JPH0432034B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a novel metal boride-based ceramic sintered body having a high density and suitable as a cutting tool material, particularly a cutting tool for woodworking and a wear-resistant material. <Prior art> Until now, tungsten carbide has been mainly used as a material for cutting tools, but as there has been a recent tendency for raw materials to be in short supply, metal borides, such as diboride, have been used as an alternative material. Titanium sintered bodies are beginning to attract attention. Incidentally, this metal boride sintered body has excellent heat resistance, oxidation resistance, strength and hardness at high temperatures, and is easily available in terms of resources. However, it has the disadvantage of low flexural strength. In order to improve the sinterability and bending strength of such a metal boride sintered body, the present inventors proposed that various binders be added to the metal boride sintered body (Japanese Patent Publication No. 56
-41690 Publication, Japanese Patent Publication No. 56-45984, Japanese Patent Publication No. Sho
54-72779, JP 56-23246, JP 56-32379) Each achieved some degree of effectiveness, but research continued to further improve heat resistance, hardness, and bending strength. Ti, Cr, V, Ta, Nb, Mn,
The basic components are at least one selected from monoborides and diborides of metals such as Mo, Hf, Al, and Zr, and at least one metal compound for a binder, and metal carbides and metal nitrides are used as basic components. It was discovered that sintered products containing additives selected from among materials exhibited even better physical properties (Japanese Patent Laid-Open No. 57-42578).
Publication No.). Although this material exhibits satisfactory physical properties as a wear-resistant tool, it lacks toughness and cannot be said to be satisfactory as a woodworking cutting tool. Therefore, we developed ceramics to which titanium carbonitride was added (Japanese Patent Application Laid-Open No. 61-97169). However, it is necessary to further improve impact resistance and expand its use as a cutting tool for a wide range of materials. <Problems to be Solved by the Invention> An object of the present invention is to provide metal boride-based ceramics having impact resistance that can be widely used as cutting tools and wear-resistant tools. <Means for solving the problem> The present inventors have conducted extensive research in order to impart impact resistance to metal boride ceramics, and have found that in order to improve impact resistance, it is possible to improve impact resistance by simply increasing toughness. It was discovered that large grains and pores that cause defects must be removed. Therefore, an attempt was made to obtain a sintered body by producing a fine-grained metal boride powder raw material, but the fine-grained metal boride powder is easily oxidized and has more pores, making it difficult to improve impact resistance that much. I couldn't do it. Therefore, we searched for an additive that had an oxygen removal effect, and found that carbides and carbonitrides had this effect, and that double carbides and double carbonitrides had a remarkable oxygen removal effect, and they improved their impact resistance. It was confirmed that this can also be improved by removing oxygen, leading to the present invention. That is, the present invention includes (A) one or more of MB ₂ , MB, M ₂ B type ₅ borides (M represents a metal) and (B) cobalt boride, nickel boride, or boron as a metal compound for the binder. The basic component is a mixture of at least one kind of iron oxides, and further contains (C)Ti, Zr, Hf, double carbide consisting of W and carbon, and nitrogen.
Carbonitrides and double carbonitrides other than TiCN relative to the total amount
This relates to a high-density metal boride ceramic sintered body made of a sintered body of a mixture to which 0.1% to 10% by weight has been added. Component (A), which is the main component of the present invention, includes TiB ₂ , ZrB ₂ ,
_CrB2 , _VB2 , _TaB2 , _NbB2 , _MnB2 , _MoB2 ,
Metal diborides such as HfB ₂ , YB ₂ , AlB ₂ , MgB ₂ , ZrB ₂ , CrB, VB, ZrB, TaB, NbB,
It is a metal boride selected from metal monoborides such as MoB, HfB, YB, AlB, and MgB, and metal pentaborides such as W ₂ B ₅ and Mo ₂ B ₅ . These may be used alone or in combination of two or more. Next, the metal compound for the binder used as component (B) is one that has been commonly used as a binder for conventional metal boride-based sintered bodies, such as
Cobalt boride, like CoB, _Co2B , _Co3B
These include nickel borides such as NiB, Ni ₂ B, Ni ₃ B, and Ni ₄ B ₃ , and iron borides such as FeB and Fe ₂ B. These may be used alone or in combination of two or more. It may also be used. The amount of the metal compound for binder added is selected in the range of 0.1 to 10% by weight based on the total amount of the raw material composition.
If this amount is less than 0.1% by weight, it will not be sufficiently densified, and if it exceeds 10% by weight, the ceramic surface will sweat during sintering, so there is no point in adding any more. In the present invention, it is necessary to add one or more types of double carbides, carbonitrides, and double carbides to the basic component consisting of the components (A) and (B) described above. These double carbides include Ti, Zr, Hf, W and C.
It is a double carbide consisting of and the atomic ratio of the two metals is in the range of 1:9 to 9:1. Also, as double carbides, Ti, Zr, Hf, C and N
The atomic ratio of the two metals is in the range of 1:9 to 9:1, and the carbon to nitrogen atomic ratio C/N is 1/9 to 9. It will be done. If a material with an atomic ratio C/N of 1/9 or less is used, it will be the same as a double nitride. Moreover, when it is 9 or more, it becomes a double carbide, and the effect of addition is the same as that of a double carbide. Furthermore, the two metals having the metal atomic ratio M ₁ /M ₂ preferably have an atomic ratio in the range of 1/9 to 9. Further, the carbonitride is a carbonitride of Zr or Hf, and the atomic ratio C/N of carbon to nitrogen is preferably in the range of 1/9 to 9. Outside this range, the effect is similar to that of adding carbides or nitrides. For the ceramics of the present invention, it is preferable to use raw materials obtained by classifying each of the above-mentioned components into average particle sizes of 4 μm or less, preferably 2 μm or less. Further, as for the production method, the mixture of these raw material powders can be produced by the hitherto known hot pressing method, ordinary sintering method, or hot isostatic pressure sintering method. For example, fill a mold with a raw powder mixture and
It is cold compressed using a press pressure of about 10 ton/cm ² , and then further molded using a rubber press using a hydrostatic pressure of about 0.5 to 10 ton/cm ² . Of course, it may be molded using either one, or may be molded by a slurry method. Next, the green compact obtained in this way is heated to 1300 to 2000 in a vacuum or in a neutral or reducing atmosphere such as argon, hydrogen, or carbon dioxide gas.
Sinter at a temperature of 1400-1700°C for 30-300 minutes. Further, if necessary, sintering is performed by hot isostatic sintering at 1200 to 1700° C. for 5 to 300 minutes under a pressure of about 2 tons/cm ² or less using argon gas or the like. At this time, the normal sintering step can be omitted by placing the green compact in a metal can. After filling the raw material powder mixture into a mold such as a graphite mold, it is heated at a die pressure of 50 to 300 Kg/cm ² and a temperature of 1300 in a vacuum or in a neutral or reducing atmosphere such as argon, hydrogen, or carbon dioxide gas. ~2000℃,
Sintering can also be carried out using a so-called hot press method, in which the material is heated and sintered preferably at a temperature of 1400 to 1700°C for 10 to 200 minutes. In this way, a metal boride-based ceramic sintered body suitable for various cutting tools can be obtained. <Example> Finely ground TiB ₂ , TaB ₂ , CoB,
(Ta ₈ Hf ₂ )C powder was classified to a particle size of 4 μm or less using a classifier to obtain a raw material powder. 91% of such raw materials
TiB ₂ -6% TaB ₂ -1% CoB - 2% (Ti ₈ Hf ₂ )C
They were mixed at a composition ratio of However, the ratio is a weight ratio.
Such raw material powder was filled into a graphite die, and heated and sintered at 1500° C. for 60 minutes in a vacuum under a hot press pressure of 200 kg/cm ² . The porosity of the obtained sintered body is
It had a toughness of 4 MPam ^1/2 and a hardness of 2400 Hv. This example is shown in No. 4 of Table 1. Similar experiments were also conducted with other compositions.
The results are shown in Table 1. However, 1*, 9*, 10*
is shown as a comparative example.

【table】

[Table] * Comparative Example <Effects of the Invention> According to the present invention, a porosity-free metal boride ceramic sintered body made from fine powder can be obtained, which can be used as cutting tools and wear-resistant members with excellent impact resistance. be able to.

Claims (1)

[Claims] 1 (A) TiB ₂ , ZrB ₂ , CrB ₂ , HfB ₂ , VB ₂ ,
TaB ₂ , NbB ₂ , MnB ₂ , MoB ₂ , YB ₂ , AlB ₂ ,
_MgB2 , CrB, VB, TaB, NbB, MoB, HfB,
YB, ZrB, HfB, TiB, MnB, W ₂ B ₅ and
At least one species selected from Mo ₂ B ₅ , and (B)
The basic component is at least one of cobalt boride, nickel boride, and iron boride as a metal compound for a binder, and (C) Ti, Zr, Hf, a double carbide consisting of W and C, or Ti, A high-density metal boride base consisting of a sintered body of a mixture to which one or more carbonitrides or double carbonitrides other than TiCN consisting of Zr, Hf, C, and N are added in an amount of 0.1% to 10% by weight based on the total amount. Ceramics sintered body.