Method for reducing crack defects in a nickel-based cladding layer formed on an aluminum-based substrate surface

Abstract

The application provides a method for reducing crack defects in a nickel-based cladding layer formed on the surface of an aluminum base, belonging to the technical field of laser cladding. The method comprises: forming a transition layer on the surface of the aluminum base by laser cladding, and then forming a nickel-based cladding layer on the surface of the transition layer. The surface roughness Ra of the aluminum base is 1-3 microns; the first raw material is used to form the transition layer, the first raw material comprises silver powder and copper powder, and the mass ratio of the silver powder and the copper powder in the first raw material is 25-30% and 70-75% respectively; the second raw material is used to form the nickel-based cladding layer, and the second raw material comprises nickel powder or / and nickel-based alloy powder. The method provided by the application can effectively reduce the crack defects in the nickel-based cladding layer formed on the surface of the aluminum base, and the bonding strength between the aluminum base and the transition layer and between the transition layer and the nickel-based cladding layer is relatively high, so that the aluminum base can be effectively endowed with high wear resistance, hardness, corrosion resistance and high temperature resistance.

Description

Technical Field

[0001] This application relates to the field of laser cladding technology, and more specifically, to a method for reducing crack defects in a nickel-based cladding layer formed on the surface of an aluminum substrate. Background Technology

[0002] Aluminum (including pure aluminum and aluminum alloys) is widely used in aerospace, rail transportation, automotive, shipbuilding, and chemical industries due to its high specific strength, high specific stiffness, good plasticity, and ease of machining. However, aluminum also has certain drawbacks; its wear resistance, corrosion resistance, and high-temperature resistance are relatively poor. Therefore, surface modification of aluminum is necessary to improve these properties.

[0003] In existing technologies, electroplating, spraying, and other techniques are commonly used to form coatings on the surface of aluminum materials to modify the surface. However, these methods often result in low bonding strength between the coating and the aluminum surface, and poor coating density, which limits the improvement of the wear resistance, corrosion resistance, and high-temperature resistance of aluminum materials.

[0004] Laser cladding, as an advanced surface treatment technology, involves applying a cladding material to the substrate surface and then melting the cladding material using a high-energy-density laser beam, resulting in a metallurgical bond between the cladding layer and the substrate. Laser cladding technology can significantly improve the quality of the coating formed on the substrate surface, thereby extending the service life of components.

[0005] Nickel and nickel-based alloys possess high hardness, good corrosion resistance, and excellent high-temperature resistance. Therefore, laser cladding to form a nickel-based coating on aluminum surfaces helps improve the hardness, wear resistance, corrosion resistance, and high-temperature resistance of aluminum. However, during the formation of the nickel-based cladding layer on aluminum surfaces, aluminum and nickel easily mix to form a large number of brittle intermetallic compound phases. This results in numerous cracks within the nickel-based cladding layer, severely reducing its service performance and even causing it to peel off directly after cladding. Consequently, it fails to effectively impart high wear resistance, hardness, corrosion resistance, and high-temperature resistance to the aluminum. Summary of the Invention

[0006] The purpose of this application is to provide a method for reducing crack defects in a nickel-based cladding layer formed on the surface of an aluminum substrate, which aims to reduce crack defects in the nickel-based cladding layer formed on the surface of an aluminum substrate.

[0007] This application provides a method for reducing crack defects in a nickel-based cladding layer formed on the surface of an aluminum substrate. The method includes: forming a transition layer on the surface of an aluminum substrate using laser cladding, and then forming a nickel-based cladding layer on the surface of the transition layer. The surface roughness Ra of the aluminum substrate is 1-3 μm; the transition layer is formed using a first raw material, which includes silver powder and copper powder, with the silver powder and copper powder accounting for 25-30% and 70-75% of the first raw material by mass, respectively; the nickel-based cladding layer is formed using a second raw material, which includes nickel powder and / or nickel-based alloy powder.

[0008] When forming a transition layer on an aluminum substrate using laser cladding, a surface roughness Ra of 1-3 μm effectively reduces the reflectivity of the aluminum substrate to the laser, improves the utilization rate of laser energy, and facilitates the rapid formation of a molten pool on the surface of the aluminum substrate, thus promoting the rapid melting of the first raw material. Furthermore, a surface roughness Ra of 1-3 μm also facilitates better wetting and spreading of the molten first raw material on the surface of the aluminum substrate. The first raw material comprises 25-30 wt% silver powder and 70-75 wt% copper powder, which effectively lowers the melting point of the first raw material, allowing it to remain liquid for a longer period after melting. This improves the fluidity of the molten first raw material, further enhancing its wetting and spreading effect on the surface of the aluminum substrate, improving the cladding formation effect of the transition layer, increasing its density, reducing defects within the transition layer, and increasing the bonding strength between the transition layer and the aluminum substrate.

[0009] In addition, the first raw material, which includes 25-30 wt% silver powder and 70-75 wt% copper powder, can effectively lower the melting point of the transition layer. When the nickel-based cladding layer is formed, it can quickly form a molten pool on the surface of the transition layer, which is conducive to the rapid melting of the second raw material. It is also conducive to the better wetting and spreading of the molten, viscous second raw material on the transition layer, which can improve the forming effect of the nickel-based cladding layer, increase the density of the nickel-based cladding layer, and reduce defects in the nickel-based cladding layer. It can also reduce the formation of intermetallic compound phases at the interface between the transition layer and the nickel-based cladding layer, which can effectively reduce crack defects at the interface between the transition layer and the nickel-based cladding layer. Furthermore, during the formation of the nickel-based cladding layer, since nickel and silver, as well as nickel and copper, form solid solutions rather than brittle intermetallic compound phases, the generation of brittle phases can be effectively suppressed, greatly reducing the conditions for crack formation in the nickel-based cladding layer. This can effectively reduce crack defects in the nickel-based cladding layer formed on the surface of the aluminum substrate, improve the bonding strength between the nickel-based cladding layer and the transition layer, and effectively impart high wear resistance, hardness, corrosion resistance, and high temperature resistance to the aluminum substrate.

[0010] In an optional embodiment of this application, the surface roughness Ra of the aluminum substrate is 1.2-1.7 μm.

[0011] The above technical solution is beneficial to further reduce the reflectivity of the aluminum substrate to the laser, thereby further improving the utilization rate of the aluminum substrate to the laser energy, and thus enabling the rapid formation of a molten pool on the surface of the aluminum substrate; it is also beneficial to further enable the first raw material after melting to quickly wet and spread on the surface of the aluminum substrate, thereby further improving the cladding forming effect of the transition layer.

[0012] In an optional embodiment of this application, the method for preparing the aluminum substrate includes: reciprocating scanning of the surface of the aluminum material using a near-infrared laser beam; wherein, during the reciprocating scanning, the laser power of the near-infrared laser beam is 10-40W, and the frequency of the reciprocating scanning is 20-100Hz.

[0013] The above technical solution can result in a high roughness of the aluminum substrate, giving the surface of the aluminum substrate a "micro-texture" structure. This can effectively reduce the reflectivity of the aluminum substrate to laser, improve the utilization rate of laser energy, and help the surface of the aluminum substrate to quickly form a molten pool, which in turn facilitates the rapid melting of the first raw material. It also helps the molten first raw material to better wet and spread on the surface of the aluminum substrate, improving the cladding effect of the transition layer.

[0014] In an optional embodiment of this application, during reciprocating scanning, the focal point of the near-infrared laser beam is located on the surface of the aluminum material; and at the focal point, the spot of the near-infrared laser beam is a circular spot with a diameter of 0.01-0.05 mm.

[0015] The above technical solution can effectively change the surface roughness of aluminum materials to prepare an aluminum matrix with high surface roughness.

[0016] In optional embodiments of this application, the laser beams used to form the transition layer and the nickel-based cladding layer are both near-infrared laser beams; and the laser power of the near-infrared laser beams is independently 1.5-4.5kW when forming the transition layer and the nickel-based cladding layer.

[0017] In the above technical solution, when forming the transition layer, the laser power of the near-infrared laser beam is 1.5-4.5kW, which can rapidly melt the surface of the aluminum substrate to form a molten pool. It also helps to rapidly expand the molten pool so that more of the first raw material can be melted quickly, and the melted first raw material can remain liquid for a longer period of time, improving the fluidity of the melted first raw material and thus improving the cladding forming effect of the transition layer. When forming the nickel-based cladding layer, the laser power of the near-infrared laser beam is 1.5-4.5kW, which can rapidly melt the surface of the transition layer to form a molten pool. It also helps to rapidly expand the molten pool so that more of the second raw material can be melted quickly, and the melted second raw material can remain liquid for a longer period of time, improving the fluidity of the melted, viscous second raw material and thus improving the forming effect of the nickel-based cladding layer.

[0018] In an optional embodiment of this application, during the formation of the transition layer and the nickel-based cladding layer, the scanning rate of the near-infrared laser beam relative to the aluminum substrate is independently 1-10 m / min.

[0019] The above technical solutions help to further improve the cladding forming effect of the transition layer and the nickel-based cladding layer.

[0020] In an optional embodiment of this application, a powder feeder is used to transfer the first raw material and the second raw material; and when transferring the first raw material and the second raw material, the rotation speed of the powder feeder is independently 0.5-3 r / min.

[0021] The above technical solutions help to further improve the cladding forming effect of the transition layer and the nickel-based cladding layer.

[0022] In an optional embodiment of this application, the first raw material and the second raw material are each independently spherical powders, and the particle size of the first raw material and the particle size of the second raw material are each independently 40-105 μm.

[0023] The above technical solution helps the first and second raw materials to melt rapidly during laser cladding.

[0024] In an optional embodiment of this application, the first raw material is treated by the following method before laser cladding: silver powder and copper powder are mixed and then dried.

[0025] Optionally, vacuum heating drying may be used as the first drying method.

[0026] Optionally, the temperature of the first drying is 80-120℃, and the drying time is 300-420 min.

[0027] Alternatively, ball milling can be used as the mixing method.

[0028] Optionally, the ball-to-material ratio during the ball milling process is (2-4):1.

[0029] Optionally, the ball milling speed is 220-280 r / min.

[0030] Optionally, the ball milling mixing time is 300-420 min.

[0031] Optionally, ball milling and mixing are carried out under inert gas protection.

[0032] In an optional embodiment of this application, the second raw material is treated by the following method before laser cladding: the second raw material is subjected to a second drying process.

[0033] Optionally, vacuum heating drying can be used as the second drying method.

[0034] Optionally, the temperature of the second drying is 80-120℃, and the time of the second drying is 300-420 min. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 A process flow diagram for reducing crack defects in the nickel-based cladding layer formed on the surface of an aluminum substrate, provided in this application.

[0037] Figure 2 This is a three-dimensional confocal characterization image of the surface of the aluminum plate used in step (2) of the embodiment of this application.

[0038] Figure 3 This is a three-dimensional confocal characterization image of the surface of the aluminum substrate obtained in step (2) of the embodiment of this application.

[0039] Figure 4 This is a physical image of the sample obtained in step (6) of the embodiment of this application.

[0040] Figure 5 This is a cross-sectional morphology diagram of the sample obtained in step (6) of the embodiment of this application.

[0041] Figure 6 This is a physical image of the sample obtained in step (3) of Comparative Example 1 of this application.

[0042] Figure 7 This is a cross-sectional morphology diagram of the sample obtained in step (3) of Comparative Example 1 of this application.

[0043] Figure 8 This is a physical image of the sample obtained in step (3) of Comparative Example 2 of this application.

[0044] Figure 9 This is a cross-sectional morphology diagram of the sample obtained in step (3) of Comparative Example 2 of this application.

[0045] Figure 10 This is an indentation map of the nickel-based cladding layer region 1 of the sample obtained in step (6) of the embodiment of this application.

[0046] Figure 11 This is an indentation map of the nickel-based cladding layer region 2 of the sample obtained in step (6) of the embodiment of this application.

[0047] Figure 12This is an indentation map of the nickel-based cladding layer region 3 of the sample obtained in step (6) of the embodiment of this application.

[0048] Figure 13 This is an indentation map of the nickel-based cladding layer region 4 of the sample obtained in step (6) of the embodiment of this application.

[0049] Figure 14 This is an indentation map of the nickel-based cladding layer region 5 of the sample obtained in step (6) of the embodiment of this application. Detailed Implementation

[0050] The inventors discovered that when preparing a nickel-based cladding layer on an aluminum substrate using laser cladding technology, nickel and aluminum elements easily mix to form a large number of brittle intermetallic compound phases. This results in numerous cracks within the nickel-based cladding layer, affecting its service performance and, in severe cases, causing the nickel-based cladding layer to detach from the aluminum substrate. Consequently, it fails to effectively impart high wear resistance, hardness, corrosion resistance, and high-temperature resistance to the aluminum substrate. Furthermore, the high viscosity of molten nickel or nickel alloys hinders wetting and spreading on the aluminum substrate surface, leading to poor cladding formation of the nickel-based cladding layer.

[0051] To address the aforementioned problems, this application provides a method for reducing crack defects in a nickel-based cladding layer formed on the surface of an aluminum substrate. The method includes: forming a transition layer on the surface of an aluminum substrate using laser cladding, and then forming a nickel-based cladding layer on the surface of the transition layer. The surface roughness Ra of the aluminum substrate is 1-3 μm; the transition layer is formed using a first raw material, comprising silver powder and copper powder, with the silver powder and copper powder accounting for 25-30% and 70-75% of the first raw material by mass, respectively; the nickel-based cladding layer is formed using a second raw material, comprising nickel powder and / or nickel-based alloy powder.

[0052] In this application, aluminum substrate refers to a substrate whose material is mainly aluminum. This application does not limit the shape or structure of the aluminum substrate. For example, the shape of the aluminum substrate can be plate-shaped, etc.

[0053] As an example, the surface roughness Ra of the aluminum substrate can be any value among 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.7 μm, 2 μm, 2.2 μm, 2.5 μm, 2.7 μm, and 3 μm, or a range between any two; the mass percentage of silver powder in the first raw material can be any value among 25%, 25.5%, 26%, 27%, 27.5%, 28%, 28.5%, 29%, and 30%, or a range between any two; the mass percentage of copper powder in the first raw material can be any value among 70%, 70.5%, 71%, 71.5%, 72%, 72.5%, 73%, 74%, 74.5%, and 75%, or a range between any two.

[0054] In this application, when a transition layer is formed by laser cladding on the surface of an aluminum substrate, the surface roughness Ra of the aluminum substrate is 1-3 μm, which can give the surface of the aluminum substrate a "micro-texture" structure. This can effectively reduce the reflectivity of the aluminum substrate to the laser, improve the utilization rate of the laser energy of the aluminum substrate, and help the surface of the aluminum substrate to quickly form a molten pool, which in turn facilitates the rapid melting of the first raw material. In addition, the surface roughness Ra of the aluminum substrate is 1-3 μm, which also facilitates better wetting and spreading of the molten first raw material on the surface of the aluminum substrate.

[0055] The first raw material includes 25-30 wt% silver powder and 70-75 wt% copper powder, which can effectively lower the melting point of the first raw material, making its melting point near the eutectic point of copper and nickel (only about 780℃). This is beneficial for the first raw material to remain in a liquid state for a longer period of time after melting, which can improve the fluidity of the first raw material after melting. It also helps the first raw material to better wet and spread on the surface of the aluminum substrate, improve the cladding forming effect of the transition layer, increase the density of the transition layer, reduce defects in the transition layer, and improve the bonding strength between the transition layer and the aluminum substrate.

[0056] Since the first raw material forming the transition layer includes 25-30 wt% silver powder and 70-75 wt% copper powder, the melting point of the transition layer can be effectively reduced. During the formation of the nickel-based cladding layer, the surface of the transition layer melts rapidly to form a molten pool, which facilitates the rapid melting of the second raw material. This also allows the molten, more viscous second raw material to better wet and spread on the transition layer, improving the forming effect and density of the nickel-based cladding layer, reducing defects within the nickel-based cladding layer, and increasing the bonding strength between the nickel-based cladding layer and the transition layer. The rapid formation of a molten pool on the surface of the transition layer also reduces the formation of intermetallic compound phases at the interface between the transition layer and the nickel-based cladding layer, effectively reducing crack defects at the interface. Furthermore, during the formation of the nickel-based cladding layer, since nickel and silver, as well as nickel and copper, form solid solutions rather than brittle intermetallic compound phases, the generation of brittle phases is effectively suppressed, significantly reducing the conditions for crack formation in the nickel-based cladding layer.

[0057] Therefore, the method for reducing crack defects in the nickel-based cladding layer formed on the surface of an aluminum substrate provided in this application can effectively reduce crack defects in the nickel-based cladding layer formed on the surface of an aluminum substrate, and the bonding strength between the transition layer and the aluminum substrate and the bonding strength between the nickel-based cladding layer and the transition layer are both high, which can effectively impart high wear resistance, hardness, corrosion resistance and high temperature resistance to the aluminum substrate.

[0058] Figure 1For a process flow diagram provided in this application for reducing crack defects in the nickel-based cladding layer formed on the surface of an aluminum substrate, please refer to [link / reference needed]. Figure 1 The preparation method includes the following steps:

[0059] S10, Prepare the first raw material and the second raw material; wherein, the first raw material includes silver powder and copper powder, and the mass percentages of silver powder and copper powder in the first raw material are 25-30% and 70-75%, respectively; the second raw material includes nickel powder and / or nickel-based alloy powder.

[0060] In some optional embodiments of this application, the first raw material is a spherical powder with a particle size of 40-105 μm; this facilitates rapid melting of the first raw material during laser cladding to form a transition layer.

[0061] In this application, the first raw material is spherical powder, which does not necessarily mean that the first raw material is a standard sphere, but can also mean that the shape of the first raw material can be quasi-spherical.

[0062] As an example, the particle size of the first raw material can be any value among 40μm, 50μm, 60μm, 75μm, 90μm, 100μm and 105μm or any value between the two.

[0063] In some optional embodiments of this application, the first raw material is treated by the following method before laser cladding: silver powder and copper powder are mixed and then dried.

[0064] In some optional embodiments of this application, the first drying method is vacuum heating drying.

[0065] Further, the temperature of the first drying is 80-120°C, and the time of the first drying is 300-420 min. As an example, the temperature of the first drying can be any value among 80°C, 85°C, 90°C, 95°C, 100°C, 110°C, and 120°C, or a range between any two; the time of the first drying can be any value among 300 min, 320 min, 340 min, 360 min, 380 min, 400 min, and 420 min, or a range between any two.

[0066] In some optional embodiments of this application, ball milling is used to mix the silver powder and copper powder, which can make the substances in the first raw material evenly mixed.

[0067] As an example, the ball-to-material ratio in the ball milling process is (2-4):1, for example, any one of the following values ​​or a range between any two: 2:1, 2.5:1, 3:1, 3.5:1 and 4:1.

[0068] As an example, the ball milling speed is 220-280 r / min. For example, the ball milling speed can be any value among 220 r / min, 230 r / min, 240 r / min, 250 r / min, 260 r / min, 270 r / min and 280 r / min or any range between two.

[0069] As an example, the ball milling time is 300-420 min. For example, the ball milling time can be any value among 300 min, 320 min, 340 min, 360 min, 380 min, 400 min and 420 min or any range between two of them.

[0070] In some optional embodiments of this application, ball milling is carried out under an inert gas atmosphere. As an example, the inert gas used during ball milling is argon or nitrogen, etc.

[0071] In this application, the second raw material includes nickel powder and / or nickel-based alloy powder. It should be noted that this application does not limit the specific material of the nickel-based alloy powder, as long as the nickel-based alloy powder is mainly composed of nickel.

[0072] In some optional embodiments of this application, the second raw material is a spherical powder with a particle size of 40-105 μm; the second raw material can melt rapidly when laser cladding forms a nickel-based cladding layer.

[0073] In this application, the second raw material is spherical powder, which does not necessarily mean that the second raw material is a standard sphere, but can also mean that the shape of the second raw material can be quasi-spherical.

[0074] As an example, the particle size of the second raw material can be any value among 40μm, 50μm, 60μm, 75μm, 90μm, 100μm and 105μm or any range between the two.

[0075] In some optional embodiments of this application, the second raw material is treated by the following method before laser cladding: the second raw material is subjected to a second drying process.

[0076] Furthermore, the second drying method is vacuum heating drying.

[0077] In some optional embodiments of this application, the second drying temperature is 80-120°C, and the second drying time is 300-420 min. As an example, the second drying temperature can be any value among 80°C, 85°C, 90°C, 95°C, 100°C, 110°C, and 120°C, or a range between any two; the second drying time can be any value among 300 min, 320 min, 340 min, 360 min, 380 min, 400 min, and 420 min, or a range between any two.

[0078] S20, Prepare an aluminum substrate; wherein the surface roughness Ra of the aluminum substrate is 1-3 μm.

[0079] In some optional embodiments of this application, the method for preparing the aluminum substrate includes: reciprocating scanning of the surface of the aluminum material using a near-infrared laser beam; wherein, during the reciprocating scanning, the laser power of the near-infrared laser beam is 10-40W, and the frequency of the reciprocating scanning is 20-100Hz.

[0080] The above method can result in a higher roughness of the aluminum substrate, giving the surface of the aluminum substrate a "micro-texture" structure. This can effectively reduce the reflectivity of the aluminum substrate to laser, improve the utilization rate of laser energy, and help the surface of the aluminum substrate to melt quickly to form a molten pool. This, in turn, facilitates the rapid melting of the first raw material. It also helps the molten first raw material to better wet and spread on the surface of the aluminum substrate, improving the cladding effect of the transition layer.

[0081] As an example, the laser power of the near-infrared laser beam can be any value among 10W, 15W, 20W, 25W, 30W, 35W and 40W or any value between the two; the reciprocating scanning frequency can be any value among 20Hz, 30Hz, 45Hz, 50Hz, 60Hz, 75Hz, 90Hz and 100Hz or any value between the two.

[0082] Furthermore, during reciprocating scanning, the focal point of the near-infrared laser beam is located on the surface of the aluminum material; and at the focal point, the spot of the near-infrared laser beam is a circular spot with a diameter of 0.01-0.05 mm. This is beneficial for effectively changing the surface roughness of the aluminum material, thereby preparing an aluminum substrate with a high surface roughness.

[0083] In this application, the spot of the near-infrared laser beam at the focal point is a circular spot. This does not necessarily mean that the shape of the spot is a standard circle, but it can also mean that the shape of the spot is approximately circular.

[0084] As an example, at the focal point, the diameter of the near-infrared laser beam spot can be any value among 0.01mm, 0.015mm, 0.02mm, 0.025mm, 0.03mm, 0.035mm, 0.04mm, and 0.05mm, or any value in between.

[0085] As an example, in the embodiments of this application, the reciprocating scan is a reciprocating linear scan mode.

[0086] Furthermore, in some optional embodiments of this application, the method for preparing the aluminum substrate further includes: removing the oxide film and oil stains on the surface of the aluminum material before reciprocating scanning of the surface of the aluminum material using a near-infrared laser beam, and then drying the aluminum material.

[0087] For example, an abrasive wheel can be used to grind off the oxide film on the surface of the aluminum material; alcohol and acetone can be used to clean the surface of the aluminum material to remove oil and other contaminants.

[0088] It should be noted that in other feasible embodiments, the aluminum substrate may not be prepared in the above manner, or other methods may be used to prepare the aluminum substrate, as long as the surface roughness Ra of the prepared aluminum substrate is 1-3 μm.

[0089] In some optional embodiments of this application, the surface roughness Ra of the aluminum substrate is 1.2-1.7 μm; this is beneficial to further reduce the reflectivity of the aluminum substrate to the laser, thereby further improving the utilization rate of the laser energy of the aluminum substrate, and thus enabling the surface of the aluminum substrate to melt rapidly to form a molten pool; it is also beneficial to further enable the first raw material after melting to quickly wet and spread on the surface of the aluminum substrate, thereby further improving the cladding forming effect of the transition layer.

[0090] S30 uses laser cladding to form a transition layer on the surface of an aluminum substrate; wherein, the transition layer is formed using a first raw material.

[0091] In some optional embodiments of this application, the laser beam used to form the transition layer is a near-infrared laser beam.

[0092] In this application, near-infrared laser beam refers to a laser beam with a wavelength of 780-2526nm.

[0093] Furthermore, when forming the transition layer, the laser power of the near-infrared laser beam is 1.5-4.5kW; this allows the surface of the aluminum substrate to melt rapidly to form a molten pool, and also helps to rapidly expand the molten pool so that more of the first raw material can melt quickly, and allows the molten first raw material to remain liquid for a longer period of time, improving the fluidity of the molten first raw material and thus improving the cladding forming effect of the transition layer.

[0094] As an example, when forming the transition layer, the laser power of the near-infrared laser beam can be any value among 1.5kW, 2kW, 2.5kW, 3kW, 3.5kW, 4kW, and 4.5kW, or any value in between.

[0095] In some optional embodiments of this application, during the formation of the transition layer, the scanning rate of the near-infrared laser beam relative to the aluminum substrate is 1-10 m / min; this helps to further improve the forming effect of the transition layer.

[0096] As an example, during the formation of the transition layer, the scanning rate of the near-infrared laser beam relative to the aluminum substrate can be any value among 1 m / min, 2 m / min, 3 m / min, 5 m / min, 6 m / min, 7 m / min, 8 m / min, 9 m / min and 10 m / min or any value between the two.

[0097] In some optional embodiments of this application, a powder feeder is used to transfer the first raw material, and the rotation speed of the powder feeder is 0.5-3 r / min when transferring the first raw material; this helps to further improve the forming effect of the transition layer.

[0098] As an example, when transferring the first raw material, the rotational speed of the powder feeder can be any value among 0.5 r / min, 1 r / min, 1.5 r / min, 2 r / min, 2.5 r / min, and 3 r / min, or any range between two values. The powder feeding gas is an inert gas, such as argon.

[0099] In some optional embodiments of this application, the process of forming the transition layer is carried out under a protective gas. As an example, the protective gas can be argon, with a flow rate of 20-25 L / min and an overlap ratio of 40-60%.

[0100] S40 uses laser cladding to form a nickel-based cladding layer on the surface of the transition layer; wherein, a second raw material is used to form the nickel-based cladding layer.

[0101] In some optional embodiments of this application, the laser beam used to form the nickel-based cladding layer is a near-infrared laser beam.

[0102] Furthermore, when forming the nickel-based cladding layer, the laser power of the near-infrared laser beam is 1.5-4.5kW; this allows the surface of the transition layer to melt rapidly to form a molten pool, and also helps to rapidly expand the molten pool so that more of the second raw material can melt quickly, and allows the melted second raw material to remain liquid for a longer period of time, thereby improving the fluidity of the melted, viscous second raw material and improving the forming effect of the nickel-based cladding layer.

[0103] As an example, when forming the nickel-based cladding layer, the laser power of the near-infrared laser beam can be any value among 1.5kW, 2kW, 2.5kW, 3kW, 3.5kW, 4kW, and 4.5kW, or any value in between.

[0104] In some optional embodiments of this application, during the formation of the nickel-based cladding layer, the scanning rate of the near-infrared laser beam relative to the aluminum substrate is 1-10 m / min; this helps to further improve the forming effect of the nickel-based cladding layer.

[0105] As an example, during the formation of the nickel-based cladding layer, the scanning rate of the near-infrared laser beam relative to the aluminum substrate can be any value among 1 m / min, 2 m / min, 3 m / min, 5 m / min, 6 m / min, 7 m / min, 8 m / min, 9 m / min and 10 m / min or any value between the two.

[0106] In some optional embodiments of this application, a powder feeder is used to transfer the first raw material, and when transferring the second raw material, the rotation speed of the powder feeder is 0.5-3 r / min; this helps to further improve the forming effect of the nickel-based cladding layer.

[0107] As an example, when transferring the second raw material, the rotational speed of the powder feeder can be any value among 0.5 r / min, 1 r / min, 1.5 r / min, 2 r / min, 2.5 r / min, and 3 r / min, or any range between two values. The powder feeding gas is an inert gas, such as argon.

[0108] In some optional embodiments of this application, the process of forming the nickel-based cladding layer is carried out under a protective gas. As an example, the protective gas can be argon, with a flow rate of 20-25 L / min and an overlap ratio of 40-60%.

[0109] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0110] Example

[0111] This embodiment provides a method for preparing a nickel-based cladding layer on the surface of an aluminum plate, including the following steps:

[0112] (1) Prepare an aluminum plate with a material size of 100mm×50mm×5mm. Use a grinding wheel to grind off the oxide film on the surface of the aluminum plate. Use alcohol and acetone to clean and remove the oil stains on the surface of the aluminum plate. After drying, fix the aluminum plate at the scanning laser station.

[0113] (2) Set the laser power of the near-infrared laser beam to 20W, the scanning frequency to 50HZ, and adjust the focus of the near-infrared laser beam to the starting position of the surface of the aluminum plate located at the scanning laser station. Set the scanning range, run the program, and obtain an aluminum substrate with a certain surface roughness.

[0114] (3) Mix silver powder and copper powder in a mass ratio of 7:18 by ball milling, and then dry the ball-milled system using a vacuum heating drying oven to obtain the first raw material.

[0115] Both silver and copper powders were spherical powders with a particle size of 40-105 μm. Ball milling was performed under an argon atmosphere at a ball-to-particle ratio of 3:1, at a milling speed of 250 r / min, for a milling time of 360 min. Drying was carried out at 100℃ for 360 min.

[0116] (4) Place the first raw material obtained in step (3) into the powder feeder; the laser used to form the Ag-Cu transition layer by cladding is near-infrared light, the laser power of the near-infrared laser beam is set to 2kW, the scanning rate of the near-infrared laser beam is 3m / min, the transfer of the powder feeder is 1r / min, the blowing gas and the cladding protective gas are both argon, the protective gas flow rate is 20L / min, and the overlap rate is 50%.

[0117] The aluminum substrate obtained in step (2) is fixed at the work station of the laser cladding platform, and the focus of the near-infrared laser beam is adjusted to the starting position on the surface of the aluminum substrate. The protective gas is turned on, the program is run, and an Ag-Cu transition layer is formed on the surface of the aluminum substrate to obtain an intermediate.

[0118] (5) Dry the nickel powder to obtain the second raw material.

[0119] The nickel powder is spherical with a particle size of 40-105 μm; the drying temperature is 100℃ and the drying time is 360 min.

[0120] (6) Place the second raw material obtained in step (5) into the powder feeder; the laser used to form the nickel-based cladding layer is near-infrared light, the laser power of the near-infrared laser beam is set to 2.5kW, the scanning rate of the near-infrared laser beam is 1.5m / min, the transfer rate of the powder feeder is 2r / min, the blowing gas and the cladding protective gas are both argon, the protective gas flow rate is 20L / min, and the overlap rate is 50%.

[0121] The intermediate obtained in step (4) is fixed at the work station of the laser cladding platform, and the focus of the near-infrared laser beam is adjusted to the starting position on the surface of the Ag-Cu transition layer. The protective gas is turned on, the program is run, and a nickel-based cladding layer is formed on the surface of the Ag-Cu transition layer.

[0122] Comparative Example 1

[0123] This comparative example provides a method for preparing a nickel-based cladding layer on the surface of an aluminum plate, comprising the following steps:

[0124] (1) Prepare an aluminum plate with a material size of 100mm×50mm×5mm. Use a grinding wheel to grind off the oxide film on the surface of the aluminum plate. Use alcohol and acetone to clean and remove the oil stains on the surface of the aluminum plate. Blow dry and set aside.

[0125] (2) Dry the nickel powder to obtain laser cladding material.

[0126] The nickel powder is spherical with a particle size of 40-105 μm; the drying temperature is 100℃ and the drying time is 360 min.

[0127] (3) Place the laser cladding material obtained in step (2) into the powder feeder; the laser used to form the nickel-based cladding layer is near-infrared light, the laser power of the near-infrared laser beam is set to 2.4kW, the scanning rate of the near-infrared laser beam is 1.5m / min, the transfer rate of the powder feeder is 2r / min, the blowing gas and the cladding protective gas are both argon, the protective gas flow rate is 20L / min, and the overlap rate is 50%.

[0128] The aluminum plate obtained in step (1) is fixed at the work station of the laser cladding platform, and the focus of the near-infrared laser beam is adjusted to the starting position on the surface of the aluminum plate. The protective gas is turned on, the program is run, and a nickel-based cladding layer is formed on the surface of the aluminum plate.

[0129] Comparative Example 2

[0130] This comparative example provides a method for preparing a nickel-based cladding layer on the surface of an aluminum plate. The difference between this comparative example and Comparative Example 1 is that the laser power in step (3) is 3kW.

[0131] Experimental Example 1

[0132] The surfaces of the aluminum plate used in step (2) of the embodiment (i.e., before laser scanning) and the aluminum substrate obtained in step (2) of the embodiment (i.e. after laser scanning) were respectively subjected to three-dimensional confocal characterization, and the characterization results are as follows: Figure 2 and Figure 3 As shown.

[0133] from Figure 2 and Figure 3The comparison shows that the operation of step (2) in the embodiment can improve the surface roughness of the aluminum plate, so that the surface of the aluminum substrate is micro-textured. The average surface roughness Ra of the aluminum substrate is measured to be 1.5 μm.

[0134] Photographs of the samples obtained in step (6) of the embodiment are collected, such as Figure 4 As shown; and the cross-section of the sample obtained in step (6) of the embodiment was characterized by light microscopy, and the characterization results are as follows. Figure 5 As shown; Figure 5 The scale bar is 1000 μm. Figure 5 Part A in the text refers to: aluminum matrix. Figure 5 Part B in the text refers to the Ag-Cu transition layer. Figure 5 The C part refers to the nickel-based cladding layer.

[0135] from Figure 4 and Figure 5 It can be seen that a smooth and continuous shape is formed on the surface of the aluminum substrate. The Ag-Cu transition layer spreads well on the surface of the aluminum substrate, and the Ag-Cu transition layer and the surface of the aluminum substrate are well bonded. Furthermore, no defects such as cracks are generated within the Ag-Cu transition layer. Similarly, a smooth and continuous shape is formed on the surface of the Ag-Cu transition layer. The nickel-based cladding layer spreads well on the surface of the Ag-Cu transition layer, and the surface of the nickel-based cladding layer and the Ag-Cu transition layer are well bonded. Furthermore, no defects such as cracks are generated within the nickel-based cladding layer.

[0136] Take a photograph of the sample obtained in step (3) of Comparative Example 1, such as Figure 6 As shown; and the cross-section of the sample obtained in step (3) of Comparative Example 1 was characterized by light microscopy, and the characterization results are as follows. Figure 7 As shown; Figure 7 The scale bar is 1000 μm. Figure 7 Part A in the text refers to: aluminum plate. Figure 7 Part B in the text refers to the nickel-based cladding layer.

[0137] from Figure 6 and Figure 7 It can be seen that in the sample prepared in Comparative Example 1, the nickel-based cladding layer spread very poorly on the aluminum plate, and many nickel-based cladding materials did not melt. Multiple cracks occurred inside the nickel-based cladding layer, and some areas even peeled off.

[0138] Photographs of the samples obtained in step (3) of Comparative Example 2 are taken, such as... Figure 8 As shown; and the cross-section of the sample obtained in step (3) of Comparative Example 2 was characterized by optical microscopy, and the characterization results are as follows. Figure 9 As shown; Figure 9 The scale bar is 1000 μm. Figure 9 Part A in the text refers to: aluminum plate. Figure 9 Part B in the text refers to the nickel-based cladding layer.

[0139] from Figure 8 and Figure 9 It can be seen that in the sample prepared in Comparative Example 2, there are still many cracks inside and on the surface of the nickel-based cladding layer.

[0140] Experiment Example 2

[0141] The surface hardness of the sample obtained in step (6) of the embodiment was tested. The test method was as follows: five regions from top to bottom of the nickel-based cladding layer were selected, and indentation treatment was performed on each of the five regions (labeled 1-5). The hardness of each region was tested. The indentation diagrams of the regions labeled 1-5 are shown in the figure below. Figures 10 to 14 As shown, Figures 10 to 14 The scale bar is 10 μm; the hardness of the areas corresponding to labels 1-5 and the surface hardness of the aluminum plate obtained in step (1) of the embodiment are shown in Table 1.

[0142] Table 1

[0143] Hardness (HV) Hardness (HV) Area 1 309.9 Area 4 434.2 Area 2 284.0 Area 5 319.9 Area 3 323.3 Aluminum plate surface 72.0

[0144] from Figures 10 to 14 As can be seen from Table 1, the average hardness of the nickel-based cladding layer exceeds 300 HV, and the highest hardness can reach 434.2 HV, which is far greater than the hardness of the aluminum plate surface of 72.0 HV; indicating that the method of forming a nickel-based cladding layer on the surface of an aluminum plate provided in the embodiments of this application can result in a high surface hardness of the aluminum substrate.

[0145] In summary, the method provided in this application can effectively reduce crack defects in the nickel-based cladding layer formed on the surface of the aluminum substrate, and the bonding strength between the aluminum substrate and the transition layer, as well as between the transition layer and the nickel-based cladding layer, is high, which can effectively endow the aluminum substrate with high wear resistance, hardness, corrosion resistance and high temperature resistance.

[0146] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A method of reducing crack defects in a nickel-based cladding layer formed on a surface of an aluminum-based substrate, characterized by, The application relates to a method for forming a transition layer and a nickel-based cladding layer on the surface of an aluminum substrate by laser cladding. The surface roughness Ra of the aluminum substrate is 1-3 mu m. The transition layer is formed by using a first raw material, the first raw material comprises silver powder and copper powder, and the mass ratio of the silver powder and the copper powder in the first raw material is 25-30% and 70-75% respectively. The nickel-based cladding layer is formed by using a second raw material, the second raw material comprises nickel powder or / and nickel-based alloy powder. The surface roughness Ra of the aluminum substrate is 1.2-1.7 mu m.

2. The method of reducing crack defects in a nickel-based cladding layer formed on an aluminum-based substrate surface according to claim 1, characterized by, The preparation method of the aluminum substrate comprises reciprocating scanning the surface of aluminum material by using a near-infrared laser beam.

3. The method of reducing crack defects in a nickel-based cladding layer formed on an aluminum-based substrate surface according to claim 1, characterized by, During the reciprocating scanning, the laser power of the near-infrared laser beam is 10-40 W, and the frequency of the reciprocating scanning is 20-100 HZ. During the reciprocating scanning, the focal point of the near-infrared laser beam is located on the surface of the aluminum material, and the spot of the near-infrared laser beam at the focal point is a circular spot with a diameter of 0.01-0.05 mm.

4. The method of reducing crack defects in a nickel-based cladding layer formed on an aluminum-based substrate surface according to claim 3, characterized by, The laser beams used for forming the transition layer and the nickel-based cladding layer are both near-infrared laser beams, and the laser power of the near-infrared laser beams used for forming the transition layer and the nickel-based cladding layer is independently 1.5-4.5 kW.

5. The method of reducing crack defects in a nickel-based cladding layer formed on an aluminum-based substrate surface according to any one of claims 1 to 4, characterized in that, During the process of forming the transition layer and the nickel-based cladding layer, the scanning speed of the near-infrared laser beam relative to the aluminum substrate is independently 1-10 m / min.

6. The method of reducing crack defects in a nickel-based cladding layer formed on an aluminum-based substrate surface according to claim 5, characterized by, The first raw material and the second raw material are transferred by using a powder feeder, and the rotating speed of the powder feeder is independently 0.5-3 r / min during the transfer of the first raw material and the second raw material.

7. The method of reducing crack defects in a nickel-based cladding layer formed on an aluminum-based substrate surface according to any one of claims 1 to 4, characterized in that, The first raw material and the second raw material are independently spherical powder, and the particle size of the first raw material and the particle size of the second raw material are independently 40-105 mu m.

8. The method of reducing crack defects in a nickel-based cladding layer formed on an aluminum-based substrate surface according to any one of claims 1-4, wherein The first raw material is treated by the following method before laser cladding: the silver powder and the copper powder are mixed and then subjected to first drying.

9. The method of reducing crack defects in a nickel-based cladding layer formed on an aluminum-based substrate surface according to any one of claims 1-4, wherein The first drying is performed by vacuum heating drying. The temperature of the first drying is 80-120 DEG C, and the time of the first drying is 300-420 min. The mixing is performed by ball milling. The ball-to-material ratio in the ball milling process is (2-4):

1. The rotating speed of the ball milling is 220-280 r / min. The time of the ball milling is 300-420 min. The ball milling is performed under the protection of inert gas. The second raw material is treated by the following method before laser cladding: the second raw material is subjected to second drying.

10. The method of reducing crack defects in a nickel-based cladding layer formed on an aluminum-based substrate surface according to any one of claims 1-4, wherein The second drying is performed by vacuum heating drying. The temperature of the second drying is 80-120 DEG C, and the time of the second drying is 300-420 min. ​

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