JPH06320304A - Diamond cutting tool excellent in welding resistance and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a diamond cutting tool, wherein a good cut surface can be formed by preventing welding from its generation in a cutting face of the cutting tool, and a method for manufacturing the cutting tool thus constructed. CONSTITUTION:In a diamond cutting tool wherein at least a cutting action part of the cutting tool is constituted of a polycrystalline diamond film, a surface of the polycrystalline diamond film corresponding to at least a cutting face of the cutting action part is coated with a boron nitride film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diamond cutting tool applicable to the cutting of non-ferrous metals, especially finishing, and a method for producing the same, and particularly to a diamond cutting tool exhibiting excellent welding resistance during cutting, and It relates to a method for manufacturing such a cutting tool.

[0002]

2. Description of the Related Art Diamond has extremely high hardness as compared with alumina, silicon nitride, tungsten carbide, etc., which have been conventionally used as hard materials, and has high thermal conductivity. Therefore, diamond is applied to cutting tools. Development is actively done.

As a tool to which diamond is applied, a tool (sintered diamond tool) using a polycrystalline diamond sintered body synthesized by sintering fine diamond powder at high temperature and high pressure has been developed. Widely used as a cutting tool.

On the other hand, since the vapor phase synthesis method of diamond was established, it may be easily and inexpensively applied to tools having complicated shapes. Development of tools in which the surface of the tool base material is coated with a diamond film is also active.

By the way, when non-ferrous metal is finished by using the above-mentioned tools, not only the sharpness of the cutting edge but also the chips separated and discharged from the work material by the cutting work are struck on the rake face of the tool. It is also necessary that they are not welded, that is, have excellent resistance to welding. The above-mentioned deposits fall off from the tool rake face and adhere to the surface of the work material, or form a cutting edge to cause a decrease in the surface roughness of the work material.

In order to prevent such welding, the sintered diamond tool has been devised so that the tool rake surface is mirror-finished to improve the slip of chips. This polishing is usually carried out by a skiffing machine, but as described above, diamond has the highest hardness, so that there is a drawback in that polishing takes a long time. Further, even if the rake face is a mirror surface, welding cannot be prevented depending on the cutting conditions, and there is a problem that the cutting conditions are limited.

On the other hand, the polycrystalline diamond film formed by vapor phase synthesis has a surface with a grain size of 0.5 μm to several μm.
Since it is composed of diamond grains of m, it is rough, and if it is used for cutting as it is, it causes welding and it is difficult to obtain a good cut surface roughness. Therefore, like the sintered diamond tool, it is possible to polish the surface of the film, but the polycrystalline diamond film obtained by vapor phase synthesis differs from sintered diamond in that it does not contain metal binder and is close to 100% diamond. Being composed of grains, it is very hard and not easy to polish.

Therefore, as a method of improving the surface roughness of the polycrystalline diamond film, a technique disclosed in, for example, Japanese Patent Laid-Open No. 1-212767 has been proposed. This technique involves depositing a polycrystalline diamond film on a substrate having a surface roughness Rmax of 0.1 μm or less by a vapor phase synthesis method, temporarily removing the produced diamond film from the substrate and cutting it into a cutting edge shape. The diamond film is attached to the cutting action part of the tool base material by brazing so that the bonded surface side of the film to the tool rake surface, and the substrate is removed from the polycrystalline diamond film before or after this brazing. The surface roughness of the surface is Rmax of 0.
It is to be 1 μm or less. However, in order to deposit diamond on the substrate, it is necessary to make a fine scratch on the substrate, which is the starting point of diamond nucleation, with diamond powder in advance, so that the surface roughness of the substrate is set to Rmax of 0.1 μm or less. It is extremely difficult to do. If the rake surface roughness is Rmax of 0.1 μm
Even if it can be done below, it is not enough to prevent welding, and similar to the sintered diamond cutting tool, welding occurs depending on the cutting conditions, and good surface roughness cannot be obtained. was there.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to prevent welding of a rake face of a cutting tool and to form a good work surface. It is to provide a diamond cutting tool that can do, and a method for manufacturing such a cutting tool.

[0010]

Means for Solving the Problems The present invention which has achieved the above object is a diamond cutting tool in which at least a cutting action portion of the cutting tool is composed of polycrystalline diamond, and at least a rake face of the cutting action portion is provided. The gist is that the surface of the corresponding polycrystalline diamond film is covered with the boron nitride film.

[0011]

The present inventors paid attention to the affinity between the work material and the tool rake face in order to improve the weldability, and studied from various angles. As a result, if the surface of the polycrystalline diamond film corresponding to at least the rake face of the cutting action portion is covered with a boron nitride film having a low affinity with the work material, the occurrence of welding can be prevented, which is good. It was found that the surface roughness to be machined was obtained, and the present invention was completed. As described above, the diamond cutting tool of the present invention is one in which at least the surface of the polycrystalline diamond film corresponding to the rake face is covered with the boron nitride film. This is because it may be covered with a boron film. However,
The boron nitride film coated on the scaly surface side is gradually removed during cutting, and as a result, polycrystalline diamond is exposed on the scaly surface side, and the original function of the diamond cutting tool is exhibited.

The diamond cutting tool of the present invention is formed by coating the surface of the polycrystalline diamond film corresponding to at least the rake face of the cutting action portion with the boron nitride film as described above. The thickness of the boron film is preferably 0.05 to 3 μm. That is, if the film thickness is less than 0.05 μm, the film becomes non-uniform and the rake face is not completely covered with the boron nitride film, and a sufficient effect cannot be obtained. On the other hand, if the film thickness exceeds 3 μm, the boron nitride film is likely to be chipped in a shell shape from the cutting edge, which rather deteriorates the surface roughness of the work material.

The surface roughness of the rake face of the diamond cutting tool coated with the boron nitride film is preferably Rmax of 1 μm or less. If the surface roughness is higher than this, chips discharged by sliding on the rake surface due to the unevenness of the surface are scraped off, and this remains on the rake surface, causing welding to occur.

The boron nitride film preferably contains 70% by volume or more of cubic boron nitride. Boron nitride includes hexagonal crystals and amorphous ones in addition to cubic crystals, but has a lower hardness than cubic crystals. If the content of cubic boron nitride in the boron nitride film is less than 70% by volume, the rake face is heavily worn by chips and the underlying diamond surface is exposed, and welding begins to occur during cutting, resulting in a rough surface to be machined. Cause a decline.

The cubic boron nitride contained in the boron nitride film preferably has a grain size of 0.01 to 2 μm. That is,
If the particle size of the cubic boron nitride is less than 0.01 μm, the wear of the film becomes severe and the effect of the present invention cannot be obtained. On the other hand, when the grain size of the cubic boron nitride exceeds 2 μm, the grains of the cubic boron nitride start to drop off from the edge of the blade by chipping, and the underlying polycrystalline diamond is exposed, so that the effect of the present invention cannot be obtained.

In the present invention, as a method for forming the boron nitride film, a low pressure vapor phase synthesis method utilizing a non-equilibrium state may be adopted. Examples of such a method include a physical vapor deposition method (PVD method) such as an ion plating method and an ion beam method, and a chemical vapor deposition method (CVD method) such as an RF plasma CVD method and a microwave plasma CVD method. However, any method can be adopted as long as the boron nitride film can be synthesized.

As the diamond cutting tool coated with the boron nitride film in the present invention, either a sintered diamond cutting tool or a vapor phase synthetic diamond cutting tool can be adopted. In particular, for vapor phase synthetic diamond cutting tools, a diamond cutting tool in which diamond is directly deposited on the surface of the cutting tool base material, and after depositing a polycrystalline diamond film on the substrate, the polycrystalline diamond film is raked on the substrate surface side. It can be used for a so-called brazing tool in which a base material is attached to a tool base material by brazing so that the substrate is removed before or after the brazing so as to be bladed.

The boron nitride film is directly coated on the diamond cutting tool by the above-mentioned method, but the vapor-phase synthetic polycrystalline diamond brazing cutting tool can be manufactured by the following method. That is, after depositing a boron nitride film on a substrate, a polycrystalline diamond film is synthesized on the boron nitride film by a vapor phase synthesis method to form a laminated film of a boron nitride film and a polycrystalline diamond film. The polycrystalline diamond film side of the laminated film is attached by brazing to at least the rake face side of the tool base material (that is, the boron nitride film is the front side), and the substrate is removed before or after brazing, It is possible to manufacture a vapor-phase synthesized polycrystalline diamond brazing cutting tool having a rake face coated with a boron nitride film by performing the edging process. Further, at this time, the surface roughness of the boron nitride film on the rake face is set to Rm by setting the surface roughness of the substrate to 1 μm or less in Rmax.
It can be 1 μm or less in ax.

As the cutting tool base material used in the present invention,
It is not particularly limited as long as it has hardness and strength that can be used as a tool, but in the case of a polycrystalline diamond brazing cutting tool for attaching a polycrystalline diamond film by brazing, From the viewpoint of less generation of thermal stress, it is preferable to use a material having a thermal expansion coefficient close to that of the polycrystalline diamond film. Examples of such materials include cemented carbide and silicon nitride ceramics. The cutting tool can be applied to cutting tools such as drills and end mills, in addition to the chips shown in the examples below.

The present invention will be described in more detail with reference to the following examples, but the following examples are not intended to limit the present invention, and any change in the design of the present invention can be made without departing from the spirit of the preceding and the following. It is included in the technical scope.

[0021]

【Example】

Example 1 Tool shape SPG having various rake faces as shown in Table 1
Prepare a sintered diamond tip of N120304,
After charging these into an ion plating device and evacuating the device to 1 × 10 ⁻⁷ Torr, boron is evaporated by electron beam irradiation, and nitrogen gas is introduced into the device to generate arc discharge of nitrogen. By superimposing RF glow discharge, the surface of the sintered diamond tip was coated with a boron nitride film of various thicknesses. At this time, the pressure inside the apparatus during film formation was 1 × 10 ⁻³ Torr, and the film thickness of the boron nitride was controlled by controlling the film formation time.
The thus-produced boron nitride film was analyzed by an infrared absorption spectrometer and a transmission electron microscope. As a result, the film was composed of 93% by volume of cubic boron nitride and 7% by volume of amorphous boron nitride, The average particle size of cubic boron nitride is 0.03.
was μm. Table 1 shows the thickness of the boron nitride film and the surface roughness of the rake surface after coating.

[0022]

[Table 1]

Next, a cutting test was carried out using the obtained chips to investigate the surface roughness of the work surface and the welding condition on the rake face. The cutting conditions at this time are as follows:
-16% Si alloy is used, cutting speed: 400 m / mi
n, feed rate: 0.1 mm / rev, depth of cut: 0.25
mm / rev, cutting time: 20 minutes, and dry continuous cutting was performed. The results are shown in Table 2. As is clear from Table 2, it is possible to prevent the occurrence of welding on the rake face by covering the rake face with a boron nitride film and appropriately adjusting the surface roughness of the rake face. It turns out that it is effective in doing.

[0024]

[Table 2]

Example 2 On the surface of a cemented carbide chip having a tool shape of SPGN120308,
A polycrystalline diamond film was formed by the microwave plasma CVD method under the following synthesis conditions. At this time, the surface roughness of the polycrystalline diamond film increases with the film thickness, so by changing the film thickness, diamond-coated superhard chips having various surface roughness as shown in Table 3 below were obtained. (Synthesis conditions) Raw material gas: H ₂ (Flow rate: 100 cc / mi
n) CH ₄ (flow rate: 1 cc / min) -Pressure: 50 Torr-Substrate temperature: 850 ° C-Micro K wave output: 1 kw

A boron nitride film was formed on the surface of the diamond-coated superhard chip thus obtained in the same manner as in Example 1. Table 3 also shows the film thickness, particle size and composition of the boron nitride film, and the surface roughness of the rake surface after coating the boron nitride film.

[0027]

[Table 3]

Next, a cutting test was conducted using the obtained boron nitride film-covered vapor-phase synthetic diamond tip, and the surface roughness of the work surface and the welding condition on the rake face were investigated. The cutting conditions at this time were Al-12% Si alloy as the work material, cutting speed: 400 m / min, feed rate: 0.
Dry continuous cutting was performed with 1 mm / rev, depth of cut: 0.25 mm / rev, and cutting time: 40 minutes. The results are shown in Table 4. As is clear from Table 4, it is necessary to properly adjust the film thickness, grain size, composition of the boron nitride film, or the surface roughness of the boron nitride film, in order to prevent the deposition on the rake face. It can be seen that it is effective in preventing the occurrence of. Further, it can be seen that in the cutting tool of the present invention, welding was not generated on the rake face at all, and a good work surface roughness was obtained as compared with the comparative material.

[0029]

[Table 4]

Example 3 The surface of a silicon substrate having a surface roughness Rmax of 0.02 μm was subjected to a scratching treatment for generating diamond nuclei with a diamond paste having a grain size of 1/4 μm. The surface roughness of the treated silicon substrate is Rmax
Was 0.02 μm. On the surface of this silicon substrate,
Diamond was deposited in the same manner as in Example 2 to a film thickness of 100 μm.

The above diamond-deposited silicon substrate was replaced with 6
The silicon substrate was removed by immersing in a 30 wt% sodium hydroxide aqueous solution at 0 ° C. Subsequently, the diamond film from which the substrate has been removed is cut into a blade shape with a YAG laser,
The diamond film was brazed to the tip of the chip so that the original substrate side became the rake face, and the blade was processed. In this way, two diamond film brazing tips were produced. A boron nitride film was deposited on one of the surfaces in the same manner as in Example 1. At this time, the thickness of the boron nitride film is 0.2
The surface roughness Rmax was 0.21 μm, the ratio of cubic boron nitride was 94%, and the particle size of cubic boron nitride was 0.02 μm.

On the other hand, the surface roughness Rmax is 0.02 μm.
A cubic boron nitride film is deposited on the surface of the silicon substrate in the same manner as in Example 1, the surface is scratched with a diamond paste having a grain size of 1/4, and then diamond is made to have a thickness of 100 μm. Was deposited in the same manner. Subsequently, the diamond-deposited silicon substrate was immersed in a 30% by weight aqueous sodium hydroxide solution at 60 ° C. to dissolve and remove the silicon substrate. After that, the diamond film from which the substrate was removed was cut into a blade shape by a YAG laser, and then the chip blade tip was brazed so that the boron nitride film side became the rake face, and blade processing was performed. At this time, the thickness of the boron nitride film is 0.4
The surface roughness was 0.02 μm in Rmax, the ratio of cubic boron nitride was 94% by volume, and the particle size of cubic boron nitride was 0.02 μm.

A cutting test was carried out using the chips prepared as described above, and the surface roughness of the work surface and the welding condition on the rake face were investigated. The cutting conditions at this time are as follows: Al-10% Si alloy is used as the work material, and the cutting speed is 500 m.
/ Min, feed rate: 0.1 mm / rev, depth of cut:
Dry continuous cutting was performed at 0.2 mm / rev and a cutting time of 60 minutes. As a result, welding occurs in the chip not coated with the boron nitride film, and the surface roughness to be machined is Rma.
Although x was 4.7, no welding occurred in the two types of chips coated with the boron nitride film. Of the two types of chips coated with a boron nitride film, the one having a rake surface with a surface roughness Rmax of 0.21 μm has a surface roughness Rmax of the work surface of 1.9 μm, and the rake surface has a surface roughness R.
If the maximum value is 0.02 μm, the surface roughness of the work surface is Rma.
The value of x was 1.7 μm, and the surface roughness of the work surface was better than that of the sample not coated with the boron nitride film.

[0034]

The present invention is constructed as described above, and at least the rake face of the tool is coated with a boron nitride film having a lower affinity for the work material than diamond, so that the rake face is moved to the rake face. It is possible to prevent the welding of chips of
It became possible to obtain excellent surface roughness.

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location C30B 29/04 W 8216-4G (72) Inventor Katsuhiko Ozaki 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Kobe Steel Co., Ltd.Kobe Research Institute

Claims (9)

[Claims] 1. A diamond cutting tool in which at least a cutting action portion of the cutting tool is composed of polycrystalline diamond, and a surface of a polycrystalline diamond film corresponding to at least a rake face of the cutting action portion is covered with a boron nitride film. A diamond cutting tool with excellent welding resistance. 2. The diamond cutting tool according to claim 1, wherein the polycrystalline diamond is deposited on the surface of at least a cutting action portion of a cutting tool base material by a vapor phase synthesis method. 3. The diamond cutting tool according to claim 1, wherein the polycrystalline diamond film formed by vapor phase synthesis is attached to at least the cutting action portion of the cutting tool base material by brazing. 4. The diamond cutting tool according to claim 1, wherein the boron nitride film has a thickness of 0.05 to 3 μm. 5. The surface roughness of the rake face has a Rmax of 1 μm.
The diamond cutting tool according to any one of claims 1 to 4, which has a thickness of m or less. 6. The diamond cutting tool according to claim 1, wherein the boron nitride film contains 70% by volume or more of cubic boron nitride. 7. The diamond cutting tool according to claim 6, wherein the grain size of the cubic boron nitride in the boron nitride film is 0.01 to 2 μm. 8. In manufacturing the diamond cutting tool according to claim 3, a boron nitride film is deposited on a substrate, and then a polycrystalline diamond film is synthesized on the boron nitride film by a vapor phase synthesis method. , A laminated film of a boron nitride film and a polycrystalline diamond film is produced, and the laminated film polycrystalline diamond film side is attached to at least the rake face side of the cutting action portion of the tool base material by brazing, and the substrate is brazed. A method for producing a diamond cutting tool having excellent welding resistance, characterized by being removed before or after. 9. The surface roughness Rmax of the substrate is 1 μm.
The method for manufacturing a diamond cutting tool according to claim 8, which is as follows.