule heat effect to increase the spreading and wetting characteristics, and the electromagnetic oscillation to discharge stacking bubbles to reduce porosity and other effects to comprehensively improve the various service performances of the Cu-based coating during cold spraying of the substrate. The present invention belongs to the field of surface coating protection technology for parts and components and the preparation of electronic components, especially for the application of wear-resistant, heat-conductive, and highly conductive parts and products (electronic components in the military and aerospace fields, engine wear-resistant parts and railway tracks in the transportation field, electronic product heat dissipation layers in the power electronics field, and battery panels in the energy field, etc.) It has played a good effect.

[0009] The advantages of the present invention are:

[0010] 1. Magnetic field assisted cold spraying technology has the advantages of magnetic field assisted non-contact and does not damage the original state of the substrate and coating. It is mainly reflected in that it does not limit the size of the substrate and coating, and can achieve the purpose of conformal processing;

[0011] 2. The magnetic field intensity generated by the magnetic field can well improve the flight-spreading-stacking behavior of the Cu-based coating particles, so that the coating particle beam is more concentrated, the spreading and stacking quality is better, the coating is dense as a whole, and the porosity is reduced;

[0012] 3. The present invention uses cold spraying to prepare the Cu-based coating, which will not damage the material properties of the Cu-based powder due to high temperature, so that it still maintains the excellent properties of high conductivity, wear resistance and corrosion resistance, and the coating thickness is uniform and can reach 500μm;

[0013] 4. The magnetic field device in the present invention is an existing device, which is simple in function, controlled by software, easy to operate, highly safe and pollution-free. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a physical picture of the magnetic field device in step 2 of experiment 1;

[0015] Figure 2 This is the pulse magnetic field waveform diagram in step 2 of experiment 1;

[0016] Figure 3 This is a time period diagram of the pulse magnetic field in step 2 of experiment 1;

[0017] Figure 4 This is a cross-sectional SEM microscopic image of the Cu-based coating prepared on the metal substrate in Experiment 1;

[0018] Figure 5 It is a comparison chart of the friction coefficient curves of the Cu-based coating prepared in the test 1, the comparative test and the test 2;

[0019] Figure 6 The bonding strength and porosity test data of the Cu-based coating prepared in Experiment 1, Comparative Experiment and Experiment 2 are shown in FIG. DETAILED DESCRIPTION

[0020] Specific implementation method 1: This implementation method is a method for preparing a high-strength and dense Cu-based coating by cold spraying, which is specifically carried out in the following steps:

[0021] 1. Pre-treat the substrate;

[0022] 2. cold spraying the pretreated substrate under the action of an external magnetic field to obtain a Cu-based coating with a thickness of 300 μm to 500 μm;

[0023] The magnetic field device for applying an external magnetic field is located directly below the substrate.

[0024] Specific implementation method 2: This implementation method is different from specific implementation method 1 in that the substrate described in step 1 is a metal substrate or a ceramic substrate. The rest is the same as specific implementation method 1.

[0025] Specific implementation method three: This implementation method is different from specific implementation method two in that: the method of pre-treating the metal substrate in step one is: sanding the metal substrate with sandpaper until the surface is bright and clean, without burrs, oxide scale and rust; then sandblasting the surface of the metal substrate to increase the roughness of the substrate surface and improve the deposition efficiency of the cold spraying powder particles; finally, preheating the metal substrate to 200°C;

[0026] The method for pre-treating the ceramic substrate in step 1 is: grinding the ceramic substrate with sandpaper until the surface is bright and clean, without burrs, oxide scale and rust; then sandblasting the surface of the ceramic substrate to increase the roughness of the substrate surface and improve the deposition efficiency of the cold spray powder particles. The rest is the same as the second embodiment.

[0027] Specific embodiment 4: This embodiment is different from specific embodiments 1 to 3 in that: the process parameters of cold spraying described in step 2 are: the spraying distance is 30 mm; the gas used for cold spraying is nitrogen; the air pressure of cold spraying is 2.5 MPa; the powder feeding rate of cold spraying is 75 g / min; the internal preheating temperature of the cold spraying gun is 450°C to 600°C; the moving speed of the cold spraying gun is 120 mm / s. Others are the same as those of specific embodiments 1 to 3.

[0028] Specific implementation mode 5: This implementation mode is different from specific implementation mode 4 in that the external magnetic field described in step 2 is a pulse magnetic field, a steady magnetic field, an alternating magnetic field or a DC magnetic field. The rest is the same as specific implementation mode 4.

[0029] Specific implementation method 6: This implementation method is different from specific implementation method 5 in that the magnetic field strength of the pulse magnetic field described in step 2 is 2T to 11T, the power supply is a pulse high-voltage power supply and the power supply charges the capacitor, and the high-intensity pulse magnetic field is released instantly through software control, the pulse magnetic field generation cycle is 30s, and the duration of the magnetic field in one cycle is 10ms. Others are the same as specific implementation method 5.

[0030] Specific implementation example 7: This implementation example is different from specific implementation example 5 in that the steady magnetic field described in step 2 utilizes the strong magnetic steady magnetic property of the NdFeB magnet to form the steady magnetic field. The rest is the same as specific implementation example 5.

[0031] Specific implementation example eight: This implementation example is different from specific implementation example five in that the alternating magnetic field described in step two is formed by an electromagnet composed of an alternating current power source, an energized coil and an iron core. The rest is the same as specific implementation example five.

[0032] Specific implementation method 9: This implementation method is different from specific implementation method 5 in that the DC magnetic field described in step 2 is formed by an electromagnet composed of a powered coil connected to a DC power source and an iron core. The rest is the same as specific implementation method 5.

[0033] Specific embodiment 10: This embodiment differs from specific embodiment 1 in that the Cu-based coating in step 2 is pure Cu powder, brass powder, tin bronze powder or composite powder of Cu and silicon dioxide. Other aspects are the same as those of specific embodiment 1.

[0034] The present invention is verified by the following tests:

[0035] Experiment 1: This experiment is a method for preparing a high-strength and dense Cu-based coating by cold spraying, which is specifically carried out in the following steps:

[0036] 1. Pre-treating the metal substrate; the metal substrate is a 4032 aluminum alloy plate;

[0037] The method for pretreating the metal substrate is as follows: immersing the 4032 aluminum alloy plate in alcohol and ultrasonically cleaning the surface oil stains; then sanding the metal substrate with sandpaper until the surface is bright and clean without burrs, oxide scale and rust; then sandblasting the surface of the metal substrate to increase the roughness of the substrate surface and improve the deposition efficiency of cold spray powder particles; finally preheating the substrate aluminum alloy plate to 200°C;

[0038] 2. cold spraying the pretreated metal substrate under the action of an external magnetic field to obtain a Cu-based coating;

[0039] The external magnetic field is a pulsed magnetic field, and the magnetic field device (an existing device, not the invention of the present invention) is located directly below the metal substrate, such as Figure 1 The spray gun is placed just above the metal substrate (i.e. the sprayed sample in the figure) and the coating, and the lower part is a pulse magnet coil; the magnetic field strength of the pulse magnetic field is 2T to 11T, the power supply is a pulse high-voltage power supply and the power supply charges the capacitor, and the high-intensity pulse magnetic field is released instantly through software control. The pulse magnetic field generation cycle is 30s, and the duration of the magnetic field in one cycle is 10ms (see Figure 2 and Figure 3 );

[0040] The process parameters of cold spraying described in step 2 are as follows: the spraying distance is 30 mm; the gas used for cold spraying is nitrogen; the air pressure of cold spraying is 2.5 MPa; the powder feeding rate of cold spraying is 75 g / min; the internal preheating temperature of the cold spraying gun is 550°C; the moving speed of the cold spraying gun is 120 mm / s; the Cu-based coating is pure Cu powder.

[0041] Figure 4 This is a cross-sectional SEM microscopic morphology image of the Cu-based coating prepared on the metal substrate in Experiment 1. The light-colored part at the top of the image is the Cu-based coating, and the dark-colored part at the bottom is the 4032 aluminum alloy substrate. It can be seen from the image that the prepared Cu-based coating is very dense, with almost no pores, and no cracks or inclusions at the interface, showing strong bonding properties and low porosity. At the same time, the coating thickness can reach 500μm.

[0042] Comparative test: This test is different from the first test in that no external magnetic field is set in step 2. The rest is the same as the first test.

[0043] Experiment 2: This experiment is different from Experiment 1 in that the metal substrate described in step 1 is a DBC ceramic plate, and no preheating is required during the pretreatment. The rest is the same as Experiment 1.

[0044] Figure 5 The friction coefficient curves of the Cu-based coating prepared in the first test, the comparative test and the second test are compared. The black line corresponds to the first test, the red line corresponds to the comparative test, and the blue line corresponds to the second test. The tribological test was carried out on a standard friction and wear test equipment (model: MPT-3G). The pin-disc friction pair was loaded on the equivalent flat part of the spherical bearing. The bearing was fixed, and the pin-disc was the friction pair rotating. The tribological performance of the equivalent flat part of the bearing was tested. Figure 5It can be seen that the average friction coefficient of the copper-based coating on the aluminum substrate with magnetic field strengthening in experiment 1 is 0.491, the average friction coefficient of the copper-based coating on the aluminum substrate without magnetic field strengthening in the comparative experiment is 0.589, and the average friction coefficient of the copper-based coating on the DBC ceramic substrate with magnetic field strengthening in experiment 2 is 0.471. After comparison, it is found that the friction coefficient of the coating is significantly reduced after magnetic field strengthening, and the wear resistance is greatly improved.

[0045] Figure 6 The bonding strength and porosity test data of the Cu-based coating prepared in Experiment 1, Comparative Experiment and Experiment 2 are shown in Figure 2. The bonding strength was measured by the bonding tensile method. The bonding strength tensile test was performed three times for each of the three coatings, and the average value was taken to form the Figure 6 The results shown show that the coating bonding strength of the magnetic field-assisted aluminum alloy substrate in test 1 was significantly improved to 20.9MPa, compared with 15.4MPa in the non-magnetic field test, and slightly improved to 17.6MPa in the DBC substrate in test 2. The porosity results were captured by cross-section SEM to perform pore statistics, and it was found that the porosity on the aluminum alloy assisted by the magnetic field in test 1 and the DBC substrate in test 2 was significantly reduced to 0.85% and 0.92% respectively, while the non-magnetic field in the comparative test was 1.26%, which shows that the pulsed magnetic field has a good improvement effect on the porosity of the cold spray coating.

Claims

1. A method for preparing a high-strength and dense Cu-based coating by cold spraying, characterized in that The method for preparing high-strength and dense Cu-based coating by cold spraying is carried out in the following steps:

1. Pre-treat the substrate; 2. cold spraying the pretreated substrate under the action of an external magnetic field to obtain a Cu-based coating with a thickness of 300 μm to 500 μm; The magnetic field device for applying an external magnetic field is located directly below the substrate.

2. The method for preparing a high-strength and dense Cu-based coating by cold spraying according to claim 1, characterized in that The substrate described in step 1 is a metal substrate or a ceramic substrate.

3. The method for preparing a high-strength and dense Cu-based coating by cold spraying according to claim 2, characterized in that The method for pre-treating the metal substrate in step 1 is: sanding the metal substrate until the surface is bright and clean without burrs, oxide scale and rust; then sandblasting the surface of the metal substrate to increase the roughness of the substrate surface and improve the deposition efficiency of the cold spray powder particles; finally, preheating the metal substrate to 200°C; The method for pre-treating the ceramic substrate in step 1 is: sanding the ceramic substrate with sandpaper until the surface is bright and clean without burrs, oxide scale and rust; then sandblasting the surface of the ceramic substrate to increase the roughness of the substrate surface and improve the deposition efficiency of the cold spray powder particles.

4. The method for preparing a high-strength and dense Cu-based coating by cold spraying according to claim 1, characterized in that The process parameters of cold spraying described in step 2 are: spraying distance is 30 mm; the gas used for cold spraying is nitrogen; the gas pressure of cold spraying is 2.5 MPa; the powder feeding rate of cold spraying is 75 g / min; the internal preheating temperature of the cold spraying gun is 450°C to 600°C; the moving speed of the cold spraying gun is 120 mm / s.

5. The method for preparing a high-strength and dense Cu-based coating by cold spraying according to claim 1, characterized in that The external magnetic field described in step 2 is a pulsed magnetic field, a steady magnetic field, an alternating magnetic field or a direct current magnetic field.

6. The method for preparing a high-strength and dense Cu-based coating by cold spraying according to claim 5, characterized in that The magnetic field strength of the pulse magnetic field described in step 2 is 2T~11T, the power supply is a pulse high-voltage power supply and the power supply charges the capacitor, and the high-intensity pulse magnetic field is released instantly through software control. The pulse magnetic field generation cycle is 30s, and the duration of the magnetic field in one cycle is 10ms.

7. The method for preparing a high-strength and dense Cu-based coating by cold spraying according to claim 5, characterized in that The steady magnetic field described in step 2 utilizes the strong magnetic stability characteristics of the NdFeB magnet to form a steady magnetic field.

8. The method for preparing a high-strength and dense Cu-based coating by cold spraying according to claim 5, characterized in that The alternating magnetic field described in step 2 is formed by utilizing an alternating current power source and an electromagnet which is a combination of an energized coil and an iron core.

9. The method for preparing a high-strength and dense Cu-based coating by cold spraying according to claim 5, characterized in that The DC magnetic field described in step 2 is formed by an electromagnet composed of an energized coil connected to a DC power source and an iron core.

10. The method for preparing a high-strength and dense Cu-based coating by cold spraying according to claim 1, characterized in that The Cu-based coating in step 2 is pure Cu powder, brass powder, tin bronze powder or composite powder of Cu and silicon dioxide.

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