JPH10182242A - High hardness and high toughness sintered compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sintered compact for a cutting tool having improved wear and chipping resistance by sintering high pressure phase type boron nitride powder coated with a binder. SOLUTION: This sintered compact consists of high pressure phase type boron nitride coated beforehand with a group IVa, Va or VIa element, Al, Si, an iron family element or their intermetallic compd. in 5-300nm average thickness, a bonding phase selected from among nitrides, carbides, borides and oxides of groups IVa, Va and VIa element, their solid solns., Al compds., Al and iron family metals and inevitable impurities. In an arbitrary region contg. at least 100 pieces high pressure phase type boron nitride grains, the number of grains coming in contact with other high pressure phase type boron nitride grains is 20 to <50%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a sintered body, and more specifically, to a cutting tool, a milling tool, an end mill, and the like having improved wear resistance and chipping resistance. The present invention relates to a high-pressure phase-type boron nitride-based high hardness and toughness sintered body for cutting tools.

[0002]

2. Description of the Related Art High-pressure phase boron nitride represented by cBN (cubic boron nitride) is a hard material next to diamond, and has a lower reactivity with iron-based materials than diamond. And cBN sintered bodies are used for various cutting tools.

[0003] Materials having high hardness and high toughness include:
Not only for cutting tools but also for various applications such as wear-resistant parts provided on sliding parts and impact-resistant parts used for defense walls.

[0004] cBN is a typical hard-to-sinter material along with diamond and is a high-pressure stable phase.
In order to sinter particles only, the temperature must be 2000 ° C or higher and 8GP
a sintering conditions of 1400 or more are required.
Under industrial sintering conditions of about 4 ° C. and 4 ° C., no bonding occurs between the cBN particles.

[0005] On the other hand, a sintered body composed of cBN particles and a binder phase reacts at the grain boundary between the cBN particles and the binder phase under the above-mentioned industrial sintering conditions. A sintered body can be obtained.

[0006] However, the conventional cBN sintered body is
BN powder and binder powder are mixed and sintered,
Since the mixed state of the cBN particles and the binder was not completely homogeneous, the cBN particles came into direct contact with each other in a part of the sintered body, or the cBN particles came into contact with a binder phase that did not easily react with the cBN particles. There was a portion where sintering did not occur. Therefore, there is a problem that the wear resistance and the fracture resistance are inferior.

As an attempt to solve this problem,
A representative one proposed is disclosed in Japanese Patent Application Laid-Open No. 58-5824.
7, JP-A-58-60678, JP-A-5-
There is 186844 gazette.

[0008]

Problems to be Solved by the Invention JP-A-58-5824
No. 7 discloses a cubic boron nitride having a binder phase composition comprising one or more borides and carbides of Ti, Hf, Zr and Mo, and having an average thickness of 0.1 to 2 μm. A high-toughness boron nitride-based ultra-high pressure sintered material for cutting and wear-resistant tools in which the nitride has a structure surrounding cubic boron nitride is disclosed.

Japanese Patent Application Laid-Open No. 58-60678 discloses a cubic boron nitride having a binder phase composition comprising at least one nitride of at least one of Ti, Hf and Si and a carbide, and having a binder phase composition of 0.1%.
A high toughness boron nitride based ultra-high pressure sintered material for cutting and wear resistant tools wherein the boride having an average thickness of 〜2 μm surrounds cubic boron nitride is disclosed.

Further, Japanese Patent Application Laid-Open No. Hei 5-186844 discloses that cubic boron nitride and / or wurtzite boron nitride
a, 5a, 6a group metals, Al, Si, Fe, Ni, Co
Carbides, nitrides, oxides, borides, oxides of rare earth metals, nitrides of these solid solutions, or Fe, Ni, C
a binder phase composition comprising at least one of
Ti, Hf, Zr, Mo, A with an average thickness of ~ 90 nm
1, high-toughness nitride for cutting and wear-resistant tools wherein at least one of nitrides, borides of Si and their mutual solid solutions has a structure surrounding cubic boron nitride and / or wurtzite boron nitride A boron based ultra high pressure sintering material is disclosed.

The high-pressure phase-type boron nitride-based sintered body described in these publications is obtained by coating the high-pressure phase-type boron nitride particles with a binder and sintering the same. The unsintered portion in the compact can be reduced, and the wear resistance and fracture resistance are improved.

However, these sintered bodies are: 1. The coating binder is a ceramic which is a brittle material; Since ceramics are thermally and chemically stable and do not react well with high pressure phase boron nitride,
Due to insufficient adhesion strength between the coated binder and the high-pressure phase-type boron nitride particles, etc., the coated binder is mixed when mixed with a binder other than the coated binder and when pressed by an ultra-high pressure sintering device and a hot press device. The material easily breaks off from the high-pressure phase-type boron nitride particles, and even in the high-pressure phase-type boron nitride-based sintered body using these powders, the high-pressure phase-type boron nitride particles frequently come into contact with each other. As a result, the homogenization of the sintered body structure was insufficient.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has improved wear resistance and chipping resistance, such as cutting tools, milling tools and end mills. It is an object of the present invention to provide a high-pressure phase-type boron nitride-based high hardness and high strength sintered body for use.

[0014]

According to the present invention, there is provided a high-hardness and high-toughness sintered body comprising a high-pressure phase-type boron nitride, a remaining binder phase and unavoidable impurities, which are coated with a binder before sintering. The present invention relates to a sintered body having the obtained high-pressure phase-type boron nitride powder. The coating binder is composed of elements of the periodic table 4a, 5a, 6a, Al, S
At least one selected from the group consisting of i, iron group elements, and these intermetallic compounds is coated with an average thickness of 5 to 300 nm. The binder powder other than the coated binder is composed of a periodic table 4a, 5a, 6a group element, Si nitride,
Carbides, borides, oxides and their solid solutions, Al
The sintered body is made of at least one selected from the group consisting of a compound, Al, and an iron group metal, and contains at least 100 high-pressure phase-type boron nitride particles constituting the sintered body. In any region, the number of particles in contact with other high-pressure phase-type boron nitride particles (hereinafter referred to as a contact ratio between high-pressure phase-type boron nitride) is 20% or more and less than 50%. I do.

According to a preferred embodiment of the present invention, the above-mentioned coated binder is coated with cubic boron nitride which is an intermetallic compound of at least one selected from the group consisting of Ti, Zr and Hf and Al. Al, which is a binder powder other than the material
At least one selected from the group consisting of Co, Ni, W, and WC
Sintered while infiltrating the seed.

The high-pressure phase-type boron nitride is cubic-type boron nitride, and the coating binder is Ti, Zr, H
an intermetallic compound of at least one selected from the group of f and Al, wherein the binder powder is TiN, ZrN,
It is also preferable to use at least one selected from the group consisting of HfN, TiC, ZrC, HfC, TiAlN, and a solid solution thereof, Al, and an Al compound.

Rather than coating with Al alone, Ti, Zr,
The interaction of Hf has the effect of increasing the reactivity with cBN.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The sintered body of the present invention is formed on a surface of high-pressure phase-type boron nitride by chemical vapor deposition (CVD), physical vapor deposition (PVD), electroless plating, mechanical mixing ( Using a high-pressure phase-type boron nitride powder coated with a binder by, for example, mechanofusion or the like, sintering can be performed by a conventional plasma sintering apparatus, hot press apparatus, or ultra-high pressure sintering apparatus. The binder other than the coated binder is infiltrated in situ during sintering or mixed with the binder-coated high-pressure phase-type boron nitride powder by a conventional powder metallurgy method such as a ball mill method. And sintering.

Hereinafter, embodiments of the present invention will be described using specific numerical values.

[0020]

EXAMPLES Example 1 cBN powder having an average particle size of 15 μm and various intermetallic compound powders were mixed with PEG (polyethylene glycol) and PAMA.
In a mixed solution of (polyalkyl methacrylate) and ethyl alcohol, wet mixing was performed while drying using a planetary mill.

The dried mixed powder was subjected to a vacuum heat treatment in a vacuum furnace at 10 ^-5 Torr at 1200 ° C. for 1 hour. The powder surface after the heat treatment was observed by EPMA. It was found that various intermetallic compounds were uniformly coated.

Next, the coated cBN powder and the binder powder were filled into a Mo capsule filled with an Al plate, and then 5.2 GPa and 1480 ° C. were applied by a belt type ultra-high pressure device.
Under the conditions described above, sintering was performed for 20 minutes while infiltrating the Al solution. For comparison, a cBN sintered body using a starting material having the same composition and not coated with a binder was also manufactured.

After sintering, the superhard container is recovered and removed by grinding, and the sintered body is subjected to X-ray analysis, SEM, TEM, EDX
Analysis was performed by FE-AES with a beam system of φ45 nm, and the composition and structure of the sintered body were analyzed. The contact ratio between cBN particles was determined from a FE-AES surface analysis image. Table 1 shows details of the manufactured sintered bodies.

[0024]

[Table 1]

From this sintered body, a length of 6 mm, a width of 3 mm,
Cut out a test specimen 0.5 to 0.55 mm thick, 4 m
The bending strength (strength) was measured under the condition of m span.

Further, a sintered body chip for cutting (ISO standard: SNMG120808) was prepared, and a cutting test was performed under the following conditions.

Work material: Round bar of SKH51 material with hardness HRC60 Cutting speed: V80 m / min, depth of cut 0.3 mm, feed 0.15 mm / rev. Table 2 shows the results of a 30 minute wet cutting test.

[0028]

[Table 2]

Example 2 As shown in Table 3, various kinds of metals, intermetallic compounds, AlB2 and TiB2 were applied to a high-pressure phase-type boron nitride powder having an average particle size of 0.5 μm using an RF sputtering PVD apparatus.
And AlN. At this time, the degree of vacuum in the furnace was set at 10
^-4 Torr, Ar gas was introduced, and 10 ^-3 Torr
The coating was performed under the conditions of electric power of 5 KW, frequency of 15 MHz, and 10 hours while being heated to 300 ° C. while being kept in an atmosphere of rr.

Next, the mixed powder obtained by mixing the coated high-pressure phase-type boron nitride powder and the binder powder so as to have the composition shown in Table 3 was subjected to a ball mill, and then a belt type ultra-high pressure apparatus was prepared in the same manner as in Example 1. Sintering at 4.5 GPa and 1300 ° C. for 10 minutes. However, no infiltration was performed. For comparison, c using starting material not coated with binder
Some BN sintered bodies were also produced.

Table 3 shows the results of analysis of the composition and structure of the manufactured sintered body in the same manner as in Example 1.

[0032]

[Table 3]

Further, in the same manner as in Example 1, the bending strength (strength) was measured and the cutting evaluation was performed under the following conditions.

Tip: SNGN120808 SCM420H of hardness HRC60 having V-shaped grooves at six locations on the outer periphery Cutting speed: V150 m / min, depth of cut 0.2 mm, feed 0.1 mm / rev. Table 4 shows the results of the dry cutting test.

[0035]

[Table 4]

Example 3 The average particle size was 1 using an RF sputtering PVD apparatus.
Al was coated on 0 μm cBN powder. At this time, Ar gas was introduced while maintaining the degree of vacuum in the furnace at 10 ⁻⁴ Torr, and the atmosphere was maintained at 10 ⁻³ Torr, and the temperature was reduced to 200 ° C.
5kw power, 12MHz frequency, 3
The coating was performed under the condition of 00 minutes.

After recovering the mixed powder, the surface of the powder was examined by TEM.
As a result, the cBN powder was found to contain Al at an average layer pressure of 150.
It was found that the coating was uniform in nm.

Next, the cBN powder coated with the binder was filled into a Mo capsule filled with an Al plate, and was then subjected to 4.8 GPa and 1450 ° C. using a belt type ultra-high pressure device.
Sintered for 15 minutes. For comparison, a cBN sintered body using a starting material having the same composition and not coated with a binder was also manufactured.

After sintering, the Mo capsules were collected, removed by grinding, and the sintered body was analyzed by X-ray analysis, ICP, TEM, and AES to analyze the composition and structure of the sintered body. Table 5 shows details of the manufactured sintered bodies.

[0040]

[Table 5]

For comparison, a commercially available cBN sintered body was also investigated. Next, from this sintered body, a length of 6 m
m, a width of 3 mm, and a thickness of 0.4 to 0.45 mm.
% Nitric acid (40 ml) diluted twice and a concentration of 45 to 5
Dissolution treatment was performed at 140 ° C. for 3 hours with hydrofluoric / nitric acid mixed with 10% of 0% hydrofluoric acid. afterwards,
Using this measurement test piece, the transverse rupture strength was measured under a condition of 4 mm span. At this time, the bending strength before the dissolution treatment was also measured. Table 6 shows the results of the transverse rupture force.

[0042]

[Table 6]

Further, a sintered chip for cutting having a square main surface (ISO standard: SNMG120812) was formed, and a cutting test was performed under the following conditions.

Work material: round bar of FCD450 having hardness HB180 having two V-shaped grooves at two outer circumferences Cutting speed: V200 m / min, depth of cut 0.5 mm, feed 0.2 mm / rev. FIG. 1 shows the results of the wet cutting test.

Although only the cBN sintered body of the present invention was separated after the melting treatment, the other cBN sintered bodies were:
All had sufficient strength (flexural strength) for handling.

The reason for this is that, in many cBN sintered bodies other than the present invention, the cBN particles are in direct contact with each other in many parts, so that hydrofluoric nitric acid, which can dissolve components other than cBN, is used. It is presumed that it could not penetrate all the way inside.

That is, in the sintered body of the present invention, since the outer periphery of the cBN particles is covered with the binder phase component dissolved in the hydrofluoric nitric acid, it is presumed that the cBN particles have been disintegrated into a powder form by the dissolution treatment. Is done.

[Brief description of the drawings]

FIG. 1 is a diagram showing the results of a cutting test.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akira Kugino 1-1-1, Koyo Kita, Itami City, Hyogo Prefecture Inside Itami Works, Sumitomo Electric Industries, Ltd. (72) Inventor Shinya Uesaka 1-1, Koyo Kita Kita, Itami City, Hyogo Prefecture No. 1 Sumitomo Electric Industries, Ltd. Itami Works

Claims (5)

[Claims] 1. A sintered body comprising a high-pressure phase-type boron nitride, a residual binder phase and an unavoidable impurity is a sintered body having a high-pressure phase-type boron nitride powder coated with a binder before sintering, The coated binder is made of a periodic table 4a, 5a, 6a group element, A
1, at least one selected from the group consisting of iron, iron group elements and intermetallic compounds thereof, coated with an average thickness of 5 to 300 nm. 4a, 5a, 6
the sintered body comprises at least one element selected from the group consisting of group a elements, Si nitrides, carbides, borides, oxides, and solid solutions thereof, Al compounds, Al, and iron group metals; 20% or more and less than 50% of particles in contact with other high-pressure phase-type boron nitride particles in an arbitrary region in the sintered body containing at least 100 high-pressure phase-type boron nitride particles. A high-hardness, high-toughness sintered body characterized in that: 2. The high hardness and high toughness sintered body according to claim 1, wherein the content of cBN particles in the sintered body is 80% or more and 99.9% or less by volume%. 3. The average particle size of the cBN particles is 20 μm or less, the length is 6 mm, the width is 3 mm, and the thickness is 0.4 to 0.45.
mm, a 2-fold dilution of nitric acid having a concentration of 60 to 65% in a closed container.
and 4 to 50% hydrofluoric acid mixed with 10 ml of hydrofluoric acid at 120 to 150 ° C. for 3 to 5 hours. transverse rupture strength is 20 kgf / mm ² or less, high hardness, high toughness sintered body according to claim 2 which is. 4. The coating binder is a cubic boron nitride which is an intermetallic compound of at least one selected from the group consisting of Ti, Zr and Hf and Al, and a binder powder other than the coating binder. The high hardness and high toughness sintered body according to claim 1, wherein at least one selected from the group consisting of Al, Co, Ni, W and WC is sintered while infiltrating. 5. The high-pressure phase-type boron nitride is cubic boron nitride, and the coating binder is an intermetallic compound of at least one selected from the group consisting of Ti, Zr and Hf and Al, The binder powder is TiN, ZrN, HfN, TiC,
ZrC, HfC, TiAlN and solid solutions thereof,
The high-hardness and high-toughness sintered body according to claim 1, comprising at least one selected from the group consisting of Al and an Al compound.