Preparation method of diamond coated cutting tool

Abstract

A multi-layer filament structure matching adaptation process is adopted, specifically, a pretreatment scheme is customized according to cutter materials (high-speed steel, hard alloy and ceramic), Ta / W / Re high-temperature-resistant filaments are selected, grid type or same-direction multi-layer arrangement is designed according to the geometric shape of the cutter, and deformation is prevented and controlled through balance weight / spring tensioning; taking H2 and CH4 as reaction gases, depositing under the conditions of 850-1000 DEG C and 20-80 Torr, and adapting special parameters according to a drill bit, a milling cutter and a turning tool; and after cooling, the coating quality is ensured through multi-dimensional detection. According to the scheme, repeated deposition or a rotating mechanism is not needed, the coating uniformity is improved, the peeling risk is reduced, the preparation efficiency is improved, and the method is suitable for batch production.

Description

Technical Field

[0001] This invention relates to a method for preparing diamond-coated cutting tools, specifically to a hot filament structure and preparation method for improving the coating uniformity and preparation efficiency of diamond-coated cutting tools, belonging to the field of CVD diamond-coated cutting tool preparation technology. Background Technology

[0002] Cutting tools are used for machining in the machinery manufacturing industry, and their performance affects the quality, efficiency, and cost of machining. During machining, cutting tools need to withstand different pressures, impacts, and thermal loads. With the development of industries such as aerospace, shipbuilding, nuclear power, and automobiles, the processing volume of difficult-to-machine materials and carbon fiber materials in manufacturing is increasing, placing higher demands on cutting tools. CVD diamond-coated tools are a type of tool that uses the CVD method to deposit a diamond coating on its surface. Data shows that diamond-coated tools can have a service life more than 10 times that of uncoated tools, while their machining speed can be 2-3 times higher, making them a type of cutting tool with great application potential.

[0003] The main methods for preparing CVD diamond include HFCVD (hot filament CVD), MPCVD (microwave plasma CVD), and DCAPCVD (direct current arc plasma CVD). Among these, HFCVD has become the preferred method for preparing diamond coatings in CVD-coated tools due to its advantages such as simple equipment, easy process adjustment, large deposition area, and low cost. The HFCVD batch preparation technology for diamond-coated tools often uses a straight filament, employs a mold such as graphite to fix the tool, and places the tool tip between the hot filaments for coating deposition.

[0004] Because cutting tools are often non-planar, three-dimensional structures, it is difficult to obtain a uniform CVD diamond coating on the tool using HFCVD deposition with a straight filament. Typically, the coating thickness is greater on the side closest to the filament. On one hand, the thickness of the diamond coating affects the service life of the coated tool; the theoretical service life of CVD diamond-coated tools is limited by the thinner areas of the coating. On the other hand, inconsistent diamond coating thickness leads to inconsistent coating stress, which can easily cause peeling in stress transition areas, significantly reducing the actual service life of the tool.

[0005] To improve the uniformity of coating deposition, a spiral filament structure can be used to conform to the three-dimensional structure of the coating deposition area on the tool. However, the preparation of a spiral filament structure is relatively complex and inefficient, and the spiral structure is prone to deformation during deposition, leading to production failures. This structure was only adopted in the early stages of HFCVD diamond-coated tool research. In addition, the spiral structure requires a complex electrode structure, increasing equipment and operating costs, making it unsuitable for large-scale, large-area fabrication of coated tools.

[0006] In the field of materials preparation, rotation is a commonly used method to improve uniformity. Since CVD diamond coating tools typically involve multiple tools depositing simultaneously, with the tool tips positioned between hot filaments, a rotation mechanism needs to be placed below each tool. This undoubtedly increases the complexity of the deposition system and production costs significantly. Furthermore, adding a rotation structure does not improve coating uniformity along the tool axis.

[0007] Another feasible way to improve the coating uniformity of CVD diamond-coated tools is to use secondary or multiple depositions, reducing the thickness difference of the coating at different locations through deposition at multiple angles. Obviously, this method will reduce production efficiency and increase production costs. Furthermore, secondary or multiple depositions of diamond coatings can lead to delamination, posing a risk of peeling off at the interface during use and shortening the service life of the diamond-coated tools. Summary of the Invention

[0008] The technical problem this invention aims to solve is to address the above-mentioned shortcomings by providing a method for preparing diamond-coated cutting tools. Through the design of a multi-layer filament structure, the uniformity of the diamond coating on the tool is improved, reducing the probability of diamond coating peeling due to uneven deposition and improving the consistency of tool use. Simultaneously, the introduction of the multi-layer filament structure avoids the need for multiple deposition processes to improve uniformity, thus increasing the preparation efficiency of CVD diamond-coated cutting tools.

[0009] To solve the above technical problems, the present invention adopts the following technical solution:

[0010] A method for preparing a diamond-coated cutting tool includes the following steps:

[0011] Step 1, tool pretreatment: depending on the tool material type, the tool tip is placed in an acid or alkali solution to improve surface roughness and enhance the bonding strength between the coating and the tool body;

[0012] Step 2, Filament design and loading;

[0013] Step 3: Fixing and adjusting the position of the cutting tool;

[0014] Step 4, Equipment Preparation: Seal the HFCVD deposition equipment and check for leaks. Start the vacuum system and evacuate to 10°C. -3 Pa

[0015] Step 5: Introduce gas, introducing a mixture of H2 and CH4.

[0016] Step 6, Deposition process: Raise the filament temperature to 850-1000℃, dynamically adjust the process parameters according to the tool type to carry out deposition, and set the deposition time according to the target coating thickness.

[0017] Step 7, Cooling complete: After deposition is complete, slowly reduce the filament power and allow it to cool naturally to room temperature before removing the tool;

[0018] Step 8: Tool coating quality inspection.

[0019] Furthermore, the specific process of tool pretreatment in step 1 is as follows:

[0020] For high-speed steel cutting tools, use acetone for ultrasonic cleaning for 10-15 minutes to remove surface oil; then soak in 10% HCl solution for 1-3 minutes to roughen the surface and increase diamond nucleation density; finally rinse with deionized water and dry with nitrogen.

[0021] For cemented carbide cutting tools, use acetone for ultrasonic cleaning for 10-15 minutes to remove surface oil; then immerse in a mixed solution of H2SO4 and H2O2 for 30-90 seconds to remove the Co phase in the cemented carbide and roughen the surface; subsequently, use 10% NaOH solution to neutralize and remove residual acid from the tool surface to prevent further etching; then use Murakami reagent etching to enhance the bonding between the diamond and the tool; finally, rinse with deionized water and dry with nitrogen.

[0022] For ceramic cutting tools, use acetone for ultrasonic cleaning for 10-15 minutes to remove surface oil; then use HF acid to etch the tool for 1-2 minutes to remove the glass phase and roughen the surface to increase nucleation density and bonding force; finally, use Ar / O2 plasma to activate the surface to increase surface energy and increase nucleation sites.

[0023] Furthermore, step 2 includes the following steps:

[0024] Step 2.1, core parameters of the filament;

[0025] Filament material selection: High-temperature resistant materials such as tantalum, tungsten, and rhenium are selected, and their melting points must meet the high-temperature requirements of 850-1000℃ during the deposition process;

[0026] Filament size specifications: filament diameter 0.2-0.6mm.

[0027] Furthermore, step 2 also includes the following steps:

[0028] The filament arrangement uses a mesh pattern, suitable for cutting tools where the cross-section at the coating location has certain dimensions in both length and width, and the shortest side of the cross-section is greater than 10mm. The arrangement rule is that each layer of filaments is staggered, with each layer forming a 90° angle with the layer above it. The number of filament layers is calculated based on the height of the coating area, with one layer placed every 7-10mm.

[0029] Furthermore, step 2 also includes the following steps:

[0030] The filament arrangement method is to choose a multi-layer filament layout in the same direction, which is suitable for tools with a large cross-sectional length-to-width ratio at the coating position. The arrangement rule is that each layer of filaments is arranged in the same direction, with the top layer of filaments located at the top of the tool and the remaining filaments arranged downwards along the side.

[0031] Furthermore, step 2 also includes the following steps:

[0032] Filament tensioning structure and deformation control;

[0033] Counterweight tensioning: A counterweight is suspended at one end of each filament, with a weight of 2%-8% of the filament's tensile strength limit;

[0034] Spring tension:

[0035] Pretension calculation: Spring pretension = Expected tension / Spring stiffness coefficient + Filament high-temperature elongation;

[0036] Adjustable design: One end of the spring is connected to the external structure of the furnace or a mechanical adjustment structure is set up. With the help of a displacement sensor, the filament drooping is detected. When the drooping exceeds 0.5mm, the spring tension is increased in time.

[0037] Furthermore, in step 3, the tool is fixed by placing the pretreated tool into the graphite mold to ensure that the tool is stable in position during the deposition process and to avoid displacement.

[0038] Position calibration: Adjust the relative position of the filament and the tool to ensure that the multi-layer filaments uniformly cover the coating area of ​​the tool; the bottom filament is about 5mm away from the edge of the area to be coated.

[0039] Furthermore, in step 5, the volume ratio of H2 to CH4 introduced is 92-98:2-8, and the gas flow rate is adjusted to make the pressure inside the equipment reach 20-80 Torr.

[0040] Furthermore, in step 6, the process parameters are dynamically adjusted according to the application of the tool to initiate the deposition reaction. The process parameters for different types of tools are adjusted as follows:

[0041] Drill bit: CH4 to H2 volume ratio 5-8:92-95, pressure 50-80 Torr, temperature 850-900℃;

[0042] End mill: Deposition pressure 20-50 Torr and slowly increases during deposition; CH4 volume percentage is 2%-3% in the initial stage and then increases to 4%-5%; deposition temperature 850-950℃.

[0043] Cutting tool: CH4 volume fraction 2%-3%, deposition temperature 900-1000℃, pressure 60-80 Torr.

[0044] Furthermore, in step 8, the thickness uniformity is tested by ball milling, the grain size is calculated by XRD combined with Scherer's formula, and the bonding force is tested by scratch test. During the initial judgment of the production line, the thickness is tested by film thickness gauge, the bonding force is tested by cross-cut test, and the coating hardness is measured by pencil hardness tester.

[0045] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0046] 1. Significantly improves coating uniformity and reduces the risk of peeling;

[0047] To address the structural characteristics of non-planar three-dimensional cutting tools, a mesh-like or unidirectional multi-layer filament arrangement is adopted to form a uniform coverage of the tool coating area. This solves the problem of "thicker coating near the filament and thinner coating at the far end" caused by traditional straight filaments, keeping the coating thickness deviation within ±10% and avoiding inconsistent stress caused by uneven thickness.

[0048] The uniform coating structure reduces the formation of stress transition zones, significantly reducing the probability of diamond coating peeling due to stress concentration during use. It also improves the consistency of use of mass-produced tools, ensuring stable and uniform performance of each tool.

[0049] II. Improve preparation efficiency and reduce production costs;

[0050] The multi-layer filament structure eliminates the need for complex solutions such as traditional secondary / multiple deposition, rotating mechanisms, or spiral filaments. It achieves uniform coating with a single deposition, avoiding the efficiency loss caused by multiple depositions and significantly improving the batch production efficiency of CVD diamond coated tools.

[0051] The filament adopts a straight structure with a simple tensioning device (counterweight or spring tensioning). Compared with spiral filaments, it has a simpler structure, is easier to manufacture, has a lower risk of deformation, and does not require a complex electrode structure, thus reducing equipment investment and operating costs. At the same time, it avoids the increased system complexity brought about by the rotating mechanism, further controlling production energy consumption and maintenance costs.

[0052] III. Optimize coating performance to adapt to the needs of different cutting tools;

[0053] By employing targeted tool pretreatment processes (customized treatment solutions for high-speed steel, cemented carbide, and ceramic materials), we ensure that the surface cleanliness, roughness, and activity of the tool meet the deposition requirements, thereby enhancing the adhesion between the coating and the tool body. Scratch testing revealed no large-area peeling.

[0054] During the deposition process, the process parameters are dynamically adjusted according to the tool type (drill bit, milling cutter, turning tool) to achieve specific properties such as high hardness and high toughness, low internal stress and impact resistance, and high wear resistance. This ensures that the coating performance is precisely matched with the tool's usage scenario, extending the tool's service life—more than 10 times longer than uncoated tools, and increasing the processing speed by 2-3 times.

[0055] IV. The process is stable and reliable, and suitable for mass production;

[0056] The filament is made of high-temperature resistant materials such as Ta, W, and Re, and is equipped with a scientific tension control design (constant force tensioning with counterweight or spring pre-compensation + displacement sensor adjustment) to effectively avoid filament deformation during the high-temperature deposition process and ensure production continuity.

[0057] Standardized gas ratio (H2 to CH4 volume ratio 92-98:2-8), vacuum environment control (10 -3 The process includes a Pa) and cooling flow (slow power reduction + natural cooling) to ensure a stable and controllable deposition process, reduce the defect rate caused by process fluctuations, and adapt to the needs of large-scale, large-area production.

[0058] V. The coating quality meets the standards and its performance indicators are excellent.

[0059] Testing revealed that the coating exhibits high diamond phase purity (non-diamond phase peak percentage is less than 5% in Raman testing), internal stress is less than 1 GPa, and grain size is precisely controlled according to the tool application (50-150nm for drills, 100-300nm for milling cutters, and 0.5-3μm for lathe tools), while also considering core properties such as hardness, toughness, and wear resistance.

[0060] After pretreatment, the tool surface is clean and dry (water droplet contact angle <10%, moisture content <0.01mg / cm²), and the roughness is suitable (50-100nm), providing a good substrate for coating deposition and further ensuring the overall performance of the coating. Attached Figure Description

[0061] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0062] Figure 1 This is a schematic diagram of the filament mesh arrangement in this invention;

[0063] Figure 2 This is a schematic diagram of the unidirectional multilayer filament layout in this invention. Detailed Implementation

[0064] An example of a method for preparing a diamond-coated cutting tool includes the following steps:

[0065] Step 1, Tool Pretreatment: Depending on the tool material type, the tool tip is placed in an acid or alkaline solution to increase surface roughness and enhance the bonding strength between the coating and the tool body. If necessary, measures are taken to test the surface cleanliness and roughness of the tool after pretreatment. The specific process is as follows:

[0066] Different pretreatments are required for different materials of cutting tools in order to achieve similar or identical deposition effects.

[0067] For high-speed steel cutting tools, use acetone for ultrasonic cleaning for 10-15 minutes to remove surface oil; then soak in 10% HCl solution for 1-3 minutes to roughen the surface and increase diamond nucleation density; finally rinse with deionized water and dry with nitrogen.

[0068] For cemented carbide cutting tools, use acetone for ultrasonic cleaning for 10-15 minutes to remove surface oil; then immerse in a mixed solution of H2SO4 and H2O2 for 30-90 seconds to remove the Co phase in the cemented carbide (thus preventing Co from catalyzing diamond graphitization during deposition) and roughen the surface; subsequently, use 10% NaOH solution to neutralize and remove residual acid from the tool surface to prevent further etching; then etch with Murakami reagent to enhance the bonding between diamond and the tool; finally, rinse with deionized water and dry with nitrogen.

[0069] For ceramic cutting tools, use acetone for ultrasonic cleaning for 10-15 minutes to remove surface oil; then use HF acid to etch the tool for 1-2 minutes to remove the glass phase and roughen the surface to increase nucleation density and bonding force; finally, use Ar / O2 plasma to activate the surface to increase surface energy and increase nucleation sites.

[0070] After the above treatment, the tool surface should achieve the following effect:

[0071] Surface clean and dry: water droplet contact angle <10°, moisture content less than 0.01 mg / cm³ 2 ;

[0072] Non-diamond has low carbon contamination: the proportion of CC peaks in XPS tests is relatively low;

[0073] Suitable surface roughness: roughness test range is 50-100 nm;

[0074] Low surface Co content (for cemented carbide): EDS semi-quantitative detection showed a content of less than 0.5%.

[0075] For the above-mentioned verified solutions, in actual production, in addition to sampling, the following simple method can be used for preliminary judgment: Immerse the treated knife in water and then take it out. Observe whether the water film is well maintained, which can determine the surface cleanliness; observe the surface roughness under light. The surface morphology should be uniform.

[0076] Step 2, Filament design and loading;

[0077] Step 2.1, core parameters of the filament;

[0078] Filament material selection: High-temperature resistant materials such as Ta (tantalum), W (tungsten), and Re (rhenium) are selected, and the melting point must meet the high temperature requirements of 850-1000℃ during the deposition process.

[0079] Filament size specifications: filament diameter 0.2-0.6mm. If the filament diameter is too small, it is easy to melt at high temperature. If the diameter is too large, the heat generation is too small and it is not enough to effectively deposit diamond. The filament length is adjusted according to the equipment size and the size of the deposition area to ensure full utilization of the equipment space.

[0080] Step 2.2, Filament arrangement selection: Design the filament arrangement according to the geometry of the tool to cover the tool as much as possible;

[0081] Mesh filament arrangement, such as Figure 1 As shown;

[0082] Applicable scenarios: The length and width of the cross-section at the coating location of the tool have certain dimensions (such as a circular cross-section, or the shortest side length of the cross-section is >10mm).

[0083] Arrangement rules: Each layer of filaments is crisscrossed, with each layer at a 90° angle to the previous one. For example, the second layer is at a 90° angle to the first layer, and the third layer is parallel to the first layer. The two ends of the filaments are connected to the positive and negative terminals of the power supply and are tensioned and straightened by a spring structure or counterweight.

[0084] Location and number of layers: The number of filament layers is determined by the height of the coating area of ​​the blade tip.

[0085] The topmost filament is located at the tip of the tool and is used to deposit a diamond coating on the tip of the tool, at a distance of 4-5 mm from the tip of the tool. The remaining filaments are arranged downwards around the coated area of ​​the tool and are used to deposit a diamond coating on the side of the tool. The number of layers is calculated according to the height of the coated area, with one filament placed every 7-10 mm.

[0086] Co-directional multi-layer filament layout, such as Figure 2 As shown;

[0087] Applicable scenarios: Cutting tools (such as blades) with a large aspect ratio at the coating location.

[0088] Arrangement rules: Each layer of filaments is arranged in the same direction, with the two ends of the filaments connected to the positive and negative terminals of the power supply, and tensioned and straightened by a spring structure or counterweight.

[0089] Positioning: The topmost filament is located at the top of the cutter, and the remaining filaments are arranged downwards along the side.

[0090] Step 2.3, Filament tensioning structure and deformation control;

[0091] Counterweight tensioning: A counterweight is suspended at one end of each filament, with a weight of 2%-8% of the filament's tensile strength limit (e.g., the tensile strength limit of a 0.3mm diameter filament is approximately 25N; when taking 4% of the tensile strength value, the counterweight weight needs to reach 1N, i.e., 100g), to ensure constant tension.

[0092] Spring tension:

[0093] Pretension calculation: Spring pretension = expected tension / spring stiffness coefficient + filament high-temperature elongation. The thermal expansion caused by high temperature is considered and compensated for in advance during the spring installation process.

[0094] Adjustable design: One end of the spring is connected to the external structure of the furnace or a mechanical adjustment structure is set up. With the help of a displacement sensor, the filament drooping is detected. When the drooping exceeds 0.5mm, the spring tension is increased in time.

[0095] Step 3: Fixing and adjusting the position of the cutting tool;

[0096] Fixing method: Place the pre-treated tool into the graphite mold to ensure that the tool is in a stable position during the deposition process and avoid displacement.

[0097] Position calibration: Adjust the relative position of the filament and the tool to ensure that the multi-layer filaments uniformly cover the coating area of ​​the tool; the bottom filament is about 5mm away from the edge of the area to be coated.

[0098] Step 4, Equipment Preparation;

[0099] Seal the HFCVD deposition equipment, check the equipment's seal, and prevent gas leakage.

[0100] Start the vacuum system and evacuate to 10. -3 Pa, thoroughly removes air and impurities from the equipment to avoid affecting the coating quality.

[0101] Step 5: Gas is introduced;

[0102] Gas ratio: A mixture of H2 and CH4 is introduced in a volume ratio of 92-98:2-8. CH4 is the carbon source, and H2 is used to decompose and generate active hydrogen atoms to inhibit the formation of the graphite phase.

[0103] Pressure control: Adjust the gas flow rate to maintain the internal pressure of the equipment at 20-80 Torr, providing a stable gas pressure environment for the deposition reaction.

[0104] Step 6, deposition process;

[0105] The process parameters are dynamically adjusted according to the application of the cutting tool to initiate the deposition reaction. The core controls are as follows:

[0106] Step 6.1, General Parameters;

[0107] The increased filament power raises the filament temperature to 850-1000℃. At this high temperature, H2 decomposes into [H] active atoms, and CH4 decomposes into C-containing groups, which deposit on the tool surface to form a diamond coating. The deposition time is set according to the target coating thickness.

[0108] Step 6.2, adjust specific parameters to match the tool type;

[0109] Drill bits: High-speed cutting requires high hardness and high toughness. Deposition necessitates increased nucleation density: Increased nucleation density refines grains, increases hardness, and simultaneously increases the number of grain boundaries, effectively suppressing crack propagation and improving toughness. Specifically, this involves increasing methane concentration, decreasing temperature, and increasing pressure, i.e., a CH4:H2 volume ratio of 5-8:92-95, a pressure of 50-80 Torr, and a temperature of 850-900℃.

[0110] Milling cutters: These require good impact resistance and need to reduce the internal stress of the coating. High internal stress, combined with the stress under milling cutter operating conditions, can lead to crack initiation and coating peeling. In terms of process, the deposition pressure can be selected from 20-50 Torr and gradually increased during deposition to promote lateral grain growth and reduce grain boundaries. The methane volume percentage can be selected from 2%-5%, initially at 2%-3% for nucleation, then increased to 4%-5% to further promote lateral grain growth and reduce grain boundaries. The deposition temperature can be selected from 850-950℃.

[0111] Lathe tools: The coating requires better wear resistance, which can be achieved by increasing the grain size: larger grains have fewer grain boundaries, making them less prone to peeling. Specifically, the methane concentration should be 2%-3%, the deposition temperature 900-1000℃, and the pressure 60-80 Torr.

[0112] Step 7, cooling complete;

[0113] After the target thickness is reached, the filament power is gradually reduced to avoid stress cracks in the coating caused by a sudden drop in temperature.

[0114] After the equipment has cooled to room temperature, open it and remove the blades to avoid contact with air at high temperatures, which could cause the coating to oxidize.

[0115] Step 8, Tool coating quality inspection;

[0116] The coating performance is verified through multi-dimensional testing to ensure it meets usage requirements. The testing items and standards are as follows:

[0117] Thickness uniformity: Two concentric circles are ground on the tool surface using a ball milling method. One circle is formed by the ball and the coating surface, and the other is formed by the ball and the tool body. The coating thickness is obtained from the diameters of the two circles. Thickness uniformity is judged by multi-point measurements, and the deviation is usually required to be <±10%.

[0118] Grain size: XRD curves of diamond were obtained using the XRD method, and the grain size was determined according to the Scherer formula. For drill bits, the grain size was 50-150 nm; for end mills, the grain size was 100-300 nm; and for turning tools, the grain size was 0.5-3 μm.

[0119] Diamond phase purity and stress: determined by Raman spectroscopy. The proportion of non-diamond phase peaks in the Raman curve was less than 5%. The stress obtained from the diamond peak displacement was less than 1 GPa.

[0120] Bonding strength: No large-area peeling occurs when using the scratch test.

[0121] In actual production lines, a film thickness gauge can be used to make a preliminary judgment on the thickness, a cross-cut test can be used to make a preliminary judgment on the adhesion, and a pencil hardness tester can be used to measure the hardness of the diamond coating.

[0122] The considerations for using a multi-layer hot filament structure in this patent to deposit CVD diamond coatings on non-planar three-dimensional tools are as follows:

[0123] In the HFCVD deposition system, the hot filament serves as the heat source and the energy source for the decomposition of H2 and CH4 gases. This determines that the distribution of [H] and C-containing group concentrations gradually decreases along the radial direction of the filament. Therefore, the thickness of the deposited diamond coating also decreases as the distance from the filament increases.

[0124] In typical HFCVD deposition systems, the filaments are arranged in a planar manner, which is very suitable for the deposition of planar coatings, and the rotation of the deposition stage can effectively improve uniformity. When depositing diamond coatings on tools with three-dimensional structures, uneven coating thickness is inevitable, and the setting of a rotating structure is more difficult, making it hard to improve uniformity through rotation. In addition, unevenness perpendicular to the stage direction cannot be improved by rotation.

[0125] By employing a multi-layered filament structure, the thickness uniformity in the vertical direction of the base can be improved. Furthermore, the enclosed filament structure enhances uniformity within the plane. Simultaneously, this design does not alter the straight alignment of the filament, thus minimizing the probability of filament deformation.

[0126] The description of this invention is given for illustrative and descriptive purposes only and is not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention and to enable those skilled in the art to understand the invention and design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A method for preparing a diamond-coated cutting tool, characterized in that: Includes the following steps: Step 1, tool pretreatment: depending on the tool material type, place the tool tip in an acid or alkali solution to improve surface roughness and enhance the bonding strength between the coating and the tool body; Step 2, Filament design and loading; Step 3: Fixing and adjusting the position of the cutting tool; Step 4, Equipment Preparation: Seal the HFCVD deposition equipment and check for leaks. Start the vacuum system and evacuate to 10°C. -3 Pa Step 5: Introduce gas, introducing a mixture of H2 and CH4 gas; Step 6, Deposition process: Raise the filament temperature to 850-1000℃, dynamically adjust the process parameters according to the tool type to carry out deposition, and set the deposition time according to the target coating thickness. Step 7, Cooling complete: After deposition is complete, slowly reduce the filament power and allow it to cool naturally to room temperature before removing the tool; Step 8: Tool coating quality inspection.

2. The method for preparing a diamond-coated cutting tool as described in claim 1, characterized in that: The specific process of tool pretreatment in step 1 is as follows: For high-speed steel cutting tools, use acetone for ultrasonic cleaning for 10-15 minutes to remove surface oil; then soak in 10% HCl solution for 1-3 minutes to roughen the surface and increase diamond nucleation density; finally rinse with deionized water and dry with nitrogen. For cemented carbide cutting tools, use acetone for ultrasonic cleaning for 10-15 minutes to remove surface oil; then immerse in a mixed solution of H2SO4 and H2O2 for 30-90 seconds to remove the Co phase from the cemented carbide and roughen the surface; subsequently, use 10% NaOH solution to neutralize and remove residual acid from the tool surface to prevent further etching; then use Murakami reagent etching to enhance the bonding between the diamond and the tool; finally, rinse with deionized water and dry with nitrogen. For ceramic cutting tools, use acetone for ultrasonic cleaning for 10-15 minutes to remove surface oil; then use HF acid to etch the tool for 1-2 minutes to remove the glass phase and roughen the surface to increase nucleation density and bonding force; finally, use Ar / O2 plasma to activate the surface to increase surface energy and increase nucleation sites.

3. The method for preparing a diamond-coated cutting tool as described in claim 1, characterized in that: Step 2 includes the following steps: Step 2.1, core parameters of the filament; Filament material selection: High-temperature resistant materials such as tantalum, tungsten, and rhenium are selected, and their melting points must meet the high-temperature requirements of 850-1000℃ during the deposition process; Filament size specifications: filament diameter 0.2-0.6mm.

4. The method for preparing a diamond-coated cutting tool as described in claim 1, characterized in that: Step 2 also includes the following steps: The filament arrangement method is to choose a mesh filament arrangement, which is suitable for tools with certain dimensions in both length and width of the coating area and the shortest side length of the cross section is >10mm. The arrangement rule is that each layer of filaments is crisscrossed, with the next layer forming a 90° angle with the previous layer. The number of filament layers is calculated according to the height of the coating area, with one layer set every 7-10mm.

5. The method for preparing a diamond-coated cutting tool as described in claim 1, characterized in that: Step 2 also includes the following steps: The filament arrangement method is to choose a multi-layer filament layout in the same direction, which is suitable for tools with a large cross-sectional length-to-width ratio at the coating position. The arrangement rule is that each layer of filaments is arranged in the same direction, with the top layer of filaments located at the top of the tool and the remaining filaments arranged downwards along the side.

6. The method for preparing a diamond-coated cutting tool as described in claim 1, characterized in that: Step 2 also includes the following steps: Filament tensioning structure and deformation control; Counterweight tensioning: A counterweight is suspended at one end of each filament, with a weight of 2%-8% of the filament's tensile strength limit; Spring tension: Pretension calculation: Spring pretension = Expected tension / Spring stiffness coefficient + Filament high-temperature elongation; Adjustable design: One end of the spring is connected to the external structure of the furnace or a mechanical adjustment structure is set up. With the help of a displacement sensor, the filament drooping is detected. When the drooping exceeds 0.5mm, the spring tension is increased in time.

7. The method for preparing a diamond-coated cutting tool as described in claim 1, characterized in that: In step 3, the tool is fixed by placing the pre-treated tool into the graphite mold to ensure that the tool is stable in position during the deposition process and to avoid displacement. Position calibration: Adjust the relative position of the filament and the tool to ensure that the multi-layer filaments uniformly cover the coating area of ​​the tool; the bottom filament is about 5mm away from the edge of the area to be coated.

8. The method for preparing a diamond-coated cutting tool as described in claim 1, characterized in that: In step 5, the volume ratio of H2 to CH4 introduced is 92-98:2-8. The gas flow rate is adjusted to bring the pressure inside the equipment to 20-80 Torr.

9. The method for preparing a diamond-coated cutting tool as described in claim 1, characterized in that: In step 6, the process parameters are dynamically adjusted according to the application of the tool to initiate the deposition reaction. The process parameters for different types of tools are adjusted as follows: Drill bit: CH4 to H2 volume ratio 5-8:92-95, pressure 50-80 Torr, temperature 850-900℃; End mill: Deposition pressure 20-50 Torr and slowly increases during deposition; CH4 volume percentage is 2%-3% in the initial stage and then increases to 4%-5%; deposition temperature 850-950℃. Cutting tool: CH4 volume fraction 2%-3%, deposition temperature 900-1000℃, pressure 60-80 Torr.

10. The method for preparing a diamond-coated cutting tool as described in claim 1, characterized in that: In step 8, the thickness uniformity is tested by ball milling, the grain size is calculated by XRD combined with Scherer's formula, and the adhesion is tested by scratch test. During the initial judgment of the production line, the thickness is tested by film thickness gauge, the adhesion is tested by scratch test, and the coating hardness is measured by pencil hardness tester.

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