JP6863092B2 - Polycrystalline diamond and its manufacturing method, scribing tool, scribing wheel, dresser, rotary tool, water jet orifice, wire drawing die, cutting tool, electrode and processing method using polycrystalline diamond - Google Patents

Description

The present invention relates to polycrystalline diamond and a method for producing the same. The polycrystalline diamond according to the present invention is suitably used for scribing tools, scribing wheels, dressers, rotary tools, water jet orifices, wire drawing dies, cutting tools, electrodes and the like. Furthermore, the present invention relates to a processing method using polycrystalline diamond.

In recent years, it has become clear that nano-polycrystalline diamond (hereinafter sometimes referred to as “NPD”) has an isotropic hardness that exceeds that of natural single crystal diamond. Nanopolycrystalline diamonds having been imparted with conductivity by adding a boron compound to such a material have been developed. Further, by incorporating boron in diamond crystal grains in an atomic substitution type, nanopolycrystalline diamond exhibiting semiconductor characteristics based on a diamond structure has been developed.

For example, in Japanese Patent Application Laid-Open No. 2012-106925 (Patent Document 1), a diamond polycrystal containing a boron compound as an impurity and having a protective film of boron oxide formed on the surface by heating in the air to improve oxidation resistance. The body is proposed. In JP2013-028500 (Patent Document 2), since the Group 3 element of the periodic table is contained in the diamond crystal grains in the atomic substitution type, it has p-type conductivity without containing a boron compound. Nanopolycrystalline diamond has been proposed.

Japanese Unexamined Patent Publication No. 2012-106925 Japanese Unexamined Patent Publication No. 2013-028500

However, the diamond polycrystalline body disclosed in Patent Document 1 has a reduced hardness because the boron compound is not contained in the crystal lattice of diamond, and cracks occur at a high temperature because the coefficient of thermal expansion of the boron compound and diamond is different. It tended to occur, and there was room for improvement in these respects. Since the nano-polycrystalline diamond disclosed in Patent Document 2 is oxidized when a work material such as a ceramic or a resin containing oxygen is processed, there is room for improvement in oxidation resistance.

Further, in the conventional nano-polycrystalline diamond, triboplasma is generated between the work material and the work material when the insulating work material is processed, and both the NPD and the work material tend to be worn out. Further, since the protective film of boron oxide is water-soluble, the protective effect could not be exhibited when an aqueous solution-based cutting fluid was used. Therefore, there is a demand for nano-polycrystalline diamond that can suppress the occurrence of triboplasm while suppressing the decrease in hardness and the occurrence of cracks, and has a water-insoluble protective film formed.

The present invention has been proposed in view of the above circumstances, and a polycrystalline diamond having a water-insoluble protective film formed while suppressing the generation of triboplasma, a method for producing the same, a scribing tool formed using the polycrystalline diamond, and a scribing. It is an object of the present invention to provide a wheel, a dresser, a rotary tool, an orifice for a water jet, a wire drawing die, a cutting tool and an electrode, and a processing method using the above-mentioned polycrystalline diamond.

The polycrystalline diamond according to one aspect of the present invention is a polycrystalline diamond having a diamond single phase as a basic composition, the polycrystalline diamond is composed of a plurality of crystal grains, and the polycrystalline diamond is composed of boron and boron. It contains nitrogen, a nitrogen compound, and silicon, and the balance is carbon and trace impurities. Boron is dispersed in the crystal grains at the atomic level, and 90 atomic% or more of the whole exists as an isolated substitution type. However, the nitrogen, the nitrogen compound and the silicon are present in the crystal grains as isolated substitution type or invasion type, and the nitrogen compound is both boron nitride and silicon nitride, or one of the crystal grains. Has a particle size of 500 nm or less, and the surface of the polycrystalline diamond is coated with a protective film.

The method for producing a polycrystalline diamond according to one aspect of the present invention includes a first step of preparing graphite containing carbon, boron, nitrogen, a nitrogen compound, and silicon by thermal decomposition of polyimide, and the above graphite is not used. The second step of filling the container in an active gas atmosphere and the third step of converting the graphite into diamond by pressure heat treatment in the container include the above-mentioned boron at the atomic level in the crystal grains of the above-mentioned graphite. 90 atomic% or more of the whole is present as an isolated substitution type, and the nitrogen compound is either boron nitride and / or silicon nitride.

According to the above, it is possible to provide a polycrystalline diamond having a water-insoluble protective film formed while suppressing triboplasma and a method for producing the same.

FIG. 1 is a graph showing an example of the distribution of additive elements inside the polycrystalline diamond according to the present embodiment. FIG. 2 is a graph showing a change in the amount of tool wear of a polycrystalline diamond cutting tool with respect to a cutting distance when high-purity alumina (purity: 99.9% by mass) is used as a work material. FIG. 3 is a flowchart showing a process of a method for producing polycrystalline diamond according to the present embodiment.

[Explanation of Embodiments of the Present Invention]
First, embodiments of the present invention will be listed and described.

[1] The polycrystalline diamond according to one aspect of the present invention is a polycrystalline diamond having a diamond single phase as a basic composition, the polycrystalline diamond is composed of a plurality of crystal grains, and the polycrystalline diamond is composed of a plurality of crystal grains. It contains boron, nitrogen, a nitrogen compound, and silicon, and the balance is carbon and trace impurities. The boron is dispersed in the crystal grains at the atomic level, and 90 atomic% or more of the whole is isolated and substituted. Existing as a type, the nitrogen, the nitrogen compound and the silicon are present in the crystallites as an isolated substitution type or an interpenetrating type, and the nitrogen compound is either boron nitride and / or silicon nitride. The crystal grains have a particle size of 500 nm or less, and the surface of the polycrystalline diamond is coated with a protective film. With such a configuration, polycrystalline diamond can form a water-insoluble protective film while suppressing triboplasma.

[2] It is preferable that 99 atomic% or more of the total boron is contained in the crystal grains as an isolated substitution type. Thereby, the triboplasma can be further suppressed.

[3] The atomic concentration of the above boron is preferably 1 × 10 ¹⁴ cm ^-3 or more and 1 × 10 ²² cm ^-3 or less. Thereby, the triboplasma can be further suppressed.

[4] The total concentration of both the nitrogen and the nitrogen in the nitrogen compound is preferably 1 × 10 ¹⁸ cm ^-3 or more and 1 × 10 ²⁰ cm ^-3 or less as the atomic concentration in the polycrystalline diamond. .. Thereby, a water-insoluble protective film can be formed.

[5] The atomic concentration of the silicon is preferably 1 × 10 ¹⁸ cm ^-3 or more and 2 × 10 ²⁰ cm ^-3 or less. Thereby, a water-insoluble protective film can be further formed.

[6] the polycrystalline diamond in the Raman spectrum measurement, the area of the peak half width is 20 cm ^-1 or less about the 1575 cm ^-1 ± 30 cm ^-1 is a half-value width around the 1300 cm ^-1 ± 30 cm ^-1 Is preferably less than 1% of the peak area of 60 cm ^{-1 or less.} This makes it possible to maintain an isotropic hardness that exceeds that of natural single crystal diamond.

[7] The polycrystalline diamond preferably has a coefficient of dynamic friction of 0.2 or less. This makes it suitable for processing insulating work materials such as ceramics and resins.

[8] The polycrystalline diamond preferably has a coefficient of dynamic friction of 0.1 or less. This makes it more suitable for processing insulating work materials such as ceramics and resins.

[9] The protective film preferably contains at least one selected from the group consisting of silicon oxide, silicon nitride and boron nitride. Since these protective films are water-insoluble protective films, they can exert a protective effect against an aqueous solution-based cutting fluid when used in a tool or the like.

[10] The protective film preferably contains precipitates precipitated from the crystal grains. Since these protective films are also water-insoluble protective films, they can exert a protective effect against an aqueous solution-based cutting fluid when used in a tool or the like.

[11] The average film thickness of the protective film is preferably 1 nm or more and 1000 nm or less. As a result, the coefficient of friction can be satisfactorily reduced.

[12] The method for producing a polycrystalline diamond according to one aspect of the present invention includes a first step of preparing graphite containing carbon, boron, nitrogen, a nitrogen compound, and silicon by thermal decomposition of polyimide, and the above. A second step of filling a container with graphite in an inert gas atmosphere and a third step of converting the graphite into diamond by pressure heat treatment in the container are included, and the boron is contained in the crystal grains of the graphite. It is dispersed at the atomic level, and 90 atomic% or more of the whole exists as an isolated substitution type, and the nitrogen compound is either boron nitride and / or silicon nitride. With such a configuration, it is possible to produce polycrystalline diamond having a water-insoluble protective film formed while suppressing triboplasma.

[13] The first step preferably includes a step of preparing the polyimide. This makes it possible to efficiently produce polycrystalline diamond having a water-insoluble protective film formed while suppressing triboplasma.

[14] The first step is preferably a step of preparing the graphite by molding the polyimide and thermally decomposing it at 800 to 2500 ° C. after the step of preparing the polyimide. This makes it possible to more efficiently produce polycrystalline diamond having a water-insoluble protective film formed while suppressing triboplasma by thermal decomposition of polyimide.

[15] In the step of preparing the above-mentioned polyimide, tetracarboxylic acid dianhydride, diamine, one selected from the group consisting of propenylboronic acid, dimethylamine borane and trisdimethylaminoborane, and tris (dimethylamino) silane. To obtain a mixture by mixing the above in an organic solvent, to react the mixture at 70 to 90 ° C. to obtain a reactant, and to heat the reactant at 200 ° C. or higher and to the reaction product. It is preferable to include the step of obtaining the polyimide by performing imidization and dehydration. As a result, a polyimide suitable for producing polycrystalline diamond can be produced, so that polycrystalline diamond having a water-insoluble protective film formed can be produced more efficiently while suppressing triboplasma.

[16] The mixture preferably further contains boranetriyltris iminotris [tris (dimethylamino) silane]. As a result, it is possible to produce a polyimide more suitable for producing polycrystalline diamond, so that it is possible to more efficiently produce polycrystalline diamond having a water-insoluble protective film formed while suppressing triboplasma. ..

[17] The step of preparing the polyimide preferably includes a step of adding graphene after obtaining the mixture and before obtaining the reaction product. This makes it possible to more efficiently produce polycrystalline diamond having a water-insoluble protective film formed while suppressing triboplasma.

[18] The method for producing a polycrystalline diamond further includes a fourth step performed after the first step and before the second step, and the fourth step includes steps A, B and C. The steps are repeated a plurality of times in this order, the step A is a step of crushing the graphite into a crushed body, the step B is a step of molding the crushed body into a molded body, and the step C is described. Is a step of preparing the graphite again by thermally decomposing the molded product at 1500 to 1800 ° C. This makes it possible to avoid contamination of impurities such as _{B 4 C as much as possible.}

[19] In the third step, it is preferable to directly heat-treat the graphite in a pressure heat treatment device. As a result, polycrystalline diamond having a diamond single phase as a basic composition can be produced without containing a bonded phase (binder) made of cobalt or the like.

[20] The pressure heat treatment is preferably performed under the conditions of 6 GPa or more and 1200 ° C. or more. This makes it possible to efficiently produce polycrystalline diamond having the above effects.

[21] The pressure heat treatment is preferably performed under the conditions of 8 GPa or more and 30 GPa or less and 1500 ° C. or more and 2300 ° C. or less. This makes it possible to more efficiently produce polycrystalline diamond having the above effects.

[22] One aspect of the present invention is preferably a scribe tool formed using the above-mentioned polycrystalline diamond. This makes it possible to provide a scribe tool using polycrystalline diamond on which a water-insoluble protective film is formed while suppressing triboplasma.

[23] One aspect of the present invention is preferably a scribe wheel formed by using the above-mentioned polycrystalline diamond. This makes it possible to provide a scribe tool using polycrystalline diamond on which a water-insoluble protective film is formed while suppressing triboplasma.

[24] One aspect of the present invention is preferably a dresser formed using the above-mentioned polycrystalline diamond. This makes it possible to provide a dresser using polycrystalline diamond on which a water-insoluble protective film is formed while suppressing triboplasma.

[25] One aspect of the present invention is preferably a rotary tool formed by using the above-mentioned polycrystalline diamond. This makes it possible to provide a rotary tool using polycrystalline diamond on which a water-insoluble protective film is formed while suppressing triboplasma.

[26] One aspect of the present invention is preferably an orifice for a water jet formed by using the above-mentioned polycrystalline diamond. This makes it possible to provide an orifice for a water jet using polycrystalline diamond on which a water-insoluble protective film is formed while suppressing triboplasma.

[27] One aspect of the present invention is preferably a wire drawing die formed by using the above-mentioned polycrystalline diamond. This makes it possible to provide a wire drawing die using polycrystalline diamond on which a water-insoluble protective film is formed while suppressing triboplasma.

[28] One aspect of the present invention is preferably a cutting tool formed by using the above-mentioned polycrystalline diamond. This makes it possible to provide a cutting tool using polycrystalline diamond on which a water-insoluble protective film is formed while suppressing triboplasma.

[29] One aspect of the present invention is preferably an electrode formed by using the above-mentioned polycrystalline diamond. This makes it possible to provide an electrode using polycrystalline diamond on which a water-insoluble protective film is formed while suppressing triboplasma.

[30] The processing method according to one aspect of the present invention is preferably a processing method for processing an object using the above-mentioned polycrystalline diamond. Thereby, the object can be processed by using the polycrystalline diamond on which the water-insoluble protective film is formed while suppressing the triboplasma.

[31] The object is preferably an insulator. As a result, the effect of suppressing the triboplasma contained in polycrystalline diamond can be suitably exhibited.

[32] The insulator preferably has a resistivity of 100 kΩ · cm or more. Thereby, the effect of suppressing the triboplasma contained in the polycrystalline diamond can be more preferably exhibited.

[Details of Embodiments of the present invention]
Hereinafter, embodiments of the present invention will be described in more detail. Here, in the present specification, the notation in the form of "A to B" means the upper and lower limits of the range (that is, A or more and B or less), and there is no description of the unit in A, and the unit is described only in B. In the case, the unit of A and the unit of B are the same.

Furthermore, when a compound or the like is represented by a chemical formula in the present specification, it shall include all conventionally known atomic ratios when the atomic ratio is not particularly limited, and is not necessarily limited to those in the stoichiometric range. For example, when "SiN" is described, the ratio of the number of atoms constituting SiN is not limited to, for example, Si: N = 1: 1 of SiN, and includes all conventionally known atomic ratios. This also applies to the description of compounds other than "SiN". In the present embodiment, the metalloid elements such as boron (B) and silicon (Si) and the non-metal elements such as nitrogen (N) and carbon (C) necessarily constitute a stoichiometric composition. No need.

≪Polycrystalline diamond≫
The polycrystalline diamond according to the present embodiment has a diamond single phase as a basic composition and is composed of a plurality of crystal grains. Further, polycrystalline diamond contains boron, nitrogen, a nitrogen compound, silicon, and the balance is carbon and trace impurities. Boron is dispersed in crystal grains at the atomic level, and 90 atomic% or more of the total is present as an isolated substitution type. Nitrogen, nitrogen compounds and silicon are present in the crystal grains as isolated substitution type or invasion type. The nitrogen compound is either boron nitride and / or silicon nitride. The polycrystalline diamond has a particle size of 500 nm or less. Further, it is preferable that the surface thereof is covered with a protective film.

Since the polycrystalline diamond according to the present embodiment has a diamond single phase as a basic composition, it does not contain a bonding phase (binder) formed by a sintering aid and / or a catalyst, and is under high temperature conditions. Even underneath, bleaching does not occur due to the difference in thermal expansion rate. Furthermore, polycrystalline diamond is a polycrystalline diamond composed of a plurality of crystal grains, and since its particle size is 500 nm or less, it does not have the directional and cleavage properties of a single crystal, and is anisotropic to all directions. Has anisotropic hardness and abrasion resistance. Since polycrystalline diamond contains boron, nitrogen, a nitrogen compound, and silicon in the crystal grains, its surface is coated with a water-insoluble protective film. As a result, the oxidation resistance becomes high, and the sliding characteristics and the wear resistance become high due to the reduction of the friction coefficient.

From the viewpoint of having isotropic hardness and abrasion resistance in all directions, the maximum particle size of polycrystalline diamond (the largest of the crystals constituting polycrystalline diamond) is 500 nm or less. .. The maximum particle size of polycrystalline diamond is preferably 200 nm or less. On the other hand, the minimum particle size of polycrystalline diamond may be 1 nm or more.

When the particle size of polycrystalline diamond is 500 nm or less, the effect of having isotropic hardness can be obtained. Further, when it is 1 nm or more, the effect of having the mechanical strength peculiar to diamond can be obtained. The particle size of polycrystalline diamond is more preferably 20 nm or more and 200 nm or less. In addition, the aspect ratio of the major axis a and the minor axis b of each particle is more preferably a / b <4.

The particle size of polycrystalline diamond can be measured by electron microscopy such as SEM and TEM. By polishing any surface of polycrystalline diamond, an observation polishing surface for measuring the particle size is prepared, and at any one place of the above observation polishing surface at a magnification of 20000 times using, for example, SEM. Observe (1 field). Since about 120 to 200,000 crystal grains of polycrystalline diamond appear in one field of view, the particle size of 10 of them is obtained, and it is confirmed that all of them are 500 nm or less. By doing this for the entire field of view over the entire size of the sample, it can be confirmed that the grain size of the polycrystalline diamond is 500 nm or less.

The particle size of polycrystalline diamond can also be measured from the half width of the (111) peak by the X-ray diffraction method (XRD method) based on the following conditions.
Measuring device: Product name (product number) "X'pert", PANalytical X-ray light source: Cu-Kα ray (wavelength 1.54185 Å)
Scanning axis: 2θ
Scanning range: 20 ° to 120 °
Voltage: 40kV
Current: 30mA
Scan speed: 1 ° / min.
The full width at half maximum is obtained from the Scherrer equation (D = Kλ / Bcosθ) after peak fitting. Here, D is the crystal grain size of diamond, B is the diffraction line width, λ is the wavelength of X-rays, θ is each Bragg, and K is a correction coefficient (0.9) determined from the correlation with the SEM image.

<Elements in crystal grains>
Polycrystalline diamond contains boron, nitrogen, nitrogen compounds, and silicon, with the balance being carbon and trace impurities. Boron is dispersed at the atomic level in the crystal grains of polycrystalline diamond, and 90 atomic% or more of the total is present as an isolated substitution type. Nitrogen, nitrogen compounds and silicon are present in the crystal grains of polycrystalline diamond as isolated substitutions or invasions. From these facts, the protective film proceeds by the reaction from the inside of the polycrystalline diamond with at least one of boron, nitrogen, nitrogen compound and silicon exposed on the surface, and the reaction between these elements and oxygen in the atmosphere. Is formed and the surface of the polycrystalline diamond is coated with its protective film. This protective film enhances the oxidation resistance of polycrystalline diamond, and the protective film reduces the coefficient of friction, thus enhancing sliding properties and wear resistance. In the present embodiment, the protective film may contain a precipitate formed by depositing on the surface of the polycrystalline diamond from the inside.

In polycrystalline diamond, boron is dispersed at the atomic level, and 90 atomic% or more of the whole exists as an isolated substitution type. Therefore, when the surface is worn, the exposed boron is oxidized and only the surface thereof is oxidized. A protective film is formed on the inside, that is, the diamond structure in each crystal grain is maintained. Boron does not aggregate in clusters in the crystal grains of polycrystalline diamond and does not aggregate at the grain boundaries of polycrystalline diamond, so impurity segregation that becomes the starting point of cracks due to temperature changes and impact occurs. Absent. Further, in addition to having conductivity, the surface energy of polycrystalline diamond is lowered by the protective film on the surface thereof, and electrons are easily attracted to the inside, which contributes to the suppression of triboplasma.

Here, in the present specification, "dispersed at the atomic level" means that different elements such as boron each have a finite activation energy (temperature-dependent electrical resistance) in the carbon constituting the crystal grains of polycrystalline diamond. Having and dispersing without changing the crystal structure of diamond, or such a level of dispersion. That is, in such a dispersed state, a dissimilar element that is isolated and precipitated is not formed, and a dissimilar compound other than diamond is not formed. "Isolated substitution type" refers to a form in which a dissimilar element or compound such as boron, nitrogen, nitrogen compound, or silicon is isolated and replaced with carbon located at a lattice point of a polycrystalline diamond or a crystal lattice of graphite. .. The "penetrating type" refers to a form in which a dissimilar element or compound such as nitrogen, a nitrogen compound, or silicon invades a gap between carbons located at a lattice point of a crystal lattice of polycrystalline diamond.

The dispersed state and present form of boron, nitrogen, nitrogen compound and silicon in the polycrystalline diamond according to the present embodiment can be observed by TEM (transmission electron microscope) or HRTEM (high resolution transmission electron microscope). It can be confirmed by TOF-SIMS (Time of Flight-Secondary Ion Mass Spectrometry) that boron is "dispersed at the atomic level" and "isolatedly substituted". The presence of nitrogen, nitrogen compounds and silicon in the "isolated" or "invasive" form can also be assessed by TOF-SIMS. The type of nitrogen compound contained in the crystal grains of polycrystalline diamond can also be observed by TEM.

The TEM used for confirming the dispersed state and the existence form is any 10 places on the polishing surface for observation at a magnification of 20000 to 100,000 times that of the polishing surface for observation for measuring the particle size of the polycrystalline diamond described above. It can be confirmed by observing (10 fields).

As for boron, 90 atomic% or more of the whole is present as an isolated substitution type in the crystal grains of polycrystalline diamond, and preferably 95 atomic% or more of the whole is present as an isolated substitution type. More preferably, 99 atomic% or more of boron is present as an isolated substitution type in the crystal grains of polycrystalline diamond, and most preferably 100 atomic% of the whole is present as an isolated substitution type. The ratio of isolated-substituted boron to the total boron in polycrystalline diamond grains can be measured by electrical conductivity characteristics and CV measurement. Boron is more than cubic boron nitride, which has a Knoop hardness of about 50 GPa, and Ib-type diamond single crystal, which has a Knoop hardness of about 90 GPa, because 90 atomic% or more of the total is present in the polycrystalline diamond crystal grains in an isolated substitution type. Has high hardness. For this reason, polycrystalline diamond is sufficiently useful in applications where wear resistance is utilized (for example, for dies, scribing tools, etc.). When the ratio of isolated-substituted boron to the total boron in polycrystalline diamond grains is less than 90 atomic%, the agglomerated boron does not have a diamond structure and becomes a starting point of fracture, which tends to cause cracks and cracks. is there.

(Atomic concentration of boron)
^{Boron has an atomic concentration of 1 × 10 14} cm ^-3 or more and 1 × 10 ²² cm ^-3 or less from the viewpoint of forming a suitable protective film on the surface of polycrystalline diamond and having a particle size of 500 nm or less. It is preferably 1 × 10 ¹⁴ cm ^-3 or more, and more ^{preferably 1 × 10 21} cm ^-3 or less. When the atomic concentration of boron is more preferable, the defective rate of the protective film is drastically reduced, and the yield is improved from 30% or more to 90% or more as compared with the atomic concentration of boron which is preferable. The atomic concentration of boron is preferably ^{1 × 10 14} cm ^-3 or more and 1 × 10 ²² cm ^-3 or less from the viewpoint of imparting conductivity that suppresses triboplasma.

Polycrystalline diamond is the atomic concentration of boron is less than 1 × 10 ¹⁹ cm ^-3 shows the electrical characteristics of the p-type semiconductor, showing the electrical characteristics of the metallic conductors in 1 × 10 ¹⁹ cm ^-3 or more. Therefore, the atomic concentration of boron is more preferably ^{1 × 10 18} cm ^-3 or more and 1 × 10 ²⁰ cm ^{-3 or less.}

When the atomic concentration of boron is 1 × 10 ¹⁴ cm ^-3 or more, the effect of suppressing triboplasma is obtained, and when it is 1 × 10 ²² cm ^-3 or less, the effect of suppressing the shedding of crystal grains is obtained. can get.

(Atomic concentration of nitrogen)
Nitrogen is contained in nitrogen and nitrogen compounds from the viewpoint that nitrogen is stably contained in the crystal grains and a water-insoluble protective film is preferably formed on the surface, and the decrease in hardness and the increase in particle size can be suppressed. the total concentration of nitrogen, 1 × 10 ¹⁸ preferably cm ^-3 to 1 × is 10 ²⁰ cm ^-3 or less as atomic concentration in the polycrystalline diamond, 1 × 10 ¹⁸ cm ^-3 to 1 × 10 ¹⁹ cm ^- More preferably, it is ^{3 or less.}

When the total atomic concentration of nitrogen is 1 × 10 ¹⁸ cm ^-3 or more, the effect of forming a protective film of BN and SiN on the surface is obtained, and it is 1 × 10 ²² cm ^-3 or less. Therefore, the effect that the hardness can be maintained without agglomeration can be obtained.

The nitrogen compound contained in polycrystalline diamond is either boron nitride and / or silicon nitride. As described above, these compounds are present in the crystal grains of polycrystalline diamond as isolated substitution type or invasion type. Boron nitride and silicon nitride can form a water-insoluble protective film by precipitating on the surface of polycrystalline diamond.

(Atomic concentration of silicon)
Silicon has an atomic concentration of 1 × from the viewpoint of stably containing silicon in the crystal grains and preferably forming a water-insoluble protective film on the surface, and from the viewpoint of suppressing a decrease in hardness and an increase in particle size. It is preferably 10 ¹⁸ cm ^-3 or more and 2 × 10 ²⁰ cm ^-3 or less, and ^{more preferably 1 × 10 18} cm ^-3 or more and 1 × 10 ¹⁹ cm ^-3 or less.

When the atomic concentration of silicon is 1 × 10 ¹⁸ cm ^-3 or more, the effect of forming a protective film of SiN can be obtained, and when it is 2 × 10 ²⁰ cm ^-3 or less, it does not aggregate. The effect of maintaining hardness can be obtained.

(Concentration of trace impurities)
The trace impurities contained in polycrystalline diamond are a general term for compounds that may be contained in trace amounts in the production of polycrystalline diamond. The content (atomic concentration) of each compound contained as trace impurities is 0 cm ^-3 or more and 1 × 10 ¹⁸ cm ^-3 or less, respectively, and the total of each compound (that is, the content of trace impurities (atomic concentration)) is 0 cm. ^-3 or more 1 x 10 ²² cm ^-3 or less. Therefore, trace impurities may or may not be contained in polycrystalline diamond. Examples of trace impurities include metal elements classified as transition metal elements and compounds containing them.

The atomic concentrations of boron, nitrogen and silicon are determined by SIMS (Secondary Ion Mass Spectrometry) inside the polycrystalline diamond on the surface of the polycrystalline diamond and its vicinity (for example, the protective film and the polycrystalline diamond in the vicinity thereof). (From the surface to a depth of 100 nm) can be measured by TOF-SIMS under the above-mentioned conditions. The concentration of trace impurities formed by elements other than carbon, boron, nitrogen and silicon can also be measured by ICP-MS (inductively coupled plasma mass spectrometry).

SIMS can measure the atomic concentrations of boron, nitrogen and silicon and the atomic concentrations of trace impurities inside polycrystalline diamond, for example, by analyzing under the following conditions.
Measuring device: Product name (product number): "IMS-7f", AMETEK primary ion species: Cesium (Cs ⁺ )
Primary acceleration voltage: 15kV
Detection area: 30 (μmφ)
Measurement accuracy: ± 40% (2σ).

FIG. 1 is a graph showing an example of the distribution of additive elements inside the polycrystalline diamond according to the present embodiment. This additive element distribution is measured using SIMS. The polycrystalline diamond shown in FIG. 1 has a maximum particle size of 1 μm or less and molecules of boron, nitrogen, and a silicon compound in carbon by subjecting a raw material that finally becomes graphite in a liquid to thermal decomposition. Graphite dispersed at the level is formed and directly converted into diamond by heat treatment under pressure at 16 GPa and 2100 ° C. From FIG. 1, it is understood that the polycrystalline diamond according to the present embodiment contains boron, nitrogen and silicon in uniform concentrations from the surface to the inside.

<Identification of polycrystalline diamond in Raman spectrum measurement>
Polycrystalline diamond according to the present embodiment, in the Raman spectrum measurement, the area of the peak half width is 20 cm ^-1 or less about the 1575 cm ^-1 ± 30 cm ^-1 is half around the 1300 ^-1 ± 30 cm ^-1 It is preferably less than 1% of the peak area where the price range is 60 cm ^{-1 or less.} This area ratio is more preferably less than 0.1%, most preferably 0%. From this, it can be seen that graphite carbon is almost completely converted to diamond carbon, specifically, 99.9 atomic% or more. When the area ratio is 1% or more, the hardness of polycrystalline diamond tends to decrease. In Raman spectrum measurement, the peak having a half width of 20 cm ^{-1 or less centered on 1575 cm -1} ± 30 cm ^-1 is derived from amorphous carbon, graphite carbon or sp2 carbon. The peak with a half-value width of 60 cm ^-1 or less centered on 1300 ^{cm -1} ± 30 cm ^-1 is a peak derived from diamond carbon.

<Dynamic friction coefficient>
The polycrystalline diamond according to the present embodiment preferably has a dynamic friction coefficient of 0.2 or less, more preferably 0.1 or less, further preferably 0.05 or less, and 0.02 or less. Most preferably. As a result, polycrystalline diamond can have high sliding characteristics and high wear resistance. When the modulus of dynamic friction of the polycrystalline diamond exceeds 0.2, the polycrystalline diamond tends not to have the desired sliding characteristics and wear resistance.

The coefficient of kinetic friction of polycrystalline diamond can be measured by a pin-on-disc sliding test performed on the surface under the following conditions.
Ball material: SUS
Load: 10N
Rotation speed: 400 rpm
Sliding radius: 1.25 mm
Test time: 100 minutes Temperature: Room temperature Atmosphere: Atmosphere, Ar or mineral oil.

When the modulus of kinematic friction of polycrystalline diamond is 0.2 or less, it decreases to 0.25 times or less of the coefficient of kinematic friction of additive-free polycrystalline diamond, for example, in a dry atmosphere (for example, at 25 ° C. and relative humidity of 40% or less). .. The modulus of kinematic friction of the polycrystalline diamond according to the present embodiment is preferably 0.2 times or less of the coefficient of kinematic friction of the additive-free polycrystalline diamond. Here, the term "additive-free polycrystalline diamond" as used herein is a polycrystalline diamond in which neither boron, nitrogen nor silicon is present in the crystal grains in an isolated substitution type, and these additive elements are grains. Even if it is deposited at the boundary, its atomic concentration does not exceed ^{1 × 10 18} cm ^-3.

<Protective film>
In the polycrystalline diamond according to the present embodiment, the protective film preferably contains at least one selected from the group consisting of silicon oxide, silicon nitride and boron nitride. It is considered that silicon oxide is generated by reacting silicon exposed from the crystal grains on the surface of the crystal grains due to abrasion or the like with oxygen in the atmosphere to form a protective film on the exposed surface. It is considered that silicon nitride is generated by the nitrogen exposed from the crystal grains to the surface due to wear or the like reacting with the silicon exposed from the crystal grains to the surface to form a protective film on the exposed surface. Be done. Further, it is also conceivable that silicon nitride, which was present in the crystal grains as a nitrogen compound, precipitates on the surface thereof due to wear or the like to form a protective film. Boron nitride is also considered to be generated by the nitrogen exposed from the crystal grains to the surface due to wear or the like reacting with the boron exposed from the crystal grains to the surface to form a protective film on the exposed surface. Be done. Further, it is also conceivable that boron nitride, which was present in the crystal grains as a nitrogen compound, precipitates on the surface thereof due to abrasion or the like to form a protective film. Since both protective films have a lubricating action and a small dynamic friction coefficient, the sliding characteristics and wear resistance of polycrystalline diamond can be improved. In particular, since silicon oxide, silicon nitride, and boron nitride are all water-insoluble, they can exert a protective effect even when a water-soluble cutting fluid is used.

The protective film can contain precipitates precipitated from the crystal grains. The precipitate contains compounds such as silicon oxide, silicon nitride, and boron nitride. It is considered that compounds such as silicon oxide, silicon nitride, and boron nitride are contained in the crystal grains of polycrystalline diamond as an intrusive type, and are exposed to the surface exposed to the surface due to wear or the like to form precipitates. Since these precipitates also have a lubricating action, they contribute to the reduction of the coefficient of dynamic friction. _{Further, silicon oxide (SiO x} , for example, x = 2), silicon nitride, boron nitride, etc. generated near the surface of polycrystalline diamond may become precipitates. Boron oxide (B _x O _y , eg x = 2, Y = 3) may also be a precipitate.

Even if the particles having the maximum particle size are shed by mechanical damage, the protective film has an average film thickness of 1 nm or more and 1000 nm or less from the viewpoint of having a volume that fills the space formed by the shedding. preferable. The average film thickness of the protective film is more preferably 20 nm or more and 500 nm or less. When the average film thickness of the protective film is 1 nm or more, the minute surface roughness is flattened and the solid lubricant effect is exhibited, so that the sliding characteristics are improved. When it is 1000 nm or less, the effect that the mechanical cutting of the object to be cut by the underlying diamond works advantageously can be obtained.

Whether or not a protective film is formed on the surface of polycrystalline diamond can be confirmed by using AES (Auger electron spectroscopy). For example, polycrystalline diamond (boron concentration 3.5 × 10 ²⁰ cm ^-3 , nitrogen concentration 5 × 10 ¹⁸ cm ^-3 , silicon concentration 1 × 10 ¹⁸ cm ^-3 ) was chemically analyzed by AES from the surface. By examining the presence or absence of oxygen in the surface layer up to a depth of about 0.5 nm, the presence or absence of a protective film at room temperature can be confirmed.

Further, the average film thickness of the protective film on the surface of polycrystalline diamond can be measured by a nanosurface measuring device (trade name: "Dektk XT", manufactured by Bruker) or TEM. For example, with respect to the above-mentioned polished surface for observation for measuring the particle size of polycrystalline diamond, any 5 places (5 fields) of the polished surface for observation can be observed at a magnification of 20000 times using TEM. Measured by. However, in the above five locations, it is assumed that each visual field includes a portion that becomes the surface of the polycrystalline diamond. The thickness of the protective film portion of the polished surface for observation appearing in each visual field can be obtained for each visual field, and the average value thereof can be used as the average film thickness of the protective film.

The method for evaluating the physical properties (hardness, wear resistance and resistivity) of polycrystalline diamond according to this embodiment is as follows.

(Evaluation of hardness)
The hardness of polycrystalline diamond can be evaluated by measuring the Knoop hardness in accordance with JIS Z 2251: 2009. For example, the Knoop hardness is measured with a load of 4.9 N. In the polycrystalline diamond according to the present embodiment, boron, nitrogen, silicon and the like present in the crystal grains serve as the starting point of plastic deformation, and it is considered that the hardness is somewhat lower than that of the polycrystalline diamond without additives. However, as shown in Table 1 described later, the polycrystalline diamond according to this embodiment (for example, B-NPD-III, boron concentration 2 × 10 ¹⁹ cm ^-3 , nitrogen concentration 1 × 10 ¹⁹ cm ^-3 , silicon concentration). The Knoop hardness of 1 × 10 ¹⁸ cm ^-3 ) is equal to or higher than that of synthetic single crystal diamond (Ib type SCD).

(Evaluation of wear resistance)
Further, the wear resistance of polycrystalline diamond can be evaluated by the following method. That is, polycrystalline diamond is processed into a cylindrical processed body of 1 mm × 1 mm × 2 mm, and the number # 800 (the number (#) means the fineness of the sieve mesh, and the larger the number, the larger the number). ^{A wear test (load 2.5 kgf / mm 2} , sliding speed 200 mm / min) is performed using a metal-bonded diamond wheel that passes through the sieve to make the particles finer. At this time, the polycrystalline diamond is evaluated to have a wear rate of 0.01 ± 0.002 μm / min.

In the above wear test, mechanical wear and thermochemical wear proceed synergistically, so it is desirable to evaluate the mechanical wear characteristics and thermochemical wear characteristics, respectively, as shown below.

As an evaluation of the mechanical wear characteristics of polycrystalline diamond, a low-speed long-time sliding test is performed on _{aluminum oxide (Al 2} O _{3) in which mechanical wear progresses.} For example, using polycrystalline diamond, a test piece having a truncated cone shape with a tip test surface having a diameter of 0.3 mm is prepared. _{Next, this test piece is pressed against an Al 2} O ₃ sintered body (purity: 99.9% by mass) with a constant load of 0.3 MPa by a machining center, and slid at a low speed of 5 m / min for a distance of 10 km. Therefore, the amount of wear is calculated from the spread of the tip diameter, and the mechanical wear characteristics of the polycrystalline diamond are evaluated. The amount of wear of the polycrystalline diamond according to the present embodiment is about 20 times that of the polycrystalline diamond without additives, and the wear resistance is significantly improved. It is considered that the protective film formed on the surface is updated one after another due to the wear of the polycrystalline diamond, the sliding characteristics are greatly improved by the lubrication effect each time, and the mechanical wear is remarkably suppressed.

As an evaluation of the thermochemical wear characteristics of polycrystalline diamond, a sliding test is performed on _{silicon dioxide (SiO 2) in which thermochemical wear progresses.} For example, using polycrystalline diamond, a test piece having a truncated cone shape with a tip test surface having a diameter of 0.3 mm is prepared. Next, this test piece is fixed and pressed against the test surface at 0.1 MPa while rotating at 6000 rpm (sliding speed 260 to 340 m / min) _{using synthetic quartz (SiO 2) having a diameter of 20 mm as a polishing machine.} As a result, the test piece is slid and the rate at which wear progresses (wear rate) is measured to evaluate the thermochemical wear characteristics of polycrystalline diamond. Polycrystalline diamond has a lower wear rate and improved wear resistance as compared with additive-free polycrystalline diamond. It is considered that the protective film formed on the surface is updated one after another due to the wear of the polycrystalline diamond, the sliding characteristics are greatly improved by the lubrication effect each time, and the mechanical wear is remarkably suppressed.

The conductivity of polycrystalline diamond can be evaluated by measuring the resistivity by the following method. That is, the surface of polycrystalline diamond is mirror-processed, and the resistivity of this processed body is measured by the four-terminal method using electrodes. This electrode is formed by annealing a Ti / Pt / Au laminated film in Ar at 320 ° C. In the present embodiment, it is preferable to prepare five of the above-mentioned processed bodies, calculate an average value from the resistivity of these processed bodies, and use this average value as the resistivity of polycrystalline diamond.

From the above, the polycrystalline diamond according to the present embodiment has a water-insoluble protective film formed on its surface, and the protective film can improve oxidation resistance, wear resistance and sliding characteristics. Furthermore, since it has conductivity, abnormal wear due to triboplasma found in additive-free polycrystalline diamond, single crystal diamond, etc. is also suppressed. Therefore, it is suitable for processing difficult-to-cut materials such as cemented carbide and aluminum alloy, and can exhibit high performance for processing insulating objects such as ceramics, plastics, glass, and quartz. .. In particular, since silicon oxide, silicon nitride, and boron nitride that constitute the protective film are all water-insoluble, the protective effect can be exhibited even when a water-soluble cutting fluid is used.

≪Manufacturing method of polycrystalline diamond≫
In the method for producing polycrystalline diamond according to the present embodiment, as shown in FIG. 3, the first step S10 prepares graphite containing carbon, boron, nitrogen, a nitrogen compound, and silicon by thermal decomposition of polyimide. A second step S20 in which the graphite is placed in a container under an inert gas atmosphere, and a third step S30 in which the graphite is converted into diamond by pressure heat treatment in the container are included. Boron is dispersed in graphite crystal grains at the atomic level, and 90 atomic% or more of the total is present as an isolated substitution type. The nitrogen compound is either boron nitride and / or silicon nitride. With the above configuration, polycrystalline diamond having high oxidation resistance, sliding characteristics and wear resistance, and a low coefficient of friction can be produced.

<First step>
The first step S10 preferably includes a step of preparing the polyimide. Any conventionally known method can be used for the step of preparing the polyimide. For example, the following multiple methods can be mentioned.

(Process to prepare polyimide)
In the first method, tetracarboxylic acid dianhydride, diamine, one selected from the group consisting of propenylboronic acid, dimethylamine borane and trisdimethylaminoborane, and tris (dimethylamino) silane are contained in an organic solvent. A step of obtaining a mixture by mixing with the above, a step of reacting the mixture at 70 to 90 ° C. to obtain a reactant, and an imide in which the reactant is heated at 200 ° C. or higher and a catalyst is used for the reactant. It is a method of preparing a polyimide including a step of obtaining a polyimide by performing conversion and dehydration.

The second method is a method of preparing a polyimide containing boranetriyltris iminotris [tris (dimethylamino) silane] in the above mixture.

The third method is a method of preparing a polyimide including a step of adding graphene after obtaining the mixture and before obtaining the reaction product.

It is preferable to use an amine compound (for example, triethylamine) as a catalyst for imidization of the above reactants. Further, it is more preferable to use a carboxylic acid anhydride in combination as a dehydrating agent for rapidly removing water generated by imidization. As the organic solvent for obtaining the mixture, methanol, ethanol, trichloroethane and the like can be used. Regardless of the first to third methods described above, graphite suitable for efficiently producing polycrystalline diamond having a water-insoluble protective film formed while suppressing triboplasma is pyrolyzed from polyimide. Can be prepared by.

Here, the boron triyltris iminotris [tris (dimethylamino) silane] mixed in the step of preparing the polyimide contains boron, nitrogen and silicon as constituent elements. The propenylboronic acid mixed in the step of preparing the polyimide contains boron as a constituent element. Dimethylamineborane and trisdimethylaminoborane, which are mixed in the step of preparing polyimide, contain nitrogen as a constituent element together with boron. The tris (dimethylamino) silane mixed in the step of preparing the polyimide contains nitrogen and silicon as constituent elements.

In the first step, after the step of preparing the polyimide, it is preferable to prepare the graphite by molding the polyimide and thermally decomposing it at 800 to 2500 ° C. As a result, boron, nitrogen, a nitrogen compound and silicon are dispersed in the crystal grains at the molecular level, and graphite having a maximum particle size of 1 μm or less can be formed by thermal decomposition of polyimide.

Further, in the first step, boron, nitrogen, a nitrogen compound and silicon are uniformly dispersed in the crystal grains at the molecular level, and graphite having a maximum particle size of 1 μm or less is stably formed in a vacuum atmosphere (less than 10 kPa). ) Is preferable.

Hereinafter, one specific example of the first step will be described. In a commercially available heat-resistant container made of stainless steel (SUS316), tetracarboxylic dianhydride, diamine, propenylboronic acid, and tris (dimethylamino) silane are mixed in an organic solvent (for example, methanol, ethanol, acetone). To obtain the mixture. By reacting this mixture at 70 to 90 ° C., a polyamic acid containing boron, nitrogen and silicon as constituent elements is obtained as a reactant. By heating this polyamic acid at 200 ° C. or higher and imidizing and dehydrating the polyamic acid in the presence of an amine compound and a carboxylic acid anhydride, a constituent element can be obtained as a precipitate in the organic solvent. To obtain a polyimide containing boron, nitrogen, and silicon (step of preparing the polyimide). Next, by molding this polyimide and thermally decomposing it at 800 to 2500 ° C., boron, nitrogen, a nitrogen compound and silicon are dispersed in the crystal grains at the molecular level, and graphite having a maximum particle size of 1 μm or less is prepared. Can be done. From the viewpoint of efficient formation of the polycrystalline diamond, graphite is preferably polycrystalline, which contains at least a partially crystallized portion.

<4th process>
Here, it is preferable that the method for producing polycrystalline diamond further includes a fourth step performed after the first step and before the second step described later. The fourth step is a step of repeating the A step, the B step, and the C step a plurality of times in this order. Step A is a step of crushing graphite into a crushed body, step B is a step of molding the crushed body into a molded body, and step C is a step of thermally decomposing the molded body at 1500 to 1800 ° C. to obtain graphite. Is the process of preparing again. By including the fourth step, the method for producing polycrystalline diamond can effectively prevent impurities such as _{B 4 C from being mixed. Whether or not B 4} C is mixed in graphite is determined by, for example, using an X-ray diffractometer (for example, trade name: "X'pert", manufactured by PANalytical), characteristic X-ray: Cu-Kα, tube voltage: 30 kV, It can be confirmed by the presence or absence of a peak derived from _{B 4} C using tube current: 20 mA, X-ray diffraction method: measured by the θ-2 θ method).

Further, the method for producing polycrystalline diamond according to the present embodiment is either after the first step and / or after the fourth step, and is as follows before the second step described later. Can include steps. That is, the graphite prepared in the first step or the fourth step is placed in a vacuum environment (less than 10 kPa), and nitrogen and / or silicon alone or nitrogen and silicon are added to the graphite. It can be introduced in a composite form.

The dispersed state and existing form of boron, nitrogen and silicon in graphite can be confirmed by the same method as the method for confirming the dispersed state and existing form of these elements in the above-mentioned polycrystalline diamond. The "dispersion at the atomic level", "isolated displacement type" or "penetration type", the concentration of boron, nitrogen and silicon, and the concentration of trace impurities are also determined by the same method as the confirmation method for polycrystalline diamond. Each can be confirmed.

The concentration of trace impurities (eg, transition metals) contained in graphite is preferably ^{below the detection limit of SIMS and ICP-MS (less than 10 15} cm ^-3). Further, the particle size of graphite is preferably 10 μm or less, preferably 1 μm or less, from the viewpoint of forming a polycrystalline diamond having a small particle size of 1 to 500 nm and a uniform distribution of boron, nitrogen and silicon. Is more preferable.

Further, the graphite has a BC ₅ concentration among the trace impurities in the range where the diffraction angle 2θ in the X-ray diffraction measurement is in the range of 0 ° to 90 ° with respect to the total area of all the diffraction peaks derived from diamond. The total area of all diffraction peaks derived from _{5 is less than 0.2%.} The concentration of BC ₅ is preferably such that the above-mentioned area ratio is less than 0.1%, and most preferably 0%. Further, _{the concentration of B 4} C is such that all the diffractions derived from _{B 4} C are compared with the total area of all the diffraction peaks derived from diamond in the range where the diffraction angle 2θ in the X-ray diffraction measurement is in the range of 0 ° to 90 °. The total area of the peak is less than 0.4%. The concentration of B ₄ C is preferably such that the above-mentioned area ratio is less than 0.2%, and most preferably 0%. The BC ₅ and B ₄ C concentrations can be measured using the above-mentioned X-ray diffractometer under the above-mentioned conditions.

The density of graphite, from the viewpoint of increasing the yield by reducing the volume change when converting the polycrystalline diamond from graphite in a third step described below, 0.8 g / cm ³ or more preferably, 1.4 g / cm ³ More preferably 2.0 g / cm ³ or less.

<Second step>
The second step is a step of filling the container with the graphite in an inert gas atmosphere. By filling a predetermined container (for example, a cell for high-pressure pressing) with graphite in an inert gas atmosphere, it is possible to prevent trace impurities from being mixed into graphite and the polycrystalline diamond produced. Here, the inert gas may be any gas that can suppress the mixing of trace impurities, and examples thereof include Ar gas, Kr gas, and He gas.

<Third step>
The third step is a step of converting the graphite into diamond by pressure heat treatment in the container. In particular, in the third step, it is preferable to directly heat-treat the graphite in a pressurizing apparatus from the viewpoint of suppressing the mixing of trace impurities into the polycrystalline diamond. Thereby, graphite can be directly converted into polycrystalline diamond, that is, without adding a sintering aid, a catalyst or the like. Pressurized heat treatment refers to heat treatment performed under pressure.

The pressure heat treatment in the third step is preferably performed under the conditions of 6 GPa or more and 1200 ° C. or more. It is more preferable that the pressure heat treatment is performed under the conditions of 8 GPa or more and 30 GPa or less and 1500 ° C. or more and 2300 ° C. or less. As a result, polycrystalline diamond in which boron is dispersed in the crystal grains at the atomic level, 90 atomic% or more of the whole is present as an isolated substitution type, and nitrogen, a nitrogen compound and silicon are present as an isolated substitution type or an interstitial type is preferable. Can be manufactured in. The pressure heat treatment has no upper limit on the pressure, but the upper limit is a condition where the temperature is 2500 ° C. When the pressure heat treatment is 6 GPa or more, graphite can be directly converted into polycrystalline diamond. Further, when the temperature is 1200 ° C. or higher, graphite can be directly converted into polycrystalline diamond. When the temperature is 2500 ° C. or lower, graphite can be directly converted into polycrystalline diamond without volatilizing each element.

From the above, the method for producing polycrystalline diamond according to the present embodiment can produce polycrystalline diamond having high oxidation resistance, sliding characteristics and wear resistance, and a low coefficient of dynamic friction. Polycrystalline diamond is produced in any shape and thickness having a diameter of about 15 × 15 t (t: sickness). For example, when the volume density of graphite ^{is about 1.8 g / cm 3} , the polycrystalline diamond shrinks to 70 to 80% of the volume of the graphite by pressure heat treatment, but the shape becomes the same as or almost the same as that of graphite. ..

<Scribe tool>
The scribe tool according to this embodiment can be produced by using the above-mentioned polycrystalline diamond.

The scribe tool according to this embodiment can be produced by a conventionally known method as long as the above-mentioned polycrystalline diamond is used.

<Scribe wheel>
The scribe wheel according to this embodiment can be manufactured by using the above-mentioned polycrystalline diamond.

The scribe wheel according to this embodiment can be manufactured by a conventionally known method as long as the above-mentioned polycrystalline diamond is used.

<Dresser>
The dresser according to this embodiment can be produced by using the above-mentioned polycrystalline diamond.

The dresser according to the present embodiment can be produced by a conventionally known method as long as the above-mentioned polycrystalline diamond is used.

<Rotating tool>
The rotary tool according to this embodiment can be manufactured by using the above-mentioned polycrystalline diamond.

The rotary tool according to this embodiment can be manufactured by a conventionally known method as long as the above-mentioned polycrystalline diamond is used.

<Orifice for water jet>
The water jet orifice according to the present embodiment can be manufactured by using the above-mentioned polycrystalline diamond.

The orifice for a water jet according to the present embodiment can be produced by a conventionally known method as long as the above-mentioned polycrystalline diamond is used.

<Drawing die>
The wire drawing die according to the present embodiment can be produced by using the above-mentioned polycrystalline diamond.

The wire drawing die according to the present embodiment can be produced by a conventionally known method as long as the above-mentioned polycrystalline diamond is used.

<Cutting tool>
The cutting tool according to this embodiment can be manufactured by using the above-mentioned polycrystalline diamond.

The cutting tool according to this embodiment can be manufactured by a conventionally known method as long as the above-mentioned polycrystalline diamond is used.

<Electrode>
The electrode according to this embodiment can be manufactured by using the above-mentioned polycrystalline diamond.

The electrode according to this embodiment can be produced by a conventionally known method as long as the above-mentioned polycrystalline diamond is used.

<Processing method>
The processing method according to the present embodiment is a method of processing an object using the above-mentioned polycrystalline diamond. Since the processing method according to the present embodiment processes the object using the above-mentioned polycrystalline diamond, the object can be processed efficiently and at low cost.

In the processing method according to the present embodiment, the object is preferably an insulator. In the processing method according to the present embodiment, since the polycrystalline diamond has conductivity, even if the object is an insulator, the object is efficiently and at low cost without causing abnormal wear due to triboplasma or the like. Can be processed.

The insulator preferably has a resistivity of 100 kΩ · cm or more. The upper limit of the resistivity of an insulator is infinity (∞). In the present embodiment, even if the object is an insulator having a resistivity of 100 kΩ · cm or more, the object can be processed efficiently and at low cost without causing etching by triboplasma.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

<Example 1: Production of polycrystalline diamond>
(Manufacturing of 4 types of polycrystalline diamond)
In Example 1, four types of polycrystalline diamonds (B-NPD-I, B-NPD-II, B-NPD-III, B-NPD-IV) used in Examples 2 to 4 described later were produced. All of these polycrystalline diamonds correspond to the examples.

(First step)
In the first step, graphite containing boron, nitrogen, a nitrogen compound and silicon was prepared by thermal decomposition of polyimide.

First, a commercially available stainless steel heat-resistant container (capacity: 500 mL) is degassed, and under a vacuum atmosphere of less than 10 kPa, 100 parts by mass of tetracarboxylic dianhydride, 100 parts by mass of diamine, and 0.4 parts by mass are used. Propenylboronic acid and 0.01 parts by mass of tris (dimethylamino) silane were mixed in an organic solvent (methanol) to obtain a mixture. To 100 parts by mass of this mixture, 1 part by mass of graphene was added and reacted at 70 to 90 ° C. to obtain polyamic acid as a reaction product.

Next, the polyamic acid is heated to 210 ° C., and the polyamic acid is imidized and dehydrated in the presence of an amine compound (methylamine) and a carboxylic acid anhydride to obtain boron and nitrogen. , A polyimide containing silicon was obtained (step of preparing the polyimide). The generated precipitate is recovered from the above container, and after molding, the polyimide is thermally decomposed at 650 ° C. in a vacuum atmosphere of less than 10 kPa, so that boron, nitrogen, nitrogen compound and silicon are molecular level in the crystal grains. To obtain graphite having a maximum particle size of 1 μm or less.

(Second step)
In the second step, graphite was stored in the container.
That is, the graphite was processed into a tablet shape and then sealed in a container (high pressure press cell: cylindrical shape of φ10 × 10t).

(Third step)
In the third step, graphite was directly converted to polycrystalline diamond.
Specifically, the graphite was directly converted into polycrystalline diamond by placing the container containing the graphite in a pressure heating device and performing a pressure heat treatment under the conditions of 16 GPa and 2100 ° C. With respect to the obtained four types of polycrystalline diamond, it was confirmed by an X-ray and electron beam diffractometer that the basic composition was a diamond single phase, no bound phase was contained, and there was no heterogeneous phase composed of _{B 4 C and the like.} Furthermore, for four types of polycrystalline diamond, it was confirmed that boron was dispersed at the atomic level and 90 atomic% or more of the total was present as an isolated substitution type, and its atomic concentration was confirmed by using TEM, SIMS and TOF-SIMS. The presence of nitrogen, nitrogen compounds and silicon as isolated substitutions or interstitial types, and the atomic concentration of nitrogen and the atomic concentration of silicon were confirmed by TOF-SIMS. The type of nitrogen compound contained in the crystal grains of polycrystalline diamond was confirmed using TEM.

Specifically, the dispersed state of boron at the atomic level by TEM and the type of nitrogen compound contained in the crystal grains of polycrystalline diamond were confirmed by a conventionally known method.

Using SIMS, the atomic concentrations of boron, nitrogen and silicon and the atomic concentrations of trace impurities inside the polycrystalline diamond were measured under the following conditions.
Measuring device: Product name (product number): "IMS-7f", AMETEK primary ion species: Cesium (Cs ⁺ )
Primary acceleration voltage: 15kV
Detection area: 30 (μmφ)
Measurement accuracy: ± 40% (2σ).

Using TOF-SIMS, it was analyzed that each element was "dispersed at the atomic level" and that each element was "isolated substitution type" or "penetrating type" under the following conditions.
Measuring device: Tof-SIMS mass spectrometer (flying time secondary ion mass spectrometer)
Primary ion source: Bismuth (Bi)
Primary acceleration voltage: 25 kV.

In addition, the resistivity and Knoop hardness (however, N = 10) were measured by the above-mentioned method, and the oxidation start temperature in the atmosphere was measured by a conventionally known method. Further, it was confirmed that the crystal grain size of the polycrystalline diamond was 500 nm or less from the half width of the (111) peak by the X-ray diffractometer (XRD). When the types and concentrations of trace impurities were measured by SIMS in the above four types of polycrystalline diamond, no transition metal element and B ₄ C were observed. The results of these measurements are shown in Table 1.

(Manufacturing of NPD and 1b type SCD, PCD)
As a comparative example, a polycrystalline diamond (NPD), an Ib-type single crystal diamond (Ib-type SCD), and diamond particles of an insulator in which boron is added in a non-isolated substitution type (penetration type) by 2 × 10 ¹⁹ cm ^-3. Sintered diamond (PCD) having a particle size of 3 to 5 μm formed by bonding with a binder containing cobalt and sintering was produced. Further, as a comparative example, polycrystalline diamond (C-NPD-I, II) was prepared from graphite having a maximum particle size of more than 10 μm when the above-mentioned first step of this example was performed. The maximum particle size of C-NPD-I and II exceeded 500 nm. For these comparative examples, the concentration of boron and the like, the type of nitrogen compound, Knoop hardness, resistivity and the like were measured by the same method as for four types of polycrystalline diamond. The results of these measurements are also shown in Table 1.

<Example 2: Abrasion resistance evaluation (thermochemical wear characteristics)>
In Example 2, using the above four types of polycrystalline diamond, 1b type SCD and NPD, a cutting tool is produced by a known manufacturing method, and a work material is a quartz glass having a Vickers hardness (Hv) of 9 GPa. It was cut as a material and its wear resistance was evaluated. The shape of the produced cutting tool is a shape classified as a general-purpose throw-away tip, and all of them have an R bite having a corner R of 0.8 mm, a clearance angle of 7 °, and a rake angle of 0 °.

In the wear resistance evaluation, the above-mentioned cutting tools are set on the ultra-precision lathe, the cutting speed (Vc) is 100 to 200 m / min (low speed condition: 100 m / min, high speed condition: 200 m / min), and the feed (f) is set. ) = 0.001 mm / rot, notch (ap) = 0.005 (low speed condition), 0.001 mm (high speed condition), measure the flank wear width Vb (unit: mm) when the work material is cut 5000 m. did. The results are shown in Table 2.

From Table 2, under low speed conditions, the amount of wear of the cutting tool using the 1b type SCD was large, and the amount of wear of the cutting tool using the four types of polycrystalline diamond and the NPD of the comparative example was about the same. Under high-speed conditions, the amount of wear was large with the cutting tool using 1b type SCD and NPD, while the amount of wear was large with B-NPD-II with the cutting tool using four types of polycrystalline diamond. In all cases, the amount of wear was extremely small. It is presumed that these are the effects of the protective film formed on the surface of the four types of polycrystalline diamond, which exerts lubricity against quartz and suppresses the reaction wear between diamond and quartz. Was done.

<Example 3: Evaluation of wear resistance (mechanical wear characteristics)>
In Example 3, B-NPD-I and B-NPD-III were used among the four types of polycrystalline diamond, and NPD and PCD were used as comparative examples to prepare a cutting tool by a known manufacturing method, respectively, and a work material was used. Was cut using a high-purity alumina sintered body (purity: 99.9% by mass) having a Vickers hardness (Hv) of 16 GPa as a work material, and wear resistance was evaluated. The shape of the produced cutting tool is a shape classified as a general-purpose throw-away tip, and all have a corner R of 0.4 mm and a clearance angle of 0 °.

In the wear resistance evaluation, the above-mentioned cutting tools were set on the ultra-precision lathe, and the maximum wear amount (VBmax (unit: μm)) with respect to the cutting distance (m) was measured under the following conditions. The results are shown in FIG. Shown.
Work Material: KYOCERA A479 φ50mm Sintered Body, Turning Cutting Conditions: Cutting Speed (Vc): 300m / min, Feed (f): 0.01mm, Cutting (ap): 0.01mm, Dry / Wet: Wet.

As shown in FIG. 2, with a cutting tool using a PCD, the cutting distance was about 600 m and the maximum wear amount exceeded 100 μm. On the other hand, with the cutting tool using NPD, the maximum wear amount did not exceed 100 μm even if the cutting distance exceeded 5000 m. Furthermore, the cutting tool using B-NPD-I shows 1.5 times higher wear resistance than NPD, and the cutting tool using B-NPD-III is 2 to 2.5 times higher than NPD. It showed high wear resistance.

<Example 4: Life evaluation by cutting an insulator>
In Example 4, a cutting tool was prepared using the above four types of polycrystalline diamond, 1b type SCD and NPD by a known manufacturing method, and the work material was cut as polycarbonate (resistivity: ∞ kΩ · cm). The life of the cutting edge was evaluated. The shape of the produced cutting tool was an R bite with a corner R of 0.8 mm, a clearance angle of 7 °, and a rake angle of 7 °.

In the life evaluation of the cutting edge in Example 4, the above-mentioned cutting tools are set on the ultra-precision lathe, cutting is performed for 4.5 km under the following conditions, and after finish cutting, the degree of damage to the cutting edge is evaluated and the damage is evaluated. The life was calculated for each cutting tool based on the degree. Specifically, the lifespan of other cutting tools was relatively evaluated when the lifespan of the cutting tool using the 1b type SCD was 1. The results are shown in Table 3.

Work Material: Polycarbonate (Takiron PCP1609A)
Cutting conditions:
(1) 4.5km cutting: Cutting speed (V): 100 to 400m / min, Feed (f): 0.04mm / rot, Cutting (ap): 0.2mm
(2) Finish cutting: Cutting speed (V): 75 m / min, feed (f): 0.002 mm / rot, depth of cut (ap): 0.002 mm, dry / wet: dry.

From Table 3, when the life of the cutting tool using the 1b type SCD is 1, the life of the cutting tool using the NPD is 1, but the life of the cutting tool using four types of polycrystalline diamond is 2.8. All of them showed a good life. The protective film formed on the surface of the four types of polycrystalline diamond and the conductivity of the four types of polycrystalline diamond suppress the wear caused by triboplasma on an insulating work material such as polycarbonate. It was presumed that the effect and the effect were due to the lubricity being exhibited and the wear being suppressed.

<Example 5: Evaluation in various tools>
(Making polycrystalline diamond)
Polycrystalline diamond (B-NPD-V to IX) used for evaluation in various tools described later is produced by the same method as in Example 1, and boron is added in a non-isolated substitution type (penetration type) by a conventionally known method. The polycrystalline diamonds (NPD-I-III) were produced. The basic composition is a single phase of diamond, boron is dispersed at the atomic level and 90 atomic% or more of the whole exists as an isolated substitution type, and nitrogen, a nitrogen compound and silicon exist as an isolated substitution type or an interstitial type. , And the method for confirming the type of nitrogen compound was the same as in Example 1. Furthermore, the atomic concentrations of carbon, boron, nitrogen and silicon, and trace impurities were measured by SIMS under the same conditions as in Example 1. Any of the above polycrystalline in diamond (B-NPD-V~IX) detects the trace impurities by SIMS B ₄ C and a transition metal element was observed.

The results of these measurements are shown in Table 4. Furthermore, it was confirmed that the crystal grain size of these polycrystalline diamonds was 30 to 60 nm from the half width of the (111) peak by the X-ray diffractometer (XRD).

(Creation and evaluation of scribe tool)
Using NPD-II and B-NPD-VI, scribe tools with 4-point tips (quadrilateral plane) were prepared, respectively. Using these scribing tools, 200 scribing grooves having a length of 50 mm were formed on the sapphire substrate at a load of 20 gf. Then, the amount of wear on the tip of the scribe tool was observed with an electron microscope. As a result, the amount of wear of the scribe tool using B-NPD-VI was extremely small, 0.1 times that of NPD-II. Similar effects were confirmed for the scribe wheels produced using NPD-II and B-NPD-VI, respectively.

(Making and evaluation of dresser)
Using NPD-II and B-NPD-VI, a single point (conical) dresser was made. These dressers were worn using a WA (white alumina) grindstone under the conditions that the peripheral speed of the grindstone was 30 m / sec, the depth of cut was 0.05 mm, and the dresser was wet. Then, the amount of wear of the dresser was measured with a height gauge meter. As a result, the amount of wear of the dresser using B-NPD-VI was extremely small, 0.1 times, as compared with that using NPD-II.

(Manufacturing and evaluation of micro rotary tools (miniature drills))
Using NPD-II and B-NPD-VI, a miniature drill having a diameter of φ1 mm and a blade length of 3 mm was produced. Using these miniature drills, a cemented carbide (WC-Co) plate with a thickness of 1.0 mm (composition: 12% by mass of Co, the balance of WC) can be used under the conditions of a rotation speed of 4000 rpm and a feed of 2 μm / time. I made a hole. The number of holes (number of drills) that could be drilled before these miniature drills were worn or damaged was evaluated. As a result, the number of drilling of the miniature drill using B-NPD-VI was 10 times higher than that using NPD-II.

<Example 6: Evaluation of cutting tool I>
In Example 6, by using the same method as in Example 1, the bulk density was 2.0 g / cm ^{3 , and the boron concentration was 1 × 10 21} cm ^-3 as measured by ICP-MS under the above-mentioned conditions. Graphite was prepared. The graphite was directly converted into polycrystalline diamond by heat-treating the graphite under pressure at 15 GPa and 2200 ° C. using an isotropic high-pressure generator. The particle size of the obtained polycrystalline diamond was 10 nm to 100 nm, respectively. From the X-ray diffraction pattern, _{no precipitation of B 4} C was observed. From the measurement under the same conditions as in Example 1 by SIMS, the silicon concentration was 1 × 10 ¹⁸ cm ^-3 and the nitrogen concentration was 2.5 × 10 ¹⁸ cm ^-3 . The boron concentration was 1 × 10 ²¹ cm ^-3 .

Using this polycrystalline diamond, a cutting tool body was produced by a conventionally known method. An active brazing material is joined to the cutting tool body in an inert atmosphere, the surface of the polycrystalline diamond is polished, and then the flank surface is cut by electric discharge machining to have a corner R of 0.4 mm, a flank angle of 11 °, and a rake angle of 0. Cutting tool I (test tool 1) with an R bite of °, and cutting tool I (test tool 1) with an R bite with a corner R of 0.4 mm, a clearance angle of 11 °, and a rake angle of 0 ° by further polishing the flank surface. Tools 2) were prepared respectively. As a comparative example, a cutting tool (comparative tool A) is manufactured by a conventionally known method using a conventional sintered diamond containing a cobalt (Co) binder, and the same electric discharge machining as the test tool 1 has the same shape as the test tool 1. R byte was given. Further, a cutting tool (comparative tool B) and a tool using Ib-type single crystal diamond (comparative tool C) are produced by a conventionally known method using additive-free polycrystalline diamond, and their flanks are used as test tools. It was processed by the same polishing as in No. 2 to give an R bite having the same shape as the test tool 2. The accuracy of the ridgeline of the cutting edge by electric discharge machining was as good as 0.5 μm or less for the test tool 1 while it was about 2 to 5 μm for the comparative tool A. The accuracy of the ridgeline of the cutting edge due to polishing was also good at 0.1 μm for the test tool 2. The test tool 1 had the same machining time as the comparison tool A.

Next, each of the test tools 1 and 2 and the comparison tools A to C was subjected to an intermittent cutting evaluation test by turning under the following conditions.

Tool shape: Corner R 0.4 mm, clearance angle 11 °, rake angle 0 °
Work Material: Material-Aluminum Alloy A390 (Shape: Diameter φ100 x 500 mm U-shaped with 4 grooves)
Machining method: Cylindrical outer circumference intermittent lathe machining (wet)
Cutting fluid: Water-soluble emulsion Cutting conditions: Cutting speed (Vc) = 800 m / min, Cutting (ap) = 0.2 mm, Feed speed (f) = 0.1 mm / rotation Cutting distance: 10 km.

After performing the above intermittent cutting evaluation test, each tool cutting edge was observed to confirm the state of wear. As a result, the comparative tool A had a large flank wear amount of 45 μm and the shape of the cutting edge was impaired, whereas the test tool 1 had a good flank wear amount of 2 μm. Further, the test tool 2 had a wear amount of 0.5 μm, which was very good as compared with the wear amount of the comparative tool B of 3.5 μm and the wear amount of the comparative tool C of 3.5 μm.

<Example 7: Evaluation of cutting tool II>
In Example 7, by using the same method as in Example 1, the bulk density was 2.0 g / cm ^{3 , and the boron concentration was 1 × 10 19} cm ^-3 as measured under the same conditions as in Example 1 by SIMS. Graphite was prepared. The graphite was directly converted into polycrystalline diamond by heat-treating the graphite under pressure at 15 GPa and 2200 ° C. using an isotropic high-pressure generator. The particle size of the obtained polycrystalline diamond was 10 nm to 100 nm, respectively. From the X-ray diffraction pattern, _{no precipitation of B 4} C was observed. From the measurement under the same conditions as in Example 1 by SIMS, the silicon concentration was 1 × 10 ¹⁸ cm ^-3 and the nitrogen concentration was 2.5 × 10 ¹⁸ cm ^-3 . The boron concentration was 1 × 10 ¹⁹ cm ^-3 .

Using this polycrystalline diamond, a cutting tool body was produced by a conventionally known method. An active brazing material is joined to the cutting tool body in an inert atmosphere, the surface of the polycrystalline diamond is polished, and then the flank surface is further polished to have a corner R of 0.4 mm, a flank angle of 11 °, and a rake angle of 0 °. A cutting tool II (test tool 3) to which the R bite of the above was applied was produced. As a comparative example, the same comparative tools A to C as those used in Example 6 were prepared. The ridgeline accuracy of the cutting edge of the test tool 3 was as good as 0.1 μm or less.

In Example 7, the test tool 3 was subjected to an intermittent cutting evaluation test under the same conditions as in Example 6. As a result, the wear amount of the test tool 3 was 0.1 μm, which was very good as compared with the wear amount of the comparative tools A to C.

<Example 8: Evaluation of cutting tool III>
In Example 8, by using the same method as in Example 1, the bulk density was 1.9 g / cm ^{3 , and the boron concentration was 1 × 10 21} cm ^-3 as measured under the same conditions as in Example 1 by SIMS. Graphite was prepared. The graphite was directly converted into polycrystalline diamond by heat-treating the graphite under pressure at 15 GPa and 2200 ° C. using an isotropic high-pressure generator. The particle size of the obtained polycrystalline diamond was 10 nm to 100 nm, respectively. The Knoop hardness was 120 GPa. A 3 mm × 1 mm square test piece was cut out from the polycrystalline diamond, and the resistivity was measured by the above-mentioned method and found to be 1 mΩ · cm. From the measurement under the same conditions as in Example 1 by SIMS, the silicon concentration was 1 × 10 ¹⁸ cm ^-3 and the nitrogen concentration was 2.5 × 10 ¹⁸ cm ^-3 . The boron concentration was 1 × 10 ²¹ cm ^-3 .

Using this polycrystalline diamond, a cutting tool body was produced by a conventionally known method. An active brazing material is joined to this cutting tool body in an inert atmosphere, the surface of polycrystalline diamond is polished, and then the flank surface is cut by electric discharge machining to have a diameter of φ0 with two twist-shaped cutting edges. A 5.5 mm ball end mill (test tool 4) was manufactured. As a comparative example, using a conventional sintered diamond containing a cobalt (Co) binder, a ball end mill (comparative tool A-2) having the same shape as the test tool 4 is machined by the same electric discharge machining as the test tool 4 to cut the flank. It was produced by Furthermore, using additive-free polycrystalline diamond, a ball end mill (comparative tool B-2) having the same shape as the test tool 4 was manufactured by cutting the flank surface by laser machining, and the cutting edge quality was locally polished. Was finished to a surface roughness Ra of 30 nm.

In Example 8, a cutting evaluation test was performed on each of the test tool 4, the comparison tool A-2, and the comparison tool B-2 under the following conditions.

Tool shape: Diameter φ0.5mm, 2-flute, ball end mill Work material: Material-STAVAX cemented carbide (WC-12 mass% Co)
Cutting fluid: White kerosene Cutting conditions: Tool rotation speed 420000 rpm, depth of cut ap = 0.003 mm, feed rate f = 120 mm / min.

When the above cutting evaluation test was performed, the tool life of the test tool 4 was 5 times the tool life of the comparison tool A-2 and 1.5 times the tool life of the comparison tool B-2, which were very good. there were. Similar effects were obtained with an aqueous solution-based cutting fluid.

<Example 9: Evaluation of orifice I for water jet>
In Example 9, by using the same method as in Example 1, the bulk density was 2.0 g / cm ^{3 , and the boron concentration was 1 × 10 19} cm ^-3 as measured by ICP-MS under the above-mentioned conditions. Graphite was prepared. The graphite was directly converted into polycrystalline diamond by heat-treating the graphite under pressure at 15 GPa and 2200 ° C. using an isotropic high-pressure generator. The maximum particle size of the obtained polycrystalline diamond was 100 nm. From the X-ray diffraction pattern, _{no precipitation of B 4} C was observed. From the measurement under the same conditions as in Example 1 by SIMS, the silicon concentration was 1 × 10 ¹⁸ cm ^-3 and the nitrogen concentration was 2.5 × 10 ¹⁸ cm ^-3 . The boron concentration was 1 × 10 ¹⁹ cm ^-3 .

Using this polycrystalline diamond, an orifice I for a water jet having an orifice hole having a diameter of φ300 μm was produced by a conventionally known method. As a comparative example, a 1b type SCD prepared by a conventionally known method was used to prepare a 1b type SCD water jet orifice having the same orifice hole as the water jet orifice I. Further, using additive-free polycrystalline diamond prepared by a conventionally known method, an additive-free polycrystalline diamond water jet orifice having the same orifice hole as the water jet orifice I was prepared.

Using these water jet orifices, the cutability was evaluated by measuring the cutting time until the orifice hole expanded to a diameter of φ350 μm under conventionally known conditions. As a result, the water jet orifice I of Example 9 had a cutting time five times as long as that of the 1b type SCD water jet orifice. In addition, it had twice the cutting time of the additive-free polycrystalline diamond water jet orifice.

<Example 10: Evaluation of orifice II for water jet>
In Example 10, by using the same method as in Example 1, the bulk density was 2.0 g / cm ^{3 , and the boron concentration was 1 × 10 19} cm ^-3 as measured by ICP-MS under the above-mentioned conditions. Graphite was prepared. The graphite was directly converted into polycrystalline diamond by heat-treating the graphite under pressure at 15 GPa and 2200 ° C. using an isotropic high-pressure generator. The maximum particle size of the obtained polycrystalline diamond was 200 nm. From the X-ray diffraction pattern, _{no precipitation of B 4} C was observed. From the measurement under the same conditions as in Example 1 by SIMS, the silicon concentration was 1 × 10 ¹⁸ cm ^-3 and the nitrogen concentration was 2.5 × 10 ¹⁸ cm ^-3 . The boron concentration was 1 × 10 ¹⁹ cm ^-3 .

Using this polycrystalline diamond, a rectangular water jet orifice having a short side of 150 μm and a long side of 300 μm was produced by a conventionally known method. As a comparative example, a PCD water jet orifice having the same shape as the water jet orifice II was prepared using a PCD prepared by a conventionally known method. Further, using additive-free polycrystalline diamond prepared by a conventionally known method, an additive-free polycrystalline diamond orifice having the same shape as the water jet orifice II was prepared.

Using these water jet orifices, the cutability was evaluated by measuring the cutting time until the long side expanded to 400 μm under conventionally known conditions. As a result, the water jet orifice II of Example 10 had a cutting time 40 times longer than that of the PCD water jet orifice. It had twice the cutting time of the additive-free polycrystalline diamond water jet orifice.

<Example 11: Performance comparison between B-NPD-III and C-NPD-I>
In this example, the performance of B-NPD-III and C-NPD-I shown in Table 1 was compared. As a result, the Knoop hardness of B-NPD-III was 110 GPa, whereas that of C-NPD-I was 75 GPa. Further, B-NPD-III was stable up to around 900 ° C. in the atmosphere, whereas C-NPD-I was oxidized and cracked at around 700 ° C.

Although the embodiments and examples of the present invention have been described above, it is planned from the beginning that the configurations of the above-described embodiments and examples are appropriately combined.

The embodiments disclosed this time should be considered to be exemplary in all respects and not restrictive. The scope of the present invention is indicated by the scope of claims rather than the above-described embodiment, and is intended to include the meaning equivalent to the scope of claims and all modifications within the scope.

S10 1st step, S20 2nd step, S30 3rd step.

Claims (28)

It is a polycrystalline diamond whose basic composition is a single-phase diamond.
The polycrystalline diamond is composed of a plurality of crystal grains.
The polycrystalline diamond contains boron, nitrogen, a nitrogen compound, and silicon, and the balance is carbon and trace impurities.
The boron is dispersed in the crystal grains at the atomic level, and 90 atomic% or more of the total is present as an isolated substitution type.
The nitrogen, the nitrogen compound and the silicon are present in the crystal grains as isolated substitution type or invasion type.
The nitrogen compound is either boron nitride and / or silicon nitride.
The crystal grains have a particle size of 500 nm or less and have a particle size of 500 nm or less.
The surface of the polycrystalline diamond is coated with a protective film .
The protective film is a polycrystalline diamond containing at least one selected from the group consisting of silicon oxide, silicon nitride and boron nitride. The polycrystalline diamond according to claim 1, wherein 99 atomic% or more of the boron is present in the crystal grains as an isolated substitution type. The polycrystalline diamond according to claim 1 or 2, wherein the boron has an atomic concentration of 1 × 10 ¹⁴ cm ^-3 or more and 1 × 10 ²² cm ^{-3 or less.} The nitrogen in the nitrogen compound and the nitrogen in the nitrogen compound are claimed from claim 1, ^{wherein the total concentration of both is 1 × 10 18} cm ^-3 or more and 1 × 10 ²⁰ cm ^{-3 or less as the atomic concentration in the polycrystalline diamond.} Item 2. The polycrystalline diamond according to any one of Item 3. The polycrystalline diamond according to any one of claims 1 to 4, wherein the silicon has an atomic concentration of 1 × 10 ¹⁸ cm ^-3 or more and 2 × 10 ²⁰ cm ^{-3 or less.} The protective layer, see containing the precipitate deposited from in the crystal grains,
The polycrystalline diamond according to any one of claims 1 to 5 , wherein the precipitate contains at least one selected from the group consisting of silicon oxide, silicon nitride, boron nitride and boron oxide. The polycrystalline diamond according to any one of claims 1 to 6 , wherein the protective film has an average film thickness of 1 nm or more and 1000 nm or less. The first step of preparing graphite containing carbon, boron, nitrogen, a nitrogen compound, and silicon by thermal decomposition of polyimide, and
The second step of filling the container with the graphite in an inert gas atmosphere, and
In the container, the third step of converting the graphite into diamond by pressure heat treatment is included.
The boron is dispersed in the crystal grains of the graphite at the atomic level, and 90 atomic% or more of the total is present as an isolated substitution type.
A method for producing polycrystalline diamond, wherein the nitrogen compound is boron nitride and / or silicon nitride. The method for producing polycrystalline diamond according to claim 8 , wherein the first step includes a step of preparing polyimide. The polycrystalline diamond according to claim 9 , wherein the first step is a step of preparing the graphite by molding the polyimide and thermally decomposing it at 800 to 2500 ° C. after the step of preparing the polyimide. Manufacturing method. In the step of preparing the polyimide, tetracarboxylic acid dianhydride, diamine, one selected from the group consisting of propenylboronic acid, dimethylamine borane and trisdimethylaminoborane, and tris (dimethylamino) silane are organic. The process of mixing in a solvent to obtain a mixture and
A step of reacting the mixture at 70 to 90 ° C. to obtain a reaction product,
The polycrystalline diamond according to claim 9 , which comprises a step of obtaining the polyimide by heating the reaction product at 200 ° C. or higher and imidizing and dehydrating the reaction product. Production method. The method for producing polycrystalline diamond according to claim 11 , wherein the step of preparing the polyimide includes a step of adding graphene after obtaining the mixture and before obtaining the reactant. The method for producing polycrystalline diamond further comprises a fourth step after the first step and before the second step.
The fourth step is a step of repeating the A step, the B step, and the C step a plurality of times in this order.
The step A is a step of pulverizing the graphite into a pulverized body.
The B step is a step of molding the pulverized body into a molded body.
The production of polycrystalline diamond according to any one of claims 8 to 12 , wherein the step C is a step of preparing the graphite again by thermally decomposing the molded product at 1500 to 1800 ° C. Method. The method for producing polycrystalline diamond according to any one of claims 8 to 13 , wherein the third step directly heat-treats the graphite with a pressure heat treatment device. The method for producing polycrystalline diamond according to any one of claims 8 to 14 , wherein the pressure heat treatment is performed under the conditions of 6 GPa or more and 1200 ° C. or more. The method for producing polycrystalline diamond according to any one of claims 8 to 15 , wherein the pressure heat treatment is performed under the conditions of 8 GPa or more and 30 GPa or less and 1500 ° C. or more and 2300 ° C. or less. A scribe tool formed by using the polycrystalline diamond according to any one of claims 1 to 7. A scribe wheel formed by using the polycrystalline diamond according to any one of claims 1 to 7. A dresser formed by using the polycrystalline diamond according to any one of claims 1 to 7. A rotary tool formed by using the polycrystalline diamond according to any one of claims 1 to 7. An orifice for a water jet formed by using the polycrystalline diamond according to any one of claims 1 to 7. A wire drawing die formed by using the polycrystalline diamond according to any one of claims 1 to 7. A cutting tool formed by using the polycrystalline diamond according to any one of claims 1 to 7. An electrode formed by using the polycrystalline diamond according to any one of claims 1 to 7. A processing method for processing an object using the polycrystalline diamond according to any one of claims 1 to 7. The processing method according to claim 25 , wherein the object is an insulator. The processing method according to claim 26 , wherein the insulator has a resistivity of 100 kΩ · cm or more. It is a polycrystalline diamond whose basic composition is a single-phase diamond.
The polycrystalline diamond is composed of a plurality of crystal grains.
The polycrystalline diamond contains boron, nitrogen, a nitrogen compound, and silicon, and the balance is carbon and trace impurities.
The boron is dispersed in the crystal grains at the atomic level, and 99 atomic% or more of the boron is present as an isolated substitution type.
The nitrogen, the nitrogen compound and the silicon are present in the crystal grains as isolated substitution type or invasion type.
The nitrogen compound is either boron nitride and / or silicon nitride.
The crystal grains have a particle size of 500 nm or less and have a particle size of 500 nm or less.
The surface of the polycrystalline diamond is coated with a protective film.
The boron has an atomic concentration of 1 × 10 ¹⁴ cm ^-3 or more and 1 × 10 ²² cm ^-3 or less.
The sum of the atomic concentrations of the nitrogen and the nitrogen in the nitrogen compound in the polycrystalline diamond is 1 × 10 ¹⁸ cm ^-3 or more and 1 × 10 ²⁰ cm ^-3 or less.
The silicon has an atomic concentration of 1 × 10 ¹⁸ cm ^-3 or more and 2 × 10 ²⁰ cm ^-3 or less .
Before Symbol protective film, silicon oxide comprises at least one member selected from the group consisting of silicon nitride and boron nitride, and wherein the precipitate deposited from in the crystal grains, said precipitates, silicon oxide, silicon nitride, Containing at least one selected from the group consisting of boron nitride and boron oxide,
The protective film is a polycrystalline diamond having an average film thickness of 1 nm or more and 1000 nm or less.

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