Diamond-metal composite brazing coating and preparation method and application thereof

Abstract

The invention discloses a diamond-metal composite brazing coating as well as a preparation method and application thereof, and relates to the technical field of wear-resistant coatings. The diamond-metal composite brazing coating comprises a plurality of composite layers and a surface layer which are arranged on the surface of a base body, the composite layer comprises a wear-resistant layer and a slow-release layer, and the slow-release layer comprises a metal net, diamond particles and metal foil. Diamond particles are arranged between the metal foil and the metal net, and a metallized coating is generated on the surface of diamond through in-situ reaction under the combined action of covering of the upper-layer metal foil and constraint of the lower-layer metal net, so that the interface bonding strength is remarkably improved, residual stress and diamond graphitization are reduced, and floating of the diamond is effectively inhibited; and segregation caused by density difference is reduced. The preparation process is simple and convenient to operate, and the prepared diamond-metal composite brazing coating is suitable for the field of superhard cutters, the field of electronic packaging heat sinks and the field of mining machinery and aerospace wear-resistant coatings.

Description

Technical Field

[0001] This invention relates to the field of wear-resistant coating technology, and more specifically, to diamond-metal composite brazing coatings, their preparation methods, and applications. Background Technology

[0002] Existing research often involves combining diamond particles with metal matrices such as copper, silver, and nickel to prepare diamond composite coatings that combine high thermal conductivity, high strength, and good formability. This overcomes the brittleness, difficulty in processing, and chemical inertness of diamond itself, and expands the application range of diamond.

[0003] The industrial application of diamond composite coatings faces the following challenges: (1) Low-temperature brazing filler metals have poor wettability on diamonds, resulting in insufficient interfacial bonding strength, which makes the coatings have poor wear resistance and cannot meet the high load requirements; (2) Active brazing filler metals directly wet diamonds at temperatures above 800℃, causing severe graphitization of diamonds and reducing their hardness and thermal conductivity; (3) Single-layer diamond coatings have limited wear resistance; although multi-layer gradient structure design can improve wear resistance, it has high residual stress; (4) The thermal expansion coefficients of diamond and metal substrates are very different. After forming a diamond composite coating, residual stress will be caused by CTE mismatch, resulting in microcracks or even macroscopic cracks in the coating; (5) There is a density difference between diamond and metal. During the heating process, diamonds are prone to float and agglomerate.

[0004] Therefore, there is an urgent need to develop an innovative preparation technology that takes into account high bonding strength, resistance to graphitization, low residual stress, and uniform distribution to solve or improve the above-mentioned technical problems.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide diamond-metal composite brazing coatings, their preparation methods, and applications, in order to solve or improve the above-mentioned technical problems.

[0007] This invention is implemented as follows: In a first aspect, the present invention provides a diamond-metal composite brazing coating, comprising a composite layer and a surface layer disposed on the surface of a substrate; wherein the surface layer is disposed away from the substrate. The composite layer includes a wear-resistant layer and a slow-release layer. The wear-resistant layer is in contact with the substrate and / or the slow-release layer. The slow-release layer includes a metal mesh, diamond particles and a metal foil arranged in sequence. Multiple diamond particles are laid on the metal mesh and the metal foil covers the multiple diamond particles.

[0008] In a second aspect, the present invention provides a method for preparing a diamond-metal composite brazing coating as described in any of the foregoing embodiments, comprising the following steps: S1. Prepare the sustained-release layer in the order of metal mesh, diamond particles and metal foil; S2. Diamond-brazing alloy composite coating is prepared by mixing diamond particles, brazing filler metal and first binder in proportion; S3. Apply the diamond-brazing alloy composite coating from step S2 onto the substrate surface to form a diamond-brazing alloy coating, thus obtaining a wear-resistant layer; S4. Stack the slow-release layer from step S1 onto the wear-resistant layer from step S3 to form a composite layer; S5. Apply the diamond-brazing alloy composite coating from step S2 onto the composite layer from step S4 to form a diamond-brazing alloy coating, thereby obtaining a surface layer and a diamond-metal composite brazing alloy coating preform. S6. The diamond-metal composite brazing coating preform obtained in step S5 is brazed to obtain the diamond-metal composite brazing coating.

[0009] Thirdly, the present invention provides the application of a diamond-metal composite brazing coating as described in any of the foregoing embodiments or a diamond-metal composite brazing coating prepared by any of the foregoing embodiments in the fields of superhard cutting tools, electronic packaging heat sinks, mining machinery and aerospace wear-resistant coatings.

[0010] The present invention has the following beneficial effects: The diamond-metal composite brazing coating provided in this embodiment of the invention includes a slow-release layer in which diamond particles are placed between a metal foil and a metal mesh and fixed. Through the combined effect of the upper metal foil covering and the lower metal mesh constraint, a metallized coating is generated on the diamond surface in situ during the preparation process, which significantly improves the interfacial bonding strength, reduces residual stress and diamond graphitization, effectively inhibits diamond floating, and reduces segregation caused by density difference.

[0011] The preparation process is simple, and the resulting diamond-metal composite brazing coating is suitable for use in the fields of superhard cutting tools, electronic packaging heat sinks, mining machinery, and aerospace wear-resistant coatings. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, 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 the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of the overall cross-section of the diamond-metal composite brazing coating obtained in step (5) of Example 1 from a first-view perspective; Figure 2 This is a schematic diagram of the structure of the sustained-release layer obtained in step (2) of Example 1; Figure 3 Analysis results of diamond particle floating: The left figure is Example 1, and the right figure is Comparative Example 1; Figure 4 Analysis results of surface cracking of the product: The left figure is Example 1, and the right figure is Comparative Example 1; Figure 5 Analysis results of diamond distribution in the product: the left figure is Example 1, and the right figure is Comparative Example 1; Figure 6 Analysis results of diamond surface formation and performance improvement: The left figure is Example 1, and the right figure is Comparative Example 1.

[0014] Icons: 1-Substrate; 2-Composite layer; 20-Wear-resistant layer; 201-First wear-resistant layer; 202-Second wear-resistant layer; 21-Sustained-release layer; 211-First sustained-release layer; 213-Metal mesh; 214-Diamond particles; 215-Metal foil; 212-Second sustained-release layer; 3-Surface layer. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention 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.

[0016] The slow-release layer 21 in the diamond-metal composite brazing coating provided by this invention, through the interlocking design of the upper metal foil 215 and the lower metal mesh 213, reacts in situ on the diamond surface during the welding process to generate a metallized coating, effectively suppressing the floating of diamond particles 214, while significantly improving the interfacial bonding strength and mitigating residual stress and diamond graphitization defects. Specific implementation methods are as follows: In a first aspect, the present invention provides a diamond-metal composite brazing coating, comprising a composite layer 2 and a surface layer 3 disposed on the surface of a substrate 1, wherein the surface layer 3 is disposed away from the substrate 1; The composite layer 2 includes a wear-resistant layer 20 and a slow-release layer 21. The wear-resistant layer 20 is in contact with the substrate 1 and / or the slow-release layer 21. The slow-release layer 21 includes a metal mesh 213, diamond particles 214 and a metal foil 215 arranged sequentially. Multiple diamond particles 214 are laid on the metal mesh 213 and the metal foil 215 covers the multiple diamond particles 214.

[0017] It should be noted that the repeated stacking of composite layer 2 forms a gradient transition on the surface of substrate 1. Substrate 1 is located at the bottom layer, and the slow-release layer 21 is stacked on the surface of substrate 1 in the order of metal mesh 213, diamond particles 214 and metal foil 215. The upper metal foil 215 provides mechanical interlocking and chemical diffusion channels to balance stress buffering and electrical / thermal conductivity requirements. The lower metal mesh 213 enables directional penetration of molten metal. The mesh nodes of metal mesh 213 are coated with a suitable metal binder to promote diamond wetting at high temperatures.

[0018] If the metal mesh 213 is missing, it will not be able to relieve stress, which will cause the surface of the diamond-metal composite brazing coating to crack and reduce its performance; if the metal foil 215 is missing, the diamond particles 214 will float to the surface.

[0019] In an optional implementation, the number of layers in composite layer 2 is n, where 1 ≤ n ≤ 3; Optionally, the composite layers 2 are stacked sequentially on the surface of the substrate 1, and the wear-resistant layer 20 in the composite layer 2 closest to the substrate 1 is in contact with the substrate 1; when n>1, the wear-resistant layer 20 and the slow-release layer 21 in the multilayer composite layer 2 are arranged alternately.

[0020] For example, when the number of repetitions of composite layer 2 in diamond-metal composite brazing coating is 1, the total number of layers of composite layer 2 and surface layer 3 is 3, and its structure is as follows: substrate 1, wear-resistant layer 20, slow-release layer 21 (metal mesh 213, diamond particles 214, metal foil 215) and surface layer 3.

[0021] When the number of repetitions of composite layer 2 is 2, the total number of layers of composite layer 2 and surface layer 3 is 5. Its structure is as follows: substrate 1, first wear-resistant layer 201, first slow-release layer 211 (metal mesh 213, diamond particles 214, metal foil 215), second wear-resistant layer 202, second slow-release layer 212 (metal mesh 213, diamond particles 214, metal foil 215) and surface layer 3, and so on.

[0022] It should be noted that on the side away from the substrate 1, the coating always ends with a diamond-solder coating, meaning that surface layer 3 is part of the wear-resistant layer 20. If surface layer 3 were a slow-release layer 21, it would significantly reduce the wear resistance of the product.

[0023] In this embodiment of the invention, the core purpose of the multi-layer composite layer 2 is to construct a gradient wear-resistant system, significantly extending the service life of the coating through thickness accumulation and structural optimization. A single-layer slow-release layer 21 is prone to early failure (such as interface peeling or abrasive grain shedding) due to localized stress concentration under extreme friction or impact conditions. The multi-layer design, through alternating deposition of the wear-resistant layer 20 and the slow-release layer 21, achieves controllable growth in the total coating thickness, making wear resistance increase approximately linearly with thickness. Furthermore, the multi-interface structure effectively blocks crack propagation paths, forcing cracks to undergo plastic deflection or passivation within the metal layer. In addition, repeated stacking can compensate for potential defects in single-layer coatings, such as porosity or uncoated areas, improving the overall density of the coating.

[0024] The synergistic design of the wear-resistant layer 20 and the stress-relieving layer 21 aims to balance the contradiction between "stress relief" and "wear resistance enhancement." Its core objective is to achieve synergistic reinforcement through the periodic arrangement of rigid-flexible materials. The wear-resistant layer 20 provides functional compensation: based on the stress buffering effect of the wear-resistant layer 20, the stress-relieving layer 21 provides extreme hardness (HV≥7000) to resist abrasive cutting; while the metal foil 215 / mesh of the stress-relieving layer 21 plays a role in plastic energy dissipation, relieving stress through dislocation slip and microcrack deflection, while its ductility inhibits the initiation of brittle cracks. The mesh structure of the metal mesh 213 also mechanically locks in the diamond, preventing it from segregating upwards due to density differences. This alternating arrangement avoids the brittle failure of pure diamond particles 214 and overcomes the problem of insufficient wear resistance in pure metal layers.

[0025] The multi-layered wear-resistant layer 20 and the slow-release layer 21 constitute a "sandwich composite structure coating." Through multiple complete "wear-resistant-toughening" cycles, a stable stress gradient is established while ensuring sufficient thickness. The diamond-solder coating on the surface layer 3 preferentially bears wear, the intermediate composite layer 2 gradually absorbs load energy, and the bottom wear-resistant layer 20 serves as a "backup" wear-resistant phase, thus achieving continuous performance stability during multiple friction cycles. In addition, the symmetrical structural design (diamond-solder layers at both ends + intermediate composite layer 2) can offset residual thermal stress and prevent coating warping failure.

[0026] The synergistic design of the wear-resistant layer 20 and the stress-relieving layer 21 forms an optimized system that combines rigidity and flexibility. The stress-relieving layer 21 provides plastic deformation capability to absorb stress, while the wear-resistant layer 20 ensures extreme wear resistance. Removing the stress-relieving layer 21 would cause the diamond-metal composite brazing coating to fail brittlely due to stress concentration, failing to inhibit the upward agglomeration of diamond particles 214 at high temperatures, resulting in uneven coating composition. Removing the wear-resistant layer 20, on the other hand, would cause the material to completely lose its ultra-hard wear resistance, with the wear rate soaring by 5-8 times. Therefore, the synergistic cooperation of the two achieves stress redistribution and crack prevention through the stress-relieving layer 21, while maintaining excellent wear resistance through the wear-resistant layer 20. This performance balance cannot be achieved by a single material system.

[0027] In an optional embodiment, the total number of wear-resistant layer 20, slow-release layer 21 and surface layer 3 on the upper surface of substrate 1 is 3 to 5 layers.

[0028] If the total number of layers is set to 7, 9 or more, the corresponding diamond-metal composite brazing coating can theoretically be prepared when the thickness does not exceed 3.5mm. However, the investment in time and production costs will be greatly increased, and there will be a waste of resources. If the thickness exceeds 3.5mm, the coating will be too thick. Diamond is not a conductor of heat, which leads to localized concentration of thermal stress. Even if a slow-release layer 21 is added, the effect will be greatly reduced.

[0029] In an optional embodiment, the mesh size of the metal mesh 213 is 150-300 mesh; the particle size of the diamond particles 214 is 50-400 mesh.

[0030] Optionally, the ratio of the mesh aperture in the metal mesh 213 to the particle size of the diamond particles 214 is 0.5-0.95. The mesh aperture of the metal mesh 213 is adjusted appropriately according to the size of the diamond particles 214. Specifically, the mesh aperture of the metal mesh 213 is smaller than the particle size of the diamond particles 214 to ensure that the diamond particles 214 do not fall off during the stacking process.

[0031] In an optional embodiment, the thickness of the wear-resistant layer 20 is ≤1mm; Optionally, the surface layer 3 and the wear-resistant layer 20 are each independently diamond-brazing alloy coatings, wherein the mass percentage of diamond in the diamond-brazing alloy coating is 0.05-0.40; the surface layer 3 belongs to the wear-resistant layer 20, and its material is the same as that of the wear-resistant layer 20, which is a diamond-brazing alloy composite coating.

[0032] It should be noted that the thickness of the surface layer 3 and the wear-resistant layer 20 can be the same or different; it can be adjusted reasonably as needed, and the final total thickness of the composite layer and the surface layer should meet the requirement of 1.2mm-3.5mm.

[0033] Optionally, the total thickness of the composite layer 2 and the surface layer 3 is 1.2mm-3.5mm; When the total thickness of composite layer 2 and surface layer 3 is about 2.5 mm, the surface of the diamond-metal composite brazing coating sample does not show defects such as macroscopic cracks or groove cracks, and the surface remains intact. The diamond is evenly distributed, and the interfacial bonding strength and wear resistance are significantly improved. The floating of diamond in the sample is effectively suppressed, and a metallized coating is generated on the diamond surface of the slow-release layer 21, forming a dense and high-strength carbide layer.

[0034] If the wear-resistant layer 20 is too thick, it will cause uneven heating of the product. When the heat preservation time is long, diamond agglomeration and segregation will occur. Strip-shaped scratches will appear on the surface of the product, some components will be lost, and it is easy to break and crack. The density of the bond with diamond is poor.

[0035] Optionally, the thickness of the metal foil 215 is 20μm-80μm; Optionally, the thickness of the metal mesh 213 is ≤100μm, and the wire diameter of the metal mesh 213 is ≤70μm.

[0036] In an optional embodiment, the brazing filler metal in the diamond-brazing filler metal coating 3 and the diamond-brazing filler metal wear-resistant layer 20 is selected from at least one of nickel-based brazing filler metal, cobalt-based brazing filler metal, copper-based brazing filler metal and silver-based brazing filler metal.

[0037] And / or, the material of the metal mesh 213 is selected from at least one of nickel (Ni) mesh, chromium (Cr) mesh, iron (Fe) mesh, phosphor bronze mesh (CuSn10) and stainless steel mesh; the purity of the material used in the metal mesh 213 is ≥99.5%.

[0038] And / or, the metal foil 215 is made of at least one of titanium (Ti) foil, tungsten (W) foil, nickel (Ni) foil, chromium (Cr) foil and silver (Ag) foil; Optionally, the material of the substrate 1 is selected from any one of WC-Co cemented carbide, high-speed steel, Ni-based cemented carbide, Fe-Ni-based cemented carbide, stainless steel, and cermet. The specifications of the substrate 1 are selected according to actual needs. Before use, it is necessary to remove oil and oxide scale from its surface. In the embodiment of the present invention, sandblasting is used. After sandblasting, the surface is cleaned again and then dried for later use.

[0039] In an optional embodiment, the diamond-metal composite brazing coating has at least one of the following characteristics: Feature 1: When the solder is a nickel-based solder, the metal mesh 213 is selected from at least one of nickel mesh, chromium mesh and iron mesh, and the metal foil 215 is selected from at least one of titanium foil, tungsten foil and nickel foil; Feature 2: When the solder is a cobalt-based solder, the metal mesh 213 is selected from at least one of chromium mesh, tungsten mesh and titanium mesh, and the metal foil 215 is selected from at least one of chromium foil and titanium foil; Feature 3: When the solder is a copper-based solder, the metal mesh 213 is selected from at least one of copper mesh and phosphor bronze mesh, and the metal foil 215 is selected from at least one of titanium foil and silver foil; Feature 4: When the solder is a silver-based solder, the metal mesh 213 is selected from at least one of silver mesh, copper mesh and titanium mesh, and the metal foil 215 is selected from at least one of titanium foil and silver foil.

[0040] It should be noted that the embodiments of the present invention also need to consider the compatibility between the brazing filler metal, the metal mesh 213, and the metal foil 215. The specific compatibility principles are analyzed as follows: (1) Chemical compatibility principle: The brazing filler metal mesh 213 should preferably be a metal mesh 213 that can form a solid solution or reinforcing phase (such as Ni-Cr, Co-W); the brazing filler metal foil 215 should be a metal foil 215 that can react with diamond to form carbides (TiC, Cr3C2, etc.) (such as Ti, Cr).

[0041] (2) Gradient principle of coefficient of thermal expansion (CTE): CTE of diamond ≈ 1 × 10 -6 / K, a CTE transition layer needs to be constructed using a metal mesh 213 / foil to reduce thermal stress, such as a high CTE Cu-based solder paired with a low CTE metal W foil; or a medium CTE Ni-based solder paired with a medium CTE metal Ni foil to buffer stress.

[0042] (3) Functional complementarity principle: high strength + high toughness, such as nickel-based brazing filler metal (high strength) + chromium mesh (reinforcement) + titanium foil (TiC interface strengthening); high thermal conductivity + wear resistance: such as silver-based brazing filler metal (low temperature and high thermal conductivity) + copper mesh (thermal conductivity) + titanium foil (TiC wear resistance).

[0043] (4) Process adaptability principle: for low-temperature brazing (550℃-700℃), Ag-Cu-Ti brazing alloy + silver / copper mesh is preferred, and for high-temperature brazing (900℃-1100℃), Ni / Co-based brazing alloy + heat-resistant metal mesh 213 (such as W, Cr) is preferred.

[0044] To facilitate comparison and selection, the matching status and advantages of the applicable series (brazing filler material, metal mesh 213 material and metal foil 215 material) are selectively summarized in Table 1.

[0045] Table 1. Matching and Advantages of Brazing Filler Material, Metal Mesh 213 Material, and Metal Foil 215 Material

[0046] It should be noted that the matching of brazing filler metal, metal mesh 213 and metal foil 215 listed in Table 1 is only for illustrative purposes. In the embodiments of the present invention, the material matching in Table 1 can be selected according to actual needs, or other material matching can be selected.

[0047] In a second aspect, the present invention provides a method for preparing a diamond-metal composite brazing coating as described in any of the foregoing embodiments, comprising the following steps: S1. Prepare the sustained-release layer 21 in the order of metal mesh 213, diamond particles 214 and metal foil 215; S2. Diamond-brazing alloy composite coating is prepared by mixing diamond particles 214, brazing filler metal and first binder in proportion; S3. Apply the diamond-brazing alloy composite coating from step S2 onto the surface of substrate 1 to form a diamond-brazing alloy coating, thus obtaining wear-resistant layer 20. S4. Stack the slow-release layer 21 from step S1 onto the wear-resistant layer 20 from step S3 to form a composite layer 2; S5. Apply the diamond-brazing alloy composite coating from step S2 onto the composite layer 2 from step S4 to form a diamond-brazing alloy coating, thereby obtaining the surface layer 3 and a diamond-metal composite brazing alloy coating preform. S6. The diamond-metal composite brazing coating preform obtained in step S5 is brazed to obtain the diamond-metal composite brazing coating.

[0048] Among them, step S1 is to prepare the sustained-release layer 21, step S2 is to prepare the diamond-brazing alloy composite coating, steps S3-S5 are to prepare the diamond-metal composite brazing coating preform, and step S6 is to prepare the diamond-metal composite brazing coating.

[0049] It should be noted that during the stacking process, the coverage of diamond particles 214 on the metal mesh 213 is 50%-100%; the size of the metal mesh 213 is 1mm-2mm larger than the size of the substrate 1, and the size of the metal foil 215 is 1mm-2mm larger than the size of the metal mesh 213; the mesh aperture of the metal mesh 213 is 150-300 mesh, the particle size of the diamond particles 214 is 50-400 mesh, and the ratio of the mesh aperture of the metal mesh 213 to the particle size of the diamond particles 214 is 0.5-0.95.

[0050] The filler metal particle size is 20μm-100μm, and the appropriate size should be selected according to actual needs.

[0051] In an optional embodiment, before use, the substrate 1 is further subjected to pretreatment of its surface, which includes the following steps: After cleaning the substrate 1 with an organic solvent, it is dried at a temperature of 80℃-100℃; wherein the organic solvent is selected from at least one of acetone, ethanol, methanol and isopropanol. The dried substrate 1 was subjected to sandblasting treatment, wherein the sandblasting pressure was 0.4MPa-0.6MPa, the spraying distance was 80mm-120mm, and the surface roughness Ra of the substrate after sandblasting treatment was 3μm-5μm. The sandblasted substrate 1 is cleaned again to obtain the pretreated substrate 1.

[0052] In an optional implementation, the number of layers in composite layer 2 is n, where 1 ≤ n ≤ 3; When n=1, proceed according to steps S1-S6; When n>1, repeat steps S1-S4 to form a multilayer composite layer 2, wherein the first wear-resistant layer 20 is coated on the substrate 1, and the remaining wear-resistant layers 20 are coated on the slow-release layer 21, and then steps S5-S6 are performed.

[0053] In an optional embodiment, the preparation method further includes at least one of the following features: Feature 1: When preparing diamond-brazing alloy composite coating, the amount of the first binder is 5%-20% of the total mass of the diamond-brazing alloy composite coating; the first binder is selected from at least one of ethanol, propylene glycol and water glass mixed aqueous solution; The type of first binder can be reasonably selected according to different brazing methods. For example, if induction brazing is selected, the first binder selected in the early stage can be a water glass mixed aqueous solution, such as sodium silicate or potassium silicate; wherein the mass percentage of water glass in the water glass mixed aqueous solution is 8%-15%. If vacuum brazing is selected, the first binder selected in the early stage can be an alcohol reagent, such as ethanol or propylene glycol.

[0054] The main function of the binder is to provide temporary bonding force, allowing the mixture to maintain its shape during coating or molding, and to fix the diamond particles 214 and the brazing filler metal in the initial stage of brazing heating until the brazing filler metal melts to achieve metallurgical bonding.

[0055] If the amount of the first binder is too small, the diamond particles 214 and the brazing filler metal will be difficult to mix evenly, and component segregation will easily occur. The resulting composite coating will be loose, making it more difficult to pre-place the coating on the surface of the substrate 1 or the surface of the slow-release layer 21, thereby affecting the uniformity of the distribution of diamond particles 214 in the final product. If the amount of the first binder is too large, it will decompose and carbonize when heated, generating a large amount of gas and residue that contaminates the brazing interface, hinders the flow and spread of the brazing filler metal, and forms inclusions and pores, thereby affecting the uniformity of the coating and reducing the performance of the final product.

[0056] Feature 2: The fixing method of the slow-release layer 21 is selected from at least one of the following: second adhesive bonding, spot welding, pressure welding and flame spraying fusion method. The second binder is selected from at least one of sodium silicate-based binder, nano-TiH2 modified binder, and nano-Ni modified binder; all of which are high-temperature resistant binders.

[0057] The specific operation of the second adhesive bonding is as follows: the second adhesive is applied to the mesh nodes of the metal mesh 213, the diamond particles 214 are evenly sprinkled on the metal mesh 213, the unadhesive diamond particles 214 are blown off with compressed air, and then another layer of the second adhesive is applied to the upper surface of the diamond particles 214, and the metal foil 215 is fixed on the metal mesh 213 with diamond particles 214.

[0058] The specific operation of spot welding is as follows: Using a micro spot welding machine, diamond particles 214 are spot welded locally at several key points (such as the four symmetrical corner points, the geometric center point, the intersection of the metal mesh 213 grids and the stress concentration area) and then fixed on the metal mesh 213 grids. After covering with metal foil 215, they are gradually fixed by spot welding.

[0059] The specific operation of pressure welding is as follows: fix the metal mesh 213 on the vacuum adsorption stage, evenly spread the diamond particles 214, and use a resistance spot welding machine to micro-weld and fix the diamond particles 214 at several key points (such as mesh intersections, edge projection points of diamond particles 214, stress compensation points, and heat distribution balance points). After covering with metal foil 215, first perform edge positioning, and then pressure weld and seal at the mesh intersections at intervals of 1 mm to 4 mm.

[0060] It should be noted that the present invention does not impose any special limitations on the selection of key points, but makes reasonable adjustments based on the specifications of the actual parts, the operating habits of the operators, and the different requirements for the final product.

[0061] The specific operation of the flame spraying melting method is as follows: First, diamond particles 214 are evenly sprinkled on the upper surface of the metal mesh 213, and then covered with a layer of metal foil 215. A high-velocity ultrasonic flame spraying (HVOF) system is then used to melt the metal foil 215 at a low temperature, causing it to adhere to the metal mesh 213 and form a slow-release layer 21. The lower temperature is set appropriately according to the material of the metal foil 215, and is ≤1000℃.

[0062] Feature 3: The coverage of diamond particles 214 on the metal mesh 213 is 50%-100%; ensuring that the diamond particles 214 are evenly distributed on the upper surface of the metal mesh 213.

[0063] Feature 4: The size of the metal mesh 213 is 1mm-2mm larger than the size of the substrate 1, and the size of the metal foil 215 is 1mm-2mm larger than the size of the metal mesh 213. The larger size of the metal foil 215 is beneficial to the brazing process, so that the metal foil 215 can wrap the diamond under the action of gravity and prevent the diamond from floating.

[0064] In an optional embodiment, the brazing process is selected from vacuum brazing or induction brazing; wherein, vacuum brazing is suitable for overall welding, and induction brazing is suitable for local repair or precision area welding; the heating method of brazing is used to make the metal foil 215 wrap the diamond under the action of gravity, prevent the diamond from floating and generate a carbide layer in situ on the diamond surface, thereby achieving the purpose of diamond surface modification.

[0065] The embodiments of the present invention employ induction brazing or vacuum brazing to achieve interfacial metallurgical bonding at short-time high temperatures, thereby reducing the risk of graphitization.

[0066] During vacuum brazing, the diamond-metal composite brazed preform is placed in a vacuum brazing furnace and evacuated to a vacuum degree ≤5×10⁻⁶. -3 Pa, heat at a rate of 3℃ / min-20℃ / min to a temperature 20℃-30℃ higher than the melting point of the brazing filler metal, hold at that temperature for 5min-25min, and then cool in the furnace to 80℃-300℃ before being removed from the furnace; For example, when the brazing filler metal is nickel-based, the specific operation of vacuum brazing with gradient heating is as follows: heating at a rate of 15°C / min for the 0-300°C stage, at a rate of 12°C / min for the 300°C-500°C stage, at a rate of 10°C / min for the 500°C-800°C stage, and at a rate of 7°C / min from 800°C to the maximum temperature. When other brazing filler metals are selected, the specific gradient heating parameters should be adjusted appropriately according to the actual filler metal.

[0067] And / or, during induction brazing, a high-frequency induction coil is used to heat the diamond-metal composite brazing preform. After the temperature is 20℃-30℃ higher than the melting point of the brazing filler metal, the induction power is cut off after holding the temperature for 30s-45s, and the material is allowed to cool naturally to room temperature in a protective atmosphere.

[0068] Optionally, after induction brazing is completed, the surface of the diamond-metal composite brazing coating is also finished.

[0069] Finishing involves using a diamond grinding wheel to remove protruding metal and adhesive from the surface of the diamond-metal composite brazing coating. This invention does not impose a specific limitation on the grit size of the diamond grinding wheel; it can be reasonably selected according to actual needs. Specifically, in this embodiment, 180-200 mesh is used. In other embodiments, the grit size can be adjusted appropriately according to actual needs.

[0070] In an optional embodiment, the heating rate of induction brazing is relatively fast. In this invention, a rate of 5°C / s-12°C / s is used to raise the temperature from room temperature to a temperature 20°C-30°C above the melting point of the brazing filler metal.

[0071] It should be noted that the RAG15 high-frequency induction heating device used in this invention has a fixed frequency of 350 kHz; the heating rate is adjusted by regulating the current within the range of 15A-35A; the current can be adjusted reasonably according to actual conditions. In other embodiments of this invention, other devices can be selected according to actual conditions.

[0072] Thirdly, the present invention provides the application of a diamond-metal composite brazing coating as described in any of the foregoing embodiments or a diamond-metal composite brazing coating prepared by any of the foregoing embodiments in the fields of superhard cutting tools, electronic packaging heat sinks, mining machinery and aerospace wear-resistant coatings.

[0073] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0074] Example 1 This embodiment provides a diamond-metal composite brazing coating, which is prepared by the following steps: (1) Pretreatment of matrix 1 65Mn steel was selected as the substrate 1, with dimensions of 70 mm × 30 mm × 20 mm. The surface of the substrate 1 was cleaned with acetone to remove oil and impurities. Specifically, the substrate 1 was ultrasonically cleaned with acetone for 15 min and then roughened by surface sandblasting. The sandblasting pressure was 0.5 MPa and the spray distance was 100 mm. After sandblasting, the surface roughness Ra of the substrate was 4 μm. Then, the substrate was ultrasonically cleaned again with acetone to remove residual abrasive and dried at 90°C for later use.

[0075] (2) Preparation of sustained-release layer 21 The sustained-release layer 21 is prepared in the order of metal mesh 213, diamond particles 214 and metal foil 215; The metal mesh 213 is made of pure nickel (Ni) with a purity of over 99.5% and a mesh size of 300 mesh. The wire diameter of the metal mesh 213 is 40 μm. The diamond particles 214 have a particle size of 180-200 mesh. The metal foil 215 is made of tungsten (W) with a purity of 99.9% and a thickness of 30 μm. The pure Ni mesh is cut into sheets that are 1 mm larger in length and 1 mm larger in width than the substrate 1. The W foil is also cut into sheets that are 1 mm larger in length and 1 mm larger in width than the pure Ni mesh.

[0076] It should be noted that after the metal mesh 213 is placed, it is fixed with a clamp. A second adhesive, nano-Ni modified adhesive, is coated on the upper surface of the metal mesh 213. Then, diamond particles 214 are evenly distributed on the upper surface of the metal mesh 213, so that the coverage of the metal mesh 213 reaches 80%. Compressed air is used to blow away the unadheded diamond particles 214. Then, a layer of nano-Ni modified adhesive is added to the surface of the diamond particles 214, and the W foil is fixed on the metal mesh 213 with diamond particles 214, so that the overall thickness of the sustained-release layer 21 is controlled within 150μm.

[0077] A schematic diagram of the structure of the prepared sustained-release layer 21 is shown below. Figure 2 , Figure 2 The arrows indicate the stacking direction of the coatings, which is also the direction for welding and fixing the diamond-metal composite brazing preform after it has been made.

[0078] (3) Preparation of diamond-brazing alloy composite coating Diamond-brazing alloy composite coating is prepared by mixing diamond particles 214, brazing alloy and first binder in a certain proportion; wherein, diamond and brazing alloy are mixed in a ratio of 1:9; the first binder is a sodium silicate mixed aqueous solution (water glass mass percentage 10%), and its amount is 10% of the total mass of diamond-brazing alloy composite coating.

[0079] The brazing filler powder is selected from BNi-2 powder and 180-200 mesh diamond particles 214, which are mechanically mixed in a ball mill for 5 h.

[0080] (4) Preparation of diamond-metal composite brazing preforms Diamond-metal composite brazing coating is obtained by stacking pretreated substrate 1, composite layer 2, and surface layer 3 in that order and then brazing them.

[0081] The specific process is as follows: The diamond-brazing alloy composite coating obtained in step (3) is pre-coated on the surface of the substrate 1 after pretreatment in step (1) to form a diamond-brazing alloy coating, and the first wear-resistant layer 201 is obtained. The thickness of the first wear-resistant layer 201 is controlled to be 0.8 mm. Then, a first slow-release layer 211 is laid on the upper surface of the first wear-resistant layer 201. The metal mesh 213 of the first slow-release layer 211 is in contact with the first wear-resistant layer 201. A second diamond-brazing alloy coating, i.e., the second wear-resistant layer 202, is pre-coated on one side of the metal foil 215. Then, a second slow-release layer 212 is laid. Finally, a third diamond-brazing alloy coating 21, i.e., the surface layer 3, is pre-coated on one side of the metal foil 215 of the second slow-release layer 212. A total of three wear-resistant layers 20 (i.e., diamond-brazing alloy coatings) and two slow-release layers 21 are prepared. After air-drying for 24 hours, the diamond-metal composite brazing alloy coating preform is obtained at 100°C for 2 hours.

[0082] It should be noted that the thickness of the first wear-resistant layer 201, the second wear-resistant layer 202, and the surface layer 3 is consistent, all being 0.8mm.

[0083] The specific structure of the diamond-metal composite brazing preform is as follows: substrate 1, first wear-resistant layer 201, first slow-release layer 211 (metal mesh 213, diamond particles 214, metal foil 215), second wear-resistant layer 202, second slow-release layer 212 (metal mesh 213, diamond particles 214, metal foil 215) and surface layer 3.

[0084] (5) Preparation of diamond-metal composite brazing coating The diamond-metal composite brazing coating is obtained by brazing the diamond-metal composite brazing coating preform obtained in step (4).

[0085] The brazing process is induction brazing, specifically using a high-frequency induction coil (RAG-15KW, 350 kHz, 28A) to heat the diamond-metal composite brazed preform, followed by vacuuming to 5×10⁻⁶. -3 Pa was heated at a rate of 6℃ / s, and after reaching 1050℃ and holding for 30s, the induction power was cut off. The furnace was then allowed to cool naturally to room temperature in a protective atmosphere to obtain a diamond-metal composite brazing coating.

[0086] A schematic diagram of the overall cross-section of the prepared diamond-metal composite brazing coating from a first-view perspective is shown below. Figure 1 .

[0087] Example 2 This embodiment provides a diamond-metal composite brazing coating, the preparation steps of which are the same as in Example 1, the only difference being: (1) Pretreatment of matrix 1 The base material 1 is made of 316 stainless steel, with dimensions of 100 mm × 40 mm × 30 mm.

[0088] (2) Preparation of sustained-release layer 21 The metal mesh 213 is made of stainless steel with a purity of over 99.5% and a mesh size of 150 mesh. The wire diameter of the metal mesh 213 is 70 μm. The diamond particles 214 have a particle size of 80-100 mesh. The metal foil 215 is made of titanium (Ti) with a purity of 99.9% and a thickness of 35 μm. The second binder is a nano-TiH2 modified binder.

[0089] The overall thickness of the sustained-release layer 21 is controlled within 200 μm.

[0090] (3) Preparation of diamond-brazing alloy composite coating Diamond-brazing alloy composite coating is prepared by mixing diamond, brazing alloy and first binder in a certain proportion; wherein, diamond and brazing alloy are mixed in a ratio of 1:8; the first binder is ethanol, and its amount is 10% of the total mass of diamond-brazing alloy composite coating.

[0091] The brazing filler powder is selected from BNi-2 powder and 80-100 mesh diamond particles 214, which are mechanically mixed in a ball mill for 6 hours.

[0092] (4) Preparation of diamond-metal composite brazing preforms The thickness of the wear-resistant layer 20 is controlled to be 1 mm; The diamond-metal composite brazing preform consists of two wear-resistant layers 20 and one slow-release layer 21. The specific structure is as follows: substrate 1, wear-resistant layer 20, slow-release layer 21 (metal mesh 213, diamond particles 214, metal foil 215), and wear-resistant layer 20 (i.e., surface layer 3).

[0093] It should be noted that the thickness of the wear-resistant layer 20 and the surface layer 3 is the same, both being 1mm.

[0094] (5) Preparation of diamond-metal composite brazing coating Vacuum brazing was employed, with a gradient heating process: 0-300℃ at a rate of 15℃ / min, 300℃-500℃ at a rate of 12℃ / min, 500℃-800℃ at a rate of 10℃ / min, and from 800℃ to the maximum temperature at a rate of 7℃ / min. When the temperature reached the maximum of 1050℃, the sample was held at that temperature for 15 minutes before being slowly cooled in the furnace to below 200℃.

[0095] Example 3 This embodiment provides a diamond-metal composite brazing coating, the preparation steps of which are the same as in Example 1, the only difference being: (1) Pretreatment of matrix 1 The base material 1 is 42CrMo steel with dimensions of 60 mm × 25 mm × 20 mm.

[0096] (2) Preparation of sustained-release layer 21 The metal mesh 213 is a CuSn10 phosphor bronze mesh, 0.2 mm thick, with a mesh size of 250 mesh and a wire diameter of 40 μm; the diamond particles 214 have a particle size of 120-150 mesh; the metal foil 215 is made of pure silver (Ag) with a purity of 99.9% and a thickness of 35 μm. The second binder is a nano-Ni modified binder.

[0097] A micro spot welder is used to fix the pure silver foil and phosphor bronze mesh at key points (the four symmetrical corners and the intersection of the 213 metal mesh grids) to ensure that the diamond particles 214 do not leak out. Then, the slow-release layer 21 is fixed step by step with a gap of 2 mm × 2 mm.

[0098] The overall thickness of the sustained-release layer 21 is controlled within 150 μm.

[0099] (3) Preparation of diamond-brazing alloy composite coating Diamond-brazing alloy composite coating is prepared by mixing diamond, brazing alloy and first binder in a certain proportion; wherein, diamond and brazing alloy are mixed in a ratio of 3:17; the first binder is a sodium silicate mixed aqueous solution (water glass mass percentage 10%), and its amount is 10% of the total mass of diamond-brazing alloy composite coating.

[0100] The brazing filler powder was selected as BAg50CuZnSn powder, and 120-150 mesh diamond particles 214 were mechanically mixed in a ball mill for 6 h.

[0101] (4) Preparation of diamond-metal composite brazing preforms A total of three wear-resistant layers 20 and two slow-release layers 21 were formed; after natural air drying for 12 hours, the diamond-metal composite brazing coating preform was obtained by drying at 80℃ for 2 hours.

[0102] (5) Preparation of diamond-metal composite brazing coating The brazing process is induction brazing, specifically using a high-frequency induction coil (equipment model RAG-15KW, frequency 350 kHz, current 24A). After the temperature reaches 680℃ and is held for 40 seconds, the induction power supply is cut off. During the cooling stage, argon gas (12 L / min) is passed through to air cool to below 200℃.

[0103] Comparative Example 1 This comparative example provides a diamond-metal composite brazing coating, the preparation steps of which are the same as those in Example 1, the only difference being: Without adding the slow-release layer 21, the upper surface of the substrate 1 is only pre-coated with the wear-resistant layer 20, and the overall coating thickness is 2.5mm.

[0104] Comparative Example 2 This comparative example provides a diamond-metal composite brazing coating, the preparation steps of which are the same as in Example 2, the only difference being: Without adding the slow-release layer 21, the upper surface of the substrate 1 is only pre-coated with the wear-resistant layer 20, and the overall coating thickness is 2mm.

[0105] Brazing was performed under vacuum conditions, and the furnace was cooled to below 200°C after holding at 1050°C for 15 minutes.

[0106] Comparative Example 3 This comparative example provides a diamond-metal composite brazing coating, the preparation steps of which are the same as in Example 2, the only difference being: The sustained-release layer 21 lacks metal foil 215, and the order of metal mesh 213 and diamond particles 214 is also different. The double-layer structure sandwiched between the two wear-resistant layers 20 is: the upper layer is a pure Ni metal mesh, and the lower layer is diamond particles 214; its specific structure is: substrate 1, wear-resistant layer 20, diamond particles 214, pure Ni metal mesh, and wear-resistant layer 20 (i.e., surface layer 3).

[0107] Comparative Example 4 This comparative example provides a diamond-metal composite brazing coating, the preparation steps of which are the same as those in Example 3, the only difference being: Without adding the slow-release layer 21, the upper surface of the substrate 1 is only pre-coated with a solder composite coating, and the overall coating thickness is 2.5 mm.

[0108] Test Example 1 This test example analyzes the performance of the products prepared in Examples 1-3 and Comparative Examples 1-4 as follows, and the relevant results are summarized in Table 2. The test items include coating thickness, wear rate (ASTM G99 pin-disc friction test), coating microhardness, and coating interfacial bonding strength. The coating condition and surface morphology after wear are described and summarized. Among them, the coating thickness refers to the total thickness of composite layer 2 and surface layer 3, which is measured by metallographic sectioning. Five vertical lines are taken at equal intervals along the coating cross section at 500x magnification, with each line spaced ≥50μm apart (to avoid interference from the deformation zone). The single-point measurement is repeated 3 times and the average value is taken.

[0109] The microhardness of the coating was measured using an HV1000A Huayin microhardness tester. During the test, the specimen was kept flat, a load of 0.5 kg was applied, and the loading time was 10 s. Since the hardness of diamond is too high, it cannot be directly measured. Therefore, when measuring the coating, the test points were moved to the side without diamond. Twenty points were randomly selected from the coating, with each point spaced at least 0.5 mm apart. The arithmetic mean was taken as the final hardness test result of the composite coating.

[0110] Interface bonding strength: The thickness of the brazed coating is generally in the millimeter range, and it is not possible to directly test the bonding strength of the coating. The sample is prepared by adopting a substrate 1-coating-substrate 1 structure (the coating refers to the composite layer 2 and the surface layer 3). The tensile strength is tested on a universal testing machine to characterize the bonding strength. The average value of the three sets of test data is taken.

[0111] Table 2 Performance Test Results

[0112] As can be seen from the data in Table 2, Example 1 has the following characteristics compared with Comparative Example 1: the interfacial bonding strength of the coating is improved by 31.4%, and the metal W foil and metal Ni mesh in the sustained-release layer 21 form a "soft-hard-soft" gradient, which suppresses interfacial cracks; the microhardness of the diamond region of the coating is improved by 21.7%, thanks to the joint reinforcement of the metal W foil and dense diamond particles 214 in the sustained-release layer 21; the wear rate is reduced by 83.8%, and the multi-layer structure of the sustained-release layer 21 is conducive to optimizing load transfer, dispersing frictional energy, and reducing the shedding of diamond particles 214.

[0113] The wear rate in Example 2 was 76.2% lower than that in Comparative Example 2. The main reason for this was that the coating thickness in Comparative Example 2 was thicker, resulting in increased residual stress in the final diamond-metal composite brazing coating, which made it more prone to crack propagation; and due to the absence of the stress-relieving layer 21, it was more brittle. The wear rate in Example 2 was 65.5% lower than that in Comparative Example 3. The main reason for this was that although vacuum furnace cooling could alleviate some stress, the lack of support from the metal W foil made the diamond particles 214 prone to detachment.

[0114] Test Example 2 This test example uses the diamond-metal composite brazing coatings prepared in Example 1 and Comparative Example 1 as examples to conduct the following tests: (1) Analysis of the floating of diamond particles 214 The test surfaces were perpendicular to the directions of each layer of the diamond-metal composite brazing coating. The relevant results are shown in [reference needed]. Figure 3 The left figure shows Example 1, and the right figure shows Comparative Example 1. The composite layer 2 and the surface layer 3 are referred to as diamond composite coating.

[0115] from Figure 3 As can be seen, the addition of the slow-release layer 21 in Example 1 significantly improved the diamond flotation, and the diamond particles 214 in the metal composite coating were evenly distributed. In Comparative Example 1, without the slow-release layer 21, severe diamond flotation occurred, and the diamond composite coating and the brazing alloy layer showed obvious delamination.

[0116] (2) Analyze the surface cracking of the product The appearance morphology and microstructure of the product at the cracks were analyzed, and the relevant results are shown in [the table below]. Figure 4 The left figure is Example 1, and the right figure is Comparative Example 1.

[0117] from Figure 4 As can be seen, the addition of the sustained-release layer 21 in Example 1 resulted in a smooth surface, and the microstructure showed a relatively uniform diamond distribution on the macroscopic surface with no obvious graphitization. In Comparative Example 1, due to the thicker coating, thermal stress could not be sustained, leading to macroscopic surface cracking and surface groove defects, which significantly affected the mechanical properties of the final diamond-metal composite brazing coating.

[0118] (3) Analyze the distribution of diamonds in the product. The distribution of diamonds in the microstructure of the product was analyzed, and the relevant results are shown in [the table below]. Figure 5 The left figure is Example 1, and the right figure is Comparative Example 1.

[0119] from Figure 5 It can be seen that in Example 1, the addition of the sustained-release layer 21 resulted in a uniform distribution of diamonds in the microstructure. In Comparative Example 1, due to the thicker coating, uneven heating, and longer holding time, diamond agglomeration and segregation occurred.

[0120] (4) Analyze the surface products and performance improvement of diamond. The microstructure of the product was analyzed, and the relevant results are shown in [the table below]. Figure 6 The left figure is Example 1, and the right figure is Comparative Example 1.

[0121] from Figure 6 As can be seen, in Example 1, the addition of the sustained-release layer 21 resulted in the formation of a WC layer on the surface of the diamond particles 214, and the diamond particles 214 remained intact, with the carbides tightly bonded to the diamond. In Comparative Example 1, the diamond particles 214 reacted with the solder, forming Cr3C2 and Cr7C3 compounds on the surface. This resulted in streak-like scratches on the diamond surface and a loss of some effective components. Furthermore, the poor bonding of the chromium carbide formed on the surface easily led to defects such as breakage and cracking on the surface of the diamond particles 214, resulting in poor density of the bond between the chromium carbide and the diamond particles 214.

[0122] In summary, the diamond-metal composite brazing coating provided in this embodiment of the invention includes a slow-release layer 21 in which diamond particles 214 are placed between a metal foil 215 and a metal mesh 213 and fixed. Through the combined effect of the upper metal foil 215 covering and the lower metal mesh 213 constraining, a metallized coating is generated on the diamond surface in situ during the preparation process, which significantly improves the interfacial bonding strength, reduces residual stress and diamond graphitization, effectively inhibits diamond floating, and reduces agglomeration caused by density difference.

[0123] The preparation process is simple, and the resulting diamond-metal composite brazing coating is suitable for use in the fields of superhard cutting tools, electronic packaging heat sinks, mining machinery, and aerospace wear-resistant coatings.

[0124] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A diamond-metal composite brazing coating, characterized in that, Includes a composite layer and a surface layer disposed on the surface of a substrate; wherein the surface layer is disposed away from the substrate; The composite layer includes a wear-resistant layer and a slow-release layer, wherein the wear-resistant layer is in contact with the substrate and / or the slow-release layer, and the slow-release layer includes a metal mesh, diamond particles and a metal foil arranged in sequence, wherein a plurality of diamond particles are laid on the metal mesh and the metal foil covers the plurality of diamond particles.

2. The diamond-metal composite brazing coating according to claim 1, characterized in that, The number of layers in the composite layer is n, where 1≤n≤3; Preferably, the composite layers are stacked sequentially on the surface of the substrate, and the wear-resistant layer in the composite layer close to the substrate is connected to the substrate; when n>1, the wear-resistant layer and the slow-release layer in the multiple composite layers are arranged alternately.

3. The diamond-metal composite brazing coating according to claim 1, characterized in that, The metal mesh has a mesh size of 150-300 mesh; the diamond particles have a particle size of 50-400 mesh. Preferably, the ratio of the mesh aperture of the metal mesh to the particle size of the diamond particles is 0.5-0.

95.

4. The diamond-metal composite brazing coating according to claim 1, characterized in that, The thickness of the wear-resistant layer is ≤1mm; Preferably, the surface layer and the wear-resistant layer are each independently a diamond-brazing filler metal coating, wherein the mass percentage of diamond in the diamond-brazing filler metal coating is 0.05-0.

40. Preferably, the total thickness of the composite layer and the surface layer is 1.2mm-3.5mm; Preferably, the thickness of the metal foil is 20μm-80μm; Preferably, the thickness of the metal mesh is ≤100μm and the wire diameter of the metal mesh is ≤70μm.

5. The diamond-metal composite brazing coating according to claim 4, characterized in that, In the diamond-solder coating, the solder is selected from at least one of nickel-based solder, cobalt-based solder, copper-based solder, and silver-based solder; And / or, the material of the metal mesh is selected from at least one of nickel mesh, chromium mesh, iron mesh, tungsten mesh, silver mesh, copper mesh, titanium mesh, phosphor bronze mesh and stainless steel mesh; And / or, the material of the metal foil is selected from at least one of titanium foil, tungsten foil, nickel foil, chromium foil, silver foil and copper foil; And / or, the material of the substrate is selected from any one of WC-Co cemented carbide, high-speed steel, Ni-based cemented carbide, Fe-Ni-based cemented carbide, stainless steel and cermet.

6. The diamond-metal composite brazing coating according to claim 5, characterized in that, The diamond-metal composite brazing coating has at least one of the following characteristics: Feature 1: When the solder is a nickel-based solder, the metal mesh is selected from at least one of nickel mesh, chromium mesh, and iron mesh, and the metal foil is selected from at least one of titanium foil, tungsten foil, and nickel foil; Feature 2: When the solder is a cobalt-based solder, the metal mesh is selected from at least one of chromium mesh, tungsten mesh, and titanium mesh, and the metal foil is selected from at least one of chromium foil and titanium foil; Feature 3: When the solder is a copper-based solder, the metal mesh is selected from at least one of copper mesh and phosphor bronze mesh, and the metal foil is selected from at least one of titanium foil and silver foil; Feature 4: When the solder is a silver-based solder, the metal mesh is selected from at least one of silver mesh, copper mesh, and titanium mesh, and the metal foil is selected from at least one of titanium foil and silver foil.

7. A method for preparing a diamond-metal composite brazing coating as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Prepare the sustained-release layer in the order of metal mesh, diamond particles and metal foil; S2. Diamond-brazing alloy composite coating is prepared by mixing diamond particles, brazing filler metal and first binder in proportion; S3. Apply the diamond-brazing alloy composite coating described in step S2 to the surface of the substrate to form a diamond-brazing alloy coating, thereby obtaining a wear-resistant layer; S4. Stack the slow-release layer described in step S1 onto the wear-resistant layer described in step S3 to form a composite layer; S5. Apply the diamond-brazing alloy composite coating described in step S2 onto the composite layer described in step S4 to form a diamond-brazing alloy coating, thereby obtaining a surface layer and a diamond-metal composite brazing alloy coating preform. S6. The diamond-metal composite brazing coating preform obtained in step S5 is brazed to obtain the diamond-metal composite brazing coating.

8. The preparation method according to claim 7, characterized in that, The number of layers in the composite layer is n, where 1≤n≤3; When n=1, proceed according to steps S1-S6; When n>1, repeat steps S1-S4 to form a multilayer composite layer, wherein the first wear-resistant layer is coated on the substrate and the remaining wear-resistant layers are coated on the slow-release layer, and then steps S5-S6 are performed.

9. The preparation method according to claim 7, characterized in that, The preparation method further includes at least one of the following features: Feature 1: When preparing the diamond-brazing alloy composite coating, the amount of the first binder is 5%-20% of the total mass of the diamond-brazing alloy composite coating; the first binder is selected from at least one of ethanol, propylene glycol and water glass mixed aqueous solution; Feature 2: The method of fixing the diamond particles and the metal foil to the metal mesh is selected from at least one of the following: bonding with a second adhesive, spot welding, pressure welding, and flame spraying fusion method. The second adhesive is selected from at least one of sodium silicate-based adhesive, nano-TiH2 modified adhesive, and nano-Ni modified adhesive; Feature 3: The diamond particles cover 50%-100% of the metal mesh; Feature 4: The size of the metal mesh is 1mm-2mm larger than the size of the substrate, and the size of the metal foil is 1mm-2mm larger than the size of the metal mesh.

10. The application of a diamond-metal composite brazing coating as described in any one of claims 1-6 or a diamond-metal composite brazing coating prepared by the preparation method as described in any one of claims 7-9 in the fields of superhard cutting tools, electronic packaging heat sinks, mining machinery and aerospace.

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