KR101519339B1 - Diamond coated cutting tool with excellent surface roughness and method of coating diamond with excellent surface roughness for cutting tool - Google Patents

Abstract

This technology suppresses the nucleation of diamond particles to form fine diamond particles. By controlling the content ratio of SP3 and SP2 structure of diamond and applying the surface pretreatment technique, the surface roughness and friction coefficient are improved compared to the conventional diamond coating. This technology ensures superior cutting performance and lifetime compared to DLC coating in aluminum alloy (duralumin) and carbon fiber plate (CFRP, carbon fiber-reinforced polymer) and it can greatly improve cutting roughness compared to diamond coating.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a diamond coating method and a diamond coating method for a cutting tool and a cutting tool coated with a diamond having excellent surface roughness.

The present invention relates to a cutting tool coated with a diamond having excellent surface roughness and a method of coating a diamond tool having excellent surface roughness on a cutting tool. More specifically, the present invention relates to a diamond tool for realizing fine diamond particles through nucleation control of diamond particles, To a technique capable of improving the surface roughness and the coefficient of friction as compared with the conventional diamond coating film by adjusting the content ratio of the SP3 and SP2 structures.

Diamond is one of the hardest materials on earth. Diamond-coated cutting tools artificially created through vapor phase synthesis (CVD) are used today to machine hard-to-machine, aluminum-silicon (Al-Si) alloys, magnesium alloys and graphite materials.

Generally, the diamond coating film is formed by a chemical vapor deposition (CVD) method in which plasma or thermal energy is converted into various kinds of power sources (DC, AC, high frequency, microwave) in a mixed gas atmosphere containing hydrocarbon, A hot filament, a combustion flame, a DC glow discharge plasma, an arc glow discharge plasma jet, and a microwave plasma. Among them, the hot filament method is generally used for the coating for the cemented carbide cutting tool.

When a diamond coating film is formed by the hot filament method, conventionally, in order to obtain a stable diamond coating film, as shown in Fig. 1, a copper plate (Cu plate) arranged at a predetermined interval in the chamber and a plurality The inserts are arranged at predetermined intervals using a vertical jig beneath a hot filament device including tungsten wires arranged in parallel to each other and power is applied to the copper plates to apply a high temperature resistance to the tungsten wire After the heat was generated, a reaction gas containing hydrocarbon was injected into the CVD apparatus to form a diamond coating film on the upper surface of the insert.

However, the diamond coating film formed through the diamond coating method using the conventional hot filament has an SP3 structure with a high hardness (Hv) but a rough surface and a coefficient of friction higher than that of the DLC coating, so that an aluminum alloy (for example, duralumin) When a workpiece such as a fiber-reinforced plastic (CFRP) plate is machined, the machining roughness of the workpiece is high.

Further, in the diamond coating method using the conventional hot filament, if a low temperature coating of 650 ° C or less is applied in order to lower the surface roughness, there is a problem that minimum adhesion between the diamond coating film and the cemented carbide base material is not ensured.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the prior art described above, and it is an object of the present invention to provide a cutting tool in which a diamond coating film formed of fine diamond grains, will be.

Another object of the present invention is to provide a method of forming a coating film of finely controlled diamond particles while ensuring a minimum degree of adhesion to the surface of a cutting tool.

In order to solve the above problems, the present invention provides a cutting tool in which a diamond coating film is formed using chemical vapor deposition (CVD), wherein the diamond coating film is made of columnar particles and the average primary particle size of the columnar primary particles is 1 탆 or less, there is provided a graphite SP2 (1580cm ^-1) and SP3 diamond Raman spectrum peak intensity ratio of ^{(1331cm -1) (I (SP3} / SP2)) is a cutting tool, characterized in that from 1 to 3.5.

In the cutting tool according to the present invention, the diamond coating may have a thickness of 1.5 to 5 탆 and a hardness of 40 to 60 GPa.

In the cutting tool according to the present invention, the surface roughness (Ra) of the diamond coating may be 70 to 250 nm.

In the cutting tool according to the present invention, the coefficient of friction of the diamond coating may be 0.06 to 0.18.

According to another aspect of the present invention, there is provided a cutting tool comprising: (a) a cutting tool having a gas pressure of 10 to 30 Torr in a mixed gas atmosphere of hydrogen and 0.5 to 3% methane, a cutting tool temperature of 750 to 900 deg. C, Coating the cutting tool with a gas pressure of 80 to 100 Torr in a mixed gas atmosphere of hydrogen and 3 to 10% methane at a cutting tool temperature of 800 to 950 ° C and a current of 130 to 140 A for 2 to 6 hours; There is provided a diamond coating method of a cutting tool including a diamond coating method of a cutting tool, which comprises coating a cutting tool at a temperature of 700 to 850 DEG C and a current of 120 to 130A for 30 to 90 minutes.

In the diamond coating method of the cutting tool according to the present invention, the diamond coating film formed by the coating method has a columnar structure, and the average particle size of the columnar crystal grains is 1 탆 or less. The graphite SP2 (1580 cm ^-1 ) The Raman spectral peak intensity ratio I (SP3 / SP2) of SP3 (1331 cm ^-1 ) may be 1 to 3.5.

In the diamond coating method of a cutting tool according to the present invention, a pre-surface treatment for the cutting tool may be performed before the step (a), and the pre-surface treatment may be one of grinding treatment, mirror surface treatment, And may preferably be subjected to mirror-surface treatment.

According to the present invention, it is possible to obtain a degree of adhesion between a coating film and a cutting tool that enables cutting processing, and to realize a diamond coating film having excellent surface roughness compared to conventional ones through nucleation control.

Further, the diamond coating film according to the present invention can greatly improve the processing roughness of the workpiece.

In addition, the cutting tool having the diamond coating film according to the present invention can realize superior cutting performance and lifetime compared with the DLC coating film, especially when processing materials such as an aluminum alloy or a carbon fiber plate such as duralumin.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic diagram showing a diamond coating process.
2 is a graph showing the results of Raman analysis of a diamond coating film prepared according to an embodiment of the present invention.
FIG. 3 is a microphotograph of a plane of a diamond coating film prepared according to Examples and Comparative Examples of the present invention. FIG.
4 is a micrograph of a cross section of a diamond coating film prepared according to a comparative example.
5 is a photomicrograph of a cross section of a diamond coating film prepared according to an embodiment of the present invention.
Fig. 6 is a schematic comparison of the sizes of columnar particles constituting the diamond coating film prepared according to the comparative example and the embodiment of the present invention.

Hereinafter, the present invention will be described based on preferred embodiments of the present invention, but the present invention is not limited to the following examples.

The diamond coating film according to the present invention mainly comprises a first step coating for securing a minimum degree of adhesion of a diamond coating to a cutting tool and a coating step for increasing the content of methane for controlling the particle size of the diamond coating film and coating in a high pressure and high temperature atmosphere And a third step coating step for further increasing the adhesion between the diamond coating film and the cutting tool.

The first step coating is carried out under a gas pressure of 10 to 30 Torr at a filament temperature of 1900 to 2100 占 폚, a mixed gas atmosphere of hydrogen and 0.5 to 3% methane, a cutting tool temperature of 750 to 900 占 폚, a current of 140 to 150 A, Time coating.

In the first step, the filament temperature is preferably 1900 to 2100 DEG C, and when the temperature is less than 1900 DEG C, graphite is generated and when the temperature exceeds 2100 DEG C, diamond is not produced. Also, the content of methane in the hydrogen-methane mixed gas is preferably 0.5 to 3%. If the amount is less than 0.5%, diamond is not formed, and if it is more than 3%, graphite is difficult to produce or diamond is grown. The gas pressure is preferably 10 to 30 Torr. If the pressure is less than 10 Torr, the temperature of the cutting tool is not easily controlled. If the pressure exceeds 30 Torr, graphite is produced. The temperature of the cutting tool is preferably in the range of 750 to 900 DEG C, and graphite is generated when the temperature is lower than 750 DEG C, and diamond is hardly grown when the temperature exceeds 900 DEG C. The current is preferably in the range of 140 to 150 A, and when the diamond grain size is less than 140 A, the diamond particles are inferior in adhesion to the cutting tool. If the diamond grain size exceeds 150 A, the diamond is hardly grown. Also, the coating time is preferably 2 to 6 hours. If the coating time is less than 2 hours, the diamond thickness is thin and the cutting function is deteriorated. If the time exceeds 6 hours, diamond is formed.

The second step coating is characterized in that the cutting tool is coated in a mixed gas atmosphere of hydrogen and 3 to 10% methane at a gas pressure of 80 to 100 Torr, a cutting tool temperature of 800 to 950 ° C, and an electric current of 130 to 140 A for 2 to 6 hours do.

In the second step, the content of methane in the mixed gas of hydrogen and methane is preferably 3 to 10%. When the amount of methane is less than 3%, growth of diamond is difficult, and if it exceeds 10%, graphite is produced. Further, the gas pressure is preferably 80 to 100 Torr. If the pressure is less than 80 Torr, coarse grain growth occurs. If the pressure is more than 100 Torr, it is difficult to coat the front or top of the cutting tool. The temperature of the cutting tool is preferably in the range of 800 to 950 ° C. If the temperature is lower than 800 ° C., the grain refinement occurs. If the temperature is higher than 950 ° C., the diamond hardly grows. The current is preferably in the range of 130 to 140 A, and if it is less than 130 A, the cohesion with the cutting tool is low due to the low temperature coating, and if it exceeds 140 A, coarse particles are formed at high temperature. The coating time is preferably from 2 to 6 hours. If the coating time is less than 2 hours, the thickness growth is difficult. If the coating time exceeds 6 hours, the coating thickness is decreased due to the increase of the coating thickness.

The third step coating is characterized by coating with a gas pressure of 80 to 100 Torr in a mixed gas atmosphere of hydrogen and 3 to 10% methane, a cutting tool temperature of 700 to 850 ° C, and a current of 120 to 130 A for 0.5 to 1.5 hours. The purpose of the coating in the third step is to further enhance the adhesion between the diamond coating and the cutting tool obtained in the coating conditions in the first and second steps. This is due to the more active diffusion of carbon atoms on the surface of the cutting tool as the coating temperature decreases.

In the third step, the content of methane in the mixed gas of hydrogen and methane is preferably 3 to 10%. If the amount of methane is less than 3%, diamond growth is difficult, and if it exceeds 10%, graphite is generated. The gas pressure is preferably 80 to 100 Torr. If the pressure is less than 80 Torr, coarse grain growth occurs. If the pressure is more than 100 Torr, it is difficult to coat the front or top of the cutting tool. The temperature of the cutting tool is preferably in the range of 700 to 850 ° C. If the temperature is less than 700 ° C., fine grain growth occurs. If the temperature exceeds 850 ° C., the diamond is difficult to grow. The current is preferably 120 to 130 A, and it is difficult to grow the diamond when it is less than 120 A, and coarse grain growth occurs when the temperature exceeds 130 A. The coating time is preferably from 0.5 to 1.5 hours. When the time is less than 0.5 hour, the thickness growth and the active diffusion reaction on the cutting tool surface are difficult, and when the time exceeds 1.5 hours, thick diamond growth occurs.

In addition, when the distance between the cutting tool and the filament is less than 5 mm when the cutting tool is put into the coating equipment, the diamond growth is difficult due to the strong electric field around the filament due to the current application, The distance between the cutting tool and the filament is preferably maintained at 5 to 45 mm.

The diamond coating film produced by the above process is made of columnar particles and has an average particle size of the main columnar grains of 1 占 퐉 or less and graphite SP2 (1580 cm ^-1 ) and diamond SP3 (1331 cm ^-1 (I (SP3 / SP2)) of 1 to 3.23 may be 1 to 3.23.

In the present invention, the " average particle size of the columnar stationary particles " is the average of the distances between the crossing points when a line crossing the middle portion of the diamond coating film of the scanning electron microscope it means.

Hereinafter, the present invention will be described in more detail based on preferred embodiments of the present invention.

[Example 1]

WC-6 ~ 8wt% Co. Inserted cutting tool insert with holes in the center with bulk diamond of 60 ~ 80 mesh and polished for 30min using ultrasonic cleaner to form scratch on tool surface.

Thereafter, 1 to 2 minutes in 30% H ₂ SO ₄ (sulfuric acid) + 70% H ₂ O ₂ (hydrogen peroxide water) solution, 35% H ₂ O ₂ (hydrogen peroxide solution) +65 % NaOH (sodium hydroxide) for 40 to 60 minutes. Ultrasonic cleaning using acetone for 30 minutes and ultrasonic cleaning using distilled water for 30 minutes were performed for each of the mediums to remove impurities on the insert surface.

The diamond coating is carried out in a controlled manner in three steps of securing the minimum adhesion (step 1) - controlling the diamond particle size (step 2) - improving the degree of adhesion (step 3), whereby a diamond having good adhesion and low surface roughness Coating layer.

The above step 1 was carried out in a mixed gas atmosphere of 1% methane-hydrogen at a filament temperature of 2000C, a gas pressure of 20Torr, a sample temperature of 900C, a current of 145A and a coating time of 3 hours.

The above step 2 was carried out in a mixed gas atmosphere of 5% methane-hydrogen at a filament temperature of 2200 ° C, a gas pressure of 80 Torr, a sample temperature of 950 ° C, a current of 135 A and a coating time of 3 hours.

The above step 3 was performed in a 5% methane-hydrogen mixed gas atmosphere at a filament temperature of 2000 ° C, a gas pressure of 80 Torr, a sample temperature of 850 ° C, a current of 125 A, and a coating time of 60 minutes.

As described above, the sample temperature and the gas temperature were controlled step by step to form a diamond coating film composed of fine columnar pores.

[Example 2]

A diamond coating film was formed using the insert having the same composition as in Example 1 and subjected to the same polishing treatment.

Concretely, the diamond coating film according to Example 2 is a one-step coating method in which coating is carried out for 5 hours at a filament temperature of 2000 ° C, a gas pressure of 20 Torr, a sample temperature of 900 ° C and a current of 145 A in a mixed gas atmosphere of 1% methane- , A two-step coating in which a filament temperature of 2200 ° C, a gas pressure of 80 Torr, a sample temperature of 950 ° C and an electric current of 140 A was applied for 5 hours in a 5% methane-hydrogen mixed gas atmosphere and a 5% methane- A three-step coating was carried out for 75 minutes at a filament temperature of 2000 占 폚, a gas pressure of 80 Torr, a sample temperature of 850 占 폚 and a current of 130 占 폚.

[Example 3]

A diamond coating film was formed using the insert having the same composition as in Example 1 and subjected to the same polishing treatment.

Specifically, the diamond coating film according to Example 3 is a one-step coating method in which coating is performed for 6 hours at a filament temperature of 2000 占 폚, a gas pressure of 20 Torr, a sample temperature of 750 占 폚 and a current of 140 A in a mixed gas atmosphere of 1% methane- , A two-step coating in which a filament temperature of 2200 ° C, a gas pressure of 80 Torr, a sample temperature of 800 ° C and a current of 130 A was applied for 6 hours in a 5% methane-hydrogen mixed gas atmosphere and a 5% methane- A filament temperature of 2000 占 폚, a gas pressure of 80 Torr, a sample temperature of 700 占 폚 and a current of 120 占 폚 for 90 minutes.

[Example 4]

A diamond coating film was formed using an insert having a composition identical to that of Example 1, subjected to the same polishing treatment, and then mirror-polished on the insert surface with a 0.5-2 μm diamond abrasive using a polishing brush.

Concretely, the diamond coating film according to Example 4 is a one-step coating method in which coating is carried out for 3 hours at a filament temperature of 2000 ° C, a gas pressure of 30 Torr, a sample temperature of 900 ° C and a current of 145 A in a mixed gas atmosphere of 1% methane- , A two-step coating in which a filament temperature of 2200 ° C, a gas pressure of 90 Torr, a sample temperature of 950 ° C and a current of 135 A was applied for 3 hours in a mixed gas atmosphere of 5% methane and hydrogen and a mixed gas atmosphere of 5% methane- A three-step coating was carried out for 60 minutes at a filament temperature of 2000 占 폚, a gas pressure of 90 Torr, a sample temperature of 850 占 폚 and a current of 125 占 폚.

[Example 5]

A diamond coating film was formed using an insert having a composition identical to that of Example 1, subjected to the same polishing treatment, and then mirror-polished on the insert surface with a 0.5-2 μm diamond abrasive using a polishing brush.

Concretely, the diamond coating film according to Example 5 was formed by a one-step coating process in which coating was carried out for 5 hours at a filament temperature of 2000 占 폚, a gas pressure of 30 Torr, a sample temperature of 900 占 폚 and a current of 145 A in a mixed gas atmosphere of 1% methane- , A two-step coating in which a filament temperature of 2200 ° C, a gas pressure of 90 Torr, a sample temperature of 950 ° C and a current of 135 A was applied for 5 hours in a mixed gas atmosphere of 5% methane and hydrogen and a mixed gas atmosphere of 5% methane- A three-step coating was carried out for 75 minutes at a filament temperature of 2000 占 폚, a gas pressure of 90 Torr, a sample temperature of 850 占 폚 and a current of 125 占 폚.

[Example 6]

A diamond coating film was formed using an insert having a composition identical to that of Example 1, subjected to the same polishing treatment, and then mirror-polished on the insert surface with a 0.5-2 μm diamond abrasive using a polishing brush.

The diamond coating film according to Example 6 was prepared in the same manner as in Example 6 except that the coating was carried out for 6 hours at a filament temperature of 2000 ° C, a gas pressure of 20 Torr, a sample temperature of 900 ° C and a current of 145 A in a mixed gas atmosphere of 1% methane- In a mixed gas atmosphere of methane and hydrogen at a filament temperature of 2200 ° C, a gas pressure of 90 Torr, a sample temperature of 950 ° C, and a current of 135 A for 6 hours, Deg.] C, a gas pressure of 90 Torr, a sample temperature of 850 [deg.] C, and a current of 125 A for 90 minutes.

[Example 7]

A diamond coating film was formed by using the insert having the same composition as that of Example 1 and subjected to the same polishing treatment, followed by dry blasting with alumina powder of # 240 mesh size at 1 bar pressure.

The diamond coating film according to Example 7 was produced in the same manner as in Example 7 except that the coating was carried out for 3 hours at a filament temperature of 2000 ° C, a gas pressure of 30 Torr, a sample temperature of 750 ° C and a current of 145 A in a mixed gas atmosphere of 1% methane- A two-stage coating was carried out in a mixed gas atmosphere of methane and hydrogen at a filament temperature of 2200 ° C, a gas pressure of 100 Torr, a sample temperature of 800 ° C and a current of 135 A for 3 hours, and a filament temperature of 2000 ° C, A gas pressure of 100 Torr, a sample temperature of 700 캜, and a current of 125 A for 60 minutes.

[Example 8]

A diamond coating film was formed by using the insert having the same composition as that of Example 1 and subjected to the same polishing treatment, followed by dry blasting with alumina powder of # 240 mesh size at 1 bar pressure.

The diamond coating film according to Example 8 was prepared by coating a 1-step coating in which a coating was performed for 5 hours at a filament temperature of 2000 占 폚, a gas pressure of 30 Torr, a sample temperature of 750 占 폚 and a current of 145 占 폚 in a mixed gas atmosphere of 1% methane- A two-step coating was carried out in a mixed gas atmosphere of methane and hydrogen at a filament temperature of 2200 ° C, a gas pressure of 100 Torr, a sample temperature of 800 ° C and a current of 135 A for 5 hours and a filament temperature of 2000 ° C, A gas pressure of 100 Torr, a sample temperature of 700 캜, and a current of 125 A for 75 minutes.

[Example 9]

A diamond coating film was formed by using the insert having the same composition as that of Example 1 and subjected to the same polishing treatment, followed by dry blasting with alumina powder of # 240 mesh size at 1 bar pressure.

The diamond coating film according to Example 9 was formed in the same manner as in Example 9 except that the coating was carried out in a mixed gas atmosphere of 1% methane-hydrogen at a filament temperature of 2000 ° C, a gas pressure of 30 Torr, a sample temperature of 750 ° C and a current of 145 A for 6 hours, A two-step coating was carried out for 6 hours at a filament temperature of 2200 占 폚, a gas pressure of 100 Torr, a sample temperature of 800 占 폚 and a current of 135 占 폚 in a mixed gas atmosphere of hydrogen and a mixed gas of 5% methane and hydrogen at a filament temperature of 2000 占 폚 and a gas pressure of 100 Torr , A sample temperature of 700 ° C, and a current of 125 A for 90 minutes.

[Comparative Example 1]

The DLC coating film according to Comparative Example 1 was coated with the insert having the same composition as in Example 1 for 3 hours under the conditions of a coating temperature of 200 캜, a gas pressure of 3 mTorr, a bias voltage of 250 V, and a carbon target of 250 A using a filter arc ion plating method As shown in Fig.

[Comparative Example 2]

The diamond coating film according to Comparative Example 2 was subjected to the same polishing treatment with the same composition as in Example 1 and then subjected to the same polishing treatment in the same manner as in Example 1 except that a filament temperature of 2000 캜, a gas pressure of 20 Torr, a sample temperature of 900 캜 to 850 캜, 145A to 135A for 12 hours.

Of the coating film  Thickness and Raman peak intensity

The thickness of the coating film formed according to Examples 1 to 9 and Comparative Examples 1 and 2 of the present invention was measured and the diamond crystal structure of each coating film was confirmed using Raman spectroscopy. The results are shown in Table 1 below.

division No. Coating film
Kinds surface
process
system Coating film
thickness
(탆) Coating film
rescue Raman analysis peak intensity (rain) SP3 SP2 I
(SP3 / SP2) Comparative Example One DLC - 1.5 SP2 + SP3 One 2.67 0.37 2 Diamond Grinding 10.7 SP3 + SP2 One 0.13 7.69 Example One Diamond Grinding 1.8 SP3 + SP2 One 0.31 3.23 2 Diamond Grinding 3.2 SP3 + SP2 One 0.32 3.13 3 Diamond Grinding 4.8 SP3 + SP2 One 0.38 2.63 4 Diamond Mirror treatment 1.6 SP3 + SP2 One 0.43 2.33 5 Diamond Mirror treatment 4.2 SP3 + SP2 One 0.49 2.04 6 Diamond Mirror treatment 4.6 SP3 + SP2 One 0.56 1.79 7 Diamond Blasting 2.2 SP3 + SP2 One 0.47 2.13 8 Diamond Blasting 3.4 SP3 + SP2 One 0.56 1.79 9 Diamond Blasting 4.5 SP3 + SP2 One 0.94 1.06

Analysis of the thus-formed coating film by Raman spectroscopy revealed that the diamond specific (SP3) Raman peak exists at 1331 cm ^-1 and graphite specific Raman peak exists at 1580 cm ^-1 of graphite (SP2) .

As can be seen in Table 1, the coating layers according to Examples 1 to 9 of the present invention also include SP3 (diamond crystalline phase) and SP2 (diamond phase) similarly to Comparative Example 1 (DLC coating film) and Comparative Example 2 (conventional diamond coating film) (Graphite crystal phase) was found to be relatively increased with the SP2 peak intensity of about 0.31 to 0.65, unlike the diamond coating film according to Comparative Example 2 (SP2 peak intensity: 0.13). Accordingly, it can be seen that the Raman analysis peak intensity ratio (I, SP3 / SP2) is also in the range of 1 to 3.23.

That is, the diamond coating films according to Examples 1 to 9 of the present invention have a nucleation and crystal structure (I value, SP2 / SP3) different from that of the conventional diamond coating film through three steps of deposition.

Micro hardness  And coefficient of friction

(Load: 30 mN, Unload: 30 mN, Load time: 10 seconds, and 10 seconds) using a Fischer scope (HM2000; Germany HELMUT FISCHER GMBH, ISO 14577) for the coating films formed according to Examples 1 to 9 and Comparative Examples 1 and 2, The microhardness test was performed under the test conditions of Unload time: 10 seconds and Creep time: 5 seconds.

In addition, a ball-on-disc test was carried out using a CETR UMT-2 microtribometer (60% of Si ₃ N ₄ , diameter 4 mm, hardness HV _{50 g} 1600) The friction coefficient was measured by performing rotation with rotation, temperature: 20 to 25 DEG C, humidity: 50 to 60%, and rotation speed: 318 rpm (10 m / min).

The surface roughness (Ra) of each coating film was measured, and the particle size of the formed diamond coating film was measured by a scanning electron microscope.

As described above, all the coating films were formed on the base material made of cemented carbide of WC-6 to 8 wt% Co. However, in order to confirm the difference in surface roughness in the case of the coating films according to Examples 1 to 9 of the present invention, (Surface grinding method), mirror surface treatment method (polishing method), and blinking method (surface treatment by spraying Al ₂ O ₃ powder at 1 to 3 bar pressure with dry or wet pressure) And a coating film was formed.

Table 2 shows the results of measurement of microhardness, friction coefficient, surface roughness and diamond particle size (the size of the coating film when viewed from the plane) of the coating films according to Examples 1 to 9 and Comparative Examples 1 and 2 of the present invention will be.

division No. Coating film
Kinds Surface treatment
system Coating film
Hardness
(GPa) Coefficient of friction Surface roughness
(nm) Diamond
Particle size
(탆) Comparative Example One DLC - 33 0.04 26 - 2 Diamond - 72 0.26 457 5.8 Example One Diamond Grinding 51 0.11 204 1.8 2 Diamond Grinding 53 0.13 245 2.8 3 Diamond Grinding 56 0.15 237 2.4 4 Diamond Mirror treatment 42 0.07 78 0.6 5 Diamond Mirror treatment 46 0.08 74 0.9 6 Diamond Mirror treatment 48 0.11 94 1.2 7 Diamond Blasting 38 0.13 112 1.4 8 Diamond Blasting 43 0.14 134 1.4 9 Diamond Blasting 42 0.18 148 1.3

As shown in Table 2, the microhardness of the coating films according to Examples 1 to 9 of the present invention was 38 GPa to 56 GPa, and the hardness was improved as compared with Comparative Example 1 (DLC, 33 GPa). Comparative Example 2 Diamond coating, 72 GPa).

In the case of the surface roughness and the diamond particle size, it can be seen that the coating film according to Examples 1 to 9 of the present invention was lowered to a level of less than half that of Comparative Example 2. As a result, The diamond coating film according to Examples 1 to 9 exhibits a higher friction coefficient than the diamond coating film of Comparative Example 1, which is a DLC coating film, but is significantly lower than that of Comparative Example 2 which is a conventional diamond coating film.

3 is a scanning electron microscope (SEM) image of a coating film according to Comparative Example 1, Comparative Example 2 and Example 5 of the present invention. It is visually confirmed that the coating film according to Example 5 of the present invention has a medium surface roughness of Comparative Example 1 and Comparative Example 2 in conformity with the measured diamond particle size and surface roughness in Table 2. [

4 and 5 are SEM images of the coating film according to Comparative Example 1 and Example 5, respectively, enlarged at a magnification of 10,000 times, and FIG. 6 is a scanning electron micrograph (The red line in Fig. 6 represents the structure of the conventional diamond coating film, and the black line represents the structure of the coating film according to the embodiment of the present invention).

As can be seen from FIGS. 4 to 6, the coating films according to Comparative Examples 1 and 5 had a columnar structure, and in the case of Comparative Example 1, the columnar crystal grain size (width) was 1 to 2 Mu m, the coating film according to Example 5 of the present invention has a microstructure of about 1/3 of that of Comparative Example 1, with a columnar crystal grain size (width) of 0.3 to 0.65 mu m (average 1 mu m or less).

Through the control of such microstructure, it was confirmed that the coating films according to Examples 1 to 9 of the present invention had intermediate microstructure and hardness between the DLC coating film of Comparative Example 1 and the conventional diamond coating film of Comparative Example 2. [

Abrasion resistance evaluation

The cutting performance of the coating film having the above microstructure and hardness was evaluated. The cutting performance was evaluated by the milling cutting performance evaluation to evaluate the wear resistance. The specific evaluation conditions are as follows. Table 3 shows the results of the wear resistance evaluation.

Worked material: Aluminum alloy steel (AC8C (duralumin) milling)

Sample model number: APKT160408PDFR

Cutting speed: 300 m / min

Cutting feed: 0.3mm / rev

Cutting depth: ap = 10 mm, ae = 15 mm

Coolant: Dry machining

division No. Coating film
Kinds Surface treatment
system Cutting life
(min) Processing
Surface roughness
Ra (탆) Cutting life
Termination Cause Comparative Example One DLC - 10 0.54 Welding + chipping, abrasion 2 Diamond - 40 2.45 Normal wear Example One Diamond Grinding 35 1.14 Abrasive wear 2 Diamond Grinding 40 1.28 Normal wear 3 Diamond Grinding 40 1.26 Normal wear 4 Diamond Mirror treatment 35 0.81 Normal wear 5 Diamond Mirror treatment 40 0.92 Normal wear 6 Diamond Mirror treatment 40 0.97 Normal wear 7 Diamond Blasting 30 1.06 Excessive wear 8 Diamond Blasting 35 1.24 Abrasive wear 9 Diamond Blasting 35 1.22 Abrasive wear

As can be seen from the above Table 3, the cutting tool having diamond coatings according to Examples 1 to 9 of the present invention was inferior to the DLC coating of Comparative Example 1, It can be seen that the machined surface roughness Ra of the workpiece is remarkably lower than that of the formed cutting tool. In addition, it can be seen that the diamond coating film according to Examples 1 to 9 of the present invention can realize the roughness of the processed surface close to the DLC film when the mirror-like processing (Embodiment 4) is performed concurrently. Accordingly, the diamond coating film according to the present invention can be suitably used for cutting an aluminum alloy (duralumin).

In terms of cutting life, the coating films according to Examples 1 to 9 of the present invention show a lifetime of about 3 to 4 times as long as the DLC coating films, and such lifetimes are comparable to those of Comparative Examples 2 and 3 When compared, they are equal or slightly lower.

That is, the diamond coating film according to the present invention exhibits remarkably improved characteristics compared to the conventional diamond coating film in terms of the processed surface roughness of the workpiece, while maintaining almost the same level in terms of cutting life as compared with the conventional diamond coating film .

Claims (7)

delete delete delete delete (a) coating a cutting tool in a mixed gas atmosphere of hydrogen and 0.5 to 3% methane at a gas pressure of 10 to 30 Torr, a cutting tool temperature of 750 to 900 DEG C and a current of 140 to 150 A for 2 to 6 hours;
(b) coating the cutting tool at a gas pressure of 80 to 100 Torr in a mixed gas atmosphere of hydrogen and 3 to 10% methane, at a cutting tool temperature of 800 to 950 ° C, and at a current of 130 to 140 A for 2 to 6 hours; And
(c) coating the cutting tool with a gas pressure of 80 to 100 Torr in a mixed gas atmosphere of hydrogen and 3 to 10% methane at a cutting tool temperature of 700 to 850 ° C and a current of 120 to 130 A for 30 to 90 minutes; Diamond coating method. 6. The method of claim 5,
The diamond coating film formed by the coating method has a columnar structure,
Wherein the average primary particle size of the columnar primary particles is 1 mu m or less,
Wherein the Raman spectral peak intensity ratio (I (SP3 / SP2)) of graphite SP2 (1580 cm ^-1 ) and diamond SP3 (1331 cm ^-1 ) is 1 to 3.5. The method according to claim 5 or 6,
Wherein the cutting tool is subjected to a grinding treatment, a mirror-surface treatment or a blasting treatment before the step (a).

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