Preparation method of multilayer diamond brazing tool based on thermoplastic resin molding

Abstract

The invention discloses a preparation method of a multilayer diamond brazing tool based on thermoplastic resin molding, which comprises the following steps: taking thermoplastic resin such as polyformaldehyde as a binder, banburying with metal powder (iron-based, copper-based or WC-Co-based alloy) to prepare a feed, crushing, screening, and carrying out hot press molding to form a matrix with a concave structure; the concave part is filled with a diamond gypsum body containing active brazing filler metal, and organic matter is removed through solvent degreasing or stepped thermal degreasing; and then synchronously completing matrix sintering and diamond brazing in a vacuum environment. By means of the process, the diamond exposure height can exceed 50%, the service life of a tool is prolonged by 2-3 times, the chip containing space is increased by 30% or above, and the problem of machining blockage is effectively solved. For a large-size tool, modular design is adopted, and the whole large-size multi-layer brazing tool is obtained after the small unit base bodies are spliced. The method is suitable for manufacturing high-end tools such as grinding wheels, drill bits and grinding cutters, and particularly meets the requirements of the fields of aerospace, precision machining and the like for high-performance diamond tools.

Description

Technical Field

[0001] This invention relates to an innovative preparation method for high-performance multilayer brazed diamond tools, belonging to the field of superhard composite material tool manufacturing. Background Technology

[0002] Traditional metal-bonded diamond tools primarily employ sintering, which produces diamond-metal-bonded products with long service lives, but lacks self-sharpening properties. Electroplating fixes a single layer of diamond particles with a nickel-based plating layer, but suffers from low bonding strength (<150 MPa) and diamond utilization of less than 30%, resulting in tool life generally below 50 hours. High-temperature brazing, using active brazing filler metals such as Ag-Cu-Ti and Cu-Sn-Ti in a vacuum furnace, can improve bonding strength (200-300 MPa), far exceeding electroplated diamond products, but is limited by single-layer arrangement; once the surface diamond detaches, it cannot continuously provide cutting capability, resulting in a short service life. While existing laser cladding methods can produce multi-layer diamond brazed products, the high-temperature heat-affected zone leads to high diamond graphitization, reducing diamond strength. For example, the method for preparing multilayer brazed diamond in Chinese patent CN108789189A suffers from drawbacks such as the inability to precisely control the multilayer structure and the high brittleness of the brazing process, especially in BNi-2 nickel-based brazing, where the outer diamond layer easily detaches. Generally, this method only produces a maximum of two layers. In Chinese patent CN113560564A, the brazed multilayer diamond tool prepared using 3D printing involves brazing of everything except the diamond. If made into a very dense tool, the cutting edge is poor; if made porous, the strength is insufficient. Summary of the Invention

[0003] To address the aforementioned problems, this invention proposes the following innovative approach: a feedstock is prepared by blending resin and metal powder, and precise control of the matrix working layer structure is achieved through heated molding; a concave structure with a certain depth is designed to achieve multi-layer self-supporting arrangement of diamond particles; and a simultaneous degreasing-sintering-brazing process is developed to complete matrix densification and diamond chemical bonding in a single heat treatment.

[0004] This invention discloses a method for preparing multilayer diamond brazing tools based on thermoplastic resin molding. The core of this method lies in firstly, mixing metal powder (such as WC-Co, Cu-based alloys, Fe-based, etc.) with thermoplastic resin (such as polyoxymethylene POM) through intensive mixing to form a uniform feedstock, and then preparing a working layer matrix with a specific concave structure through hot pressing molding. Pre-prepared diamond paste containing active brazing filler elements (such as alloys containing Cr, Ti, etc.) is precisely filled into the concave structure of the pre-formed matrix. This step achieves three-dimensional spatial orientation and controllable arrangement of multilayer diamond particles in the metal matrix. The molded blank undergoes solvent degreasing and precise stepped thermal degreasing processes to completely remove the organic resin components. Subsequently, high-temperature treatment is performed in a vacuum environment to simultaneously complete the densification sintering of the metal matrix and the active brazing connection of the diamond particles. To address the problems of short lifespan and complex fabrication processes for traditional single-layer diamond tools, this invention proposes a method for achieving three-dimensional controllable multi-layer arrangement of diamond particles through metal-resin composite matrix design and simultaneous sintering brazing. The fabrication method of this invention includes the following steps: a) Feed preparation: Thermoplastic resin and metal powder are mixed at 150-200℃ for 35 minutes to 4 hours to form a uniform feed. Metal powder, comprising 50-95 wt%, serves as the matrix skeleton material. Examples include Fe-based iron powder, Cu-based powder, and WC-Co. Thermoplastic resin, comprising 10-55 wt%, serves as the binder phase. Examples include polyoxymethylene (POM), polypropylene (PP), or their copolymers. Plasticizers, such as dioctyl phthalate (DOP), are added at 1-3% to improve flow. Lubricants, such as zinc stearate, are added at 0.5-2 wt% to reduce the molding friction coefficient. b) Forming of the concave structure working layer substrate: A working layer substrate with a predetermined concave structure is prepared using a hot press mold. Alternatively, it can be machined after forming to the required hole size or arrangement. The concave structure design generally uses depth to determine the number of layers. The concave depth (H) and diamond grit size (d) satisfy the following relationship: H = n * (d + 0.2d), where n is an integer from 2 to 10. The shape of the concave structure can be designed to improve cutting efficiency, such as a circle or hexagon. For a circle, the diameter D < 2d; other shapes ensure that one diamond can be inserted. Sometimes, to achieve a specific grinding effect, multiple diamonds can be added to a single hole.

[0005] c) Diamond coating: Diamond paste containing brazing filler metal or diamond particles and brazing powder are filled into the recesses by means of screen printing, dispensing, scraping, etc. The brazing paste contains 10-80 vol% diamond particles, 20-80 vol% brazing alloy powder and 1-10 wt% organic carrier.

[0006] d) Degreasing treatment: including a two-stage degreasing process: solvent degreasing (soaking in trichloroethylene or acetone for 0.5-2 hours) and thermal degreasing (heating to 400-600℃ at 1-5℃ / min and holding for 1-4 hours under inert atmosphere or vacuum conditions); removing organic matter in stages and forming a porous matrix framework.

[0007] e) Simultaneous sintering and brazing: Simultaneous sintering and brazing are performed under vacuum conditions ≤1×10⁻²Pa. The temperature is increased at 2-10℃ / min to 30-100℃ above the liquidus line of the brazing filler metal, and held for 0.5-3 hours. Sintering is performed on the working layer substrate of the recessed structure, and brazing is performed on the filled diamond brazing paste. The densification of the working layer substrate and the diamond metallurgical bonding are completed simultaneously. The sintered and brazed block is then brazed onto the specific substrate.

[0008] As a further technical solution of the present invention, the solder alloy powder is an active solder, including Ag-Cu-Ti, Cu-Sn-Ti, Ni-Cr-B-Si or Ni-Cr-P systems.

[0009] As a further technical solution of the present invention, the thermoplastic resin includes polyoxymethylene, polypropylene or wax-based resin.

[0010] As a further technical solution of the present invention, the thermoplastic resin is a wax-based resin system, and the degreasing process includes a two-stage degreasing process: solvent degreasing: soaking in trichloroethylene for 0.5-36 hours; thermal degreasing: heating to 400-600℃ at 1-10℃ / min and holding for 0.5-8 hours under an inert atmosphere.

[0011] As a further technical solution of the present invention, the thermoplastic resin is polyoxymethylene, and the degreasing method is degreasing by acid catalysis with nitric acid or oxalic acid.

[0012] As a further technical solution of the present invention, the resin mixed with the metal powder includes not only thermoplastic resin and thermosetting resin, but also other composite binders. Existing metal injection molding binder systems can all be used as molding resins.

[0013] As a further technical solution of the present invention, some other powders are added to the brazing alloy powder to increase the bonding strength with diamond (such as chromium, titanium, vanadium and other elements that easily form carbides with diamond), change the viscosity or hardness of the flux during brazing (such as alumina powder, silicon carbide, tungsten carbide, tungsten, etc.), or other elemental metal powders to adjust the brazing performance.

[0014] As a further technical solution of the present invention, a single diamond or multiple diamonds may be placed in a single layer of a single concave structure.

[0015] As a further technical solution of the present invention, the thermal degreasing process, sintering, and brazing can be completed in one process, only requiring a period of time at different temperature stages. Alternatively, they can be completed in stages.

[0016] As a further technical solution of the present invention, after degreasing and sintering, diamond brazing paste can be filled in and then vacuum brazed.

[0017] As a further technical solution of the present invention, the brazed and sintered body can be welded to the substrate or brazed and sintered together with the substrate after feeding and forming.

[0018] As a further technical solution of the present invention, diamond can be replaced by cubic boron nitride, cemented carbide, polycrystalline superhard material, silicon carbide or other hard abrasives, or composite abrasives thereof.

[0019] Compared with the prior art, the present invention has the following advantages: This invention relates to a method for preparing multilayer diamond brazing tools based on thermoplastic resin molding. By designing a metal-resin composite matrix with a specific concave structure, a three-dimensional oriented arrangement of diamond particles is achieved. Thermoplastic resins such as polyoxymethylene are blended with metal powder as feedstock. After mixing and hot pressing, diamond paste containing active brazing filler metal is precisely filled into the concave areas. Organic matter is removed through solvent degreasing and stepped thermal degreasing. Finally, matrix sintering and diamond brazing are simultaneously completed in a vacuum environment. This process can increase the lifespan of diamond tools by 2-3 times and is particularly suitable for high-end tool manufacturing in aerospace, superhard material processing, and other fields. Attached Figure Description

[0020] Figure 1 A schematic diagram of the process for preparing multilayer brazed diamond tools from thermoplastic resin. Detailed Implementation

[0021] Example 1: Iron-based three-layer diamond sintered block, metal powder: Fe80-Cu10-Sn5-Ni5 alloy 95wt% (D50=25μm, oxygen content<0.3%), binder system: polyoxymethylene (POM) 4wt% and polyethylene wax 1wt%, kneaded in a vacuum mixer at 180℃ for 40 minutes. After crushing and sieving, it was then molded. The mold was designed as a rectangular base with 320 inline circular recesses (2.0mm deep, 0.8mm in diameter) to accommodate single blocks. Pressing parameters: 150℃, 50MPa holding pressure for 5 minutes, green compact density reached 85% of the theoretical value. Then, diamond brazing paste was applied using a scraping method. Its main components were 10% wt of BNi-2 alloy powder (-300 mesh) + 80% wt of diamond (35 / 40 mesh) + 10% wt of terpineol, equivalent to a multi-layer brazing diamond with 3 layers of diamond. Degreasing treatment: Solvent degreasing: Trichloroethylene ultrasonic cleaning (40kHz×30min) to remove surface grease, followed by thermal degreasing: Under N2 protection, the temperature was increased in steps at 2℃ / min (200℃×1h + 400℃×2h), with residual carbon <0.1%. At 5×10 - Vacuum sintering was performed at 1030℃ for 30 minutes under the conditions of 3 Pa, 1030℃, and a heating rate of 5℃ / min. Example 2: Copper-based five-layer glass drill bit This embodiment provides a high-efficiency five-layer diamond drill bit for glass processing, employing a copper-based alloy system to achieve excellent thermal conductivity and anti-adhesion properties. The metal powder used is: Cu70-Fe10-Ni15 alloy (D50=20μm, oxygen content <0.2%) 50%; the binder system is: polyoxymethylene (POM) 45% + zinc stearate 5%; the diamond brazing paste is: Cu80Sn15Ti5 alloy powder (-400 mesh) 80% + diamond (50 / 60 mesh) 10% + ethyl cellulose 10%. The preparation process is as follows: mixing and internal mixing: mixing at 165℃ for 4 hours in a vacuum mixer, with a stable torque value of 28 N·m. The resulting feedstock is crushed and screened. Then, through mold design and hot pressing, the hot pressing parameters are: 200℃ × 10MPa holding pressure for 6 minutes, to obtain a green blank with 480 hexagonal grooves (2.8mm deep, 0.6mm distance between edges) on the cylindrical base surface. Diamond Coating: Precise filling using screen printing, with a coating amount of 18±1mg per groove. Degreasing Treatment: Solvent degreasing: Acetone ultrasonic cleaning (35kHz×25min). Thermal degreasing: Ar / H2 mixed atmosphere (H2 content 8%) with stepwise heating (180℃×1.5h + 380℃×2.5h). Vacuum Sintering: Parameters: 8×10⁻³Pa vacuum, 880℃×45min (heating rate 4℃ / min). Pressure Control: 1.2MPa axial pressure applied throughout. Performance Characteristics: Number of Diamond Layers: 5 layers (measured layer thickness 2.75mm), experiments show that a TiC transition layer is formed on the diamond surface. Cutting Performance: Life reaches 1200 holes when machining 5mm thick tempered glass, 3 times better than conventional drill bits. This embodiment, through the optimized design of copper-based materials and multi-layer diamond structure, significantly improves the heat dissipation performance and wear resistance of the drill bit in glass processing, making it particularly suitable for precision machining fields such as photovoltaic glass and cover glass.

[0022] Example 3: This embodiment provides a multi-layer diamond tool for machining high-hardness ceramics, employing a silver-based brazing filler metal to achieve high-strength connections and excellent thermal stability. The metal powder used is 70% Fe60-Cu30-Ni10 alloy (D50=18μm, oxygen content <0.25%), the binder system is 25% polyoxymethylene (POM) + 5% polyethylene wax, and the diamond brazing paste is 52% Ag65-Cu30-Ti5 alloy powder (-350 mesh) + 43% diamond (45 / 50 mesh) + 5% terpineol. The metal powder and binder are mixed in a vacuum mixer at 170°C for 38 minutes, achieving a stable torque value of 32 N·m. The obtained feed is screened and crushed. Design: 360 rectangular grooves (depth 2.2mm, length × width = 0.8 × 0.5mm) are set on the surface of the circular substrate. Hot pressing parameters: 160℃ × 14MPa holding pressure for 5min, the green density reaches 86% of the theoretical value. Diamond coating: adopts scraper printing process, coating amount of 15±1mg per groove. Degreasing treatment: Solvent degreasing: Trichloroethylene ultrasonic cleaning (38kHz×20min) Thermal degreasing: Under N2 protection, temperature is increased in steps at 10℃ / min (220℃×1h + 420℃×2h) Vacuum sintering: Vacuum degree: 6×10⁻³Pa, 820℃×40min (heating rate 5℃ / min) Final diamond layer count: 4 layers (measured layer thickness 2.15mm), forming a continuous and dense TiC transition layer (thickness 2-4μm) at the diamond-brazing interface. Machining performance: Tool life reaches 95 hours when machining alumina ceramics, which is 3.2 times better than conventional tools. Surface quality: Surface roughness Ra of the machined workpiece is ≤0.2μm. This embodiment achieves high-strength diamond bonding at a relatively low brazing temperature through the combination of silver-based brazing filler metal and multilayer structure, effectively avoiding thermal damage to diamond at high temperatures. It is particularly suitable for efficient machining of hard and brittle materials such as precision ceramics and silicon carbide.

Claims

1. A method for preparing a multilayer diamond brazing tool based on thermoplastic resin molding, characterized in that, The method includes the following steps: a) Mix thermoplastic resin and metal powder at 150-200℃ for 35 minutes to 4 hours to form a uniform feed, wherein the metal powder content is 50-95 wt%; b) After crushing the feed to a particle size of 0.2-2mm, hot press it at 150-200℃ and 10-50MPa to form a working layer matrix with a predetermined concave structure, wherein the depth of the concave part is 0.2-5mm. c) Fill the recess with diamond brazing paste, the brazing paste comprising 10-80 wt% abrasive particles, 20-80 wt% brazing alloy powder and 1-10 wt% organic carrier. d) Remove organic matter through a degreasing process; e) In a vacuum degree ≤ 1×10 - Simultaneous sintering and brazing are carried out under 2Pa conditions: the temperature is increased to 30-100℃ above the liquidus line of the brazing filler metal at 2-10℃ / min, and the temperature is held for 0.5-3 hours. The working layer substrate of the concave structure is sintered, and the diamond brazing paste is brazed. f) The sintered and brazed block is brazed onto the substrate.

2. The method according to claim 1, characterized in that, The depth H of the recess and the diamond grain size d satisfy the following relationship: H = n * (d + 0.2d), where n is an integer from 2 to 10.

3. The method according to claim 1, characterized in that, The solder alloy powder is an active solder, including Ag-Cu-Ti, Cu-Sn-Ti, Ni-Cr-B-Si, or Ni-Cr-P systems.

4. The method according to claim 1, characterized in that, The recessed structure is circular or hexagonal in shape, and the recess is filled with brazing by means of brazing paste or by adding diamond first and then brazing powder.

5. The method according to claim 1, characterized in that, Step a) The thermoplastic resin and metal powder also contain thermosetting resin and composite binder.

6. The method according to claim 1, characterized in that, The thermoplastic resin includes polyoxymethylene, polypropylene, or wax-based resin.

7. The method according to claim 1, characterized in that, The thermoplastic resin is a wax-based resin system. The degreasing process includes a two-stage degreasing process: solvent degreasing: soaking in trichloroethylene for 0.5-36 hours; thermal degreasing: heating to 400-600℃ at 1-10℃ / min and holding for 0.5-8 hours under an inert atmosphere.

8. The method according to claim 1, characterized in that, The thermoplastic resin is polyoxymethylene, and the degreasing method is degreasing by acid catalysis with nitric acid or oxalic acid.

9. The method according to claim 1, characterized in that, Step c) Fill the recess with diamond solder paste using screen printing, dispensing, or scraping methods.

10. The method according to claim 1, characterized in that, The hard abrasive grains include one or a composite abrasive of diamond, cubic boron nitride, cemented carbide, polycrystalline superhard material, and silicon carbide.

Images