JPH0657427A - Hard carbon film coated sintered hard alloy tool and its production - Google Patents

Abstract

PURPOSE:To improve the adhesion of the base of the base metal of a tool and a hard carbon film by coating the base metal with W, bringing an excited carbon-contg. gas into contact with it to form porous WC and thereafter coating it with a hard carbon film having small grain diameter. CONSTITUTION:The surface of the base metal of the tool of WC sintered hard alloy is coated with metallic W into about 1 to 3mum thickness. An excited carbon-cong. gas is brought into contact with the coated metallic W to form porous WC having >=0.1mum average grain diameter as a substrate. The substrate is coated with a hard carbon film having average grain diameter smaller than that of the porous WC by using a vapor phase synthesis method. In this way, the prevention of the diffusion of Co on the surface of the base metal can be attained, by which the hard carbon film coated sintered hard alloy tool in which the adhesion of the base metal and hard carbon film is excellent can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard carbon film-coated cemented carbide tool in which a WC-based cemented carbide is used as a tool base material and the base material is coated with a hard carbon film such as diamond or amorphous carbon. Regarding its manufacturing method, in particular, a hard carbon coated cemented carbide tool that achieves good adhesion to a base material of a hard carbon film and is optimal as a cutting tool or wear resistant tool, and a method for manufacturing such a tool Related to the improvement of.

[0002]

2. Description of the Related Art Hard carbon such as diamond and amorphous carbon has extremely high hardness and high thermal conductivity as compared with alumina, silicon nitride, tungsten carbide and the like which have been widely used as conventional hard materials. Therefore, application development as a material for cutting tools, wear resistant tools, etc. is being actively pursued.

As an example of a technique for applying diamond as a material for a cutting tool, a diamond sintered body tool using diamond synthesized by sintering under ultrahigh pressure and high temperature is known, but it is expensive. In addition, it is difficult to process into a complicated shape because there is no one having a hardness higher than that of diamond, and the shape is also restricted.

Recently, a hard carbon film such as diamond or amorphous carbon is formed by a chemical vapor phase synthesis method using a carbon-containing gas (for example, a mixed gas of hydrogen and hydrocarbon) excited by a microwave or a hot filament. Since it is possible to form a hard carbon film on a base material, and this technology can easily and inexpensively form a hard carbon film even for tools with complex shapes, tool development is actively applying this technology. Is being advanced to.

[0005]

However, the hard carbon film synthesized by vapor phase has a large internal stress of the film and a weak adhesion strength with the base material. There is a problem in that the excellent characteristics of hard carbon such as high hardness and high thermal conductivity cannot be fully utilized. Especially when the tool base material contains about 5 to 20% of Co as a binder like WC cemented carbide, carbon is not dissolved in Co during synthesis to form a hard carbon film. However, even if a hard carbon film is formed, the adhesion strength to the tool base material is not sufficient, and there is a drawback that peeling occurs easily. Therefore, it is said that the most important point for improving the adhesion between the WC-based cemented carbide base material and the hard carbon film is to prevent Co diffusion on the base material surface.

As one of the proposals for solving such inconvenience, an attempt has been made to improve the adhesion between the cemented carbide base material and the hard carbon film by forming an underlayer on the surface of the cemented carbide base material. ing. For example, JP-A-63-19987
No. 0, No. 58-126972, JP-A-1-201478 and No. 1-20
No. 1480 and the like disclose a method of forming an underlayer on the surface of a cemented carbide base material. However, these techniques not only require complicated processing steps, but also
Since the underlayer is previously formed as a carbide or oxide on the surface of the base material, the adhesion between the underlayer and the base material is still insufficient, and there is a drawback that it cannot reach the stage of practical use.

On the other hand, Japanese Patent Laid-Open No. 1-275759 also proposes a technique for preventing Co diffusion on the surface of the base material by forming an underlayer on the base material of the cemented carbide. In this technique, one or more metals selected from Group IVa, Va, VIa metals and Si are coated as an underlayer, and these metals are carbonized to form a hard carbon film while forming an underlayer. The purpose is to improve the adhesion. However, even with this technique, the expected effect of improving the adhesiveness has not been obtained. That is, in this technology, the synthesis temperature is relatively high at 900 ° C, the carbonization reaction of the metal is preferentially promoted over the nucleation of hard carbon in the initial stage of synthesis, and the nucleation density of hard carbon is significantly suppressed. Will be lost. As a result, the synthesis of the hard carbon film itself is suppressed, or even if it becomes a film, a large number of bonds remain at the interface with the underlying layer, and good adhesion cannot be obtained. Further, in this technique, a metal such as IVa, Va, VIa group or Si is shown as the type of the underlayer, but the thermal expansion coefficient of the carbide of these metals and the cemented carbide is often different, Adhesion between the base material and the underlayer also deteriorates.

The present invention has been made under these circumstances, and an object thereof is a hard carbon film-coated cemented carbide tool excellent in adhesion between a cemented carbide base material and a hard carbon film, and such a tool. It is to provide a useful method for manufacturing a simple tool.

[0009]

According to the method of the present invention which has achieved the above object, a WC-based cemented carbide is used as a tool base material, and a hard carbon film is coated on the underlayer by a vapor phase synthesis method. In producing a carbon film-coated cemented carbide tool, a metal W is coated on the surface of the base material, and then an excited carbon-containing gas is brought into contact with the metal W to form a porous WC having an average particle size of 0.1 μm or more.
Is formed as an underlayer, and the vapor phase synthesis method is applied to coat the underlayer surface with a hard carbon film having an average particle size smaller than the crystal grain size of the porous WC. By carrying out this method, a hard carbon film-coated cemented carbide tool having excellent adhesion can be obtained.

[0010]

In order to solve the above problems, the present inventors have studied from various angles. First, it was found that WC, which is the main component of the cemented carbide, is the most desirable as the material of the underlayer that is most effective in preventing Co diffusion on the surface of the WC-based cemented carbide base material. That is, when another carbide is used as the underlayer, the adhesion with the hard carbon film is poor, but the adhesion with the cemented carbide as the base material is poor. However, the underlayer is WC
Then, it turns out that such inconvenience does not occur.

Further, as a means for forming an underlayer made of WC on the surface of the base material and forming a hard carbon film thereon, W is used.
The surface of the C-based cemented carbide base material is coated with the metal W, and then the excited carbon-containing gas is brought into contact with the metal W to obtain an average particle size of 0.1.
After forming a porous WC having a size of μm or more as an underlayer, a vapor phase synthesis method is applied to obtain an average particle size smaller than that of the porous WC (hence, WC is polycrystalline). The inventors have found that it is optimal to coat the surface of the underlayer with a hard carbon film, and completed the present invention.

In the present invention, as described above, the metal W coated on the surface of the cemented carbide base material is brought into contact with an excited carbon-containing gas to carbonize the metal W, thereby carbonizing the porous Wc having an average particle diameter of 0.1 μm or more. To form as. And this porous W
By growing a hard carbon film having an average particle size smaller than the crystal grain size of WC so as to enter the inside of C, the contact area between the underlayer and the hard carbon film is remarkably increased. Achieved improved adhesion. From this point of view, after forming the underlayer, fine flaws may be formed on the surface of the underlayer, and then a hard carbon film may be coated thereon.

In the present invention, the thickness of the metal W coating the surface of the cemented carbide base material is preferably 1 to 3 μm.
That is, if the thickness is less than 1 μm, Co diffuses from the cemented carbide as the base material, and if it exceeds 3 μm, the effect of stress due to the difference in the thermal expansion coefficient between the underlayer and the base material cannot be ignored, and However, peeling is likely to occur. The temperature at which the metal W is carbonized is preferably about 500 to 1000 ° C. from the viewpoint that the average particle size of WC is 0.1 μm or more.
Further, in the present invention, the thickness of the hard carbon film coated on the underlayer is not particularly limited, but practically 3
It is about 20 to 20 μm, more preferably about 10 to 20 μm.

The present invention will be further described below with reference to examples, but the following examples are not of a nature limiting the present invention, and any modification of the design in view of the spirits of the preceding and the following will be technical aspects of the present invention. It is included in the range. For example, in the following examples, the ion plating method was used as the method for coating the metal W and the microwave plasma CVD method was used as the method for coating the hard carbon film. However, other PVD methods are used in the former case and other CV methods are used in the latter case.
D method (hot filament method, high frequency plasma CVD method, etc.)
Can be used. Further, in the following embodiments, the case where the tool of the present invention is applied as a tip and a drill is shown, but it goes without saying that the tool of the present invention is not limited to these and can be applied to, for example, an end mill.

[0015]

【Example】

Example 1 As a cemented carbide base material, a throwaway tip (shape SPGN) of WC-6% Co was used, and a metal W was formed on the flank and rake surface of this tip by an ion plating method.
Was coated. At this time, the thickness of the metal W is 0.5 μ
m, 1.0 μm, 2.0 μm, 3.0 μm and 4.0 μm. Next, the metal W was brought into contact with the methane-hydrogen mixed gas excited by applying the microwave plasma CVD method for 1 hour. The base material temperature at this time was about 750 ° C. According to SEM observation and X-ray diffraction of the surface of the base material, the metal W
Was confirmed to have changed to a porous WC (polycrystalline film) having an average particle size of 0.6 μm. Continue to use these base materials
Fine flaws were formed on the surface of the porous WC by immersing it in an ethanol suspension in which diamond abrasive grains (particle size: about 0.5 μm) were dispersed and performing ultrasonic treatment.

Microwave plasma CV is applied to these base materials.
A hard carbon film was formed to a thickness of about 15 μm by gas phase synthesis with a methane-hydrogen mixed gas excited by applying the method D for about 12 hours. The synthesis conditions at this time were: base material temperature: 900 ° C., methane concentration: 2% by volume. Also, for comparison, the same chip was prepared except that the underlayer was not coated. As a result of Raman analysis and X-ray diffraction analysis, it was confirmed that a hard carbon film made of a mixture of diamond and amorphous carbon and having a Vickers hardness of 7000 to 8000 was formed on the surface of the underlayer. A cutting test was performed using the above 6 types of chips and their cutting lives were compared. At this time, the work material is Al-
20% Si is used, and the cutting speed, feed amount and depth of cut are 50
It was set to 0 m / min, 0.6 mm / rev, and 1.0 mm. The results are shown in Table 1.

[0017]

[Table 1]

As is apparent from Table 1, it is clear that the examples of Nos. 2 to 4 have an overwhelmingly small amount of wear or a long life even under severe conditions with a large depth of cut. . However, the thickness of the metal W is 0.5 μm or
In case of 4.0 μm (No. 1, 5), comparative example (No. 6)
However, the effect of the present invention is not sufficiently exerted. When the thickness of the metal W is 0.5 μm, peeling occurs between the hard carbon film and the WC underlayer, and when the base material surface (that is, the surface of the WC layer) is analyzed by EPMA, Co is detected. Was done. This is because Co contained in the base material permeates the underlayer and is locally deposited during the formation of the WC or the synthesis of the hard carbon film, and the presence of this Co reduces the adhesion between the hard carbon film and the WC underlayer. It is considered to be a thing. On the other hand, when the thickness of the metal W was 4.0 μm, peeling occurred between the WC underlayer and the base material. W film is 3 μm
If it exceeds, it takes a long time to uniformly carbonize over the entire film thickness, and a brittle (MCo) ₆ C-like precipitate is formed at the interface, resulting in an adverse effect. In addition, since short-time carbonization does not proceed to the interface, uncarbonized metal W is left at the interface, and the effect of stress due to the difference in thermal expansion coefficient from the base metal cannot be ignored, and the adhesion is adversely affected as in the above. Will be affected.

Example 2 A hard carbon film-coated cemented carbide drill was produced in the same manner as in Example 1 except that a cemented carbide drill having a shaft diameter of 8 mm (Co content: about 10%) was used as the tool base material. did. The coating thickness of the metal W at this time was about 2 μm. For comparison, an untreated drill not according to the invention was also made. A cutting test was performed on these drills. At this time, the work material was Al-16% Si, and the cutting conditions were a cutting speed of 150 m.
/ min, feed rate: 0.1 mm / rev and cutting length: 25 mm.
As a result, in the drill of the present invention, there was no peeling of the film even after cutting about 3000 holes, whereas in the comparative example, the blade edge was severely worn at the time of cutting about 250 holes, and the life was reached.

[0020]

According to the present invention, C on the surface of the cemented carbide base material
o Diffusion prevention can be achieved, and as a result, a hard carbon film-coated cemented carbide tool having excellent adhesion to the base material can be realized, and its industrial value is extremely large.

Claims (3)

[Claims] 1. When manufacturing a hard carbon film-coated cemented carbide tool by coating a hard carbon film on a base layer by a vapor phase synthesis method using a WC-based cemented carbide as a tool base material, the surface of the base material is used. The metal W is coated with the metal W, and then the excited carbon-containing gas is brought into contact with the metal W to form a porous W having an average particle size of 0.1 μm or more.
After forming C as an underlayer, a vapor phase synthesis method is applied to coat the surface of the underlayer with a hard carbon film having an average particle size smaller than the crystal grain size of the porous WC. A method for manufacturing a coated cemented carbide tool. 2. The method of claim 1, wherein the metal W
The coating method according to claim 1, wherein the coating thickness is 1-3 μm. 3. A hard carbon film-coated cemented carbide tool manufactured by the method according to claim 1.