JPH0570254A - Production of high hardness laminated body for tool - Google Patents

Abstract

PURPOSE:To produce a high hardness laminated body for a tool made of a joined body of a cubic BN sintered body and a hard sintered body by a single treatment at a high temp. under an ultrahigh pressure. CONSTITUTION:A low pressure phase BN molded body, a middle layer of a transition metal or a compd. thereof and a hard sintered body or a hard molded body are piled, filled into a reactor and treated at a high temp. under a static ultrahigh pressure to produce a joined body of a cubic BN sintered body and a hard sintered body. The low pressure phase BN molded body has <=100 deg. degree of selective orientation of c-axes to the principal plane. A high hardness laminated body for a tool made of the joined body can be produced by the single treatment as a body having high joining strength and free from cracks and chips.

Description

Detailed Description of the Invention

[0001]

The present invention relates to cubic boron nitride (c).
The present invention relates to a method for producing a high hardness laminate for a tool, which comprises a joined body of a BN) sintered body and a hard sintered body.

[0002]

2. Description of the Related Art Since cBN, which is a high-pressure phase of boron nitride, has hardness and thermal conductivity second to diamond and is chemically stable, it is used as a tool for machining ferrous metals. Is being promoted. In this case, since the cBN sintered body itself has insufficient strength and cannot be brazed to a metal or the like, it is usually used as a laminated body joined to a cemented carbide or the like.

Conventionally, the above-mentioned laminated body was synthesized by adding a catalyst to low-pressure phase boron nitride and treating it at an ultrahigh pressure and a high temperature to synthesize cBN powder.
Add binders such as metals such as Al and Co, carbides such as TiN, TiC, and Al ₂ O ₃ , nitrides, oxides, etc., and place bonding materials such as cemented carbide adjacently to them, and then again with ultrahigh pressure. Manufactured by high temperature treatment.

However, in this method, since the produced cBN sintered body contains the above-mentioned binder having a hardness lower than that of cBN, the hardness becomes small, and the original characteristics of cBN cannot be sufficiently brought out, and moreover, it is expensive. There is a problem that the production efficiency is poor because the high pressure and high temperature treatment is required twice.

In Japanese Patent Laid-Open No. 63-191505, a cBN is prepared by adding a magnesium nitride catalyst to a hexagonal boron nitride (hBN) compact as a low-pressure phase boron nitride and subjecting it to an ultrahigh pressure and high temperature treatment.
A method of joining a cBN sintered body and a hard sintered alloy substrate while manufacturing a sintered body has been proposed. However, this method has a problem that a laminate having excellent tool characteristics cannot be manufactured unless a special material such as TiN / Mo / TiN is used as the intermediate layer.

[0006]

The object of the present invention is to provide cB
The object is to efficiently manufacture a high-hardness laminate for tools, which is composed of a joined body of an N sintered body and a hard sintered body, by one ultrahigh pressure and high temperature treatment.

As a result of various investigations to achieve the above object, the present inventors have found that as a raw material low-pressure phase boron nitride compact, the degree of selective orientation of the c-axis with respect to the main plane of the compact is 100 degrees or less. The present invention was completed by discovering that a low pressure phase boron nitride compact can be used to efficiently produce a laminate composed of a joint of a cBN sintered body and a hard sintered body, which has a large joint strength and has no cracks or chips. It was made.

[0008]

That is, according to the present invention, a low-pressure phase boron nitride compact, an intermediate layer made of a transition metal or a compound thereof, and a hard sintered compact or a hard compact are stacked and filled in a reactor. Then, in producing a joined body of a cubic boron nitride sintered body and a hard sintered body by treating at static ultra-high pressure and high temperature, as the low-pressure phase boron nitride formed body, with respect to the main plane of the formed body. The method for producing a high hardness laminate for a tool is characterized by using a material having a degree of c-axis orientation of 100 degrees or less.

The present invention will be described in more detail below. The raw material low-pressure phase boron nitride compact used in the present invention should have a smaller value of the degree of selective orientation of the c-axis, and should be at least 100 degrees or less. The reason for this is that if the degree of orientation exceeds 100 degrees, cracks and chips are generated in the obtained laminate, or the bonding strength becomes insufficient, as shown in Examples described later.

In the present invention, "low-pressure phase boron nitride" means one having a laminated structure of hexagonal mesh plane formed by alternately bonding boron atoms and nitrogen atoms, and specifically, Is hBN, a turbostratic boron nitride (tB
N), rhombohedral boron nitride (rBN) alone or in a mixture.

In the present invention, the "degree of selective orientation of the c-axis" means to what extent the c-axis of the crystallites constituting the above low-pressure phase boron nitride is perpendicular to the main plane of the low-pressure phase boron nitride compact. It is a scale that indicates whether you are facing the direction. For the degree of selective orientation of the c-axis and its measuring method, see US Pat. No. 3,578,403.
No., `` Physica 139 & 104B (1986) P256-258.
, "X-Ray Diffraction Guide P79-82" (Rigaku Denki 198)
(Published November 30, 2012), the degree of selective orientation adopted in the present invention will be described in detail below.

To measure the degree of selective orientation of the c-axis, as shown in FIG. 1, a sample was cut out so that the axial direction of the cylinder was parallel to the main plane of the low-pressure phase boron nitride compact, and the sample was cut with X-axis. It is installed in a line diffractometer and is performed by the ω scan method. The "ω scan method" is an X-ray source that captures a specific diffraction line,
This is a method in which the diffraction counter is fixed and a cylindrical sample is scanned around the cylindrical axis to measure the diffraction intensity at each angle ω.

In the present invention, as the diffraction line, particularly, the low-pressure phase boron nitride has an interplanar spacing of around 3.33 angstroms,
That is, the diffraction line of (002) is used in the case of hBN and tBN, and the diffraction line of (003) is used in the case of rBN.

If the crystallites in the low-pressure phase boron nitride compact are oriented at random at all, the diffraction intensity will be constant irrespective of the angle ω, and the diffraction diagram of FIG. It becomes flat as shown in A). On the other hand, if each crystallite is oriented, the diffractogram will have an intensity distribution. In particular, if the c-axis is oriented in the direction perpendicular to the main plane of the low-pressure phase boron nitride compact, FIG.
As shown in, the analysis diagram is observed as a peak having a maximum intensity at a position where ω is 0 degree.

In the present invention, "degree of selective orientation of c-axis"
Is defined as the half-value width θ degree of the diffraction peak having the maximum intensity at the position where ω is 0 degree. That is, it is shown that the smaller the degree of θ is, the better the c-axis of the crystallite of low-pressure phase boron nitride is oriented in the direction perpendicular to the main plane of the low-pressure phase boron nitride compact.

The low-pressure phase boron nitride molded body used in the present invention, in which the degree of selective orientation of the c-axis of boron nitride is 100 degrees or less with respect to the principal plane, can be obtained, for example, as follows. (1) Pyrolytic boron nitride plate in which the degree of selective orientation of the low-pressure phase boron nitride on the c-axis is 100 degrees or less with respect to the principal plane: Pyrolytic boron nitride is generally synthesized by the CVD method and hB.
The pyrolytic boron nitride compact, which is composed of N, tBN, and rBN alone or in a mixture and is widely produced industrially, and which has a required degree of c-axis selective orientation used in the present invention is a CVD condition. Can also be obtained by adjusting or from the market. (2) Low-pressure phase boron nitride powder molded so that the degree of selective orientation of the c-axis is 100 degrees or less with respect to the main plane of the low-pressure phase boron nitride compact: For example, a normal scaly powder It can be obtained by filling the molding die little by little and applying a large number of pressures in the uniaxial direction each time.

In the present invention, the hard sintered body to be joined to the cBN sintered body has sufficient strength and hardness as a reinforcing material for the cBN sintered body and can be brazed to a shank such as a bite. I wish I had it. Specifically, WC, Mo
Cemented carbides such as C, TiC and TaC are listed, and WC is most suitable. Further, in the ultrahigh pressure and high temperature treatment carried out in the present invention, the hard powder is sufficiently sintered, so a hard molded product obtained by adding a suitable binder such as Co to the above hard powder and molding it into a plate shape. May be charged to the reactor.

The intermediate layer used in the present invention is cB
Any material can be used as long as it has good wettability with the N sintered body and the hard sintered body and can obtain high bonding strength. Specific examples of such a substance include transition metals of Group IV, V, and VI and compounds containing the same. Among them, Ti, Zr, Nb,
TiN, ZrN, NbN, TaN, ZrB ₂ and NbB ₂ are preferable. The thickness of the intermediate layer is preferably 0.001 to 1 mm. If it is less than 0.001 mm, sufficient bonding strength cannot be obtained. On the other hand, if it is thicker than 1 mm, stress concentrates on this part when used as a tool, causing peeling. Such an intermediate layer may be a sintered body of the above substance or a powder compact. Further, the intermediate layer is provided with C on the surface of one or both of the low-pressure phase boron nitride compact, the hard sintered compact and the hard compact.
It can also be formed by a thin film deposited by the VD method or the like.

The static ultrahigh pressure and high temperature treatment in the present invention is carried out, for example, as follows. The low-pressure phase boron nitride compact, the intermediate layer, and the hard sintered compact or the hard compact are stacked in an ultrahigh-pressure high-temperature reactor so that their main planes are parallel to each other, and packed into a belt-type high-temperature generator. Install. After that, first increase the pressure and then the temperature,
Hold for a period of time at pressure. The conditions are such that the low-pressure phase boron nitride compact is converted to cBN and a laminate having sufficient bonding strength can be obtained. Specifically, the pressure is 6.5 to 8.0 GPa and the temperature is 2000 to 2400 ° C. The holding time is 5 to 60 minutes. After the treatment, the temperature is first returned to room temperature and the pressure is returned to 1 atm, and the produced high hardness product phase for tool is taken out.

[0020]

The reason why the high hardness laminate for tools obtained by the present invention is free from cracks and chips and has a high bonding strength is considered as follows. True density of the low-pressure phase nitride boron and cBN, since each is 2.25 g / cm ³ and 3.48 g / cm ^3, when the low-pressure phase boron nitride is transferred to the cBN sintered body in a static ultrahigh pressure high temperature A large volume change occurs.
The low-pressure phase boron nitride is a material having a large anisotropy in the crystal structure, and when the structure changes to cBN, it hardly changes in the a-axis direction and contracts largely in the c-axis direction.
Such a volume change occurs.

As in the present invention, when a low-pressure phase boron nitride molded body which is selectively oriented in the c-axis direction is used, the direction parallel to the surface of the molded body is the a-axis direction, so that there is almost no volume change in this direction. In addition, since there is almost no deviation at the bonding interface with the intermediate layer, the bonding strength with the intermediate layer increases. That is, when the low-pressure phase boron nitride compact having a high density and selectively oriented is used, the volume change at the time of conversion to cBN becomes small, and the displacement at the bonding interface with the intermediate layer that occurs at that time becomes small, so that cracking occurs. Moreover, a laminated body having high bonding strength without chipping can be obtained.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1 As a raw material for a cBN sintered body (a low pressure phase boron nitride compact), a commercially available pyrolytic nitrogen boron (P-BN) plate having a degree of selective orientation of the c-axis of 5 degrees, a diameter of 17 mm, A disc having a thickness of 1 mm was cut out. As an intermediate layer, a commercially available NBN powder is molded to have a diameter
A disk having a thickness of 17 mm and a thickness of 0.2 mm was produced. As a raw material for a hard sintered body (hard compact), 1% by weight of Co powder was added to WC powder to form a disk having a diameter of 17 mm and a thickness of 0.2 mm.

The above P-BN disc, intermediate layer disc and hard molded disc were placed in a cylindrical graphite ultra high pressure high temperature reactor also serving as a heater so that the principal planes of the discs were parallel to each other. They were stacked and filled, and installed in a belt type high temperature generator.

Then, the pressure was first raised to raise the temperature, and the ultrahigh pressure high temperature treatment was carried out under the conditions of pressure 7.5 GPa, temperature 2300 ° C. and holding time 30 minutes, and then temperature first and then pressure respectively room temperature and 1 atm. The resulting laminate was taken out, and the occurrence of cracks and chips was examined by an optical microscope. Further, in order to examine the bonding state, a tool insert (shape: JIS model number TNGN332) was produced and a cutting test (cutting condition: JIS B4011) was performed to check the presence or absence of peeling on the bonding surface. The results are shown in Table 1. In Table 1, "degree of orientation" means the degree of selective orientation of the c-axis.

[0026]

[Table 1]

Examples 2 to 5 P- with c-axis selective orientation degrees of 33 degrees, 62 degrees, 91 degrees and 100 degrees
The same procedure as in Example 1 was carried out except that a BN disc was used.

Examples 6 to 7 Except that the ultrahigh pressure and high temperature treatment conditions are those shown in Table 1,
The same procedure as in Example 5 was performed.

Examples 8 to 10 The same procedure as in Example 5 was carried out except that a commercially available Nb plate, Ti plate or Zr plate was used as the intermediate layer disc.

Examples 11 to 15 The same as Example 5 except that a commercially available TiN powder, ZrN powder, TaN powder, NbB ₂ powder or ZrB ₂ powder was used as the intermediate layer disk. went.

Example 16 As a low-pressure phase boron nitride compact, a commercially available hBN powder (GP grade manufactured by Denki Kagaku Kogyo Co., Ltd.) was charged little by little into a molding die, and the pressure was applied three times in each uniaxial direction ( 100 M
Pa) was added, and a disk having a degree of selective orientation on the c-axis of 100 degrees was used, and the same procedure as in Example 1 was performed.

Comparative Example 1 The procedure of Example 1 was repeated, except that a P-BN disk having a c-axis selective orientation of 119 degrees was used. As a result, no abnormal appearance was observed in the obtained laminated body, but the cBN sintered body was peeled off from the joint surface of the intermediate layer during the cutting test.

Comparative Example 2 The procedure of Example 1 was repeated except that a P-BN disk having a degree of selective orientation of c-axis of 135 degrees was used. As a result, several cracks were found in the cBN sintered body portion of the obtained laminate.

[0034]

EFFECTS OF THE INVENTION According to the present invention, a high-hardness laminate for a tool, which is a joined body of a cBN sintered body and a hard sintered body, can be produced by a single ultra-high pressure and high temperature treatment, and a high joint can be obtained. It is possible to obtain a product that has strength and is free of cracks and chips.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a method for measuring the degree of selective orientation of a c-axis of a low-pressure phase boron nitride compact.

FIG. 2 is a diffraction diagram of a low-pressure phase boron nitride compact by the ω scan method.

Front page continuation (72) Inventor Hiroaki Tanji 3-5-1, Asahimachi, Machida-shi, Tokyo Denka Kagaku Kogyo Co., Ltd.

Claims (1)

[Claims] 1. A low pressure phase boron nitride compact, an intermediate layer made of a transition metal or a compound thereof, and a hard sintered compact or a hard compact are stacked and filled in a reactor and treated at a static ultrahigh pressure and high temperature. In manufacturing a joined body of a cubic boron nitride sintered body and a hard sintered body, as the above-mentioned low-pressure phase boron nitride compact, the degree of selective orientation of the c axis with respect to the main plane of the compact is 100 degrees or less. A method for manufacturing a high hardness laminate for tools, characterized in that