JP6015325B2 - Polycrystalline diamond, method for producing the same, and tool - Google Patents

Description

  The present invention relates to a polycrystalline diamond body and a method for manufacturing the same, and a tool, and more particularly to a polycrystalline diamond body having an orientation on a (111) plane, a manufacturing method therefor, and a tool.

As a material constituting conventional tools such as cutting tools, dressers, dies, and excavating bits, a polycrystalline diamond having no cleaving property is used. However, the diamond polycrystal is generally produced using a sintering aid or a binder. As the sintering aid, for example, iron group element metals such as iron (Fe), cobalt (Co), nickel (Ni), and carbonates such as calcium carbonate (CaCO ₃ ) are used. As the binder, for example, ceramic such as silicon carbide (SiC) is used.

  For example, a polycrystalline diamond produced using a sintering aid can be obtained by using diamond powder as a raw material together with a sintering aid at a high pressure and high temperature (generally, pressure is stable). It is produced by sintering under conditions of about 5 to 8 GPa and a temperature of about 1300 to 2200 ° C. In this case, the obtained polycrystalline diamond contains a sintering aid. Such a sintering aid has a considerable influence on mechanical properties such as hardness and strength and heat resistance of the polycrystalline diamond.

  Also known are those obtained by removing the sintering aid by acid treatment, and diamond sintered bodies with excellent heat resistance using heat-resistant SiC as a binder, but they have low hardness and strength and are used as tool materials. It does not have sufficient mechanical properties (hardness characteristics, wear resistance, etc.).

  On the other hand, a polycrystalline diamond obtained by vapor phase synthesis is an example of polycrystalline diamond that is produced without using a sintering aid and does not contain a sintering aid. However, the diamond polycrystalline body produced by this method is poor in mechanical strength because it easily contains hydrogen at the grain boundary and has weak interparticle bonding force.

  Naturally produced diamond polycrystals (carbonados, ballasts, etc.) are also known, and some are used as drill bits, but due to the large variation in materials and the small amount of output, they are not very used industrially. It has not been.

  For some applications, single crystal diamond is used. However, it is limited to ultra-precision tools and precision wear-resistant tools due to dimensional and price constraints. Furthermore, the single crystal diamond has strong wear resistance with respect to the (111) plane, but there are restrictions on the use and use conditions due to the (111) cleavage of the single crystal diamond.

  In contrast, T.W. Irifune, H.M. Sumiya, “New Diamond and Frontier Carbon Technology”, 14 (2004) p313 (Non-Patent Document 1), and Kakutani, Iriaki, SEI Technical Review 165 (2004) p68 (Non-Patent Document 2) include high-purity high-crystals. A method for obtaining a dense and high-purity diamond polycrystal by direct conversion sintering by indirect heating at an ultrahigh pressure and high temperature of 12 GPa or more and 2200 ° C. or more using a starting graphite as a starting material is disclosed.

T.A. Irifune, H.M. Sumiya, “New Diamond and Frontier Carbon Technology”, 14 (2004) p313. Kakutani, Iriaki, SEI Technical Review 165 (2004) p68

  The polycrystalline diamond obtained by the method described in Non-Patent Document 1 or 2 has a very high hardness and excellent wear resistance.

  However, since the polycrystalline diamond obtained by the method described in Non-Patent Document 1 or 2 exhibits isotropic properties, it is possible to use a (111) plane that exhibits particularly excellent hardness characteristics and wear resistance in diamond. It was difficult.

  The present invention has been made to solve the above-described problems. A main object of the present invention is to provide a polycrystalline diamond having excellent hardness characteristics and wear resistance, a method for producing the same, and a tool.

  As a result of intensive research to solve the above-mentioned problems, the present inventors have directly converted and sintered pyrolytic graphite having orientation on a specific surface under an ultra-high pressure and high temperature, It has been found that a polycrystalline diamond having an orientation plane of (111) is obtained.

The diamond polycrystal according to the present invention is a diamond polycrystal having a diamond single phase structure, and the diamond polycrystal with respect to the X-ray diffraction intensity I ₍₁₁₁₎ of the (111) plane of the diamond polycrystal ( The ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ of the X-ray diffraction intensity I ₍₂₂₀₎ of the ₍ 220) plane is 0.15 or less. Here, “diamond single phase” means that it does not contain a sintering aid or a binder.

  Thereby, since the (111) plane is an orientation surface, the diamond polycrystal of this invention can be made harder than the conventional diamond polycrystal.

  The average particle diameter of the polycrystalline diamond is 100 nm or less. Here, the “crystal grain size of the polycrystalline diamond” was measured by directly observing with a microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The average value of the outer diameter (longest part) of individual single crystal particles constituting the polycrystalline diamond, that is, primary particles. The Knoop hardness of the polycrystalline diamond may be 130 GPa or more. The hydrogen concentration at the crystal grain boundary of the polycrystalline diamond may be less than 100 ppm. Thereby, the slip of the crystal grain in a crystal grain boundary can be suppressed, and the coupling | bonding of crystal grains can be strengthened.

  The tool which concerns on this invention consists of the said diamond polycrystal. In this way, a tool with high hardness and excellent wear resistance can be realized.

  The method for producing a polycrystalline diamond according to the present invention includes a step of preparing a carbon material made of graphite-like carbon and having an orientation on the (002) plane, and a pressure and temperature range in which diamond is thermodynamically stable. Converting the carbon material directly into diamond. If it does in this way, the ceramic sintered compact according to this invention can be obtained easily.

  The method for producing a polycrystalline diamond according to the present invention comprises a step of preparing a carbon material made of graphite-like carbon and having orientation on the (002) plane, and the carbon material at a pressure of 15 to 30 GPa and a temperature of 1500 to 3000 ° C. And a step of directly converting to diamond by sintering under the above conditions. If it does in this way, the ceramic sintered compact according to this invention can be obtained easily.

In the carbon material, the ratio I ₍₁₁₀₎ / I ₍₀₀₂₎ of the (110) plane X-ray diffraction intensity I _{(110) to} the ₍₀₀₂ ) plane X-ray diffraction intensity I ₍₀₀₂₎ is 0.01 or less. Preferably there is. The carbon material is preferably pyrolytic graphite.

  The diamond polycrystal according to the present invention can have higher hardness than the conventional diamond polycrystal because the (111) plane is an orientation plane. Moreover, the diamond polycrystal according to the present invention can have higher wear resistance than the conventional diamond polycrystal.

  The method for producing a polycrystalline diamond according to the present invention comprises a step of directly converting the carbon material oriented in the (002) plane into a diamond by sintering. Can be produced.

It is the schematic of the tool which concerns on this Embodiment. 2 is an X-ray diffraction spectrum of the starting material of Example 1. 2 is an X-ray diffraction spectrum of the polycrystalline diamond of Example 1. FIG.

Embodiments of the present invention will be described below.
The diamond polycrystal according to the present embodiment is a diamond single-phase polycrystal. That is, the polycrystalline diamond does not substantially contain a binder, a sintering aid, a catalyst and the like. At this time, the average particle diameter of the polycrystalline diamond is about 100 nm or less. That is, the polycrystalline diamond according to the present embodiment has crystal grains having an average grain size of about 100 nm or less, which are directly bonded to each other, and has a dense crystal structure with very few voids. .

Further, polycrystalline diamond according to the present embodiment, the polycrystalline diamond for (111) X-ray diffraction intensity _I of plane _(111), polycrystalline diamond of (220) plane of the X-ray diffraction intensity _{I ( 220)} ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ is 0.15 or less. That is, the polycrystalline diamond according to the present embodiment has a surface in which a plurality of single-crystal diamonds included in the polycrystalline diamond are oriented in the [111] direction (hereinafter referred to as X-rays in the polycrystalline diamond). A plane having a diffraction intensity I ₍₂₂₀₎ ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ of 0.15 or less is referred to as a plane oriented in the [111] direction or a (111) oriented plane).

From the examples described later, the average particle diameter of the polycrystalline diamond composed of a diamond single phase is 100 nm or less, and the X-ray diffraction intensity ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ is 0.04 to 0.13. It was confirmed that a certain polycrystalline diamond had a high Knoop hardness at room temperature on the (111) orientation plane of 155 GPa or more and excellent wear resistance on the (111) orientation plane. However, the same effect can be obtained if the average particle diameter of the diamond polycrystal composed of a single diamond phase is 100 nm or less and the X-ray diffraction intensity ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ is 0.15 or less. It is thought that

  Next, the manufacturing method of the diamond polycrystal of this Embodiment is demonstrated. The method for producing a polycrystalline diamond according to the present embodiment includes a step (S01) of preparing pyrolytic graphite (PG) having a (002) plane as an orientation plane as a starting material (carbon raw material); A step of sintering the decomposed graphite under a pressure of 15 GPa or more and a temperature of 1500 ° C. or more and directly converting it into diamond (S02).

First, in the step (S01), the ratio I ₍₁₁₀₎ / I ₍₀₀₂₎ of the (110) plane X-ray diffraction intensity I _{(110) to} the ₍₀₀₂ ) plane X-ray diffraction intensity I ₍₀₀₂₎ is 0. Prepare pyrolytic graphite (PG) which is 01 or less. That is, PG prepared in this step (S01) exhibits orientation on the (002) plane.

  Next, in the step (02), the high orientation pyrolytic graphite (PG), which is a starting material, is converted into a polycrystalline diamond and simultaneously sintered using an ultra-high pressure and high temperature generator. Sintering is performed under conditions of a pressure of 15 GPa or more and a temperature of 1500 ° C. or more. Thereby, a diamond polycrystal having the (111) plane as an orientation plane can be obtained. The diamond polycrystalline body has a diamond single-phase structure substantially free of a binder, a sintering aid, a catalyst, and the like, and can have an average particle size of about 100 nm or less. In the sintering conditions, the upper limit values of pressure and temperature may be any value as long as diamond is thermodynamically stable, and the upper limit values of pressure and temperature are actually determined by the ultrahigh pressure and high temperature generator to be used. For example, the upper limit for industrially stable production is a pressure of about 30 GP and a temperature of about 3000 ° C.

  From the examples described later, in the step (S02), the obtained polycrystalline diamond has a (111) orientation plane under sintering conditions of a pressure of 16 GPa or more and a temperature of about 2000 ° C. or more, and the (111) orientation. It was confirmed that the Knoop hardness of the surface at room temperature was 140 GPa. Moreover, it was confirmed that the (111) -oriented surface of the polycrystalline diamond was excellent in wear resistance. However, it is considered that a polycrystalline diamond having similar characteristics can be obtained even under sintering conditions of a pressure of about 15 GPa or more and 1500 ° C. or more.

  As described above, the polycrystalline diamond according to the present embodiment has a single-phase diamond structure and has an average particle size of about 100 nm or less. For this reason, the diamond polycrystalline body has excellent hardness characteristics because the crystal grains are directly bonded to each other and has a dense crystal structure with very few voids. Furthermore, since the polycrystalline diamond according to the present embodiment has a (111) -oriented surface, it is possible to utilize particularly excellent hardness characteristics and wear resistance of the (111) surface in diamond. Therefore, the Knoop hardness of the polycrystalline diamond according to the present embodiment can be 130 GPa or more.

  Further, the polycrystalline diamond according to the present embodiment can strengthen the bond between crystal grains by setting the hydrogen concentration at the crystal grain boundary to less than 100 ppm. Thereby, the Knoop hardness of the polycrystalline diamond can be increased. In addition, abnormal growth of crystal grains can be effectively suppressed, and variations in crystal grain size can be reduced.

  Furthermore, the diamond polycrystalline body of the present embodiment can be used for a tool. At this time, in the polycrystalline diamond according to the present embodiment, the tool is manufactured so that the (111) -oriented surface is in contact with the workpiece and directed to a surface with a large amount of wear, so that the tool has excellent wear resistance. be able to. As a tool, for example, it can be used in the wear dominant direction of a cutting tool or an anti-abrasion tool. FIG. 1 shows a schematic diagram of a tool in which the (111) -oriented surface of the polycrystalline diamond according to the present embodiment is applied to a surface with a large amount of wear of the cutting tool. Diamond polycrystalline body 1 is fixed to a predetermined region of base metal 2 via brazing layer 3 and metallized layer 4. At this time, if the rake face is used for a tool, the tool is manufactured so that the (111) oriented face of the polycrystalline diamond 1 constitutes the rake face 5, so that the feed amount (feed speed) is large. When cutting, it is possible to extend the cutting tool life.

  In the case of a tool application in which the flank face is more worn, the tool may be produced so that the (111) -oriented face of the polycrystalline diamond 1 faces the flank face 7. Even in this case, the amount of wear due to friction between the flank 7 and the finished surface of the workpiece can be reduced, and the life of the cutting tool can be extended.

  In the method for producing a polycrystalline diamond according to the present embodiment, the starting material has a graphite-like carbon single-phase structure, and any carbon material may be adopted as long as the (002) plane is an orientation plane. Can do. For example, pyrolytic graphite produced by a CVD method, rolled graphite sheet, or the like may be used as a starting material. Even in this way, a polycrystalline diamond having a (111) orientation plane can be produced.

  The method for producing a polycrystalline diamond according to the present embodiment uses a carbon material as an example of a step of directly converting the carbon material into diamond in a pressure and temperature range where diamond is thermodynamically stable. A process of sintering and converting directly to diamond under conditions of a pressure of 15 GPa or more and a temperature of 1500 ° C. or more is employed.

  Next, embodiments of the present invention will be described with reference to the drawings.

Diamond polycrystalline bodies according to Examples 1 and 2 were produced by the following method. First, pyrolytic graphite showing orientation on the (002) plane was prepared as a starting material (carbon raw material). FIG. 2 shows an X-ray diffraction spectrum when the pyrolytic graphite is measured by X-ray diffraction. The horizontal axis in FIG. 2 represents the diffraction angle 2θ (unit: deg), and the vertical axis represents the diffracted X-ray intensity in arbitrary units normalized by the peak intensity of the (002) plane. The pyrolytic graphite had a ratio I ₍₁₁₀₎ / I ₍₀₀₂₎ of the (110) plane X-ray diffraction intensity I _{(110) to} the (002) plane X-ray diffraction intensity I ₍₀₀₂₎ of 0. The starting material raw material was directly converted into diamond by holding it for 20 minutes under conditions of a pressure of 15 to 17 GPa and a temperature of about 2000 to 2500 ° C. using an ultrahigh pressure and high temperature generator.

The diamond polycrystals of Comparative Examples 1 and 2 were produced by the following method. First, as a starting material (carbon material), graphite produced by powder compression and annealing was prepared. The graphite had a ratio I ₍₁₁₀₎ / I ₍₀₀₂₎ of (110) plane X-ray diffraction intensity I _{(110) to} (002) plane X-ray diffraction intensity I ₍₀₀₂₎ of 0.091. The starting material was directly converted to diamond by holding it for 20 minutes under conditions of a pressure of 15 to 17 GPa and a temperature of about 2000 to 2500 ° C. using an ultrahigh pressure and high temperature generator.

  In addition, the X-ray diffraction performed in order to investigate the orientation of the said starting material used the X-ray-diffraction apparatus (X'Pert) by PHILLIPS.

  The orientation, hardness, and wear resistance of the polycrystalline diamonds of Examples 1 and 2 and Comparative Examples 1 and 2 obtained as described above were measured by the following methods.

The orientation was evaluated using the X-ray diffractometer. Specifically, the ratio I _{(220 )} of the (220) plane X-ray diffraction intensity I _{(220) to} the (111) plane X-ray diffraction intensity I ₍₁₁₁₎ of the polycrystalline diamond obtained by the X-ray diffraction method. ₎ / I ₍₁₁₁₎ was calculated.

  The hardness was determined by measuring the Knoop hardness at room temperature in the (111) orientation plane in the polycrystalline diamond. The Knoop hardness was measured using a micro Knoop indenter with a test load of 0.5 N. The measurement was carried out five times, and the average value of the three measurements obtained by removing the minimum value and the maximum value from each measurement value was taken as the hardness of the diamond polycrystal (hardness. The measuring instrument used was HM-124 manufactured by Mitutoyo. .

  The wear resistance was evaluated by a wear test on the (111) plane. In the wear test, a diamond polycrystal processed to φ2.0 was slid with a metal bond diamond grindstone at a load of 2 kgf and a speed of 30 m / s to wear the (111) surface of the diamond polycrystal. The amount of wear was compared.

Table 1 shows the results of the X-ray diffraction intensity ratios I ₍₂₂₀₎ / I ₍₁₁₁₎ , hardness, and wear resistance of the polycrystalline diamonds of Examples 1 and 2 and Comparative Examples 1 and 2. FIG. 3 shows an X-ray diffraction spectrum of the polycrystalline diamond of Example 1. The horizontal axis in FIG. 3 represents the diffraction angle 2θ (unit: deg), and the vertical axis represents the diffracted X-ray intensity in arbitrary units normalized by the peak intensity of the (111) plane. The wear resistance was evaluated at the time when the wear amount reached 100 μm. The wear resistance of the diamond polycrystalline body of Comparative Example 2 is taken as 1, and the ratio to this is shown in Table 1.

As shown in Table 1, in Examples 1 and 2, the ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ of the X-ray diffraction intensity I _{(220 )} was 0.04 to 0.13. Furthermore, the Knoop hardness at room temperature in the (111) orientation planes of Examples 1 and 2 was 155 to 180 GPa. Referring to FIG. 3, the polycrystalline diamond of Example 1 exhibits high orientation on the (111) plane.

On the other hand, in Comparative Examples 1 and 2, the ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ of the X-ray diffraction intensity I _{(220 )} was 0.19 to 0.23. That is, the diamond polycrystals of Comparative Examples 1 and 2 were isotropic with no orientation on any face. Since Comparative Examples 1 and 2 are isotropic, the Knoop hardness at room temperature was measured on a randomly selected surface, which was 125 to 128 GPa.

  Furthermore, Examples 1 and 2 were 1.5 to 2.1 times longer in life than Comparative Example 2, and were more excellent in wear resistance than Comparative Examples 1 and 2. That is, the diamond polycrystals of Examples 1 and 2 have improved wear resistance compared to the diamond polycrystals of Comparative Examples 1 and 2 by making the (111) -oriented surface wear. confirmed.

  Although the embodiments and examples of the present invention have been described above, various modifications can be made to the above-described embodiments and examples. Further, the scope of the present invention is not limited to the above-described embodiments and examples. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The polycrystalline diamond according to the present invention, the production method thereof, and the tool are particularly advantageously applied to tool members and tools that require unidirectional wear resistance.

  1 diamond polycrystal, 2 base metal, 3 brazing layer, 4 metallized layer, 5 rake face, 7 flank face.

Claims (6)

A diamond polycrystal having a diamond single phase structure,
The ratio I ₍₂₂₀₎ / I _{(111 )} of the X-ray diffraction intensity I ₍₂₂₀₎ of the (220) plane of the diamond polycrystal to the X-ray diffraction intensity I ₍₁₁₁₎ of the (111) plane of the polycrystalline diamond. ₎ Is 0.15 or less, and the hydrogen concentration at the crystal grain boundary of the polycrystalline diamond is less than 100 ppm.   The diamond polycrystalline body according to claim 1, wherein an average particle diameter of the polycrystalline diamond is 100 nm or less.   The diamond polycrystal according to claim 1 or 2, wherein the diamond polycrystal has a Knoop hardness of 130 GPa or more.   A tool provided with the polycrystalline diamond according to any one of claims 1 to 3. A step of preparing a carbon material made of graphite-like carbon and having orientation on the (002) plane;
The carbon material is sintered under conditions of a pressure of 15 to 30 GPa and a temperature of 1500 to 3000 ° C. and directly converted into diamond,
In the carbon material, the ratio I ₍₁₁₀₎ / I ₍₀₀₂₎ of the (110) plane X-ray diffraction intensity I _{(110) to} the ₍₀₀₂ ) plane X-ray diffraction intensity I ₍₀₀₂₎ is 0.01 or less. The said polycrystalline diamond manufacturing method of any one of the said Claims 1-3 which exists . A step of preparing a carbon material made of graphite-like carbon and having orientation on the (002) plane;
The carbon material is sintered under conditions of a pressure of 15 to 30 GPa and a temperature of 1500 to 3000 ° C. and directly converted into diamond,
In the carbon material, the ratio I ₍₁₁₀₎ / I ₍₀₀₂₎ of the (110) plane X-ray diffraction intensity I _{(110) to} the ₍₀₀₂ ) plane X-ray diffraction intensity I ₍₀₀₂₎ is 0.01 or less. Yes,
The said carbon material is a manufacturing method of the said diamond polycrystal of any one of Claims 1-3 which is pyrolytic graphite.

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