JP2709150B2 - Coating method of vapor phase diamond - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for coating a surface of a cemented carbide with diamond by vapor deposition, and more particularly to a coating method for improving the adhesion between a cemented carbide and diamond.

[Prior art] TiC, TiN on the surface of cemented carbide used as a cutting tool
The method of applying a coating such as
Attempts have been made to coat the diamond with the highest hardness in the material.

In this case, most of the cemented carbide contains Co, Ni,
Fe tends to decrease the adhesion between the cemented carbide and diamond. Conventionally, to prevent this, Co, Ni, Fe, etc. are dissolved and removed from the surface of the cemented carbide by acid treatment,
Recently, a method of heat treating the surface of a cemented carbide in an atmosphere containing alcohol, H ₂ O, CO, CO ₂ (Japanese Patent Application No. 62-305233)
(JP-A-1-145396).

[Problems to be solved by the invention]

A method of synthesizing diamond by a combustion flame method previously filed by the present applicant (Japanese Patent Application No. 63-71758 (JP-A-1-282193)).
)), The method of dissolving Co, Ni, Fe, etc. from the surface by acid treatment complicates the process, requires time and labor, and eliminates micro scratches on the substrate surface Therefore, the nucleation density of diamond decreases, and the flatness and adhesion strength of the film decrease.

In the method of heat-treating the surface of cemented carbide in an atmosphere containing alcohol, H ₂ O, CO, CO _2, etc. as shown in Japanese Patent Application No. 62-305233 (Japanese Patent Application Laid-Open No. 1-145396), it takes a long time for the surface treatment. Also, since the etching effect was not so strong, the adhesion strength was insufficient.

An object of the present invention is to solve the above problems and to efficiently synthesize a diamond film having a high adhesion strength.

[Means for solving the problem]

The present inventors have conducted intensive studies to achieve the above object, and as a result, prior to the combustion flame method disclosed in Japanese Patent Application No. 63-71758 (Japanese Patent Application Laid-Open No. 1-282193), the surface of the cemented carbide was subjected to an oxygen ratio. Discovered that a high-adhesion-strength diamond film can be efficiently synthesized by installing a cemented carbide in the incomplete combustion region, which is the diamond synthesis region, after being exposed to the complete combustion region or oxidation flame of the increased combustion flame. As a result, the present invention was completed.

That is, the gist of the present invention is to maintain the surface of a cemented carbide in a complete combustion region of a raw material compound for diamond precipitation or in an oxidizing atmosphere in the vicinity of the region, and then burn the compound for diamond precipitation to have an incomplete combustion region, Vapor-phase diamond coating method comprising: coating a diamond on a cemented carbide substrate by placing the cemented carbide substrate in the non-oxidizing atmosphere in or near the incomplete combustion region. It is in.

In this case, for example, in the case of an oxygen-acetylene flame, the ratio of the combustible gas to oxygen is C ₂ H ₂ / O ₂ ≦ 1 in a complete combustion flame or an oxidizing flame which is a pretreatment of the surface of the cemented carbide, and at this time, the temperature of the flame is The maximum is 3000 ° C or higher. When a cemented carbide substrate is held inside this flame, Co, Ni, and Fe on the surface gasify at high speed, and the surface becomes not only in a state where diamond is easily formed, but also the surface becomes rough, and the substrate and the diamond film are connected. Acts as an anchor. The time required for the above surface treatment depends on the gas flow rate, but is usually as fast as several minutes. After the surface treatment, if the oxygen ratio is reduced and the substrate is placed in the incomplete combustion region, the diamond film can be synthesized immediately after the surface treatment.

The present invention is disclosed in Japanese Patent Application No. 63-71758 (JP-A-1-282193).
The surface treatment can be performed with the same apparatus as the diamond synthesis apparatus disclosed in the 35th Applied Physics Alliance Lecture Meeting Preliminary Proceedings Vol. 2 29a-P-1, p. 434, '88. That is, during the synthesis of the diamond film, as shown in FIG. 2, it is kept in a region of oxygen deficiency called a reducing flame (inner flame) indicated by 8 in the combustion flame. This region is relatively low in the combustion flame due to lack of oxygen.

On the other hand, the area used for the surface treatment in the present invention is the external flame 3 shown in FIG. This region has the highest temperature in the combustion flame, and usually cannot synthesize diamond. After performing surface treatment in this area, as a method of transferring the substrate to the internal flame formed by diamond, it is possible to approach the burner substrate or conversely, approach the substrate to the burner, but in general, flammable It is easiest and most accurate to increase the oxygen to gas ratio and then to the proper oxygen ratio.

In other words, taking acetylene gas as an example, when acetylene gas and oxygen gas are burned, the area where diamond can be synthesized is formed as C ₂ H ₂ / O ₂ > 1, so that C ₂ H ₂ / O ₂ > 1 _{When 2} H ₂ / O ₂ ≦ 1, the substrate is exposed to an external flame to perform a surface treatment. After the surface treatment, if the oxygen ratio is reduced, the composition is continuously put into diamond synthesis. The time required for this surface treatment varies depending on the gas flow rate and the oxygen ratio, but according to experiments performed by the present inventors, acetylene 1.5 /
When the super-hard substrate is installed, the Co, Ni and Fe components on the surface are gasified after about 2 to 3 minutes, and the surface is roughened on the order of several μm and the anchor effect is high. Was. The roughness of the surface was not so great as to impair the dimensional accuracy of the cemented carbide substrate.

Although the mechanism by which Co, Ni, and Fe are removed in the complete combustion flame or the oxidation flame shown above is not clear, Co, Ni, and Fe are directly vaporized because of the higher temperature compared to the incomplete combustion flame, In addition, CO ₂ and H ₂ O contained more than incomplete combustion flame
Co, Ni, and Fe become Co (CO) ₄ , Ni (CO) ₄ , Fe (C
O) It is considered that a carbonyl compound such as ₅ is formed and vaporized.

〔Example〕

The present invention was carried out using the apparatus shown in FIG. 1 and using acetylene and oxygen as source gases. That is, the burner for acetylene is fixed at the tip at the bottom, and a water-cooled substrate support base at a distance of 20 mm from the burner nozzle, a 10 mm square, 3 mm thick
(Compound WC94% by weight, Co6% by weight). Acetylene 1.5 / min and oxygen 1.5 / min were passed through the burner to form a complete combustion flame consisting of a white heart and an external flame, and the cemented carbide substrate was held in the interior for 5 minutes. Thereafter, the oxygen ratio was reduced to 1.5 / min of acetylene and 1.2 / min of oxygen to form a white heart, a reducing flame (acetylene feather), and an outer flame, and the substrate was held in the reducing flame as shown in FIG. , Coated with diamonds.

After the synthesis, in order to examine the adhesiveness of the diamond film, a hemispherical tip having a diameter of 200 μm and a diamond film Rockwell indenter having an apex angle of 120 ° were used. As a result, the diamond film peeled off at about 35 kg.

[Comparative Example 1] A diamond film was synthesized using the same apparatus as in the example without performing surface treatment using a complete combustion flame. That is, as shown in FIG. 2, acetylene 1.5 / min, oxygen 1.2
The substrate was held for 30 minutes in the reducing flame under the condition of / min.

After the synthesis, the load until the diamond film was peeled off was examined in the same manner as in the example.

[Comparative Example 2] Hot filament method C having a diameter of 20 cm, a height of 15 cm, and a volume of 4.5
In the VD reactor, the same super-hard substrate as in the example was placed on the substrate support, and in a mixed gas of CO: 20 SCCM, CO ₂ : 20 SCCM, H ₂ : 5 SCCM, a filament temperature of 2000 ° C, a substrate temperature of 800 ° C, and a reaction pressure were used. Five
Surface treatment was performed at 0 Torr for 1 hour. As shown in FIG. 2, this surface-treated cemented carbide substrate was
The substrate was held for 30 minutes in a reducing flame under the conditions of 1.2 / min and oxygen 1.2 / min.

After the synthesis of the diamond, the load until the diamond film was peeled off was examined in the same manner as in the example, and it was about 25 kg.

〔The invention's effect〕

According to the present invention, the surface treatment of the cemented carbide and the coating of the diamond film can be performed in a series of operations, and a diamond coating film having a strong adhesive force can be synthesized.

[Brief description of the drawings]

FIG. 1 is a front view of an example of performing a surface treatment on a carbide substrate, and FIG. 2 is a front view of an example of synthesizing a diamond coating film.

Claims (1)

(57) [Claims] After maintaining the surface of a cemented carbide in a complete combustion region of a raw material compound for diamond precipitation or in an oxidizing atmosphere near the region, the compound for diamond deposition is burned to have an incomplete combustion region. A method for coating a diamond by a vapor phase method, wherein a diamond is coated on a cemented carbide substrate by placing the cemented carbide substrate in a non-oxidizing atmosphere in or near a complete combustion region.