JP2013245126A - Polycrystalline diamond abrasive grain and method for producing the same, slurry, and fixed abrasive grain type wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide diamond abrasive grains having a longer lifetime than the lifetime of a conventional abrasive grains and a method for producing the same, slurry including the diamond abrasive grains, and fixed abrasive grain type wire.SOLUTION: Polycrystalline diamond abrasive grains consist of a polycrystalline diamond including no binder, a crystal grain size (maximum length) of the polycrystalline diamond is less than 1 μm, and an average secondary particle diameter of the polycrystalline diamond abrasive grains is 1 to 200 μm. A production method of the polycrystalline diamond abrasive grains includes a step to sinter a carbon material at a pressure of 12 GPa or more and a temperature of 1,500°C or more without using any binder to convert the carbon material directly into diamond and obtain the polycrystalline diamond having a crystal grain size of <1 μm, and a step to work the polycrystalline diamond in such a way that an average secondary particle diameter thereof gets to be 1 to 200 μm.

Description

  TECHNICAL FIELD The present invention relates to abrasive grains using polycrystalline diamond, a manufacturing method thereof, slurry, and a fixed abrasive wire, and more particularly, polycrystalline diamond abrasive grains having nano-sized crystal grains, a manufacturing method thereof, slurry, and fixing. The present invention relates to an abrasive wire.

  Conventionally, as diamond grains for polishing, those obtained by pulverizing natural diamond or artificial single crystal diamond have been used.

  Factors that affect the life and polishing performance of diamond abrasive grains include the amount of impurities, the hardness of the abrasive grains, and the cleavage property. However, it is difficult to improve the impurity amount, hardness, cleavage, etc. of natural diamond and artificial single crystal diamond. In particular, when the size of the diamond abrasive grains is as small as several μm to several tens of μm, the effect of cleavage and crystal anisotropy on the life of the abrasive grains is large, and as a result, the life tends to be limited. there were.

  On the other hand, although polycrystalline diamond is excellent in terms of cleavage, it is generally produced using a binder, a sintering aid, a catalyst, and the like, so that the amount of impurities is large and hardness characteristics at high temperatures are reduced. It is also generally known that the wear resistance decreases as the content of a binder or the like increases. For this reason, polycrystalline diamond containing a binder or the like does not have sufficient hardness characteristics and wear resistance as abrasive grains, and there is a tendency that the life of abrasive grains made of conventional polycrystalline diamond is limited. It was.

  The diamond abrasive grains are described in, for example, JP 2010-201514 A and JP 9-132771 A.

JP 2010-201514 A Japanese Patent Laid-Open No. 9-132771

  An example of the use of polycrystalline diamond abrasive grains is a wire saw in which diamond abrasive grains are fixed to a core wire. Semiconductors and the like can be cut using the wire saw, but in recent years, ingots for semiconductors have been increased in size and processing opportunities for wide gap semiconductors such as hard SiC, AlN, and GaN have increased. Yes. Accordingly, there is a demand for abrasive grains that have a longer life than conventional ones. Similar trends are seen for other uses of diamond abrasive.

  The present invention has been made in view of the problems as described above. Diamond abrasive grains having a longer lifetime than conventional abrasive grains and a method for producing the same, slurry provided with the diamond abrasive grains, and fixed abrasive wire are provided. The purpose is to provide.

  The polycrystalline diamond abrasive grain according to the present invention is made of polycrystalline diamond containing no binder. The polycrystalline diamond grain diameter is less than 1 μm, and the average secondary particle diameter of the polycrystalline diamond abrasive grain is 1 μm or more. 200 μm or less.

  Here, the “crystal grain size of the polycrystalline diamond” was measured by directly observing with a microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). , The individual single crystal particles constituting the polycrystalline diamond, that is, the outer diameter (longest part) of the primary particles.

  The “average secondary particle diameter of the polycrystalline diamond abrasive grains” means the individual polycrystalline grains constituting the measured polycrystalline diamond abrasive grains, that is, the secondary diamond grains, which are directly observed with a microscope such as SEM or TEM. The average value of outer diameter.

  The concentration of inevitable impurities in the polycrystalline diamond is preferably 0.01% by mass or less. The polycrystalline diamond abrasive can be used for slurry and fixed abrasive wire.

  In the method for producing polycrystalline diamond abrasive grains according to the present invention, a carbon material is directly converted into diamond by sintering without using a binder at a pressure of 12 GPa or higher and a temperature of 1500 ° C. or higher, and less than 1 μm. A step of obtaining polycrystalline diamond having a crystal grain size, and a step of processing the polycrystalline diamond so that the average secondary particle size is 1 μm or more and 200 μm or less.

  The carbon material is preferably prepared by a gas phase synthesis method. In the step of processing the polycrystalline diamond, the polycrystalline diamond may be pulverized by colliding a metal, ceramic, or a composite thereof with the polycrystalline diamond.

  The polycrystalline diamond abrasive grain according to the present invention is made of polycrystalline diamond containing no binder, and since the polycrystalline diamond has a crystal grain size of less than 1 μm, it can have a longer life than conventional abrasive grains. .

  In the method for producing polycrystalline diamond abrasive grains according to the present invention, the carbon material is directly converted into diamond by sintering without using a binder at a pressure of 12 GPa or higher and a temperature of 1500 ° C. or higher. Since diamond is processed, diamond abrasive grains as described above can be produced. Therefore, polycrystalline diamond abrasive grains having a longer life than conventional abrasive grains can be produced.

It is a figure which shows an example of the structure | tissue of the nano polycrystalline diamond before processing into an abrasive grain in the manufacturing method of the polycrystalline diamond abrasive grain which concerns on embodiment of this invention.

  Embodiments of the present invention will be described below. The polycrystalline diamond abrasive according to the present embodiment is made of polycrystalline diamond (primary particles; hereinafter referred to as “nanopolycrystalline diamond”) having a crystal grain size (maximum length) of less than 1 μm. The nanopolycrystalline diamond abrasive grains (secondary particles) have an average secondary particle diameter of about 1 μm or more and about 200 μm.

  The nano-polycrystalline diamond can be produced, for example, by subjecting graphite formed on a substrate by vapor phase synthesis or the like to heat treatment under high temperature and high pressure. Graphite is an integral solid and may include a crystallized portion. The nano-polycrystalline diamond and graphite may have an arbitrary shape and thickness. For example, nano-polycrystalline diamond and graphite may have a flat shape.

  The nano-polycrystalline diamond is substantially free of binders, sintering aids, catalysts and the like. The nano-polycrystalline diamond has a very small amount of impurities, crystal grains having a grain size of less than 1 μm, and is directly bonded to each other, and has a dense crystal structure with very few voids. FIG. 1 shows an example of the structure of nano-polycrystalline diamond that can be used for producing polycrystalline diamond abrasive grains according to the present embodiment. As shown in FIG. 1, in the nano-polycrystalline diamond, fine diamond crystal grains are directly bonded to each other. In addition, variations in size and shape of each crystal grain are small, and there are few voids between crystal grains.

  In addition, as long as the crystal grain diameter of nano-polycrystalline diamond is less than 1 μm, there may be some variation between the crystal grains. However, from the viewpoint of the bonding strength between the crystal grains of nano-polycrystalline diamond, it is preferable that the variation in crystal grain size is small.

  While maintaining the excellent characteristics of the nano-polycrystalline diamond, the nano-polycrystalline diamond is processed into the desired secondary particles, so that it has substantially no cleaving property, and has high hardness and wear resistance. Excellent polycrystalline diamond abrasive grains can be obtained. At this time, the average secondary particle diameter is set to a micron order. Specifically, it is preferably 1 μm or more and 200 μm or less. The average secondary particle size is set to 1 μm or more. When the average secondary particle size is smaller than 1 μm, nano-polycrystalline diamond exhibits properties like a single crystal, and can take advantage of the isotropic property of a polycrystalline body. This is because it cannot be done. The average secondary particle size is set to 200 μm or less because when the average secondary particle size is larger than 200 μm, the strength of the polycrystalline diamond abrasive grains is reduced, and at the same time, the abrasive surface is too rough. It is because it ends. The polycrystalline diamond abrasive grains may contain polycrystalline diamond abrasive grains having a secondary particle diameter of less than 1 μm or 200 μm or more as long as the average secondary particle diameter is in the range of 1 μm to 200 μm.

  The polycrystalline diamond abrasive according to the present embodiment has an impurity concentration (hereinafter referred to as “impurity concentration”) of nitrogen, hydrogen, oxygen, boron, silicon, transition metal or the like that promotes the growth of crystal grains. The content is preferably 01% by mass or less. That is, the impurity concentration is about the limit of detection in SIMS (Secondary Ion Mass Spectrometry) analysis. Moreover, about a transition metal, it is a detection limit grade in ICP (Inductively Coupled Plasma) analysis and SIMS analysis. As described above, when producing polycrystalline diamond abrasive grains using graphite, the impurity concentration of the graphite is preferably 0.01% by mass or less.

  Thus, by reducing the amount of impurities in graphite to a detection limit level in SIMS analysis and ICP analysis, when nanopolycrystalline diamond is produced using the graphite, extremely high purity nanopolycrystalline diamond Can be produced. Further, even when graphite containing impurities slightly larger than the detection limit in SIMS analysis or ICP analysis is used, polycrystalline diamond having significantly superior characteristics can be obtained compared to the conventional case.

  The high-purity nanopolycrystalline diamond has an extremely low impurity concentration throughout. Further, the nano-polycrystalline diamond does not show segregation of impurities as in the prior art, the impurity concentration in any part is extremely low, and the impurity concentration at the crystal grain boundary is about 0.01% by mass or less. . As described above, since the impurity concentration at the crystal grain boundary is extremely low, slip of the crystal grain at the crystal grain boundary can be suppressed, and the bond between the crystal grains can be strengthened. Thereby, the Knoop hardness of the polycrystalline diamond can be increased. In addition, abnormal growth of crystal grains can be effectively suppressed, and variations in crystal grain size can be reduced.

  While maintaining the excellent properties of the above-mentioned high-purity nano-polycrystalline diamond, nano-polycrystalline diamond is processed into a desired average secondary particle size, so that polycrystalline diamond abrasive grains with a longer life than conventional abrasive grains can be obtained. Can be obtained. Thereby, the polycrystalline diamond abrasive grains according to the present embodiment can have a longer life than conventional abrasive grains even when processing wide gap semiconductors such as hard SiC, AlN, and GaN.

  Next, a method for producing polycrystalline diamond abrasive grains according to the present embodiment will be described. The polycrystalline diamond abrasive according to the present embodiment directly sinters carbon material with diamond by sintering without using a binder under high temperature and high pressure (for example, pressure of 12 GPa or more, temperature of 1500 ° C. or more). The nanopolycrystalline diamond having a crystal grain size of less than 1 μm is obtained after the conversion, and then the nanopolycrystalline diamond can be processed.

  As an example of the carbon material, for example, graphite formed on a substrate by pyrolyzing a hydrocarbon gas introduced into a vacuum chamber at a temperature of about 1500 ° C. to 3000 ° C. can be given. At this time, the degree of vacuum in the vacuum chamber may be about 20 to 100 Torr. Thereby, the solid-phase graphite which is polycrystalline can be formed directly on the base material from the gas phase hydrocarbon. Further, by increasing the purity of the hydrocarbon gas, graphite with a very small amount of impurities can be produced on the substrate. For example, graphite formed on a substrate by pyrolyzing a hydrocarbon gas having a purity of 99.99% or more introduced into a vacuum chamber at a temperature of about 1500 ° C. to 3000 ° C. has an impurity concentration of 0.01 mass. % Or less. Note that methane gas is preferably used as the hydrocarbon gas.

  When producing graphite on a base material, the base material installed in the vacuum chamber is heated to a temperature of 1500 ° C. or higher. A well-known method can be adopted as the heating method. For example, it is conceivable to install a heater in the vacuum chamber that can directly or indirectly heat the substrate to a temperature of 1500 ° C. or higher.

  As a base material for producing graphite, any solid phase material may be used as long as it can withstand a temperature of about 1500 ° C. to 3000 ° C. Specifically, a metal, an inorganic ceramic material, or a carbon material can be used as a base material. From the viewpoint of suppressing impurities from being mixed into graphite, it is preferable that the substrate is made of carbon. Examples of the solid-state carbon material include diamond and graphite. When using graphite as a base material, it is preferable to use graphite with an extremely small amount of impurities prepared by the above-mentioned method as the base material.

  When a carbon material such as diamond or graphite is used as the material for the base material, at least the surface of the base material may be composed of the carbon material. For example, only the surface of the substrate may be composed of a carbon material, the remaining portion of the substrate may be composed of a material other than the carbon material, and the entire substrate may be composed of a carbon material.

  The crystal grain size of graphite as the carbon material is not particularly limited because the synthesis of the nanopolycrystalline diamond of the present embodiment is not a martensitic transformation.

  Next, the graphite produced on the substrate is sintered under conditions of a temperature of 1500 ° C. or higher and a pressure of 12 GPa or higher, and is directly converted into diamond. Thereby, nano-polycrystalline diamond substantially free of binder, sintering aid, catalyst and the like can be obtained. The nano-polycrystalline diamond has excellent hardness characteristics because the crystal grains are directly bonded to each other, and has a dense and extremely small crystal structure.

  Moreover, since the impurity concentration contained in the nanopolycrystalline diamond after conversion is approximately the same as the impurity concentration of the graphite, the impurity concentration of the graphite is preferably 0.01% by mass or less. As a result, the impurity concentration of the nano-polycrystalline diamond can be reduced to 0.01% by mass or less, and it has been found that more excellent hardness characteristics can be obtained.

  In synthesizing nanopolycrystalline diamond, uniaxial pressure may be applied or isotropic pressure may be applied. However, synthesis under hydrostatic pressure is preferred from the viewpoint of aligning the crystal grain size and the degree of crystal anisotropy with isotropic pressure. As a result, nano-polycrystalline diamond having a uniform crystal grain size and crystal anisotropy can be produced, and the bond between crystal grains can be further strengthened.

  Next, the nano-polycrystalline diamond synthesized in the previous step is processed into polycrystalline diamond abrasive grains. At this time, any processing can be adopted as long as the excellent characteristics of the nano-polycrystalline diamond can be maintained. For example, a metal, a ceramic, or a composite thereof may be collided with nano-polycrystalline diamond and pulverized. For example, stainless steel (SUS) can be used as the metal used for the collision. In addition, as the shape of the metal, ceramic, or composite thereof used for the collision, any shape can be adopted, for example, a spherical shape may be used. At this time, the polycrystalline diamond abrasive grains can be processed to have an average secondary particle diameter of 1 μm or more and 200 μm or less, and the collision conditions can be selected so as to have a desired average secondary particle diameter. . For example, polycrystalline diamond abrasive grains having a large average secondary particle diameter can be obtained by reducing the number of collisions.

  The polycrystalline diamond abrasive grains may contain polycrystalline diamond abrasive grains having a secondary particle diameter of less than 1 μm or 200 μm or more as long as the average secondary particle diameter is in the range of 1 μm to 200 μm. Moreover, the method for producing polycrystalline diamond abrasive grains according to the present embodiment may include a step of selecting the secondary particle diameter of nano-polycrystalline diamond used for the abrasive grains by sieving or the like. Thereby, since the secondary particle diameter of a polycrystalline diamond abrasive grain can be arrange | positioned in the desired range, the processing quality by a polycrystalline diamond abrasive grain can be improved.

  As described above, according to the method for producing polycrystalline diamond abrasive grains according to the present embodiment, the polycrystalline diamond abrasive grains are produced by processing the nanopolycrystalline tiremond as described above. Polycrystalline diamond abrasive grains having a longer life than conventional abrasive grains can be obtained.

  In addition, the average secondary particle diameter of the polycrystalline diamond abrasive grains in the present invention is based on the particle size distribution of the individual polycrystalline grains (secondary particles) constituting the polycrystalline diamond abrasive grains based on a microscope image such as TEM. , D50 particle diameter is calculated. Specifically, from an image of a TEM (for example, “H-9000” manufactured by Hitachi, Ltd.) observed at a magnification of 100 to 500,000 times, each image is analyzed using an image analysis program (for example, “ScionImage” manufactured by Scion Corporation). The particles are extracted, and the extracted particles are binarized to calculate the area (S) of each particle. The individual particle diameter (D) is calculated as the diameter (2√ (S / π)) of a circle having the same area as the area (S) of each individual particle to obtain a frequency distribution of the particle diameter. The particle size frequency distribution is processed by a data analysis program (“Origin” manufactured by OriginLab, “Mathchad” manufactured by Parametric Technology, etc.), and a particle size at 50% cumulative (D50 particle size) is calculated. The average secondary particle size is used.

  Next, examples of the present invention will be described.

  Graphite having a concentration of inevitable impurities such as hydrogen, oxygen, nitrogen, and boron of 0.01% by mass or less formed by a vapor phase synthesis method was directly changed to polycrystalline diamond under the conditions of a temperature of 2100 ° C. and a pressure of 16 GPa. The polycrystalline diamond has a crystal grain size of about 10 to 100 nm, and it was confirmed by a scanning electron microscope (SEM) that the crystal grains were directly bonded to each other.

  This nanopolycrystalline diamond had a Knoop hardness of 120 GPa. SUS spheres were made to collide with the nano-polycrystalline diamond 20 times per second for a total of 18000 times to obtain nano-polycrystalline diamond particles. The nano-polycrystalline diamond particles were screened to 1 μm or more by sieving to produce polycrystalline diamond abrasive grains having an average secondary particle diameter of 100 μm. Further, the polycrystalline diamond abrasive grains were dispersed in water to form a slurry, and a grindstone coated with the slurry was produced.

When lapping cubic nitrogen boride with the above-mentioned grindstone, it was confirmed that the lapping rate was doubled compared to the case of using conventional diamond abrasive grains and the life of the abrasive grains was extended by 3 times or more. . The lapping conditions were a load of 300 g / cm ² , a rotation speed of 60 rpm, a slurry injection time of 10 seconds, and a slurry injection interval of 50 seconds.

  Graphite having a concentration of inevitable impurities such as hydrogen, oxygen, nitrogen, and boron of 0.01% by mass or less formed by a vapor phase synthesis method was directly changed to polycrystalline diamond under the conditions of a temperature of 2200 ° C. and a pressure of 16 GPa. The polycrystalline diamond has a crystal grain size of about 10 to 100 nm, and it was confirmed by a scanning electron microscope (SEM) that the crystal grains were directly bonded to each other.

  This nanopolycrystalline diamond had a Knoop hardness of 120 GPa. SUS spheres were made to collide with the nano-polycrystalline diamond 20 times per second for a total of 18000 times to obtain nano-polycrystalline diamond particles. The nano-polycrystalline diamond particles were screened to 1 μm or more by sieving to produce polycrystalline diamond abrasive grains having an average secondary particle diameter of 100 μm. Further, the polycrystalline diamond abrasive grains were fixed to the wire to produce a fixed abrasive wire.

  When cubic nitrogen boride was cut with the above-mentioned fixed abrasive wire, the cutting speed was doubled compared to the case of using conventional diamond abrasive grains, and the life of the abrasive grains was extended by 3 times or more. It could be confirmed.

  Graphite having a concentration of inevitable impurities such as hydrogen, oxygen, nitrogen, and boron of 0.01% by mass or less formed by a vapor phase synthesis method was directly changed to polycrystalline diamond under the conditions of a temperature of 2100 ° C. and a pressure of 16 GPa. The polycrystalline diamond has a crystal grain size of about 10 to 100 nm, and it was confirmed by a scanning electron microscope (SEM) that the crystal grains were directly bonded to each other.

  This nanopolycrystalline diamond had a Knoop hardness of 120 GPa. SUS spheres were made to collide with the nano-polycrystalline diamond 20 times per second for a total of 18000 times to obtain nano-polycrystalline diamond particles. The nano-polycrystalline diamond particles were screened to 20 μm or less to produce polycrystalline diamond abrasive grains having an average secondary particle diameter of 10 μm. Further, the polycrystalline diamond abrasive grains were dispersed in water to form a slurry, and a grindstone coated with the slurry was produced.

  When the above-described grindstone was used to wrap cubic nitrogen boride under the same conditions as in Example 1, the lapping rate was doubled and the life of the abrasive grains was tripled compared to the case of using conventional diamond abrasive grains. It has been confirmed that it extends as described above.

  Graphite having a concentration of inevitable impurities such as hydrogen, oxygen, nitrogen, and boron of 0.01% by mass or less formed by a vapor phase synthesis method was directly changed to polycrystalline diamond under the conditions of a temperature of 2200 ° C. and a pressure of 16 GPa. The polycrystalline diamond has a crystal grain size of about 10 to 100 nm, and it was confirmed by a scanning electron microscope (SEM) that the crystal grains were directly bonded to each other.

  This nanopolycrystalline diamond had a Knoop hardness of 120 GPa. SUS spheres were made to collide with the nano-polycrystalline diamond 20 times per second for a total of 18000 times to obtain nano-polycrystalline diamond particles. The nano-polycrystalline diamond particles were screened to a size of 10 μm or more to produce polycrystalline diamond abrasive grains having an average secondary particle size of 100 μm. Further, the polycrystalline diamond abrasive grains were fixed to the wire to produce a fixed abrasive wire.

  When cubic nitrogen boride was cut with the above-mentioned fixed abrasive wire, the cutting speed was doubled compared to the case of using conventional diamond abrasive grains, and the life of the abrasive grains was extended by 3 times or more. It could be confirmed.

  Graphite having a concentration of inevitable impurities such as hydrogen, oxygen, nitrogen, and boron of 0.01% by mass or less formed by a vapor phase synthesis method was directly changed to polycrystalline diamond under conditions of a temperature of 2100 ° C. and a pressure of 20 GPa. The polycrystalline diamond has a crystal grain size of about 10 to 100 nm, and it was confirmed by a scanning electron microscope (SEM) that the crystal grains were directly bonded to each other.

  This nanopolycrystalline diamond had a Knoop hardness of 120 GPa. SUS spheres were made to collide with the nano-polycrystalline diamond 20 times per second for a total of 18000 times to obtain nano-polycrystalline diamond particles. Polycrystalline diamond abrasive grains having an average secondary particle diameter of 100 μm were prepared by screening the nanopolycrystalline diamond through a 100 μm sieve. Further, the polycrystalline diamond abrasive grains were dispersed in water to form a slurry, and a grindstone coated with the slurry was produced.

  When the above-described grindstone was used to wrap cubic nitrogen boride under the same conditions as in Example 1, the lapping rate was doubled and the life of the abrasive grains was tripled compared to the case of using conventional diamond abrasive grains. It has been confirmed that it extends as described above.

  Graphite having a concentration of inevitable impurities such as hydrogen, oxygen, nitrogen, and boron of 0.01% by mass or less formed by a vapor phase synthesis method was directly changed to polycrystalline diamond under the conditions of a temperature of 2200 ° C. and a pressure of 20 GPa. The polycrystalline diamond has a crystal grain size of about 10 to 100 nm, and it was confirmed by a scanning electron microscope (SEM) that the crystal grains were directly bonded to each other.

  This nanopolycrystalline diamond had a Knoop hardness of 120 GPa. SUS spheres were made to collide with the nano-polycrystalline diamond 20 times per second for a total of 18000 times to obtain nano-polycrystalline diamond particles. Polycrystalline diamond abrasive grains having an average secondary particle diameter of 100 μm were prepared by screening through a 100 μm sieve. Further, the polycrystalline diamond abrasive grains were fixed to the wire to produce a fixed abrasive wire.

  When cubic nitrogen boride was cut with the above-mentioned fixed abrasive wire, the cutting speed was doubled compared to the case of using conventional diamond abrasive grains, and the life of the abrasive grains was extended by 3 times or more. It could be confirmed.

  In addition, the conventional diamond abrasive grain made into the comparison object in said Example is a single crystal diamond abrasive grain. When the cubic boron nitride was polished under the same lapping conditions as in Example 1 as a slurry, the lapping rate was 1 μm / h. In addition, when a conventional diamond abrasive grain was fixed to form a wire saw and cubic boron nitride was cut, the cutting speed was 140 μm / min.

  In the above examples, polycrystalline diamond abrasive grains having an average secondary particle diameter of 1 to 100 μm obtained by pulverizing high-hardness nanopolycrystalline diamond having a crystal grain diameter of about 10 to 100 nm are obtained by conventional diamond grinding. It was confirmed that the lifetime was three times longer than that of the grains. However, even under conditions other than the Examples, it is considered that polycrystalline diamond abrasive grains having equivalent characteristics can be produced as long as they are within the scope of the claims.

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

Claims (7)

A polycrystalline diamond abrasive grain made of polycrystalline diamond containing no binder,
The polycrystalline diamond has a crystal grain size of less than 1 μm,
Polycrystalline diamond abrasive grains having an average secondary particle diameter of 1 μm or more and 200 μm or less.   The polycrystalline diamond abrasive according to claim 1, wherein an inevitable impurity concentration in the polycrystalline diamond is 0.01% by mass or less.   A slurry using the polycrystalline diamond abrasive grain according to claim 1.   A fixed abrasive wire to which the polycrystalline diamond abrasive grain according to claim 1 or 2 is fixed. Sintering the carbon material at a pressure of 12 GPa or higher and a temperature of 1500 ° C. or higher without using a binder to directly convert it to diamond to obtain polycrystalline diamond having a crystal grain size of less than 1 μm;
And a step of processing the polycrystalline diamond so that the average secondary particle diameter is 1 μm or more and 200 μm or less.   The method for producing polycrystalline diamond abrasive grains according to claim 5, wherein the carbon material is prepared by a vapor phase synthesis method. In the step of processing the polycrystalline diamond,
The method for producing polycrystalline diamond abrasive grains according to claim 5 or 6, wherein the polycrystalline diamond is pulverized by colliding a metal, a ceramic, or a composite thereof with the polycrystalline diamond.