Copper surface laser cladding conductive wear-resistant copper-based medium entropy alloy coating, preparation method and application

Abstract

This invention discloses a conductive and wear-resistant copper-based medium-entropy alloy coating laser cladding on a copper surface, its preparation method, and its application. The coating's chemical composition, by mass percentage, is 20-30 wt.% Mn, 20-30 wt.% Ni, and 40-60 wt.% Cu. The preparation process requires no pretreatment of the copper substrate. Using a conventional red laser, with power of 3.2-4.5 kW and scanning speed of 2-12 mm / s, a well-formed, continuous, dense coating free of pores and cracks can be directly clad onto a cold copper substrate. The cladding thickness is 0.4-2 mm, and it forms a metallurgical bond with the substrate, meeting the quality requirements for industrial applications. Furthermore, after aging at 350-450 °C for 36-60 h, a large amount of nano-sized NiMn phase precipitates, and the aged hardness exceeds 400 HV. 0.5 With a conductivity exceeding 30% IACS, it can be widely used in electrical engineering current-carrying wear-resistant applications, marine corrosion protection, metallurgical and chemical wear-resistant applications, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of alloy material design and relates to a conductive and wear-resistant copper-based medium-entropy alloy coating suitable for laser cladding on copper surfaces and its preparation method. Background Technology

[0002] There is an urgent need for surface strengthening of low-hardness copper in engineering applications. Current technologies mainly employ electroplating or thermal spraying, resulting in coating thicknesses generally less than 300 μm and poor bonding performance due to only mechanical adhesion to the substrate. Laser cladding can produce thicker coatings and form a metallurgical bond with the substrate, offering significant technological advantages. However, highly reflective copper has an absorption rate of less than 10% for laser light and extremely high thermal conductivity, leading to insufficient laser energy input and difficulty in forming a stable molten pool on the copper surface, resulting in a poor cladding quality. To address this, numerous patents and publications have explored pretreatment processes such as pre-applying a transition layer to the copper substrate, sandblasting, high-temperature preheating, or spraying light-absorbing materials, or using extremely high laser power (above 6 kW) or extremely small spot sizes to increase input energy density, to obtain high-hardness, wear-resistant Ni- or Co-based coatings on the copper surface. However, Ni- or Co-based coatings have poor electrical conductivity, significantly reducing the electrical and thermal conductivity of the copper substrate. Furthermore, this type of solution involves a complex process, and excessively high laser power and energy input density can easily cause severe spattering, porosity, and cracks in the molten pool. It also increases the substrate dilution rate, leading to significant deviations between the coating composition and the design objectives. In addition, the strong reflection of excessively high-power lasers by the copper substrate can cause irreversible damage to equipment and pose safety hazards to personnel. Especially when cladding copper surfaces with copper-based conductive wear-resistant alloy coatings that have similar thermophysical properties to the substrate, the high reflectivity and low hardness of the copper-based coating material itself limit the technological advancements required.

[0003] This invention discloses a method for direct laser cladding of Cu on a cold copper substrate. (100-2x) Ni x Mn x (x=20~30) describes the composition and preparation process of a copper-based wear-resistant medium-entropy alloy coating. This process utilizes a conventional red laser with a power of 3.2~4.5 kW. The resulting coating exhibits excellent surface quality, is crack-free, and has a dense microstructure, fully meeting the requirements of industrial applications. The coating hardness exceeds 500 HV. 0.5 This coating exhibits extremely high hardness among current copper-based alloy coatings, significantly improving the wear resistance of copper surfaces and providing excellent electrical conductivity due to its high copper content. Furthermore, the matching thermophysical properties of the coating with the copper substrate help mitigate the tendency for the coating to peel off and crack during thermal cycling. Summary of the Invention

[0004] This invention discloses a conductive and wear-resistant copper-based medium-entropy alloy coating suitable for laser cladding on copper surfaces and its preparation method. It enables the preparation of a high-metallurgical-bonding-strength, high-hardness, and wear-resistant copper-based alloy coating on a cold copper substrate surface without any pretreatment processes or conventional laser cladding parameters. Compared with previous methods for preparing Ni- and Co-based wear-resistant coatings by laser cladding on copper surfaces, the copper-based medium-entropy alloy coating disclosed in this project not only exhibits higher hardness and wear resistance after aging but also boasts a simpler process. The coating's thermophysical properties match those of the copper substrate, which helps mitigate the tendency for peeling and cracking that easily occurs during thermal cycling, while also providing good conductivity.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] This invention provides a conductive and wear-resistant copper-based medium-entropy alloy coating laser cladding on a copper surface. The chemical composition of the coating, by mass percentage, is 20-30 wt.% Mn, 20-30 wt.% Ni, and 40-60 wt.% Cu.

[0007] Furthermore, the coating raw materials are Mn, Ni and Cu elemental powders, the particle size of the elemental metal powders is 45-150 μm, and the purity is not less than 99.5 wt.%.

[0008] This invention provides a method for preparing a conductive and wear-resistant copper-based medium-entropy alloy coating by laser cladding on a copper surface. The method employs a conventional red laser to directly clad the coating onto a cold-base copper plate without any pretreatment via coaxial powder feeding. The laser cladding process parameters are: power 3.2~4.5 kW, scanning speed 2~12 mm / s, overlap rate 45~65%, powder feeding rate 5~15 g / min, and a circular spot with a diameter of 3~5 mm or a broadband spot with a diameter of 10~12 mm can be used.

[0009] Furthermore, argon gas is used for synchronous protection during the laser cladding process.

[0010] Furthermore, the coating exhibits excellent cladding quality, with a single-layer cladding thickness of 0.4~2 mm. Thicker coatings can also be prepared using multi-layer cladding.

[0011] Preferably, the laser cladding process parameters are: laser power 3.6 kW, scanning speed 8 mm / s, overlap rate 50%, powder feeding rate 10 g / min, and a circular spot with a diameter of 4 mm.

[0012] This invention provides a post-treatment method for laser-clad conductive and wear-resistant copper-based medium-entropy alloy coatings on copper surfaces. The method involves aging the laser-clad coating at a temperature of 350–450 °C for 36–60 h. After aging, a large amount of nanoscale NiMn ordered phases precipitate on the α-Cu matrix, achieving a hardness of 400–553 HV. 0.5 Its conductivity exceeds 30% IACS.

[0013] Preferably, the aging treatment temperature is 400 ℃ and the aging time is 48 h.

[0014] This invention provides applications of the aforementioned copper-based medium-entropy alloy coating, which is used for current-carrying and wear-resistant modification of copper components in electrical engineering, seawater erosion prevention of copper components in marine equipment, and wear-resistant strengthening of high-heat-dissipation copper components in the metallurgical and chemical industries.

[0015] Compared with the prior art, the present invention has the following technical effects:

[0016] (1) In the conventional red laser cladding process on the surface of cold copper plates, this invention found that Cu-Mn binary alloy coatings can improve the poor coating formability caused by the high reflectivity of the copper substrate. However, Cu-Mn coatings with Mn added alone are prone to a large number of pore defects formed by Mn deoxidation and slag formation. Further research found that adding Ni, which is infinitely miscible with Cu, to this system can significantly improve the coating's feeding performance. Ultimately, it is possible to obtain Cu coatings with excellent forming quality, free of pores and cracks, and with good metallurgical bonding with the copper substrate by direct cladding without any pretreatment of the bright copper surface. (100-2x) Ni x Mn x (x=20~30) Copper-based medium-entropy alloy coating, the cladding quality fully meets the requirements for direct industrial applications.

[0017] (2) This study found that when the Ni and Mn contents are both below 15 wt.%, the coating does not exhibit a significant age-hardening effect, and the maximum hardness is below 300 HV. However, when the Ni and Mn contents are controlled within the range of 20-30 wt.%, under the combined effect of the medium entropy effect and rapid laser solidification, the coating still mainly consists of a simple α-Cu solid solution phase after solidification. After aging treatment at 350-450 ℃, a large number of nano-sized NiMn ordered phases precipitate in the α-Cu matrix of the coating, significantly enhancing the age-hardening effect, and the maximum hardness can reach 400-553 HV. 0.5This coating exhibits extremely high hardness among currently reported high-strength copper alloys. Eddy current conductivity testing of the 0.5 mm thick coating along with the copper substrate showed a conductivity >30% IACS, achieving a synergistic improvement in coating hardness, wear resistance, and conductivity. Furthermore, the coating's thermophysical properties are similar to the substrate's, which helps mitigate the tendency for the coating to peel off and crack during thermal cycling. Attached Figure Description

[0018] Figure 1 This is the macroscopic morphology of the surface after multiple coating layers are clad in Embodiment 1 of the present invention;

[0019] Figure 2 SEM tissue analysis and energy dispersive spectroscopy line scanning at the interface of Embodiment 1 of the present invention;

[0020] Figure 3 This is the macroscopic surface morphology of a single-pass coating after cladding in Comparative Example 1 of the present invention;

[0021] Figure 4 This is the macroscopic surface morphology of a single-pass coating after cladding in Comparative Example 2 of the present invention;

[0022] Figure 5 This is the macroscopic surface morphology of the single-pass coating after cladding in Comparative Example 3 of the present invention;

[0023] Figure 6 This is the macroscopic morphology of the surface after single-pass coating cladding in Embodiment 1 of the present invention;

[0024] Figure 7 This is the macroscopic morphology of the surface after single-pass coating cladding in Embodiment 2 of the present invention;

[0025] Figure 8 This is the macroscopic surface morphology of the single-pass coating after cladding in Comparative Example 4 of the present invention;

[0026] Figure 9 The TEM microstructure and L-type microstructure of the coating after aging at 400 °C for 48 h in Example 3 of this invention are shown. 10 -Electron diffraction spots of NiMn nanoprecipitates;

[0027] Figure 10 The macroscopic morphology of the surface after single-pass coating cladding in Examples 6-8 of the present invention is shown. Detailed Implementation

[0028] The following examples further illustrate a conductive, wear-resistant, medium-entropy alloy coating for laser cladding on copper surfaces and its preparation method, but the scope of protection of the present invention is not limited to the examples.

[0029] Example 1

[0030] This embodiment uses the following method to prepare a conductive and wear-resistant copper-based medium-entropy alloy coating on a copper surface by laser cladding. Table 1 shows the composition of Examples 1-5 and Comparative Examples 1-4. Each component was prepared by weight percentage using elemental spherical metal powder with a purity ≥99.9 wt.%. All samples were prepared by direct cladding on a pure copper cold substrate under argon protection using the same cladding process and conventional red laser synchronous powder feeding method. The cladding process parameters were: laser power 3.6 kW, scanning speed 8 mm / s, circular spot diameter 4 mm, and overlap rate 50%. The heat treatment process after coating cladding was isothermal aging at 400 ℃ for 48 h.

[0031] Figure 1 The figure shown is Cu, the component of Example 1. 50 Ni 25 Mn 25 The surface morphology of the multi-layer coating after cladding is approximately 1 mm thick. The macroscopic morphology is smooth, without obvious undulations, bumps, or visible defects. The overlapping boundaries of the multiple layers are clear and straight. After polishing the surface with a handheld grinder, there are no defects such as pores, which fully meet the requirements of industrial applications for cladding quality. Figure 2 The image shows the SEM structure and energy dispersive spectroscopy results at the coating interface. It can be seen that there is a clear gradient of Cu, Ni and Mn elemental composition in the interface region between the coating and the substrate, indicating that the coating and the substrate have formed a reliable metallurgical bond. Figures 3-5 The images show the macroscopic surface morphology of single-layer coatings after cladding in Comparative Examples 1 to 3, respectively. The images also show the differences between pure Cu in Comparative Example 1 and Cu in Comparative Example 2. 75 Ni 25 The coatings were difficult to clad and form, making it impossible to obtain continuous coatings. Adding Mn significantly improved the formability of the cladding layer, as seen in Comparative Example 3 with Cu. 70 Mn 25 The coating already exhibited continuity, but noticeable porosity remained on the surface, failing to meet engineering application requirements. Further addition of Ni resulted in excellent, continuous, defect-free coatings in Examples 1-5. Typical surface morphologies are shown below. Figure 6 and Figure 7 As shown in Examples 1 and 2, Cu 50 Ni 25 Mn 25 and Cu 60 Ni 20 Mn 20 The components are all continuously and coherently combined, and the coating has no pore defects on the surface, resulting in excellent cladding quality. However, Figure 8 Comparative Example 4, Component Cu 70 Ni 15 Mn 15 The peeling of a single coating layer indicates that the addition of Ni and Mn elements must be higher than 20 wt.% to achieve effective metallurgical bonding between the coating and the copper substrate and to obtain excellent cladding quality.

[0032] Table 1 shows the surface hardness and conductivity results before and after aging of the coating surface after multiple cladding passes, polished to a thickness of 0.5 mm. When measuring conductivity using a 7501A eddy current conductivity meter, the copper substrate was not removed to ensure the measurement results were consistent with the actual operating conditions where the substrate was retained. It can be seen that the Cu in Comparative Example 4... 70 Ni 15 Mn 15 After aging, the hardness of the coating is close to that of the solidified state, at only 223 HV. 0.5 The component of this invention is Cu. (100-2x) Ni x Mn x Examples 1-5 within the protection range (x=20~30) not only exhibited excellent cladding quality but also achieved significant age-hardening effects, with post-aging hardness ranging from 400 to 553 HV. 0.5 Between these values, the conductivity all exceeded 30% IACS. Figure 9 The image shown is a TEM image of the coating in Example 1 after aging at 400°C for 48 hours. The results indicate that the increase in Ni and Mn content promotes L 10 - The ordered NiMn nanophase precipitates in large quantities from the α-Cu solid solution matrix, which not only achieves the strengthening effect of nanophase precipitation, but also reduces the amount of Ni and Mn elements in the matrix, thus achieving a simultaneous improvement in coating hardness and conductivity.

[0033] Table 1. Hardness and conductivity of the components and aging processes in the examples and comparative examples.

[0034]

[0035] Example 2

[0036] Tables 2 and 3 respectively show the effects of changes in laser parameters and aging process on Cu in Example 1. 50 Ni 25 Mn 25 The effects of composition on hardness, conductivity, and cladding quality after aging were investigated. All metal powders used in the experiments were elemental spherical powders with a purity ≥99.9 wt.%, prepared according to the corresponding weight percentages. All samples were directly clad onto cold pure copper substrates using a conventional red laser synchronous powder feeding method under an argon protective atmosphere. Table 2 shows that after aging at 400℃ for 48 h with different laser process parameters, the coatings exhibited a hardness greater than 500 HV and a conductivity greater than 30% IACS. Figure 10 The table shows the macroscopic surface morphology of the single-pass coating after cladding in Examples 6-8. Within the process parameters defined by this invention, the coatings in each example are well-formed, without obvious defects such as cracks, peeling, or porosity. Table 3 shows that Cu prepared using the same cladding process... 50Ni 25 Mn 25 Within the range of different aging temperatures and time parameters defined in this invention, the coatings all achieve performance indicators such as hardness greater than 500 HV and conductivity greater than 30% IACS.

[0037] Table 2. Effects of different laser cladding process parameters on coating performance

[0038]

[0039] Table 3. Effects of different aging heat treatment process parameters on Cu 50 Ni 25 Mn 25 Influence of coating performance

[0040]

Claims

1. A surface laser-clad conductive and wear-resistant copper-based medium-entropy alloy coating, characterized in that: The chemical composition of the coating, by mass percentage, is 20-30 wt.% Mn, 20-30 wt.% Ni, and 40-60 wt.% Cu.

2. The method for preparing a conductive and wear-resistant copper-based medium-entropy alloy coating by laser cladding on a copper surface according to claim 1, characterized in that: The copper plate surface is directly clad using conventional red laser coaxial powder feeding. The cladding process parameters are: laser power 3.2~4.5 kW, scanning speed 2~12 mm / s, overlap rate 45~65%, powder feeding rate 5~15 g / min; the laser spot is a circular spot with a diameter of 3~5 mm or a broadband spot with a diameter of 10~12 mm.

3. The method for preparing a conductive and wear-resistant copper-based medium-entropy alloy coating by laser cladding on a copper surface according to claim 2, characterized in that, The coating is prepared by multi-layer cladding.

4. The method for preparing a conductive and wear-resistant copper-based medium-entropy alloy coating by laser cladding on a copper surface according to claim 2, characterized in that, The thickness of a single layer of the coating is 0.4~2 mm.

5. The method for preparing a conductive and wear-resistant copper-based medium-entropy alloy coating by laser cladding on a copper surface according to claim 2, characterized in that, After aging at 350~450 ℃ for 36~60 h, the coating phase structure consists of a large number of nano-sized NiMn ordered phases precipitated on an α-Cu matrix, and the aged hardness exceeds 400 HV. 0.5 Conductivity greater than 30% IACS.

6. The application of the conductive and wear-resistant copper-based medium-entropy alloy coating laser cladding on copper surfaces according to claim 1, characterized in that, The coating is used for current-carrying and wear-resistant modification of the surface of copper components in electrical engineering.

7. The application of the conductive and wear-resistant copper-based medium-entropy alloy coating laser cladding on copper surfaces according to claim 1, characterized in that, The coating is used to protect the surface of copper parts in ships and marine equipment from seawater abrasion.

8. The application of the conductive and wear-resistant copper-based medium-entropy alloy coating laser cladding on copper surfaces according to claim 1, characterized in that, The coating is used to enhance the wear resistance of high-heat-dissipation copper components in the metallurgical and chemical industries.

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