JPH0224005A - Diamond coated tool and manufacture thereof - Google Patents

Abstract

PURPOSE:To manufacture a diamond coated tool at low cost by forming a diamond film by using a silicon nitride substrate having the needle crystal structure that the surface becomes a silicon carbide by the vapor phase developing method utilizing a low temp. plasma. CONSTITUTION:A low temp. plasma is generated by a microwave on the substrate 5 of a silicon nitride 4 having a needle crystal structure whose surface becomes a silicon carbide 3, for instance, an ethanol is used for a raw material gas and the composite time is taken for ten hours in total of three hours with 4SCCM of the flow, 36SCCM hydrogen gas flow, 200W microwave output and 30Torr gas pressure, and 7 hours with 300W microwave output and 40Torr gas pressure. In this case the detection of Si is not found nor of the needle structure of the silicon nitride, and a diamond coating is found. For instance no crack was generated even in case of 3000m cutting with an aluminum alloy being machined at 60m/min cutting speed and 0.5mm depth of cut max.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a diamond-coated tool used for cutting and grinding aluminum manufactured by a vapor phase growth method using low-temperature plasma using a specific substrate, and the like. Regarding the manufacturing method.

(Prior Art) It is generally well known that diamond-coated tools are the most suitable tools for cutting and grinding aluminum. Many of these diamond-coated tools are made of diamond grains that are artificially synthesized under high temperature and pressure and are hardened with a resin or metal binder. However, because synthesis under high temperature and high pressure is very expensive, and because diamond grains are hardened very much in the inner layer, attention has recently been focused on the vapor phase growth method, which can easily synthesize diamonds at low cost. It is being

This vapor phase growth method includes a method using high temperature plasma and a method using low temperature plasma. The method of using high-temperature plasma is to heat a mixed gas of methane, hydrogen, and argon to 10,000 degrees using high frequency or DC power.
This is a method in which diamond is deposited on a substrate with a temperature of around 900 degrees, and a method using low-temperature plasma involves heating a mixed gas of methane or organic solvent and hydrogen to around 900 degrees using a tungsten filament or microwave. This method uses heating and excitation to precipitate diamond onto a substrate.

Note that the substrates used as diamond-coated tools have conventionally been made of tungsten carbide, tantalum, alumina, and silicon nitride.

(Problems to be Solved by the Invention) However, the conventional diamond-coated tool has the following drawbacks in its manufacturing method.

■ In the pretreatment of substrates used as diamond-coated tools, they had to be polished with diamond abrasive grains in advance.

Among the methods using high-temperature plasma, in the method using high frequency and the method using low-temperature plasma, if the substrate is not polished with diamond abrasive grains in the pretreatment, will diamond not be deposited on the substrate at all? Even if it were to be precipitated, the number of particles would be about 100,000 per square centimeter at most, and no precipitation would occur as a film, so it could not be used as a tool because it was not coated with diamond.

■ Synthesizing equipment becomes expensive.

Although the method using high-temperature plasma is simpler than the method of artificially synthesizing at high temperature and high pressure, it is still expensive.

Therefore, in order to synthesize at a lower cost than the above-mentioned drawbacks (1) and (2), the only way is to use low-temperature plasma, and in that case, the substrate must be polished with diamond abrasive grains as a pretreatment.

However, these diamond abrasive grains were also synthesized artificially under high temperature and high pressure, leading to the conclusion that diamond cannot be synthesized artificially without using expensive diamond synthesis methods.

An object of the present invention is to provide a diamond-coated tool that can be provided at low cost without using any of the expensive synthesis methods described above, and a method for manufacturing the same.

(Means for Solving the Problems) The present invention has been made to solve the above problems and is configured as follows.

The diamond-coated tool of the present invention is a diamond-coated tool formed by forming a diamond coating film on the silicon carbide surface of a silicon nitride substrate having an acicular crystal structure in which one surface is made of silicon carbide.

To explain the diamond-coated tool of the present invention with reference to FIG. This is a diamond-coated tool in which a diamond-coated film 1 is formed on a diamond-coated tool.

A method for manufacturing a diamond-coated tool according to the present invention.

This is a method of manufacturing a diamond-coated tool using a silicon nitride substrate with an acicular crystal structure whose surface is made of silicon carbide by a vapor phase growth method using low-temperature plasma.

Next, the properties of the diamond-coated tool of the present invention and its manufacturing method will be illustrated by the following examples.

Example 1 A substrate 5 of silicon nitride 4 having an acicular crystal structure whose surface is silicon carbide 3 as shown in FIG. 1, and a substrate 5 of silicon nitride 4 having an acicular crystal structure as shown in FIG. We conducted a comparative experiment using Note that polishing with diamond abrasive grains, which is a pretreatment of the substrate, was not performed in either case.

Low-temperature plasma was generated using microwaves under zero synthesis conditions and a microwave output of 300 (W).

Synthesis was carried out for 5 hours at a gas pressure of 40 (Torr), using ethanol as a source gas, an ethanol flow rate of 4 (SccM), and a hydrogen gas flow rate of 36 (SccM).

After synthesis, microscopic observation was performed to count the number of diamond nuclei per unit area. The results were as follows. Here, the substrate 5 in FIG. 1 is sample 1, and the substrate 5 in FIG. 2 is sample 2. The substrate 5 in FIG. 3, that is, the substrate 5 in FIG. 2 before diamond synthesis is defined as sample 3.

On sample L 6.0X10' (pcs/cd) On sample 2 5.0XIO' (pcs/-) Example 2 Microwave output 200 (W), gas pressure 30 (Torr
) for 3 hours, microwave output 300 (W), gas pressure 4
Synthesis was carried out under the same conditions as in Example 1 except that the synthesis time was 7 hours at 0 (Torr) for a total of 10 hours.

After the synthesis, Si was detected by EPMA.

In sample 1, no Si was detected. In sample 2, Si was detected to the same extent as in sample 3.

Similarly, the sample after synthesis was observed under a microscope.

In sample 1, no acicular structure of silicon nitride was observed, and diamond coating film 1 was observed. In sample 2, diamond grains 2 were found scattered on the acicular structure of silicon nitride.

Similarly, sample 1 after synthesis was analyzed by X-ray diffraction and laser Raman spectroscopy, and both analyzes matched the peak of natural diamond.

Example 3 The aluminum alloys of Sample 1 and Sample 3 synthesized in Example 2 were cut.

The cutting speed was 60 m/akin and the depth of cut was 0.5 m.

As a result, sample 3 suffered from chipping after 1000 m of cutting, while sample 1 did not show any chipping even after 3000 m of cutting.

(Effects of the Invention) The following excellent effects can be obtained by this invention.

■ Diamond-coated tools can be manufactured at low cost.

Because it uses low-temperature plasma, it is more suitable for electricity and buildings than artificial high-pressure methods or methods that use high-temperature plasma.

This is because the cost of materials is less than one-tenth.

Also, in mass production, it is possible to avoid using diamond abrasive grains used in polishing.

■ It becomes a simple manufacturing method.

Because it is not polished with diamond abrasive grains during pre-treatment,
This is because there is no need to perform a polishing process and a cleaning process to remove diamonds after polishing. This difference becomes even more noticeable especially when mass production begins.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a diamond-coated tool of the present invention.
Figure 2 is a longitudinal cross-sectional view of a conventional diamond-coated tool;
The figure is a longitudinal sectional view showing the substrate of FIG. 2 before diamond synthesis. 1... Diamond coating film, 2... Diamond grains. 3...Silicon carbide, 4...Silicon nitride with acicular crystal structure, 5...Substrate, Fig. 1

Claims (1)

[Scope of Claims] 1. A diamond-coated tool formed by forming a diamond coating film on the silicon carbide surface of a silicon nitride substrate having an acicular crystal structure whose surface is silicon carbide. 2. A method for manufacturing a diamond-coated tool using a silicon nitride substrate with an acicular crystal structure whose surface is made of silicon carbide by a vapor phase growth method using low-temperature plasma.