1. A preparation method of PCBN cutter with a nano-diamond film coating on the surface is characterized by comprising the following steps:

(1) dry polishing the pretreated PCBN cutter in nano diamond powder to brightness, then placing the PCBN cutter on a base station, placing the PCBN cutter in a microwave plasma chemical vapor deposition system for vacuumizing, and introducing a first reaction source gas after vacuumizing;

(2) and starting a microwave plasma chemical vapor deposition system, exciting a first reaction source gas by microwave to generate a plasma ball, introducing a second reaction source gas to start deposition, and obtaining the PCBN cutter with the surface provided with the nano-diamond film coating after the deposition is finished.

2. The method according to claim 1, wherein the pretreatment of step (1) comprises ultrasonic cleaning and drying;

preferably, the cleaning solution adopted by the ultrasonic cleaning is acetone;

preferably, the ultrasonic cleaning time is 8-12 min;

preferably, the drying is carried out in a constant temperature drying oven;

preferably, the drying time is not less than 4 min;

preferably, the drying temperature is 45-55 ℃.

3. The method according to claim 1 or 2, wherein the nano-diamond powder of step (1) has a particle size of 10to 500 nm.

4. The method according to any one of claims 1to 3, wherein the dry polishing time in the step (1) is 10to 25 min.

5. The production method according to any one of claims 1to 4, wherein the first precursor gas of step (1) is H₂；

Preferably, the second precursor gas of step (1) is CH₄；

Preferably, the CH₄And H₂The gas flow rate ratio of (0.5-8): 50.

6. The method according to any one of claims 1to 5, wherein in the step (2), the power of the microwave is 500 to 700W;

preferably, the pressure of the working chamber in the process of generating the plasma ball in the step (2) is 8-12 Torr.

7. The method according to any one of claims 1to 6, wherein the power of the microwave is adjusted to 1000 to 2000W during the deposition in step (2);

preferably, in the deposition process in the step (2), the pressure of the working chamber is 20to 60 Torr;

preferably, in the deposition process in the step (2), the temperature of the base station is 600-900 ℃;

preferably, the deposition time in the step (2) is 6-12 h.

8. The method according to any one of claims 1to 7, wherein the thickness of the nanodiamond thin film coating of step (2) is 5 to 15 μm.

9. The method of any one of claims 1to 8, comprising the steps of:

(1) ultrasonically cleaning a PCBN cutter for 8-12 min by using acetone, drying for not less than 4min at 45-55 ℃, then dry-polishing in diamond powder with the particle size of 10-500 nm for 10-25 min, then placing on a base station with the height of 40-55 mm, placing in a microwave plasma chemical vapor deposition system, vacuumizing to the limit vacuum, and introducing a first reaction source gas after vacuumizing;

(2) starting a microwave plasma chemical vapor deposition system, setting the microwave power to be 500-700W, setting the air pressure of a working cavity to be 8-12 Torr, exciting a first reaction source gas to generate a plasma ball, then introducing a second reaction source gas to start deposition, wherein the gas flow ratio of the second reaction source gas to the first reaction source gas is (0.5-8): 50, adjusting the microwave power to be 1000-2000W in the deposition process, setting the air pressure of the working cavity to be 20-60 Torr, setting the temperature of a base station to be 600-900 ℃, depositing for 6-12 h, and obtaining the PCBN cutter with the nano diamond film coating of 5-15 mu m on the surface after deposition is finished.

10. A PCBN cutter, wherein the surface of the PCBN cutter has a nano-diamond thin film coating prepared by the method of any one of claims 1to 9.

Background

In recent years, Polycrystalline Cubic Boron Nitride (PCBN) cutters are increasingly used as a novel superhard material in modern precision machining, and particularly show incomparable superiority with other cutter materials in the fields of high-speed cutting, hard cutting, dry cutting and the like. PCBN is an artificial synthetic substance with hardness second to that of diamond, but different from the diamond tool, the PCBN tool has poor affinity with Fe, and is particularly suitable for cutting ferrous metal; compared with a hard alloy cutter, the durability of the PCBN cutter is more than 10 times, the cutting force is small when ultrahigh-strength materials and chemical active materials are cut at high speed, and no accumulated chip is generated in the cutting process; compared with a ceramic cutter, the PCBN cutter has higher hardness, wear resistance and thermal conductivity, better chemical stability, thermal stability and red hardness in machining, and can realize turning instead of grinding under specific cutting conditions, so that the machined workpiece obtains higher machining precision and surface quality and simultaneously greatly improves the production efficiency. However, since the cost of the PCBN tool is high, if it cannot be guaranteed that the tool will have a long life in the machining process, the production cost will be increased, and meanwhile, the severe wear of the tool will cause the workpiece to be scrapped and need to be re-machined, which seriously affects the production efficiency and economic benefits. Therefore, it is of great practical significance to find a method for improving the wear resistance and service life of the tool.

Covering a layer of diamond film on the surface of the PCBN cutter is an effective means for prolonging the service life of the PCBN cutter. The existing Chemical Vapor Deposition diamond film coating technology mainly uses a Hot Filament Chemical Vapor Deposition (HFCVD) method, but the HFCVD method has a complex preparation process, and the prepared diamond film has Filament pollution and great difficulty in improving the quality of the film. In addition, since the temperature of the filament in the HFCVD method is generally more than 2000 ℃, the filament material is volatilized into the reaction chamber, thereby introducing impurities into the thin film, reducing the purity of the diamond film, and resulting in low reproducibility and yield. In addition, the substrate material is mainly concentrated on diamond cutters, hard alloy cutters and ceramic cutters, and most of the diamond films on the surfaces of the coated cutters are in micron-scale. However, the micron diamond film has coarse and uneven grains, a rough coating surface, and difficulty in surface polishing, and causes great wear and high cutting force when the tool contacts with a workpiece, thereby seriously affecting the service life of the coated tool.

CN105861995A discloses ZrTiN-MoS₂The tool with laminated Ti/Zr coating is made of high speed steel, hard alloy, cubic boron nitride or diamond as base material and MoS on the surface₂the/Ti/Zr lubricating coating comprises a Ti transition layer, a Ti/Zr transition layer, a ZrTiN hard coating and MoS from a substrate to the surface of the coating in sequence₂a/Ti/Zr lubricating coating alternating laminated composite structure; the cutter has more coatings, is prepared by adopting an arc plating and medium-frequency magnetron sputtering composite coating method, and has more complex process flow and higher cost.

CN106637143A discloses a preparation method of an MPCVD diamond film, which adopts inert gas Ar as catalytic gas in the deposition process to play the roles of refining the crystal grains of the diamond film, improving the hardness of the diamond film and improving the quality of the diamond film; however, the inert gas Ar can cause the reduction of the hydrogen concentration, so that enough active hydrogen atoms are not etched, the non-diamond phase components are increased, and the quality of the diamond film is influenced.

In summary, how to provide a continuous and compact thin film coating with a certain thickness that is deposited uniformly on the surface of the PCBN tool, which ensures that the bonding force and the supporting force between the thin film coating and the substrate are not changed, and improves the cutting performance, is a problem that needs to be solved at present.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a PCBN cutter with a nano-diamond film coating on the surface and a preparation method thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

in one aspect, the invention provides a preparation method of a PCBN cutter with a nano-diamond film coating on the surface, which comprises the following steps:

(1) dry polishing the pretreated PCBN cutter in nano diamond powder to brightness, then placing the PCBN cutter on a base station, placing the PCBN cutter in a microwave plasma chemical vapor deposition system for vacuumizing, and introducing a first reaction source gas after vacuumizing;

(2) and starting a microwave plasma chemical vapor deposition system, exciting a first reaction source gas by microwave to generate a plasma ball, introducing a second reaction source gas to start deposition, and obtaining the PCBN cutter with the surface provided with the nano-diamond film coating after the deposition is finished.

According to the preparation method, by adopting and optimizing a Microwave Plasma Chemical Vapor Deposition (MPCVD) process, a transition layer is not required to be prepared or surface modification is not required to be carried out on a PCBN cutter substrate, and the nano-scale diamond film coating which is continuous, compact, high in adhesive strength, large in binding force, uniform in coating thickness and smooth and flat in surface can be obtained through Deposition, so that abrasion and cutting force generated when the PCBN cutter is in contact with a workpiece can be effectively reduced, and the service life of the coated cutter is prolonged; compared with the conventional Hot Filament Chemical Vapor Deposition (HFCVD) process, the method simplifies the process flow, avoids the problem of film growth stability caused by uneven wire drawing, avoids the problem of product surface pollution caused by Hot Filament breakage in the preparation process, and greatly improves the product yield.

The following technical solutions are preferred technical solutions of the present invention, but not limited to the technical solutions provided by the present invention, and technical objects and advantageous effects of the present invention can be better achieved and achieved by the following technical solutions.

As a preferable technical scheme of the invention, the pretreatment in the step (1) comprises ultrasonic cleaning and drying.

Preferably, the cleaning solution adopted by the ultrasonic cleaning is acetone.

Preferably, the ultrasonic cleaning time is 8-12 min, such as 8min, 9min, 10min, 11min or 12min, but not limited to the recited values, and other values not recited in the range of values are also applicable.

Preferably, the drying is carried out in a constant temperature drying oven.

Preferably, the drying time is not less than 4min, such as 4min, 5min, 6min, 7min, 8min, or 9min, but not limited to the recited values, and other values not recited within the range of values are equally applicable.

Preferably, the drying temperature is 45 to 55 ℃, for example, 45 ℃, 46 ℃, 47 ℃, 48 ℃, 49 ℃, 50 ℃, 51 ℃, 52 ℃, 53 ℃, 54 ℃ or 55 ℃, but not limited to the values listed, and other values not listed within the range of values are also applicable.

According to the invention, the surface purification and crystal planting process is comprehensively optimized by the cutter pretreatment method, and the adsorbates and pollutants on the surface of the cutter are effectively removed by selecting a proper reagent, so that the surface microscopic quality is improved; and then nano diamond powder is used for dry polishing until the surface is bright, so that the activity and high-energy points of the surface of the cutter are increased. Compared with ultrasonic treatment of a diamond powder-containing suspension, the crystal planting process can obtain more defects such as scratches, dislocations, crystal boundaries and the like, the defects provide nucleation work for diamond nucleation, and diamond powder fragments remained in the defects on the surface of the cutter provide nucleation points for MPCVD deposited diamond, so that the nucleation density is improved. Meanwhile, the nucleation growth mode enables the diamond film and the cutter to act with an anchor chain effect, so that the adhesive force of the film and the substrate is improved.

As a preferable embodiment of the present invention, the nano-diamond powder of the step (1) has a particle size of 10to 500nm, for example, 10nm, 50nm, 100nm, 200nm, 300nm, 400nm or 500nm, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.

In a preferred embodiment of the present invention, the dry polishing time in step (1) is 10to 25min, for example, 10min, 12min, 15min, 18min, 20min, 22min, or 25min, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned range are also applicable.

In the present invention, the height of the base in the step (1) is 40to 55mm, for example, 40mm, 42mm, 45mm, 48mm, 50mm, 52mm, or 55mm, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.

In the present invention, the height of the base has a certain influence on the quality of the final film formation. If the height of the base station is too high, the ionization degree of a sample contacting the center position of the plasma is increased; if the height of the base station is too low, the distance between the plasma ball and the sample is increased, and the plasma glow cannot completely cover the sample; both of which lead to a decrease in the surface uniformity and film stability of the coating.

In the invention, the step (1) of vacuumizing to limit vacuum avoids poor crystal texture quality of the nano diamond coating and high impurity content in the film caused by impurity gas contained in an MPCVD system.

In a preferred embodiment of the present invention, the first precursor gas in step (1) is H₂。

Preferably, the second precursor gas of step (1) is CH₄。

Preferably, the CH₄And H₂The gas flow rate ratio is (0.5 to 8):50, for example, 1:100, 1:50, 1:25, 3:50, 2:25, 1:10, 3:25, 7:50, or 4:25, but is not limited to the recited values, and other values not recited within the range of the values are also applicable.

In the present invention, the CH₄And H₂The gas flow rate is given in units of "sccm".

In the present invention, during the deposition processThe proportion of the source gases for the reaction is of critical importance. If the carbon source (CH)₄) When the content is excessive, H is inevitably reduced₂The concentration and a large amount of hydrocarbon groups absorbed on the surface of the cutter are not etched by enough active hydrogen atoms, so that the non-diamond phase components are increased, and the purity of diamond in the film is reduced; in addition, the high concentration of the carbon source can cause the nucleation and growth rate of diamond grains to be too fast, and the film thickness is not easy to control. If H is₂When the content is too large, the surface of the cutter does not have enough hydrocarbon groups for forming diamond grains, so that the deposition rate of the film coating is reduced; in addition, fewer hydrocarbon groups reduce the probability of secondary nucleation, and thus smaller size diamond grains cannot be obtained.

In a preferred embodiment of the present invention, in the process of generating the plasma sphere in the step (2), the power of the microwave is 500 to 700W, for example, 500W, 550W, 600W, 650W, 700W, etc., but the microwave is not limited to the above-mentioned values, and other values not listed in the above-mentioned range of values are also applicable.

Preferably, the pressure of the working chamber during the plasma ball generation in step (2) is 8to 12Torr, such as 8Torr, 9Torr, 10Torr, 11Torr, or 12Torr, but not limited to the values listed, and other values not listed in this range are also applicable.

In a preferred embodiment of the present invention, in the deposition process in step (2), the power of the microwave is adjusted to 1000 to 2000W, for example, 1000W, 1100W, 1200W, 1300W, 1400W, 1500W, 1600W, 1700W, 1800W, 1900W, 2000W, etc., but the present invention is not limited to the above-mentioned values, and other values not listed in the above-mentioned range are also applicable.

Preferably, the pressure of the working chamber during the deposition in step (2) is 20to 60Torr, such as 20Torr, 30Torr, 40Torr, 50Torr or 60Torr, but not limited to the values listed, and other values not listed in the range of the values are also applicable.

According to the preparation method, the volume and the density of the generated plasma spheres are further controlled by cooperatively regulating the microwave power and the working cavity air pressure, so that the uniformity of the surface temperature field of the cutter substrate, and the deposition rate and the growth quality of a film are improved. If the microwave power is too high during deposition, the intensity of the plasma is correspondingly increased, so that the surface of the cutter is bombarded more intensely by ions, and the temperature of the base body of the cutter is increased; if the microwave power is too low during deposition, the volume of the plasma ball is reduced, and the plasma density is reduced; both fail to obtain a high quality nano-diamond film with a uniform surface. If the air pressure of the working cavity during deposition is too high, the average free path of molecules is reduced, the average free path of hydrogen atoms and carbon-containing groups is shortened, secondary nucleation is not easy to generate when the hydrogen atoms and the carbon-containing groups collide with a cutter matrix, and diamond particles are easy to grow; if the air pressure of the working cavity during deposition is too small, the number of free radicals in the reaction chamber is reduced, and carbon elements capable of generating diamond are reduced to a certain extent, so that the growth rate of the diamond is reduced, and the cutting performance of the diamond coated tool is finally influenced along with the appearance of more graphite and amorphous carbon in the film and the reduction of adhesive force between the coating and the tool substrate.

Preferably, in the deposition process in the step (2), the temperature of the base is 600 to 900 ℃, for example, 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃, 900 ℃, etc., but not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the deposition time in step (2) is 6-12 h, such as 6h, 7h, 8h, 9h, 10h, 11h or 12h, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

In the invention, the preparation method effectively inhibits the growth of crystal grains through secondary nucleation, thereby improving the film quality and stability of the diamond coating.

In a preferred embodiment of the present invention, the thickness of the nanodiamond thin film coating in step (2) is 5 to 15 μm, for example, 5 μm, 6 μm, 7 μm, 8 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or 15 μm, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned range are also applicable.

As a preferred technical scheme of the invention, the preparation method comprises the following steps:

(1) ultrasonically cleaning a PCBN cutter for 8-12 min by using acetone, drying for not less than 4min at 45-55 ℃, then dry-polishing in diamond powder with the particle size of 10-500 nm for 10-25 min, then placing on a base station with the height of 40-55 mm, placing in a microwave plasma chemical vapor deposition system, vacuumizing to the limit vacuum, and introducing a first reaction source gas after vacuumizing;

(2) starting a microwave plasma chemical vapor deposition system, setting the microwave power to be 500-700W, setting the air pressure of a working cavity to be 8-12 Torr, exciting a first reaction source gas to generate a plasma ball, then introducing a second reaction source gas to start deposition, wherein the gas flow ratio of the second reaction source gas to the first reaction source gas is (0.5-8): 50, adjusting the microwave power to be 1000-2000W in the deposition process, setting the air pressure of the working cavity to be 20-60 Torr, setting the temperature of a base station to be 600-900 ℃, depositing for 6-12 h, and obtaining the PCBN cutter with the nano diamond film coating of 5-15 mu m on the surface after deposition is finished.

In another aspect, the invention provides a PCBN cutter, and the surface of the PCBN cutter is provided with the nano-diamond film coating prepared by the preparation method.

Compared with the prior art, the invention has the following beneficial effects:

(1) the preparation method of the invention adopts and optimizes the MPCVD process, and can directly deposit and obtain the continuous compact, high adhesive strength, large binding force, even coating thickness and smooth and flat surface nano-scale diamond film coating without preparing a transition layer or surface modification on the PCBN cutter substrate in advance, thereby solving the problems of complex preparation process, micron-scale crystal grains on the surface of the coating, poor binding force between the film and the cutter, difficult post-polishing and the like in the prior art for preparing the diamond coating by the HFCVD process; the height of a base station, microwave power, working chamber air pressure and gas proportion in the MPCVD process are further controlled, so that the grain size and the film uniformity are further controlled, the abrasion and cutting force generated when the cutter is in contact with a workpiece are reduced, and the service life of the cutter is further prolonged;

(2) the preparation method has simple process flow, MPCVD has no internal electrode, can avoid electrode discharge, and the axisymmetric plasma ball is not contacted with the wall of the vacuum vessel, thereby reducing pollution.

Drawings

Fig. 1 is a process flow chart of the process of preparing a cutting tool with a nano-diamond film coating on the surface according to example 1 of the present invention.

FIG. 2 is a surface topography of the nano-diamond film coating on the surface of the cutting tool provided in example 1 of the present invention.

FIG. 3 is a grain morphology diagram of the tool surface nano-diamond thin film coating provided in example 1 of the present invention.

FIG. 4 is a sectional view of the tool surface nano-diamond film coating provided in example 1 of the present invention.

Fig. 5 is an XRD pattern of the nano-diamond film coating on the surface of the tool provided in example 1 of the present invention.

FIG. 6 is a Raman spectrum of the nano-diamond film coating on the surface of the cutting tool provided in example 1 of the present invention.

Detailed Description

In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the present invention, which is defined by the claims.

The following are typical but non-limiting examples of the invention:

example 1:

the embodiment provides a preparation method of a cutting tool with a nano-diamond film coating on the surface, and the process flow chart of the preparation method is shown in figure 1.

The preparation method comprises the following steps:

(1) ultrasonically cleaning PCBN cutter with acetone for 10min, drying at 50 deg.C for 4min, and adjusting the particle diameter toDry polishing 100nm diamond powder for 15min to brightness, placing on a 40 mm-high base table, placing in an MPCVD system, vacuumizing to limit vacuum, introducing H₂；

(2) Starting the MPCVD system, setting the microwave power to be 600W, setting the air pressure of the working chamber to be 10Torr, and exciting H₂Generating plasma ball, and introducing CH₄Starting deposition of said CH₄And H₂The gas flow ratio of the gas flow ratio is 1:50, the microwave power is adjusted to be 1500W in the deposition process, the air pressure of the working cavity is 40Torr, the temperature of the base station is 700 ℃, the deposition is carried out for 10h, and the PCBN cutter with the nano-diamond film coating on the surface is obtained after the deposition is finished.

The nano-diamond film coating on the surface of the PCBN cutter is characterized, the surface topography is shown as figure 2, the grain topography is shown as figure 3, the cross-sectional topography is shown as figure 4, the XRD spectrum is shown as figure 5, and the Raman spectrum is shown as figure 6.

As can be seen from FIG. 2, the nano-diamond coating has been uniformly deposited on the surface of the PCBN tool, the coated diamond film is continuous, compact in structure and high in surface smoothness, obvious grain boundaries exist among grains, and an obvious secondary nucleation phenomenon can be observed at the grain boundaries, which indicates that the prepared nano-diamond film has high quality.

As can be seen from fig. 3, the diamond grains in the thin film coating have good crystallinity, are clustered and have a typical nanoscale diamond structure, i.e., a so-called cauliflower-like morphology, and the diamond grains have substantially the same size and an average size of 50nm or less.

As can be seen from fig. 4, the nano-diamond film does not grow in a columnar shape as in the conventional film, but is a growth mode in which grains are stacked. The secondary nucleation phenomenon is continuously generated on the surface of the film in the process of the growth of the nano-diamond film, the growth of crystal grains is inhibited, the crystal grains are refined, and the diamond crystal grains are continuously accumulated on the surface of the film along with the extension of the deposition time. In addition, it can be observed from the cross-sectional morphology that the surface of the nano-diamond film was smooth and flat, which is consistent with the results obtained in fig. 2.

As is clear from fig. 5, there are two distinct diffraction peaks at 43.92 ° 2 θ and 75.32 ° 2 θ, which correspond to the (111) and (220) crystal planes of the diamond crystal, respectively, indicating that the nano-diamond film has high crystallinity and high grain orientation density.

As can be seen from FIG. 6, the depth is 1332cm^-1A wider raman scattering peak (D peak) appears, indicating that the film contains diamond phase. The reason why the peak is wide is that the D peak and the diamond characteristic peak in the vicinity thereof are superimposed on each other. At 1579cm^-1The G peak at (a) corresponds to graphitic and amorphous carbon structures. At 1150cm^-1The characteristic peaks of the nano-diamond appearing nearby show that the diamond component in the film is increased, the crystal grains are refined, and the purity of the film is higher. In addition, the drift amount of the G peak in the Raman spectrum is small, which shows that the residual stress in the film coating is small, and the quality of the nano-diamond film is high.

Example 2:

the embodiment provides a preparation method of a PCBN cutter with a nano-diamond film coating on the surface, which comprises the following steps:

(1) ultrasonically cleaning PCBN cutter with acetone for 8min, drying at 45 deg.C for 5min, dry-polishing in diamond powder with particle size of 10nm for 20min to brightness, placing on a base station with height of 55mm, placing in MPCVD system, vacuumizing to limit vacuum, vacuumizing, and introducing H₂；

(2) Starting the MPCVD system, setting the microwave power at 500W and the working chamber pressure at 8Torr, exciting H₂Generating plasma ball, and introducing CH₄Starting deposition of said CH₄And H₂The gas flow ratio of the deposition process of the PCBN tool is 4:25, the gas pressure of the working cavity is 20Torr, the temperature of the base platform is 600 ℃, the deposition is carried out for 12 hours, and the PCBN tool with the nano-diamond film coating on the surface is obtained after the deposition is finished.

Example 3:

the embodiment provides a preparation method of a PCBN cutter with a nano-diamond film coating on the surface, which comprises the following steps:

(1) firstly, the PCBN cutter is firstlyUltrasonically cleaning with acetone for 12min, drying at 45 deg.C for 4min, dry-polishing in 500nm diamond powder for 18min to brightness, placing on a 45mm height base table, vacuumizing in MPCVD system to limit vacuum, vacuumizing, and introducing H₂；

(2) Starting the MPCVD system, setting the microwave power at 700W and the working chamber pressure at 12Torr, exciting H₂Generating plasma ball, and introducing CH₄Starting deposition of said CH₄And H₂The gas flow ratio of the gas flow ratio is 1:100, the microwave power is adjusted to be 2000W in the deposition process, the air pressure of the working cavity is 60Torr, the temperature of the base station is 900 ℃, the deposition is carried out for 6h, and the PCBN cutter with the nano-diamond film coating on the surface is obtained after the deposition is finished.

Example 4:

this example provides a method of making a PCBN tool with a nanodiamond thin film coating on the surface, which is comparable to the method of example 1, except that: the height of the base table in the step (1) is 35 mm.

Example 5:

this example provides a method of making a PCBN tool with a nanodiamond thin film coating on the surface, which is comparable to the method of example 2, except that: the height of the base table in the step (1) is 60 mm.

Example 6:

this example provides a method of making a PCBN tool with a nanodiamond thin film coating on the surface, which is comparable to the method of example 2, except that: and (3) adjusting the microwave power to 800W in the deposition process in the step (2).

Example 7:

this example provides a method of making a PCBN tool with a deep sub-micron diamond film coating on the surface, the method being referred to the method of example 3, except that: and (3) adjusting the microwave power to 2200W in the deposition process in the step (2).

Example 8:

this example provides a method of making a PCBN tool with a nanodiamond thin film coating on the surface, which is comparable to the method of example 2, except that: and (3) the pressure of the working chamber in the deposition process in the step (2) is 10 Torr.

Example 9:

this example provides a method of making a PCBN tool with a deep sub-micron diamond film coating on the surface, the method being referred to the method of example 3, except that: and (3) the pressure of the working chamber in the deposition process in the step (2) is 70 Torr.

Comparative example 1:

this comparative example provides a method of making a PCBN tool with a sub-micron diamond film coating on the surface, the method of manufacture being referenced to that of example 1, except that: in the step (1), the PCBN cutter does not carry out nano-diamond powder dry polishing treatment, but adopts a diamond-containing powder alcohol suspension for ultrasonic treatment.

The surface quality, diamond grain size, film thickness and uniformity of the tool with diamond film coating obtained in examples 1to 9 and comparative example 1 were observed, and the results are shown in table 1.

TABLE 1

In the embodiment 1-3, the microwave plasma chemical vapor deposition technology is adopted, the PCBN cutter pretreatment and crystal planting process are optimized, and the reaction conditions in the deposition process are further controlled, so that the surface of the cutter is provided with the nano-diamond film coating which is continuous and compact, uniform in coating thickness, flat and smooth in surface and not easy to cause stress concentration, the abrasion and cutting force generated when the cutter is in contact with a workpiece are effectively reduced, and the service life of the coated cutter is prolonged; in the embodiments 4 to 5, the height of the base table is respectively reduced and increased in the preparation process, so that the distance between the cutter substrate and the plasma ball is remarkably changed, the smoothness of the obtained coating and the stability of the film are reduced, and particularly when the height of the base table is too low, the plasma glow can not completely cover the sample, and the quality of the film is seriously reduced; example 6 the microwave power during deposition was reduced during the preparation process, resulting in a reduction in plasma density, a reduction in thickness and uniformity of the resulting film, and cracks appearing on the surface of the coating; example 7 in the preparation process, the microwave power during deposition is increased, which leads to the increase of the substrate temperature and the reduction of the energy of active groups, thereby reducing the probability of secondary nucleation, increasing the grain size of the obtained diamond film to submicron level, and obviously increasing the surface roughness of the coating; example 8 in the preparation process, the working chamber air pressure is reduced, the growth rate of diamond is reduced, and the cutting performance of the diamond coated cutter is influenced; example 9 the working chamber pressure was increased during the preparation process, the mean free path of hydrogen atoms and carbon containing groups was shortened, secondary nucleation was not easily generated upon collision with the tool substrate, resulting in easy growth of diamond particles.

In the comparative example 1, the conventional crystal planting process is adopted, so that the micro defects and nucleation centers on the surface of the cutter substrate are fewer, the initial and secondary nucleation rates are reduced, and the quality of the obtained diamond film coating is poorer.

It can be seen from the above examples and comparative examples that the preparation method of the present invention, by adopting and optimizing the MPCVD process, can deposit and obtain a continuous, compact, high adhesion strength, large bonding force, uniform coating thickness, smooth and flat surface nanoscale diamond film coating without preparing a transition layer or modifying the surface on the PCBN tool substrate in advance, and solves the problems of complex preparation process, micron-sized grains on the surface of the coating, poor bonding force between the film and the tool, difficult post-polishing, etc. existing in the existing HFCVD process for preparing diamond coatings; the height of a base table, the microwave power, the air pressure of a working cavity and the gas ratio in the MPCVD process are further controlled, so that the grain size and the film uniformity are further controlled, the abrasion and the cutting force generated when the tool is in contact with a workpiece are reduced, and the service life of the PCBN tool is further prolonged; the preparation method has simple process flow, the MPCVD has no internal electrode, can avoid electrode discharge, and the axisymmetric plasma sphere is not contacted with the wall of the vacuum vessel, thereby reducing pollution.

The applicant states that the present invention is illustrated by the above examples to show the product and detailed method of the present invention, but the present invention is not limited to the above products and detailed method, i.e. it is not meant that the present invention must rely on the above products and detailed method to be carried out. It will be apparent to those skilled in the art that any modifications to the present invention, equivalents thereof, additions of additional operations, selection of specific ways, etc., are within the scope and disclosure of the present invention.