JPH07822B2 - High density metal boride based ceramics - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel metal boride-based ceramic having a high density, which is suitable as a cutting tool material, particularly as a woodworking cutting tool and an abrasion resistant material.

2. Description of the Related Art Tungsten carbide has been mainly used as a cutting tool material up to now, but since there is a tendency for a shortage of raw materials recently, metal boride such as titanium diboride is used as an alternative material. Sintered bodies have come into the spotlight.

By the way, this metal boride sintered body is excellent in heat resistance, oxidation resistance, strength and hardness at high temperature, and is easily available in terms of resources. However, it has a difficulty in sinterability and a cutting tool. Has the drawback of low impact resistance.

For this reason, it has been proposed to mix metals such as Co, Ni, Fe, and Cu with borides in a relatively large amount of several tens wt% for the purpose of improving flame retardancy. JPA
51-30213), when such a large amount of metal is blended, the boride reacts with the metal and deteriorates, so that the desired impact-resistant ceramics cannot be obtained.

Further, the present inventors have previously proposed to add an iron group metal boride such as cobalt boride, nickel boride, and iron boride as a boride binder. (Japanese Patent Publication Sho 56-41690
JP-B-56-45984, JP-A-54-72779, JP-A-56-23246).

The ceramics thus obtained have impact resistance
Although some improvements have been made, they are not necessarily satisfactory yet. Therefore, a titanium carbonitride was further added to improve the toughness (JP-A-61-97169).
This publication also has insufficient impact resistance to limit the field of application, and the borides of Co, Fe, and Ni used as binders are expensive, and the resulting ceramics are costly. It has the disadvantage of being expensive.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention An object of the present invention is to provide an inexpensive and impact resistant metal boride ceramics which can be widely used as a cutting tool or an abrasion resistant tool.

Means for Solving the Problems The present inventors first conducted various experiments in order to find an inexpensive binder, but when a small amount of Co, Fe, and Ni were added, these metals and boride were burned. A reaction occurs at the time of conclusion,
For example, Co was changed to CoB, Co ₂ B, Co ₃ B, etc., but it was found that the hexagonal boride mainly composed of TiB ₂ remains in the hexagonal system. Therefore, inexpensive Co, Fe, Ni without using cobalt boride, nickel boride, or iron boride
It has been found that may be used. The amount of the iron group metal added is in the range of 0.1 to 5% by weight, more preferably 0.5 to 4% by weight.

Next, the present inventors have conducted intensive studies in order to impart impact resistance, but it has been found that impact resistance must not only enhance toughness but also remove defective large grains and pores. did. Therefore, we tried to obtain a sintered body by producing a finely divided metal boride powder raw material, but the finely divided metal boride powder is easy to oxidize, and rather, the number of pores increases and impact resistance is not significantly improved. could not. So I searched for an additive that has an oxygen-removing effect.
It was confirmed that carbides and carbonitrides have the effect, and that double carbides and carbonitrides have a remarkable oxygen removing effect, and it was confirmed that the impact resistance can be improved by removing oxygen, and thus the present invention is made. I arrived. That is, the present invention is
(A) The total weight of at least one selected from Co, Fe and Ni as the metal component for the binder (B) is the basic component of the metal boride composed mainly of TiB ₂ hexagonal boride. In an amount ranging from 0.1 to 5% by weight, and also (C) T
0.1 to 1 based on the total weight of at least one selected from among carbides, composite carbides, carbonitrides or composite carbonitrides of at least one metal selected from i, Hf, W and Zr.
The present invention provides a high-density metal boride-based ceramic comprising a sintered body of a mixture added in an amount in the range of 0% by weight.

Although TiB ₂ is used as the component (A) of the present invention, that is, the basic component, it is not always necessary to use TiB ₂ alone, and it is necessary to maintain its hexagonal structure even if a small amount is added to TiB _2. However, it may contain a metal boride which is commonly used in combination with TiB ₂ in ordinary impact resistant ceramics. Examples of such metal borides that can be used in combination with TiB ₂ include ZrB ₂ , CrB ₂ , VB ₂ , TaB ₂ , MbB ₂ , MnB ₂ and MoB.
₂ , metal diboride such as HfB ₂ , YB ₂ , AlB ₂ and MgB ₂ , Cr
Examples thereof include metal monoborides such as B, VB, ZrB, TaB, MbB, 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, as the binder metal used as the component (B), its boride has been conventionally used as a binder for metal boride-based sintered bodies, and there are Co, Fe and Ni. These may be used alone or in combination of two or more.

The amount of this binder metal added is based on the total amount of the raw material composition.
It is selected in the range of 0.1 to 5% by weight. If this amount is less than 0.1% by weight, it will not be sufficiently densified, and if it is 5% by weight or more, it will cause sweating on the ceramic surface during sintering, and it is meaningless to add more than this.

In the present invention, it is necessary to add at least one of carbide, double carbide, carbonitride, and double carbonitride to the basic component consisting of the above-mentioned component (A) and component (B).

This carbide includes Ti, Zr, and Hf carbides.

Further, the double carbide is Ti, Zr, Hf, and a double carbide composed of W and C.

The double carbonitride is a double carbonitride composed of Ti, Zr, Hf, C and N. Carbon / nitrogen atomic ratio C / N is 1/9 ~
9 is preferable. If the atomic ratio C / N is 9 or more, the same effect as double carbide is obtained. If it is less than 1/9, it becomes a double nitride and has no effect.

The carbonitrides are Zr, Hf, and Ti carbonitrides,
The atomic ratio C / N of carbon and nitrogen is preferably in the range of 1 / 9-9.
Within the range other than this range, the same effect as the addition of carbide or nitride is obtained.

The ceramics of the present invention, each of the above-mentioned components having an average particle size of 4 μm
It is preferable to use a raw material classified to m or less, preferably 2 μm or less. In addition, as a manufacturing method, a mixture of these raw material powders can be manufactured by a conventionally known hot pressing method, an ordinary sintered body, or a hot isostatic pressing method.

For example, the raw powder mixture is filled in a mold and 0.5-10 ton / c
It is cold-pressed by a press pressure of about m ² and then further formed by a rubber press with a hydrostatic pressure of about 0.5 to ¹⁰ ton / cm ² . Of course, either one may be molded, or the slurry method may be used. Next, the green compact obtained in this manner is vacuumed or in a neutral or reducing atmosphere such as argon, hydrogen or carbon dioxide gas at 1300-
Sintering is performed at a temperature of 2000 ° C., preferably 1400-1700 ° C. for 30-300 minutes. Further, if necessary, it is sintered by hot isostatic pressing at 1200 to 1700 ° C. for 5 to 300 minutes under a pressure of about ² ton / cm ² or less by argon gas or the like. On this occasion,
The normal sintering step can be omitted by placing the green compact in a metal can.

Further, according to another method, after filling the raw material powder mixture into a mold such as a graphite mold, in vacuum or in a neutral or reducing atmosphere such as argon, hydrogen, carbon dioxide gas, the die pressure 50 ~ 300 kg /. cm ² , temperature 1300-2000
C., preferably 1400 to 1700.degree. C., and sintered by using a so-called hot pressing method, which is heat sintering for 10 to 200 minutes.

In this way, metal boride-based ceramics suitable for various cutting tools can be obtained.

EXAMPLES Next, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 95% by weight of TiB _{2 and} 1% by weight of Co were classified into particles having a particle size of 4 μm or less.
After thoroughly mixing the powder mixture consisting of 4% by weight of TiCN and 4% by weight of TiCN with a mixer, the mixture was filled in a graphite mold and heated and sintered in a vacuum at a die pressure of 200 kg / cm ² and a temperature of 1600 ° C. for 60 minutes. Thus, the toughness value (K ₁ C) is 3.5MPa ^1/2 and the porosity is
A sintered body with 0.3 Vol% and hardness (Hv) of 2100 kg / mm ² was obtained.

Comparative Examples 1 to 5 Based on TiB ₂ , 5% by weight of TaB ₂ and 0 to 6% by weight of Ni were used as a raw material, and a mixture containing no carbide, complex carbide, carbonitride or complex carbonitride was used as a raw material. It was heated and sintered at a pressure of 200 kg / cm ² and a temperature of 1500 ° C. for 60 minutes. The physical properties of the thus obtained sintered body are shown in Table 1.

As is clear from this table, those lacking the component (C) or the component (B) and the component (C) have a large porosity and do not become dense.

Examples 2 to 5 and Comparative Example 6 A mixture of 6% by weight of TaB ₂ and 1% by weight of Co with respect to TiB ₂ and 0 to 6% by weight of TiCN was used as a raw material. 6 at pressure 200 kg / cm ² and temperature 1500 ° C
It was heated and sintered for 0 minutes. The physical properties of the thus obtained sintered body are shown in Table 2.

As is clear from this table, those which do not contain the component (C) have a large porosity and a low density.

Examples 6 to 15 Table 3 shows the physical properties of sintered bodies obtained by sintering the raw materials having the compositions shown in Table 3 under the same sintering conditions as in Examples 2 to 5.

EFFECTS OF THE INVENTION According to the present invention, pore-free metal boride-based ceramics obtained from fine powder can be obtained, and can be used as a cutting tool material or wear resistant material that is inexpensive and has excellent impact resistance.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ichihisa Ibuhisa 807 Nonoshita, Toji City, Tosu City, Saga Prefecture 1 Inside Kyushu Industrial Technology Laboratory (72) Inventor Yukio Kai 1-3, Asmuta Town, Omuta City, Fukuoka Prefecture (56) References JP-A-60-165340 (JP, A) JP-B-61-50909 (JP, B2)

Claims (1)

[Claims] 1. At least one selected from Co, Fe and Ni as a metal component for a binder (B) with respect to (A) a metal boride basic component consisting of a hexagonal boride mainly composed of TiB _2. One in an amount ranging from 0.1 to 5% by weight, based on total weight,
Further, (C) at least one kind of carbide, compound carbide, carbonitride or compound carbonitride of at least one metal selected from Ti, Hf, W and Zr is 0.1 to 10% by weight based on the total weight. High density metal boride based ceramics consisting of a sintered body of a mixture added in an amount in the range of.