JP2710287B2 - Polycrystalline diamond for tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a tool for a tool which has a remarkably improved strength, welding resistance, heat resistance and wear resistance suitable for use as a cutting tool, a wear-resistant tool and the like. Related to crystalline diamond.

[Conventional technology]

As a diamond for tools, a sintered diamond obtained by sintering fine powder of diamond under ultra-high pressure is used for cutting tools, drill bits, drawing dies and the like of non-ferrous metals.

For example, Japanese Patent Publication No. 52-12126 discloses that diamond powder is brought into contact with a powder compact or sintered body of a WC-Co cemented carbide and sintered, and a part of Co is used as a bonding metal in the diamond powder. A technique for producing a diamond sintered body containing 10 to 15% by volume of Co by infiltration is disclosed. Although this diamond sintered body has practical performance as a cutting tool for non-ferrous metals, it has a drawback of poor heat resistance. For example, when heated to 700 ° C. or higher, wear resistance and strength are reduced, and at a temperature higher than 900 ° C., the sintered body is broken. It is considered that such a defect in heat resistance is caused by graphitization of diamond at the interface between diamond particles and Co as a binder and thermal stress based on a difference in coefficient of thermal expansion when both are heated.

As an attempt to improve the heat resistance of the above-mentioned diamond sintered body, for example, Japanese Patent Application Laid-Open No. 53-114589 proposes that the sintered body is subjected to an acid treatment to remove the binding metal Co. However, in this method, since the removed Co portions become vacancies, there is a disadvantage that the heat resistance is improved but the strength is reduced.

On the other hand, recently, it has become possible to synthesize diamond by a method of chemically synthesizing from the gas phase. As this chemical vapor synthesis method (CVD method), various proposals have been made to excite and decompose hydrogen and hydrocarbon source gases. For example,
No. 58-91100 discloses a method of preheating a raw material gas with a thermionic emitting material heated to 1000 ° C. or higher, and then introducing the raw material gas to a heated base material surface to precipitate diamond by thermal decomposition of hydrocarbons. JP-A-58-110494 discloses a method in which hydrogen gas is passed through a microwave electrodeless discharge and then mixed with a hydrocarbon gas to precipitate diamond in the same manner; No. 30398 discloses that a microwave is introduced into a mixed gas of a hydrogen gas and an inert gas to generate a plasma, a substrate is placed in the mixture, and the substrate is heated to 300 to 1300 ° C. to decompose the hydrocarbon. Methods for depositing diamond are described respectively. Japanese Patent Application Laid-Open No. 61-158899 discloses that an oxygen-containing gas is mixed with a hydrocarbon as a raw material gas.

By applying these CVD methods, tools having polycrystalline diamond coated on a substrate have also been provided. However, since the diamond film is thin and the adhesion strength of the diamond to the substrate is insufficient, sufficient performance as a tool has not been obtained.

[Problems to be solved by the invention]

The present inventors have examined the drawbacks of the conventional diamond tool and have previously described Japanese Patent Application Nos. 63-34033 and 63-340.
According to No. 34, the polycrystalline diamond formed on the substrate by applying the CVD method is separated from the substrate by chemical treatment or mechanical means, and brazed to a support member made of hardened steel or cemented carbide. By doing so, we have proposed a diamond tool which is not less inferior in strength and wear resistance than conventional diamond tools, and which is far superior in heat resistance.

However, as a result of progressing the performance evaluation of the diamond tool according to the above proposal, it was found that there was a difference in tool performance, particularly in chipping resistance and wear resistance, depending on the type of polycrystalline diamond as a tool material, leading to the present invention. Things.

That is, an object of the present invention is to improve the strength, welding resistance, heat resistance and wear resistance, and to provide a polycrystalline diamond for a tool which is particularly excellent in chipping resistance and wear resistance.

[Means for solving the problem]

In order to achieve the above object, the polycrystalline diamond for tools of the present invention has a thickness of 50 μm or more and an average crystal grain size of 50 μm.
m or less and diamond carbon (X) and non-diamond carbon (Y) by Raman spectroscopy as indices of purity.
Is characterized by having a peak ratio (Y / X) of 0.2 or less, preferably 0.05 or less, and a specific resistance of 10 ⁷ Ω · cm or more.

As an index of the purity of polycrystalline diamond, in addition to the peak ratio and the specific resistance of Raman spectroscopy, light transmittance, dielectric loss, and the like can be used.In this case, the visible light transmittance at a wavelength of 600 nm is 10%. % And a dielectric loss at 100 KHz of 0.2 or less are necessary conditions, but they cannot be said to have a directly corresponding relationship.

[Action]

It is a particularly important condition that polycrystalline diamond has high purity. As an index of the purity, any one of peak ratio and specific resistance, light transmittance, and dielectric loss of Raman spectroscopic analysis is used as described above. In these purity indexes, when the peak ratio (Y / X) exceeds 0.2, when the specific resistance is smaller than 10 ⁷ Ω · cm, when the visible light transmittance at a wavelength of 600 nm is smaller than 10%, or If the dielectric loss at 100 KHz is greater than 0.2, it can be determined that the purity has decreased due to the inclusion of many non-diamond carbon and other impurities,
Such a diamond is liable to generate large defects when used as a tool, and wear due to minute crushing or falling off of particles becomes remarkable. This is because the non-diamond carbon is present between the diamond particles, which lowers the intergranular bond strength, and the diamond particles deposited under such conditions have a large number of defects, so the strength of the particles themselves is also small. It is presumed to be due to the above.

Polycrystalline diamond satisfying such conditions is described above.
It can be produced by selecting the synthesis conditions based on the CVD method.In particular, plasma is used to excite the source gas, and oxygen-containing gas such as oxygen and water vapor is used as the source gas in addition to hydrocarbons and hydrogen. It is effective to use. Note that it is preferable to select synthesis conditions so that impurities other than non-diamond carbon are not mixed as much as possible.

Further, the thickness of the polycrystalline diamond is set to 50 μm or more because the flank wear width at the time of life when the cutting tool is used is 50 μm.
m or more, and when the thickness is less than 50 μm, the strength is reduced and the material is easily broken. Further, when abrasion resistance is required, the thickness is preferably set to 0.3 to 3.0 mm. This is because, by increasing the thickness, the heat radiation characteristics are improved, and the rise in the temperature of the cutting edge when using the tool is suppressed.

Further, the reason why the average crystal grain size is set to 50 μm or less is to improve the fracture resistance, and the range of 1 μm to 10 μm is more preferable. If it is larger than this range, the fracture resistance gradually decreases, and if it is smaller than this range, the wear resistance decreases. Such control of the crystal grain size can be performed by the method described in Japanese Patent Application Nos. 63-139143 and 63-148631 by the present inventors.

The polycrystalline diamond of the present invention synthesized by a CVD method or the like is separated from the base material and brazed to a supporting member in the same manner as in Japanese Patent Application Nos. 63-34033 and 63-34034. Tools or thick ones are used as single tools.

〔Example〕

Example 1 H ₂ 2 was used as a source gas by microwave plasma CVD.
_{50cc / min, CH 4 5cc /} min, and the Ar80cc / min using a pressure 20
Polycrystalline diamond on Mo substrate at 0 torr about 0.5 in 20 hours
mm. The average crystal grain size on the growth upper surface of the polycrystalline diamond (A) was about 40 μm. next,
Polycrystalline diamond (B) was formed to a thickness of about 0.4 mm in 20 hours under the same conditions as above except that 1.0% by volume of steam was further added to the raw material gas. This average grain size is about 25
μm.

Thereafter, when the Mo substrate was dissolved and removed by hot aqua regia treatment to recover the polycrystalline diamond, (A) was black and opaque, but (B) was white and transparent. The specific gravity was 3.52, and the result of Raman spectroscopy was as shown in FIG. ^1. The non-diamond of 1360 to 1580 cm ^-1 measured from the back ground between 1800 cm ^{-1 and} 1000 cm ^-1. The peak ratio (Y / X) between the carbon peak (Y) and the diamond carbon peak (X) measured using the periphery of the peak at 1333 cm ^-1 as the background is (A) of 0.32, while (B) is 0.32. ) Is 0.05, and the specific resistance (A) is 3 × 10
(B) was 7 × 10 ¹² Ω · cm against ³ Ω · cm.
Looking at other indexes of purity, the visible light transmittance at a wavelength of 600 nm (sample thickness 50 μm) is (A) 3% and (B) 60%.
%, And the dielectric loss at 100 KHz was (A) 0.95 to (B) 0.03, clearly indicating that (B) had a lower non-diamond carbon content and higher purity.

Next, in order to evaluate tool performance, each polycrystalline diamond was brazed to a cemented carbide base metal to prepare a cutting chip. As a comparative material, an ultrahigh-pressure sintered diamond containing 10% by volume of a binder Co and having an average particle size of 10 μm was similarly used to produce a cutting chip. A390 alloy (Al-17Si) round bar with four grooves extending in the axial direction is formed on the outer peripheral surface as a work material, cutting speed 300m / min, depth of cut 0.2mm, feed 0.1mm / r
Dry cutting was performed under the conditions of ev., and the tool performance was evaluated.

As a result, (A) was lost at the time of cutting for 40 minutes,
(B) has no defect and the average wear width after 90 minutes cutting is 0.04mm
It was. Although the comparative material did not break, the average wear width after cutting for 90 minutes was 0.09 mm.

Example 2 A linear tungsten filament having a diameter of 0.5 mm and a length of 20 mm was used as a thermionic emitting material, and a raw material gas comprising hydrogen, a carbon source and water vapor was decomposed and excited to form a first material on a Si substrate.
Polycrystalline diamond was formed for 10 hours under the conditions shown in the table.

When each of the obtained polycrystalline diamonds (C) to (H) was subjected to an acid treatment and separated and recovered from the Si substrate, (D) and (E)
Was black and opaque, but all others were white and translucent. Table 2 shows the results of measuring the thickness, average crystal grain size, and index of purity of each polycrystalline diamond.

(Note) The measurement of the peak ratio (X / Y), transmittance, and dielectric loss is the same as in Example 1.

Each of polycrystalline diamonds (C) to (H) is brazed to a cemented carbide base metal to produce a cutting chip, and an AC8A alloy (Al-12Si) having four axially extending grooves formed on the outer peripheral surface ) Using a round bar as the work material, cutting speed 500m / min, depth of cut 0.2m
Table 3 shows the results of cutting for 90 minutes in a dry condition under conditions of m and feed rate of 0.1 mm / rev.

Although the samples (C), (F) and (G) according to the present invention all showed good tool properties, the sample (D) had a low purity but was relatively fine so that no defects occurred,
Since the purity was low, the abrasion resistance was inferior. The sample (E) was defective in a short time because the particle size was coarse and the purity was low, and the sample (H) was thin and the strength was reduced, respectively.

Example _{3 C 2 H 6: H 2} ( volume ratio 1: 100) 0-2 further O ₂ mixed gas of
Using a source gas with 0% by volume added, adjust the gas flow rate to 200 cc / min and the pressure to 180 Torr, apply high frequency (13.56 MHz) at an output of 900 W to excite the source gas, and with a 20 hour reaction time
Polycrystalline diamond having a thickness of 0.5 to 0.7 mm was formed on a Si substrate.

The average particle size of the obtained polycrystalline diamond is 7 μm.
m and a thickness of 650 μm, each having a different purity were selected on the basis of each purity index, and each was brazed to a cemented carbide holder and subjected to a blade treatment to evaluate the cutting performance of the hard ceramics. The cutting evaluation was performed using a round alumina sintered body (Hv =
The outer periphery turning of 2000 kg / mm ² ) was performed for 15 minutes by a wet method under the conditions of a cutting speed of 50 m / min, a cutting depth of 0.2 mm, and a feed of 0.25 mm / rev. The relationship between the index of purity and the flank wear width was determined and is shown in FIGS. 2 to 5, respectively.

From this result, it can be seen that any of the indices of purity within the range of the present invention have excellent wear resistance.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, strength, welding resistance, heat resistance, and abrasion resistance are improved, and the polycrystalline diamond for tools excellent especially in fracture resistance and abrasion resistance can be provided.

Therefore, a high-performance tool can be manufactured using the polycrystalline diamond, and it is particularly effective for tools such as cutting tools, excavating tools, and dressers.

[Brief description of the drawings]

FIG. 1 is a graph showing the results of Raman spectroscopic analysis of the polycrystalline diamond prepared in Example, and FIGS. 2 to 5 are flank wear widths of the polycrystalline diamond prepared in Example 3 and Raman as an index of purity. It is a graph which shows the relationship between a spectral analysis peak ratio, specific resistance, visible light transmittance, and dielectric loss, respectively.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akihiko Ikegaya 1-1-1, Koyokita, Itami-shi, Hyogo Sumitomo Electric Industries, Ltd. Itami Works (72) Inventor Naoji Fujimori 1-chome, Koyokita, Itami-shi, Hyogo No. 1-1 In Itami Works of Sumitomo Electric Industries, Ltd. (56) References JP-A-62-107068 (JP, A) JP-A-63-33570 (JP, A) JP-A-64-52699 (JP, A) ) JP-A-63-55197 (JP, A)

Claims (3)

(57) [Claims] Claims: 1. A polycrystalline diamond which is brazed to a support member to form a tool or as a single tool as it is,
The thickness is 50 μm or more, the average crystal grain size is 50 μm or less,
A polycrystalline diamond for tools, having a peak ratio (Y / X) of diamond carbon (X) to non-diamond carbon (Y) of 0.2 or less and a specific resistance of 10 ⁷ Ω · cm or more by Raman spectroscopy. 2. A polycrystalline diamond which is brazed to a support member to form a tool or as a single tool as it is,
The thickness is 50 μm or more, the average crystal grain size is 50 μm or less,
Polycrystalline diamond for tools, having a visible light transmittance of 10% or more at a wavelength of 600 nm. 3. Polycrystalline diamond brazed to a support member to form a tool or as a single tool,
The thickness is 50 μm or more, the average crystal grain size is 50 μm or less,
Polycrystalline diamond for tools characterized by having a dielectric loss of 0.2 or less at 100 KHz.