KR20040057559A - A deposition method of coating film with fine-crystalline diamond to cutting tool - Google Patents

Abstract

PURPOSE: A method for forming a film having fine crystalline diamond characteristics on the matrix by methane-hydrogen based microwave plasma by setting the matrix to be treated on a substrate holder geometrically designed using an insert used as cutting tool as a matrix is provided. CONSTITUTION: The method comprises a step of positioning a matrix(200) on a substrate holder(100) on which groove(110) is formed; and a step of generating methane-hydrogen based microwave plasma(300), and constantly maintaining a distance between the matrix and the plasma so that a film having fine crystalline diamond characteristics is formed on the matrix, wherein the matrix is exposed to a position that is 2 to 3 mm above the surface of the substrate holder, and the distance between the surface of the matrix and the plasma is 2 to 10 mm, wherein the matrix is a WC based hard metal insert comprising 3 to 10 wt.% of Co and 10 wt.% or less of other carbide, wherein the matrix is a WC based hard metal having an average particle size of 0.5 to 6 μm, wherein the plasma is generated by coaxial or cavity type microwave power supply and other microwave power supply, and a plasma source used is a mixed gas of methane and hydrogen or a mixed gas of methane, hydrogen and carbon, and wherein the film formed has crystal grain size of 5 to 500 nm, thickness of 0.5 to 15 μm, surface roughness Ra of 5 to 40 nm and hardness of 80 to 120 GPa.

Description

A deposition method of coating film with fine-crystalline diamond to cutting tool

The present invention relates to a method for producing a microcrystalline diamond coated cutting tool, and more particularly, to a method for forming a diamond characteristic film of an insert, in particular a milling insert.

Diamond is one of the hardest materials in the world. Today, the diamond cutting tools artificially produced by the gas phase synthesis method are used as the best tools for machining difficult-to-machine, aluminum-silicon alloys, magnesium alloys and graphite materials. In general, a diamond coating film is manufactured by chemical vapor deposition (CVD) which is converted into plasma or thermal energy by various power sources (direct current, alternating current, high frequency, microwave) in a mixed gas atmosphere including hydrocarbons. Hot filament method, combustion flame, dc glow discharge plasma, arc glow discharge plasma jet, microwave plasma method, etc. have. Among them, the cemented carbide cutting tool is mainly applied by thermal filament coating, and the diamond film is made of polycrystalline diamond composed of coarse crystal size of about 5 to 15 µm. It is precipitated into columnar columnar structure from the surface and is very rough. The cemented carbide diamond cutting tool composed / manufactured by such coarse crystal size lowers the surface roughness of the workpiece during processing, thereby lowering the machining precision. In addition, since the coefficient of friction (μ,> 0.6) of the microcrystalline diamond is high, welding of the fine particles of the workpiece between the diamond particles and the particles during cutting causes a decrease in the life of the tool. To solve this problem, the surface of the microcrystalline diamond film must be finely and smoothly polished. However, since the cemented carbide cutting tool has a three-dimensional complex shape, it is very difficult to polish the cutting edge, and the polishing cost is high. In addition, as another method, a diamond sintered insert is used for brazing a diamond cutting tool. However, a drill and an end mill having a complicated shape are scattered with problems of manufacturing method and difficulty of lighting having high manufacturing cost.

In order to solve the surface roughness of the microcrystalline diamond film produced by the vapor deposition method, which is the above problem, the basic research on the microcrystalline diamond film coating has been published as some papers and patents by several methods. According to published papers and patents, most of them are examples of fabricating microcrystalline diamonds of about 15 to 50 nm in Si wafers. Most of the manufacturing methods include microwave plasma chemical vapor deposition (Microwave Plasma CVD), using a high concentration of methane gas in the methane-hydrogen mixture gas, a method using argon or C60-hydrogen-methane, direct current bias on the base metal. And a method of applying a voltage. In another method, the thermal filament method, by using a mixed gas of hydrogen-methane, the substrate temperature is reduced (1250 ° C. => 1020 ° C.) at a high gas pressure (about 200 Torr) to obtain a fine crystal size of about 8 to 16 nm. It is reported that diamonds have been deposited. However, no practical application has been reported for cutting tools, which are cemented carbide, and no evaluation method has been reported for the prepared microcrystalline diamond film cutting tools. The reason for this is that the synthesis conditions of the microcrystalline diamond film are very severe and the precise synthesis mechanism for the microcrystalline diamond due to coarsening due to the growth of the crystal grains during long time deposition has not yet been identified.

As described above, the method for producing a microcrystalline diamond film using a microwave plasma chemical vapor deposition method or a hot filament method on a conventional Si wafer is applied to a microwave power source in a mixed gas atmosphere containing a high gas pressure methane-hydrogen-argon gas of 100 Torr or more. A plasma was generated to excite the gas while suppressing ionization to synthesize a microcrystalline diamond film on the base material. As a result, it is possible to partially grow on a two-dimensional flat base material, but in the case of applying to a cemented carbide cutting tool having a three-dimensional complex shape, the uniformity or adhesion of crystal grain size / film thickness is a problem. In addition, even in the physical property evaluation of the film, it is difficult to take a large cost and time to accurately identify or evaluate the microcrystalline diamond.

As described above, in the case of cutting, in order to improve the surface roughness of the workpiece and to produce a high-speed cutting, by producing microcrystalline diamond directly on the cemented carbide cutting tool, the particle size of the diamond is not finely adjusted or mechanical external force is applied. In the range, it is necessary to adjust the surface of the diamond film smoothly / smoothly. The cemented carbide used as a cutting tool is composed of a mixture of tungsten carbide (WC) and cobalt (Co), and in the coating of diamond, graphite component, which is a non-diamond phase, is precipitated by Co, a binder phase present between the WC particles and the particles. This reduces the adhesion between the cemented carbide and the thin film.

Korean Patent Laid-Open Publication No. 2000-34774 discloses a diamond-coated cutting tool, but the patent discloses a method of coating diamond on a long rotary cutting tool such as a drill, an end mill or a reamer.

The present invention is to solve the above problems, an object of the present invention is to insert a three-dimensional composite cemented carbide substrate, particularly inserts used as a cutting tool for improving the surface roughness and high-speed cutting performance of the workpiece that is a problem during cutting The present invention provides a method for forming a microcrystalline diamond characteristic film by methane-hydrogen-based microwave plasma by setting a base material to be treated in a geometrically designed substrate holder.

Thus, the film formed by the present invention was characterized by Visible (514.5 nm) and UV (ultraviolet, 244 nm) Raman spectroscopy and nanoindentor, and the coating film was diamond.

Figure 1a is a placement method of cemented carbide base material seen from the top

Figure 1b is a front view of a conventional cemented carbide setting method

Figure 1c is a front view of the cemented carbide setting method of the present invention

Figure 2a is a surface photograph of the diamond characteristic film formed of methane-hydrogen plasma in the conventional setting method

Figure 2b is a surface photograph of the diamond characteristic film formed of methane-hydrogen-argon-based plasma in a conventional setting method

Figure 2c is a surface photograph of the diamond characteristic film formed of methane-hydrogen plasma in the setting method of the present invention

Figure 3a is a photograph of the surface shape by AFM of the diamond feature film formed by the present invention

Figure 3b is a surface roughness photograph by the AFM of the diamond feature film formed by the present invention

Figure 4 is a microhardness distribution graph of the nano-indenter (nanoindentor) of the microcrystalline diamond characteristic film according to the present invention

5 is a graph of analysis results by Visible (514.5 nm) and UV (244 nm) Raman spectroscopy of the microcrystalline diamond characteristic film according to the present invention.

<Explanation of symbols for the main parts of the drawings>

100: substrate holder 200: the base material

300: plasma

In order to achieve the object of the present invention as described above, the present invention, after placing the base material in a substrate holder formed with a suitable groove for inserting the base material, in particular, cemented carbide insert having a three-dimensional shape, and then the methane-hydrogen microwave plasma Provided is a method of forming a coating film having generated and deposited microcrystalline diamond characteristics on a base material. Here, the methane-hydrogen mixed gas is used as the plasma source, and the content thereof may be 10% methane-90% hydrogen.

In the above, the base material is preferably exposed to the upper surface of the substrate holder about 2 ~ 3mm, the distance between the surface of the base material and the plasma is about 2 ~ 10mm to keep the base surface and the contact portion of the plasma close / uniform. desirable.

In addition, the base material is a cemented carbide insert, in particular, its composition is preferably used WC-based cemented carbide inserts containing 3 ~ 10wt% Co and less than 10wt% tar carbide, the average particle size of the base material is 0.5 ~ 6㎛ WC It is recommended to use cemented carbide.

In addition, the generation method of the plasma source is preferably a coaxial or cavity-type microwave power source and a synthesis method using other microwave power sources. The plasma source used is a mixed gas of methane-hydrogen or the like. It is preferable to use a mixed gas containing carbon.

In addition, the crystal grain size of the coated film is preferably 5 to 500nm, 0.5 to 15㎛ thickness, surface roughness is Ra = 5 to 40nm, hardness 80 ~ 120GPa.

In addition, the Visible Raman spectroscopy is approximately 1140 and the diamond in the CH bond of the sp ² structure, 1333cm ^-1 1480cm ^-1 in the sp ³ bonding structure, and at 1355 and 1540cm ^-1 display order (disorder) and graphite (G band) a it has an sp ² bond structure, in particular, UV (ultraviolet) Raman spectroscopy of the graphite having an sp ² bond structure in the slightly sharp peak of about 1580cm ^-1 and the periphery of the diamond having an sp ³ bond structure in the vicinity of about 1333cm ^-1 It is desirable to obtain a broad peak.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.

Unlike the conventional method of forming a microcrystalline diamond characteristic film, the present invention generates plasma by setting a base material in the substrate holder 100, and inserts the base material into the groove 110 formed on the holder 100. After maintaining the plasma shape stably by bringing the distance to the substrate (5 ~ 10mm) closest to each other, a 90-110 GPa microcrystalline diamond characteristic film close to the hardness of natural diamond was formed by the methane-hydrogen mixed gas. The coating film obtained by using the Visible (514.5nm) and UV (244nm) Raman spectroscopy and nanointensifiers were evaluated for the characteristics showed a hardness close to natural diamond.

According to the present invention, the non-uniform temperature distribution of the conventional base material is solved by setting the base material 200 to be coated on the same line as the height of the substrate holder. By concentrating the plasma, the conventional problem that the crystal grains grow coarse or the film grows rapidly due to the temperature difference of about 50 ° C. with the central portion of the insert, which is the base metal, solves the conventional problem.

Comparative Example 1

This embodiment is a substrate (100) of a cemented carbide (WC-6% Co) having a three-dimensional complex shape of 16 * 8 * 5 (thickness) mm ^{3 in} the substrate holder 100 by a conventional method (APKT1604PDFR-MA) 200 1B was set in the substrate holder 100 and then coated with a base material temperature of 750-850 ° C. for 10 hours in a methane-hydrogen mixed gas atmosphere with a gas pressure of 20-40 Torr. As a result, the size of the crystal grains of the obtained film was about 2 ~ 5㎛, XRD analysis showed peaks of diamond (111), (200), (311) plane, Visible Raman spectroscopic analysis of about 1333cm ^-1 Sharp peaks were obtained showing relatively good crystallinity of the diamond. However, when looking at the thickness of the obtained film, it is obtained relatively uniformly on the upper surface, but is thinly coated on the side surface than the cutting edge and the upper surface, and the size of crystal grains is also different. This is because the distribution of the plasma is concentrated at the edge portion at the portion where the plasma and the upper surface of the base contact each other. As a result, the nucleation and growth rate of the diamond are different because the temperature distribution of the base is different.

Comparative Example 2

This embodiment is a substrate (100) of a cemented carbide (WC-6% Co) having a three-dimensional complex shape of 16 * 8 * 5 (thickness) mm ^{3 in} the substrate holder 100 by a conventional method (APKT1604PDFR-MA) 200 1b was set in the substrate holder 100 and then coated in a mixed gas atmosphere of methane-hydrogen-argon with a gas pressure of 20 to 40 Torr for 10 hours at a substrate temperature of 750 to 850 ° C. As a result, the size of the crystal grains of the obtained film was about 2 to 4 µm and initially grown as a film having a crystal size of about 500 to 700 nm, but after some growth, it was grown to an island shape instead of the film. XRD analysis result of diamond 111, 220, 311 was the peak of the surface-detecting, Visible (514.5nm) of the graphite in the Raman spectroscopy results sp ³ structure and 1580cm ^-1 of diamond at about 1333cm ^-1 sp ² Weak broad peaks in the structure could be observed. This method is very difficult to control the plasma between the gas pressure of 20 to 50 Torr by the introduction of argon gas, which is very unstable. In addition, the surface of the grown diamond film was observed to be sputtered by argon ions, resulting in damage to the crystal grains.

Example 3

In the embodiment of the present invention, setting of the base material (APKT1604PDFR-MA) 200 which is a cemented carbide (WC-6% Co) having a three-dimensional complex shape of 16 * 8 * 5 (thickness) mm ^{3 in} the substrate holder 100. The method was made different from Comparative Examples 1 and 2. That is, the surface which contact | connects the plasma 300 and the base material 200 was made as flat as possible. As seen from the front of FIG. 1C, the groove 110 is formed to have a depth enough to enter the lower end (about 3 mm) of the base material 200 so that only the top surface of the base material 200 is about 2 mm from the surface of the substrate holder 100. Exposed or raised. By doing so, when the base material 200 and the plasma 300 are in contact with each other, the shape distribution of the plasma 300 can be uniformly adjusted, thereby reducing the temperature difference on the surface of the base material 200 by the plasma 300, which is possible. Particle growth of diamond proceeds uniformly at one top, edge and side. As a result, the nucleation and growth of diamond are uniformly controlled by reducing the difference in temperature distribution in the base material 200 as much as possible.

Experimental Conditions of Examples

Gas pressure 20 to 40 Torr, mixed gas of methane-hydrogen, coating time 10 hours, substrate temperature 750 to 850 ° C, microwave power 1 to 2 kW, distance between upper surface of substrate and plasma 5 to 10 mm

Property evaluation result

Rating 1

In Example 3, the obtained film had a particle size of 5 to 25 nm, a surface roughness of Ra = 20 to 40 nm, and XRD analysis showed that polycrystalline fine diamonds of diamonds 111, 220, and 311 were obtained. As a result, no peeling occurred when indented under a load of 60 kg. In addition, as shown in Figure 4, the microhardness measurement results (three measurements) by the nano-intensors showed a very high hardness of about 90-110GPa.

Evaluation 2

In Example 3, the Visible (514.5 nm) and UV (244 nm) Raman spectroscopy of the obtained film as a result of Raman spectroscopy, as shown in FIG. 5, stretching vibration of CH around 1140 and 1480 cm ^-1 in Visible Raman spectroscopy. mode which was the Raman shift of the sp ² structure, indicates a sp ³ bonding structure, about 1355 and sp ² bond structure called at 1540cm ^-1 in the so-called disorder (D band) and graphite (G band) of the diamond at 1333cm ^-1. Furthermore, the sp ³ more sensitive UV Raman spectroscopy of carbon bonded structure a broad peak at about 1580cm ^-1 and slightly sharp peak of diamond at about 1333cm ^-1 around the vicinity of graphite were observed. Here, the graphite peak around 1580 cm ^-1 is caused by sp ² carbon present at the interface between the many crystal grains and the particles constituting the film.

As described above, by designing the upper surface of the cemented carbide base material as closely as possible to the substrate holder as possible, the upper surface portion of the base material and the plasma is adjusted so as to be in close contact with the most uniformly, very high of about 90 to 110 GPa. It is possible to form a film on the cemented carbide with a fine crystal diamond characteristic having a hardness and a crystal size of about 5 to 25 nm.

Therefore, the nonuniform temperature distribution of the base material, which has been a conventional problem, is solved, and thus it is possible to prevent the peeling phenomenon of the film due to the coarse grain growth or the rapid growth of the film.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art various modifications and changes to the present invention without departing from the spirit and scope of the invention described in the utility model registration claims I can understand that you can.

Claims (7)

In the method of forming a microcrystalline diamond characteristic film on a base material, the base material is placed in a grooved substrate holder, followed by deposition by generating a methane-hydrogen microwave plasma to maintain a constant distance between the base material and the plasma. A method of forming a microcrystalline diamond characteristic film on a base material. The method of claim 1, wherein the base material is exposed to the top of the substrate holder 2 to 3mm, and the distance between the surface of the base material and the plasma is 2 to 10mm. The method of claim 2, wherein the base material is a cemented carbide insert, the composition is a WC-based cemented carbide insert containing 3 to 10wt% Co and less than 10wt% tar carbide. 4. The method of claim 3, wherein the average particle size of the base material is a WC-based cemented carbide of 0.5 to 6 [mu] m. The method of claim 1, wherein the generation of the plasma source is a synthesizing method using a coaxial or cavity type microwave power source and other microwave power sources, and a plasma source to be used is a mixed gas of methane-hydrogen or its A method of forming a microcrystalline diamond characteristic film on a base material, characterized in that the mixed gas containing an external carbon. The microcrystalline diamond characteristic film of claim 1, wherein the film is formed with a crystal grain size of 5 to 500 nm, a thickness of 0.5 to 15 μm, a surface roughness of Ra = 5 to 40 nm, and a hardness of 80 to 120 GPa. How to let. 7. The method of claim 6 wherein the film Visible Raman CH in about 1140 and 1480㎝ ^-1 spectral sp ² bond structure, the diamond sp ³ bonding structure in 1333㎝ ^-1, and 1355 in display order and 1540㎝ ^-1 (disorder) (D band) and graphite (G band) of sp ² bond structure has a, UV (ultraviolet) slightly sharp peak of diamond having an sp ³ bond structure in the vicinity of about 1333cm ^-1 in Raman spectroscopy and about 1580cm ^- A method of forming a microcrystalline diamond characteristic film on a base material, characterized in that a broad peak of graphite having a sp ² bonding structure is obtained around ¹ .