JPH0774449B2 - Method for producing diamond-coated hydrogen-brittle metal - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hydrogen-brittle metal whose surface is coated with a diamond thin film and a method for producing the same.

[Conventional technology]

Diamond has been conventionally synthesized from a thermodynamically stable state at high temperature and high pressure, but recently, thin film diamond has been synthesized on a substrate at low pressure or normal pressure by a chemical vapor deposition method.

In such a chemical vapor phase synthesis method (so-called CVD method), a mixed gas of hydrocarbon and hydrogen is used. For example, thermal filament (Japanese Patent Laid-Open No. 58-91100), microwave non-polar discharge (Japanese Patent Laid-Open No. 58-58100).
-110494), hydrogen plasma (JP-A-58-135117), microwave plasma (JP-A-59-30398), ultraviolet irradiation (JP-A-60-112697) and the like. Are excited to form a diamond thin film on the substrate. Further, recently, a method of using alcohol or the like as a carbon source or a method of increasing a film formation rate by applying a DC bias (JP-A-59-35092) has been proposed. In any of the above methods, a condition for forming a diamond thin film having good crystallinity is to use a mixed gas prepared by diluting hydrocarbon with 10 times or more hydrogen to prevent precipitation of amorphous free carbon, and the substrate temperature is 700 to It is said to be 1000 ° C.

By forming a diamond thin film with good crystallinity on the surface of metal or ceramics in this way, it is possible to improve wear resistance and reduce the friction coefficient, so diamond coating materials are used for cutting tools and mechanical It is used in applications such as seals, speaker diaphragms, and integrated circuit boards.

However, titanium and zirconium, or their alloys,
Further, it has been impossible to form a diamond thin film on a hydrogen-brittle metal such as nickel-chromium steel and other tough steel. Titanium, zirconium, or their alloys have high specific strength, and are generally used as materials for aviation and space engineering, etc., and tough steels are generally used as structural materials and tool materials. However, since these metals are called hydrogen embrittlement metals and are chemically very active, the conventional CVD method carried out in a reducing atmosphere using hydrocarbons and hydrogen as raw materials reacts with carbon and hydrogen to cause an incompatibility. This is because it forms stable and brittle carbides such as titanium carbide and hydrides such as titanium hydride.

Therefore, even if the diamond thin film is coated on the surface of the hydrogen embrittlement metal by the CVD method, the characteristics and shape of the hydrogen embrittlement metal are impaired due to the formation of carbides or hydrides, and the diamond thin film with good adhesion cannot be formed. . or,
When the hydrogen-brittle metal substrate has a thickness of 5 mm or less, or is exposed to the plasma of the source gas for a long time, the formation of carbides and hydrides is severe, and the substrate itself is damaged. It was also possible.

[Problems to be Solved by the Invention]

As described above, in the conventional chemical vapor deposition method using a mixed gas of hydrocarbon and hydrogen, the hydrogen-brittle metal produces carbides and hydrides, so the hydrogen-brittle metal is coated with a diamond thin film having good adhesion. It was impossible.

In view of such conventional circumstances, it is an object of the present invention to provide a hydrogen-brittle metal whose surface is coated with a diamond thin film having good adhesion.

[Means for Solving the Problems]

To achieve the above object, in the method for producing a diamond thin film-coated hydrogen-brittle metal of the present invention, the surface of the hydrogen-brittle metal, titanium carbide and nitride, silicon and silicon carbide, nitride, boron and boron carbide, Nitride, and a single layer or a plurality of intermediate layers selected from the group consisting of aluminum nitride, to form a layer in contact with at least hydrogen embrittlement metal by physical vapor phase synthesis method, then on the intermediate layer The feature is that a diamond thin film is formed by a chemical vapor deposition method.

Therefore, the diamond thin film-coated brittle metal of the present invention obtained by the above method is a hydrogen-coated metal, and a carbide and nitride of titanium formed on the surface of the hydrogen-brittle metal with good adhesion,
A single layer or a plurality of intermediate layers selected from the group consisting of silicon and silicon carbide, boron nitride and boron carbide, nitride, and aluminum nitride, and a diamond formed on the intermediate layer with good adhesion. It consists of a thin film.

In the present invention, the hydrogen-brittle metal includes titanium, zirconium, alloy containing 5% by weight or more of titanium or zirconium, nickel, chromium and molybdenum.
It means a tough steel containing less than or equal to wt%.

In the method of the present invention, the physical vapor deposition method (so-called PVD method) for forming the intermediate layer includes vapor deposition, sputtering, ion plating, etc., and the chemical vapor deposition method for forming the diamond thin film (CVD method) is thermal Filament law,
All conventionally known CVD methods such as a microwave plasma CVD method, a high frequency plasma CVD method, an ultraviolet excitation method, or a method combining these can be used. Note that ordinary reaction conditions are used for both the PVD method and the CVD method.

[Action]

In the present invention, the diamond thin film is not directly formed on the surface of the hydrogen-brittle metal, but is formed via the intermediate layer having excellent adhesion to the hydrogen-brittle metal, so that the diamond thin film having good adhesion can be obtained.

As the intermediate layer, titanium carbides and nitrides, silicon and silicon nitrides, carbides, boron and boron carbides, nitrides, and aluminum nitrides, which have excellent adhesion to both hydrogen-brittle metal and diamond thin film, are used. The thing is preferable and it may be a single layer or multiple layers which consist of these substances. In particular, the intermediate layer in contact with the diamond thin film is preferably silicon carbide, silicon nitride, or silicon in terms of adhesion.

When the normal CVD method is used to form the intermediate layer, a reducing atmosphere containing active carbonization or hydrogen is used,
As in the case of directly forming a diamond thin film, the characteristics and shape of the hydrogen embrittlement metal are impaired by the formation of carbides and hydrides, and an intermediate layer having good adhesion cannot be obtained. Therefore,
By using the PVD method for forming the intermediate layer in the method of the present invention, the intermediate layer having good adhesion can be formed on the surface of the hydrogen-brittle metal without damaging it.

As a result of forming the intermediate layer on the surface of the hydrogen-brittle metal in this way, the diamond thin film formed thereon can be formed by the ordinary CVD method. That is, since the above-mentioned intermediate layer does not react with carbon or hydrogen in the reducing atmosphere used in the ordinary CVD method for synthesizing a diamond thin film, the hydrogen embrittlement metal of the lower layer becomes brittle or its characteristics deteriorate, or its shape changes. It is possible to form a diamond thin film having good crystallinity as the uppermost layer with good adhesion without causing the above phenomenon.

〔Example〕

A hydrogen brittle metal having the shape shown in Table 1 below was surface-finished with # 600 diamond powder to prepare a substrate.

On the surface of this substrate, PVD the intermediate layer of the first layer shown in Table 1
One type of magnetron sputtering method (PVD-M
S method or abbreviated) or ion plating method (abbreviated as PVD-IP method) was used to form under normal conditions. As shown in Table 1, an intermediate layer of a second layer was formed on some of the samples under the usual conditions by using the PVD-MS method, the PVD-IP method or the CVD method.

After surface finish of the surface of the intermediate layer formed substrate with diamond powder # 600 of the thus single layer or plural layers, diamond CH ₄ gas and H ₂ gas as a raw material by a CVD method as shown in Table 1 A gas phase reaction for coating was performed. The CVD method used is the microwave plasma CVD method (abbreviated as μ-PCVD method) shown in FIG. 1 and the high frequency plasma CV shown in FIG.
D method (abbreviated as RF-PCVD method), DC plasma combined thermal filament method (abbreviated as F-PCVD method) or thermal filament CVD method (abbreviated as F-CVD method) shown in FIG. 3, and shown in FIG. DC
Any of the plasma CVD methods (abbreviated as DC-PCVD method), and the optimum reaction conditions other than those shown in Table 1 were selected.

It was confirmed by any of X-ray diffraction, RHEED (high-speed electron beam diffraction) and Raman spectroscopic analysis that the diamond thin films of Sample Nos. 1 to 15 formed as described above were crystalline diamond. For example, the Raman spectrum obtained for sample No. 6 is shown in FIG.
A Raman line of 2.5 cm ^-1 appears clearly, which indicates that the diamond has a very good crystallinity. Furthermore, sample No. 1-10
By ion plating on the diamond thin film of
The electric resistance of each diamond thin film was 1.0 × 10 ^{9 to} 1.0 × 10 ¹³ Ω · cm, which was obtained by measuring Ti / Au electrodes and using the substrate as the other electrode to measure the VI characteristics between the two electrodes. It was or,
The diamond thin films of Sample Nos. 1 to 15 all had Vickers hardness (load: 500 g) of 10000 kg / mm ² or more.

Regarding the samples Nos. 1 to 15 obtained as examples of the present invention, the states of the base material and the diamond thin film were examined, and Table 1 is summarized together with the method for forming the intermediate layer and the diamond thin film. Further, as a comparative example, the same items as in the present invention example are also shown in Table 1 for the samples (No. 16 to 23) in which the intermediate layer was not formed and the diamond layer was directly formed on the surface of the substrate.

From Table 1, among the examples of the present invention, sample Nos. 1 to 10 and 1 in which the intermediate layer in contact with the diamond thin film was SiC, Si ₃ N ₄ or Si.
In Nos. 2 and 13, a diamond thin film having excellent adhesion can be formed on the surface of the base material, but it can be seen that Sample No. 11 in which the intermediate layer in contact with the diamond thin film is TiC is slightly inferior in adhesion.
On the other hand, in the comparative example without the intermediate layer, samples No. 16, 17 and No.
Although diamond thin films were obtained in Nos. 22 and 23, adhesion was extremely low because a large amount of hydrogen was taken in the surface of the substrate and carbides and hydrides were generated on the surface. The diamond thin film was not formed by changing to carbide or hydride.

Incidentally, among the materials of the intermediate layer according to the present invention, the materials not exemplified in Table 1 are slightly inferior in adhesiveness as the intermediate layer in contact with the diamond thin film, but are effective as other intermediate layers. It was

〔The invention's effect〕

According to the present invention, since the intermediate layer formed by the PVD method is present between the hydrogen embrittlement metal and the diamond thin film, there is no formation of carbides or hydrides even by the ordinary CVD method and the characteristics of the hydrogen embrittlement metal. A diamond thin film having good crystallinity can be formed with good adhesion without damaging the shape. In particular, even if the hydrogen-brittle metal has a thickness of 5 mm or less, for example, about 0.04 mm, it can be coated with the diamond thin film.

Therefore, the diamond-coated hydrogen-brittle metal of the present invention has both the characteristics of the surface diamond and the characteristics of the hydrogen-brittle metal inside, and is used in aircraft materials, space optical materials, nuclear engineering materials, cutting tool materials, mechanical seals, etc. It can be used as a material requiring abrasion resistance, a material requiring a high specific elastic modulus such as a diaphragm of an acoustic speaker, and a material requiring a low dielectric constant such as an integrated circuit board.

[Brief description of drawings]

Fig. 1 is a conceptual diagram showing a microwave plasma CVD device, Fig. 2 is a conceptual diagram of an RF plasma CVD device, Fig. 3 is a conceptual diagram of a thermal filament CVD device that can be used with DC plasma, and Fig. 4 is a DC plasma CVD device. FIG. 5 is a conceptual diagram of the apparatus, and FIG. 5 is a Raman spectrum of the diamond thin film of sample No. 6 of the example. 1 ... Substrate, 2 ... Quartz tube 3 ... Vacuum exhaust port, 4 ... Gas inlet port 5 ... Magnetron, 6 ... Waveguide 7 ... Plunger, 8 ... Plasma 9 ... RF electrode, 10 …… Coil 11 …… Supporting base, 12 …… Cooling water 13 …… Filament, 14 …… Insulating seal 15 …… AC electrode, 16 …… DC electrode 17 …… Cathode

Claims (1)

[Claims] 1. A surface of a hydrogen embrittlement metal made of titanium or zirconium, an alloy containing 5% by weight or more of titanium or zirconium, or a tough steel containing nickel, chromium or molybdenum in an amount of 5% by weight or less. A layer in contact with at least a hydrogen-brittle metal among intermediate layers of a single layer or a plurality of layers selected from the group consisting of nitrides, silicon and carbides and nitrides of silicon, boron, carbides and nitrides of boron, and nitrides of aluminum. Is formed by a physical vapor phase synthesis method, and then a diamond thin film is formed on the intermediate layer by a chemical vapor phase synthesis method.