JP2000044347A - Cbn sintered compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cBN sintered compact excellent in fracture resistance by optimizing the crater resistance and strength. SOLUTION: This cBN sintered compact is obtained by sintering cBN particles with a bonding phase which is continuous when two-dimensionally viewed. The bonding phase contains one or more kinds selected from the group consisting of carbides, nitrides, carbonitrides and borides of groups 4a, 5a and 6a transition metals of the periodic table, nitrides, borides and oxides of Al, carbides, nitrides, carbonitrides and borides of at least one kind of Fe, Co and Ni and mutual solid solutions thereof. The average value of the thickness of the bonding phase is <=1.0 μm and the standard deviation thereof is <=0.7. The content of the cBN is 45-70% expressed in terms of vol.%. The average particle size of the cBN particles is >=0.01 and <2 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to cubic boron nitride (c)
BN) Sintered body. In particular, it relates to a cBN sintered body for a cutting tool having improved wear resistance and fracture resistance.

[0002]

2. Description of the Related Art cBN is a high-hardness material next to diamond, and cBN-based sintered bodies are used for various cutting tools, wear-resistant parts, impact-resistant parts and the like.

As this kind of sintered body, for example, Japanese Patent Publication No. 62-2
No. 5,630, JP-B-62-25631, and JP-A-5-186272.

[0004]

However, the above techniques are not always sufficient in strength. For example, when the above-described sintered body is used for a cutting tool, in applications where a strong impact is applied to the cutting edge, the cutting edge is likely to be broken by the impact, and as a result, there is a problem that the tool life is not stable.

Accordingly, a main object of the present invention is to provide a cBN sintered body having excellent fracture resistance by improving the strength.

[0006]

The sintered body of the present invention is a sintered body obtained by sintering cBN particles with a binder phase. This bonded phase has a continuous structure when viewed two-dimensionally. Further, this bonded phase is composed of carbides, nitrides, carbonitrides, borides, Al nitrides, borides, oxides, and transition metals of transition metals of Groups 4a, 5a, and 6a of the periodic table.
e, at least one selected from the group consisting of carbides, nitrides, carbonitrides, borides, and mutual solid solutions of Ni, Co, and Ni. Further, the average value of the binder phase thickness is 1.0 μm or less, and the standard deviation thereof is 0.7 or less. Here, the binder phase thickness means a distance between cBN particles on an arbitrary straight line in the sintered body.
On the other hand, the content of cBN is 45 to 70% by volume.
The average particle size of the cBN particles is 0.01 to 2.0 μm.
m. This average particle size means that the cumulative volume% is 50%
Means the particle size.

A conventional cBN sintered body (cBN particles having an average particle size of 0.01 to 2 μm) has a standard deviation of the binder phase thickness of 0.7.
Is over. That is, there is a portion where the thickness of the binder phase varies greatly and the binder phase alone occupies a large volume. This portion is a portion (defect) of low strength in the sintered body. When an impact is applied to the sintered body, stress is likely to concentrate at this portion and the strength is weak, so that fracture is likely to occur from this point, and the tool has insufficient fracture resistance.

In applications where an impact is applied to the cutting edge, as described above, the stress concentrates on the above-mentioned defect portion due to the impact, and the strength of this portion is weak. It is thought to be missing.

Therefore, in the sintered body of the present invention, the variation in the thickness of the binder phase is made smaller than that of the conventional sintered body, thereby reducing the portion that becomes a defect and improving the fracture resistance. When the average thickness of the binder phase and its standard deviation exceed the above specified values,
The portion occupying a large volume by the binder phase alone increases, and the effect of improving the fracture resistance is small. The lower limit of the average thickness of the binder phase is preferably about 0.2 μm in order to exhibit the function as the binder phase. Further, when the cBN particles are finer than the above-mentioned specification, the heat resistance of the particles is inferior and wear tends to develop,
If the grain size is larger than the specified value, the cBN particle itself is cleaved by the impact, the cutting edge is broken, and the fracture resistance of the tool is insufficient.
The suitable size of the BN particles is 0.01 to 2 μm.

In order to obtain the sintered material of the present invention, cBN is coated with a binder phase material or the raw materials are mixed by a special method. Before sintering, the coating of the binder phase material is induced by the compression shear force, friction force, and impact force during chemical vapor deposition (CVD), physical vapor deposition (PVD), electroless plating, or mechanical mixing. And a method utilizing a mechanochemical reaction. For a special mixing method, an ultrasonic mixing method or a ball mill method using a dispersing material is optimal.

In the step of sintering the sintered material of the present invention, a plasma sintering apparatus, a hot press apparatus, an ultra-high pressure sintering apparatus, or the like can be used.

[0012]

Embodiments of the present invention will be described below.

Example 1 76% by weight of Ti nitride
18% by weight Al, 3% by weight Co and 3% by weight N
i was mixed, and the compound that had been heat-treated in vacuum at 1200 ° C. for 30 minutes was pulverized to prepare a binder phase powder. This binder phase powder is made of TiN, Ti ₂ by XRD (X-ray diffraction).
Peaks such as AlN and TiAl ₃ were observed. This binder phase powder and cBN powder having an average particle size of 1 μm were mixed by the method described in Table 1 so that the volume content of cBN was 60% by volume. The detailed conditions of each mixing method are as follows. Here, No. In 2, the cBN was coated with TiN by RF sputtering. The average thickness of the coating is 40 nm. In addition, No. No dispersant was used in the mixing of the two.

Ultrasonic mixing method: cBN and a binder powder were put into acetone and mixed with ultrasonic vibration of 23.5 kHz. BM method → Pot a ball having a diameter of 10 mm, cBN powder and binder powder into a pot, and set at 235 rpm, 34
Wet mixing was performed in ethyl alcohol for 0 minutes. Dispersant → 1.5% by weight of polyvinyl alcohol was added as a dispersant.

[0015]

[Table 1]

Then, the mixed powder was prepared at 5 GPa, 1300
Sintered under ultra high pressure of ℃ and high temperature. XR of the obtained sintered body
D is cBN, TiN, TiB ₂ , AlB ₂ , Al
N, Al ₂ O ₃ and WC were observed.

The structures of these sintered bodies were examined with a metallographic microscope.
When photographed at × 00, cBN particles appearing black and a bonded phase appearing white were observed. An arbitrary straight line was drawn on this photograph, and the thickness of the binder phase was measured. This measurement is performed by measuring the thickness of the binder phase in the arbitrary linear shape, that is, the distance between cBN particles at 20 points or more, and calculating the average of the measured values. Then, the average value and the standard deviation shown in Table 1 were obtained from each measured value.

Further, these sintered bodies were processed into cutting tools, and cutting tests were performed under the following conditions to measure the tool life leading to chipping. The results shown in Table 1 were obtained.

Cutting test conditions: Work material: SCM415, HRC58-62, φ100 mm
× L300 mm, with six V-shaped grooves in the longitudinal direction. Tool shape: SNG432 NL-25 * 0.15-0.
2 Holder: FN11R Cutting conditions: V = 100 m / min, d = 0.2 mm, f = 0.
13mm / rev, dry

As is apparent from the results, when the average value of the binder phase thickness is 1.0 μm or less and the standard deviation is 0.7 or less, the tool life is doubled. Further, in order to produce a sintered body having such a binder phase thickness, it can be seen that when mixing the binder phase material, an ultrasonic mixing method or a ball mill method using a dispersing material is preferable.

Example 2 73% by weight of Ti nitride
19 wt% Al, 4 wt% Co and 4 wt% N
i was mixed and heat-treated in vacuum at 1240 ° C. for 32 minutes to pulverize the compound to prepare a binder phase powder. T in XRD
Peaks such as iN, Ti ₂ AlN, and TiAl ₃ were observed.
This binder phase powder and cBN powder having an average particle size of 0.5 μm were
The mixture was mixed by an ultrasonic mixing method and a ball mill (BM) method without using a dispersing agent so that the volume content of cBN was 65%. The detailed conditions of each mixing method are as follows.

Ultrasonic mixing method: cB in ethyl alcohol
N and the powder of the binder were charged and mixed by applying ultrasonic vibration of 22.3 kHz. BM method → Pot a ball with a diameter of 10 mm, cBN powder and binder powder into a pot, and add 215 rp
m, for 450 minutes, wet mixing in acetone.

Then, this powder was added to 4.85 GPa, 131
The sintering was performed under an ultra-high pressure of 0 ° C. and a high temperature. X of the obtained sintered body
RD is cBN, TiN, TiB ₂ , AlB ₂ , Al
N, Al ₂ O ₃ and WC were observed. The structures of these sintered bodies were observed by the following method. In each of the following methods, the method for measuring the thickness of the binder phase is the same as in Example 1. 1) When taken with a metallographic microscope at 1500x magnification,
CBN particles appearing black and a bonded phase appearing white were observed. An arbitrary straight line was drawn on this photograph, and the thickness of the binder phase was measured.

2) SEM (Scanning Electron Microscope)
When photographed at 3,000 times at, cBN particles and a binding phase were observed. An arbitrary straight line was drawn on this photograph, and the thickness of the binder phase was measured.

3) TEM (Transmission Electron Microsc)
When the photograph was taken at 10000 magnification in (ope), cBN particles and a binding phase were observed. An arbitrary straight line was drawn on this photograph, and the thickness of the binder phase was measured.

4) Auger (Auger Electron Spectrosc)
opy) at 10,000 ×, cBN particles and a bonded phase were observed. Draw any straight line in this photo,
The binder phase thickness was measured.

5) When photographed with a metallographic microscope at 1500 ×, cBN particles appearing black and a bonded phase appearing white were observed. This was image-analyzed, binarized so that the area ratio of the particles that looked black as the cBN particles was equal to the volume content of cBN, the portion corresponding to the binder phase was specified, and the binder phase thickness was measured.

6) When photographed with a metallographic microscope at a magnification of 1000, cBN particles appearing black and a bonded phase appearing white were observed. This was image-analyzed, and the luminance on an arbitrary straight line was measured. As a result, periodicity was observed. When a certain luminance is divided into a dark part (a part corresponding to the cBN particle) and a light part (a part corresponding to the binder phase), the luminance is determined so that the ratio becomes equal to the volume content of the cBN, and the length of the bright part is combined. The phase thickness was used.

The average value and the standard deviation of the binder phase thickness measured in this way were calculated, and the results are as shown in Table 2.

[0030]

[Table 2]

These sintered bodies were processed into cutting tools, and a cutting test was carried out under the following conditions to measure the tool life leading to chipping. The sintered body was broken in about 5 minutes. Therefore, it is understood that it is more preferable to mix the binder phase material by the ultrasonic mixing method than by the ball mill method using no dispersant.

Cutting test conditions: Work material: SCM420, HRC59-61, φ100 mm ×
L300mm with eight V-shaped grooves in the longitudinal direction. Tool shape: SNG432 NL-25 * 0.15-0.
2 Holder: FN11R Cutting conditions: V = 90 m / min, d = 0.23 mm, f = 0.
14mm / rev, dry

Example 3 A mixture of 92% by weight of Ti nitride and 18% by weight of Al was mixed at 1200.degree.
The compound subjected to the heat treatment was pulverized to prepare a binder phase powder. This powder is TiN, Ti ₂ AlN, Ti by XRD.
Peaks such as Al ₃ were observed. This binder phase powder was added to a cBN powder having an average particle size of 1.5 μm to have a volume content of cBN of Table 3.
The coating was carried out so as to have the proportions described in Table 1. Coating was performed using an RF sputtering PVD apparatus. This coated powder is
Observation by EM showed that the cBN powder was almost uniformly coated with TiN at an average layer thickness of 45 nm.
The TiN-coated cBN particles and the binder phase powder were mixed in a ball mill without using a dispersant. Mixing by the BM method was carried out by placing a ball having a diameter of 10 mm, cBN powder and binder powder in a pot, and performing wet mixing in ethyl alcohol at 235 rpm for 550 minutes. Then, this mixed powder was sintered at 4.9 GPa, an ultra-high pressure of 1380 ° C. and a high temperature. The XRDs of the obtained sintered bodies were all cBN, TiN,
TiB ₂ , AlB ₂ , AlN, Al ₂ O ₃ and WC were observed.

[0034]

[Table 3]

The structures of these sintered bodies were examined with a metallographic microscope.
When photographed at a magnification of 1500 times, cBN particles appearing black and a bonded phase appearing white were observed. Further, when an arbitrary straight line was drawn on this photograph and the thickness of the binder phase was measured, the average value and the standard deviation shown in Table 3 were obtained.

Further, these sintered bodies were processed into cutting tools, and cutting tests were carried out under the following conditions to measure tool life leading to chipping. Table 3 also shows the results.

Cutting test conditions: Work material: SCM415, HRC58-62, φ100 mm ×
L300mm shape with 6 V-shaped grooves in the longitudinal direction. Tool shape: SNG432 NL-25 * 0.15-0.
2 Holder: FN11R Cutting conditions: V = 110 m / min, d = 0.15 mm, f =
0.09mm / rev, dry

These results show that the content of cBN is preferably 45 to 70% by volume.

(Example 4) Binder phase powders were prepared by mixing binder phase raw material powders of various compositions and heat treating them at 1270 ° C for 28 minutes in a vacuum. This binder phase powder and a cBN powder having an average particle size of 1.8 μm were mixed by a ball mill method using a dispersant so that the volume content of cBN was 64%. Mixing by the BM method is as follows. A ball having a diameter of 10 mm, cBN powder and binder powder are placed in a pot and 245 rp.
m, 750 minutes by wet mixing in ethyl alcohol. 1.8% by weight of polyvinyl alcohol was added as a dispersant. Then, the mixed powder was 4.8 GPa, 133
The sintering was performed under an ultra-high pressure of 0 ° C. and a high temperature. X of the obtained sintered body
The peaks of the compounds shown in Table 4 were observed in RD.

[0040]

[Table 4]

The structures of these sintered bodies were examined with a metallographic microscope.
When observed at a magnification of 1000 times, cBN particles appearing black and a bonded phase appearing white were observed. When an arbitrary straight line was drawn on this photograph and the thickness of the binder phase was measured, the average value and standard deviation shown in Table 4 were obtained.

Further, these sintered bodies were processed into cutting tools, and cutting tests were performed under the following conditions, and the tool life leading to chipping was measured. The results shown in Table 4 were obtained.

Cutting test conditions: Work material: SCM415, HRC58-62, φ100 mm ×
L300mm shape with 6 V-shaped grooves in the longitudinal direction. Tool shape: SNG432 NL-25 * 0.15-0.
2 Holder: FN11R Cutting conditions: V = 190 m / min, d = 0.15 mm, f =
0.11mm / rev, dry

No. Each of the samples 18 to 25 had an average binder phase thickness of 1 μm or less and a standard deviation of 0.7 μm.
It is as follows. The tool life was about 30 minutes, which is a good result. Also, as you can see,
As the binder phase, carbides, nitrides, carbonitrides, borides of Al transition metals of the periodic table 4a, 5a, 6a, nitrides, borides, oxides of Al, at least one carbide of Fe, Co, Ni, It can be seen that at least one selected from the group consisting of nitrides, carbonitrides, borides, and their mutual solid solutions is good.

Example 5 78% by weight of Ti nitride,
16% Al, 4% Co and 2% N by weight
i was mixed and heat-treated at 1260 ° C. for 20 minutes in a vacuum to pulverize the compound to prepare a binder phase powder. This powder is X
In RD, peaks of TiN, Ti ₂ AlN, TiAl _{3 and the} like were observed. This binder phase powder and c having the average particle size shown in Table 5
The BN powder was mixed by an ultrasonic mixing method so that the volume content of cBN was 57%. For ultrasonic mixing, put cBN and binder powder in ethyl alcohol, and add 20.5k
Hz ultrasonic vibration was applied. Then, the mixed powder was sintered under a high pressure of 5.0 GPa and 1400 ° C. under a high temperature. The XRDs of the obtained sintered bodies were all cBN, Ti
_{N, TiB 2, AlB 2,} AlN, Al 2 O 3, WC were observed.

[0046]

[Table 5]

The structures of these sintered bodies were examined with a metallographic microscope.
When photographed at a magnification of 1500 times, cBN particles appearing black and a bonded phase appearing white were observed. An arbitrary straight line was drawn on this photograph and the thickness of the binder phase was measured. As a result, the average value and standard deviation shown in Table 5 were obtained.

Further, these sintered bodies were processed into cutting tools, and cutting tests were carried out under the following conditions, and the tool life leading to chipping was measured. The results shown in Table 5 were obtained.

Cutting test conditions: Work material: SCM415, HRC58-62, φ100 mm ×
L300mm shape with 6 V-shaped grooves in the longitudinal direction. Tool shape: SNG432 NL-25 * 0.15-0.
2 Holder: FN11R Cutting conditions: V = 100 m / min, d = 0.21 mm, f =
0.12mm / rev, dry

As is evident from the results, it can be seen that the loss can be suppressed when the average particle size of cBN is 0.1 μm or more and less than 2 μm.

[0051]

As described above, according to the present invention,
By reducing the variation in the thickness of the binder phase in the sintered body, it is possible to obtain a cBN sintered body having excellent wear resistance and fracture resistance.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akira Kukino 1-1-1, Koyokita-Kita, Itami-shi, Hyogo F-term in Sumitomo Electric Industries, Ltd. Itami Works 4G001 BA24 BA34 BA37 BA61 BA63 BB03 BB21 BB24 BB31 BB34 BB36 BB37 BB41 BB43 BB56 BB57 BC02 BC13 BC17 BC21 BC41 BC42 BD04 BD12 BD18 BD36 BE01 BE11 BE22 BE26

Claims (1)

[Claims] 1. A sintered body obtained by sintering cBN particles with a binder phase, wherein the binder phase is continuous in a two-dimensional manner, and the binder phase belongs to a group 4a, 5a, or 6a of the periodic table. Transition metal carbides, nitrides, carbonitrides, borides, Al nitrides, borides, oxides, at least one of Fe, Co, Ni carbides, nitrides,
Selected from the group consisting of carbonitrides, borides, and their mutual solid solutions1
The cBN content is 45-70% by volume, the average particle size of the cBN particles is 0.01 or more and less than 2.0 μm, and the average value of the binder phase thickness is 1.0 μm or less. A cBN sintered body having a standard deviation of 0.7 or less.