CN112695293A

CN112695293A - Method for depositing polycrystalline diamond compact with CVD diamond coating at low temperature

Info

Publication number: CN112695293A
Application number: CN202011504051.XA
Authority: CN
Inventors: 简小刚; 胡吉博; 彭薪颖; 杨天
Original assignee: Tongji University
Current assignee: Tongji University
Priority date: 2020-12-17
Filing date: 2020-12-17
Publication date: 2021-04-23

Abstract

The invention relates to a method for depositing a polycrystalline diamond compact with a CVD diamond coating at low temperature, which comprises the following steps: (1) preparing a polycrystalline diamond compact substrate; (2) vacuumizing a reaction chamber of the chemical vapor deposition device, introducing mixed gas consisting of hydrogen and methane, and carrying out nucleation treatment; (3) putting the polycrystalline diamond compact substrate into a reaction chamber, introducing a mixed gas consisting of hydrogen, methane and carbon dioxide, and performing chemical vapor deposition; (4) and after the deposition is finished, closing methane and carbon dioxide, keeping the hydrogen flow unchanged, and carrying out etching treatment to obtain the polycrystalline diamond compact deposited with the CVD diamond coating at the low temperature. Compared with the prior art, the method can avoid the failure of the polycrystalline diamond compact caused by the graphitization promotion effect of the catalyst under the high-temperature and high-pressure condition and the difference of the high-temperature thermal expansion coefficients, thereby prolonging the service life of the polycrystalline diamond compact, reducing the drilling change frequency and the like.

Description

Method for depositing polycrystalline diamond compact with CVD diamond coating at low temperature

Technical Field

The invention belongs to the technical field of material coatings, and relates to a method for depositing a polycrystalline diamond compact of a CVD diamond coating at a low temperature.

Background

The diamond coating is a novel functional material in the 21 st century, has high strength, high frictional wear performance, high thermal conductivity and chemical stability, and has wide application prospect. Currently, the well-known Deposition method of diamond coating is mainly Chemical Vapor Deposition (CVD), but the main problem limiting the industrial development of diamond coating technology is insufficient toughness of the coating, which leads to easy peeling off of the coating and the substrate.

Diamond wear of diamond drills can be classified into brittle fracture, abrasive wear, thermal wear, and threshing. Firstly, the bonding metal in the matrix is worn because the hardness and the wear resistance of the bonding metal are much lower than those of the framework material, and simultaneously, the bonding metal is easily worn by rock particles. The abrasion of the bonding metal further causes the falling-off of the framework material and the diamond, and further grinds the matrix, so that the matrix is further abraded, and the failure of the diamond drill bit is caused.

Polycrystalline diamond has various formulas and uses, and the selection of a proper substrate formula to obtain good substrate + diamond coating film-substrate bonding strength is a key problem to be solved. The U.S. Pat. No. 4, 4211294A,897,897,89 bit matrix is composed of titanium carbide, nickel-manganese alloy and iron powder, wherein the tungsten carbide content is about 10-50%, the nickel-manganese alloy content is about 15-50% (wherein the nickel content is about 50-60%, the manganese content is 40-50%) and the iron powder content is about 20-50% by weight. The drill bit adopts diamond with the granularity of 40-50 meshes and the matrix grade of HRC 10-20. Patent CN110056313A proposes that diamond micro powder 80-89 wt%, cobalt 10-15 wt%, silicon 1-5 wt% and diamond-impregnated layer in polycrystalline diamond layer are sintered at 20-30 MPa, 700-1000 ℃ or 0.2-0.6 GPa, 700-1000 ℃. In summary, there are currently existing diamond drill bits that have improved performance, but that have not yet met the desired needs.

Meanwhile, with the rapid development of the technology of CVD deposition of the diamond coating, the performance of the diamond coating is gradually excellent, but most of researches on the preparation of the diamond coating require that the substrate temperature is higher than 700 ℃, for example, the deposition temperature of a workpiece in a patent CN201410068775 is 820-880 ℃, the deposition temperature of a patent CN201410465657 is 850-900 ℃, the deposition temperature of a patent CN105349965B is 700-900 ℃, and the like, and the deposition temperature is still higher. This undoubtedly increases the process difficulty of CVD deposition of diamond coatings.

Generally speaking, because the diamond bit works under the abominable operating mode, the service life of the bit is gradually reduced, and because the replacement cost of the bit is higher, the current polycrystalline diamond composite bit needs to be researched and optimized and guidance can be provided for subsequent industrialized popularization.

Disclosure of Invention

The invention aims to provide a method for depositing a polycrystalline diamond compact with a CVD diamond coating at a low temperature.

The invention changes the proportion of each element in the formula of the substrate of the polycrystalline diamond compact, thereby improving the film-substrate binding force between the diamond coating and the polycrystalline diamond compact, improving the working efficiency and the service life of the polycrystalline diamond compact drill bit, reducing the replacement frequency and achieving better economic benefit.

The purpose of the invention can be realized by the following technical scheme:

a method of low temperature deposition of a CVD diamond coated polycrystalline diamond compact, comprising the steps of:

(1) preparing a polycrystalline diamond compact substrate;

(2) vacuumizing a reaction chamber of the chemical vapor deposition device, introducing mixed gas consisting of hydrogen and methane, and carrying out nucleation treatment;

(3) putting the polycrystalline diamond compact substrate into a reaction chamber, introducing a mixed gas consisting of hydrogen, methane and carbon dioxide, and performing chemical vapor deposition;

(4) and after the deposition is finished, closing methane and carbon dioxide, keeping the hydrogen flow unchanged, and carrying out etching treatment to obtain the polycrystalline diamond compact deposited with the CVD diamond coating at the low temperature.

Further, in step (1), the polycrystalline diamond compact substrate is prepared by the following method:

mixing diamond micro powder and metal alloy, wherein the diamond micro powder is formed by mixing particles with the particle size of 25-30 meshes and particles with the particle size of 40-50 meshes according to the mass ratio of 1: 1; the metal alloy comprises the following components: 54-58 wt% of WC, 3-7 wt% of Co, 28-34 wt% of Cu and 5-15 wt% of Sn, and sintering at high temperature and high pressure by adopting a powder metallurgy method to obtain the polycrystalline diamond compact substrate.

Furthermore, the mass ratio of the diamond micro powder to the metal alloy is 4: 1.

Furthermore, the sintering process specifically comprises: sintering at the temperature of 1000-1200 ℃ under the condition of 5GPa, keeping the temperature for 5-15min, cooling to 800 ℃, discharging, and cooling to room temperature.

Furthermore, the diamond micro powder has one or more of nano-crystal, submicron crystal, micron crystal, fine crystal or coarse crystal in particle size.

Further, in the step (2), the volume ratio of hydrogen to methane is 49: 1;

in the nucleation treatment process, the air pressure in the reaction cavity is 5kPa, the microwave frequency is 2.45GHz, the power of the microwave source is set to be 1kW, then the reactor is started, and the nucleation time is 30 min.

Further, in the step (3), the flow ratio of the hydrogen, the methane and the carbon dioxide is 200: (5-7): (4-6).

Further, in the step (3), during the deposition process: the deposition pressure is 6-9 kPa, the microwave power is 600-900W, the deposition temperature is 500-700 ℃ and the deposition time is 6-10 h.

Further, in the step (4), the process conditions of the etching process are specifically as follows: the pressure is 9-15 kPa, the microwave power is 600-1000W, the etching temperature is 700-900 ℃, and the time is 5-15 min.

Further, the CVD diamond coating is deposited to a thickness of not less than 0.01 mm.

The polycrystalline diamond compact is prepared by loading a hard alloy matrix and diamond micro powder into a metal cup and sintering at high temperature and high pressure under the condition of a metal catalyst. The diamond content is typically about 70% to 90% by weight, and the binder content is typically low. The diamond micro powder has strong hardness, wear resistance and good performance, the binder phase has good toughness, and the diamond particles, WC, Co, Cu and Sn determine the strength, toughness, wear resistance and other performances of the matrix. Under a proper sintering temperature, copper with low cauterization points is used as bonding metal, Cu can be melted by alloy, the matrix is impregnated through infiltration, Cu and Sn and Cu and Co are mutually diffused, the binding force between the matrixes is improved, and the holding force of the matrixes to diamond is improved; the WC with high cauterization points can form hard particles of the matrix in the matrix, so that the hardness and the wear resistance of the matrix are increased, and meanwhile, the WC in a solid phase is kept during high overflow so that diamond does not move in a dislocation way; tungsten carbide is selected for its good forming properties at high temperatures, minimal erosion to diamond, and good wetting to a variety of metals. The cobalt mainly has the effects of improving the machinability of the matrix, and components such as Co in the hard alloy permeate to diamond under high temperature and high pressure and promote the bonding and adhesion of diamond particles; fusible metals such as Sn work the same as Cu, but with different efficiencies. Manganese, cobalt, nickel and chromium all play a role in improving and strengthening the performance of the tire body in the tire body. The components and content of the binder phase have great influence on the performance of the polycrystalline diamond compact, and the polycrystalline diamond compact containing the metal binder phase generally has poor thermal stability but good impact toughness.

The Co metal element only endures the temperature below 700 ℃ under normal pressure, the temperature above 700 ℃ promotes the transformation of diamond to graphite, and graphitization preferentially occurs at the interfaces between diamond particles. Graphite can block bonding among diamond particles; the volume increase caused by the graphitization of the diamond phase and the high-temperature thermal expansion coefficient of metals such as Co and the like are far larger than that of diamond, so that cracks are easily generated, and the strength and hardness of the diamond are greatly reduced. The composition and content of Co need to be defined. Because the difference between the thermal expansion coefficient of cobalt and diamond is large, microcracks are easily formed between diamond and metal cobalt in the actual drilling process, and the composite sheet is thermally failed; on the other hand, the temperature condition of the composite sheet also needs to be specially limited because the graphitization of diamond is promoted under the high temperature condition and the service life of the composite sheet is shortened. In addition, the polycrystalline diamond compact contains metal tungsten, but excessive tungsten also reduces the wear resistance of the polycrystalline diamond compact. In addition, the content of cobalt is not too high, so that the problem of poor permeability of metal cobalt in the diamond micro powder is avoided.

When the diamond coating is prepared, chlorine element, oxygen element and the like are introduced, so that the preparation of the coating with better surface quality under the low-temperature condition is facilitated, and the film-substrate binding force of the coating is improved. The H plasma etches graphite and also etches diamond, but the graphite etching speed is far higher than that of etching diamond, so that the diamond coating with better surface appearance is indirectly obtained.

Compared with the prior art, the invention has the following advantages:

(1) the formula of the polycrystalline diamond compact is adjusted, and the polycrystalline diamond compact with compact particles and good performance is sintered;

(2) the invention is to improve the polycrystalline diamond substrate by adding oxygen-containing CO source₂Optimizing the deposition process, realizing the effect of depositing the CVD diamond coating at low temperature, and avoiding the influence on the bonding performance of the polycrystalline diamond compact due to the graphitization effect and the difference of the thermal expansion coefficient of the catalyst at higher temperature;

(3) the method is simple, the operation is easy to realize, the method can be popularized and applied to the fields of numerical control machine tools, drawing dies, geological drills and the like, and the low-temperature deposition process can be continuously explored subsequently to expand the method to the fields of electronic devices such as semiconductors, heat transfer, heat dissipation and the like.

Drawings

Fig. 1 is a surface topography of a polycrystalline diamond compact of the improved substrate formulation of the present invention;

FIG. 2-1 is a 2000-fold scanning electron micrograph of a CVD diamond film according to the present invention at a substrate deposition temperature of 500 ℃;

FIG. 2-2 is a Raman diagram of a CVD diamond film at a substrate deposition temperature of 500 ℃ in the present invention;

FIG. 3-1 is a view of a CVD diamond film at a deposition temperature of 600 ℃ according to the present invention, as observed by a scanning electron microscope of 2000 times;

FIG. 3-2 is a Raman diagram of a CVD diamond film at a substrate deposition temperature of 600 ℃ in the present invention;

FIG. 4-1 is a view of a CVD diamond film at a deposition temperature of 700 ℃ according to the present invention, as observed by a scanning electron microscope of 2000 times;

FIG. 4-2 is a Raman diagram of a CVD diamond film at a substrate deposition temperature of 700 ℃ in the present invention;

fig. 5 is a graph showing the indentation test results of the CVD diamond film at a deposition temperature of 500 c, 600 c, and 700 c for the polycrystalline diamond compact of the present invention.

FIG. 6 is a 2000-fold scanning electron microscope observation image of the CVD diamond film obtained in comparative example 1;

FIG. 7 is a 2000-fold scanning electron microscopic view of the CVD diamond film obtained in comparative example 2;

FIG. 8 is a 2000-fold scanning electron microscopic observation image of the CVD diamond films obtained in comparative examples 3 to 5.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

In the following examples, CVD diamond coatings were prepared using a Korea Woostonent-R2.0 model MultiFunctional Microwave Plasma (MPCVD) apparatus (2kW,2.45 GHz). Otherwise, unless otherwise specified, all the conventional commercial raw materials or conventional processing techniques are used in the art.

Example 1:

a method for low temperature deposition of a CVD diamond coating on a polycrystalline diamond compact based on an improved substrate formulation, comprising the steps of:

(1) improved polycrystalline diamond compact substrate formulation

Changing the formula of the polycrystalline diamond compact substrate, wherein the ratio of the diamond micro powder to the metal alloy is 4:1 in parts by mass, wherein the ratio of the diamond micro powder to the metal alloy is as follows: 25/30 mesh (25-30 mesh, the same below) and 40/50 mesh (40-50 mesh), wherein 25/30:40/50 is 1:1 (mass ratio, the same below); the metal alloy contains 50 wt% of WC, 7 wt% of Co, 28 wt% of Cu and 15 wt% of Sn. And directly placing the polycrystalline diamond powder and the hard alloy powder into a die, sintering at the temperature of 1200 ℃ under the condition of 5GPa by adopting a powder metallurgy method, keeping the temperature for 15min, cooling to 800 ℃, discharging, and air cooling to room temperature.

(2) CVD diamond coating deposition

The first step is as follows: nucleation stage

Vacuumizing to below 1Pa, forming a mixed gas by 98% of hydrogen and 2% of methane, adjusting the air pressure to 5kPa, setting the microwave frequency to 2.45GHz, setting the power of a microwave source to 1kW, starting, generating plasma in a reaction chamber, and nucleating for 30 min.

The second step is that: CVD diamond coating deposition

Putting the naturally air-dried substrate into a chemical vapor deposition device, and introducing H₂、CH₄、CO₂The mixed gas is used for carrying out chemical vapor deposition experiments. H₂The content is 200sccm, CH₄Content 6sccm, CO₂The content is 6sccm, and the deposition process parameters are as follows: the deposition pressure is 8kPa, the microwave power is 800W, the deposition temperature of the substrate can reach 500 ℃ measured by an infrared thermometer, and the deposition lasts for 8 hours.

The third step: etching of hydrogen plasma

Close CH₄、CO₂Gas, hold H₂The flow is unchanged, the temperature and the pressure of the substrate are adjusted, etching is carried out, and the etching parameters are as follows: the deposition pressure is 11kPa, the microwave power is 800W, the deposition temperature of the substrate can reach 800 ℃ measured by an infrared thermometer, and the etching is carried out for 5 min. And after the etching is finished, shutting down the machine and taking out the substrate.

Example 2

(1) improved polycrystalline diamond compact substrate formulation

Changing the formula of the polycrystalline diamond compact substrate, wherein the ratio of the diamond micro powder to the metal alloy is 4:1 in parts by mass, wherein the ratio of the diamond micro powder to the metal alloy is as follows: 25/30 mesh (25-30 mesh, the same below) and 40/50 mesh (40-50 mesh), wherein 25/30:40/50 is 1:1 (mass ratio, the same below); the metal alloy contained 54 wt% of WC, 6 wt% of Co, 30 wt% of Cu and 10 wt% of Sn. And directly placing the polycrystalline diamond powder and the hard alloy powder into a die, sintering at the temperature of 1100 ℃ under the condition of 5GPa by adopting a powder metallurgy method, keeping the temperature for 10min, cooling to 800 ℃, discharging, and air cooling to room temperature.

(2) CVD diamond coating deposition

The first step is as follows: nucleation stage

The second step is that: CVD diamond coating deposition

Putting the naturally air-dried substrate into a chemical vapor deposition device, and introducing H₂、CH₄、CO₂The mixed gas is used for carrying out chemical vapor deposition experiments. H₂The content is 200sccm, CH₄Content 7sccm, CO₂The content is 4sccm, the deposition process parameters are that the deposition air pressure is 9kPa, the microwave power is 850W, the deposition temperature of the substrate can be measured by an infrared thermometer and can reach 600 ℃, and the deposition is carried out for 8 hours.

The third step: etching of hydrogen plasma

Close CH₄、CO₂Gas, hold H₂And (3) adjusting the temperature and the pressure of the substrate to etch the substrate without changing the flow, wherein the etching parameters are that the deposition pressure is 13kPa, the microwave power is 830W, the deposition temperature of the substrate can be measured by an infrared thermometer to reach 830 ℃, and the etching is carried out for 10 min. And after the etching is finished, shutting down the machine and taking out the substrate.

Example 3

(1) improved polycrystalline diamond compact substrate formulation

Changing the formula of the polycrystalline diamond compact substrate, wherein the ratio of the diamond micro powder to the metal alloy is 4:1 in parts by mass, wherein the ratio of the diamond micro powder to the metal alloy is as follows: 25/30 mesh (25-30 mesh, the same below) and 40/50 mesh (40-50 mesh), wherein 25/30:40/50 is 1:1 (mass ratio, the same below); the metal alloy contained WC in an amount of 58 wt%, Co in an amount of 3 wt%, Cu in an amount of 34 wt%, and Sn in an amount of 5 wt%. And directly placing the polycrystalline diamond powder and the hard alloy powder into a die, sintering at the temperature of 1000 ℃ under the condition of 5GPa by adopting a powder metallurgy method, keeping the temperature for 5min, cooling to 800 ℃, discharging, and air cooling to room temperature.

(2) CVD diamond coating deposition

The first step is as follows: nucleation stage

The second step is that: CVD diamond coating deposition

Putting the naturally air-dried substrate into a chemical vapor deposition device, and introducing H₂、CH₄、CO₂The mixed gas is used for carrying out chemical vapor deposition experiments. H₂The content is 200sccm, CH₄Content 5sccm, CO₂The content is 5sccm, the deposition process parameters are that the deposition air pressure is 7kPa, the microwave power is 900W, the deposition temperature of the substrate can reach 700 ℃ by using an infrared thermometer, and the deposition is carried out for 8 hours.

The third step: etching of hydrogen plasma

Close CH₄、CO₂Gas, hold H₂And (3) adjusting the temperature and the pressure of the substrate to perform etching with the flow unchanged, wherein the etching parameters are that the deposition pressure is 15kPa, the microwave power is 900W, the deposition temperature of the substrate can be measured by an infrared thermometer to reach 850 ℃, and the etching is performed for 15 min. And after the etching is finished, shutting down the machine and taking out the substrate.

The surface topography of the polycrystalline diamond compact with the improved substrate formulation prepared in example 1 above is shown in fig. 1.

FIG. 2 is a graph showing a deposition temperature of 5 ℃ for the substrate obtained in example 1The SEM image and the Raman image of the CVD diamond film at 00 ℃ of 2000 times can show that the grains of the diamond film are clear, but more fine grains exist, which indicates that a large amount of secondary nucleation exists at a lower temperature, from the SEM image of the image 2-1. From the Raman graph of FIGS. 2-2, it can be seen that the diamond peak is 1336.51cm^-1There is a large residual compressive stress.

FIG. 3 is a scanning electron micrograph and a Raman micrograph of the CVD diamond film of 2000 times at a deposition temperature of 600 ℃ obtained in example 2, and it can be seen from the SEM of FIG. 3-1 that the grains of the diamond film are clear and the number of fine grains is not so large, which shows that the secondary nucleation phenomenon is alleviated at a lower temperature. From the Raman graph of FIG. 3-2, it can be seen that the diamond peak is 1334.92cm^-1The residual compressive stress also becomes small.

FIG. 4 is a 2000-fold scanning electron micrograph and a Raman micrograph of a CVD diamond film at a deposition temperature of 700 ℃ on the substrate obtained in example 3, as shown in FIG. 4. It can be seen from the SEM of FIG. 4-1 that the grains of the diamond film are clear and relatively uniform. From the Raman graph of FIG. 4-2, it can be seen that the diamond peak is 1333.33cm^-1The residual compressive stress is minimal.

The polycrystalline diamond compacts prepared in examples 1 to 3 were deposited at 500 ℃, 600 ℃, and 700 ℃ as shown in fig. 5, which shows the indentation test results of the CVD diamond thin film. The test result shows that the bonding strength of the film and the substrate is increased along with the temperature, the cracks are gradually reduced, the general rule is met, the indentation cracks are uniform, and the film-substrate bonding strength is good.

Comparative example 1:

compared with the embodiment 1, most of the components are the same, except that the carbon dioxide component is omitted from the mixed gas in the chemical vapor deposition process, namely, only the hydrogen and the methane with the same content are introduced. FIG. 6 shows that CO is not introduced₂SEM topography of diamond coating. Under the condition of low temperature, the temperature is lower and the energy in the reaction system is insufficient, so that more graphite phases are deposited, and the integral surface appearance is poorer. Indicating the introduction of CO₂The gas is beneficial to preparing the diamond coating with better surface appearance under the condition of low temperature. The test was carried out using a 150kg Rockwell indentation with the addition of CO at 500 deg.C₂Is marked withCompared with the appearance, the crack is larger, and the crack has radial and tangential cracks.

Comparative example 2:

most of them are the same as in example 1 except that the step of hydrogen plasma etching is omitted. As shown in fig. 7, in the diamond coating without hydrogen plasma etching, the coating morphology has many fine particles and a small portion of graphite phase, and the grain boundary is not very clear. The test is carried out by adopting 150kg Rockwell indentation, and compared with the indentation morphology etched by adopting hydrogen plasma at 500 ℃, the crack is larger and has the tendency of diffusing around.

Comparative example 3:

compared with example 1, most of the metal components are the same, except that the metal component of Co is omitted from the polycrystalline diamond compact substrate formula, and the ratio of the metal components is unchanged, and the diamond coating is shown in fig. 8 (a).

Comparative example 4:

compared with example 1, most of the metal components are the same, except that in the polycrystalline diamond compact substrate formula, the metal component of Cu is omitted, the proportion of the metal components is unchanged, and the diamond coating is shown in figure 8 (b).

Comparative example 5:

compared with example 1, most of the metal components are the same, except that the metallic component of Sn is omitted from the formulation of the polycrystalline diamond compact substrate, and the ratio of the metal components is unchanged, and the diamond coating is as shown in fig. 8 (c).

The Co and other components in the hard alloy can penetrate into diamond, promote bonding and adhesion of diamond particles and enhance the machinability of a matrix. The lack of Co as a metal component can reduce the possibility of forming microcracks between the diamond coating and the metal cobalt due to the larger difference between the thermal expansion coefficient of cobalt and that of diamond, but the SEM appearance is poor. Copper with low cauterization points is used as bonding metal, Cu can be melted through alloy, the matrix is soaked through infiltration, Cu and Sn and Cu and Co are diffused mutually, binding force between the matrix is improved, and holding force of the matrix to diamond is improved. The metal component Cu or Sn is lacked, the good wettability of the metal to diamond is lacked, and the SEM appearance is poor. And meanwhile, 150kg of Rockwell indentations are adopted for testing, and compared with the indentation morphology containing Co, Cu and Sn at 500 ℃, the cracks are relatively large. The lack of these metal elements can weaken the bonding strength of diamond coating film base, and the improved metal base formula is favorable to improving and strengthening the coating performance.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. A method of low temperature deposition of a polycrystalline diamond compact with a CVD diamond coating, comprising the steps of:

(1) preparing a polycrystalline diamond compact substrate;

2. A method of low temperature deposition of a polycrystalline diamond compact with a CVD diamond coating according to claim 1, wherein in step (1), the polycrystalline diamond compact substrate is prepared by: mixing diamond micro powder and metal alloy, wherein the diamond micro powder is formed by mixing particles with the particle size of 25-30 meshes and particles with the particle size of 40-50 meshes according to the mass ratio of 1: 1; the metal alloy comprises the following components: 54-58 wt% of WC, 3-7 wt% of Co, 28-34 wt% of Cu and 5-15 wt% of Sn, and sintering at high temperature and high pressure by adopting a powder metallurgy method to obtain the polycrystalline diamond compact substrate.

3. A method of low temperature deposition of a polycrystalline diamond compact with a CVD diamond coating as claimed in claim 2, wherein the mass ratio of diamond micropowder to metal alloy is 4: 1.

4. The method of claim 2, wherein the sintering process comprises: sintering at the temperature of 1000-1200 ℃ under the condition of 5GPa, keeping the temperature for 5-15min, cooling to 800 ℃, discharging, and cooling to room temperature.

5. A method of low temperature deposition of a polycrystalline diamond compact with a CVD diamond coating according to claim 2, wherein the diamond micro powder used has a particle size of one or more of nanocrystalline, sub-nanocrystalline, fine grain or coarse grain.

6. A method of low temperature deposition of a polycrystalline diamond compact with a CVD diamond coating according to claim 1, wherein in step (2), the volume ratio of hydrogen to methane is 49: 1; in the nucleation treatment process, the air pressure in the reaction cavity is 5kPa, the microwave frequency is 2.45GHz, the power of the microwave source is set to be 1kW, then the reactor is started, and the nucleation time is 30 min.

7. A method of low temperature deposition of a polycrystalline diamond compact with a CVD diamond coating according to claim 1, wherein in step (3) the ratio of the flow rates of hydrogen, methane and carbon dioxide is 200: (5-7): (4-6).

8. A method of low temperature deposition of a polycrystalline diamond compact with a CVD diamond coating as claimed in claim 1, wherein in step (3) the deposition process comprises: the deposition pressure is 6-9 kPa, the microwave power is 600-900W, the deposition temperature is 500-700 ℃ and the deposition time is 6-10 h.

9. The method of claim 1, wherein in step (4), the etching process comprises the following specific process conditions: the pressure is 9-15 kPa, the microwave power is 600-1000W, the etching temperature is 700-900 ℃, and the time is 5-15 min.

10. A method of low temperature deposition of a polycrystalline diamond compact with a CVD diamond coating according to claim 1, wherein the CVD diamond coating is deposited to a thickness of not less than 0.01 mm.