JPH0253396B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing polycrystalline diamond abrasive grains having excellent grinding properties.

[Prior Art] Natural or artificially synthesized diamonds are used as diamond abrasive grains. Normally, each of these diamonds is composed of single crystal grains.

[Problems to be solved by the invention] Diamond single crystal particles have sharp edges and are suitable as abrasive grains, but they also have the disadvantage of being weak against stress and impact and easily broken. There is. In this sense, diamond polycrystalline particles have high fracture strength. Therefore, polycrystalline diamond particles are particularly suitable for heavy grinding such as creep feed grinding. However, polycrystalline diamond particles are rarely produced naturally.

One possibility of synthesizing polycrystalline diamond particles using conventional techniques is to sinter polycrystalline particles and then crush them.
However, each step of sintering under ultra-high pressure, pulverization, and classification requires high costs. Therefore, it seems difficult to industrially realize the production of polycrystalline diamond particles.

A method for producing diamond powder without using an ultra-high pressure apparatus is disclosed in Japanese Patent Application Laid-Open No. 107914/1983. According to this document, a method is disclosed in which diamond powder is extracted by heating an amorphous metal to precipitate diamond and then dissolving phases other than diamond. However, this method only discloses a method for obtaining diamond powder, but does not disclose a method for obtaining polycrystalline diamond particles that can be used as abrasive grains for grinding.

Also, "Surface Science" Volume 5 No. 1 (1984) No. 54
Pages to pages 60, CVD and plasma on the substrate
A method for synthesizing diamond from the gas phase by CVD is disclosed. According to this document, the relationship between the surface treatment of the substrate and the density of diamond nucleation is described as follows.

When a silicon wafer is cleaned with an acid or an organic solvent, the density of nucleation is low, and most of the diamond particles grow as independent particles (single crystals).
Diamond particles are said to be concentrated in the scratches and edges. That is, when a silicon wafer as a substrate is chemically cleaned, diamond particles are precipitated as independent particles in most cases.

Furthermore, it is said that one effective method for obtaining diamond film is to roughen the surface of a silicon wafer with an abrasive. In other words, if the surface of the substrate is uniformly roughened with a mechanical abrasive, a diamond film will grow. This is thought to be due to the fact that when the surface of the substrate is roughened with an abrasive, the density of nucleation on the surface increases, and the growing diamond particles become stuck together, forming a diamond film. .

As mentioned above, polycrystalline diamond particles that can be used as abrasive grains cannot be obtained even when the substrate is chemically cleaned or roughened with a mechanical abrasive.

This invention has been made to solve the above-mentioned problems, and aims to provide an industrially feasible method of manufacturing diamond polycrystalline particles that can be used as abrasive grains. .

[Means for Solving the Problems] To realize this invention, it is necessary to precipitate diamond particles from the gas phase. Research on diamond vapor phase synthesis has been conducted for a long time. As shown in the above-mentioned literature, a method of synthesizing diamond by CVD or plasma CVD has recently been established. However, it is only recognized that diamond in the form of film or single crystal particles can be obtained by this method.

While considering these methods, the inventors of the present application discovered that it was possible to obtain polycrystalline diamond particles, and came up with the idea of applying the polycrystalline particles as abrasive grains. be.

The method for producing polycrystalline diamond abrasive grain according to the present invention is to grow polycrystalline diamond grains as a group of densely packed grains having a predetermined grain size, with polycrystalline grains spaced apart from each other. A method for obtaining particles, which includes the following steps.

(1) The surface of the base material, which will become the bed for diamond synthesized from the gas phase, is machined to a predetermined surface roughness according to the above-mentioned spacing and particle size so that diamond precipitation starts at multiple points. The process of forming

(2) A step of synthesizing diamond particles from the gas phase onto the surface of the base material.

(3) A step of separating the diamond particles from the base material.

Step (1) is to control the number of diamond nuclei generated during vapor phase synthesis. If too many nuclei are generated, it will easily become a film-like diamond. Therefore, it is necessary to make scratches so that nuclei are generated according to the desired particle diameter. It is well known that the surface shape of a base material generally determines the point of precipitation of a solid from the gas phase, and this phenomenon also occurs in the gas phase synthesis of diamond. Although it is possible to completely control the generation of nuclei by precisely digging rectangular grooves with a defined pitch, digging the grooves itself is expensive and is not economically desirable. For convenience,
It is possible to obtain approximately a predetermined grain size by rubbing with abrasive grains of a certain shape or by controlling the finished surface accuracy. In step (1) of this invention, the surface of the base material is mechanically polished to a predetermined surface roughness depending on the particle size of the particles to be grown and the distance between the clusters of particles in which the grown particles are densely packed. The characteristic requirement is to form.

Step (2) can be performed by any method as long as it is a gas phase synthesis method. For example, CVD method, plasma CVD method, IBD method (ion beam deposition method)
All such techniques can be used in this invention.
However, the temperature at which diamond particles form is
CVD and plasma CVD methods require temperatures of 500°C or higher, so consideration must be taken when selecting the base material. Furthermore, it is also possible to synthesize diamond locally by using a laser or an electron beam as a heat source or excitation source for a reaction, and such a method may be preferable in some cases.

In step (3), possible methods for separating the base material and diamond include mechanically dropping or melting the base material. Chemical methods are considered appropriate in order not to damage the shape of the obtained particles.

The diamond abrasive grains produced in the manner described above are not only polycrystalline, but also have a feature that the grain sizes are uniform with extremely high precision.

[Operations and Effects of the Invention] As described above, according to the present invention, the surface of the base material is mechanically formed to have a predetermined surface roughness depending on the interval and particle size of the grain groups to be grown. Polycrystalline diamond particles can be produced at low cost without the growth of diamond-shaped diamonds. In particular, polycrystalline diamond abrasive grains with excellent grinding properties can be produced industrially.

[Example] Examples of the present invention will be described below.

A Ni plate was used as the base material, and its surface was lapped with No. 3000 diamond abrasive grains. after that,
The surface of the Ni plate was scratched in one direction with 1200-grit abrasive paper. Diamond was synthesized on a substrate from hydrogen gas containing 2% CH ₄ by microwave plasma CVD. At this time, the substrate was heated to approximately 800°C. When the resulting particles were observed with a scanning electron microscope, they were found to have a predetermined particle size of about 10 to 15 μm, and each particle had a diameter of 7 to 15 μm.
It was confirmed that it consists of 15 crystal grains.

Diamond particles were recovered as a residue after dissolving this substrate in aqua regia, and when observed with a scanning electron microscope, the particles observed on the substrate were confirmed.

Claims (1)

[Claims] 1. Polycrystalline diamond abrasive grains in which polycrystalline diamond grains are obtained by growing polycrystalline grains spaced apart from each other as a dense grain group of grains having a predetermined grain size. , the surface of the base material, which will become a bed for diamond synthesized from a gas phase, is arranged in a predetermined plane according to the interval and the particle size so that diamond precipitation starts at a plurality of points. A polycrystalline material comprising the following steps: mechanically forming diamond particles on the surface of the base material from a gas phase; and separating the diamond particles from the base material. Method of manufacturing diamond abrasive grains. 2. The polycrystalline diamond abrasive according to claim 1, wherein the step of mechanically forming the surface of the base material to a predetermined surface roughness includes a step of smoothing and then scratching the surface of the base material. Method of manufacturing grains.