JPS62207869A - Parts coated with hard boron nitride containing oxygen - Google Patents

Abstract

PURPOSE:To improve the hardness of a coating film of hard boron nitride by incorporating oxygen into the film during deposition on the surface of a base materizal from a vapor phase so as to increase the amount of cubic or wurtzite type crystals. CONSTITUTION:A gaseous mixture cong. B2H6, NH3, H2 and N2O is introduced into a reactor. Microwaves are applied to the reactor to generate plasma and a base material is placed in the plasma to form a coating film contg. oxygen by 0.01-30atom% of the total amount of nitrogen and oxygen. Thus, parts coated with hard boron nitride contg. oxygen and having a cubic or wurtzite type crystal structure are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an oxygen-containing hard boron nitride coated part of a tool material used in cutting, plastic working, grinding, etc.

(Prior art) Cubic boron nitride has the second highest hardness after diamond, has high oxidation resistance, and has no reactivity with iron group metals, so it is used as a tool material for cutting, plastic working, etc. It is an extremely ideal material.

However, cubic boron nitride does not exist in nature, and its synthesis requires ultra-high pressure and high temperatures, so when considered as a tool material, it has limited shapes and is economically expensive. Therefore, its application as a tool material was limited. Recently, various techniques have been proposed for coating a thin film of cubic boron nitride by depositing cubic boron nitride on a gas phase surface without using ultra-high pressure or high temperature. According to this vapor phase coating technology, there are very few restrictions on the shape of the tool material, and it is economically inexpensive, so it can be used as a tool material that takes advantage of the excellent properties of cubic boron nitride. It is thought that this will expand significantly. The conventional technique for coating cubic boron nitride is to evaporate boron and evaporate nitrogen while heating the boron on the substrate, as shown in (II Japanese Patent Publication No. 1/2A, No. 2). A method for producing cubic boron nitride by simultaneously irradiating the substrate with an ion beam.

(21 Journal of Materials 5
science Letters If (/91r!;
') 3/-! ; A manufacturing method in which cubic boron nitride is deposited on a substrate by chemically transporting boron using a mixed plasma of hydrogen and nitrogen as shown in It.

f31 Proc, qth Symp on l5
IAT (Ion 5source and Ion As
5isted Technology) I! ,
As shown in Tokyo (/91J), E
(While evaporating boron with a CD gun (a type of electron gun),
A manufacturing method in which cubic boron nitride is coated on a substrate by ionizing nitrogen gas from a hollow anode, introducing it onto the substrate, and applying high frequency to the substrate to create a self-biasing effect.

etc. are known.

(Problems to be Solved by the Invention) A detailed study of cubic boron nitride-coated parts made using conventional technology reveals that the hardness of the coating film is, in fact, as hard as 9/-2000 or more on the Witzkers hardness. ultra high pressure,
The Witzkars hardness was extremely unsatisfactory compared to that of cubic boron nitride sintered bodies obtained at high temperatures. This is because the obtained film does not consist of a single phase of boron nitride with a completely cubic crystal structure, but has an extremely fine cubic or Wurtz crystal structure within the macrogonal boron nitride film. This is because the crystals of boron nitride, which have the same properties, are mixed together. Since the orthogonal boron nitride does not have the high hardness of boron nitride having a cubic or Wurtz crystal structure, coating films made in the prior art have had problems in terms of hardness.

It is an object of the present invention to solve these problems.

(Means for solving the problem) The fact that a large amount of hexagonal boron nitride is contained in the cubic boron nitride film deposited by the prior art is because hexagonal boron nitride is thermodynamically more stable at room temperature and pressure. It just reflects that.

In the conventional technology, each boron nitride constituent atom in the gas phase is excited to the highest possible energy state, and the excited state is used to synthesize hard boron nitride having a cubic or urushi-type crystal structure in a metastable phase. ing. However, in the conventional technology, it was difficult to avoid the presence of stable macrogonal boron nitride. In the conventional technology, boron atoms and nitrogen atoms are excited to a high energy state in the gas phase, and these excited species bond on or near the substrate surface, raising the energy level of both. Boron nitride is formed according to the energy level, but at this time, the mu bonds that form the SP2 hybrid orbital tend to be dominant, and the bonds that form the SP3 hybrid orbital occur at extremely limited energy levels. This is because it is nothing more than a . Therefore, in order to synthesize single-phase cubic boron nitride, the energy level of the excited species must be synthesized within a very limited region. For example, a double ion beam using a boron ion beam and a nitrogen ion beam simultaneously is required. Beam deposition (D, 1.B.

D) method, E which uses the cyclotron resonance of electrons that can keep the energy level in the plasma narrow.

A COR plasma OVD method or the like may be considered. However, all of these methods require large equipment,
-Less lethal.

The inventors investigated in detail the synthesis method of hard boron nitride and found that when oxygen coexists in the coating film, hard boron nitride with cubic and Wurtzian crystal structures can be formed under a wide range of energy levels. We obtained the knowledge that boron nitride can be preferentially synthesized.

(Function) The present invention is based on the knowledge that when synthesizing hard boron nitride, if oxygen is included in the boron nitride film, hard boron nitride having a cubic or Wurtzian crystal structure can be synthesized. . For example, BJH, gas θ2! ;vo1%,
NH3 gas □Jvo1%, remaining H2 gas,
The mixture was introduced into a quartz reaction vessel at a pressure of rOTorr, and 300 W of 2#j-GH microwave was applied to this vessel.
Plasma was generated by microwave non-polar discharge. Note that a substrate made of Si was placed in the plasma, and the substrate was heated to about qso'c by the plasma. Note that the oxygen partial pressure of the system was adjusted by mixing various concentrations of N20 gas into this mixed gas. Each tube was covered for 5 hours, and each was approximately 5μ
A coating film was obtained.

Phase identification was performed using electron beam reflection diffraction, X-ray diffraction, and ESCA using Rutherford, back, and scattering (R, B,
The amount of oxygen in the coating film was analyzed in S).

The results are shown in Table-/.

As is clear from Table-/, when oxygen coexists in the coating film,
The amount of cubic boron nitride present in the resulting coating film increases, and the atomic ratio of nitrogen and oxygen in the coating film increases.
It can be seen that if the amount is i% or more, the proportion of cubic boron nitride generated is sufficient. In addition, the oxygen content is 30%
If it exceeds 0, it is not preferable because a large amount of boron oxide is generated in the coating film. (Example 1) A cutting tip made of cemented carbide (I
SOK-10, model number SNG 32) was installed, and BzH6
0,2! ; vo [%e NH30,,! ; vol1
%, N,OO,01 voJ%.

Remaining H2, gas introduced at 90 Torr, ttoo w's ill! ; Plasma was generated using GHz microwaves. (The temperature of the chip was about qso0a>, and a coating film of about 5μ was obtained by coating for s hours. When the sample was examined by X-ray diffraction, cubic boron nitride was detected. With this sample, the following conditions were applied. A cutting test was conducted.

Work material SCM≠／! ; (HRc -5) Cutting speed 10om/= Feed rate O,/m depth/re
v Notch as holder FN//R-#≠A Cutting material Flank wear was o, or as after cutting for 70 minutes using a water-soluble cutting material.

Note that a sample made in the same manner as above without introducing N20 could be cut for only 2 minutes and 31 r seconds under these conditions. For comparison, when an uncoated cemented carbide base material was similarly cut, the cutting edge was melted away in 32 seconds.

(Example 2) 11th N ion brating device (1 is a vacuum chamber, 2
is a cathode, 3 is a base material, 4 is an ion electrode, and 5 is a water-cooled crucible (
), 6 is an electron gun, 7 is an exhaust hole, 8
is Ar+N2. gas introduction hole, 9 is 0 gas introduction hole, 1
0 is a waveguide, 11 is a microwave oscillator, 12.13 is a direct current electric J,), variously adjust the 02 partial pressure in the prefecture,
Boron nitride was coated onto a Si substrate.

In addition, the ionization voltage is +SOV, the bias voltage is -1,
, 5' kV, introduced gas is NLj□vo1%, pressure cover in the system is 1,! ; At Xlo-JTorr, the substrate temperature is g
02 gas is turned into plasma by microwave discharge at 24'3 GHz.

O2 partial pressure in the system, O1 information in the obtained membrane, and rt
The uul results are shown in Table 2.

Table 2 (Effects of the invention) When synthesizing and coating hard boron nitride, if a predetermined amount of oxygen is contained in the coating film, the hard boron nitride with cubic and Wurtzian crystal structures present in the coating film This has the effect of significantly increasing the amount of boron nitride present.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an ion blating apparatus used in an embodiment of the present invention. 1... Vacuum chamber, 2... A is the pole, 3... Base material, 4...
- Ionization electrode, 5... Water-cooled crucible (contains boron metal), 6... Electron gun, γ... Exhaust hole, 8...
Ar+N gas introduction hole, 9...0 Yugas introduction hole, 10
...Waveguide, 11...Microwave oscillator, 12.1
3...DC power supply.

Claims (1)

[Claims] 1. In a hard boron nitride-coated part in which a coating film is deposited on the surface of a base material from a gas phase, oxygen is present in the hard nitride coating film in an atomic ratio of 0.5% of the total amount of nitrogen and oxygen. 01%~3
An oxygen-containing hard boron nitride coated part characterized by containing 0% oxygen.