JPH0333085A - Diamond coated combined body - Google Patents

Abstract

PURPOSE:To obtain a diamond coated combined body useful as a cutting tool, a high performance heat radiating substrate, etc., without requiring post- machining such as polishing by forming a smooth diamond film on the surface of a cubic boron nitride sintered body having prescribed purity, grain size and surface smoothness. CONSTITUTION:A smooth diamond film having <=0.05mum surface roughness Ra is formed by epitaxial growth on the surface of a cubic boron nitride sintered body having >=98mol% purity, <=10mum grain size and <=0.05mum surface roughness Ra to obtain a diamond coated combined body.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a diamond-coated composite useful as a cutting tool with good wear resistance and a high-performance heat dissipation substrate.

[Conventional technology]

Diamond synthesis methods include Fe and Ni.

5 to 7 GPa of graphite using Co as a catalyst, 130
A static ultra-high pressure method in which the process is carried out at high temperatures and pressures of 0 to 2000°C, and a dynamic ultra-high pressure method in which graphite is directly converted into diamond by shock waves such as explosions are known. In addition to these methods, a chemical vapor deposition method using a carbon-containing gas as a raw material at a relatively low temperature and low pressure has recently been developed and is attracting particular attention. In this chemical vapor deposition method, a gas mixture of carbon-containing gas and hydrogen is introduced into a reaction tank, and the mixture of carbon-containing gas and hydrogen is activated by thermionic radiation or plasma, and then deposited on a heated substrate. It is used to precipitate diamonds.

An example of using thermionic radiation is JP-A-58-9110.
0, and Japanese Patent Application Laid-open No. 110494/1984 as an example using microwave plasma.

[Problem to be solved by the invention]

When forming a diamond film by chemical vapor deposition, it is possible to form a diamond film with a smooth surface by using a diamond single crystal as the substrate, but the available single crystal diamond is only a few squares in size. Moreover, it is expensive because it requires high-temperature and high-pressure treatment at 1600° C. and 6 GPa or more, which takes time.

Furthermore, when a diamond film is used as a cutting tool and a heat dissipating substrate, the base must be processed into those shapes, but such processing requires a great deal of time.

On the other hand, when silicon, molybdenum, tungsten carbide, etc. are used for the substrate as a material other than diamond single crystal, the formed film is a polycrystalline film due to multinucleation generation, and the film surface has a surface smoothness. Ra: 0
．． Since it has irregularities of 1 μm to several μm, it was necessary to process and polish the surface irregularities to make it smooth in order to use it as a cutting tool or a heat dissipation substrate.

For example, Japanese Patent Application Laid-Open No. 62-278181 discloses that the surface of a base material made of a sintered body containing cubic boron nitride is
A diamond-coated tool member is disclosed in which a coating layer made of diamond and/or diamond-like carbon is formed with a thickness of ~40 μm, but the coating layer made of diamond-like carbon is formed by multinucleation, so it is not a smooth diamond. Unable to form a film.

Furthermore, in order to smooth the surface, diamonds have traditionally been mechanically polished using cast iron (so-called scaife polishing), but this method is not suitable for diamond films, which have weak bonding strength with the substrate. Moreover, it took a long time.

Furthermore, a method of polishing a diamond film using a thermochemical reaction has recently been proposed, but polishing takes a long time and the fundamental problem has not been solved.

Therefore, it is an object of the present invention to propose a diamond-coated composite having a smooth surface without requiring post-processing such as polishing.

[Means to solve the problem]

That is, the present invention has a purity of 98 mol% or more and a particle size of 101
! The substrate is a cubic boron nitride sintered body with a surface smoothness Ra of 0.05 μm or less, and a surface smoothness Ra of 0.05 μm or less.
: A diamond-coated composite characterized by having a smooth diamond film of 0.05 μm or less.

The present invention will be explained in more detail below.

The reason why a diamond film on a diamond single crystal grows epitaxially is that the substrate and the diamond film are made of the same material and have a negative lattice constant.

The lattice constant of cubic boron nitride (hereinafter referred to as cBN) is
It has a lattice constant of 0.36162 nm, which is very close to the lattice constant of diamond, which is 0.35667 nm. c B N (1
The degree of mismatch (misfit factor) between the lattice constants of the diamond (00) plane and the diamond (100) plane is L4%.

Since the lattice mismatch is small in this way, it becomes possible to grow diamond heteroepitaxially on the cBN single crystal.

Also, the thermal expansion coefficients of cBN and diamond are 4.5xlO-' and 4.3x10-hK-', respectively.
(750″C), so when used as a cutting tool, interfacial peeling or cracking due to the difference in thermal expansion coefficient that occurs during cutting is unlikely to occur.

In the present invention, the purity is 98 mol% or more and the particle size is 10 μm.
Above, surface smoothness Ra: cB of 0.05 μm or less
It has been discovered that by using a N sintered body as a substrate, it is possible to form a diamond film with a smooth surface.

(Function) If the purity of the cBN sintered body is less than 98 mol%, the synthesis catalyst remains at the grain boundaries, and the particles of the sintered body are separated by the catalyst at the grain boundaries. This causes multinucleation of diamond, making it impossible to form a diamond film with a smooth surface, and also reduces the adhesion between the cBN substrate and the diamond film to be formed.

When the size of the substrate is the same, as the grain size becomes smaller, the number of grain boundaries increases and multi-nucleation of the formed diamond is likely to occur. Therefore, in the present invention, the grain size is limited to 10 μm or more. If the particle size is less than 10 μm, a diamond film with a smooth surface cannot be formed.

Furthermore, since diamond grows on the surface of the cBN sintered body, the surface smoothness of the diamond film is influenced by the surface smoothness of the base and becomes comparable to that of the base. As a result of examining the relationship between the surface smoothness of the cBN sintered body that is the base and the smoothness of the diamond film formed, it was found that the surface smoothness of the base is R.
It has been found that when a exceeds 0.05 μm, the smoothness of the surface of the diamond film formed decreases markedly, so the surface smoothness of the substrate is limited to Ra: 0.05 μm or less.

In order to obtain the cBN sintered body according to the present invention, for example, a pyrolytic boron nitride (P-BN) plate is mixed with boron trichloride, boron tribromide, and other borides and ammonia and other nitrogen. The P-BN is synthesized by chemical vapor deposition (CVD) using the contained gas as a raw material gas, and the resulting P-BN is diffused and impregnated by heat treatment using an alkaline earth metal nitride such as MgzBI'h as a synthesis catalyst. high-temperature, high-pressure treatment (e.g., JP-A-63-
260865)).

The cBN sintered body thus obtained is processed into a desired shape such as a cutting tool member or a heat dissipating substrate, and processed and polished to a surface smoothness of Ra: 0.05 μm or less to obtain a base body.

In order to produce the diamond-coated composite of the present invention, the cBN sintered body substrate is placed in a reaction layer, and a mixed gas of hydrogen and a carbon-containing gas such as methane, propane, acetylene, methanol, or ethanol is introduced into the reaction tank. CBN sintering is carried out by introducing a mixed gas of carbon-containing gas and hydrogen into an activated state by thermionic radiation from a filament such as tungsten, microwaves, or high-frequency plasma, and heating the mixture to 00 to 00°C. Diamonds are deposited on the upper body. The surface smoothness of the deposited diamond film is Ra
: Since it has a smooth surface of 0.05 μm or less, it can be used as it is as a cutting tool member or a heat dissipation substrate.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Fruit 1 Tsu0- Temperature 1900 using boron trichloride and ammonia as raw material gas
°C1 pressure 200 Pa, deposition rate 1100tt/h
CVD was performed under the conditions of r to obtain a P-BN plate, which was then coated with MgJ
z powder and held at 1200°C for 8 hours in a N2 stream to diffusely impregnate 0.5 mol% MgJNl. This is heated in a belt-type high pressure generator using a 1.600″C15,8
A sintered body was obtained by performing high temperature and high pressure treatment at GPa for 30 minutes.

When the generated phase of this sintered body was identified by XvA diffraction method, it was confirmed that it was a cBN sintered body. Further, by reflection electron microscopy and impurity analysis, it was confirmed that the particle size was 50 μm and the purity was 99.3 mol%.

This cBN sintered body was cut into 5 mm squares and 0.5 mm squares, and lapped to a surface smoothness of Ra: 0.030 μm.

Using the cBN sintered body as a substrate, a diamond film was formed as a bottom film in a microwave plasma CVD apparatus.

The total flow rate is 200cm using methane and hydrogen as raw material gases.
'/min (Standard condition; 0°C-1 atm: Below r S
CCM J), methane partial pressure 67 Pa, hydrogen methane partial pressure ratio 59, and 2.45 from a microwave oscillator.
GIlz microwave was oscillated at 400 W and guided into the reaction chamber through a waveguide to generate plasma around the substrate and maintain the substrate temperature at 850°C. After 5 hours, the entire substrate has a thickness of 5 μm.
A smooth diamond film of m was formed. The surface smoothness of the formed diamond film is Ra: 0.035μ
It was m.

A diamond film was formed on the substrate surface of a cBN sintered body produced in the same manner as in Example 1 by thermionic method.

In other words, using methane and hydrogen as raw material gases, the total flow rate is 2
005CCM, methane partial pressure 67 Pa, hydrogen methane partial pressure ratio 59, and filament temperature for thermionic emission 2.
000°C1 The temperature of the substrate was maintained at 850°C.

After 5 hours, a smooth diamond film with a thickness of 5 μm was formed on the entire surface of the substrate.

The surface smoothness of the formed diamond film is Ra:
It was 0.040 tta.

A diamond film was formed on the substrate surface of a cBN sintered body produced in the same manner as in Example 1 in a microwave plasma CVD apparatus.

That is, using methane and hydrogen as raw material gases, the total flow rate was 200 SCCM, the methane partial pressure was 67 Pa, the hydrogen-methane partial pressure ratio was 59, and the microwave oscillator was used to generate 2.45
A GHz microwave was oscillated at 400 W and guided into the reaction chamber through a waveguide to generate plasma around the substrate and maintain the substrate temperature at 950°C. After 5 hours, a thickness of 5μ is applied to the entire surface of the substrate.
A smooth diamond film of m was formed.

The surface smoothness of the shaped diamond film is Ra: 0
．． It was 040tIm.

A diamond film was formed in the same manner as in Example 1, except that the substrate was made of polished tungsten carbide having a size of 5 mm x 0.5 mm and a surface smoothness Ra of 0.035 μm.

As a result, after 5 hours, a diamond film with a thickness of 5 μm was formed on the entire surface of the substrate, and the surface smoothness was Ra: 0.
．． It was 55 μm.

A diamond film was formed in the same manner as in Example 1, except that a non-glare silicon single crystal was processed to have a 5 n+m square x 0.5+aa+ and a surface smoothness Ra of 0.030 μm as a substrate.

As a result, after 5 hours, a diamond film with a thickness of 5 μm was formed on the entire surface of the substrate, and its surface smoothness was Ra: 0.
It was 52ttm.

This (Iwagumi) has a surface smoothness of Ra: 0.070 ttm.
A diamond film was formed in the same manner as in Example 1 except that a N sintered body was used as the substrate. As a result, a diamond film with a thickness of 5 μm was formed on the entire surface of the substrate after 5 hours.
Its surface smoothness was Ra: O, I51zm.

(Wadasu) A P-BN plate diffused and impregnated with Mgi BH3 was obtained in the same manner as in Example 1, and it was heated in a belt-type high pressure generator for 1
．． High temperature and high pressure treatment was performed at 400° C. and 4.5 GPa for 30 minutes to produce a cBN sintered body with a particle size of 5 μm and a purity of 99.3 mol%.

It was processed to have a 5111Il angle X0.5+nn+ and a surface smoothness Ra: 0.05 μm to obtain a substrate.

A diamond film was formed in the same manner as in Example 1 except that this substrate was used. After 5 hours, a diamond film with a thickness of 5 μm was formed on the entire surface of the substrate, but cB
Since the grain size of the N sintered body was too small, the surface smoothness of the diamond film was Ra: 0.10 μm.

This 1 u glue was 2.5 mol% by changing the catalyst impregnation time in Example 1.
After obtaining a P-BN plate diffused and impregnated with MgzBNs of Obtained.

This is 5nIII angle x 0.5mm, surface smoothness Ra
: Processed to 0.040 μm as a substrate, a diamond film was formed in the same manner as in Example 1. After 5 hours, a diamond film with a thickness of 5 μm was formed on the entire surface of the substrate, but cBN Since the purity of the sintered body was low, the surface smoothness of the diamond was Ra: 0.10 μm.

Using the inventive product of Example 1.2 and the comparative product of Comparative Example 1, a workpiece material of 80% Af-20% Si was cut at a cutting speed of 350III/ll1n, a depth of cut of 0.5 mm, and a feed rate. A cutting test was attempted under the conditions of 0.1 mm/rev and cutting time of 10 min.

The comparison product had minute chipping accompanied by peeling of the coating layer, whereas the product of the present invention showed normal wear. Also,
The surface smoothness of the workpiece cut with the comparison product is Ra: 0
．． In contrast, the surface smoothness of the workpiece cut with the product of the present invention was 0.05 μm.

Practical Works Metallized layers of a first layer of Ni and a second layer of Au were shaped by the ion beam penta method on the product of the present invention in Example 3 and used as a heat dissipation substrate.

After operating the 50 mW semiconductor laser for 1000 hours,
No deterioration of laser output was observed. On the other hand, comparative example 2
．． No. 3, 4.5 could not be used as a heat dissipation substrate without post-processing.

〔Effect of the invention〕

The present invention is a coated composite having a smooth diamond film on a cBN sintered body as a base, and although the manufacturing time is significantly shortened because no post-processing is required, the adhesion between the base and the diamond film is It has the effect of being strong. The present invention can be expected to be used as a cutting tool or a heat sink with high thermal conductivity.

Claims (1)

[Claims] 1. The substrate is a cubic boron nitride sintered body with a purity of 98 mol% or more, a grain size of 10 μm or more, and a surface smoothness Ra of 0.05 μm or less, and a smooth diamond film with an Ra of 0.05 μm or less on the surface. Features a diamond-coated composite.