A ceramic reinforced metal-based multi-gradient composite coating and its preparation method and application

Abstract

This invention discloses a ceramic-reinforced metal-based multi-gradient composite coating, its preparation method, and its application. The composite coating comprises a first gradient layer, a second gradient layer, and a third gradient layer, sequentially laser-clad onto the surface of a copper substrate from the inside out. The first gradient layer, by weight percentage, comprises: 80-90% aluminum-clad nickel alloy powder, 10-20% aluminum bronze, and / or cupronickel; the second gradient layer comprises: 80-85% Ni60, 7-10% graphite, 4.5-12.7% titanium-iron alloy powder and / or vanadium-iron alloy powder, and 0.3-0.5% carbon nanotubes; the third gradient layer comprises: 74.5-84% Ni60, 10-15% graphite, 5-10% titanium-iron alloy powder and / or vanadium-iron alloy powder, and 0.5-1% carbon nanotubes. This effectively suppresses the coating's cracking sensitivity and improves its hardness and wear resistance.

Description

Technical Field

[0001] This invention belongs to the field of metal ceramic materials technology, and particularly relates to a ceramic-reinforced metal-based multi-gradient composite coating, its preparation method and application. Background Art

[0002] Copper alloys are widely used in various heat exchange and heat transfer equipment due to their good thermal conductivity. They are also used as components in cooling equipment, such as the condenser copper plates in continuous casting equipment. However, their relatively poor hardness and wear resistance often result in a short service life for copper alloy components, especially under harsh high-temperature conditions, which further reduces their service life.

[0003] Ni-based alloys are often used to improve the yield strength of materials operating at high temperatures. This is mainly because Ni-based alloys can generate a second phase, which forms antiphase grain boundaries that inhibit dislocation movement. Ni60 alloy powder is a widely used cladding material among Ni-based self-fluxing alloy powders. It contains alloying elements such as C, B, Si, Cr, Fe, and Ni. B and Si are the main elements for slag formation and deoxidation. Cr and Fe readily form solid solutions with Ni, thus improving the wear resistance and oxidation resistance of the cladding layer. Cr and Fe readily combine with C to produce carbides, which can improve the hardness and wear resistance of the cladding layer.

[0004] To extend the service life of these copper components, laser cladding technology is considered an effective method for preparing protective coatings on their surfaces. However, due to the high thermal conductivity and low laser absorption rate of copper alloys, it is difficult to directly prepare high-quality cladding coatings on their surfaces. The coating properties are prone to abrupt changes and have high cracking sensitivity, thereby reducing the coating's hardness and wear resistance, making it unsuitable for harsh application conditions. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a ceramic-reinforced metal-based multi-gradient composite coating, its preparation method and application, wherein the gradient coating can effectively suppress the cracking sensitivity of the coating and improve the hardness and wear resistance of the coating.

[0006] To solve the above-mentioned technical problems, the first aspect of the present invention provides a ceramic-reinforced metal-based multi-gradient composite coating, comprising a first gradient layer, a second gradient layer and a third gradient layer sequentially laser-clad on the surface of a copper substrate from the inside out;

[0007] The raw material components of the first gradient layer, by weight percentage, include: 80-90% aluminum-clad nickel alloy powder, 10-20% aluminum bronze and / or cupronickel;

[0008] The raw material components of the second gradient layer, by weight percentage, include: 80-85% Ni60, 7-10% graphite, 4.5-12.7% ferro-titanium alloy powder and / or ferro-vanadium alloy powder, and 0.3-0.5% carbon nanotubes.

[0009] The raw material components of the third gradient layer, by weight percentage, include: 74.5-84% Ni60, 10-15% graphite, 5-10% titanium-iron alloy powder and / or vanadium-iron alloy powder, and 0.5-1% carbon nanotubes.

[0010] Specifically, this invention uses aluminum-clad nickel alloy powder as the main raw material on the surface of a copper substrate. A certain amount of aluminum bronze and / or cupronickel is added to the first gradient layer directly connected to the copper substrate. The second gradient layer contains a certain amount of graphite powder, ferrotitanium alloy powder and / or ferrovanadium alloy powder, and a small amount of carbon nanotubes (CNTs) added to Ni60. The third gradient layer contains a certain amount of graphite powder, no less than the amount of ferrotitanium alloy powder and / or ferrovanadium alloy powder in the second gradient layer, and CNTs added to Ni60, forming a gradient coating with different compositions and structures. Specifically: the first gradient layer is based on the principle of infinite miscibility between Cu and Ni, reducing the oxygen content of the coating and enabling better metallurgical bonding between the first gradient layer and the substrate; simultaneously, the aluminum-clad nickel alloy powder and aluminum bronze powder contain Al, which can react with oxygen in the coating, reducing the coating porosity; cupronickel has a lower reflectivity than pure copper, effectively utilizing laser energy while ensuring coating quality. The nano-graphite powder and titanium-iron alloy powder or vanadium-iron alloy powder added to the second gradient layer not only strengthen Ni60 to form a TiC / VC reinforcing phase, but the introduction of Ti also enhances the internal toughness of the Ni60 coating, reduces the cracking tendency, and CNTs increase heterogeneous nucleation sites, refining the coating microstructure. The third gradient layer adds a certain amount of nano-graphite powder and more of one or more of titanium-iron alloy powder or vanadium-iron alloy powder than the second gradient layer, along with CNTs. This not only forms a reinforcing phase but also ensures a smooth transition in the coating. Furthermore, the design ensures a smooth transition between the gradient layers from the substrate to the top of the coating, preventing abrupt performance changes, reducing the coating's cracking sensitivity, and to some extent, improving the overall performance of the coating.

[0011] Therefore, this invention optimizes and rationally blends the raw materials for each gradient layer, creating a continuous gradient transition between different coatings, eliminating abrupt changes in microstructure and properties, and resulting in excellent metallurgical bonding. Simultaneously, it improves the toughness within the coating and significantly enhances its performance through the formation of reinforcing phases.

[0012] Preferably, the Ni60 powder has a particle size of 50-100 μm. The crack rate of the coating is proportional to the laser power density of the laser cladding. By controlling the particle size of Ni60, the laser power density can be effectively controlled, reducing the heat input.

[0013] Preferably, the graphite powder has a particle size of less than 50 nm; more preferably, the graphite powder has a particle size of 30-50 nm.

[0014] Preferably, the powder particle size of both the pure aluminum bronze and the cupronickel is 30-45 μm.

[0015] Preferably, the chemical composition of the Ni60, by weight percentage, is: C 0.6-1.0%, Cr 14-17%, B 2.5-4.5%, Si 3.0-4.5%, Fe≤15.0%, impurities≤0.7%, and the balance is Ni. During the laser melting process, it can form a solid solution with other elements, which reduces the formation of pores and improves the overall performance of the coating.

[0016] Preferably, the chemical composition of the aluminum-clad nickel alloy powder is 4-6% Al by weight, with the balance being Ni.

[0017] Preferably, the aluminum-clad nickel alloy powder is KF-6.

[0018] Preferably, the titanium-iron alloy powder is FeTi70.

[0019] Preferably, the vanadium-iron alloy powder is FeV50.

[0020] Preferably, the thickness of the first gradient layer is 0.2-0.3 mm, the thickness of the second gradient layer is 0.3-0.5 mm, and the thickness of the third gradient layer is 0.4-0.6 mm. Using gradient layers of different thicknesses clad onto the surface of the copper substrate not only facilitates the formation of gradient structural changes and prevents abrupt performance changes, but also controls the coating thickness to reduce coating cracking caused by temperature gradients.

[0021] A second aspect of this invention provides a method for preparing the above-mentioned ceramic-reinforced metal-based multi-gradient composite coating, comprising the following steps:

[0022] (1) The raw materials for preparing the first gradient layer, the second gradient layer and the third gradient layer were ultrasonically assisted to grind in a vacuum atmosphere and then vacuum dried to obtain the first premix, the second premix and the third premix.

[0023] (2) The first premix, the second premix and the third premix are sequentially clad on the surface of the copper substrate by laser cladding to form a first gradient layer, a second gradient layer and a third gradient layer; then the substrate is slowly cooled to obtain the ceramic-reinforced metal-based multi-gradient composite coating.

[0024] Preferably, in step (1), the frequency of the ultrasound assistance is 20-40KHz and the amplitude is 2μm.

[0025] Specifically, during the powder mixing process, the small particle size of the powder can lead to agglomeration. Ultrasonic-assisted powder mixing can make the powder more uniform, resulting in a more uniform coating structure and more stable performance.

[0026] Preferably, in step (2), the laser cladding process parameters are as follows: laser power of 2200-2500W, spot diameter of 2-3mm, spot scanning speed of 6-8mm / s, powder feeding rate of 2-3g / min, powder tray rotation speed of 0.2-0.4r / min, overlap rate of 40%, laser head angle of 2-4°, and powder carrier gas flow of 4-6L / min argon.

[0027] Preferably, in step (2), the rate of slow cooling is 0.1-0.3℃ / min. Since the copper substrate has high thermal conductivity and its thermal expansion coefficient and other parameters are quite different from those of the Ni-based alloy coating, air cooling at room temperature will cause an imbalance in temperature changes, resulting in cracking or peeling of the coating.

[0028] Preferably, before laser cladding, the process further includes a step of preheating the copper substrate at a temperature of 350-450°C. Preheating the copper substrate before laser cladding helps to reduce the lateral and longitudinal temperatures at the junction of the deposited layer and the substrate during the cooling process, thereby effectively reducing the cracking sensitivity of the coating.

[0029] The third aspect of the present invention provides the application of the above-mentioned ceramic-reinforced metal-based multigradient composite coating in protective coatings.

[0030] Preferably, the protective coating includes protective coatings for blast furnace tuyeres and continuous casting crystallizers.

[0031] Compared with the prior art, the above-described technical solution of the present invention has at least the following technical effects or advantages:

[0032] This invention employs laser cladding to sequentially clad a first gradient layer, a second gradient layer, and a third gradient layer on the surface of a copper substrate to form a ceramic-reinforced metal-based multi-gradient composite coating. By optimizing and rationally compounding the raw materials for each gradient layer, a continuous gradient transition is achieved between different coatings, eliminating abrupt changes in microstructure and properties, resulting in good metallurgical bonding. At the same time, the toughness inside the coating is improved, and the working performance of the coating is greatly enhanced through the generation of reinforcing phases.

[0033] Meanwhile, ultrasonic assistance is used during powder mixing to ensure more uniform powder composition. Substrate heating and slow cooling reduce temperature gradients and coating cracking tendencies, comprehensively improving the quality of the prepared coating. This achieves a microhardness of 350-1200 HV. 0.3 With a friction and wear coefficient of 0.6721-0.7013, it is suitable for harsh industrial working conditions. Attached Figure Description

[0034] Figure 1 This is a cross-sectional optical micrograph of the ceramic-reinforced metal-based multigradient composite coating prepared in Example 1.

[0035] Figure 2 This is a cross-sectional optical micrograph of the ceramic-reinforced metal-based multigradient composite coating prepared in Example 2.

[0036] Figure 3 This is a cross-sectional optical micrograph of the ceramic-reinforced metal-based multi-gradient composite coating prepared in Example 3.

[0037] Figure 4 The image shows the cross-sectional optical microstructure of the ceramic-reinforced metal-based multigradient composite coating prepared in Comparative Example 1.

[0038] Figure 5 The image shows the cross-sectional optical microstructure of the ceramic-reinforced metal-based multi-gradient composite coating prepared in Comparative Example 2.

[0039] Figure 6 This is a cross-sectional optical micrograph of the gradient coating of ceramic-reinforced metal matrix composite material prepared in Comparative Example 8. Detailed Implementation

[0040] The present invention will now be described in detail with reference to embodiments to facilitate understanding of the invention by those skilled in the art. It is particularly important to note that the embodiments are merely illustrative of the invention and should not be construed as limiting the scope of protection of the invention. Non-essential improvements and adjustments made to the invention by those skilled in the art based on the above description should still fall within the scope of protection of the invention. Furthermore, all raw materials mentioned below, unless otherwise specified, are commercially available products; all process steps or preparation methods not mentioned in detail are process steps or preparation methods known to those skilled in the art.

[0041] In the following examples and comparative examples, the aluminum-clad nickel alloy powder used was KF-6, the titanium-iron alloy powder was FeTi70, and the vanadium-iron alloy powder was FeV50.

[0042] Example 1

[0043] A ceramic-reinforced metal-based multi-gradient composite coating comprises, from the inside out, a first gradient layer, a second gradient layer, and a third gradient layer, which are sequentially laser-clad onto the surface of a copper substrate.

[0044] The raw material components of the first gradient layer, by weight percentage, include: 80% aluminum-clad nickel alloy powder and 20% aluminum bronze; the raw material components of the second gradient layer, by weight percentage, include: 85% Ni60, 10% graphite powder, 4.5% ferrotitanium alloy powder, and 0.5% CNTs; the raw material components of the third gradient layer, by weight percentage, include: 75% Ni60, 15% graphite powder, 4.6% ferrotitanium alloy powder, 4.6% ferrovanadium alloy powder, and 0.8% CNTs. The aluminum-clad nickel alloy powder is spherical with a particle size of 50-100 μm; the Ni60 powder is spherical with a particle size of 50-100 μm; the aluminum bronze powder is spherical with a particle size of 30-45 μm; the graphite powder is spherical with a particle size of 50 nm; and the ferrotitanium alloy powder is spherical with a particle size of 20-45 μm.

[0045] The chemical composition of Ni60 by weight percentage is: C 0.8%, Cr 16%, B 3%, Si 3.5%, Fe 14.8%, impurities ≤0.7%, and the balance is Ni.

[0046] The thickness of the first gradient layer is 0.2 mm; the thickness of the second gradient layer is 0.4 mm; and the thickness of the third gradient layer is 0.7 mm.

[0047] A ceramic-reinforced metal-based multi-gradient composite coating and its laser processing method include the following steps:

[0048] (1) Weigh the raw materials for the preparation of the first gradient layer, the second gradient layer and the third gradient layer according to the mass ratio, grind them in a vacuum atmosphere for 12 hours with ultrasonic assistance (frequency of 25KHz), and dry them in a vacuum at 100℃ for 8 hours to obtain the first premix, the second premix and the third premix.

[0049] (2) Select a copper substrate with dimensions of length × width × thickness = 250mm × 250mm × 18mm as the substrate material. First, preheat the copper substrate at 350℃ for 30min. Then, use laser cladding to sequentially clad the first premix, the second premix and the third premix obtained in step (1) on the surface of the copper substrate to form the first gradient layer, the second gradient layer and the third gradient layer. Then, move the prepared coating into the heat preservation box for slow cooling (cooling rate is 0.2℃ / min) to obtain the ceramic-reinforced metal-based multi-gradient composite coating of this embodiment.

[0050] The laser cladding process parameters are as follows: laser power is 2200W, spot diameter is 2mm, spot scanning speed is 6.5mm / s, powder feeding rate is 2.2g / min, powder tray rotation speed is 0.2r / min, overlap rate is 40%, laser head angle is 2°, and the powder carrier gas is argon gas with a flow rate of 4.5L / min.

[0051] Example 2

[0052] A ceramic-reinforced metal-based multi-gradient composite coating includes a first gradient layer, a second gradient layer, and a third gradient layer, which are sequentially laser-clad onto the surface of a copper substrate.

[0053] The raw material components of the first gradient layer, by weight percentage, include: 90% aluminum-clad nickel alloy powder and 10% cupronickel; the raw material components of the second gradient layer, by weight percentage, include: 84.5% Ni60, 9.7% graphite powder, 4.5% ferrotitanium alloy powder, and 0.3% CNTs; the raw material components of the third gradient layer, by weight percentage, include: 83% Ni60, 11% graphite powder, 5% ferrotitanium alloy powder, and 1% CNTs. The aluminum-clad nickel alloy powder is spherical with a particle size of 50-100 μm; the Ni60 powder is spherical with a particle size of 50-100 μm; the cupronickel powder is spherical with a particle size of 30-45 μm; the graphite powder is spherical with a particle size of 50 nm; and the ferrotitanium alloy powder is spherical with a particle size of 20-45 μm.

[0054] The chemical composition of Ni60 by weight percentage is: C 0.8%, Cr 16%, B 3%, Si 3.5%, Fe 14.8%, impurities ≤0.7%, and the balance is Ni.

[0055] The thickness of the first gradient layer is 0.25 mm; the thickness of the second gradient layer is 0.3 mm; and the thickness of the third gradient layer is 0.4 mm.

[0056] A ceramic-reinforced metal-based multi-gradient composite coating and its laser processing method include the following steps:

[0057] (1) Weigh the raw materials for the preparation of the first gradient layer, the second gradient layer and the third gradient layer according to the mass ratio, grind them in a vacuum atmosphere for 12 hours with ultrasonic assistance (frequency of 30KHz), and dry them in a vacuum at 100℃ for 8 hours to obtain the first premix, the second premix and the third premix.

[0058] (2) Select a copper substrate with dimensions of length × width × thickness = 250mm × 250mm × 18mm as the substrate material. First, preheat the copper substrate at 400℃ for 30min. Then, use laser cladding to sequentially clad the first premix, the second premix and the third premix obtained in step (1) on the surface of the copper substrate to form the first gradient layer, the second gradient layer and the third gradient layer. Then, move the prepared coating into the heat preservation box for slow cooling (cooling rate is 0.2℃ / min) to obtain the ceramic-reinforced metal-based multi-gradient composite coating of this embodiment.

[0059] The laser cladding process parameters are as follows: laser power is 2300W, spot diameter is 2mm, spot scanning speed is 7mm / s, powder feeding rate is 2.5g / min, powder tray rotation speed is 0.3r / min, overlap rate is 40%, laser head angle is 3°, and the powder carrier gas is argon gas with a flow rate of 5L / min.

[0060] Example 3

[0061] A ceramic-reinforced metal-based multi-gradient composite coating includes a first gradient layer, a second gradient layer, and a third gradient layer, which are sequentially laser-clad onto the surface of a copper substrate.

[0062] The raw material components of the first gradient layer, by weight percentage, include: 80% aluminum-clad nickel alloy powder, 10% aluminum bronze, and 10% cupronickel; the raw material components of the second gradient layer, by weight percentage, include: 83% Ni60, 10% graphite powder, 6.5% ferrotitanium alloy powder, and 0.5% CNTs; the raw material components of the third gradient layer, by weight percentage, include: 75% Ni60, 14% graphite powder, 5% ferrotitanium alloy powder, 5% ferrovanadium alloy powder, and 1% CNTs. The aluminum-clad nickel alloy powder is spherical with a particle size of 50-100 μm; the Ni60 powder is spherical with a particle size of 50-100 μm; the aluminum bronze and cupronickel powders are spherical with a particle size of 30-45 μm; the graphite powder is spherical with a particle size of 50 nm; and the ferrotitanium alloy and ferrovanadium alloy powders are spherical with a particle size of 20-45 μm.

[0063] The chemical composition of Ni60 by weight percentage is: C 0.8%, Cr 16%, B 3%, Si 3.5%, Fe 14.8%, impurities ≤0.7%, and the balance is Ni.

[0064] The thickness of the first gradient layer is 0.3 mm; the thickness of the second gradient layer is 0.5 mm; and the thickness of the third gradient layer is 0.5 mm.

[0065] A ceramic-reinforced metal-based multi-gradient composite coating and its laser processing method include the following steps:

[0066] (1) Weigh the raw materials for the preparation of the first gradient layer, the second gradient layer and the third gradient layer according to the mass ratio, grind them in a vacuum atmosphere for 12 hours with ultrasonic assistance (frequency of 40KHz), and dry them in a vacuum at 100℃ for 8 hours to obtain the first premix, the second premix and the third premix.

[0067] (2) Select a copper substrate with dimensions of length × width × thickness = 250mm × 250mm × 18mm as the substrate material. First, preheat the copper substrate at 450℃ for 30min. Then, use laser cladding to sequentially clad the first premix, the second premix and the third premix obtained in step (1) on the surface of the copper substrate to form the first gradient layer, the second gradient layer and the third gradient layer. Then, move the prepared coating into the heat preservation box for slow cooling (cooling rate is 0.2℃ / min) to obtain the ceramic-reinforced metal-based multi-gradient composite coating of this embodiment.

[0068] The laser cladding process parameters are as follows: laser power is 2500W, spot diameter is 3mm, spot scanning speed is 8mm / s, powder feeding rate is 3g / min, powder tray rotation speed is 0.2r / min, overlap rate is 40%, laser head angle is 3°, and the powder carrier gas is argon gas with a flow rate of 5.5L / min.

[0069] Comparative Example 1

[0070] The only difference between Comparative Example 1 and Example 1 is that ultrasonic-assisted grinding was not performed in step (1) of the preparation method of ceramic-reinforced metal-based multi-gradient composite coating in Comparative Example 1.

[0071] Comparative Example 2

[0072] The only difference between Comparative Example 2 and Example 1 is that the ceramic-reinforced metal-based multi-gradient composite coating of Comparative Example 2 does not contain a first gradient layer.

[0073] Comparative Example 3

[0074] The only difference between Comparative Example 3 and Example 1 is that the second gradient layer of the ceramic-reinforced metal-based multi-gradient composite coating in Comparative Example 3 does not contain graphite. The raw material composition of the second gradient layer includes: 94% Ni60, 4.5% titanium-iron alloy powder, and 0.5% CNTs.

[0075] Comparative Example 4

[0076] The only difference between Comparative Example 4 and Example 1 is that the second gradient layer of the ceramic-reinforced metal-based multi-gradient composite coating in Comparative Example 4 does not contain titanium-iron alloy powder. The raw material composition of the second gradient layer includes: 89.5% Ni60, 10% graphite powder, and 0.5% CNTs.

[0077] Comparative Example 5

[0078] The only difference between Comparative Example 5 and Example 1 is that the third gradient layer of the ceramic-reinforced metal-based multi-gradient composite coating in Comparative Example 5 does not contain graphite. The raw material composition of the third gradient layer includes: 90% Ni60, 4.6% ferro-titanium alloy powder, 4.6% ferrovanadium alloy powder, and 0.8% CNTs.

[0079] Comparative Example 6

[0080] The only difference between Comparative Example 6 and Example 1 is that the raw material composition of the third gradient layer of the ceramic-reinforced metal-based multi-gradient composite coating in Comparative Example 6 does not contain titanium-iron alloy powder and vanadium-iron alloy powder. The raw material composition of the third gradient layer includes: 9.2% Ni60, 10% graphite powder, and 0.8% CNTs.

[0081] Comparative Example 7

[0082] The only difference between Comparative Example 7 and Example 1 is that the third gradient layer of the ceramic-reinforced metal-based multi-gradient composite coating in Comparative Example 7 does not contain CNTs. The raw material composition of the third gradient layer includes: 80.8% Ni60, 10% graphite powder, 4.6% titanium-iron alloy powder, and 4.6% vanadium-iron alloy powder.

[0083] Comparative Example 8

[0084] The only difference between Comparative Example 8 and Example 1 is that in step (2) of the preparation method of ceramic-reinforced metal-based multi-gradient composite coating in Comparative Example 8, slow cooling was not performed.

[0085] Performance testing

[0086] 1. Microstructure

[0087] The cross-sectional optical microstructure of the ceramic-reinforced metal-based multi-gradient composite coatings prepared in Examples 1-3 was examined using an optical microscope. The test results are as follows: Figure 1-3 As shown. From Figure 1-3 As can be seen, in the ceramic-reinforced metal matrix composite gradient coatings prepared in Examples 1-3, the internal structure of the coating is uniform and dense, with no obvious defects such as pores or cracks, and the cladding layer is well bonded to the substrate.

[0088] Figure 4 The image shows the cross-sectional optical microstructure of the ceramic-reinforced metal-based multi-gradient composite coating prepared in Comparative Example 1. Since ultrasonic assistance was not performed during grinding, the prepared powder exhibits obvious agglomeration.

[0089] Figure 5 The image shows the cross-sectional optical microstructure of the ceramic-reinforced metal-based multi-gradient composite coating prepared in Comparative Example 2. Due to the absence of a first gradient layer, the coating has poor adhesion to the substrate, and the abrupt change in coating performance leads to the appearance of through cracks to some extent.

[0090] Figure 6 The image shows the cross-sectional optical microstructure of the ceramic-reinforced metal-based multi-gradient composite coating prepared in Comparative Example 8. Due to the lack of slow cooling of the coating, cracking occurred during rapid cooling due to differences in material properties.

[0091] 2. Microhardness

[0092] The hardness of the ceramic-reinforced metal matrix composite gradient coatings prepared in Examples 1-3 and Comparative Examples 1-8 was tested using a microhardness tester. Multiple tests were conducted at 100 μm intervals along the direction perpendicular to the coating. The load was 300 g and the loading time was 15 s. The measured hardness values ​​are shown in Table 1.

[0093] Table 1:

[0094] sample <![CDATA[Microhardness (HV 0.3 )]]> Example 1 350-1200 Example 2 360-1050 Example 3 300-1050 Comparative Example 1 340-1060 Comparative Example 2 300-1000 Comparative Example 3 300-1030 Comparative Example 4 320-1050 Comparative Example 5 350-1000 Comparative Example 6 350-980 Comparative Example 7 360-950 Comparative Example 8 310-1050

[0095] As can be seen from Table 1, the hardness of the cladding layer of the coatings prepared in Examples 1-3 is much greater than that of the substrate, and the hardness of the coating gradually increases from the bonding area to the surface of the cladding layer.

[0096] Compared to Example 1, the agglomeration of powder in Comparative Example 1 leads to uneven coating composition and defects such as burn-off, thereby affecting the performance of the coating.

[0097] Compared to Example 1, the absence of the first gradient layer in Comparative Example 2 resulted in poor coating transition, leading to poor coating adhesion and cracking, which in turn affected the coating hardness.

[0098] Compared to Example 1, Comparative Example 3 shows a stepwise change in coating hardness. This is mainly because the reduction in the reinforcing ratio of the second gradient layer leads to a poor transition between the first and third gradient layers, thus affecting the coating hardness.

[0099] The coating hardness of Comparative Example 4 was lower than that of Example 1 to a certain extent. Although the increase in graphite content would form solid solution reinforcement inside the coating, the coating hardness mainly depended on precipitation reinforcement, which led to the decrease in hardness.

[0100] Compared to Example 1, Comparative Example 5 shows that the third gradient layer is mainly characterized by dispersion reinforcement, and the decrease in hardness is caused by a reduction in the proportion of solid solution and precipitation reinforcement.

[0101] Compared to Example 1, in Comparative Example 6, the third gradient layer is mainly solid solution strengthening, while the dispersion and precipitation strengthening are weakened, resulting in a decrease in coating hardness.

[0102] Compared to Example 1, Comparative Example 7 did not include CNTs, resulting in the absence of fine-grain reinforcement within the coating and thus reducing the coating hardness.

[0103] Compared to Example 1, Comparative Example 8 did not undergo slow cooling, which led to coating cracking and thus affected the coating's hardness to some extent.

[0104] 3. Wear-resistant

[0105] The ceramic-reinforced metal matrix composite gradient coatings prepared in Examples 1-3 were subjected to tribological tests using a tribological testing machine. The friction pair consisted of Si3N4 balls, with a reciprocating friction length of 10 mm, a load of 10 N, a speed of 2 m / s, and a sliding distance of 200 m. The measured friction coefficients of the ceramic-reinforced metal matrix composite gradient coatings prepared in Examples 1-3 were 0.6825, 0.7013, and 0.6721, respectively, which were significantly higher than the friction coefficient of 0.3083 of the copper substrate.

[0106] For those skilled in the art, several simple deductions or substitutions can be made without departing from the inventive concept, without requiring creative effort. Therefore, any simple improvements made to this invention by those skilled in the art based on the disclosure of this invention should be within the scope of protection of this invention. The above embodiments are preferred embodiments of this invention, and all processes similar to this invention and equivalent changes should fall within the scope of protection of this invention.

Claims

1. A ceramic-reinforced metal-based multi-gradient composite coating, characterized in that, It includes a first gradient layer, a second gradient layer, and a third gradient layer that are laser-clad sequentially from the inside out on the surface of a copper substrate; The raw material components of the first gradient layer, by weight percentage, include: 80-90% aluminum-clad nickel alloy powder, 10-20% aluminum bronze and / or cupronickel; The raw material components of the second gradient layer, by weight percentage, include: 80-85% Ni60, 7-10% graphite, 4.5-12.7% titanium-iron alloy powder and / or vanadium-iron alloy powder, and 0.3-0.5% carbon nanotubes. The raw material components of the third gradient layer, by weight percentage, include: 74.5-84% Ni60, 10-15% graphite, 5-10% titanium-iron alloy powder and / or vanadium-iron alloy powder, and 0.5-1% carbon nanotubes.

2. The ceramic-reinforced metal-based multi-gradient composite coating according to claim 1, characterized in that, The Ni60 powder has a particle size of 50-100 μm; and / or the graphite powder has a particle size of less than 50 nm.

3. The ceramic-reinforced metal-based multi-gradient composite coating according to claim 1, characterized in that, The chemical composition of the Ni60, by weight percentage, is: C 0.6-1.0%, Cr 14-17%, B 2.5-4.5%, Si 3.0-4.5%, Fe≤15.0%, impurities≤0.7%, with the balance being Ni; the chemical composition of the aluminum-clad nickel alloy powder, by weight percentage, is Al 4-6%, with the balance being Ni.

4. The ceramic-reinforced metal-based multi-gradient composite coating according to claim 1, characterized in that, The thickness of the first gradient layer is 0.2-0.3 mm, the thickness of the second gradient layer is 0.3-0.5 mm, and the thickness of the third gradient layer is 0.4-0.6 mm.

5. A method for preparing a ceramic-reinforced metal-based multi-gradient composite coating as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) The raw materials for preparing the first gradient layer, the second gradient layer and the third gradient layer were ultrasonically assisted to grind in a vacuum atmosphere at a frequency of 20-40KHz, and then vacuum dried to obtain the first premix, the second premix and the third premix. (2) The first premix, the second premix and the third premix are sequentially clad on the surface of the copper substrate by laser cladding to form a first gradient layer, a second gradient layer and a third gradient layer; then the substrate is slowly cooled at a rate of 0.1-0.3℃ / min to obtain the ceramic-reinforced metal-based multi-gradient composite coating.

6. The method for preparing the ceramic-reinforced metal-based multi-gradient composite coating according to claim 5, characterized in that, In step (2), the laser cladding process parameters are as follows: laser power is 2200-2500W, spot diameter is 2-3mm, spot scanning speed is 6-8mm / s, powder feeding rate is 2-3g / min, powder tray rotation speed is 0.2-0.4 r / min, overlap rate is 40%, laser head angle is 2-4°, and powder carrier gas flow is 4-6L / min of argon.

7. The method for preparing a ceramic-reinforced metal-based multi-gradient composite coating according to claim 5, characterized in that, Before performing the laser cladding, the copper substrate is preheated at a temperature of 350-450°C.

8. The application of the ceramic-reinforced metal-based multi-gradient composite coating according to any one of claims 1-4 in protective coatings.

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