Microwave plasma deposition apparatus and method for tool diamond film deposition

Abstract

The application discloses a microwave plasma deposition device and method for tool diamond film deposition, and belongs to the technical field of tool corrosion-resistant treatment. The device comprises a shell, a gas path control system, a vacuum cavity system, a tool clamping system and a symmetrically arranged microwave generation and transmission system; uniform distribution and accurate proportioning of reaction gas are realized by optimizing the gas path structure, the symmetric microwave system guarantees the stability of the plasma environment, the electrode applying cyclic alternating voltage accurately controls the directional migration of active groups, the tool clamping system matched with the posture control realizes the uniform and ordered deposition of active groups on the surface of the tool substrate; and the deposition method adopting the device is also disclosed, and a diamond film tool with high toughness and uniformity can be prepared.

Description

Technical Field

[0001] This invention relates to a microwave plasma deposition apparatus and method for diamond film deposition on cutting tools, belonging to the field of cutting tool corrosion resistance treatment technology. Background Technology

[0002] Microwave plasma chemical vapor deposition (MPCVD) technology has become the mainstream technology for preparing high-quality diamond films due to its advantages such as high plasma purity, concentrated energy, and controllable deposition temperature. Its core principle is to use microwaves of a specific frequency to excite a mixture of CH4 and H2 gases in a vacuum chamber to form a high-density plasma. Active groups such as carbon and hydrogen radicals in the plasma undergo crystallization and deposition reactions on the tool substrate surface, ultimately forming a diamond film with high hardness and high wear resistance, which can significantly improve the cutting performance and service life of the tool.

[0003] However, existing MPCVD devices still face several technical bottlenecks in practical applications: First, the gas path system design is unreasonable, easily generating eddies during gas transmission, leading to uneven gas distribution within the cavity, resulting in large deviations in film thickness and uneven composition. Second, poor plasma stability, low microwave energy transmission efficiency, and excessively high reflected power cause large fluctuations in the concentration of active groups, affecting the crystallization quality of the film. Third, the tool clamping method is singular, unable to achieve multi-dimensional attitude control, resulting in incomplete film coverage for complex-shaped tools, and insufficient temperature control precision, leading to stress concentration within the film and making it prone to cracking and detachment. Fourth, the fracture toughness of diamond films prepared by existing devices is generally lower than 12 MPa. m 1 / 2 This makes it difficult to meet the needs of high-end fields such as aerospace and automobile manufacturing for long-life, impact-resistant cutting tools.

[0004] Therefore, how to provide an MPCVD device that can achieve uniform gas distribution, precise plasma control, flexible tool clamping, and temperature regulation is one of the technical problems that urgently need to be solved by those skilled in the art. Summary of the Invention

[0005] The MPCVD device proposed in this invention achieves uniform distribution and precise ratio of reactant gases by optimizing the structure of the gas path control system. It ensures the stability of the plasma environment by using a symmetrically arranged microwave generation and transmission system. It precisely controls the directional migration and deposition of active groups by using a pair of electrodes with alternating voltages. Combined with a multi-dimensional attitude control tool clamping system, the active groups can undergo uniform and orderly deposition reactions on the tool substrate surface, ultimately producing a diamond thin film tool with high toughness and high uniformity.

[0006] This invention addresses the problems of unreasonable gas path design, poor plasma stability, limited tool clamping methods, and poor film fracture toughness in existing MPCVD devices by providing a microwave plasma deposition apparatus and method for diamond film deposition on tools.

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: a microwave plasma deposition apparatus for diamond film deposition in cutting tools, comprising: The outer casing, gas path control system, vacuum chamber system, tool clamping system, and microwave generation and transmission system; The tool clamping system and the vacuum chamber system are located inside the outer shell; The gas circuit control system includes interconnected gas transmission channels and an air inlet base. The gas transmission channel is connected to the air inlet base; The gas path control system is movably connected to the vacuum chamber via the air inlet base; The vacuum chamber system includes a vacuum chamber shell, a temperature controller, a drive motor, a first electrode, and a cover plate; The vacuum chamber housing is rotatably connected to the air inlet base, the first electrode is connected to the vacuum chamber housing, and the temperature controller is disposed inside the vacuum chamber housing. The vacuum chamber shell includes an air passage, an air inlet cavity, a deposition cavity, a positioning groove, a first air outlet, and a second air outlet; The air intake cavity is connected to the deposition cavity through a first air outlet; the air intake cavity is also connected to the deposition cavity in sequence through an air passage and a second air outlet. The air intake cavity, the deposition cavity, and the air passage are arranged coaxially, and the air passage is arranged around the deposition cavity. The temperature controller is located at the bottom of the deposition cavity; The drive motor is rotatably connected to the vacuum chamber housing; The first electrode is disposed on the outer wall of the vacuum chamber shell, and the cover plate is disposed on the top of the vacuum chamber shell; The cover plate is provided with an opening, through which the tool clamping system extends into the deposition cavity; The tool clamping system includes a tool clamp, a rotation controller, and a second electrode; The tool holder is located below the rotation controller, and the second electrode is located on the transverse outer wall of the rotation controller. The rotation controller integrates a rotation motor and a vibrator. The microwave generation and transmission system includes a microwave source, a circulator, a three-screw impedance tuner, an analog conversion antenna, and a microwave system mounting component. The microwave source, circulator, three-screw impedance tuner, analog conversion antenna, and microwave system mounting part are connected in sequence. There are two sets of microwave generation and transmission systems. The microwave system fixing parts of the two sets of microwave generation and transmission systems are fixed to the reserved interface in the middle of the upper part of the outer shell.

[0008] Preferably, there are four drive motors, which are evenly spaced on the bottom surface of the lower housing and rotatably connected to the vacuum chamber system.

[0009] Preferably, the outer shell is formed by splicing an upper shell and a lower shell together using flanges.

[0010] Preferably, the temperature controller integrates a temperature sensor and a heater.

[0011] The present invention also provides a method for depositing a diamond film using the above-described apparatus as a cutting tool, comprising the following steps: S1. Open the cover plate, fix the tool to be deposited in the tool clamping system, and then close the cover plate to seal; S2. Evacuate the vacuum chamber system and start the gas path control system to introduce CH4 and H2 into the vacuum chamber system; S3. Start the microwave generation and transmission system and energize the first and second electrodes; S4. Start the drive motor and rotation controller, start the temperature controller to heat the vacuum chamber system, and perform the diamond film deposition.

[0012] Preferably, the vacuum level achieved in step S2 is 5 × 10⁻⁶. -³ Pa.

[0013] Preferably, the volume ratio of CH4 to H2 in step S2 is 1:15.

[0014] Preferably, the gas pressure after CH4 and H2 are introduced in step S2 is 4 kPa.

[0015] Preferably, in step S3, the voltage of the first electrode and the second electrode alternates between -30V and 30V; the period of the alternation is 10s-60s.

[0016] More preferably, the period is 30s, wherein the first electrode is energized for 15s and the second electrode is energized for 15s.

[0017] Preferably, the heating temperature in step S4 is 945-955°C.

[0018] Preferably, the deposition time in step S4 is 0.5h-10h.

[0019] The deposition time mentioned above affects the coating thickness range from 1 μm to 20 μm. This range is the most commonly used range for industrial tool coatings, balancing coating quality, preparation efficiency, and service life. Among them, 4 hours is the optimal deposition time, corresponding to a diamond coating thickness of 8 μm ± 0.5 μm.

[0020] Preferably, the method for depositing a diamond film using the above-described apparatus further includes the step of shutting down the apparatus: First, turn off the microwave source, then turn off the first and second electrodes, then turn off the drive motor and rotation controller, and finally turn off the gas path control system; after the vacuum chamber system has cooled to room temperature naturally, open the vacuum chamber system to restore the pressure inside the chamber to atmospheric pressure; loosen the cover plate, take out the tool, and you can obtain the tool with deposited diamond film.

[0021] The beneficial effects of this invention are as follows: The MPCVD device proposed in this invention achieves uniform distribution and precise ratio of reaction gases by optimizing the structure of the gas path control system, ensures the stability of the plasma environment by using a symmetrically arranged microwave generation and transmission system, precisely controls the directional migration and deposition of active groups by using a pair of electrodes with alternating voltages, and combines it with a multi-dimensional attitude control tool clamping system to enable active groups to undergo uniform and orderly deposition reactions on the tool substrate surface, ultimately producing a diamond thin film tool with high toughness and high uniformity. The aforementioned MPCVD equipment can control the coating thickness of the workpiece within the range of 1-20 μm and the fracture toughness to 14.2 MPa. m 1 / 2 -16.8MPa m 1 / 2 Hardness 80-96 GPa, elastic modulus 960-1050 GPa, and grain size 0.05-10 μm. Attached Figure Description

[0022] Figure 1 This is a cross-sectional view of a microwave plasma deposition apparatus for diamond film deposition in cutting tools provided by the present invention, wherein the cross-section is the plane containing the axes of the two gas transmission channels; Figure 2 This is a cross-sectional view of a microwave plasma deposition apparatus for diamond film deposition in cutting tools provided by the present invention, wherein the cross-section is the plane containing the axis of the drive motor and the axis of the apparatus; Figure 3 A three-dimensional view showing the bottom surface of the vacuum chamber shell; Figure 4 A three-dimensional view showing the top surface of the vacuum chamber shell; Figure 5 A perspective view of a microwave plasma deposition apparatus for diamond film deposition in cutting tools provided by the present invention; Figure 6 This is a SEM image of the coating on the tip arc portion of a cutting tool with a deposited diamond film obtained in an embodiment of the present invention; Figure 7 This is a SEM image of the coating on the main cutting edge of the diamond film-coated cutting tool obtained in an embodiment of the present invention. Figure 8 This is a SEM image of the coating on the bottom surface of the chip groove of a cutting tool with a deposited diamond film, obtained in an embodiment of the present invention. Figure 9 This is a SEM image of the coating on the outer cylindrical surface of the tool holder with deposited diamond film obtained in an embodiment of the present invention. Figure 10 This is a SEM image of the coating at the center of the end face of a tool with a deposited diamond film obtained in an embodiment of the present invention. The reference numerals in the attached drawings are as follows: 101, gas transmission channel; 102, air inlet base; 201, vacuum chamber shell; 202, first electrode; 203, cover plate; 204, gas passage; 205, air inlet cavity; 206, deposition cavity; 207, positioning groove; 208, first air outlet; 209, second air outlet; 210, temperature controller; 211, drive motor; 301, tool holder; 302, rotation controller; 303, second electrode; 401, microwave source; 402, circulator; 403, three-screw impedance tuner; 404, analog conversion antenna; 405, microwave system fixing part; 501, upper shell; 502, lower shell. Detailed Implementation

[0023] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0024] Example 1 This embodiment provides a microwave plasma deposition apparatus for diamond film deposition on cutting tools, including a housing, a gas path control system, a vacuum chamber system, a tool clamping system, and a microwave generation and transmission system. The gas path control system includes a gas transmission channel 101 and an inlet base 102, wherein the gas transmission channel 101 is connected to the bottom surface of the inlet base 102 via two pipes. The vacuum chamber system includes a vacuum chamber housing 201, a temperature controller 210, and a first electrode 202. The inlet base 102 is coaxially rotatably connected to the vacuum chamber housing 201 via a positioning groove 207, allowing the vacuum chamber housing 201 to rotate on the inlet base 102. Specifically, a second gear is connected to the bottom of the vacuum chamber housing 201, and drive motors 211 are distributed around the vacuum chamber housing 201. A first gear is connected to the output end of the drive motors 211, and the first gear meshes with the second gear to drive the vacuum chamber housing 201 to rotate relative to the inlet base 102. (See attached...) Figure 1In the indicated orientation, the inner cavity formed by the vacuum chamber shell 201 and the air inlet base 102 is divided into an air inlet cavity 205 and a deposition cavity 206. The deposition cavity 206 is located above the air inlet cavity 205, and the gas transmission channel 101 is connected to the air inlet cavity 205 through two pipes. A partition is formed between the deposition cavity 206 and the air inlet cavity 205, and a first air outlet 208 for connecting the deposition cavity 206 and the air inlet cavity 205 is provided on the partition. The first air outlet 208 is distributed in a circular array. The vacuum chamber shell 201 is further arrayed with air channels 204 along its circumference. The cross-section of the air channels 204 is fan-shaped. The air channels 204 extend from the inlet cavity 205 to the deposition cavity 206. A second outlet 209 is provided on the side wall of the deposition cavity 206. The second outlet 209 is arrayed along the axial and circumferential directions and is interconnected with the air channels 204. The inlet cavity 205 is connected to the deposition cavity 206 through the air channels 204 and the second outlet 209. The inlet cavity 205 is used to mix the gas introduced by the gas transmission channel 101 and to disperse the pressure. An annular temperature controller 210 is provided inside the deposition cavity 206 to detect the temperature inside the deposition cavity 206 and to heat and stabilize the internal temperature of the deposition cavity 206. The vacuum chamber shell 201 includes a main body and a transparent glass cover plate 203 for sealing the inner cavity of the main body. A first electrode 202 is provided on the outer wall of the vacuum chamber shell 201. A voltage can be applied to the first electrode 202, forming a voltage difference with the voltage applied to the second electrode 303, which can accelerate the adsorption of ionized gas groups. The first electrode 202 extends in a wave shape to ensure the length of the first electrode 202.

[0025] The tool clamping system includes a tool clamp 301, a rotation controller 302, and a second electrode 303. The tool clamp 301 is used to fix the tool to be deposited. The tool clamp 301 can pass through the cover plate 203 and be coaxially connected to the rotation controller 302. The tool clamp 301 is driven by the rotation motor and vibrator built into the rotation controller 302 to realize the vibration and rotation of the tool to be deposited. The tool clamp 301 is also provided with a second electrode 303 surrounding it. The voltage difference between the second electrode 303 and the voltage applied to the first electrode 202 can accelerate the adsorption of ionized gas groups.

[0026] The upper part of the upper housing 501 is connected to the microwave system fixing part 405 of a microwave generation and transmission system, and is connected in sequence to the analog conversion antenna 404, the three-screw impedance tuner 403, the circulator 402 and the microwave source 401. Microwave source 401 converts electrical energy into high-power microwave energy and uses circulator 402 to ensure that microwave signals can only be transmitted unidirectionally in a fixed, irreversible direction. Three-screw impedance tuner 403 further introduces capacitive or inductive parallel reactance by inserting three metal screws with adjustable depth in the waveguide to compensate for the impedance mismatch of the load. Finally, analog conversion antenna 404 is used to convert the mode generated by microwave source 401 into a specific mode suitable for directional radiation to achieve directional transmission.

[0027] The lower part of the lower housing 502 is also equipped with a microwave generation and transmission system of the same structure, and the two microwave generation and transmission systems are arranged opposite to each other.

[0028] Each microwave generation and transmission system includes a microwave system fixing unit 405, an analog conversion antenna 404, a three-screw impedance modulator 403, a circulator 402, and a microwave source 401 connected in sequence.

[0029] Except for the gas transmission channel 101 and the two opposing microwave generation and transmission systems, the rest of the structure is encapsulated by the upper housing 501 and the lower housing 502.

[0030] Example 2 This embodiment provides a method for depositing diamond films on cutting tools using the microwave plasma deposition apparatus described above, including the following steps: Clamping and Vacuum Preparation: Open the cover plate 203 on the top of the vacuum chamber housing 201, embed the WC-Co carbide tool to be coated into the tool holder 301, and close the cover plate 203 and lock it in place after clamping; evacuate the inside of the vacuum chamber housing 201 until the vacuum level inside the vacuum chamber housing 201 reaches 5×10⁻⁶. -3 Pa provides a low-pressure environment for subsequent plasma excitation.

[0031] Gas proportioning and delivery: According to the deposition process requirements, methane and hydrogen are introduced into the gas transmission channel 101 at a volume ratio of 1:15 through a high-precision mass flow controller; then, they are delivered to the inlet cavity 205 through the inlet base 102; after being buffered and guided by the fan-shaped gas channel 204, the mixed gas is evenly dispersed into the deposition cavity 206 through the second gas outlet 209, and at the same time, the mixed gas is also evenly dispersed into the deposition cavity 206 through the first gas outlet 208; the gas forms a stable and uniform low-pressure gas flow field in the cavity, and the gas partial pressure is maintained at 4 kPa.

[0032] Microwave excitation and plasma generation: The microwave generation and transmission systems on both sides of the upper shell 501 and the lower shell 502 are started simultaneously. The operating frequency of the microwave source 401 is set to 2.45 GHz and the output power is 1.2 kW. The microwave energy is transmitted unidirectionally through the circulator 402 to avoid reflected microwave damage to the microwave source 401. The impedance matching is then completed by the three-screw impedance tuner 403 to control the reflected power within 5% and improve the microwave energy utilization rate. Finally, the microwave energy is accurately introduced into the deposition cavity 206 by the analog conversion antenna 404. Under the action of microwave energy, the methane-hydrogen mixed gas in the cavity is rapidly ionized to form a high-density active plasma containing carbon free radicals, hydrogen free radicals and hydrocarbon groups. Among them, hydrogen free radicals can effectively inhibit the generation of graphite phase impurities and ensure the purity of the diamond coating.

[0033] Attitude control and directional deposition: The electrodes are activated, opening the first electrode 202 on the outside of the vacuum chamber shell 201 and the second electrode 303 of the tool clamping system, causing the voltage to cycle alternately between -30V and 30V for 30 seconds. Under positive voltage, the carbon-containing active groups in the plasma are guided to migrate and accumulate directionally towards the surface of the uncoated tool. Under negative voltage, the electrodes attract ionized hydrogen free radicals to collide with the tool surface, precisely etching the graphite phase and non-diamond phase impurities generated during the deposition process. At the same time, the four drive motors 211 at the bottom of the vacuum chamber shell are activated, driving the vacuum chamber shell 201 to rotate at a low speed of 5r / min. Simultaneously, the rotation controller 302 of the tool clamping system is activated, controlling the tool clamp 301 to rotate at a speed of 10r / min through the rotation motor and vibrator integrated in the rotation controller 302, supplemented by a micro-vibration with a frequency of 5Hz and an amplitude of 0.2mm, ensuring that the tool edge, sides, grooves and other complex parts can uniformly contact the active groups, achieving all-round uniform deposition.

[0034] Temperature control and deposition process: The temperature controller 210 is activated to stabilize the deposition environment temperature in the deposition cavity 206 at 950℃. The temperature inside the cavity is monitored in real time by the temperature sensor built into the temperature controller 210. When the temperature fluctuates, the temperature controller 210 automatically adjusts the heating power to control the temperature fluctuation range within ±5℃. Under the synergistic effect of a stable temperature field, a uniform plasma atmosphere and a directional adsorption electric field, active groups undergo an orderly crystallization and deposition reaction on the surface of the tool substrate.

[0035] Shutdown and Finished Product Removal: After 4 hours of continuous deposition, shut down the machine in the following order: first turn off the microwave source 401, then turn off the first electrode 202 and the second electrode 303, then turn off the drive motor 211, and finally turn off the gas source; after the cavity has cooled to room temperature naturally, open the vent valve of the vacuum cavity system to restore the pressure inside the cavity to atmospheric pressure; loosen the flange bolts of the cover plate 203, open the cover plate 203, and remove the tool to obtain the finished tool with a high-toughness diamond coating on the surface.

[0036] The uniformity of the diamond coating prepared by this invention is characterized from three core dimensions: thickness uniformity, phase composition uniformity, and microstructure and roughness uniformity. All characterizations select five typical feature points: the tool tip arc, the main cutting edge, the bottom surface of the chip flute, the outer cylindrical surface of the tool holder, and the center of the tool end face, covering all working areas and complex structures of the tool. The specific methods involved are as follows: Characterization of coating thickness uniformity: A combination of direct cross-sectional measurement and contact profilometer testing was used. The test tool was cut along the axial line, cold-mounted, and mechanically polished. The cross-sectional morphology of the coating was observed and the physical thickness was directly measured using a field emission scanning electron microscope. At the same time, the thickness of each characteristic site was tested using a contact profilometer. The average thickness, range, and relative standard deviation of each point of a single tool were statistically analyzed, as well as the thickness uniformity between pieces of the same batch of tools, to characterize the uniformity of the global distribution of coating thickness.

[0037] Characterization of coating fracture toughness: The Vickers indentation method was used as the core method, combined with the single-sided notched beam method for verification. For the Vickers indentation method, indentation tests were performed at various characteristic sites. The indentation and crack propagation morphology were photographed using a metallographic microscope. The diagonal length of the indentation and the crack propagation length were measured, and the fracture toughness KIC was calculated using the Anstis formula. For the single-sided notched beam method, sheet-like samples deposited using the same process were subjected to a three-point bending test according to the standard to calculate the fracture toughness and verify the consistency of the indentation test results. At the same time, the crack state around the indentation was used to characterize the coating's resistance to crack propagation. Coating microhardness characterization: Micro Vickers hardness tester was used for testing. Multi-point parallel indentation test was performed on each characteristic site of the coating. The test load and holding time were set according to the standard, and the test thickness met the rule of 10 times the indentation depth to avoid interference from the tool substrate on the hardness test results. The average hardness, range, and relative standard deviation of each point were statistically analyzed to characterize the global consistency and overall hardness level of the coating.

[0038] Characterization of microstructure and surface roughness uniformity: Field emission scanning electron microscopy and atomic force microscopy were used to photograph the surface morphology of each feature site, and the diamond grain size and density were statistically analyzed to observe whether there were defects such as pores, cracks, pinholes, and abnormal grain growth. Atomic force microscopy was used to select a fixed area scanning region at each feature site to test the surface roughness Ra value, and the dispersion of Ra values ​​between each point was statistically analyzed to characterize the global consistency of the coating microstructure and surface roughness.

[0039] Through testing, the microwave plasma deposition apparatus for diamond film deposition in cutting tools provided by this invention can effectively achieve diamond deposition films for cutting tools with the following parameters, wherein the corresponding characterization method data are the finished cutting tool data of the cutting tool in the embodiment of this invention: Coating thickness: 1-20μm; Corresponding characterization method: Using the aforementioned coating thickness uniformity characterization method, 5 parallel samples were selected from the same batch. For each sample, 5 characteristic points were selected: the tip arc, the main cutting edge, the bottom surface of the chip groove, the outer circular surface of the tool holder cylinder, and the center of the tool end face. 5 parallel data points were tested at each point, and the measured coating thickness was 8 μm.

[0040] In some embodiments, the coating thickness can be continuously and controllably adjusted within the range of 1 μm to 20 μm by adjusting the deposition time; the relative standard deviation of thickness between points of a single sample is ≤3.5%, the relative standard deviation of thickness between samples in the same batch is ≤4.0%, the coating thickness uniformity is excellent, and there are no local thick / thin defects.

[0041] Fracture toughness: 14.2 MPa m 1 / 2 -16.8MPa m 1 / 2 ; Corresponding characterization methods: The coating fracture toughness characterization method described above in this specification uses the Vickers indentation method with a load of 4.9 N (500 gf) and a holding time of 15 s; the single-sided notched beam method uses WC-Co substrate sheet specimens deposited using the same process, with a test span of 20 mm and a loading rate of 0.05 mm / min. The average fracture toughness obtained by the Vickers indentation method is 15.6 MPa. m 1 / 2 The deviation of the single-sided notched beam method verification test results was ≤4%, and the data consistency was good; only slight radial cracks appeared at the indentation sites of all samples, with no crack bifurcation or coating peeling, and the crack propagation resistance was significantly better than that of diamond coatings prepared by existing conventional MPCVD equipment (generally below 12MPa). m 1 / 2 This can achieve the beneficial effect of improving the fracture toughness of the coating as expected by the present invention.

[0042] Hardness: 80-96 GPa; Elastic modulus: 960-1050 GPa; In some embodiments, by controlling the deposition time, a correlation between deposition time and coating thickness can be achieved: Coating thickness 2μm (deposition 1h): microhardness 80GPa, elastic modulus 960GPa; Coating thickness 4μm (deposition 2h): microhardness 88GPa, elastic modulus 990GPa; Coating thickness 8μm (deposition 4h): microhardness 92.4GPa, elastic modulus 1020GPa; Coating thickness 12μm (deposition 6h): microhardness 94GPa, elastic modulus 1035GPa; Coating thickness 16-20μm (deposition 8-10h): microhardness 95-96GPa, elastic modulus 1040-1050GPa.

[0043] Corresponding characterization method: The coating microhardness characterization method (micro Vickers hardness test method) described above in this specification is used in conjunction with the nanoindentation method to simultaneously test the elastic modulus. A microhardness test load of 0.49 N (50 gf) is used, with a holding time of 15 s. The test thickness strictly adheres to the rule of 10 times the indentation depth. The nanoindentation method uses a Berkovich diamond indenter, with a maximum indentation depth not exceeding 1 / 10 of the coating thickness to avoid interference from the tool substrate on the test results. Using the coating microhardness characterization method, the average microhardness at each characteristic site of the coating is 92.4 GPa, with a relative standard deviation (RSD) ≤ 2.0%; the average elastic modulus is 1020 GPa, with a relative standard deviation (RSD) ≤ 1.8%. The consistency of hardness and elastic modulus across the entire range is excellent, and the performance is close to the intrinsic level of natural diamond.

[0044] Grain size: 0.05-10μm.

[0045] Corresponding characterization methods: The microstructure and surface roughness uniformity characterization methods described above in this specification are cross-validated using X-ray diffraction (XRD) and the Scherrer formula calculation method. SEM testing was used to select five characteristic sites: the tool tip arc, the main cutting edge, the bottom of the chip flute, the outer cylindrical surface of the tool holder, and the center of the tool end face. At least 200 grain sizes were statistically analyzed at each site. XRD testing used Cu target Kα rays, with a scanning range of 20° to 100°, and the grain size was calculated using the full width at half maximum (FWHM) of the diamond (111) crystal plane diffraction peaks. Verification results of this example (deposition time 4 hours, corresponding to a coating thickness of 8 μm): SEM statistics showed an average diamond grain size of 1.2 μm, while XRD Scherrer formula calculation yielded a grain size of 1.18 μm. The deviation between the two methods was ≤2%, indicating good data consistency. By adjusting the deposition process parameters (methane concentration, microwave power, deposition temperature), the diamond grain size can be precisely controlled within the range of 0.05 μm to 10 μm in some embodiments; the coatings prepared in all embodiments have regular grain morphology, no abnormal growth phenomenon, coating density ≥99.5%, and no structural defects such as pores and microcracks.

[0046] The high-toughness diamond-coated cutting tools prepared by this invention can be widely used in high-end manufacturing, precision machining, aerospace and other fields. They are suitable for cutting hard and brittle / difficult-to-machine materials such as carbon fiber reinforced resin matrix composites, hard-to-machine metals, and ceramics. Compared with diamond-coated cutting tools prepared by traditional MPCVD equipment, their cutting service life and machining accuracy are greatly improved, and the machining cost is significantly reduced, which promotes the development of high-end cutting tool manufacturing technology.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A microwave plasma deposition apparatus for diamond film deposition in cutting tools, comprising a housing, characterized in that, Also includes: Pneumatic control system, vacuum chamber system, tool clamping system, and microwave generation and transmission system; The gas path control system includes interconnected gas transmission channels (101) and air inlet base (102). The vacuum chamber system is located inside the outer shell; the vacuum chamber system includes a vacuum chamber housing (201), a temperature controller (210) and a first electrode (202); the vacuum chamber housing (201) is rotatably connected to the air inlet base (102), the first electrode is connected to the vacuum chamber housing (201), and the temperature controller is located inside the vacuum chamber housing (201); The vacuum chamber shell (201) includes an air passage (204), an air inlet cavity (205), a deposition cavity (206), a first air outlet (208), and a second air outlet (209); the air inlet cavity (205) is connected to the deposition cavity (206) through the first air outlet (208), and the air inlet cavity (205) is also connected to the deposition cavity (206) in sequence through the air passage (204) and the second air outlet (209); the air passage (204) is arranged around the deposition cavity (206); The tool clamping system is used to fix the tool to be processed and to drive the tool to be processed into the deposition cavity (206); The microwave generation and transmission system includes a microwave source (401), a circulator (402), a three-screw impedance tuner (403), an analog conversion antenna (404), and a microwave system fixing part (405) connected in sequence. The microwave generation and transmission system consists of two sets, with the microwave system fixing parts of the two sets of microwave generation and transmission systems fixed relative to each other at the reserved interface between the upper and lower parts of the outer shell. The tool clamping system includes a tool clamp (301), a rotation controller (302), and a second electrode (303). The tool holder (301) is located below the rotation controller (302), and the second electrode (303) is located on the transverse outer wall of the rotation controller (302). The rotation controller (302) integrates a rotation motor and a vibrator. The microwave plasma deposition apparatus further includes a drive motor (211), a first gear, and a second gear; the first gear is disposed at the output end of the drive motor (211), and the second gear is disposed on the outer wall of the vacuum chamber housing (201), and the first gear meshes with the second gear.

2. The microwave plasma deposition apparatus according to claim 1, characterized in that, The outer shell is formed by flange splicing of the upper shell (501) and the lower shell (502).

3. The microwave plasma deposition apparatus according to claim 1, characterized in that, The temperature controller (210) integrates a temperature sensor and a heater; A cover plate (203) is provided above the deposition cavity (206).

4. A method for depositing diamond films using the microwave plasma deposition apparatus described in any one of claims 1-3 as a cutting tool, characterized in that, Includes the following steps: S1. Open the cover plate (203), fix the tool to be deposited in the tool clamping system, and then close the cover plate (203) to seal; S2. Evacuate the vacuum chamber system and start the gas path control system to introduce CH4 and H2 into the vacuum chamber system; S3. Start the microwave generation and transmission system and energize the first electrode (202) and the second electrode (303). The voltage of the first electrode (202) and the second electrode (303) alternates between -30V and 30V. The period of the alternation is 10s-60s. S4. Start the drive motor (211) and rotation controller (302), start the temperature controller (210) to heat the vacuum chamber system, and perform the diamond film deposition.

5. The method according to claim 4, characterized in that, The vacuum level described in S2 reaches 5×10⁻⁶. -3 The volume ratio of CH4 to H2 in Pa;S2 is 1:

15.

6. The method according to claim 4, characterized in that, The gas pressure after CH4 and H2 are introduced in S2 is 4 kPa.

7. The method according to claim 4, characterized in that, The heating temperature described in S4 is 945-955℃.

8. The method according to claim 4, characterized in that, The deposition time described in S4 is 0.5h-10h.

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