CVD diamond thick film and preparation method and application thereof

Abstract

The invention discloses a CVD diamond thick film and a preparation method and application thereof. The thickness of the CVD diamond thick film is not less than 0.5 mm. The method comprises the following steps: (1) adopting a first growth process on a substrate to obtain an unmodified CVD diamond film; (2) carrying out modification treatment on the unmodified CVD diamond film obtained in the step (1) by adopting a second treatment process to obtain a modified CVD diamond film; (3) carrying out transition treatment on the modified CVD diamond film obtained in the step (2) by adopting a third transition process; and (4) the step (1) to the step (3) are cyclically operated, the cycle number is n, and the CVD diamond thick film is obtained. According to the method, through process control, the secondary nucleation process in the deposition process is achieved, the grain size is consistent in the long-time deposition process, no obvious columnar crystal exists on the diamond section, the good mechanical property is achieved, the thickness of the prepared CVD thick film reaches the millimeter level, and the hot wire carbon deposition phenomenon is remarkably relieved.

Description

Technical Field

[0001] The invention belongs to the technical field of CVD diamond thick films, and particularly relates to a high-performance CVD diamond thick film and a preparation method and application thereof. Background Art

[0002] Diamond has a series of excellent physical and chemical properties such as high hardness, high strength, good thermal conductivity, low thermal expansion coefficient, good optical and electrical properties, etc. It can be widely used in cutting tools, drill bits, ultra-high power semiconductor devices, infrared optical window materials and other fields, and has a wide range of application scenarios. Almost all the physical and chemical properties of diamonds prepared by Chemical Vapor Deposition (CVD) are the same as those of natural high-quality type IIa diamond single crystals (diamonds), which is the most promising process for artificial synthesis of diamonds. Among the many CVD synthetic diamond methods, the hot wire method (HF-CVD) is a commonly used method for synthesizing tool-grade CVD diamonds because of its simple process equipment, low cost, and large-area deposition.

[0003] Diamond synthesized by CVD can be divided into diamond thin film and diamond thick film according to thickness. Generally speaking, diamond thick film is defined as diamond film with a thickness of more than 0.5 mm. At present, diamond synthesized by CVD method is mainly thin film (with a thickness of μm level), and thick film is relatively rare. However, the application scenarios of diamond thick film in the market are far higher than that of thin film, especially in thick film tools, deep well drill bits, aerospace, high-power electronic device heat sinks, etc., which are far beyond the reach of CVD diamond thin film. However, the deposition rate of CVD diamond is low. When depositing millimeter-level thick films, the deposition time is usually hundreds of hours. The main difficulties in the preparation of CVD diamond thick film are: (1) The quality of the thick film is low. During the diamond deposition process, the preferential growth of crystals along a certain direction causes the crystals to gradually present a "V"-shaped columnar crystal with thin bottom and thick top. The existence of such columnar crystals leads to large internal stress in the diamond film, and the mechanical properties such as impact resistance, toughness, and wear resistance are reduced. As the deposition time increases, the columnar crystals grow significantly, and the quality and mechanical properties of the diamond thick film will further decline. (2) Filament quality deteriorates. During the hot-filament CVD deposition process, carbon deposition will inevitably occur on the filament, and the carbon deposition increases with the deposition time. When the carbon deposition on the filament is serious, it will affect the quality of the diamond film and even interrupt the deposition process.

[0004] CN201810306685.0 discloses a method for depositing a CVD diamond thick film. The method deposits a CVD diamond thick film on a metal molybdenum substrate, but the method only reaches the target deposition thickness by extending the time, and the obtained CVD diamond thick film contains a large number of columnar crystals, and the mechanical properties are seriously affected. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a CVD diamond thick film and a preparation method and application thereof. The CVD thick film of the present invention has a thickness of millimeters and good mechanical properties, and can be used as a cutting element using the method of the present invention. The method of the present invention realizes the "secondary nucleation" process in the deposition process through process control, achieves a consistent grain size during a long deposition process, and has no obvious columnar crystals on the diamond cross section. Through process control, the carbon deposition phenomenon of the hot wire is significantly slowed down, and long-term deposition is achieved.

[0006] A first aspect of the present invention provides a method for preparing a CVD diamond thick film, wherein the thickness of the CVD diamond thick film is not less than 0.5 mm, preferably not less than 1.0 mm, and further 1.0 mm to 2.0 mm, the method comprising:

[0007] (1) obtaining an unmodified CVD diamond film on a substrate by using a first growth process;

[0008] (2) then modifying the unmodified CVD diamond film obtained in step (1) using a second treatment process to obtain a modified CVD diamond film;

[0009] (3) then using a third transition process to perform transition treatment on the modified CVD diamond film obtained in step (2);

[0010] (4) Repeat steps (1) to (3) for n cycles to obtain the CVD diamond thick film.

[0011] In the above CVD diamond thick film preparation method, the first growth process is: respectively passing the first gas phase flow, the second gas phase flow and the third gas phase flow into the hot wire method CVD diamond growth furnace, setting the CVD diamond growth furnace parameters to the first growth process parameters, and running the first growth time.

[0012] In the above CVD diamond thick film preparation method, the first gas phase flow can be one or more of gaseous organic matter containing carbon elements and / or liquid organic matter containing carbon elements that are easily gasified, the second gas phase flow is hydrogen, and the third gas phase flow is argon. Specifically, the gaseous organic matter containing carbon elements can be one or more of methane, ethane, acetylene, propane, propylene, propyne, etc.; the liquid organic matter containing carbon elements that are easily gasified can be one or more of methanol, ethanol, acetone, and petroleum ether.

[0013] In the above-mentioned CVD diamond thick film preparation method, the volume flow ratio of the first gas phase flow, the second gas phase flow, and the third gas phase flow in the first growth process is controlled as follows: the third gas phase flow: (the second gas phase flow and the third gas phase flow) is 0.1 to 0.7, preferably 0.4 to 0.6; the first gas phase flow: (the first gas phase flow and the second gas phase flow) is 0.01 to 0.06, preferably 0.03 to 0.05.

[0014] In the above-mentioned CVD diamond thick film preparation method, the first growth process parameters are: the deposition furnace pressure is 3000~10000Pa, the single filament power is 0.5~0.9kW, the filament temperature is 2200~2700℃, the substrate temperature is 750~1050℃, and the distance between the filament and the substrate is 4~8mm; preferably, the deposition furnace pressure is 4000~9000Pa, the single filament power is 0.6~0.8kW, the single filament temperature is 2300~2600℃, and the substrate temperature is 800~950℃.

[0015] In the above CVD diamond thick film preparation method, the first growth time is 120 to 600 minutes, preferably 240 to 360 minutes.

[0016] In the above-mentioned CVD diamond thick film preparation method, the second treatment process is: stop the third gas phase flow, respectively pass the first gas phase flow and the second gas phase flow into the hot wire method CVD diamond growth furnace, set the CVD diamond growth furnace parameters to the second treatment process parameters, and run the second treatment time.

[0017] Furthermore, in the second treatment process, the volume flow ratio of the first gas phase flow and the second gas phase flow is controlled as follows: first gas phase flow: (first gas phase flow and second gas phase flow) is 0.04 to 0.08, preferably 0.05 to 0.06.

[0018] Furthermore, the second processing parameters are: the deposition furnace pressure is 2000-4000Pa, the single filament power is 0.7-1.0kW, the filament temperature is 2200-2700°C, the substrate temperature is 750-1050°C, and the distance between the filament and the substrate is 4-8mm; preferably, the deposition furnace pressure is 2500-3500Pa, the single filament power is 0.75-0.85kW, the single filament temperature is 2300-2600°C, and the substrate temperature is 800-950°C.

[0019] Furthermore, the second treatment duration is 10 to 60 minutes, preferably 20 to 30 minutes.

[0020] In the above-mentioned CVD diamond thick film preparation method, the third transition process is: introducing a third gas phase flow, respectively passing the first gas phase flow, the second gas phase flow, and the third gas phase flow into the hot wire method CVD diamond growth furnace, setting the CVD diamond growth furnace parameters to the third transition process parameters, and running the third transition time.

[0021] Furthermore, the third transition process parameters are: within the third transition time, the gas volume flow rate, deposition furnace pressure, single filament power, filament temperature, substrate temperature, and distance between the filament and the substrate linearly change from the second processing parameters to the first growth process parameters.

[0022] Furthermore, the third transition time is 20 to 120 minutes, preferably 30 to 60 minutes.

[0023] In the above CVD diamond thick film preparation method, the substrate can be selected as needed, and can be at least one of metal molybdenum, silicon, tungsten, titanium, graphite, etc. The shape of the substrate can be any shape, and the size of the substrate is not limited.

[0024] In the above CVD diamond thick film preparation method, the filament can be at least one of tantalum filament, tungsten filament, etc. The length and diameter of the filament are not limited and can be adapted to the size of the CVD deposition furnace and substrate used.

[0025] The second aspect of the present invention provides a CVD diamond thick film prepared by the above method.

[0026] Furthermore, the cross-sectional crystal size of the CVD diamond thick film is consistent.

[0027] Furthermore, the consistent size of the cross-sectional crystals means that there are no columnar crystals that are thin at the bottom and thick at the top, and the columnar crystal phenomenon of CVD diamond deposited for a long time is significantly improved.

[0028] Furthermore, the CVD diamond thick film is a micron polycrystalline structure. The crystals of the micron polycrystalline structure are one or more of a cubic morphology, an octahedral morphology, a truncated octahedral morphology and a more complex faceted morphology, or a chaotic non-preferentially oriented crystal composed of the above structures, preferably an octahedral morphology. The crystal size of the micron polycrystalline structure is between 10 and 100 μm.

[0029] Furthermore, the CVD diamond thick film crystals are tightly connected by DD bonds, and there are no obvious grain boundaries between the crystals.

[0030] Furthermore, Raman spectroscopy was used to characterize the SP 2 Characteristic peak intensity of hybrid graphite phase I G and SP 3 Characteristic peak intensity of hybrid diamond phase ID The ratio is I G / I D <0.2, preferably 1 G / I D <0.15.

[0031] According to a third aspect of the present invention, the CVD diamond thick film is used as a cutting element.

[0032] Furthermore, CVD diamond thick films can be used in the field of geological drilling for oil drilling, deep drilling and other conditions.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention realizes "secondary nucleation" during the growth process by periodically introducing the second treatment process and the third transition process, which can effectively block the formation of a columnar crystal structure with thin bottom and thick top due to the preferential rapid and long-term deposition of crystals in a certain direction in the traditional CVD diamond thick film deposition process. The columnar crystal phenomenon of CVD diamond deposition for a long time is significantly improved.

[0035] (2) The present invention introduces argon gas during the deposition process to increase the mean free path of methyl radicals, thereby increasing the effective methyl radical concentration, slowing down the carbon deposition phenomenon of the hot wire, effectively increasing the single growth time, and ensuring the thickness of the diamond film.

[0036] (3) The cross-sectional size of the crystals of the CVD diamond thick film provided by the present invention is uniform and consistent from top to bottom, and there are no columnar crystals that are thin at the bottom and thick at the top, thus avoiding the internal stress inside the crystal caused by such columnar crystal structure and improving the overall mechanical properties of the diamond film. The wear of the CVD diamond thick film provided by the method of the present invention can reach 600,000 to 900,000, which is 50% higher than that of conventional CVD diamond thick films.

[0037] (4) Compared with the PCD diamond commonly used in the field of geological exploration, the CVD diamond thick film provided by the present invention does not contain any metal binder and metal catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a cross-sectional scanning electron microscope image of the CVD diamond thick film of Example 1 of the present invention;

[0039] Figure 2 This is a surface scanning electron microscope image of the CVD diamond thick film of Example 1 of the present invention;

[0040] Figure 3 is a Raman spectrum of the CVD diamond thick film in Example 1 of the present invention;

[0041] Figure 4The carbon deposition of the filament in the CVD diamond furnace in Example 1 of the present invention after a cumulative deposition of 18000 min;

[0042] Figure 5 This is a cross-sectional scanning electron microscope image of the CVD diamond thick film in Comparative Example 1 of the present invention;

[0043] Figure 6 This is the carbon deposition condition of the filament in the CVD diamond furnace in comparative example 1 of the present invention after a cumulative deposition of 18000 min. DETAILED DESCRIPTION

[0044] The method of the present invention is further described in detail below by way of examples. The examples are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples.

[0045] The scanning electron microscope image of the present invention adopts Zeiss EVO MA15;

[0046] The Raman spectra of the present invention adopt LabRAM HR Evolution;

[0047] SP of the present invention 2 , SP 3 Hybridization was confirmed by Raman spectroscopy.

[0048] The present invention adopts the wear ratio to reflect the mechanical properties of the CVD diamond self-supporting film, and the test method is "JB / T-3235-1999"

[0049] Example 1

[0050] (1) Methane gas at a flow rate of 20 sccm, hydrogen gas at a flow rate of 500 sccm, and argon gas at a flow rate of 500 sccm were respectively introduced into the CVD diamond growth furnace, and the parameters of the CVD diamond growth furnace were set as follows: the deposition furnace pressure was 6000 Pa, the single filament power was 0.7 kW, the filament temperature was 2400°C, the substrate temperature was 850°C, the distance between the filament and the substrate was 6 mm, and the first growth time was 300 min.

[0051] (2) The argon gas flow rate was adjusted to 0 sccm, the methane gas flow rate was adjusted to 60 sccm, and the hydrogen gas flow rate was adjusted to 1000 sccm. The parameters of the CVD diamond growth furnace were adjusted as follows: the deposition furnace pressure was 3000 Pa, the single filament power was 0.8 kW, the filament temperature was 2350°C, the substrate temperature was 850°C, the distance between the filament and the substrate was 6 mm, and the second processing time was 25 min.

[0052] (3) After step (2) is completed, the third transition time is set to 35 minutes. Within 35 minutes, the parameters in step (2) including methane gas flow rate, hydrogen gas flow rate, argon gas flow rate, deposition furnace pressure, single filament power, filament temperature, substrate temperature, and the distance between the filament and the substrate are linearly changed to the parameters of step (1).

[0053] (4) Repeat steps (1) to (3) 70 times to obtain a CVD diamond thick film.

[0054] Example 2

[0055] (1) Methane gas at a flow rate of 18 sccm, hydrogen gas at a flow rate of 335 sccm, and argon gas at a flow rate of 500 sccm were respectively introduced into the CVD diamond growth furnace, and the parameters of the CVD diamond growth furnace were set as follows: the deposition furnace pressure was 9000 Pa, the single filament power was 0.8 kW, the filament temperature was 2600°C, the substrate temperature was 900°C, the distance between the filament and the substrate was 8 mm, and the first growth operation time was 360 min.

[0056] (2) The argon gas flow rate was adjusted to 0 sccm, the methane gas flow rate was adjusted to 64 sccm, and the hydrogen gas flow rate was adjusted to 1000 sccm. The parameters of the CVD diamond growth furnace were adjusted as follows: the deposition furnace pressure was 3500 Pa, the single filament power was 0.85 kW, the filament temperature was 2600°C, the substrate temperature was 950°C, the distance between the filament and the substrate was 4 mm, and the second processing time was 30 min.

[0057] (3) After step (2) is completed, the third transition time is set to 60 minutes. Within 60 minutes, the parameters in step (2) including methane gas flow rate, hydrogen gas flow rate, argon gas flow rate, deposition furnace pressure, single filament power, filament temperature, substrate temperature, and the distance between the filament and the substrate are linearly changed to the parameters of step (1).

[0058] (4) Repeat steps (1) to (3) 60 times to obtain a CVD diamond thick film.

[0059] Example 3

[0060] (1) Methane gas at a flow rate of 16 sccm, hydrogen gas at a flow rate of 800 sccm, and argon gas at a flow rate of 200 sccm were respectively introduced into the CVD diamond growth furnace, and the parameters of the CVD diamond growth furnace were set as follows: the deposition furnace pressure was 10000 Pa, the single filament power was 0.9 kW, the filament temperature was 2650°C, the substrate temperature was 1000°C, the distance between the filament and the substrate was 8 mm, and the first growth operation time was 120 min.

[0061] (2) The argon gas flow rate was adjusted to 0 sccm, the methane gas flow rate was adjusted to 60 sccm, and the hydrogen gas flow rate was adjusted to 1000 sccm. The parameters of the CVD diamond growth furnace were adjusted as follows: the deposition furnace pressure was 3000 Pa, the single filament power was 0.8 kW, the filament temperature was 2350°C, the substrate temperature was 850°C, the distance between the filament and the substrate was 6 mm, and the second processing time was 25 min.

[0062] (3) After step (2) is completed, the third transition time is set to 35 minutes. Within 35 minutes, the parameters in step (2), including methane gas flow rate, hydrogen gas flow rate, argon gas flow rate, deposition furnace pressure, single filament power, filament temperature, substrate temperature, and the distance between the filament and the substrate, are linearly changed to the parameters shown in step (1).

[0063] (4) Repeat steps (1) to (3) 120 times to obtain a CVD diamond thick film.

[0064] Example 4

[0065] (1) Methane gas at a flow rate of 20 sccm, hydrogen gas at a flow rate of 500 sccm, and argon gas at a flow rate of 500 sccm were respectively introduced into the CVD diamond growth furnace, and the parameters of the CVD diamond growth furnace were set as follows: the deposition furnace pressure was 6000 Pa, the single filament power was 0.7 kW, the filament temperature was 2400°C, the substrate temperature was 850°C, the distance between the filament and the substrate was 6 mm, and the first growth time was 300 min.

[0066] (2) The argon gas flow rate was adjusted to 0 sccm, the methane gas flow rate was adjusted to 32 sccm, and the hydrogen gas flow rate was adjusted to 750 sccm. The parameters of the CVD diamond growth furnace were adjusted as follows: the deposition furnace pressure was 2000 Pa, the single filament power was 1.0 kW, the filament temperature was 2700°C, the substrate temperature was 1050°C, the distance between the filament and the substrate was 4 mm, and the second processing time was 10 min.

[0067] (3) After step (2) is completed, the third transition time is set to 35 minutes. Within 35 minutes, the parameters in step (2) including ethane gas flow rate, hydrogen gas flow rate, argon gas flow rate, deposition furnace pressure, single filament power, filament temperature, substrate temperature, and the distance between the filament and the substrate are linearly changed to the parameters of step (1).

[0068] (4) Repeat steps (1) to (3) 70 times to obtain a CVD diamond thick film.

[0069] Comparative Example 1

[0070] (1) Methane gas at a flow rate of 20 sccm and hydrogen gas at a flow rate of 1000 sccm were respectively introduced into the CVD diamond growth furnace, and the parameters of the CVD diamond growth furnace were set as follows: the deposition furnace pressure was 6000 Pa, the single filament power was 0.7 kW, the filament temperature was 2400°C, the substrate temperature was 850°C, the distance between the filament and the substrate was 6 mm, and the first growth time was 300 min.

[0071] (2) Adjust the methane gas flow rate to 60 sccm and the hydrogen gas flow rate to 1000 sccm. Adjust the CVD diamond growth furnace parameters as follows: the deposition furnace pressure is 3000 Pa, the single filament power is 0.8 kW, the filament temperature is 2350°C, the substrate temperature is 850°C, the distance between the filament and the substrate is 6 mm, and the second processing time is 25 min.

[0072] (3) After step (2) is completed, the third transition time is set to 35 minutes. Within 35 minutes, the parameters in step (2) including methane gas flow, hydrogen gas flow, argon gas flow, deposition furnace pressure, single filament power, filament temperature, substrate temperature, and the distance between the filament and the substrate are linearly changed to the parameters of step (1).

[0073] (4) Repeat steps (1) to (3) 70 times to obtain a CVD diamond thick film.

[0074] Comparative Example 2

[0075] (1) Methane gas at a flow rate of 20 sccm, hydrogen gas at a flow rate of 500 sccm, and argon gas at a flow rate of 500 sccm were respectively introduced into a CVD diamond growth furnace, and the parameters of the CVD diamond growth furnace were set as follows: the deposition furnace pressure was 6000 Pa, the single filament power was 0.7 kW, the filament temperature was 2400°C, the substrate temperature was 850°C, the distance between the filament and the substrate was 6 mm, and the first growth time was 24000 min to obtain a CVD diamond thick film.

[0076] Comparative Example 3

[0077] (1) Methane gas at a flow rate of 20 sccm, hydrogen gas at a flow rate of 500 sccm, and argon gas at a flow rate of 500 sccm were respectively introduced into the CVD diamond growth furnace, and the parameters of the CVD diamond growth furnace were set as follows: the deposition furnace pressure was 6000 Pa, the single filament power was 0.7 kW, the filament temperature was 2400°C, the substrate temperature was 850°C, the distance between the filament and the substrate was 6 mm, and the first growth time was 300 min.

[0078] (2) The argon gas flow rate was adjusted to 0 sccm, the methane gas flow rate was adjusted to 60 sccm, and the hydrogen gas flow rate was adjusted to 1000 sccm. The parameters of the CVD diamond growth furnace were adjusted as follows: the deposition furnace pressure was 3000 Pa, the single filament power was 0.8 kW, the filament temperature was 2350°C, the substrate temperature was 850°C, the distance between the filament and the substrate was 6 mm, and the second processing time was 25 min.

[0079] (3) Cycle the steps (1) to (2) for 70 cycles to obtain a CVD diamond thick film

[0080] Application Example 1

[0081] The CVD diamond thick films obtained in Examples 1-4 and Comparative Examples 1-3 were subjected to abrasion ratio tests. The abrasion ratio test conditions were as follows: the samples were uniformly laser cut to Double-sided grinding and polishing were performed. The core-forming surface was used as the working surface, the grinding wheel hardness was 3.7, the initial test speed was 25 m / s, and the rest of the test conditions and steps were carried out in accordance with JB / T-3235-1999.

[0082] Table 1 Test results of CVD diamond films of various embodiments and comparative examples

[0083]

[0084]

[0085] pass Figure 1 and Figure 5 By comparison, it can be seen that the CVD diamond thick film prepared by the method of the present invention is dense, has few defects, has a regular cross-sectional crystal structure, and the growth of columnar crystals is effectively suppressed. Figure 4 and Figure 5 It can be seen from the comparison that the method of the present invention effectively suppresses the carbon deposition in the two sections of the filament during the preparation of the CVD diamond thick film, thereby ensuring the stability of the filament deposited for a long time.

[0086] The above describes the specific implementation of the present invention in detail, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the various technical features being combined in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing a CVD diamond thick film, wherein the thickness of the CVD diamond thick film is not less than 0.5 mm, preferably not less than 1.0 mm, and further 1.0 mm to 2.0 mm, the method comprising: (1) obtaining an unmodified CVD diamond film on a substrate by using a first growth process; (2) then modifying the unmodified CVD diamond film obtained in step (1) using a second treatment process to obtain a modified CVD diamond film; (3) then using a third transition process to perform transition treatment on the modified CVD diamond film obtained in step (2); (4) Repeat steps (1) to (3) for n cycles to obtain the CVD diamond thick film.

2. The preparation method according to claim 1, characterized in that: The first growth process is: respectively passing the first gas phase flow, the second gas phase flow and the third gas phase flow into the hot wire method CVD diamond growth furnace, setting the CVD diamond growth furnace parameters to the first growth process parameters, and running the first growth time.

3. The preparation method according to claim 2, characterized in that: The first gas phase flow is one or more of gaseous organic matter containing carbon elements and / or liquid organic matter containing carbon elements that is easily gasified, the second gas phase flow is hydrogen, and the third gas phase flow is argon.

4. The preparation method according to claim 2, characterized in that: In the first growth process, the volume flow ratio of the first gas phase flow, the second gas phase flow, and the third gas phase flow is controlled as follows: the third gas phase flow: (the second gas phase flow and the third gas phase flow) is 0.1 to 0.7, preferably 0.4 to 0.6; the first gas phase flow: (the first gas phase flow and the second gas phase flow) is 0.01 to 0.06, preferably 0.03 to 0.

05.

5. The preparation method according to claim 2, characterized in that: The first growth process parameters are: the deposition furnace pressure is 3000-10000Pa, the single filament power is 0.5-0.9kW, the filament temperature is 2200-2700°C, the substrate temperature is 750-1050°C, and the distance between the filament and the substrate is 4-8mm; preferably, the deposition furnace pressure is 4000-9000Pa, the single filament power is 0.6-0.8kW, the single filament temperature is 2300-2600°C, and the substrate temperature is 800-950°C.

6. The preparation method according to claim 2, characterized in that: The first growth time is 120 to 600 minutes, preferably 240 to 360 minutes.

7. The preparation method according to claim 1, characterized in that: The second treatment process is: stop the third gas phase flow, respectively introduce the first gas phase flow and the second gas phase flow into the hot wire method CVD diamond growth furnace, set the CVD diamond growth furnace parameters to the second treatment process parameters, and run the second treatment time.

8. The preparation method according to claim 7, characterized in that: In the second treatment process, the volume flow ratio of the first gas phase flow and the second gas phase flow is controlled as follows: first gas phase flow: (first gas phase flow and second gas phase flow) is 0.04 to 0.08, preferably 0.05 to 0.

06.

9. The preparation method according to claim 7, characterized in that: The second processing parameters are: the deposition furnace pressure is 2000-4000Pa, the single filament power is 0.7-1.0kW, the filament temperature is 2200-2700°C, the substrate temperature is 750-1050°C, and the distance between the filament and the substrate is 4-8mm; preferably, the deposition furnace pressure is 2500-3500Pa, the single filament power is 0.75-0.85kW, the single filament temperature is 2300-2600°C, and the substrate temperature is 800-950°C.

10. The preparation method according to claim 7, characterized in that: The second treatment duration is 10 to 60 minutes, preferably 20 to 30 minutes.

11. The preparation method according to claim 1, characterized in that: The third transition process is: introducing a third gas phase flow, respectively passing the first gas phase flow, the second gas phase flow, and the third gas phase flow into the hot wire method CVD diamond growth furnace, setting the CVD diamond growth furnace parameters to the third transition process parameters, and running the third transition time.

12. The preparation method according to claim 11, characterized in that: The third transition process parameters are: within the third transition time, the gas volume flow rate, deposition furnace pressure, single filament power, filament temperature, substrate temperature, and the distance between the filament and the substrate linearly change from the second processing parameters to the first growth process parameters.

13. The preparation method according to claim 11, characterized in that: The third transition time is 20 to 120 minutes, preferably 30 to 60 minutes.

14. A CVD diamond thick film prepared by the preparation method according to any one of claims 1 to 13.

15. The CVD diamond thick film according to claim 14, characterized in that The cross-sectional crystal size of the CVD diamond thick film is consistent.

16. The CVD diamond thick film according to claim 14, characterized in that The CVD diamond thick film is a micron polycrystalline structure, and the crystal size of the micron polycrystalline structure is between 10 and 100 μm.

17. The CVD diamond thick film according to claim 14, characterized in that Characterized by Raman spectroscopy, SP 2 Characteristic peak intensity of hybrid graphite phase I G and SP 3 Characteristic peak intensity of hybrid diamond phase I D The ratio is I G / I D <0.2, preferably 1 G / I D <0.

15.

18. Application of the CVD diamond thick film prepared by the preparation method according to any one of claims 1 to 13 in cutting elements.

Images