KR100576318B1 - A improvement method of surface roughness of diamond coating film to cutting tool - Google Patents

Abstract

The microcrystalline diamond cutting tool, which is artificially manufactured on a cemented carbide (WC-Co) base material by conventional chemical vapor deposition, is used for coarsening of crystal grains (3-15 μm) during processing. As a result, there is a problem in that the surface roughness of the workpiece is poor or the tool life is reduced. In order to solve this problem, a method of forming smoothed diamond is disclosed by coating a microcrystalline diamond as an intermediate layer to enhance adhesion, and subsequently miniaturizing the crystal grains of the diamond by harsh deposition conditions. That is, in order to improve the tool surface roughness of the workpiece according to the surface roughness of the diamond cutting tool by chemical vapor deposition method to improve the tool life, the mixed gas atmosphere that maintains the proper gas pressure of methane and hydrogen in the cemented carbide having a three-dimensional complex shape In the present invention, a coating film capable of characterizing a fine-crystalline diamond cutting tool formed by a hot-filament method is provided. As a result, the crystal grains of the microcrystalline diamond are very fine, about 30 to 100 nm. The surface roughness of the workpiece after cutting also showed very good results.

Description

A method of surface roughness of diamond coating film to cutting tool

The present invention relates to a method for improving the surface roughness of a diamond coating film for cutting tools, and more particularly, in order to improve the surface roughness of a workpiece in processing a workpiece such as aluminum-silicon alloy or magnesium alloy and graphite material, which is a non-ferrous metal. WC-Co) relates to a method of coating a diamond film composed of a very fine particle size on the base material.

In particular, the present invention relates to a method for producing a smoothed diamond-coated cemented carbide cutting tool to improve the surface roughness of the film by miniaturizing the crystal size of the growing diamond by harsh processing conditions, wherein the smoothed diamond film is a hot filament chemical vapor deposition method (HFCVD: hot). It relates to a method of coating diamond on cemented carbide using -filament chemical vapor deposition.

In general, the diamond coating cutting tool used commercially is produced by cutting a sintered body sintered by high temperature and high pressure into an appropriate size and welding it on a cemented carbide, and by dissolving and exciting a mixed gas containing carbon and coating it on a cemented carbide. There is a way. The former is excellent in tool performance, but the shape and size of the tool that can be welded in the manufacturing process is limited, there is a limit to the application to complex three-dimensional tools that require a variety of shapes. On the other hand, the coating film by the vapor phase method is somewhat inferior to the former, but has the advantage that it can be applied to three-dimensional complex shapes such as drills and end mills. However, the diamond film grown by the vapor phase method has a high coefficient of friction (μ,> 0.6) due to the coarsening of the crystal grains. Welding or chipping and peeling, which is a criterion for life, roughens the surface roughness of the workpiece and reduces the tool life. In order to improve / enhance this problem, the surface of the microcrystalline diamond cutting tool must be finely polished. However, it is not only very difficult to grind the edge portion of the three-dimensional cutting tool having a complicated shape, but also has a problem that the polishing cost is high even when applied to a simple two-dimensional cutting tool.

In order to improve the above problems, it is necessary to directly control the deposition or flattening of fine grain size particles directly on the cemented carbide substrate. Due to these needs, it has been manufactured by various chemical vapor deposition methods such as direct current, high frequency, hot filament, and microwave plasma on cemented carbide, but it has been used to manufacture reproducible microcrystalline diamond-coated cutting tools that have close adhesion in the process of commercialization. There are many difficulties. To this end, the diamond film composed of fine particles from the initial nucleation step results in a decrease in the adhesion life with the base material due to the high residual stress, which leads to a decrease in tool life. After synthesizing the diamond film to an appropriate thickness, the microcrystalline diamond film is continuously grown in harsh conditions to enhance adhesion to the base material and smooth the surface of the diamond film to smoothly discharge chips generated during cutting. Skill is required. In the US Patent Nos. 5989511 and 5772760 in connection with such a smoothed diamond film, a microcrystalline diamond film of about 15 to 50 nm is directly coated on a Si substrate using microwave plasma chemical vapor deposition (MPCVD). In addition, Patent Publication No. WO 0060137 under the name of Semecon Co., Ltd. discloses a method of forming a complex coating film as a multilayer structure in which the coating film has several layers.

As described above, in order to improve the surface roughness of the workpiece during cutting and to improve the life of the diamond cutting tool, after depositing microcrystalline diamond as an intermediate layer for improving the adhesion to the cemented carbide cutting tool, successively the appropriate thickness There is a need for a technique for synthesizing so-called smoothed diamond for coating a microcrystalline diamond film, i.e., a diamond coating method capable of effectively exerting a performance as a cutting tool without a complicated multilayer.

As mentioned above, the application of the welded diamond sintered body on the cemented carbide cutting tool has many problems such as the sintering / welding and polishing cost according to the three-dimensional complex shape, and the microcrystalline diamond film deposited by the vapor phase method Due to the rough / non-smooth surface characteristic, the workability of the workpiece is degraded due to the deposition of fine workpiece sludge between the diamond particles.

The present invention has been made to solve the above-mentioned problems, and is applicable to complex shapes, and a method for producing a smoothed diamond-coated cutting tool having improved surface roughness of a conventional diamond film so as to suppress welding of the workpiece with fine sludge. The purpose is to provide. The present invention is applied to the filament CVD method, synthesized in the composite structure of the intermediate layer and the microcrystalline diamond film consisting of about 30 ~ 100nm size of diamond crystal particles thereon, XRD (X-ray diffractometer) and Visible (514.5nm) ) Raman spectroscopy and scanning electron microscopy (SEM) confirmed that the diamond.

The cutting tool manufactured through the present invention is particularly suitable for the automotive industry, which requires machining precision by improving the surface roughness of the workpiece and improving tool life in cutting non-ferrous metals such as aluminum-silicon and brass and graphite, wood, etc. It can be usefully used in the semiconductor, electronics industry.

The present invention relates to a method for producing a smoothed diamond cutting tool with improved surface roughness to solve the above problems and its characteristics, the microcrystal having a size of diamond crystal grains of 1 ~ 10㎛ using the hot filament CVD method The diamond film is coated with an intermediate layer, thereby continuously coating a microcrystalline diamond film having a size of about 30 to 100 nm of diamond crystal grains thereon to improve surface roughness.

Specifically, a microcrystalline diamond film having a size of diamond crystal grains of 1 to 10 μm is coated on the cemented carbide (WC-Co) base material after Co treatment with an intermediate layer, and then about 30 to A 100 nm fine crystalline diamond film was deposited to smooth the surface of the diamond film during the process. The smoothed diamond obtained by this step coating method can maintain the adhesion with the base material and improve the surface roughness, thereby improving the tool life due to the increased wear resistance of the cutting tool and the lubrication effect due to the low friction coefficient. .

In order to achieve the object of the present invention as described above, the present invention is pretreated with a WC-Co-based cemented carbide as a base material and then coated with a microcrystalline diamond film having a high modulus of elasticity as an intermediate layer. It provides a diamond coating film for cutting tools characterized in that the coating.

Here, the intermediate layer coating is performed in a mixed gas atmosphere of methane (CH ₄ ) -hydrogen (H ₂ ), the ratio of methane amount is 0.2 ~ 1%, gas pressure 10 ~ 30 Torr, the microcrystalline diamond film coating is the amount of methane It is preferable to perform at the ratio of 3 to 10% and gas pressure of 50 to 100 Torr. The intermediate layer is microcrystalline diamond, grown in 1% or less of methane and 99% or more of hydrogen atmosphere, because the high hydrogen content allows the growth of pure diamond crystals by etching the non-diamond phase.

In addition, the thickness ratio (b / a) of the microcrystalline diamond film (b) to the intermediate layer (a) is preferably 2.0 to 4.0, wherein the thickness of the intermediate layer is 3.0 to 6.0㎛, the microcrystalline diamond It is preferable to make the film thickness into 8-15 micrometers.

In addition, the microcrystalline particles of the intermediate layer is 1 ~ 10㎛, the microcrystalline diamond film crystal grains may be 30 ~ 100nm, the surface roughness of the microcrystalline diamond film is to be Rmax = 10 ~ 100nm good.

Hereinafter, the present invention will be described in more detail.

According to the present invention, after pretreatment by a chemical method using a cemented carbide as a base material, a smoothed diamond film is manufactured by continuously changing process conditions. The cemented carbide used as the base material has a WC particle size in the range of about 0.5 to 5 μm and a Co content of 6 wt% or less. The greatest feature of the present invention is that as an intermediate layer, microcrystalline diamond having a larger elastic modulus than the base material and having a diamond grain size of about 1 to 10 μm is deposited to an appropriate thickness of a columnar structure to improve adhesion to the base material. By successively varying the process conditions, microcrystalline diamond having a homogeneous phase of about 30 to 100 nm in size is deposited on the microcrystalline diamond film, thereby increasing the surface area of the diamond particles to improve the bonding strength between the particles and the surface. The tool life is improved by improving the roughness. In addition, since the smoothed diamond film is composed of fine crystal grains, the friction coefficient exhibits very low lubrication characteristics. That is, the high elastic modulus of the microcrystalline diamond film in contact with the base material prevents cracking of the thin film, and the lubrication effect can be obtained due to the low coefficient of friction of the microcrystalline diamond film. Therefore, the tool life is longer than that of the conventional microcrystalline diamond cutting tool. Can improve.

In the present invention, the intermediate layer is carried out at a mixed gas atmosphere of methane (CH ₄ ) -hydrogen (H ₂ ) at a ratio of 0.2-1% of methane and a gas pressure of 10-30 Torr, and the microcrystalline diamond coating has a ratio of methane of 3-10. %, At a gas pressure of 50 to 100 Torr.

The thickness of the intermediate | middle layer of this invention is 3-4 micrometers, and the thickness of a microcrystal diamond film is 8-12 micrometers. That is, the thickness ratio of the microcrystalline diamond film to the intermediate layer is preferably about 2.0 to 4.0. The total film thickness of the smoothed diamond shall be about 11-16 micrometers. In addition, the crystal grain size of the microcrystal and the microcrystalline diamond film is about 1 to 10 mu m and 30 to 100 nm, respectively.

In addition, as a result of non-diamond component analysis by Visible Raman spectroscopy, the film obtained under the step deposition conditions showed sp ² bonding structure of CH at about 1144 and 1483 cm ^-1 , sp ³ bonding structure of diamond at 1333 cm ^-1 and 1350 has a structure of sp ² bonded graphite (G band) at about ~ 1364㎝ and 1540 disorder (D band) in the vicinity of ^-1 ~ 1550㎝ ^-1. In addition, as a result of analysis by X-ray diffraction (XRD) to confirm the presence of the crystal plane, the peak of the (111) plane was detected at about 43.98 (2θ) to confirm that the diamond of the microstructure.

Comparative Example

As shown in Table 1 below, three samples of the present invention were prepared. The preparation method of these samples is as follows.

First, as shown in Table 1, in the intermediate layer, the ratio of methane in the mixed gas atmosphere of methane (CH ₄ ) -hydrogen (H ₂ ) is 0.2-1%, the gas pressure is 10-30 Torr, and the microcrystalline diamond film is methane. The ratio of 3 to 10%, the gas pressure was changed to 50 ~ 100 Torr and deposited under the same conditions. As the base material, model number SPCN1203EDR for milling was used. In addition, the workpiece is AC8A, a kind of aluminum alloy, which has a Si content of about 11 to 13%, and its hardness and melting point are very low. It is an appropriate workpiece that is good for judging. In the case of cutting with practically uncoated cemented carbide, the cutting edge of the cutting tip at the initial stage generates chipping and peeling phenomenon due to welding, which roughens the surface roughness of the workpiece. However, the smoothing diamond cutting tool according to the present invention suppresses this welding phenomenon as much as possible to improve the surface roughness of the workpiece. Table 2 shows the results of evaluating the cutting performance under the cutting conditions as shown in (A) below.

(A) Abrasion resistance test (dry processing)

Workpiece: AC8A (11 ~ 13% Si, 120㎜ 200㎜ 300㎜)

Cutting speed: 800 (m / min)

Feeding amount: 0.15 (㎜ / rev)

Depth of cut: 2 (mm)

Cutting distance: 1, 50, 100 (pass, cutting distance (mm): 1pass = 300mm)

Cutting Tip Shape: SPCN1203EDR

Tool evaluation was carried out after 1, 50, 100 pass to confirm the welding and peeling around the edge, and measured the surface roughness (Rmax), the results are shown in Table 2. The smoothed diamond cutting tool produced by the present invention shows excellent cutting performance compared to the comparative sample.

Table 1.

Table 2.

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As described above, in the severe stepwise process conditions, the thickness of the intermediate layer is in the range of about 3 to 6 μm, and the crystal grains are coated in about 1 to 10 μm, and then the thickness of the microcrystalline diamond film is about 8 to 15. It was possible to improve the tool life and surface roughness over the conventional microcrystalline diamond cutting tool by depositing the size of the crystal grains in the range of 탆 and about 30 to 100 nm. That is, depositing a thickness ratio of the microcrystalline diamond film to the intermediate layer at about 2.0 to 4.0 showed excellent cutting characteristics in performance evaluation. It is difficult to manufacture high-quality process / high quality products due to the roughness of the surface of the conventional workpiece and the cutting resistance due to unsatisfactory chip discharge due to the roughness of the surface of the cutting tool itself. It is possible to solve the problem.

Although described above through the preferred embodiment of the present invention, those skilled in the art can understand that the present invention can be variously changed and modified within the spirit and scope of the invention described in the claims below. There will be.

Claims (5)

In the method of improving the surface roughness of the diamond coating film for cutting tools, After cobalt (Co) removal treatment using a WC-Co cemented carbide as a base material, a microcrystalline diamond film having a crystal grain size of 1 to 10 µm and having an elastic modulus larger than that of the base material was coated with an intermediate layer (a), and the frictional force was applied. In order to reduce the thickness, a microcrystalline diamond film having a crystal grain size of 30 to 100 nm is coated with the outermost layer (b), and the film thickness ratio (b / a) of the outermost layer (b) to the intermediate layer (a). Method of forming a diamond coating film for a cutting tool, characterized in that 2.0 to 4.0. delete The method of claim 1, wherein the intermediate layer has a thickness of 3 to 4 μm, and the microcrystalline diamond film has a thickness of 8 to 12 μm. delete The method of claim 1, wherein the surface roughness of the microcrystalline diamond film is Rmax = 10 ~ 100nm.