JP2944271B2 - Method for producing alumina-based composite sintered body and alumina-based composite 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 method for producing a dense and high-hardness alumina-based composite sintered body, and to an alumina-based composite sintered body obtained by the method.

[0002]

2. Description of the Related Art In general, alumina ceramics are particularly thermally and chemically stable among ceramics, and have high hardness and relatively high strength. In particular, since it has the highest hardness among oxide ceramics, it uses the abrasion resistance due to its hardness to use powder such as sandblasting equipment, shot blasting equipment, powder classifier, dust blower, etc. Used for equipment applications
Is being done .

[0003] By the way, in sand blasting machines and the like, sand containing corundum having the same hardness as alumina ceramic having high hardness may be used in order to increase the processing efficiency. In that case, the wear resistance of erosion wear, which is damage due to collision of solid particles, decreases when the hardness difference between the solid particles and the colliding material disappears, so that conventional alumina ceramics cannot exhibit sufficient performance. This is because there is a problem. Therefore, it is desired that alumina ceramics have further improved hardness.

[0004] Generally, to increase the hardness of ceramics,
There is a method of dispersing particles having higher hardness than the matrix. To increase the hardness of alumina ceramics, a method of dispersing non-oxide ceramic particles having a higher hardness than alumina ceramics, such as SiC, TiC, and TiN, is often used.

[0005]

However, since the above-mentioned non-oxide ceramic particles are difficult to sinter, if these are dispersed in alumina, a dense sintered body having a high hardness in ordinary normal pressure sintering is obtained. It is very difficult to get. Therefore, such sintering is usually performed by using a hot press method or adding a sintering aid.

However, when sintering is performed by the hot press method, only a simple shape product can be manufactured, and in order to produce a product having a complicated shape such as a machine component, the product may be extremely processed due to its high hardness. There is an inconvenience that costs are increased. In addition, when sintering is performed using a sintering aid, the hardness of the alumina itself is reduced due to the reaction with the alumina, which causes a new disadvantage that the effect of the particle dispersion is offset.

[0007] The present invention has been made in view of the above-mentioned circumstances, and an object thereof is that it can be manufactured by normal-pressure sintering without using a sintering aid, and has a higher efficiency than conventional ones. An object of the present invention is to provide a method capable of manufacturing an alumina-based composite sintered body having a hardness and a sintered body obtained by the method.

[0008]

Means for Solving the Problems Claim 1 of the present invention
In the method for producing an alumina-based composite sintered body described above, an Al ₂ O ₃ powder having an average particle diameter of 0.05 μm or less and a SiC powder having an average particle diameter of 0.05 μm or less are mixed and mixed at 3 to 10% by volume. Powder, and put this mixed powder in an inert atmosphere for 1 hour.
Firing at 150 to 1350 ° C., and then crushing and shaping the fired powder to form a compact, and then sintering the compact at 1500 to 1700 ° C. in an inert atmosphere at normal pressure. Was the solution. In the method of manufacturing an alumina-based composite sintered body according to claim 2, the Al ₂ O ₃ powder is BE
The means for solving the above-mentioned problem is that the γ-type crystal form with a T specific surface area of 40 m ² / g or more is used, and the SiC powder is a β-type crystal form with a BET specific surface area of 40 m ² / g or more. . The alumina-based composite sintered body according to claim 3, wherein a 90 to 97 vol% of Al ₂ O ₃ particles, 3-10 volume
% Of SiC particles.
_The SiC particles are dispersed inside the ₂ O ₃ particles,
What has a rate of 2% or less is a means for solving the problem.

Hereinafter, a method for producing an alumina-based composite sintered body of the present invention and an alumina-based composite sintered body obtained by the method will be described in detail. In order to increase the hardness of the alumina-based composite sintered body, the present inventor has found that when dispersing SiC particles, Al ₂ O ₃ and SiC having a large specific surface area, excellent surface activity, high purity and a very small particle diameter are used. These particles are mixed with each other using a particle, and a calcination treatment is performed after the mixing, so that only Al ₂ O ₃ is preferentially grown due to a difference in the particle growth rate, and AlC is dispersed inside the particle to thereby form an Al ₂ O _3. The inventor of the present invention came up with the idea of preparing a powder, molding the powder and sintering the powder under normal pressure.

That is, according to the present invention, first, as the Al ₂ O ₃ raw material powder, the particle diameter is set to 0.1 to obtain a desired sintered density.
The one having a size of 05 μm or less is used. Further, the Al ₂ O ₃ powder has a BET specific surface area of 40 m ^{2 in} terms of surface activity.
/ G or more and having a γ-type crystal form are preferred. In addition, a SiC raw material powder having a particle diameter of 0.05 μm or less is used. The reason why the particle diameter is set to 0.05 μm or less is that if it exceeds this, even if the Al ₂ O ₃ particles grow, they will not be sufficiently dispersed therein. Further, as the SiC powder, a powder having a BET specific surface area of 40 m ² / g or more and a β-type crystal form is preferable in terms of surface activity and hardness.

Then, the Al ₂ O ₃ powder and the SiC powder are mixed to form a mixed powder. In this case, if the difference between the particle diameters is large, it is difficult to achieve uniform mixing. Therefore, it is preferable that these two powders have the same particle diameter. Also, S
The mixing amount of the iC powder is the whole (Al ₂ O ₃ powder and SiC
3 to 10% by volume of the total amount with the powder). The reason why the amount of the SiC powder is set to 3 to 10% by volume is that if the content is less than 3% by volume, the effect of increasing the hardness of the sintered body due to the addition of SiC is not sufficiently exhibited. S
This is because the iC particles do not sufficiently disperse in the Al ₂ O ₃ particles, so that sufficiently high hardness is not exhibited. Further, regarding such a mixing operation of the Al ₂ O ₃ powder and the SiC powder,
A well-known method such as a ball mill method is employed because of the usual powder mixing.

Next, the obtained mixed powder is fired at a temperature of 1150 to 1350 ° C. under an inert atmosphere and a normal pressure. The reason for sintering is that S _{2 is} contained in the Al ₂ O ₃ particles as described above.
This is because it is difficult to uniformly disperse iC and to form the fine particles as they are, so that the particles are grown by firing. Further, the firing temperature is set at 1150 to 1350.
C. is because the alumina does not grow sufficiently under 1150 ° C., and the SiC particles do not disperse inside.
On the other hand, when the temperature exceeds 1350 ° C., the alumina particles become too large and the densification of the sintered body is hindered. Note that the inert atmosphere referred to here is an atmosphere such as helium, argon, nitrogen, or vacuum, but is preferably performed in a vacuum atmosphere in order to remove a gas generated by a substance attached to the surface during firing.

Next, the fired powder is formed into a predetermined shape by a well-known method, and under an inert atmosphere under normal pressure at 1500
Sinter at a temperature of 1700 ° C. In this case, the sintering temperature is 1
The reason for setting the temperature to 500 to 1700 ° C. is that if the temperature is lower than 1500 ° C., the porosity is not reduced to 2% or less, and satisfactory hardness cannot be obtained. This is because a decrease occurs. Note that the inert atmosphere referred to here is also an atmosphere such as helium, argon, nitrogen, or vacuum. The thus obtained a
The lumina-based composite sintered body is composed of 90 to 97% by volume of Al ₂ O ₃ particles.
Pressure Sintered Body Containing Particles and 3 to 10% by Volume of SiC Particles
Wherein the SiC particles are separated inside the Al ₂ O ₃ particles.
And the porosity is 2% or less.
It is elaborate.

[0014]

According to the method for producing an alumina-based composite sintered body according to the first aspect of the present invention, fine alumina and SiC powder are used as raw material powders, and the SiC particles are dispersed in the alumina powder particles by firing treatment. By sintering it, an alumina- based composite sintered body in which SiC particles are uniformly dispersed at normal pressure is obtained. According to the method for producing an alumina-based composite sintered body according to the _{second aspect} , the surface activity is high as an Al ₂ O ₃ powder, the BET specific surface area is 40 m ² / g or more, and γ
The use of a SiC powder having a high surface activity and hardness, a BET specific surface area of 40 m ² / g or more and a β-type crystal form, thereby providing higher hardness alumina. A basic composite sintered body is obtained. According to the alumina composite sintered body of the _{third aspect} , Al ₂ O ₃ particles
Disperse SiC particles inside to reduce the porosity to 2% or less.
High-hardness alumina by densifying the sintered body
It becomes a basic composite sintered body.

[0015]

EXAMPLES Hereinafter, the alumina-based composite sintered body of the present invention will be described more specifically with reference to examples. γ-alumina powder (average particle size: 0.004 μm, BET specific surface area: 300 m
² / g) of 95% by volume, β-SiC powder synthesized by a high-frequency plasma CVD method (average particle size: 0.02 μm, BET
Each powder was blended so that the specific surface area (50 m ² / g) was 5% by volume, and mixed by a ball mill for 72 hours to obtain a mixed powder. Next, the obtained mixed powder was dried, and further dried for 120 minutes.
After firing at 0 ° C. for 2 hours in an argon atmosphere, the fired powder was crushed and molded to obtain a molded body. Thereafter, the obtained molded body was heated at 1600 ° C. for 1 hour under normal pressure in nitrogen,
Sintering was performed to obtain a sintered body.

The density of the obtained sintered body was measured by the Archimedes method using water displacement, and the relative density was calculated from the theoretical density. The Vickers hardness was measured with a Vickers hardness meter. Table 1 shows the results.

For comparison, as shown in Table 1, the alumina-based composite sintered body of the present invention uses a SiC powder having an average particle size of 0.3 μm which is out of the range of the particle size of the raw material powder. And a sintered body of alumina alone not mixed with SiC powder were prepared, and the relative density and Vickers hardness were measured. The results are also shown in Table 1.

[Table 1] From the results shown in Table 1, it was confirmed that the product of the present invention was easier to be densified than the product of the comparative example and had high hardness.

[0018]

As described above, in the method for producing an alumina-based composite sintered body according to the first aspect of the present invention, fine alumina powder and SiC powder are used as raw material powders. Alumina sintered body in which SiC particles are dispersed uniformly at normal pressure by dispersing SiC particles in a sintering medium, and easily producing a sintered body having a high hardness and a complicated shape. can do. Further, the method for producing an alumina-based composite sintered body according to claim 2 uses an Al ₂ O ₃ powder having a high surface activity, a BET specific surface area of 40 m ² / g or more and a γ-type crystal form, By using SiC powder having high surface activity and hardness, having a BET specific surface area of 40 m ² / g or more and having a β-type crystal form, a sintered body having higher hardness can be obtained. The alumina-based composite sintered body according to the _{third aspect} is obtained by dispersing SiC particles inside Al ₂ O ₃ particles and reducing the porosity to 2% or less. In addition to the properties, the hardness is further enhanced as compared with the conventional one, and therefore, it is a very effective material as compared with the conventional one.

Claims (3)

(57) [Claims] An Al ₂ powder having an average particle size of 0.05 μm or less.
₃ to 10% by volume of SiC powder having an average particle diameter of 0.05 μm or less is mixed with O ₃ powder to form a mixed powder, and the mixed powder is fired at 1150 to 1350 ° C. in an inert atmosphere. The fired powder is crushed and formed into a compact, and then the compact is placed in an inert atmosphere under normal pressure at 1500 to
A method for producing an alumina-based composite sintered body, comprising sintering at 1700 ° C. 2. The method for producing an alumina-based composite sintered body according to claim 1, wherein the Al ₂ O ₃ powder has a γ-type crystal form having a BET specific surface area of 40 m ² / g or more,
A method for producing an alumina-based composite sintered body, characterized in that the SiC powder has a β-type crystal form with a BET specific surface area of 40 m ² / g or more. 3. An Al ₂ O ₃ particle of 90 to 97% by volume ,
Pressureless sintered body containing 10 to 10% by volume of SiC particles.
Thus, the SiC particles are dispersed inside the Al ₂ O ₃ particles.
And a porosity of 2% or less .