JP2000044350A - Cubic bn 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 a sintered compact obtained by sintering cBN grains 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 <=1.5 μm and the standard deviation thereof is <=0.9. The content of the cBN is 45-70% expressed in terms of vol.% and the average grain size of the cBN grains is >=2 and <=6 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.

[0003] With this type of sintered body, it is difficult to achieve both hardness and strength.
No. 62-25630, Japanese Patent Publication No. 62-25631, JP-A-5-1862
No. 72 publication.

[0004]

However, each of the above techniques is not always sufficient in terms of both hardness and strength. For example, when the above-described sintered body is used for a cutting tool, the cutting edge becomes sharp due to flank wear and crater wear, and this cutting edge is liable to be broken, resulting in a problem that the tool life is not stable.

Accordingly, it is a main object of the present invention to provide a cBN sintered body having excellent fracture resistance by optimizing crater resistance and 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 1.5 μm or less, and its standard deviation is 0.9 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 2 to 6 μm. The average particle size means a particle size at which the cumulative volume% becomes 50%.

A conventional cBN sintered body (cBN particles having an average particle size of 2 to 6 μm) has a standard deviation of binder phase thickness exceeding 0.9. That is, the thickness variation of the binder phase is large,
Some parts occupy a large volume solely by the binder phase. Since this portion is a portion (defect) of low strength in the sintered body, cracks are easily developed, and the chipping resistance of the tool is not sufficient.

[0008] In high-speed cutting, the strength of the material is reduced due to the high temperature of the cutting edge. In addition, crater wear develops and the shape of the cutting edge becomes sharp, which also reduces the strength of the cutting edge. It is presumed that the impact applied to the cutting edge in such a state causes a crack to be generated in a portion where the crater wear has occurred in parallel with the cutting edge, and that the crack propagates due to the intermittent impact and leads to loss.

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. The average thickness of the binder phase and its standard deviation are 1.5 μm, 0.
If it exceeds 9 μm, 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 average particle diameter of the cBN particles is less than 2 μm, the heat resistance of the particles is inferior, crater wear is likely to develop, and the fracture resistance is inferior.
If it exceeds, the chipping resistance is inferior to the impact during cutting,
The particle size of the cBN particles is suitably from 2 to 6 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 3 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 50 nm. In addition, No. No dispersant was used in the mixing of the two.

Ultrasonic mixing method → cB in ethyl alcohol
N and the powder of the binder were charged and mixed by applying ultrasonic vibration of 20 kHz. BM method: A ball having a diameter of 10 mm, cBN powder and binder powder were placed in a pot, and wet-mixed in ethyl alcohol at 250 rpm for 800 minutes. Dispersant → 2% by weight of polyvinyl alcohol as dispersant
Was added.

[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 = 180 m / min, d = 0.3 mm, f = 0.
15mm / rev, dry

As is apparent from the results, when the average value of the binder phase thickness is 1.5 μm or less and the standard deviation is 0.9 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. A method of coating the cBN particles with a binder phase is also effective.

(Example 2) 75% by weight of Ti nitride,
22% by weight Al, 2% by weight Co and 1% by weight 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 4.8 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: The powder of cBN and the binder was put into acetone and mixed by applying ultrasonic vibration of 25 kHz. BM method: A ball having a diameter of 10 mm, cBN powder and binder powder were put in a pot, and wet-mixed in ethyl alcohol at 200 rpm for 600 minutes.

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 a cBN particle) and a bright part (a part corresponding to a 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 = 150 m / min, d = 0.25 mm, f =
0.11mm / rev, dry

Example 3 A mixture of 80% by weight of Ti nitride and 20% 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 3.5 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 with an average layer thickness of 50 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 putting a ball having a diameter of 10 mm, cBN powder and binder powder into a pot and performing wet mixing in acetone at 260 rpm for 650 minutes. Then, the mixed powder was 4.8.
GPa was sintered at a high pressure of 1350 ° C. under 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 = 160 m / min, d = 0.2 mm, f = 0.
13mm / rev, dry

These results show that the content of cBN is preferably 45 to 70% by volume. In particular, good results were obtained at 60 to 70% by volume.

(Example 4) Binder phase powders having various compositions were mixed, and a compound heat-treated at 1230 ° C for 32 minutes in a vacuum was pulverized to prepare a binder phase powder. This binder phase powder and a cBN powder having an average particle size of 4.1 μm were mixed by a ball mill method using a dispersing agent such that the volume content of cBN was 62%. For mixing by the BM method, a ball having a diameter of 10 mm, cBN powder and binder powder were put in a pot, and the mixture was heated to 190 rp.
m, 700 minutes by wet mixing in acetone. The dispersant is polyvinyl alcohol. Then, the mixed powder was sintered under a high pressure of 5.1 GPa, a high pressure of 1310 ° C. and a high temperature. The peaks of the compounds listed in Table 4 were observed in the XRD of the obtained sintered body.

[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

As can be seen, as the binder phase, carbides, nitrides, carbonitrides, and the like of transition metals of Groups 4a, 5a and 6a of the periodic table are used.
Boride, nitride of aluminum, boride, oxide, Fe, Co,
It can be seen that at least one selected from the group consisting of at least one of carbides, nitrides, carbonitrides, borides, and mutual solid solutions of Ni is preferable.

Example 5 70% by weight of Ti nitride,
25% by weight Al, 3% by weight Co and 2% by weight N
i was mixed and heat-treated in vacuum at 1250 ° C. for 25 minutes 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 powder obtained by ultrasonically mixing the BN powder so that the volume content of cBN becomes 57% is 4.9 GPa, an ultra-high pressure of 1320 ° C.,
Sintered under high temperature. The ultrasonic mixing was performed by charging cBN and a binder powder into ethyl alcohol and applying ultrasonic vibration of 23 kHz. The XRDs of the obtained sintered bodies were all cBN, TiN, TiB ₂ , AlB ₂ , AlN, Al ₂
O ₃ and 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 = 170 m / min, d = 0.25 mm, f =
0.14mm / 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 2.0 to 6.0 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.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Junichi Shiraishi 1-1-1, Kunyokita, Itami-shi, Hyogo F-term in Sumitomo Electric Industries, Ltd. Itami Works (reference) 3C046 FF25 FF27 FF35 FF41 FF55 FF57 4G001 BA34 BA38 BA39 BA61 BA63 BB03 BB21 BB24 BB25 BB26 BB31 BB34 BB36 BB37 BB38 BB39 BB41 BB43 BB44 BB56 BB57 BB61 BC01 BC02 BC13 BC21 BC46 BD12 BD13 BD18 BE15 BE22

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 2 to 6 μm, the average value of the binder phase thickness is 1.5 μm or less, and the standard deviation is 0. The cBN sintered body is not more than 0.9.