JPH05186272A - Sintered boron nitride having composite high-density phase - Google Patents

Abstract

PURPOSE:To enable a sintering process by hot-pressing or a hot hydrostatic treatment without using an ultrahigh-pressure press and to provide a sintered boron nitride containing composite high-density phase, having improved abrasion resistance, chipping resistance, toughness and impact resistance and producible at a low cost. CONSTITUTION:The objective sintered material contains >=10vol.% of a composite hard phase consisting of hard phase particles of cubic boron nitride and/or wurtzite-type boron nitride surface-coated with the 1st layer having mono or multilayer structure of at least one kind of material selected from nitride or boride of Ti, Zr, Hf, Al and Si or their solid solution and the 2nd layer having mono or multilayer structure of at least one kind of material selected from carbide, nitride, carbonate, oxynitride or boride of the group 4a, 5a or 6a metal of the periodic table or their solid solution. Each of the 1st and the 2nd layer has an average layer thickness of >=5Angstrom .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite high density phase boron nitride firing suitable for a cutting tool represented by a turning tool, a milling tool, a drill, an end mill or the like, or a wear resistant tool represented by a die, a cutting blade or the like. Regarding union.

[0002]

2. Description of the Related Art Cubic boron nitride and wurtzite boron nitride are called high-density phase boron nitride because they have a higher density than hexagonal boron nitride. An ultrahigh pressure sintered material obtained by sintering at a high pressure and a high temperature by interposing a binder phase of metal and / or ceramics in this high-density phase boron nitride has been put into practical use. Conventionally used ultra-high pressure sintered materials are mainly wear resistant, toughness, strength and thermal shock resistance by adjusting the ratio of hard phase to binder phase of high density phase boron nitride or the material of binder phase. Are being studied.

However, this conventional ultra-high pressure sintered material is a mixture of hard phase powder and binder phase powder, and therefore, between binder phase particles, between hard phase particles, and between hard phase particles and binder phase. The bond at the grain boundary of the particle becomes insufficient, and the incomplete bond is likely to remain as a defect.
Adjust the ratio of hard phase and binder phase, or the material of binder phase,
There is a problem that if the wear resistance is increased, the toughness, strength, or thermal shock resistance is lowered, and conversely, if the toughness, strength, or thermal shock resistance is increased, the wear resistance is decreased. A typical one proposed as a solution to this problem is Japanese Patent Laid-Open No. 58-58247.
JP-A-58-60678 and JP-A-58-612.
There is a 53 publication.

[0004]

Problems to be Solved by the Invention JP-A-58-58247
Japanese Patent Laid-Open Publication No. Heisei 7-27242 discloses that cubic boron nitride has a composition containing a binder phase composed of at least one boride of Ti, Hf, Zr and Mo and a carbide and has an average layer thickness of 0.1 to 2 μm. A high toughness boron nitride based ultra high pressure sintered material for cutting and wear resistant tools is described in which the boride has a structure surrounding cubic boron nitride.

Further, Japanese Patent Application Laid-Open No. 58-60678 discloses that cubic boron nitride has a composition containing a binder phase composed of one or more nitrides of Ti, Hf and Si and a carbide, and 0.1%. A high toughness boron nitride based ultra high pressure sintered material for cutting and wear resistant tools is described in which the nitride having an average layer thickness of ˜2 μm has a structure surrounding cubic boron nitride.

Further, Japanese Patent Application Laid-Open No. 58-61253 discloses that cubic boron nitride has a composition containing Al and one or two kinds of Al oxides and nitrides, and has a composition of 0.1-1.
High toughness boron nitride base for cutting and wear resistant tools having a structure in which Al having an average layer thickness of μm or Al and one or two of Al oxide and nitride are surrounded by cubic boron nitride. Ultra high pressure sintered materials are described.

The ultra-high pressure sintered materials described in these publications are the same as those used in conventional ultra-high pressure sintered materials.
Micropores and unbonded defects that existed between the binder phase particles and at the grain boundaries between the hard phase particles and the binder phase particles are eliminated by the coating that surrounds the cubic boron nitride, and has both wear resistance and toughness, and cutting. Has excellent fracture resistance even in tests,
In addition, it has high hardness and excellent heat resistance and high temperature strength. However, the ultra-high pressure sintered materials described in these publications are sintered by using an ultra-high pressure apparatus at a pressure of 40 kb or more and a temperature of 1200 ° C. or more, as in the prior art, and thus it is difficult to mass-produce them. That is, there is a problem that it is difficult to manufacture a large-sized product, and that the manufacturing cost is high, and in terms of material, the film thickness and the film material easily cause defects in the film, and Defects tend to occur at the interface between the coating and other binder phases other than the coating, or at the interface between the coating and the coating, and the manufacturing cost is increased by adding the coating formation process, but the life is not improved. There is a problem.

The present invention solves the above-mentioned problems, and more specifically, hot pressing (HP) is applied to the surface of hard phase particles made of cubic boron nitride and / or wurtzite type boron nitride. ) Or hot isostatic pressure (HIP) treatment conditions to form a coating that prevents the hard phase from being converted back into hexagonal boron nitride, and to prevent defects caused by the coating, resulting in wear resistance and chipping resistance. An object of the present invention is to provide a composite high-density phase boron nitride sintered body having improved toughness, toughness, and impact resistance.

[0009]

DISCLOSURE OF THE INVENTION The present inventors have found that a dense phase boron nitride firing consisting of a hard phase made of cubic boron nitride and / or wurtzite type boron nitride and a binder phase of metal and / or ceramics. As a result of studying the low cost of the aggregate and the improvement of various properties, if a film quality and a film thickness are selected on the particle surface of the high-density phase boron nitride and a dense film is formed, H
It was found that under P or HIP treatment conditions, reverse conversion of high-density phase boron nitride to hexagonal boron nitride is less likely to occur, and that various properties of the obtained sintered body are improved by controlling the film thickness. .. The present invention has been completed based on this finding.

In the composite high-density phase boron nitride sintered body of the present invention, the grain surface of the hard phase of cubic boron nitride and / or wurtzite type boron nitride is nitride of Ti, Zr, Hf, Al, Si, or boron. A single layer or a multi-layer first layer of at least one of these compounds and their mutual solid solutions, and a carbide, nitride of a metal of group 4a, 5a, 6a of the periodic table on the surface of the first layer,
Carbonates, oxynitrides, borides and aluminum oxides,
Aluminum oxynitride and their mutual solid solutions (however,
Ti, Zr, Hf nitrides, borides, and mutual solid solutions thereof are excluded. 10) a composite hard phase surrounded by a coating consisting of at least one monolayer or a multi-layered second layer in 10).
A sintered body containing at least volume% is characterized in that the first layer and the second layer each have an average layer thickness of 5Å or more.

The first layer and the second layer in the sintered body of the present invention are
Specifically, for example, TiN, ZrN, HfN, AlN, Si
₃N_Four, TiB₂, ZrB₂, HfB₂, Al B₂, Al
B₁₂, Ti (B, N), Zr (B, N), Hf (B,
N), Al (B, N), (Ti, Zr) N, (Ti, Z
r, Hf) N, (Ti, Al) N, (Ti, Al)
(B, N) and (Al, Si) N can be mentioned.
If the first layer has an average layer thickness of less than 5Å, the hard phase
The effect of suppressing the reverse conversion to tetragonal boron nitride is reduced,
And the adhesiveness of the second layer surrounded by the surface of the first layer is poor.
In particular, when the first layer has an average layer thickness of 50 to 1000Å,
The above-mentioned function of suppressing the reverse transformation, the adhesion between the first layer and the second layer, and
And from the viewpoint of peeling resistance in the first layer.

The second layer surrounded by the surface of the first layer is specifically, for example, TiC, ZrC, HfC, V.
C, NbC, TaC, WC, Mo ₂ C, Cr ₃ C ₂ , V
N, NbN, TaN, CrN, Ti (C, N), Ti
(N, O), Ti (C, O), Ti (C, N, O),
(Ti, Ta) C, (Ti, Ta) (C, N), (T
i, V) (C, O), (Ti, Nb) (N, O), (T
i, Zr) (C, N, O), (Ti, W) C, (Ti,
W) (C, N), (Ti, Mo) (C, O), (Ti,
Mo) (C, N, O), Al ₂ O ₃ , Al (O, N),
(Al, Ti) (N, O) can be mentioned. When the second layer has an average layer thickness of less than 5Å, the fracture resistance and the oxidation resistance are lowered, and the effect of suppressing the reverse conversion of the hard phase to hexagonal boron nitride is lowered. In particular, when the second layer has an average layer thickness of 50 to 1000Å, it is preferable in terms of the above-described effect of suppressing the reverse conversion and the peeling resistance in the second layer.

The coating composed of the first layer and the second layer has an average layer thickness of 5 Å or more.
The case where the average layer thickness is 00Å to 2000Å is preferable for the above reason. In addition, this coating is preferable in that the composition components are changed from the surface of the hard phase particles toward the inside of the coating, that is, when the composition is a so-called gradient composition, the adhesion strength at the interface between the hard phase particles and the coating and at the grain boundaries in the coating becomes high, which is preferable. That is. Specifically, the gradient composition in the coating is, for example, a non-stoichiometric composition having a large content of B and / or N elements in the vicinity of the hard phase particle surface, and B toward the inside and the outside of the coating. And / or a non-stoichiometric composition containing a small amount of N element is particularly preferable from the viewpoint of the strength of the film.

The binder phase in the sintered body of the present invention is specifically, for example, TiC, ZrC, HfC, VC, NbC,
TaC, WC, Mo ₂ C, Cr ₃ C ₂ , SiC, TiN,
ZrN, VN, NbN, TaN, CrN, AlN, Si
₃ N ₄ , Fe ₃ C, TiO ₂ , Ta ₂ O ₅ , Al ₂ O ₃ , SiO
₂ , NiO, CoO, TiB ₂ , TaB ₂ , WB, Al
B ₂ , Y ₂ O ₃ , YN, Dy ₂ O ₃ , CeO, (Ti, Z
r) C, (Ti, Ta) C, (Ti, Ta, Nb) C,
(Ti, W) C, (Ti, Ta, W) C, Ti (C,
N), Ti (N, O), Ti (C, O), Ti (C,
N, O), (Si, Al) (O, N), Fe, Ni, C
o, (Fe, Ni) alloy, (Ni, Co) alloy, (F
e, Co) alloy and (Fe, Ni, Co) alloy. The binder phase is 10 to 75% by volume of the binder phase.
Is a whisker of at least one of 4a, 5a, 6a group metals of the periodic table, Ai, Si carbides, nitrides, oxides, borides and mutual solid solutions thereof.
Specifically, for example, TiC, ZrC, TaC, WC, S
iC, TiN, TaN, AlN, Si ₃ N ₄ , TiO ₂ ,
When the whiskers of Al ₂ O ₃ , TiB ₂ , AlB ₂ , and Ti (C, N) are used, the strength and toughness of the sintered body are increased, which is particularly preferable. When the whiskers contained in the sintered body have an average thickness of 0.003 to 3 μm, an average length of 0.01 to 300 μm, and an aspect ratio of 3 or more, the effect of suppressing crack propagation in the sintered body is high,
It is particularly preferable because a high toughness and high strength sintered body is easily obtained.

The sintered body of the present invention is coated on the surface of cubic boron nitride and / or wurtzite type boron nitride powder by, for example, chemical vapor deposition (CVD), physical vapor deposition (PVD) or wet plating. It can be produced by using the starting material having the above-mentioned structure and sintering it by hot pressing (HP) in a non-oxidizing atmosphere, hot isostatic pressing (HIP), or a conventional ultrahigh pressure apparatus. Further, in the case of a sintered body containing a binder phase, the substance of the binder phase and the above-mentioned film-formed boron nitride powder are treated by a conventional powder metallurgy method and sintered by the above method. It can be produced by

[0016]

In the sintered body of the present invention, the coating surrounding the surface of the hard phase acts to prevent the hard phase from being converted back into hexagonal boron nitride during the sintering process. It has the function of closely coupling each other. Further, in the case of the sintered body of the present invention containing a binder phase, 4a, 5a, 6a of the periodic table are used.
At least one binder phase among group metals, carbides, nitrides, oxides, borides of Al, Si, Fe, Ni, Co and their mutual solid solutions has high temperature chemical stability and wear resistance of the sintered body. Of the rare earth metal oxides and nitrides and at least one binder phase among the mutual solid solutions of these rare earth metals eliminates the micropores in the sintered body and makes the sintered body dense. The whiskers act to prevent crack propagation, and Co, Ni, and Fe act to improve toughness and strength.

[0017]

Example 1 Commercially available cubic boron nitride (C
BN) powder was used to coat the surface of the CBN powder with the coating shown in Table 1 by the conventional CVD treatment to produce a composite CBN powder. After the composite CBN powder was made into a powder compact, (the samples using the two kinds of composite CBN powders were well mixed) and sintered under the sintering conditions shown in Table 1 to obtain the products 1 to 3 of the present invention. Obtained.

For comparison, a composite CBN powder shown in Table 1 was prepared and sintered under the conditions shown in Table 1 to give a comparative product 1.
~ 3 was obtained.

Inventive products 1 to 3 and comparative product 1 thus obtained
The fracture toughness values of ~ 3 were measured, and the results are also shown in Table 1. In the column of film quality in Table 1, after coating the film of, the surface of was coated with the film of.

[0020]

[Table 1]

[0021]

Example 2 Composite C shown in Table 2 as in Example 1
BN powder was obtained. The composite CBN powders in Table 2 and the binder phase forming powders shown in Table 3 were added to obtain Products 4 to 6 of the present invention.

The compounding composition of the present invention product 4 is 52.03 vo
1% composite CBN powder and residual binder phase forming powder, the product 5 of the present invention is 65.57 vol% composite CBN powder and residual binder phase forming powder, product 6 of the present invention is 35.37 vol% composite CBN
The powder and the remaining binder phase forming powder were used. The compound of this composition was sintered under the sintering conditions shown in Table 4 to obtain the product 4 of the present invention.
~ 6 was obtained.

The products 4 to 6 of the present invention thus obtained and commercially available CB
Two types of N sintered body (ultra high pressure product) are used for comparison 4,
5, and the fracture toughness values of the respective samples were calculated and shown in Table 4.

[0024]

[Table 2]

[0025]

[Table 3]

[0026]

[Table 4]

[0027]

EFFECTS OF THE INVENTION A high-density phase boron nitride sintered body capable of being sintered by hot pressing or hot isostatic pressing, which is an effect that cost reduction can be achieved and a fracture toughness value of the sintered body. However, there is an effect that it is improved by about 27 to 102% as compared with the conventional high density phase boron nitride sintered body or the comparative sintered body deviated from the product of the present invention.

Claims (3)

[Claims] 1. The surface of particles of the hard phase of cubic boron nitride and / or wurtzite type boron nitride is Ti, Zr, Hf, A.
a single-layer or multi-layer first layer of at least one of N, Si nitrides, borides and mutual solid solutions thereof;
On the surface of the layer, carbides, nitrides, carbonates, oxynitrides, borides and aluminum oxides of group 4a, 5a and 6a metals of the periodic table, aluminum oxynitride and mutual solid solutions thereof (however, Ti, Zr, Hf are included). , Nitrides and borides thereof, and mutual solid solutions thereof), and a sintered body containing at least 10% by volume of a composite hard phase surrounded by a coating consisting of at least one single layer or a second layer of multiple layers in A composite high-density phase boron nitride sintered body, wherein the first layer and the second layer each have an average layer thickness of 5Å or more. 2. The surface of the particles of the hard phase of cubic boron nitride and / or wurtzite type boron nitride is Ti, Zr, Hf, A.
a single-layer or multi-layer first layer of at least one of N, Si nitrides, borides and mutual solid solutions thereof;
On the surface of the layer, carbides, nitrides, carbonates, oxynitrides, borides and aluminum oxides of groups 4a, 5a and 6a of the periodic table, aluminum oxynitride and their mutual solid solutions (however, Ti, Zr, Hf Of nitrides, borides, and mutual solid solutions thereof, except for 10% by volume or more of the composite hard phase surrounded by a film consisting of at least one single layer or a second layer of multiple layers in And an unavoidable impurity, wherein the first layer and the second layer each have an average layer thickness of 5Å or more, and the binder phase is a group 4a, 5a, 6a metal of the periodic table, Al, Si, Fe, Ni,
Co carbide, nitride, oxide, boride, rare earth metal oxide, nitride and mutual solid solution thereof, or Fe,
A composite high density phase boron nitride sintered body comprising at least one of Ni and Co. 3. In the binder phase, 10 to 75% by volume of the binder phase is 4a, 5a, 6a group metal, Al, Si of the periodic table.
3. The composite high density phase boron nitride sintered body according to claim 2, comprising at least one kind of whiskers among the carbides, nitrides, oxides, borides, and mutual solid solutions thereof.