JP2003081677A - Dispersion-enhanced cbn-based sintered compact and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a CBN-based sintered compact which has simultaneously improved hardness and toughness, that is, wear resistance and resistance to fracture by uniformly dispersing an appropriate amount of superfine particles of CBN into a binding phase, and to provide a method of producing the same. SOLUTION: The CBN-based sintered compact consists of 1 to 25 vol% superfine CBN particles having a diameter of <=0.5 μm, 5 to 65 vol% binding phase and the balance being CBN particles having an average particle diameter of 1 to 10 μm. The superfine CBN particles are uniformly dispersed in the binding phase, and the volume ratio of the superfine CBN particles to the binding phase is 0.05 to 1.5. In the method of producing the CBN-based sintered compact, the superfine CBN particles and a binding material component are previously mixed and subjected to heat treatment, and the heat treated mixture is then finely pulverized and used as a starting material. Accordingly, the CBN- based sintered compact has higher hardness and fracture toughness, exhibits superior wear resistance, resistance to fracture and chipping resistance in comparison with a conventional CBN-based sintered compact containing fine granular CBN particles, and yields a cutting tool having a longer service life.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cubic boron nitride (CBN) -based sintered body which is most suitable as a cutting tool or wear resistant tool, and a method for producing the same, and more specifically, to a ceramic component for bonding CBN particles. The present invention relates to a dispersion-strengthened CBN-based sintered body in which abrasion resistance as well as chipping resistance and chipping resistance are significantly improved by uniformly dispersing ultrafine CBN particles into a dispersion and a method for producing the same.

[0002]

2. Description of the Related Art CBN has an excellent advantage as a tool material that it has the second highest hardness after diamond and excellent thermal conductivity, and that it has a lower affinity for iron than diamond. Many studies have been conducted on the performance improvement of a CBN-containing sintered body composed of CBN and a binder phase of ceramics or a metal, and among them, as a typical one proposed from the structure structure of the sintered body, JP 2000-21
8411, JP 2000-247746 A,
JP-A-2000-44348 and JP-A-2000-
There is 226263 publication.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
No. 411 gazette contains 30 to 90% by volume of fine-grained cubic boron nitride having an average grain size of 1 μm or less and coarse-grained cubic boron nitride having an average grain size of 2 to 10 μm. A cubic boron nitride sintered body cutting tool is described in which fine-grained cubic boron nitride <bonding material <coarse-grained cubic boron nitride. Further, JP-A-2000-247746 discloses that fine grained cubic boron nitride 30-9 having an average grain size of 1 μm or less.
In addition to containing 0% by volume and coarse-grained cubic boron nitride having an average particle size of 2 to 10 μm, AlN and Al 2 O 3 were contained in the binder, and the periodic table 4a, 5a, 6a by X-ray diffraction measurement was used.
A cutting tool for cubic boron nitride sintered bodies is described in which the peak strength ratios of borides of group elements, non-boriding compounds of these elements, and cubic boron nitride are limited.

Further, in Japanese Unexamined Patent Publication No. 2000-44348, high-hardness firing consisting of 50 to 80% by volume of high-pressure phase boron nitride and 50 to 20% by volume of a binder phase composed of titanium compounds (TiC, TiN, TiCN) and aluminum. In the aggregate, the high-pressure phase boron nitride contains coarse particles 60 of 1 to 8 μm.
A high-hardness sintered body for cutting cast iron having 80% by volume and 20 to 40 volume of 0.02 to 1 μm fine particles is described.

CBN described in these three publications
By mixing fine CBN particles in the base sintered body, the CBN particles may fall off during cutting, wear of the binder,
Although it prevents tool wear and chipping due to falling off,
Since the amount of fine CBN is large or the grain size is significantly larger than that of the binder, agglomerates of fine CBN are formed in the structure of the sintered body, which in turn causes wear due to particle loss and defects from this aggregate. There is a problem that it is easy to do.

Next, Japanese Patent Laid-Open No. 2000-226263 discloses cubic nitriding coated with one or more kinds of fine particles selected from carbides, nitrides, carbonitrides of group 4a, 5a, and 6a metals. A cubic boron nitride composite cermet tool using boron particles and a method for making the same are described.
In the CBN sintered body described in this publication, since the binder particles in the vicinity of the CBN particles are fine, the sintering property is improved,
Although the hardness can be improved and the life of the CBN particles can be improved by preventing the particles from falling off, there is a problem that the performance improvement is small because the strength and wear resistance of the binder are insufficiently improved.

The present invention has solved the above-mentioned problems. Specifically, an appropriate amount of ultrafine CBN is uniformly dispersed in the binder to form a binder phase having a fine structure and the binder itself. By strengthening the dispersion, the hardness, strength, and
An object of the present invention is to provide a dispersion-strengthened CBN-based sintered body having improved toughness and greatly improved wear resistance, fracture resistance and the like, and a method for producing the same.

[0008]

Means for Solving the Problems The inventors of the present invention have studied simultaneous improvement of wear resistance and fracture resistance of a sintered body composed of CBN and a binder phase.
If the appropriate amount of is dispersed uniformly, the grain growth of the binder phase during sintering is suppressed and the binder phase becomes a uniform fine grain structure, and at the same time the binder phase is dispersed and strengthened by the ultrafine CBN, and the strength and toughness are greatly improved. The chipping resistance and chipping resistance are improved, and because the ultrafine CBN particles that are uniformly and finely dispersed are difficult to drop during cutting, the wear resistance of the binder phase itself is improved, and the binder phase is dispersed and strengthened. For this, ultrafine CBN and a binder component are mixed in advance and heat-treated, and this is pulverized to obtain a fine powder of a dispersion-strengthening binder, which is then mixed with CBN powder of a normal grain size and sintered. Based on the knowledge obtained, the present invention has been completed.

The dispersion-strengthened CBN-based sintered body of the present invention comprises 1 to 25% by volume of ultrafine CBN particles having an average particle diameter of 0.5 μm or less and a binder phase 5 mainly composed of ceramics and / or iron group metal. 65% by volume and the rest having an average particle size of 1 to 10 μm
In the CBN-based sintered body composed of CBN particles and unavoidable impurities, the ultrafine CBN particles are uniformly dispersed in the binder phase, and the volume ratio of the ultrafine CBN particles to the binder phase is 0.1 to 1. It is characterized by being 0.0.

The ultrafine CBN particles in the dispersion-strengthened CBN-based sintered body of the present invention have no effect of dispersion strengthening because it becomes difficult to uniformly disperse them in the binder phase when the average particle size increases beyond 0.5 μm. On the other hand, if the content is less than 1% by volume, there are few dispersed particles and there is no effect of improving wear resistance and fracture resistance by dispersion strengthening. Conversely, if it exceeds 25% by volume, aggregates are formed in the binder phase. Both wear and loss increase.
Further, it is practically preferable that the average particle size of CBN be 0.01 μm or more because it is difficult to produce a CBN having an average particle size of less than 0.01 μm.

The ultrafine CBN particles in the dispersion-strengthened CBN-based sintered body of the present invention are uniformly dispersed in the binder phase. Specifically, three or more particles are united to form an aggregate. The ratio of the contact area between CBN and CBN to the contact area between CBN and the binder phase is 0.5 or less.
Further, if the volume ratio to the binder phase (amount of ultrafine CBN / amount of binder phase) is less than 0.1, the grain growth suppressing effect of the binder phase during sintering due to dispersion of the ultrafine CBN is small and a coarse structure is formed. Since the effect of strengthening the dispersion of ultrafine CBN is small, there is no effect of improving wear resistance and fracture resistance. On the contrary, when it exceeds 1.5, it becomes difficult to uniformly disperse in the binder phase, and aggregates are formed. Since both wear resistance and fracture resistance decrease,
It was set to 0.1 to 1.0.

The binder phase in the dispersion-strengthened CBN-based sintered body of the present invention is specifically TiC, TiN, TiN, Ti.
(CN), ZrN, HfC, NbN, TaC, WC, Z
Periodic Table 4a, 5 of rO ₂ , TiB ₂ , MoSi ₂ etc.
Carbides, nitrides, oxides, borides of a and 6a group elements,
Silicides, aluminum nitrides such as Al ₂ O ₃ , AlN, and AlB ₁₂ , oxides, borides, AlCTi ₂ , (T
iAl) N, AlBMo and other complex compounds, mutual solid solutions, metals such as Co, Ni and Fe, alloys and mixtures of these metals with the above compounds, complex compounds and the like can be mentioned. In particular, the average particle size of these binder phases is 1
It is preferable that the particle size is not more than μm because the ultrafine CBN particles are uniformly dispersed in the binder phase. Further, from the viewpoint of difficulty in the manufacturing process, it is practically preferable that the thickness is 0.02 μm or more.

If the average particle size of the remaining CBN particles in the dispersion-strengthened CBN-based sintered body of the present invention is less than 1 μm, the amount of the binder phase is relatively insufficient and it is difficult to sinter, and conversely 10 μm.
If it exceeds the range, the contact between CBN particles becomes strong, so that high-pressure sintering or an increase in the amount of the binder phase is required.

When the ultrafine CBN particles in the dispersion-strengthened CBN-based sintered body of the present invention are surrounded by a Ti compound of titanium boride and / or titanium nitride having an average layer thickness of 0.01 to 0.2 μm, they are bonded. It is preferable because the adhesive strength with the phase is increased and the falling wear of the ultrafine CBN is less likely to occur. T
The enclosure with the i compound is formed on the surface of the ultrafine CBN particles by a diffusion reaction when sintering the mixed powder in which the ultrafine CBN particles and the binder phase component particles are uniformly dispersed. The thickness of the Ti compound layer is preferably in a range not exceeding the diameter of the ultrafine CBN particles.

The dispersion-strengthened CBN-based sintered body of the present invention can be obtained by mixing ultrafine CBN powder as a raw material, binder phase forming powder, and normal particle CBN powder, and then sintering by ultrahigh pressure. The following manufacturing steps and methods are preferable for exhibiting the performance.

That is, the method of manufacturing the dispersion-strengthened CBN-based sintered body of the present invention uses ultrafine CB having an average particle size of 0.5 μm or less.
N powder and metal of Group 4a, 5a, 6a group of periodic table,
First step of mixing and pulverizing carbide, nitride, oxide, boride, aluminum metal, oxide, nitride, boride, silicide, and at least one or more binder phase forming powders of iron group metals , Mixed powder in vacuum, 700 ℃ ~ 10
Second step of heat treatment at 00 ° C., third step of pulverizing the heat-treated mixed powder, the obtained ultrafine CBN-dispersed binder phase powder and, if necessary, the binder phase forming powder and 1 to 10 μm
Fourth step of mixing with mCBN powder, then pressure 4-6
It is characterized by comprising a fifth step of sintering under an ultrahigh pressure and high temperature of GPa and a temperature of 1400 to 1600 ° C.

The binder phase forming powder in the method for producing the dispersion-strengthened CBN-based sintered body of the present invention comprises TiN _x , Ti (CN) _x (x = 0.6-0.
A mixed powder containing 9) as a main component or a mixed powder containing metal Al and metal Co as main components is preferable.

The second step in the method for producing the dispersion-strengthened CBN-based sintered body of the present invention is the binder phase component such as TiN and A.
1 is reacted to generate brittle Ti ₂ AlN or the like, and promotes uniform dispersion of the accompanying ultrafine CBN particles in the binder phase by fine grinding in the third step.

[0019]

The operation of the dispersion-strengthened CBN-based sintered body of the present invention is as follows.
The ultrafine CBN particles dispersed in the binder phase make the binder phase into a fine structure and the hardness of the binder phase by the dispersion strengthening mechanism.
It has the effect of improving strength and toughness to simultaneously improve wear resistance, chipping resistance and chipping resistance. The manufacturing method is to heat-treat a mixture of ultrafine CBN powder and binder phase forming powder and then pulverize it. That is, the ultrafine CBN particles have a function of uniformly and finely dispersing in the binder phase.

[0020]

Example 1 CBN powder (UF having an average particle size of 0.1 μm)
/ CBN), 2.0 μm CBN powder (M / CB
N) and 5.5 μm CBN powder (C / CB
N), 1.1 μm TiN _0.8 powder, 0.9 μm Al
Powder, 0.2 μm Al ₂ O ₃ powder, 1-2 μm Ti
C, HfN, TaC, WC, and Co were blended to the composition shown in Table 1, and this was mixed and pulverized for 48 hours with a ball mill using a cemented carbide ball and a methanol solvent. Powders A to F for the binder phase used in the present invention were obtained by heating in vacuum for 1.0 hour at the temperature shown in Table 1 and then pulverizing with the same ball mill for the time shown in Table 1. Got

[0021]

[Table 1]

Next, the binder phase powders A to F and the above-mentioned respective raw material powders were blended in the composition shown in Table 2, and this was mixed with a cemented carbide ball and a ball mill using a methanol solvent for 24 hours (however, in comparison. The product was mixed for 48 hours and dried in argon to prepare each mixed powder. These press-formed bodies were set on a disc base metal made of cemented carbide to form capsules, and then a pressure of 5.5 GPa, a temperature of 1500 ° C., and a holding time of 30 minutes were used by using an ultra-high pressure and high temperature apparatus. Then, the products of the present invention 1 to 7 and comparative products 1 to 7 were obtained by sintering.

[0023]

[Table 2]

The CBN-based sintered bodies of the present invention products 1 to 7 and comparative products 1 to 7 thus obtained were cut by electric discharge machining, ground by diamond, and lapped to prepare samples for measurement. First, Table 2 also shows the measurement results of the fracture toughness values by the Knoop hardness and the Vickers indentation method. Next, using a field emission analytical electron microscope, the dispersion state of the ultrafine CBN in the binder phase, the dispersion amount and the volume ratio to the binder phase, the average particle diameter, the average thickness of the enclosed Ti compound and the binder phase The average particle diameter and the like were measured (confirmed by observing the fracture surface).
The results are shown in Table 3.

[0025]

[Table 3]

[0026]

[Embodiment 2] Each of the sintered bodies of the present invention products 1 to 6 and comparative products 1 to 6 obtained in the embodiment 1 is cut by electric discharge machining, brazed to a cemented carbide chip base metal, and diamond diamond is used. After grinding, cutting test tip shape: TNMA16
0408 was prepared. Then, a cutting test was conducted under the following conditions, and the results are shown in Table 4. (A) Peripheral continuous dry cutting Work material: SCM415 (HR
C60.9-61.7), cutting speed: 150 m / mi
n, depth of cut: 0.5 mm, feed: 0.1 mm / re
v, evaluation criteria: average flank wear amount VB = 0.2 mm or cutting time until intermediate fracture (B) outer peripheral continuous wet cutting Work material: FC30 (HB21
0-230), cutting speed: 500 m / min, depth of cut: 0.5 mm, feed rate: 0.15 mm / rev, evaluation standard: average flank wear amount VB = 0.2 mm or cutting time until midway fracture (C) Peripheral continuous wet cutting Work material: Inconel 718,
Cutting speed: 120 m / min, Depth of cut: 0.3 mm,
Feed rate: 0.10 mm / rev, Evaluation criteria: Boundary wear amount VN = Cutting time until reaching 0.3 mm

[0027]

[Table 4]

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4G001 BA03 BA12 BA24 BA34 BA36                       BA37 BA41 BA43 BA48 BA61                       BA63 BB03 BB12 BB24 BB34                       BB37 BB43 BB48 BB61 BC13                       BC43 BC52 BC54 BD12 BD16                       BD18

Claims (5)

[Claims] 1. Ultrafine CBN particles having an average particle diameter of 0.5 μm or less.
1 to 25% by volume of particles, 5 to 65% by volume of a binder phase containing ceramics and / or an iron group metal as a main component, and the rest of the CBN-based sintered body consisting of CBN particles having an average particle size of 1 to 10 μm and inevitable impurities. In, the ultrafine CBN particles are uniformly dispersed in the binder phase, and the volume ratio of the ultrafine CBN particles to the binder phase is 0.1 to 1.0. Sintered body. 2. The dispersion-strengthened CBN-based sintered body according to claim 1, wherein the binder phase has an average particle diameter of 1 μm or less. 3. The bonding phase is represented by Periodic Table Nos. 4a, 5a, 6
Consists of at least one or more of a-group element carbides, nitrides, oxides, borides, silicides, aluminum nitrides, oxides, borides, and their complex compounds, mutual solid solutions, and iron group metals. Claim 1 characterized by the above.
Alternatively, the dispersion-strengthened CBN-based sintered body according to item 2. 4. The ultrafine CBN particles have an average layer thickness of 0.0.
The dispersion-strengthened CBN-based sintered body according to claim 1, wherein the dispersion-strengthened CBN-based sintered body is surrounded by a Ti compound of 1 to 0.2 μm of titanium boride and / or titanium nitride. 5. An ultrafine CBN powder having an average particle size of 0.5 μm or less, and metals, carbides, nitrides, oxides, borides, aluminum metals of elements of groups 4a, 5a and 6a of the periodic table,
First step of mixing and pulverizing oxide, nitride, boride, silicide, and at least one or more binder phase forming powders of iron group metal, the mixed powder in vacuum at 700 ° C to 1000 ° C
Second step of heat treatment at 0 ° C, third step of finely pulverizing the heat-treated mixed powder, fourth step of mixing the obtained ultrafine CBN dispersed powder and optionally the binder phase forming powder and 1-10 µm CBN powder And a fifth step of sintering at a pressure of 4 to 6 GPa and a temperature of 1400 to 1600 ° C. under an ultrahigh pressure and high temperature.