JP3132843B2 - High toughness high pressure phase boron nitride sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-toughness high-pressure phase boron nitride-based sintered body which is most suitable as a cutting tool such as a turning tool, a milling tool, a drill or a wear-resistant tool such as a die.

[0002]

2. Description of the Related Art Conventionally, cubic boron nitride (hereinafter, referred to as CBN) or wurtzite-type boron nitride (hereinafter, referred to as CBN) having low affinity with iron-based materials has been used for cutting hardened high-hardness steel and the like. , WBN) are in practical use.

[0003] This high-pressure phase boron nitride sintered body is a sintered body in which a binder phase is interposed at the grain boundaries of a hard phase made of high-pressure phase boron nitride such as CBN and / or WBN. , Cermet-based materials, and ceramic-based materials.

[0004] These conventional high-pressure phase boron nitride sintered bodies are:
The starting material consisting of the high-pressure phase boron nitride and the bonding phase-forming substance is simply physically mixed and sintered as it is at a high pressure and high temperature. However, there is a problem that the sintered body is inferior, the toughness of the sintered body is low, and the sintered body is easily broken.

[0005] Representative examples of solutions proposed to solve this problem include JP-A-58-58247, JP-A-58-60678, and JP-A-61-14.
No. 6763 and a summary of high-pressure debates (November 2, 1990, 2A12).

[0006]

Among the conventional high-pressure phase boron nitride sintered bodies, Japanese Patent Application Laid-Open No. 58-58247 discloses that cubic boron nitride contains at least one kind of boron selected from Ti, Hf, Zr and Mo. A high-pressure phase boron nitride sintered body having a structure surrounded by an average layer thickness of 0.1 to 2 μm made of a nitride is disclosed. Japanese Patent Application Laid-Open No. 58-60678 discloses cubic boron nitride containing Ti,
0.1 to 2 made of at least one kind of nitride of Hf and Si
A high-pressure phase boron nitride sintered body having a structure surrounded by an average layer thickness of μm is disclosed.

In the high-pressure phase boron nitride sintered bodies disclosed in both of these publications, small voids due to insufficient wraparound of the binder phase into the recesses on the surface of the particles of CBN are formed by CB.
It solves the problem of being formed at the grain boundary of N, and in the case of a binder phase of a carbide-based ceramic, a part where the bonding strength is weakly formed partially between the CBN and the binder phase. The boride or nitride layer surrounding the CBN particles is formed by chemical vapor deposition (CVD) or physical vapor deposition (PVD)
Is formed, the adhesion strength with CBN particles is weak,
It is difficult to form a film having a uniform thickness on the surface of fine CBN because the effect of peeling during mixing and pulverization and enhancing the toughness is low, and even if a film is formed, the film and the CBN particles are not coagulated. There is a problem that it is difficult to form a uniform structure as a mass.

Further, Japanese Patent Application Laid-Open No. 61-146,763 discloses that TiC or T
A method for producing a high-pressure phase boron nitride sintered body in which i (C, N) is wrapped around CBN particles and other binder phase particles to form a reaction region layer free of Al at the interface of the CBN particles. It has been disclosed that the high pressure debate summary on November 2, 1990 includes AlN-Ti inside around the CBN particles.
A high-pressure phase boron nitride sintered body in which a reaction layer having an N layer and a TiB ₂ layer on the outside is formed is disclosed.

[0009] The high-pressure phase boron nitride sintered body disclosed in this publication and in the outlines can be obtained by adding CVD or PVD to CBN particles as a starting material.
Instead of forming a film by the method, a reaction layer is formed with a binder phase that can easily react with CBN particles during sintering at ultra-high pressure and high temperature, and the toughness and wear resistance are improved. There is a problem that the reaction between the CBN particles and the binder phase is weak, and the adhesion strength between the CBN particles and the reaction layer is not yet sufficient and the toughness has not been significantly increased.

The present invention has solved the above-mentioned problems. Specifically, a hard phase of high-pressure phase boron nitride and a binding phase-forming substance are reacted and sintered to form particles on the surface of the hard phase. It is an object of the present invention to provide a high-pressure phase boron nitride sintered body having a high toughness and excellent fracture resistance, in which a different reaction layer comprising a hard phase and a binder phase forming substance is formed.

[0011]

Means for Solving the Problems The inventors of the present invention aimed at stabilizing the tool life when using a high-pressure phase boron nitride sintered body as a cutting tool and expanding the range of use of the sintered body. While studying to improve toughness,
In addition, when CBN is reacted with a binder phase forming substance that becomes a binder phase after sintering, the fracture resistance is improved, but the effect differs depending on the magnitude of the reaction between the two and the substance generated by the reaction. I learned that it would come.

Secondly, in order to make CBN and the binder phase forming substance more actively react, the surfaces of the starting materials, in particular, CBN and the binder phase forming substance involved in the reaction are activated, and during sintering, mutual interaction occurs. To make the reaction active, so that micropores do not occur at the intergranular boundaries of CBN and the binder phase,
It becomes denser and can form an optimal reaction layer on the surface of CBN. This reaction layer acts as a mediator to increase the adhesion between CBN and the binder phase, and the strength and toughness of the obtained sintered body Was found to significantly increase the

The present invention has been completed based on the first and second findings described above.

That is, the high-toughness high-pressure phase boron nitride sintered body of the present invention comprises 25 to 90% by volume of cubic boron nitride and / or
Alternatively, in a high-pressure phase boron nitride sintered body in which wurtzite-type boron nitride is used as a hard phase and the remaining binder phase is mainly composed of ceramics, the entire surface of the particles of the hard phase includes boronitride and boron containing Ti. A first material comprising at least one of carbide, borate, boronitride, boronitride, borocarbonate, and boronitride
A boronitride, a borocarbide, a boride, a boronitride, a boronitride, a borocarbonate containing Al on the surface of the first layer;
A second layer comprising at least one kind of borocarbonitride is formed.

Specifically, the binder phase in the present invention is, for example, carbides, nitrides, oxides, borides, silicides of metals belonging to groups 4a, 5a and 6a of the periodic table and their mutual solid solutions, Si, At least one kind of ceramics among Al carbides, nitrides, oxides, borides, and their mutual solid solutions, or the ceramics having a periodic table 4a, 5a, 6
At least one of Group A metals, Co, Ni, and Fe contains 10% or less of the binder phase.

The binder phase comprises at least one of Ti carbides, carbonates, nitrides, nitrides, borides and their mutual solid solutions, and Al nitrides, nitrocarbides, oxides,
When it is composed of boride and at least one of these mutual solid solutions, the denseness of the composite boron nitride in which the first layer and the second layer are formed on the surface of the particles of high-pressure phase boron nitride is also increased. This is particularly preferred.

The composite boron nitride according to the present invention has a structure in which the entire surface or a part of the surface of the hard phase particles is surrounded by a first layer, and the entire surface or a part of the surface of the first layer is surrounded by a second layer. It has become. The first component constituting the peripheral portion of the composite boron nitride
The layer and the second layer are formed, in particular, by the reaction between the high-pressure phase boron nitride constituting the core and the binder phase, and the degree of the reaction is increased to roughen the particle surface of the hard phase of the core. Is preferable.

Of these, the first layer is, for example, T
i (B, N), Ti (B, C), Ti (B, O), Ti
(B, N, O), Ti (B, N, C), Ti (B, N,
O), Ti (B, N, C, O), (Ti, M) (B,
N), (Ti, M) (B, C), (Ti, M) (B,
O), (Ti, M) (B, N, C), (Ti, M)
(B, N, O), (Ti, M) (B, C, O), (T
i, M) (B, N, C, O). The first layer is particularly preferably made of boronitride, boronitride, boronitride, or boronitride in order to make the core firmly adhere to the hard phase and make it denser.

The second layer is made of, for example, Al
(B, N), Al (B, C), Al (B, O), Al
(B, N, O), Al (B, N, C), Al (B, C,
O), Al (B, N, C, O), (Al, M) (B,
N), (Al, M) (B, C), (Al, M) (B,
O), (Al, M) (B, N, O), (Al, M)
(B, N, C), (Al, M) (B, C, O), (A
1, M) (B, N, C, O).
(However, M in the chemical composition formulas exemplified for the first layer and the second layer represents a metal element or a metalloid element of ceramics constituting the bonding phase, and specifically, for example, Zr, Hf,
V, Nb, Ta, Cr, Mo, W, and Si. The first component constituting the composite boron nitride with the above binder phase
The layer and the second layer have respective optimum combinations, and in particular, the carbide, carbonate, nitride, nitride oxide,
The first layer is composed of at least one of borides and their mutual solid solutions, and at least one of nitrides, nitrocarbides, oxides, borides of Al and their mutual solid solutions; Wherein the second layer is at least one of Al boronitride, boronitride, and boronitride, and the second layer is at least one of Al boronitride, boronitride, and boronitride. In this case, the effect of increasing the toughness and fracture resistance of the sintered body is remarkable and preferable.

When the hard phase in the present invention exceeds 90% by volume, the binder phase becomes relatively less than 10% by volume, and even if the composition components of the first layer and the second layer are selected, sintering may be performed. The effect of increasing the strength and toughness of the body is difficult to exert. Conversely, if it is less than 25% by volume, the high hardness of the hard phase cannot be fully utilized, and the reduction in wear resistance of the sintered body becomes remarkable.

The high-toughness high-pressure phase boron nitride sintered body of the present invention was produced.
In order to manufacture, the powder of high pressure phase boron nitride as a starting material
For example, the first layer and the like are formed on the surface by physical vapor deposition or chemical vapor deposition.
And the precursor of the first and second layers
After the coating has been formed, this starting material and other
Can be obtained by mixing, molding and high-pressure and high-temperature sintering.
However, in the starting material, an intermetallic compound such as Ti A
l_Three, Ti Al, Ti_TwoAlN, Ti_TwoContains AlCN
And perform the mixing and forming steps in a non-oxidizing gas atmosphere.
In the high pressure and high temperature sintering process, intermetallic compounds and high pressure phase nitriding
Reacting and sintering boron to form a first layer and a second layer
Preferably.

Specifically, the reaction during the reaction sintering is, for example, to decompose an intermetallic compound into Ti and Al, of which Ti having excellent wettability with high-pressure phase boron nitride reacts with high-pressure phase boron nitride. To form a first layer, and then a part of the first layer reacts with Al to form a second layer.

The thicknesses of the first and second layers can be adjusted by the contents of the components necessary for forming the first and second layers, the sintering temperature, and the particle size of the starting material. It is possible, the higher the content, the higher the sintering temperature, the thicker the layer thickness, these layer thicknesses each being 2
μm or less, and the total thickness of the first layer and the second layer is 0.1
Preferably, the thickness is reduced to 3.0 μm, the thickness is preferably reduced from the viewpoint of manufacturing cost, the thickness is increased to a certain level from the viewpoint of the strength of the sintered body, and from another viewpoint, the surface of the CBN is rough. It is preferable that the total thickness of the first layer and the second layer is 0.1 to 1.0 μm.

With respect to this preferred production method, the filing date of the present inventors is described in detail in the specification of the patent application filed on March 1, 1991.

[0025]

In the high-toughness high-pressure phase boron nitride sintered body of the present invention, the first layer and the second layer constituting the composite boron nitride are a medium for densely fixing the high-pressure phase boron nitride in the core and the binder phase. Wherein the first layer is formed in a state where the first layer interacts particularly with the surface of the high-pressure phase boron nitride in the core portion, and the surface of the high-pressure phase boron nitride is roughened. When one layer is densely inserted, the fixing strength is further increased.

[0026]

Example 1 Starting materials comprising various binder phase forming substances having an average particle diameter of 2 to 4 μm were mixed and pulverized by a ball mill in an argon atmosphere having an oxygen concentration of 20 ppm or less until the respective average particle diameters became submicron or less. And an average particle size of 2
CBN of 10 μm to 10 μm was additionally mixed to obtain each mixed powder of the composition components shown in Table 1.

Next, in the same atmosphere, WC-8% by weight Co powder was inserted into a mold so as to have a predetermined thickness, and then the above-mentioned mixed powders were subjected to transfer embossing to form a composite compact. After degreasing and heating under vacuum of 1 × 10 ⁻⁶ Torr and 900 ° C., the mixture was set in a belt-type ultrahigh-pressure high-temperature apparatus and sintered under the conditions of 6.0 GPa, 1600 ° C. and 30 minutes. A composite sintered body composed of articles 1 to 5 and a cemented carbide was produced.

As a comparison, a composite sintered body consisting of comparative products 1 to 3 and a cemented carbide was subjected to mixing and pulverization in air, compaction molding, heating for degreasing and sintering at an ultra-high pressure and high temperature as in the past. Was prepared.

[0029]

[Table 1] The products 1 to 5 of the present invention and the comparative products 1 to 3 thus obtained were examined by a scanning electron microscope and micro-Auger analysis, and the fracture toughness value due to cracks was determined.
It was shown to.

[0030]

[Table 2]

[0031]

Example 2 Using the composite sintered bodies of the products 1 to 5 of the present invention and the comparative products 1 to 3 obtained in Example 1, an SNGN432 shape (with a honing of 0.1 × -25 °) and a work material SKD11 were used. Milling with a hardened surface (HRC62), work surface 50W × 200 lmm, cutter MD1006, single blade, and the average flank wear amount up to chipping or at the time of 2,000 m cutting were obtained, and the results are shown in Table 3. Was.

[0032]

[Table 3]

[0033]

As described above, the high-toughness high-pressure phase boron nitride sintered body of the present invention is a comparative product 1 in which a reaction layer is formed on the surface of CBN or a comparative product 2 in which a reaction layer cannot be confirmed, as in the prior art.
Compared with No. 3, there is an effect that the fracture toughness value is improved by about 42 to 163% and the fracture resistance in the cutting test is improved by about 4.9 to 15.4 times.

[Brief description of the drawings]

FIG. 1 shows the particle structure of the composite boron nitride of the product 1 of the present invention obtained in Example 1,

2 is a particle structure of a composite boron nitride obtained by enlarging FIG. 1;

FIG. 3 shows a particle structure of a composite boron nitride of Comparative Example 3 obtained in Example 1.

Claims (4)

(57) [Claims] 1. A high-pressure phase boron nitride sintered body in which 25 to 90% by volume of cubic boron nitride and / or wurtzite-type boron nitride is used as a hard phase and the remaining binder phase is mainly composed of ceramics. A first layer made of at least one of Ti-containing boronitride, borocarbide, borate, boronitride, boronitride, borocarbonate, and boronitride on the surface of the hard phase particle;
Boronitride, borocarbide containing Al on the entire surface of the first layer,
A high-toughness high-pressure phase boron nitride sintered body characterized in that a second layer comprising at least one of boron oxide, boronitride oxide, boronitride carbide, borocarbonate, and borocarbonitride is formed. 2. The method according to claim 1, wherein the binder phase is Ti carbide, carbonate,
At least one of nitrides, nitrides, borides and their mutual solid solutions, and at least one of Al nitrides, nitrocarbides, oxides, borides and their mutual solid solutions;
The high-toughness high-pressure phase boron nitride sintered body according to claim 1, wherein the sintered body is a seed. 3. The method according to claim 1, wherein the first layer is made of at least one of boronitride, boronitride and boronitride of Ti, and the second layer is made of boronitride, boronitride and boronitride of Al. The high-toughness high-pressure phase boron nitride sintered body according to claim 1, wherein the sintered body is made of at least one of the following. 4. The total thickness of the first layer and the second layer is 0.
2. The high-toughness high-pressure phase boron nitride sintered body according to claim 1, wherein the thickness is 1 to 3.0 [mu] m.