A preparation method of a copper alloy-tungsten copper composite electrical contact by laser additive manufacturing

Abstract

The present invention belongs to the fields of electrical and electronic engineering and advanced nonferrous metal additive manufacturing. Specifically, it relates to a method for preparing copper alloy-tungsten-copper composite electrical contacts using laser additive manufacturing. The method uses coaxial powder feeding laser cladding to prepare a nickel or nickel alloy coating as an intermediate layer on a copper alloy substrate. This is followed by laser cladding to prepare a tungsten-copper coating. The composite electrical contact consists, in sequence, of a pure copper or copper alloy substrate layer, a pure nickel or nickel alloy coating, and a tungsten-copper coating. The resulting electrical contact has high electrical and thermal conductivity and good resistance to arc erosion. Using laser cladding technology to prepare copper alloy-tungsten-copper electrical contacts can effectively reduce production costs, improve production efficiency, and facilitate subsequent maintenance and repair, making it environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the field of electrical engineering, electronics and advanced nonferrous metal additive manufacturing, and specifically relates to a preparation method of a copper alloy-tungsten-copper composite electrical contact manufactured by laser additive manufacturing. Technical Background

[0002] Electrical contacts, responsible for connecting and disconnecting current, are critical components in high- and low-voltage electrical equipment. Their reliability, durability, and stability directly impact the safety and service life of switches. Copper alloys offer advantages such as high electrical and thermal conductivity and excellent processability, but their mechanical strength, wear resistance, and ablation resistance fall short of meeting the performance requirements of electrical contact materials. In recent years, W-Cu has been widely used as an improved contact material due to its high strength, good wear resistance, and strong resistance to arc ablation. Traditional preparation methods include melt infiltration and liquid-phase sintering. When preparing tungsten-copper composites using the melt infiltration method, factors such as powder particle size and the addition of inducers during pre-sintering of the tungsten skeleton significantly influence the microstructure. Furthermore, the sintering of the tungsten skeleton can lead to uneven porosity, resulting in the formation of closed pores, making it difficult for copper to penetrate. Consequently, the remaining uninfiltrated copper must be removed through machining, increasing production costs. Materials prepared using liquid-phase sintering have relatively low density and suffer from significant copper volatilization, resulting in high production costs. The wear and ablation of electrical contacts mainly occur on the surface of the material. Therefore, the preparation of W-Cu coating on copper alloy through surface modification technology can not only retain the excellent electrical and thermal conductivity of copper alloy, but also improve the surface wear resistance, arc erosion resistance and mechanical properties.

[0003] Laser cladding technology utilizes a controllable high-energy, high-power density heat source, enabling the rapid solidification of the material. This not only refines the microstructure but also improves the surface's resistance to thermal fatigue. It is also easy to operate and requires simple equipment. However, due to the high laser reflectivity of copper and copper alloys, a transition layer is typically deposited on the surface before laser cladding is performed to create the coating. The patent "A Method for Manufacturing Pure Copper / Copper-Chromium Alloy Composite Contact Material" (Patent No.: CN101834077 A) discloses a method for preparing a Cu-Cr paste using a binder, pre-depositing a coating of a certain thickness on the copper surface, and then drying it for laser cladding. However, due to the extremely rapid solidification of the molten pool, decomposition or incomplete volatilization of the added binder can lead to defects such as holes and cracks between the substrate and the coating, severely impacting their bonding performance. Furthermore, the continuous laser input causes the overall material temperature to rise, potentially causing the pre-deposited coating to flake off, significantly impacting the cladding process. Spraying combined with laser remelting is also a method for modifying the surface of copper and copper alloys. For example, the patent "A Heat-Dissipating Tungsten-Copper Coating Material for Electronic Packaging and Its Preparation Method" (Patent No.: CN 107620030 A) discloses plasma spraying of W-Cu composite powder onto an oxygen-free copper surface followed by laser remelting. However, the rapid heating and cooling characteristics of laser remelting can easily lead to cracks and coating flaking. Currently, the production of composite electrical contacts with excellent performance and good interfacial bonding remains a significant challenge. Summary of the Invention

[0004] In response to the shortcomings of the current methods for preparing copper alloy-tungsten-copper composite electrical contacts, the present invention provides a method for preparing copper alloy-tungsten-copper composite electrical contacts by laser additive manufacturing: a nickel or nickel alloy transition layer is prepared on the surface of a clean copper alloy by laser cladding, and then W-Cu cladding is performed. In addition to the good wear resistance and corrosion resistance of nickel-based alloys themselves and having certain toughness and good wetting and lubrication properties, the atomic radius, density, and specific heat of copper and nickel are very similar, and both copper and nickel have face-centered cubic structures, which can form infinite or limited mutual solubility in both solid and liquid states, which is conducive to forming a good metallurgical bond between the substrate and the coating, and is suitable for laser cladding on the surface of copper and copper alloys. For W-Cu composite materials, nickel can also promote the solid solution of W and Cu.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] Step 1: Clean and degrease the processed surface of the pure copper or copper alloy substrate, sandblast, clean, and air-dry at room temperature; cleaning and degreasing are performed by ultrasonic cleaning with acetone solution for 5 minutes, and then rinsing with deionized water; sandblasting is performed by using corundum to treat the material surface with a sandblasting pressure of 0.6 MPa; cleaning is performed by ultrasonic cleaning with anhydrous ethanol for 5 minutes.

[0007] Step 2: Place the substrate processed in step 1 in a forming chamber with an oxygen content of less than 2000 ppm for preheating.

[0008] Step 3: Prepare pure nickel or nickel alloy coating by laser cladding on pure copper or copper alloy substrate. The specific process parameters are: laser power 300-500W, scanning rate 300-600mm / min, spot diameter 1.2mm-3mm, overlap rate 40%-60%.

[0009] Step 4: Using tungsten copper powder as raw material, laser cladding is performed on the pure nickel or nickel alloy coating to prepare a tungsten copper coating. The specific process parameters are set as follows: laser power 200-1000 W, scanning rate 200-800 mm / min, spot diameter 1.2 mm-3 mm, and overlap rate 35%-65%.

[0010] Step 5: Machining and cleaning the copper alloy-tungsten copper composite electrical contacts to ensure that the copper alloy-tungsten copper composite electrical contacts meet industry standards.

[0011] Furthermore, in step 1, the copper alloy is selected from: a Cu-Cr alloy, a Cu-Sn alloy or a Cu-Zn alloy, and the mass percentage of copper is not less than 50%.

[0012] Furthermore, in step 2, the forming chamber is in an inert atmosphere, and the preheating temperature of the substrate is not less than 100°C.

[0013] Furthermore, in step three, the raw material for preparing the nickel alloy coating is selected from: one of Ni-Cr alloy, Ni-Mo alloy or Ni-Cu alloy, and the mass percentage of nickel is not less than 60%.

[0014] Furthermore, in step three, the thickness of the pure nickel or nickel alloy coating is not less than 0.02 mm and does not exceed 20% of the thickness of the substrate.

[0015] Furthermore, in the step 4, the composition ratio of the tungsten copper powder is W:Cu by mass ratio of 95 / 5 to 10 / 90.

[0016] Furthermore, in step 4, the thickness of the tungsten copper coating is not less than 0.2 mm and not more than 50% of the thickness of the substrate.

[0017] The copper alloy-tungsten copper composite electrical contact prepared by the method of the present invention is composed of a pure copper or copper alloy substrate layer, a pure nickel or nickel alloy coating and a tungsten copper coating in sequence.

[0018] The method of the present invention can realize the low-cost and short-process preparation of copper alloy-tungsten copper composite electrical contacts. The process is simple, the technology is easy to control, and it can realize automated production. It is green, environmentally friendly, and pollution-free. The specific beneficial effects are as follows:

[0019] (1) Due to the high reflectivity of copper, the laser absorption performance of tungsten copper powder is better than that of pure copper. Small laser energy input will result in the substrate being unable to form a molten pool or the molten pool being narrow and shallow, making it difficult for tungsten copper to form a good metallurgical bond with the substrate and form an excellent coating; excessive laser energy input will cause a large amount of copper in the powder to volatilize, which not only affects the stability of the cladding process, but also causes uneven coating structure, holes, cracks and other defects; the present invention uses pure nickel or nickel alloy as an intermediate layer before preparing tungsten copper composite material coating by laser cladding. On the one hand, it can effectively reduce the reflection of the copper substrate to the laser, and on the other hand, nickel can promote the wetting of tungsten and copper, which can significantly improve the uniformity of the structure of the tungsten copper composite material coating and effectively avoid the generation of holes, cracks, etc.

[0020] (2) The electric contact manufactured by the present invention has a core that maintains the excellent electrical and thermal conductivity of copper and copper alloys, and a surface that has the excellent arc erosion resistance of tungsten-copper composite materials. Moreover, when the electric contact reaches the end of its service life and has defects, it can be directly repaired by laser cladding and reused, which greatly reduces costs and waste of resources.

[0021] (3) The method of the present invention uses metal powder to directly clad the functional layers without the need for a binder. During the rapid solidification and crystallization of the cladding layer, the gas generated by the thermal decomposition of the binder is avoided from being retained in the pores formed in the cladding layer and contaminating the surface of the substrate, thereby improving the quality of the fusion of the substrate and the coating; at the same time, the cost is reduced, the process is simplified, and the production process is more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 SEM images of the copper alloy-tungsten-copper composite electrical contact prepared in Example 1: (a) low magnification (b) high magnification;

[0023] Figure 2 SEM images of the copper alloy-tungsten-copper composite electrical contact prepared in Example 2: (a) low magnification (b) high magnification;

[0024] Figure 3 SEM image of the copper alloy-tungsten-copper composite electrical contact prepared in Comparative Example 1;

[0025] Figure 4 SEM image of the copper alloy-tungsten-copper composite electrical contact prepared in Comparative Example 2. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Example

[0027] Step 1: Using a pure copper plate as the substrate, the surface of the substrate is cleaned and degreased, sandblasted, cleaned, and air-dried at room temperature; the cleaning and degreasing is to use acetone ultrasonic cleaning for 5 minutes, and then rinse with deionized water; sandblasting is to use corundum to treat the material surface, and the sandblasting pressure is 0.3 MPa; cleaning is to use anhydrous ethanol ultrasonic cleaning for 5 minutes; and air-dry at room temperature.

[0028] Step 2: Fix the substrate on the heating plate of the forming chamber, fill the forming chamber with argon gas with an oxygen content of 2000 ppm, and preheat the substrate to 300°C;

[0029] Step 3: Using pure nickel powder as raw material, laser cladding nickel coating on the surface of the substrate. The cladding process parameters are set as follows: laser power 300W, scanning rate 350mm / min, spot diameter 1.5mm, overlap rate 60%, and nickel coating thickness 0.1mm;

[0030] Step 4: Using W-40 wt.% Cu powder as the raw material, a tungsten-copper coating was clad on the nickel coating. The cladding process parameters were set as follows: laser power 400 W, scanning rate 400 mm / min, spot diameter 1.5 mm, overlap rate 65%, and total thickness of the tungsten-copper coating 0.4 mm.

[0031] Step 5: Machining and cleaning the copper alloy-tungsten copper electrical contacts to make them meet the industry standards. Figure 1 .

[0032] Hardness (HV0.5) Electrical conductivity (%IACS) Thermal conductivity (W / (m*K)) 162 58 312 Example

[0033] Step 1: Use pure copper plate as the substrate, clean and degrease the substrate surface, sandblast, clean, and air-dry at room temperature; cleaning and degreasing is done by using acetone ultrasonic cleaning for 5 minutes, and then rinsing with deionized water; sandblasting is done by using corundum to treat the material surface, with a sandblasting pressure of 0.4 MPa; cleaning is done by using anhydrous ethanol ultrasonic cleaning for 5 minutes, and air-drying at room temperature.

[0034] Step 2: Fix the substrate on the heating plate of the forming chamber, fill the forming chamber with argon gas with an oxygen content of 200 ppm, and preheat the substrate to 400°C.

[0035] Step 3: Using Ni-Cr alloy powder as raw material, a nickel alloy coating was clad on the surface of the substrate. The cladding process parameters were set as follows: laser power 400 W, scanning rate 500 mm / min, spot diameter 2 mm, overlap rate 45%, cladding single layer of nickel, and the total thickness of the nickel coating was 0.15 mm.

[0036] Step 4: Using W-20 wt.% Cu powder as raw material, a tungsten-copper composite coating was clad on the nickel coating. The cladding process parameters were set as follows: laser power 500 W, scanning rate 500 mm / min, spot diameter 2 mm, overlap rate 50%, and total thickness of the tungsten-copper coating 0.6 mm.

[0037] Step 5: Machining and cleaning the copper alloy-tungsten copper composite electrical contact to make it meet the industry standard. Figure 2 and the table below.

[0038] Hardness (HV0.5) Electrical conductivity (%IACS) Thermal conductivity (W / (m*K)) 218 45 287 Example

[0039] Step 1: Use pure copper plate as the substrate, clean and degrease the substrate surface, sandblast, clean, and air-dry at room temperature; cleaning and degreasing is done by using acetone ultrasonic cleaning for 5 minutes, and then rinsing with deionized water; sandblasting is done by using corundum to treat the material surface, with a sandblasting pressure of 0.6 MPa; cleaning is done by using anhydrous ethanol ultrasonic cleaning for 5 minutes; and finally, air-dry at room temperature.

[0040] Step 2: Fix the substrate on the heating plate of the forming chamber, fill the forming chamber with argon gas with an oxygen content of 500 ppm, and preheat the substrate to 500°C.

[0041] Step 3: Using nickel powder as raw material, a nickel coating is clad on the surface of the substrate. The cladding process parameters are set as follows: laser power 500W, scanning rate 700 mm / min, spot diameter 2 mm, overlap rate 50%, and total nickel coating thickness 0.5 mm;

[0042] Step 4: Using W-10 wt.% Cu powder as raw material, a tungsten-copper coating was clad on the nickel coating. The cladding process parameters were set as follows: laser power 1000 W, scanning rate 750 mm / min, spot diameter 3 mm, overlap rate 30%, and total thickness of the tungsten-copper coating 1.5 mm.

[0043] Step 5: Machining and cleaning the copper alloy-tungsten copper composite electrical contacts to ensure they meet industry standards. Their performance is shown in the table below.

[0044] Hardness (HV0.5) Electrical conductivity (%IACS) Thermal conductivity (W / (m*K)) 385 18 141

[0045] Step 1: Use a 5mm thick pure copper plate as the substrate, clean and degrease the substrate surface, sandblast, clean, and air-dry at room temperature; cleaning and degreasing is to use acetone ultrasonic cleaning for 5 minutes, and then rinse with deionized water; sandblasting is to use corundum to treat the material surface, and the sandblasting pressure is 0.4 MPa; cleaning is to use anhydrous ethanol ultrasonic cleaning for 5 minutes; finally, air-dry at room temperature.

[0046] Step 2: Fix the substrate on the heating plate of the forming chamber, fill the forming chamber with argon gas with an oxygen content of 200 ppm, and preheat the substrate to 400°C.

[0047] Step 3: Using W-20 wt.% Cu powder as the raw material, a tungsten-copper composite coating was clad on the substrate. The cladding process parameters were set as follows: laser power 500 W, scanning rate 500 mm / min, spot diameter 2 mm, overlap rate 50%, and total tungsten-copper coating thickness 0.3 mm.

[0048] Step 5: Machining and cleaning the copper alloy-tungsten copper composite electrical contact. Its SEM image and performance are as follows: Figure 3 and the table below.

[0049] Hardness (HV0.5) Electrical conductivity (%IACS) Thermal conductivity (W / (m*K)) 136 13 102

[0050] Compared with the embodiment, in Comparative Example 1, a nickel coating was not prepared as a transition layer, and a tungsten-copper composite material coating was directly prepared on a copper alloy substrate using the same parameters. It was found that the bonding quality between the coating and the substrate was poor, and a large number of holes were present, which greatly affected the bonding between the coating and the substrate and reduced the performance of the material.

[0051] Step 1: Using a 2 mm thick pure copper plate as the substrate, the substrate surface is cleaned and degreased, sandblasted, cleaned, and air-dried at room temperature; the cleaning and degreasing is to use acetone ultrasonic cleaning for 5 minutes, and then rinse with deionized water; sandblasting is to use corundum to treat the material surface, and the sandblasting pressure is 0.6 MPa; cleaning is to use anhydrous ethanol ultrasonic cleaning for 5 minutes; finally, air-dry at room temperature.

[0052] Step 2: Fix the substrate on the heating plate of the forming chamber, fill the forming chamber with argon gas, and preheat the substrate to 500°C with an oxygen content of 50ppm.

[0053] Step 3: Using nickel powder as raw material, a nickel coating is clad on the surface of the substrate. The cladding process parameters are set as follows: laser power 500W, scanning rate 700 mm / min, spot diameter 2 mm, overlap rate 50%, and total nickel coating thickness 0.1 mm;

[0054] Step 4: Using W-25 wt.% Cu powder as raw material, a tungsten-copper composite coating was clad on the nickel coating. The cladding process parameters were set as follows: laser power 1000 W, scanning rate 750 mm / min, spot diameter 3 mm, overlap rate 50%, and total thickness of the tungsten-copper coating 2 mm;

[0055] Step 5: Machining and cleaning the copper alloy / tungsten copper electrical contacts. Figure 4 and the table below.

[0056] Hardness (HV0.5) Electrical conductivity (%IACS) Thermal conductivity (W / (m*K)) 216 9 122

[0057] Compared with the embodiment, the thickness of the copper coating in Comparative Example 2 is equivalent to the thickness of the substrate. In the obtained copper alloy-tungsten-copper composite electrical contact, obvious defects appear at the junction of the substrate and the coating, and the tungsten phase and copper phase are unevenly distributed in the coating, which greatly reduces the performance of the material.

[0058] The above describes in detail the preferred embodiments of this patent, but this patent is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by ordinary technicians in this field without departing from the purpose of this patent.

Claims

1. A method for preparing a copper alloy-tungsten copper composite electrical contact by laser additive manufacturing, characterized in that: The following steps are involved: Step 1: Clean and degrease the processed surface of the pure copper or copper alloy substrate, sandblast it, clean it, and air-dry it at room temperature; cleaning and degreasing is done by ultrasonic cleaning with acetone solution for 5 minutes, followed by rinsing with deionized water; sandblasting is done by using corundum to treat the surface of the material at a sandblasting pressure of 0.6 MPa; cleaning is done by ultrasonic cleaning with anhydrous ethanol for 5 minutes; Step 2: placing the substrate treated in step 1 in a forming chamber with an oxygen content of less than 2000 ppm for preheating; Step 3: Prepare a pure nickel or nickel alloy coating by laser cladding on the pure copper or copper alloy substrate. The specific process parameters are: laser power 300-500W, scanning rate 300-600mm / min, spot diameter 1.2mm-3mm, overlap rate 40%-60%, pure nickel or nickel alloy coating thickness not less than 0.02mm, not more than 20% of the substrate thickness, and nickel mass percentage in the nickel alloy not less than 60%; Step 4: Using tungsten copper powder as raw material, laser cladding is performed on the pure nickel or nickel alloy coating to prepare a tungsten copper coating. The specific process parameters are set as follows: laser power 200-1000 W, scanning rate 200-800 mm / min, spot diameter 1.2 mm-3 mm, overlap rate 35%-65%, and the thickness of the tungsten copper coating is not less than 0.2 mm and not more than 50% of the substrate thickness. Step 5: Machining and cleaning the copper alloy-tungsten copper composite electrical contacts to ensure that the copper alloy-tungsten copper composite electrical contacts meet industry standards.

2. The method for preparing a copper alloy-tungsten copper composite electrical contact by laser additive manufacturing according to claim 1, characterized in that: In the step 1, the copper alloy is selected from: a Cu-Cr alloy, a Cu-Sn alloy or a Cu-Zn alloy, and the mass percentage of copper is not less than 50%.

3. The method for preparing a copper alloy-tungsten copper composite electrical contact by laser additive manufacturing according to claim 1, characterized in that: In the step 2, the forming chamber is in an inert atmosphere, and the preheating temperature of the substrate is not less than 100°C.

4. The method for preparing a copper alloy-tungsten copper composite electrical contact by laser additive manufacturing according to claim 1, characterized in that: In the step 3, the raw material for preparing the nickel alloy coating is selected from: Ni-Cr alloy, Ni-Mo alloy or Ni-Cu alloy.

5. The method for preparing a copper alloy-tungsten copper composite electrical contact by laser additive manufacturing according to claim 1, characterized in that: In the step 4, the composition ratio of the tungsten copper powder is W:Cu by mass ratio of 95 / 5 to 10 / 90.

6. The copper alloy-tungsten-copper composite electrical contact prepared by the preparation method according to any one of claims 1 to 5, characterized in that: It consists of a pure copper or copper alloy substrate layer, a pure nickel or nickel alloy coating and a tungsten copper coating.

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