JP2891559B2 - Manufacturing method of high hardness laminate for tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to cubic boron nitride (c)
BN) The present invention relates to a method for manufacturing a high-hardness laminate for a tool comprising a joined body of a sintered body and a hard sintered body.

[0002]

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

Conventionally, the above-mentioned laminate is synthesized by adding a catalyst to low-pressure phase boron nitride and subjecting it to ultra-high pressure and high temperature processing to synthesize cBN powder,
Metals such as Al and Co, binders such as carbides, nitrides and oxides such as TiN, TiC and Al ₂ O ₃ are added, and a cementing material such as cemented carbide is placed adjacent to them, and then the Manufactured by high-temperature treatment.

However, in this method, the cBN sintered body to be formed contains the above-mentioned binder having a lower hardness than cBN, so that the hardness is reduced, so that the inherent characteristics of cBN cannot be sufficiently brought out, and furthermore, an expensive superconducting material is required. There is a problem that the production efficiency is low because the high pressure and high temperature treatment is required twice.

Japanese Patent Application Laid-Open No. 63-191505 discloses that a hexagonal boron nitride (hBN) compact as a low-pressure phase boron nitride is added with a magnesium nitride catalyst and subjected to ultra-high pressure and high temperature treatment to obtain cBN.
A method of joining a cBN sintered body and a hard sintered alloy substrate while producing 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]

An object of the present invention is to provide cB
It is an object of the present invention to efficiently manufacture a high-hardness laminate for a tool comprising an N sintered body and a joined body of a hard sintered body by one ultra-high pressure and high temperature treatment.

The inventors of the present invention have conducted various studies to achieve the above object. As a result, as a raw material of a low-pressure phase boron nitride compact, the degree of c-axis selective orientation with respect to the main plane of the compact was 100 degrees or less. Using a certain low-pressure phase boron nitride compact, the present inventors have found that a laminate comprising a joined body of a cBN sintered body and a hard sintered body having a large joint strength and without cracks or cracks can be efficiently produced, and completed the present invention. It was made.

[0008]

That is, the present invention relates to 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 hard compact which 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 processing at a static ultra-high pressure and high temperature, the above-mentioned low-pressure phase boron nitride molded body is formed with respect to a main plane of the molded body. A method for producing a high-hardness laminate for tools, characterized in that a material having a degree of c-axis selective orientation of 100 degrees or less is used.

Hereinafter, the present invention will be described in more detail. 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 have a value of 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 is not sufficient, as will be shown in Examples described later.

In the present invention, "low-pressure phase boron nitride" means a layered structure of hexagonal mesh planes formed by alternately bonding boron atoms and nitrogen atoms. Is hBN, turbostratic boron nitride (tB
N), a simple substance or a mixture of rhombohedral boron nitride (rBN).

In the present invention, the term “degree of c-axis selective orientation” means that the degree of the c-axis of the crystallite constituting the 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. Regarding the degree of c-axis orientation and its measurement method, see US Pat. No. 3,578,403.
No., `` Physica139 & 104B (1986) P256-258
”,“ Guide to X-ray diffraction P79-82 ”(Rigaku Denki Co., Ltd. 198)
(Published on November 30, 2012), the preferred orientation degree employed in the present invention will be described in detail below.

As shown in FIG. 1, the measurement of the degree of selective orientation of the c-axis is performed by cutting a sample such that the axial direction of the cylinder is parallel to the main plane of the low-pressure phase boron nitride compact, and the sample is cut out by X. It is installed in a line diffractometer and performed by the ω scan method. The “ω scan method” is an X-ray source that captures specific diffraction lines,
In this method, a diffraction counter tube is fixed, a cylindrical sample is scanned around a cylindrical axis, and the diffraction intensity at each angle ω is measured.

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

If the crystallites are oriented at random in the low-pressure phase boron nitride compact, the diffraction intensity is constant without depending on the angle ω. It becomes flat as shown by 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 a direction perpendicular to the main plane of the low-pressure phase boron nitride molded product, it can be seen from FIG.
As shown in the figure, the analysis diagram is observed as a peak having the maximum intensity at the position where ω becomes 0 degrees.

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

The low-pressure phase boron nitride molded article in which the degree of selective orientation of the c-axis of boron nitride used in the present invention is 100 degrees or less with respect to the main plane can be obtained, for example, as follows. (1) Pyrolytic boron nitride plate in which the degree of c-axis selective orientation of low-pressure phase boron nitride is 100 degrees or less with respect to the main plane: Pyrolytic boron nitride is generally synthesized by a CVD method and is hB.
The thermally decomposed boron nitride molded body made of a single substance or a mixture of N, tBN, and rBN, which is industrially widely produced, and has a required degree of c-axis selective orientation used in the present invention, is subjected to CVD conditions. Can be obtained either by adjusting or on the market. (2) A 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 scale-like powder is used. It can be obtained by applying a pressure many times in one axial direction each time while filling the molding die little by little.

In the present invention, the hard sintered body 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 cutting tool. I just need. Specifically, WC, Mo
Cemented carbides such as C, TiC, and TaC are mentioned, and WC is most preferable. Further, in the ultra-high pressure and high temperature treatment performed in the present invention, since the hard powder is sufficiently sintered, a hard compact obtained by adding a suitable binder such as Co to the above hard powder and forming the plate 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 substances include transition metals of Groups IV, V and VI and compounds containing the same. Among them, Ti, Zr, Nb,
TiN, ZrN, NbN, TaN, ZrB ₂ and NbB ₂ are preferred. The thickness of the intermediate layer is preferably from 0.001 to 1 mm. If the thickness is less than 0.001 mm, sufficient bonding strength cannot be obtained. On the other hand, if the thickness is more than 1 mm, when used as a tool, stress concentrates on this portion and causes peeling. Such an intermediate layer may be a sintered body of the above substance or a powder compact. In addition, the intermediate layer is formed on one or both surfaces of the low-pressure phase boron nitride compact, the hard sintered compact, and the hard compact by applying C
It can also be formed by a thin film deposited by a VD method or the like.

The static ultra-high pressure and high temperature treatment in the present invention is performed, for example, as follows. The low-pressure phase boron nitride compact, the intermediate layer and the hard sintered compact or hard compact are stacked and filled in an ultra-high pressure high-temperature reactor so that their main planes are parallel to each other. Install. After that, the pressure is first increased, and then the temperature is increased.
Hold at pressure for a period of time. The conditions are such that the low-pressure phase boron nitride compact is converted into cBN and a laminate having sufficient bonding strength is obtained. Specifically, the pressure is 6.5 to 8.0 GPa, the temperature is 2000 to 2400 ° C. And a retention time of 5 to 60 minutes. After the treatment, the temperature is firstly restored, then the pressure is returned to room temperature and 1 atm, respectively, and the resulting high-hardness product for a tool is taken out.

[0020]

The reason why the high-hardness laminate for a tool obtained according to the present invention has no cracks and chips, and has high bonding strength is 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 Large volume changes occur.
Low-pressure phase boron nitride is a material having a large anisotropy in the crystal structure. When the structure changes to cBN, it hardly changes in the a-axis direction and shrinks greatly in the c-axis direction.
Such a volume change occurs.

When a low-pressure phase boron nitride compact having a preferred orientation in the c-axis direction is used as in the present invention, the direction parallel to the surface of the compact is the a-axis direction, and almost no volume change occurs in this direction. In addition, since almost no displacement occurs at the bonding interface with the intermediate layer, the bonding strength with the intermediate layer increases. That is, when a low-pressure phase boron nitride compact having a high density and selective orientation is used, a change in volume at the time of conversion to cBN is small, and a shift at a bonding interface with an intermediate layer at that time is small, so that a crack is generated. A laminate having high bonding strength without chipping is obtained.

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

Example 1 As a raw material (a low-pressure phase boron nitride compact) of a cBN sintered body, a commercially available pyrolytic nitrogen-boron (P-BN) plate having a c-axis selective orientation of 5 degrees was used. A disk having a thickness of 1 mm was cut out. As an intermediate layer, commercially available NBN powder is molded and
A disk having a thickness of 17 mm and a thickness of 0.2 mm was produced. As a raw material of a hard sintered body (hard molded body), 1 wt% 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-mentioned P-BN disk, intermediate layer disk and hard compact disk are placed in a cylindrical graphite ultra-high pressure high temperature reactor also serving as a heater so that the principal planes of the disks are parallel to each other. Stacked and filled, and placed in a belt-type high-temperature generator.

Then, the pressure is first increased, then the temperature is increased. After the ultra-high pressure and high temperature treatment is performed under the conditions of a pressure of 7.5 GPa, a temperature of 2300 ° C., and a holding time of 30 minutes, the temperature is first increased, and then the pressure is increased to room temperature and 1 atm , And the obtained laminate was taken out and examined for occurrence of cracks and chips by an optical microscope. In addition, in order to examine the joining state, a tool insert (shape: JIS model number TNGN332) was prepared, and a cutting test (cutting condition: JIS B4011) was performed to check for the presence or absence of peeling at the joining surface. Table 1 shows the results. In Table 1, "degree of orientation" means the degree of selective orientation of the c-axis.

[0026]

[Table 1]

Examples 2 to 5 P-type crystals having a c-axis orientation of 33 degrees, 62 degrees, 91 degrees and 100 degrees
Except that a BN disk was used, the procedure was the same as in Example 1.

Examples 6 and 7 Except that the ultrahigh-pressure and high-temperature treatment conditions were the conditions shown in Table 1,
Performed in the same manner as in Example 5.

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

Examples 11 to 15 In the same manner as in Example 5, except that a commercially available TiN powder, ZrN powder, TaN powder, NbB ₂ powder or ZrB ₂ powder was used as an 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 a pressure (three times) in one axial direction was applied each time. 100 M
Pa) was performed in the same manner as in Example 1 except that a disk having a c-axis selective orientation of 100 ° was used.

Comparative Example 1 The same procedure as in Example 1 was carried out except that a P-BN disk having a c-axis orientation degree of 119 ° was used. As a result, no abnormality in appearance was observed in the obtained laminate, but the cBN sintered body was separated from the joint surface of the intermediate layer during the cutting test.

Comparative Example 2 The same procedure as in Example 1 was carried out except that a P-BN disk having a c-axis selective orientation of 135 ° was used. As a result, several cracks were formed in the cBN sintered body portion of the obtained laminate.

[0034]

According to the present invention, a high-hardness laminate for a tool comprising a bonded body of a cBN sintered body and a hard sintered body can be manufactured by one high-pressure and high-temperature treatment, and a high bonding strength can be obtained. A product having strength and without cracks and chips can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a method for measuring the degree of selective orientation of the 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 an ω-scan method.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroaki Tanji 3-5-1 Asahicho, Machida-shi, Tokyo Denki Kagaku Kogyo Co., Ltd. (56) References JP-A-63-191632 (JP, A) JP-A-2-199072 (JP, A) JP-A-63-202444 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 37/00 C04B 35/626

Claims (1)

(57) [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 ultra-high pressure and high temperature. In producing a joined body of a cubic boron nitride sintered body and a hard sintered body, the low pressure phase boron nitride molded body has a c-axis selective orientation degree of 100 degrees or less with respect to a main plane of the molded body. A method for producing a high-hardness laminate for tools, characterized by using: