JPH03193668A - Production of cubic boron nitride ceramic material having high toughness - Google Patents

Abstract

PURPOSE:To obtain cubic boron nitride ceramic material having high toughness by heating the green compact of the mixture of titanium hydride and cubic boron nitride powder in vacuum and allowing both to react with each other and treating a porous sintered body wherein titanium nitride and titanium boride are strongly bonded to cubic boron nitride at ultrahigh pressure and high temp. CONSTITUTION:The mixture of 0.5-20wt.% titanium hydride powder (TiHx, mean particle diameter is less than 1mum) and the balance cubic boron nitride powder (c-BN, mean particle diameter is 1-10mum) is molded into a green compact. Thereafter, this green compact is heated and held at 1200-500 deg.C in vacuum. TiHx is allowed to react with c-BN to produce TiN and TiB2. A porous c-BN- based ceramic sintered body having a structure is obtained wherein TiN and TiB2 are strongly bonded to c-BN. This sintered body is treated at the ultrahigh pressure and high temp. to make it dense at theoretical density ratio of at least 98%. Thereby the c-BN-based ceramic material having high toughness is obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention has high toughness and excellent wear resistance.
It is excellent when used as a cutting tool, not only for continuous cutting under normal conditions, but also for continuous high-speed cutting of cast iron where toughness is required, and interrupted cutting of high-hardness steel such as die steel and high-speed steel. The present invention relates to a method for manufacturing a cubic boron nitride (hereinafter referred to as c-BN)-based ceramic material that exhibits cutting performance over a long period of time.

[Conventional technology]

In general, c-BN-based ceramic materials have high hardness and are used as cutting tools.
For example, as described in Japanese Patent Publication No. 57-3811, the base ceramic material contains c-BN powder, c-BN powder,
as well as 4a and 5a of the periodic table.

Using carbide powder, nitride powder, boride powder, and silicide powder of group 6a metals, these raw material powders are blended into a predetermined composition and mixed under normal conditions to form a mixed powder state or a compacted powder. After being molded into a body, it is subjected to normal conditions, i.e. pressure of 10,000 atmospheres or more, temperature: 100
Theoretical density ratio:
It is also well known that it can be manufactured by forming a 98% or more dense sintered body.

[Problem to be solved by the invention]

However, when the c-BN-based ceramic material manufactured by the above-mentioned conventional method is used for continuous high-speed cutting of cast iron or interrupted cutting of the above-mentioned high-hardness steel, the cutting edge cracks due to lack of toughness. At present, cutting and chipping are likely to occur, and the cutting life is not sufficiently satisfactory.

[Means to solve the problem]

Therefore, from the above-mentioned viewpoint, the present inventors conducted research to produce a c-BN-based ceramic material with excellent toughness. As a result, the raw material powder used was titanium hydride (hereinafter referred to as TiHx).
) powder and c-BN powder, and T i H
While making the particle size of
and desirably Ti on the surface of the c-BN powder.
To ensure uniform distribution of Hx powder, T i
The particle size of the Hx powder is preferably 1/2 or less of the particle size of the c-BN powder, and these raw material powders are composed of the following proportions: TiHx: 0.5 to 20% by weight, c-BN: the remainder. After mixing under normal conditions and forming into a green compact, when this green compact is heated to a temperature of 1200 to 1500°C in a vacuum, the surface of the c-BN powder forms a gap between the TiHx powder and the TiHx powder. A reaction occurs and all of the T i Hx reacts, resulting in the production of titanium nitride (hereinafter referred to as TiN) and titanium boride (hereinafter referred to as T i B 2).
Since both N and T iB 2 have high activity, they are strongly bonded to c-BN as dispersed phase forming components, and the c-BN-based ceramic sintered body formed as a result is porous, but
It has extremely high toughness, and therefore, this porous c-BN, l ceramic sintered body is subjected to ultra-high pressure and high temperature treatment under normal conditions, that is, at a pressure of over 10,000 atmospheres and a temperature of over 1000°C. Give 9
The c-BN-based ceramic material with a theoretical density ratio of 8% or more has excellent toughness and high hardness equivalent to that of the C-BNM ceramic material manufactured by conventional methods. Even when used as a cutting tool for continuous high-speed cutting of cast iron, which requires toughness, or interrupted cutting of high-hardness steel, the cutting edge does not chip or chip, and exhibits excellent cutting performance over a long period of time. The research results showed that.

This invention was made based on the above research results, and uses TtHx powder with an average particle size of less than 1 and c-BN powder with an average particle size of 1 to 10 IIA as raw material powders. are blended into a composition consisting of T i Hx: 0.5 to 20% by weight, c-BN: the remainder, mixed under normal conditions, and formed into a green compact. While heating and maintaining the temperature at 1200-1500°C, c-BN and TiHx are reacted to form T
iN and TiB 2 are generated to form a porous c-BN-based ceramic sintered body having a structure in which c-BN is strongly bonded with the generated TiN and TiB 2; - c-BN which has high toughness by subjecting the BN-based ceramic sintered body to ultra-high pressure and high temperature treatment under normal conditions to densify it to a theoretical density ratio of 98% or more.
This method is characterized by a method of manufacturing a base ceramic material.

Next, the reason why the manufacturing conditions are limited as described above in the method of this invention will be explained.

A. Blend composition and powder average particle size (a) TiHx powder T i Hx powder reacts with c-BN powder to form active TiN and T iB 2, which act as a binder phase forming component. It has the effect of forming a sintered body in which the constituent components are strongly bonded to each other, but the proportion is 0.5%.
If the ratio is less than 20%, the desired effect cannot be obtained, and on the other hand, if the ratio exceeds 20%, the ratio of c-BN powder that reacts with the c-BN powder increases, and the ratio of c-BN in the ceramic material becomes relatively low. The ratio is determined to be 0.5 to 20% because the hardness decreases and the wear resistance decreases when used as a cutting tool.

In addition, in order to ensure high toughness by uniformly reacting with the T i Hx grain powder and c-BN powder, it is desirable to distribute the particles in a -like manner around them, and therefore the average grain size is 1 to 1 or more. Since uniform distribution becomes difficult due to the particle size of the C-BN powder, the average particle size was set to less than one particle.

Furthermore, in this case, the particle size of the TiHx powder is set to 1/2 or less of the particle size of the C-BN powder, so that the TiHx powder c-BN
It is best to distribute it evenly around the powder.

(b) c-BN powder When the average particle size of the c-BN powder is less than 11IJa, not only the hardness of the ceramic material decreases and the desired wear resistance cannot be secured, but also the TLHX powder The particle size is similar to that of c-BN powder, and the blending ratio of c-BN powder is relatively high, and that of T i Hx grain powder is low.
There is a part where the powders are adjacent to each other, and in this part c - B
The N+TiHx reaction does not occur, so the reaction remains localized, and as a result, strong interparticle bonding cannot be achieved throughout the ceramic material, thus ensuring high toughness in the ceramic material. On the other hand, if the average particle size exceeds 10IIja, local hardness unevenness will occur in the ceramic material, so the average particle size was determined to be 1 to 1O1tI@.

B, sintering temperature If the temperature is less than 1200 °C, c-B N +TiH
x reaction at an appropriate rate, i.e., the produced TiN and T
It is not possible to perform the reaction sufficiently with iB2 highly active, and on the other hand, if the temperature exceeds 1500℃, c
-BN becomes unstable and it becomes impossible to manufacture a ceramic material with no material variations, so the temperature was set at 1200 to 1500°C.

〔Example〕

Next, the method of the present invention will be specifically explained using examples.

As raw material powders, T i Hx grain powders and c-BN powders each having an average particle diameter shown in Table 1 were prepared, and these raw material powders were blended into the formulation composition also shown in Table 1, and acetone was used as a solvent. After wet mixing using Porous c-BN was produced by sintering at the temperature shown in Table 1 for 30 minutes.
A base ceramic sintered body is formed, and then this porous c
- BNa ceramic sintered body using a normal belt-type ultra-high pressure and high temperature device, pressure = 30,000 atm, temperature: 1200°C
, holding time: 30 minutes, ultra-high pressure and high temperature treatment was carried out according to methods 1 to 6 of the present invention, and c-BN, l
Manufactured ceramic material.

Also, for the purpose of comparison, instead of T i Hx powder, T
Using iN powder and T r B 2 powder, the first
Comparative methods 1 to 6 were carried out under the same conditions except that the composition shown in the table was used and the green compact was directly treated at 60,000 atm and 1600°C to produce a c-BN-based ceramic material. did.

Next, the theoretical density ratio, micro-Vickers hardness, and fracture toughness values of the various c-BN-based ceramic materials obtained as a result are determined by Apj, and this lpj determination result is used as the first
Shown in the table. Furthermore, when these c-BN-based ceramic materials were observed by X-ray diffraction, both c-BN and T
It was confirmed that it was composed of iN and T I B 2 and contained no T i Hx or metal TI.

Furthermore, these various c-BNI ceramic materials,
The cutting tool cutting edge is finished by cutting and polishing. Work material: 5KD57 (Rockwell hardness C scale 26)
5), a round bar material with two longitudinal grooves at 1800 pitches on the outer periphery, cutting speed: 60 m/rain, depth of cut: 0.2 mm, feed rate: 0.1 fin/rev, conditions. An interrupted turning test was conducted on high speed steel (high hardness steel) and the cutting time until chipping occurred on the cutting edge was measured. These measurement results are shown as the average value of five test cutting edges.

〔Effect of the invention〕

From the results shown in Table 1, the c-BN-based ceramic materials produced by methods 1 to 6 of the present invention all have high toughness and high hardness, do not contain TjHx and Ti, and have high hardness. When used for interrupted cutting of steel, it exhibits excellent toughness and a significantly long service life, whereas as seen in the c-BN-based ceramic materials produced by Comparative Methods 1 to 6, the raw material It is clear that if TiHx powder is not used as the powder, sufficient toughness cannot be obtained and only a short service life is exhibited in interrupted cutting of hardened steel.

As mentioned above, according to the method of the invention - conventional c-B
It is possible to produce a c-BN-based ceramic material that has high toughness that cannot be obtained with N-based ceramic materials and also has high hardness equivalent to that of N-based ceramic materials. When used as a cutting tool for high-speed continuous cutting or interrupted cutting of high-hardness steel, it provides industrially useful effects such as excellent cutting performance over a long period of time without chipping or chipping of the cutting edge. It is possible.

Claims (1)

[Claims] (1) As raw material powders, titanium hydride powder with an average particle size of less than 1 μm and cubic boron nitride powder with an average particle size of 1 to 10 μm are used, and these raw material powders are: Titanium hydride: 0.5 to 20% by weight , cubic boron nitride: the remainder, after mixing under normal conditions and forming into a green compact, this green compact is heated and held at a temperature of 1200 to 1500°C in vacuum. Then, cubic boron nitride and titanium hydride are reacted to produce titanium nitride and titanium boride. A cubic boron nitride-based ceramic sintered body is formed, and then the porous cubic boron nitride-based ceramic sintered body is subjected to ultra-high pressure and high temperature treatment under normal conditions to achieve a theoretical density ratio of 98% or more. A method for producing a cubic boron nitride-based ceramic material having high toughness.