JP6968346B2 - Diamond grains for tools and their manufacturing methods - Google Patents

Description

The present invention relates to diamond grains suitable for tools used for removal processing such as cutting processing and polishing processing, and a method for producing the same.

Diamond is known as the hardest material on the earth and is industrially used for removing various hard and brittle materials. However, although diamond is a hard material, it has a drawback that it has a lower toughness than a metal material, and has a problem in terms of fracture resistance when used for removal processing. For example, regarding the machining of diamond tools using diamond abrasive grains, it is always an issue to improve the machining quality and reduce the machining cost, and for this reason, a tool capable of high-speed machining and having a long life is required. It is also required to reduce the manufacturing cost of the diamond tool itself.

The wear of the diamond tool progresses due to the dropout of the abrasive grains, the chipping of the abrasive grains, and the chemical wear of the abrasive grains. By improving the properties that lead to these wear factors, the life and machining quality of the tool will be improved. The dropout of the abrasive grains can be improved by increasing the adhesion between the diamond and the metal layer to which it is fixed, and by increasing the durability of the metal layer itself to which the diamond is fixed. Further, the chemical wear of the abrasive grains is improved by increasing the cooling capacity of the processed portion.

However, although the defect of the abrasive grains can be reduced by using the diamond grains having high strength, there is a problem that the workability is deteriorated. Further, although it can be reduced to some extent by slowing down the processing speed, there is a problem that the processing cost becomes high. As described above, the current situation is that there is no effective countermeasure for the defect of the diamond tool even if an attempt is made to improve it.

On the other hand, as one of the means for improving the fracture resistance of the material, a method of applying compressive stress to the surface of the material has been conventionally adopted. There are various methods for applying compressive stress, and shot blasting is a typical example. Further, in the field of hard thin films, it has been confirmed that a thin film formed by a physical vapor deposition method in particular has an effect that compressive stress is generated and it is difficult to be chipped, and fatigue strength is increased. It is also well known that when materials with different coefficients of thermal expansion are bonded at a high temperature and cooled to room temperature, tensile stress is generated on the material side with a large coefficient of thermal expansion and compressive stress is generated on the material side with a small coefficient of thermal expansion. It is a phenomenon.

Although it is not intended to apply compressive stress to diamond grains, many techniques for coating the surface of diamond grains with a material having a coefficient of thermal expansion larger than that of diamond have been proposed so far. For example, it is carried out for the purpose of improving the bondability between the diamond grain and the binder or the plating film for fixing the diamond grain, reducing the dropout of the abrasive grain, and improving the life of the tool. Even with these methods, compressive stress is generated in the diamond grains as a result, but it cannot be said that the effect is fully exhibited.

Patent Document 1 describes (1) diamond powder and titanium, zirconium, chromium, molybdenum, as well as diamond powder in a closed container for the purpose of obtaining diamond abrasive grains having an improved bonding force with a metal-based bond material for a metal-bonded diamond tool. After filling with one or more transition metals selected from tungsten and vanadium, and halogen substances, the mixture is heated to 600 ° C. or higher, and (2) a halide of the metal is formed by the reaction between the transition metal and halogen to form the above diamond. A method has been proposed for producing a carbide-coated diamond powder by reaching the surface of the particles and (3) decomposing the halide on the surface of the diamond, while reacting the transition metal released by the decomposition with the diamond. There is.

Further, Patent Document 2 describes superabrasive tools such as diamond and cubic boron nitride for the purpose of preventing deterioration of superabrasive grains due to the influence of heat during sintering for forming a superabrasive grain layer. The surface of the abrasive grains is coated with metal carbide. In this method for producing metal carbide-coated superabrasive grains, the temperature in the reaction chamber is raised to a predetermined temperature, and the atmosphere in the reaction chamber is depressurized. The first step of holding the superabrasive particles, the second step of introducing a raw material gas containing at least a metal into the reaction chamber holding the superabrasive particles, and the raw material gas in the reaction chamber for a predetermined time. The second, third, and fourth steps are provided with a third step of holding the raw material gas, and after the step of holding the raw material gas, a fourth step of exhausting the reaction chamber to bring the pressure down. A method for producing metal carbide-coated superabrasive grains by repeating the process has been proposed.

Further, in Patent Document 3, for the purpose of firmly fixing the metal layer to the diamond substrate, a mixture or alloy of a metal capable of forming a stable carbide and a low melting point metal is used as a diamond abrasive grain or an abrasive grain. A method has been proposed in which a metal-coated diamond abrasive grain is produced by arranging it in contact with an aggregate, forming a layer of a molten alloy generated by heating on the surface of diamond, and simultaneously or by raising the temperature further.

Further, in Patent Document 4, for the purpose of forming a bonding layer on the surface of the diamond for firmly bonding the diamond to a dissimilar material such as metal, the surface of the diamond is arranged so as to be in contact with the metal powder contained in the container. Then, the inside of the container containing the diamond and the metal powder is evacuated, and the surface of the diamond is heated at a temperature higher than the temperature at which the metal powder can form a metal carbide layer on the surface of the diamond and below the melting point of the metal powder. A method of forming a metal carbide layer has been proposed.

Japanese Patent Application Laid-Open No. 2003-55649 Japanese Unexamined Patent Publication No. 2001-322066 Japanese Unexamined Patent Publication No. 2-229878 Japanese Unexamined Patent Publication No. 2001-220251

As described above, regarding machining using a diamond tool, it is required to improve the machining quality and reduce the machining cost and the tool manufacturing cost. By improving the wear factor of the diamond tool in response to such a demand, the life of the tool can be extended and the processing quality can be improved. In Patent Documents 1 to 4 described above, since the surface of the diamond grain is coated with a material having a coefficient of thermal expansion larger than that of diamond, compressive stress is applied to the diamond grain, and the defectability of the diamond abrasive grain among the wear factors is improved. May be done.

However, Patent Document 1 is a method of chemically transferring a metal to diamond using a halogen such as iodine, so that a device for treating a toxic halogen gas, which is highly corrosive to the metal, is required. There is a problem that the manufacturing cost becomes high. Further, in this method, since the thickness of the carbide layer depends on the diffusion rate of carbon, it takes time to thicken the carbide layer, which poses a problem in terms of manufacturing cost.

Since Patent Document 2 is also a method using a halogen compound gas containing titanium tetrachloride or the like, equipment such as an apparatus is costly as in Patent Document 1.

Since Patent Document 3 is a method of heating a metal to a temperature equal to or higher than the melting point, it is extremely difficult to separate the diamond grain and the metal after melting, which poses a problem in terms of practical use and manufacturing cost.

Since Patent Document 4 is a method of forming a metal carbide layer for the purpose of improving the bondability between diamond and metal, it cannot be said that the compressive stress applied to diamond is sufficient, and there is a problem in terms of the improvement effect.

As shown above, all of the above patent documents have technical problems and cost problems, and cannot be said to be sufficient in terms of processing quality.

In view of the above, the present invention has been made to provide diamond grains for tools which have fracture resistance and can be manufactured at low cost, and a method for manufacturing the same.

The diamond grain for a tool according to the present invention is a diamond grain for a tool having a diamond grain having an average particle size of 1 μm to 1000 μm and a coating film made of titanium nitride formed on the surface of the diamond grain. In the coating film, the peak position of the diffraction line by X-ray diffraction using the copper target exists between the peak position at the Miller index (220) of titanium carbide and the peak position at the Miller index (220) of titanium nitride. ing.

In the method for producing diamond grains for tools according to the present invention, the diamond grains having an average particle size of 1 μm to 1000 μm are surrounded by titanium grains having an average particle size of 1 μm to 4000 μm in a container capable of vacuum exhaust and heating. A transfer step of arranging a mixed mixture that has been brought into contact with each other and heating the mixture at a temperature lower than the melting point of the titanium grains while keeping the inside of the container in a vacuum to transfer titanium to the surface of the diamond grains. It is provided with a nitriding step of forming a film made of titanium carbonitride on the surface of the diamond grains by introducing nitrogen into the container and creating a nitrogen atmosphere while continuing the heated state of the transfer step.

In another method for producing diamond grains for tools according to the present invention, a diamond grain having an average particle size of 1 μm to 1000 μm is surrounded by titanium grains having an average particle size of 1 μm to 4000 μm in a container capable of vacuum exhaust and heating. A transfer step of arranging the mixed mixture in contact with each other and heating the mixture at a temperature lower than the melting point of the titanium grains while keeping the inside of the container in a vacuum to transfer titanium to the surface of the diamond grains. Then, by taking out only the transferred diamond grains treated in the transfer step, arranging the transferred diamond grains in a container capable of heating the atmosphere and heating in a nitrogen atmosphere, titanium carbonitride on the surface of the diamond grains. It includes a nitriding step of forming a film made of a material.

Further, in the above manufacturing method, the heating temperature is set to 700 ° C. or higher and 1000 ° C. or lower in the transfer step and the nitriding step.

In the present invention, it is possible to obtain high-quality tool diamond grains having a film made of titanium carbonitride formed on the surface of the diamond grains and having hardened fracture resistance, and transfer of titanium to the surface of the diamond grains. The process and the nitrided titanium nitriding process make it possible to easily produce high quality tool diamond grains at low cost.

It is a schematic block diagram of the manufacturing apparatus for carrying out this invention. It is a schematic cross-sectional view of the diamond grain for a tool. It is a schematic cross-sectional view of the transferred diamond grain. It is a graph which shows the X-ray diffraction result of the treated plate-shaped diamond in Example 2. FIG. It is a graph which shows the X-ray diffraction result of the transferred plate-shaped diamond in Example 3. FIG. It is a graph which shows the X-ray diffraction result of the treated plate-shaped diamond in Example 3. FIG.

Hereinafter, embodiments according to the present invention will be described in detail. In the diamond grain for a tool according to the present invention, the surface of the diamond grain is coated with a coating film made of a plurality of types of materials, and the compressive stress generated between the plurality of types of materials is utilized to improve the fracture resistance of the diamond grain. It is something that is going to be enhanced.

As the diamond grains used in the present invention, those having an average particle size of 1 μm to 1000 μm are preferable for tools. As such diamond grains, those usually available can be used. The shape of the diamond grain can be various and is not particularly limited depending on the intended use.

As the material used for the coating film formed on the surface of the diamond grain, a material having adhesion and strength capable of withstanding the high stress generated at the interface between the diamond and the coating material due to the difference in thermal expansion or the like is preferable. High adhesion is obtained by forming a chemical reaction layer between the diamond and the coating material. Such materials preferably form a carbide-based material having a high hardness, and examples thereof include materials such as titanium, zirconium, hafnium, tungsten, molybdenum, and tantalum, and alloy materials containing these. Among these, titanium is preferable because it has a lower melting point than other metals and has high adhesion to diamond. As the titanium, various forms such as sponge titanium and granular titanium can be used. When titanium particles are used, it is preferable to use titanium particles having an average particle size of 1 μm to 4000 μm.

When titanium metal is transferred to the surface of diamond grains, titanium carbide is formed near the interface between the titanium metal and diamond, but in general, titanium nitride has a higher hardness, that is, strength than titanium carbide. In addition, since it has a high coefficient of thermal expansion, it is preferable as a coating material, and it is considered that stronger compressive stress is generated. Specifically, titanium carbide has a coefficient of thermal expansion of 7.8 × 10 ^-6 / ° C at a hardness of 16 GPa, and titanium carbide has a coefficient of thermal expansion of 8.1 × 10 ^-6 / ° C at a hardness of 18 GPa. ..

The film made of titanium carbide formed on the surface of diamond grains can be formed by heat-treating the film made of titanium carbide formed on the surface of diamond grains in a nitrogen atmosphere.

The melting point of titanium metal differs slightly depending on the manufacturing method and the content and form of impurities, but even at a temperature 500 ° C or more lower than the melting point of titanium metal, the titanium metal can be generated through the contact portion between the titanium metal and diamond by chemical driving force. A film is formed so as to diffuse to the surface of the diamond and cover the surface, and the surface of the diamond can be treated. Specifically, if heat treatment is performed at a heating temperature of 700 ° C. to 1000 ° C., a film made of titanium carbide can be formed using a wide variety of titanium such as sponge titanium and granular titanium.

After the titanium metal is transferred to the surface of the diamond to form a film made of titanium carbide, the transferred titanium is nitrided to the surface of the diamond grains by supplying nitrogen gas into the container to create a nitrogen atmosphere. A diamond grain for a tool having a film formed of titanium carbonitride can be obtained. The heating temperature does not have to be the same as the heating temperature at the time of titanium transfer, but the selected temperature range is preferably set to 700 ° C. to 1000 ° C. as at the time of transfer.

When particulate titanium is used, by setting the heating temperature appropriately according to the type of titanium, the titanium grains or the titanium grains and the diamond grains do not adhere firmly to each other, and after the coating treatment. The diamond particles for tools and the titanium particles can be easily separated.

The produced titanium carbonitride can be confirmed by X-ray diffraction, and the distribution of the diffraction lines appears continuously as an intermediate phase between the diffraction peaks of titanium carbide and titanium nitride. Specifically, in an X-ray diffraction experiment using a copper target, if the diffraction angle of titanium carbide is 2θ = 60.448 ° and the diffraction angle of titanium nitride is 2θ = 61.812 °, the distribution of the diffraction lines will be the same. The formation of titanium carbide can be confirmed in the range between the diffraction points. Specifically, it is possible to confirm the formation of titanium carbonitride when the peak position exists between the peak positions where the intensity becomes the maximum value in the distribution of the diffraction lines of titanium carbide and titanium nitride. In order to confirm the presence of titanium carbonitride based on the peak position of the diffraction line, the Miller index of the diffraction line is set to (hkl) = (220) to ensure that it is separated from other peak positions such as carbon. The peak position can be confirmed. Therefore, the peak position of the diffraction line exists between the peak position at the Miller index (220) of titanium carbide and the peak position at the Miller index (220) of titanium nitride, thereby preventing the presence of titanium carbonitride. It becomes possible to identify.

Next, a method for manufacturing diamond grains for tools according to the present invention will be described. FIG. 1 is a schematic configuration diagram of a manufacturing apparatus for carrying out the present invention. A vacuum exhaust device 5 is connected to a chamber 3 such as a quartz tube via an exhaust valve 8, and a nitrogen cylinder 9 is connected to the chamber 3 via a nitrogen supply valve 7. A pressure relief valve 10 is attached to the connection pipe between the vacuum exhaust device 5 and the vacuum exhaust device 5. A heating device 6 is attached around the chamber 3 so that the entire chamber 3 is heat-treated so as to have a predetermined heating temperature. The mixture 12 of the diamond grains 1 and the titanium grains 2 is housed in the crucible 4 made of alumina and arranged in the chamber 3.

In the mixture 12, the diamond grains 1 and the titanium grains 2 are uniformly mixed, and the diamond grains 1 are brought into contact with each other so as to be surrounded by the titanium grains 2. As the diamond grain 1, one formed into a pentagonal cross section is used, but diamond grains having another shape such as a plate can also be treated in the same manner. It is also possible to process diamond grains of different shapes at the same time. The melting point of the titanium grain 2 may change when it contains impurities, but it does not affect the treatment and a wide variety of titanium can be used. The crucible 4 on which the mixture 12 is arranged may be made of a material other than alumina as long as it has heat resistance equal to or higher than the heating temperature and has a characteristic that diffusion due to heating does not easily occur in the mixture 12. The chamber 3 can also be made of another material such as alumina as long as it can be evacuated and has heat resistance equal to or higher than the heating temperature, and is not particularly limited.

After arranging the mixture 12 in the chamber 3, the exhaust valve 8 is opened and the vacuum exhaust device 5 is operated to exhaust the inside of the chamber 3. The pressure region is preferably as high a vacuum as possible, but practically it may be about 0.01 Pa or less. The nitrogen supply valve 7 is set to the closed state during the exhaust operation.

After the inside of the chamber 3 is exhausted to a predetermined pressure, the chamber 3 is heated by the heating device 6 to heat the mixture 12 at a predetermined heating temperature, and a step of transferring titanium to the diamond grain surface is performed. The heating temperature is preferably 700 ° C. or higher, which is the temperature at which titanium is transferred to the surface of diamond grains. On the other hand, when the titanium particles 2 are melted by heating, they adhere to each other and the diamond particles 1 cannot be separated from the mixture 12. Therefore, it is desirable to set the heating temperature lower than the melting point of titanium, specifically, the heating temperature. It is preferable to set it to 1000 ° C. or lower. At a heating temperature of 1000 ° C. or lower, various types of titanium can be treated so as not to be melted, although it depends on the form of titanium. The heating temperature and heating time can be set according to the thickness and properties of the titanium carbide film to be produced.

Next, while continuously heating by the heating device 6, the nitrogen supply valve 7 is opened to supply nitrogen into the chamber 3 from the nitrogen cylinder 9, and at the same time, the exhaust valve 8 is closed to set the inside of the chamber 3 to a nitrogen atmosphere. , The mixture 12 is heated in a nitrogen atmosphere. It is advisable to continue supplying nitrogen even after the chamber 3 is filled with nitrogen. The heating temperature does not need to be set to the same temperature as the heat treatment in vacuum, but is preferably set to 700 ° C to 1000 ° C in consideration of the transfer and melting of titanium. The heating temperature and heating time can be set according to the thickness and properties of the titanium carbonitride film to be produced.

After that, the heating operation by the heating device 6 is stopped to cool the mixture 12. After cooling, the nitrogen supply valve 7 is closed, the mixture 12 is taken out from the chamber 3, and the titanium particles 2 are separated from the mixture 12 to obtain diamond particles for a tool. FIG. 2 is a schematic cross-sectional view of a diamond grain for a tool. The tool diamond grain 14 has a coating film 13 made of titanium carbonitride formed on the surface of the diamond grain 1. In the titanium transfer treatment, the chemical driving force of surface diffusion in vacuum is used, and the heating temperature is not raised to the melting point of titanium. Therefore, when separating the diamond grains for tools from the treated mixture 12. Can be easily done with a sieve or the like.

Next, a modified example of the above-mentioned manufacturing method will be described. Using the manufacturing apparatus shown in FIG. 1, the mixture 12 is placed in the chamber 3 and heated in a vacuum in the same manner as in the above procedure, and then the heating operation of the heating apparatus 6 is temporarily stopped to heat the mixture 12. Cooling. After cooling, the nitrogen supply valve 7 is opened, nitrogen is introduced from the nitrogen cylinder 9, the gas in the chamber 3 is replaced, and the mixture 12 is taken out. In the replacement of the gas in the chamber 3 after cooling, a gas introduction port may be separately connected to the manufacturing apparatus shown in FIG. 1 and the atmosphere, an inert gas or the like may be introduced to replace the gas.

The removed mixture 12 is separated from the titanium grains 2 using a sieve or the like, and the diamond grains 1 are taken out. A titanium transfer layer is formed around the diamond grain 1, and a film having a surface made of titanium carbide is formed. FIG. 3 is a schematic cross-sectional view of the treated diamond grain. A transferred diamond grain 16 having a titanium transfer layer 15 formed around the diamond grain 1 is obtained.

The obtained transferred diamond grains 16 are housed in the crucible 4 again, arranged in the chamber 3, and then the exhaust valve 8 is opened to operate the vacuum exhaust device 5 to exhaust the inside of the chamber 3. After exhausting to a predetermined pressure, the nitrogen supply valve 7 is opened to introduce nitrogen into the chamber 3 from the nitrogen cylinder 9, and at the same time, the exhaust valve 8 is closed to create a nitrogen atmosphere in the chamber 3. If it is possible to create a nitrogen atmosphere in the chamber 3 by introducing nitrogen for a long time, it is not necessary to perform exhaust before introducing nitrogen. The transferred diamond grains 16 are heated by the heating device 6 while the introduction of nitrogen is continued even after the inside of the chamber 3 is made into a nitrogen atmosphere. The heating temperature does not need to be set to the same temperature as the heat treatment in vacuum, but is preferably set to 700 ° C to 1000 ° C in consideration of the transfer and melting of titanium. The heating temperature and heating time can be set according to the thickness and properties of the titanium carbonitride film to be produced.

After that, the heating operation by the heating device 6 is stopped to cool the treated diamond grains for tools. After cooling, the nitrogen supply valve 7 is closed and the diamond grains for tools are taken out from the chamber 3 to obtain diamond grains for tools similar to those shown in FIG.

Hereinafter, examples will be described.

[Example 1]
Diamond grains for tools were manufactured using the manufacturing apparatus shown in FIG. First, a commercially available alumina crucible is placed in a chamber (manufactured by Fujiwara Seisakusho Co., Ltd.), and titanium grains (manufactured by High Purity Science Laboratory Co., Ltd .; average particle size 600 μm to 2000 μm) and diamond grains (manufactured by Tomei Diamond Co., Ltd .; average). A mixture in which particles having a particle size of 500 μm) were uniformly mixed at a weight ratio of 6: 1 was put into an alumina crucible. After setting the mixture, open the exhaust valve and operate the vacuum exhaust device (manufactured by ULVAC Kiko Co., Ltd.) to exhaust the inside of the chamber until the pressure becomes 0.002 Pa or less, and the heating device (manufactured by Asahi Rika Seisakusho Co., Ltd.). The mixture was heated to temperatures of 500 ° C., 550 ° C., 600 ° C., 650 ° C., 700 ° C., 750 ° C., 800 ° C., 850 ° C., 900 ° C., 950 ° C. and 1000 ° C. and held as it was for 60 minutes.

After that, while continuing heating at each heating temperature, the nitrogen supply valve was opened to introduce nitrogen into the chamber from a nitrogen cylinder (manufactured by Uno Oxygen Co., Ltd.), and at the same time, the exhaust valve was closed to create a nitrogen atmosphere in the chamber. After that, while continuing the introduction of nitrogen, the nitriding treatment was carried out by holding the nitrogen at each heating temperature for 60 minutes.

After that, the heating operation of the heating device was stopped to cool the furnace, the temperature inside the chamber dropped to 100 ° C or less, the introduction of nitrogen was stopped, the alumina crucible was taken out from the chamber, and titanium grains and diamond grains were screened. Treated diamond grains were obtained. All of the treated diamond grains treated at 700 ° C. or higher had a mixed color of gold and gray on the surface, whereas the treated diamond grains treated at 650 ° C. or lower did not change in color.

[Example 2]
Next, instead of the diamond grains of Example 1, a plate-shaped diamond coated with a diamond film having a thickness of about 15 μm on a cemented carbide substrate (manufactured by Mitsubishi Materials Corporation) was used and treated by the same manufacturing apparatus as in Example 1. bottom.

An alumina crucible was placed in the chamber, and a mixture of plate-shaped diamonds embedded in titanium grains was housed in the alumina crucible. After the arrangement, the exhaust valve was opened to operate the vacuum exhaust device to exhaust the inside of the chamber to a pressure of 0.002 Pa or less, and the inside of the chamber was heated to 850 ° C. by a heating device and held as it was for 60 minutes.

After that, while continuing heating, the nitrogen supply valve was opened to introduce nitrogen into the chamber from the nitrogen cylinder, and at the same time, the exhaust valve was closed to create a nitrogen atmosphere in the chamber. After that, while continuing to introduce nitrogen, the nitriding treatment was carried out by maintaining the heating temperature at 850 ° C. for 60 minutes, 120 minutes and 240 minutes.

After that, the heating operation of the heating device was stopped to cool the furnace, the temperature inside the chamber dropped to 100 ° C or less, the introduction of nitrogen was stopped, the alumina crucible was taken out from the chamber, and the plate-shaped diamond treated from the titanium grains was treated. Got The treated plate-shaped diamond exhibited a mixed color of gold and gray on the surface during each treatment time of the nitriding treatment, and was similar to the diamond grains treated at 700 ° C. or higher in Example 1.

The X-ray diffraction data of the treated plate-shaped diamond was measured using an X-ray diffractometer (manufactured by Rigaku Co., Ltd.). In the measurement, a copper target was used and the Miller index was set to (220). FIG. 4 is a graph showing the analysis results of the X-ray diffraction data of the treated plate-shaped diamond. In the graph, the intensity is taken on the vertical axis and the diffraction angle 2θ is taken on the horizontal axis, and among the measured X-ray diffraction data, the data in which the diffraction angle 2θ where the (220) peak of titanium carbide and titanium nitride appears is around 61 °. Shows. On the surface of the plate-shaped diamond, a peak position exists between titanium carbide having a diffraction peak at 60.448 ° and titanium nitride having a diffraction peak at 61.812 °, and titanium carbonitride is generated. It was confirmed that

[Example 3]
Next, the plate-shaped diamond used in Example 2 was heat-treated in a vacuum in the same manner as in Example 2. After that, the heating operation of the heating device is stopped, the chamber is cooled, the temperature inside the chamber is lowered to 100 ° C. or less, and then the nitrogen supply valve is opened to introduce nitrogen from the nitrogen cylinder to replace the gas in the chamber and replace the alumina crucible. Was taken out, and the plate-shaped diamond was taken out from between the titanium grains.

The plate-shaped diamond taken out had a gray color similar to the color of titanium grains, and it was confirmed that titanium had been transferred to the diamond surface.

The transferred plate-shaped diamond was subjected to X-ray diffraction in the same manner as in Example 2. FIG. 5 is a graph showing the analysis results of the X-ray diffraction data of the transferred plate-shaped diamond. On the diamond surface, a peak appeared at the same diffraction angle as titanium carbide having a diffraction peak at 60.448 °, and it was confirmed that titanium carbide was formed.

Then, the relocated plate-shaped diamond was housed in an alumina crucible placed in the chamber. Then, the exhaust valve is opened to operate the vacuum exhaust device to exhaust the inside of the chamber, and when the pressure drops to 0.002 Pa or less, the nitrogen supply valve is opened to introduce nitrogen into the chamber from the nitrogen cylinder and at the same time close the exhaust valve. , The inside of the chamber was made into a nitrogen atmosphere. While the introduction of nitrogen was continued, the inside of the chamber was heated to 850 ° C., 950 ° C. and 1000 ° C. with a heating device, and kept as it was for 240 minutes.

Then, the heating operation of the heating device was stopped, the temperature was cooled to 100 ° C. or lower, the introduction of nitrogen was stopped, and the treated plate-shaped diamond was taken out from the alumina crucible.

The treated plate-shaped diamond was subjected to X-ray diffraction in the same manner as in Example 2. FIG. 6 is a graph showing the analysis result of the X-ray diffraction data of the treated plate-shaped diamond. From the graph, as in Example 2, a peak position exists on the diamond surface between titanium carbide having a diffraction peak at 60.448 ° and titanium nitride having a diffraction peak at 61.812 °. , It was confirmed that titanium carbide nitride was formed.

1 ... Diamond grain, 2 ... Titanium grain, 3 ... Chamber, 4 ... Alumina pot, 5 ... Vacuum exhaust device, 6 ... Heating device, 7 ... Nitrogen supply valve, 8 ... Exhaust valve, 9 ... Nitrogen cylinder, 10 ... Pressure relief valve, 12 ... Mixage of diamond grains and titanium grains, 13 ... Coating made of titanium carbonitride, 14 ...・ Diamond grains for tools, 15 ... Titanium transfer layer, 16 ... Transfer diamond grains

Claims (3)

A mixed mixture is placed in a container capable of vacuum exhaust and heating so that diamond grains having an average particle size of 1 μm to 1000 μm are surrounded by titanium grains having an average particle size of 1 μm to 4000 μm. The container is maintained in a transfer step of heating the mixture at a temperature lower than the melting point of the titanium grains to transfer titanium to the surface of the diamond grains while keeping the inside vacuum, and a heating state of the transfer step. A method for producing diamond grains for a tool, which comprises a nitriding step of forming a film made of titanium carbonitride on the surface of the diamond grains by introducing nitrogen into the diamond grains to create a nitrogen atmosphere. A mixed mixture is placed in a container capable of vacuum exhaust and heating so that diamond grains having an average particle size of 1 μm to 1000 μm are surrounded by titanium grains having an average particle size of 1 μm to 4000 μm. While keeping the inside vacuum, the mixture is heated at a temperature lower than the melting point of the titanium grains to transfer titanium to the surface of the diamond grains, and only the transferred diamond grains treated in the transfer step are taken out. Diamonds for tools provided with a nitriding step of arranging the transferred diamond grains in a container capable of heating the atmosphere and heating in a nitrogen atmosphere to form a film made of titanium carbonitride on the surface of the diamond grains. Grain manufacturing method. The method for producing diamond grains for a tool according to claim 1 or 2, wherein in the transfer step and the nitriding step, the heating temperature is set to 700 ° C. or higher and 1000 ° C. or lower.

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