JP5081352B2 - Method for producing carbide coated diamond powder - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a carbide-coated diamond powder, in particular, a diamond fine powder whose surface is coated with a carbide layer of a transition metal and has improved uniform mixing with the bond material and bonding strength with the bond material metal, and the effectiveness of such diamond powder. The present invention relates to a manufacturing method.
[0002]
[Prior art]
When manufacturing a metal bond diamond tool, the surface of the diamond particle as an abrasive grain is made of some kind such as titanium, chromium or silicon in order to firmly hold the chemically inert diamond with the bond metal. It is widely practiced to coat with metal. As a coating method, vapor deposition, other PVD techniques, CVD by decomposition of volatile compounds, and the like are used. These coating metals become carbides at the joints with diamond and form a strong chemical bond with diamond.
[0003]
Since these metals or metal carbides have much better wettability to the bond metal than diamond, the diamond abrasive grains are fixed to the bond metal via the metal carbide by chemical bonding, and the abrasive grains Long tool life has been achieved by preventing falling off.
[0004]
In addition, these coating layers also function as a protective film to prevent the diamond surface from coming into contact with oxygen, and also prevent the graphitization of diamond promoted by contact with oxygen during heating during diamond tool fabrication. It is known that
[0005]
With the development of precision machining technology, diamond tools used for cutting, grinding, and polishing have become highly functional, and the processing field in which loose abrasive grains have been used in the past has been progressively processed with fixed abrasive grains using a grindstone. It is changing. And the size of diamond used for the grindstone has become finer, and submicron-sized diamond powder can be fixed in the grindstone.
[0006]
When fixing the fine diamond abrasive grains in the bond material as described above, if the bond material is a metal system, the effect of fixing the abrasive grains by chemical bonding is expected, and at the same time, the raw material to be implemented prior to sintering In order to enable uniform mixing of the metal powder and the diamond powder, it is desirable to form a metal or metal carbide coating on the surface of the diamond particles in advance.
[0007]
That is, due to oxygen or oxygen-containing functional groups adsorbed or adhered to the surface of the diamond particles, the diamond particles agglomerate during mixing, and a gas mainly containing CO during sintering. Are released from the particle surface, and as a result, the bonding strength between the diamond particles and the bond material is lowered, that is, the holding power of the powder by the bond material is lowered.
[0008]
Therefore, it is desirable to remove the oxygen from the surface of the diamond particles by heating and to form a metal carbide film on the diamond surface by the reaction between the transition metal and diamond to inactivate the surface of the diamond particles and eliminate the above problems. A similar effect is expected when a resin-based bond material is used.
[0009]
In order to improve the bonding strength with such a bonding material and to exhibit an antioxidant effect, it is desirable that the entire surface of the diamond powder is covered with metal or metal carbide as described above. However, in order to bring the entire surface of the powder into contact with the metal source by the PVD or CVD method described above, there is a problem that complicated equipment and operation are required for mixing and stirring, and productivity is low.
[0010]
[Problems to be solved by the invention]
Accordingly, a main object of the present invention is to provide diamond abrasive grains having improved bonding strength with a metal-based bond material, and an effective manufacturing method thereof.
[0011]
[Means for Solving the Problems]
The gist of the present invention resides in that in the diamond powder having an average particle size of 40 μm or less, the surface of the diamond particles constituting the powder is entirely covered with transition metal carbide.
[0012]
The formation of the carbide coating layer according to the present invention can be applied to diamond powder having an average (nominal) particle size of 40 μm or less as described above. The most effective is in diamond powder of 20 μm or less, particularly 5 μm or less.
[0013]
The amount of the carbide coating layer varies to some extent depending on the particle size of the diamond particles of the substrate, but it is appropriate that the mass ratio with respect to diamond is approximately 0.5% or more and less than 5%. If the amount is less than this range, the above effect is not remarkable. On the other hand, if an excessive coating is applied, the amount of carbon atoms that move to form carbides on the crystal surface increases, and a large number of vacancies are formed in the diamond crystal. This is not preferable because the strength of the crystal itself is reduced.
[0014]
In the present invention, the metal species forming the carbide coating layer is suitably a transition metal, and particularly contains one or more selected from titanium, zirconium, chromium, molybdenum, tungsten, and vanadium. Thus, the carbide is formed by reacting such a metal with the base diamond under the influence of heat.
[0015]
For the preparation of the above-mentioned carbide-coated diamond powder, a method using a halide vapor of these metals can be used. In particular, this method uses a gas phase as a metal carrier, so that a carbide layer can be effectively formed even on the surface of fine diamond particles.
[0016]
According to the present invention, generation of diamond powder with carbides coating layer to such coating layer is carried out as follows.
[0017]

(1) After filling a sealed container with diamond powder (with an average particle size of 40 μm or less) and one or more transition metals selected from titanium, zirconium, chromium, molybdenum, tungsten and vanadium, and a halogen substance, 600 ° C. or higher Heated to
(2) A halide of the metal is formed by the reaction between the transition metal and the halogen to reach the surface of the diamond particles,
(3) The halide is decomposed on the diamond surface, while the transition metal released by the decomposition is reacted with diamond to form a metal carbide layer on the diamond surface.
[0018]
In the above, iodine can be used as the halogen, and the above transition metal iodide can be used as the halide. Since the metal iodide vapor can penetrate into the fine diamond particle gaps, the metal iodide vapor can be brought into contact with the entire surface of the diamond particles, so that even a fine diamond surface can be uniformly coated.
[0019 ]
Te above Symbol method odor, since the diffusion rate of carbon or metal atoms is not large in the carbide, the reaction rate of each other at the point where the carbide occurs was reduced, apparently at the particle surface which is exposed carbon atoms Carbide formation reaction proceeds with priority. As a result, according to the present invention, the entire diamond surface is covered with a carbide layer having a substantially uniform thickness.
[0020]
Further in the method of the present invention by a halide vapor treatment, metal fluoride anhydride, chloride may also be used, but diamond reacts with metal iodide to form a metal carbide, based on the nature of the separation of iodine, iodine The iodide method using bismuth as a metal carrier is advantageous because it is easy to operate. In this case, the conditions for forming carbides over the entire particle surface are established by filling the gaps between the diamond particles with iodide vapor. Since iodine separated from the metal on the diamond surface comes into contact with the metal and becomes metal iodide again, iodine acts as a metal carrier until the diamond particle surface is covered with metal carbide and the metal transport rate is reduced.
[0021]
Also in the iodide method, the treatment temperature is preferably 600 ° C. or higher, particularly 800 ° C. or higher (temperature on the diamond surface) from the viewpoint of securing the carbide formation rate.
[0022]
Thus, in the present invention, all the diamond powder surface, a transition metal from touching including vapor phase, that all the powder surface is covered with a carbide formed by reaction of the metal deposited from vapor phase Thus, the adhesion to the matrix metal during tool manufacture is improved, and the effect of preventing oxidation and graphitization of diamond during heating is obtained as a protective film. In particular, by improving the adhesion to metal, for example, in a grinding wheel, diamond is firmly held by the bond material metal. There is also a merit that resistance is lowered.
[0023]
Also, in fine powder (submicron grade) diamond, the functional groups on the diamond surface, which cause the aggregation of diamond particles, are replaced with metal carbide, resulting in the surface becoming inactive and the dispersibility of the powder. As a result, the mixing operation with the powdery matrix raw material became easy. Such a change in the diamond surface state was also confirmed by infrared absorption analysis.
[0024]
When the diamond powder of the present invention is applied to a ceramic matrix material in the manufacture of a tool, the diamond powder covered with carbide is heated to 1000 ° C. or higher in a nitrogen atmosphere, so that the surface is carbonitride or nitride. It is possible to improve the wettability and adhesive strength to the matrix material.
[0025]
The following method is effective for the nitriding treatment. That is, carbide-coated diamond is placed in a sealed container and heated to a predetermined temperature in a nitrogen atmosphere. The operation of evacuating the inside of the container while maintaining heating and filling with nitrogen is repeated. By this method, the surface of submicron diamond powder can be nitrided.
[0026]
[Example 1 ]
Internal volume 50 ml made of SUS into a closed vessel, diamond powder 10g having an average particle size of 20 [mu] m, molybdenum powder 2g having an average particle diameter of 3 [mu] m, put iodine 1g, sealed and evacuated vessel, heated to 950 ° C. Held for 1 hour. The extracted diamond had a black color, and the generation of Mo ₂ C was confirmed by X-ray diffraction.
[0027]
Using the obtained molybdenum-coated diamond, a bronze bonded surface grinding wheel was manufactured and used for grinding a sintered alumina plate. The grindstone was a straight grindstone with an outer diameter of 150 mm and a thickness of 8 mm. The concentration was 50, and the grinding conditions were a peripheral speed of 1500 m / min and a cutting depth of 3 μm. The grinding resistance was reduced by 15% and the grinding wheel life was increased by 43% compared to a grinding wheel using uncoated diamond manufactured simultaneously for comparison.
[0028]
[Example 2 ]
The above method is carried out using tungsten powder having an average particle diameter of 3 μm instead of molybdenum powder, and a WC coating layer is formed on the diamond surface, and the thickness of the coating layer is about 0.05 μm by SEM observation. Admitted. For quantification of the coating amount, a method of obtaining the value of about 3% was obtained by using a method in which the coating was dissolved and removed using hydrofluoric acid and the mass was determined before and after dissolution.
[0029]
【Effect of the invention】
1. As is well known, during the manufacture of a metal bond tool, the diamond abrasive grains and the metal of the bond material form a chemical bond through the carbide coating formed on the diamond surface. In the diamond powder, the holding strength of the abrasive grains by the bond material is improved, the fall of the abrasive grains is prevented, and the tool life is improved by effective use. At the same time, since the protruding height of the abrasive grains on the tool surface can be made large, the energy required for processing can be reduced.
[0030]
2. Even in the fine diamond powder, by applying the coating of the present invention, the functional group on the particle surface that causes the powder aggregation is substituted with the carbide and inactivated. As a result, in the production of diamond fine powder-containing tools or wear-resistant hard materials, the dispersibility of diamond is improved during the mixing operation with the matrix raw material, the uniformity of the structure in the material using fine diamond is increased, and the resistance is increased. Abrasion performance is improved.

Claims (3)

(1) Fill a sealed container with diamond powder and one or more transition metals selected from titanium, zirconium, chromium, molybdenum, tungsten, vanadium, and a halogen substance, and then heat to 600 ° C or higher.
(2) A halide of the metal is formed by the reaction between the transition metal and the halogen to reach the surface of the diamond particles,
(3) Carbide-coated diamond powder characterized in that a metal carbide layer is formed on the diamond surface by decomposing the halide on the diamond surface and reacting the transition metal liberated by the decomposition with diamond. Manufacturing method. The method for producing a carbide-coated diamond powder according to claim 1 , wherein the halogen is iodine. The method for producing a carbide-coated diamond powder according to claim 1 , wherein the diamond powder has an average particle size of 40 μm or less.