JPH0542509B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical field of the present invention] The present invention relates to cubic boron nitride, which has excellent wear resistance and is suitable for use as a cutting tool.
Nitride is abbreviated as CBN. ) The present invention relates to a method for manufacturing a hard body coated with a surface layer. [Conventional Cutting Tools] Currently, tools are used in which the surface of a sintered hard substrate containing at least one type of carbide along with a bonding metal is coated with TiC, TiN, Al ₂ O ₃ or the like. This current coated tool has excellent both toughness and wear resistance by attaching the coating layer, which has higher hardness and excellent wear resistance, to a base having high toughness. However, as the cutting speed increases, the temperature of the cutting edge increases, but the coating layer can (1) reduce the reaction with the work material due to its chemical stability, and (2) lower the temperature of the cutting edge due to its high thermal conductivity. Can not. As a result, it has been impossible to extend the life of the cutting tool made of the coating layer. The present inventors have conducted repeated research to develop a tool material that exhibits excellent performance in high-speed cutting by considering the types of coating layers for (1) and (2) above, and have developed the present invention. This is the completed version. [Object of the present invention] That is, the object of the present invention is to provide a method for manufacturing a coated hard body in which the temperature of the cutting edge does not increase significantly even when cutting at high speed, and there is less wear due to reaction with the work material. is to provide. [Structure of the present invention] And, as a means to achieve the above object, the present invention selects CBN as the coating layer,
In addition, as a means of forming this coating layer on the surface of a hard substrate or on the surface of a hard substrate on which an intermediate coating layer has been previously applied, it is possible to first coat amorphous boron nitride and then convert it into CBN. be. That is, the present invention provides a sintered hard substrate containing at least one carbide together with a binder metal or one of the carbides, nitrides, oxides and borides of metals from groups 4a and 5a of the periodic table. The surface of the above-mentioned hard substrate coated with a coating of 0.5 to 20 μm in thickness is coated with amorphous boron nitride by a vapor phase method, and this coated hard body is brought into contact with Al and/or an Al compound. A method for manufacturing a cubic boron nitride-coated hard body, characterized in that all amorphous boron nitride is converted to cubic boron nitride by maintaining the cubic boron nitride in a thermodynamically stable region. It is. Describing the present invention in detail below, the present inventors discovered that CBN is a material with the second highest hardness next to diamond, has excellent thermal conductivity, and has low reactivity with iron group metals at high temperatures. Knowing that CBN is directly applied to a sintered hard substrate containing at least one carbide along with a bonding metal or a carbide of a group 4a or 5a metal of the periodic table,
0.5 through one or more intermediate layers of one or more coatings of nitrides, oxides, borides.
It has been found that a hard body coated with a thickness of ~20μ has unprecedented performance. Incidentally, although research into vapor phase synthesis of CBN has been widely conducted, a reliable method has not yet been found. However, it is relatively easy to form a uniform film of amorphous boron nitride using methods such as plasma CVD, ion plating, and ion beam evaporation. The present inventors focused on this point, and first coated with an amorphous boron nitride thin film (of course, it may also partially contain CBN), and then covered it with Al and/or Al. By exposing it to high pressure and high temperature, which is the stable region of CBN, while in contact with a compound, it is converted into a CBN film. According to this method, a strong coating layer made only of CBN can be easily obtained, and the adhesion strength to the hard substrate is also high. As mentioned above, CBN has excellent properties such as hardness, thermal conductivity, and chemical stability at high temperatures, so a hard object coated with CBN will have a high cutting edge temperature even when cutting at high speed. It does not rise and there is little wear due to reaction with the work material. In the present invention, a sintered hard substrate containing at least one type of carbide along with a binder metal is used as the substrate, for example, WC-based, (Mo, W)C-based cemented carbide, TiC. The material can be arbitrarily selected from known materials such as cermet, which is the main material. In the present invention, the thickness of the CBN coating layer on the surface is
The range is 0.5 to 20μ, because if it is less than 0.5μ, properties such as hardness, thermal conductivity, and chemical stability for the work material will not be sufficient, and there will be large variations between products. If it exceeds 20μ, strain will easily occur within the coating layer and the strength of the layer itself will decrease.
This is because micro-defects occur in the coating layer during cutting, resulting in a decrease in tool performance. Furthermore, in the present invention, when coating a WC-based cemented carbide with a CBN layer, if amorphous boron nitride is directly coated, only weak adhesion will be obtained;
As a base, one or more intermediate layers of one or more of carbides, nitrides, oxides, and borides of metals from groups 4a and 5a of the periodic table are coated in advance, and amorphous amorphous A coating of boron nitride may be applied. However, if the hard substrate contains TiC or TiN, for example, it is possible to directly coat it with amorphous boron nitride with good adhesion. The thickness of this intermediate layer can be varied within certain limits while retaining its advantageous properties. In order to obtain an intermediate layer suitable according to the invention, the thickness is at least 0.5μ. Best results were found between 1 and 10μ. This middle layer is the well-known PVD,
Coating is performed using methods such as CVD. In coating the CBN layer, according to the present invention, for example, a hard substrate is placed in a gas flow containing BCl ₄ and NH ₃ and amorphous boron nitride is deposited by plasma CVD at a temperature of 600 to 1000°C and a pressure of 0.1 to 10 mmHg. The coated hard substrate and Al and/or Al compound are filled in a metal container, such as Mo or W, so that they are in contact with each other, and the container is placed in a high temperature and high pressure generating chamber. Shown in Figure 1
Exposure for several minutes or more in the thermodynamically stable region of CBN, that is, region A. (In Fig. 1, 1 is the cubic-cubic boron nitride equilibrium line, A is the high-pressure phase boron nitride stability region, and B is the hexagonal boron nitride stability region.) During this time, Amorphous boron nitride is converted into CBN by the catalytic action of Al and/or Al compounds, and a CBN layer is formed on the surface of the hard substrate. After the holding is completed, only heating is stopped while the pressure is held, and after the high temperature and high pressure generation chamber is cooled to around room temperature, the holding pressure is gradually released and the pressure is returned to normal pressure. A CBN-coated hard body is obtained from the recovered sample by treating the metal reaction vessel with acid. For coating a hard substrate with amorphous boron nitride, in addition to the plasma CVD method described above, methods such as ion beam evaporation or ion plating can also be applied in the present invention. EXAMPLES The present invention will be described in more detail below with reference to Examples. Example 1 WC-based cemented carbide (9.5% Co, 12% by weight)
Using a substrate of TiC, 6% TaC and residual WC)
A cutting chip of SNG432 was created. This in advance
The one coated with 1μ of TiC by CVD method and the one without coating were treated with 15% and 40% by weight of BCl ₄ , NH ₃ , and H ₂ respectively.
Temperature 800℃, placed in a mixed gas stream containing 45%
Amorphous boron nitride coating was performed by plasma CVD using a high frequency of 13.56 MHz and 200 W under a pressure of 0.5 mmHg. The treatment time was 2 hours. As a result of this treatment, amorphous boron nitride with a thickness of approximately 4 μm was obtained. These were filled into a Mo container so that the coating layer and the Al powder were in contact with each other, and the container was held at a temperature of 1200°C and a pressure of 40 kb for 10 minutes. As a result, all amorphous boron nitride was converted to CBN. A cutting test was conducted on these chips under the conditions shown in Table 1. For comparison, the above substrate
Chips directly coated with Al ₂ O ₃ using the CVD method were used.
The results are shown in Table 2.

【table】

【table】 Example 2 Three types shown in Table 3 were used as hard substrates.

[Table] Using the hard substrates shown in Table 3, SNG432 chips were prepared and coated using the plasma CVD method under the same conditions as in Example 1. The treatment time was 3 hours.
As a result of this treatment, amorphous boron nitride with a thickness of 5.4 μm was obtained. These were filled into a Mo container so that the coating layer and AlN powder were in contact with each other, and the container was heated to a temperature of 125°C.
It was held at 45kb for 10 minutes. As a result, all of the amorphous boron nitride had been converted to CBN.A cutting test was conducted on these chips under the same conditions as Condition 1 of Example 1. For comparison, chips No. K and G shown in Table 3 were used which were directly coated with Al ₂ O ₃ by the CVD method. (Comparative materials -1 and -2, respectively) The results are shown in Table 4.

[Table] Example 3 Using the hard substrate No. A of Example 2, a CBN-coated chip (SNG 432) was produced in the same manner as in Example 1. Table 5 shows the thickness and processing time of these CBN layers. Table 5 shows the results of a cutting test conducted on these under conditions 2 and 3 of Example 1. As a comparative material, a chip in which substrate A was coated with 5μ of Al ₂ O ₃ was used.

[Effects of the present invention]

As detailed above, the present invention has excellent performance when used as a cutting tool, that is, the temperature of the cutting edge does not increase significantly even during high-speed cutting, and there is little wear due to reaction with the work material. It is something that produces the effect that something is obtained.

[Brief explanation of the drawing]

FIG. 1 shows the thermodynamically stable region on the pressure-temperature phase diagram of high-pressure phase type boron nitride. 1: cubic-hexagonal boron nitride equilibrium line, A: high-pressure phase boron nitride stability region, B: hexagonal boron nitride stability region.

Claims (1)

[Claims] 1. A sintered hard substrate containing at least one carbide together with the binder metal or a pre-coated with one or more carbides, nitrides, oxides and borides of metals from groups 4a and 5a of the periodic table. The surface of the above-mentioned hard substrate is coated with amorphous boron nitride with a thickness of 0.5 to 20μ by a vapor phase method, and the coated hard body is subjected to cubic nitriding in contact with Al and/or Al compounds. A method for producing a cubic boron nitride-coated hard body, which comprises converting all amorphous boron nitride into cubic boron nitride by maintaining the boron in a thermodynamically stable region.