JPH03290356A - Aluminum oxide based ceramics having high toughness and strength and production thereof - Google Patents

Abstract

PURPOSE:To improve toughness and strength of the title ceramics by blending specific Al2O3 powder with metal oxide powder and metal carbide, nitride or oxide powder and then forming the blend under pressure and sintering the formed article in Ar- containing atmosphere. CONSTITUTION:(a) Al2O3 powder having <=0.6mum average grain size is blended with (b) 1-12wt.% one or two or more kind of metal oxides among oxides of Y, Mg, Cr, Ni, Co and rare earth elements having <=1mum average grain size and (c) 2.1-50wt.% one or two or more kind of metal carbide, nitride or oxide powder among carbide, (carbon) nitride, carboxide, nitride and carbon nitride oxide of Ti, Zr and Hf containing >=10wt.% compound having <=0.3mum grain size and the blend is formed into a pressed body, which is then sintered in an atmosphere of Ar or Ar and inert gas at 1680-1830 deg.C for 10-40min and then retained in an atmosphere of Ar or Ar and inert gas at 1300-1450 deg.C for 2-10hr to provide Al2O3 based ceramics containing 0.5-10wt.% metal oxide other than Al2O3 and CrO2, 2-40wt.% component (c) in the crystalline grain boundary of (a) in which (b) is made to solid solution and containing 0.1-30wt.% component (c) having <=0.3mum grain size in the cystalline grain boundary of (a) as rigid disperse phase component.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention has particularly high toughness and strength, and also has excellent electrical conductivity, so it can be formed by electrical discharge machining. Therefore, aluminum oxide ( The present invention relates to a base ceramic (hereinafter referred to as A I 20 s) and a method for producing the same.

[Conventional technology]

Conventionally, as an AM 20 a-based ceramic and a method for manufacturing the same, a method described in, for example, Japanese Patent Application Laid-Open No. 53-1.18410 is known.

This method, as a raw material powder, corresponds to the production of AD203-based ceramics of the present invention, A I 20
s powder, Y, Mg, Cr, Ni.

Co, and oxides of rare earth elements (hereinafter referred to as Y
O, MgO, Cr2O3, Cod.

3 N i O, and metal oxide powder consisting of one or more types of R20a (where R: rare earth element), as well as carbides, nitrides, carbonitrides of Ti, Zr, and Hf, Carbonates, nitrides, and carbonitoxides (hereinafter referred to as MC, respectively).

MN, MCN, MCO, MNO, and MCN0, where M consists of one or more of Ti, Zr, and Hf). Powders of oxides (hereinafter referred to as M-C-N-0) are prepared, and these raw material powders are mixed in weight% (
The following % indicates weight %), metal oxide powder = 10% or less, M-C◆N-0 powder: 10 to 90%, A M 20 g powder: the remainder, and the usual After mixing and forming into a compact under the same conditions, e.g.
Temperature = 1580°C in a nitrogen partial pressure atmosphere of oOtorr,
This is a method for producing A it 20 a-based ceramics by hot pressing under the conditions of pressure = 30 atm and holding time = 10 to 30 minutes, and the produced A ρ20
The three-group ceramic has a structure in which the above-mentioned metal oxide constitutes a binder phase, the above-mentioned A I 20 a and M・C-N・0 constitutes a dispersed phase, and has substantially the same component composition as the blended composition. It is something that we have.

[Problem to be solved by the invention]

On the other hand, in recent years, demands for labor saving and cost reduction in various industrial fields have become even more severe.For example, the same is true in the field of molding processing using dies. There is a tendency to demand further extension of the lifespan of conventional A.
g2O3 group ceramics and any other A
I203-based ceramics do not yet have sufficiently satisfactory toughness and strength, so it is currently impossible to meet these requirements.

[Means to solve the problem]

Therefore, from the above-mentioned viewpoint, the present inventors conducted research to develop A II 20a ceramics with high toughness and high strength, and as a result, as a raw material powder,
A 1' 20 a powder with an average particle size of 0.6 tHo or less, the above metal oxide powder with an average particle size of 1- or less, and an average particle size of:
Using the above M-C-N 0 powder which accounts for 10% or more with a particle size of 0.3- or less with a mark of 1.5 or less, the above-mentioned metal oxide powder: 1 to 12%, The above M-C-N・0 powder: 2°1-50%, A I 2
0s powder: The remainder is blended into a composition consisting of the following, mixed under normal conditions, and formed into a green compact.
In a mixed gas atmosphere of r or Ar and inert gas, temperature:
When high-temperature short-time sintering is performed under the conditions of holding at 1680-1830°C for 10-40 minutes, a part of the metal oxide (in this case Cr20a is completely dissolved) is dissolved in the high-temperature short-time sintering. Solid solution in Ag2O3, the rest is Ag2o
It forms a compound with 3 and exists in the grain boundaries of Ap
．． M-C with a particle size of 3- or less and an average particle size of 1.5- or less
-A1 with a structure in which N-0 is distributed as a hard dispersed phase
A 1203 group ceramic is formed, and this is further sintered continuously or intermittently after the high temperature short time sintering in an atmosphere of Ar or a mixed gas of Ar and an inert gas at a pressure of 100 to 2000 atm at a temperature of 1300 to 1450. ℃2
When heat treatment is performed under the conditions of ~10 hours of retention, this heat treatment results in AlI2O3
The metal oxide dissolved therein promotes the grain growth of A I 203, so that Al 1203
◆M-C- with a fine particle size of 0.3- or less of N-0
Grain growth while incorporating N-0 into crystal grains - Ag2
M-C-N-0 is distributed as a hard dispersed phase at the grain boundaries of O3, but there is also a structure in which M-C-N-0 with a fine grain size of 0.3- or less is distributed within the Aρ203 grains. The resulting Ag2o3-based ceramics have Ag2o
The research results showed that the fine M-C-N.0 distributed within the crystal grains of No. 3 gave significantly higher strength and toughness than Ag2o3-based ceramics that did not contain this.

This invention was made based on the above research results, and uses Al120 as a raw material powder with an average particle size of 0.6 groups or less.
3 powder, 1 part or less of the above metal oxide powder, and an average particle size of 1.5ρ or less, 0.3t! Using the above M-C-N-0 lead C- containing 10% or more of particle size smaller than In, these raw material powders were prepared: the above-mentioned metal oxide: 1 to 12%, the above-mentioned M◆C-N-0: 2. 1-50%, Al120a
: The remainder is blended into a composition consisting of the following, mixed under normal conditions, and formed into a green compact.
In a mixed gas atmosphere of r or Ar and inert gas, temperature:
Hold at 1880-1830°C for 10-40 minutes, sinter at high temperature for a short period of time, and then continuously or intermittently sinter at 100-2000 atm A or a mixed gas atmosphere of Ar and inert gas. Medium, temperature 71300-1450℃ 2~
A method for producing Ag2O3-based ceramics by subjecting Ag2O3 crystal grain elongation heat treatment under the conditions of holding for 10 hours, and A I 20 a and the above metal oxide (however, Cr 20
(excluding 3): 5 to 10%, and the above M-C-N-02 to 40% as a hard dispersed phase forming component, and also in the crystal grains of A12o3 (1,3 blood). The above M-C-N-0 with the following grain sizes is present as a hard dispersed phase forming component at a ratio of 01 to 30% (however, the total of the above M-C-N-0 at the grain boundaries and within the grains) f
fi: 50% by weight or less).

Next, the reason for limiting the manufacturing conditions and component compositions as described above in the ceramics and the manufacturing method thereof of the present invention will be explained.

A. Manufacturing conditions (a) Average grain size of Ag203 powder When the average grain size becomes larger than 0.8tEO, the average grain size of Al2O3 crystal grains in ceramics is reduced to 0.8tEO.
It becomes difficult to suppress it to 9- or less, and A 1' 20
Ceramics with s-crystal grains exceeding 0.9 tln have a significant decrease in strength, so the average grain size is set to 0.9 tln. f3u
It was set as Ia or below.

(b) Blending ratio of M-C-N・0 powder M-C-N-0 has a hard dispersion phase distributed in Ag2O3 grain boundaries to improve the wear resistance of ceramics, and It also distributes within the crystal grains and has the effect of improving the strength and toughness of ceramics, but if the blending ratio is less than 2.1%, the content ratio in ceramics will also be 2.
．． If it is less than 1%, the desired effect cannot be obtained from the above action,
On the other hand, when the blending ratio exceeds 50%, sinterability decreases,
The content rate in ceramics has also increased to more than 50%, and the content rate of AN),,03 has become relatively low.
AI! Since the heat resistance and oxidation resistance brought about by 20 a decrease, the blending ratio was changed to 2.
．． It was set at 1 to 50%. In this case, the average particle size of the powder is 1
．． When it exceeds 5-, the average particle size in ceramics also decreases to 1.
．． The average particle size must be 1.5 or less, as exceeding 5-5-100 mm will result in coarseness and a decrease in strength. In addition, during Ag2O3 grain growth heat treatment, A i) 2
In order to easily incorporate and distribute M-C-N O into the 0s crystal grains, the grain size must be 0.3- or less, and in this case, the grain size of 0.3- or less must be M-C things
- By making the proportion of -N-0 powder 10% or more, the AI! 20a By activating the incorporation into the crystal grains during crystal grain growth and controlling the ratio to 0.1 to 30% of the total ceramic, the strength and toughness of the ceramic can be significantly improved.

(c) Mixing ratio of metal oxide powder During high-temperature, short-time sintering, part of the metal oxide becomes Ag2.
In addition to forming a compound with O3 to improve sinterability and thereby improving the strength of ceramics, the remainder is Al2O3.
A solid solution in A1) 0 during heat treatment for 20g grain growth
．． It has the effect of promoting grain growth of Af1203 while incorporating fine M-C-N・0 of 3Ltn or less into the crystal grains, but if the blending ratio is less than 1%, the desired effect is not obtained. On the other hand, if the blending ratio exceeds 12%, it will remain in the ceramic in the form of metal oxides and the hardness and strength, especially at high temperatures, will decrease. was set at 1-12% (
As a natural result of this, the content ratio in ceramics is also 1 to 12%). In addition, when the average grain size exceeds ILm, it becomes difficult to form a solid solution in A i' 20 a and to form a compound, and the metal oxide remains at the grain boundary, which makes it difficult for ceramics to work at high temperatures. Since this causes a decrease in strength and hardness, the average particle size is set to 1- or less.

(d) High-temperature, short-time sintering conditions Satisfactory sintering cannot be achieved even if the atmospheric pressure is less than 0.8 atm, or if the temperature and holding time are less than 1000°C and less than 10 minutes, respectively. The densification due to the solid solution of the oxide and the formation of compounds becomes insufficient, and on the other hand, if the atmospheric pressure exceeds 5 atm, the gas generated during sintering becomes internal and the densification becomes insufficient. It was not possible to obtain a sintered body, and when the temperature exceeded 830°C, the raw material powder began to decompose.
The gas generated by this decomposition reduces sinterability, and if the holding time exceeds 40 minutes, especially M
- Grain growth occurs in the fine grain size of -C/N-0 of 0.3 tlIo or less, and the incorporation into Ag2O3 crystal grains in the subsequent process is not carried out sufficiently, so the conditions are as follows:
Atmospheric pressure: 0.8 to 5 atm, temperature: 1680 to 18
The temperature was set at 30° C. and the holding time was set at 710 to 40 minutes.

(e) Grain growth heat treatment of Ag203 This heat treatment reduces the bore in the ceramic to bring it close to true density, and A,i'203
The growth of crystal grains is measured, and at the same time the grain size of M-C-N-0 existing at Ag2O3 grain boundaries is OJ! This is done to improve the strength and toughness of ceramics by taking in fine M-C-N.0 of In or less and distributing it within the crystal grains. Removal is insufficient and the temperature is 1300
If the holding time is less than 2 hours, the growth of A1120g crystal grains will be extremely slow, making it impractical.
ji' 203 It is impossible to make the proportion of M-C-N・0 distributed within the crystal grains more than 0.5% in the whole ceramic, and on the other hand, the atmospheric pressure exceeding 2000 atm is technically and practically impractical. Moreover, temperatures exceeding 1450°C cause the growth of Ap203 grains and M-C-
N・0 grains also grow, and the proportion of M・C−N−0 distributed within the Ag2O3 crystal grains becomes extremely small. The conditions should be changed to atmospheric pressure 1.
00~2000 atm, temperature: 1300~1450℃,
The holding time was set at 2 to 10 hours.

In addition, in the method of this invention, an average particle size of 1.5- or less containing 10% or more of fine particles with a diameter of 0.3 μs or less is used.
-C-N-0 powder has an average particle size of 0.7 to 2-M-C
-N-0 powder with a diameter of 1 to 31. Insert aM's WCC cemented carbide balls together into the attritor, 10 to 100
Prepared by subjecting to time grinding.

B. Component composition (a) Compound of Ag203 and metal oxide This compound is:
As mentioned above, it is formed during high-temperature, short-time sintering, and has the effect of improving sinterability, densifying ceramics, and improving toughness, but if the content is less than 0.5%, the desired effect will not be achieved. On the other hand, if the content exceeds 10%, the hardness decreases and the wear resistance deteriorates, so the content was set at 0.5 to 10%.

(b) M-C-N・0 at grain boundaries These components have the effect of improving the wear resistance of ceramics, but if their content is less than 2%, the desired effect of improving wear resistance cannot be obtained. On the other hand, if the content exceeds 40%, the strength of the ceramic will decrease, so the content was set at 2 to 40%.

(c) M-C-N-0 in the crystal grains These components have the effect of dramatically improving the toughness and strength of ceramics as described above, but if their content is 0.
．． If the content is less than 1%, the desired effect cannot be obtained, and if the content exceeds 30%, the toughness will decrease, so the content was set at 0.1 to 30%. However, in this case, as mentioned above, M-C at the grain boundaries and within the grains
-N.0 must not exceed 50% in total.

〔Example〕

Next, the ceramics of the present invention and the method for producing the same will be specifically explained using examples.

Various Aps shown in Table 1 were used as raw material powders.
Using 203 powder, M-C-N-0 powder, and metal oxide powder, these raw material powders were blended into the composition shown in Table 1, mixed for 72 hours in a ball mill, and dried. A green compact with dimensions of 30 mm x 30 mm (plane) and 10 mm (thickness) and a compact of 120 mm (diameter) x 60 mm (thickness) were press-molded at a pressure of 11 on/c-. These compacts were then subjected to high-temperature short-time sintering and Ap20 under the same conditions shown in Table 1.
3. Methods 1 to 15 of the present invention by performing grain growth heat treatment
Ceramics 1 to 15 of the present invention were produced respectively.

In addition, for the purpose of comparison, the raw material powders shown in Table 1 were blended to the composition shown in Table 1, and further, instead of the above-mentioned high-temperature short-time sintering and A 11203 grain growth heat treatment, Conventional methods 1 to 5 were carried out under the same conditions except that hot pressing was carried out under the conditions shown in Table 1 to produce conventional ceramics 1 to 5, respectively.

Next, for the various ceramics obtained as a result, the component composition, theoretical density ratio, Rockwell hardness (A scale), transverse rupture strength, and indentation method (1M method)
The fracture toughness value was measured.

In addition, the above diameter: 120mm x thickness: [i0a++
An L-shaped through hole with a side length of 30+us was made in the center of the circular ceramic disc marked * by electric discharge machining, and this was used as a die. Workpiece material: pure AII (heating temperature: 480'C), extrusion speed : All was warm extruded under the conditions of 20 rn/gin s, and the extrusion time from the time when cracks occurred in the die to the end of its service life was measured. These results are shown in Table 2.

〔Effect of the invention〕

From the results shown in Tables 1 and 2, it is clear that the method of the present invention
The ceramics 1 to 15 of the present invention manufactured by the conventional methods 1 to 15 all have a theoretical density ratio of 99% or more, are dense, and have extremely few micropores, and are superior to the conventional ceramics 1 to 5 manufactured by the conventional methods 1 to 5. It has superior strength and toughness, as well as high hardness, so these properties provide excellent fracture resistance when used as a die for extrusion processing under harsh conditions. It is clear that it exhibits excellent performance over a long period of time.

As described above, according to the method of the present invention, it is possible to produce Aρ203-based ceramics that have high strength and toughness, and also have excellent wear resistance and electrical conductivity. A f) of this invention 20
Since a-based ceramics have the excellent properties described above, they can of course be used in the manufacture of dies, but can also greatly contribute to higher speeds, higher performance, and labor savings in other industrial technology fields. Industrially useful effects such as these are brought about.

Claims (1)

[Claims] (1) At the grain boundaries of aluminum oxide in which a metal oxide consisting of one or more of oxides of Y, Mg, Cr, Ni, Co, and rare earth elements is dissolved. , Compounds of the above metal oxides excluding aluminum oxide and chromium oxide: 0.5 to 10% by weight, and carbides, nitrides, carbonitrides, carbonates, and nitrides of Ti, Zr, and Hf as hard dispersed phase forming components. 2 to 40% by weight of metal carbon/nitrogen/oxide consisting of one or more of oxides and carbonitride oxides, and furthermore, 0.3 μm in the crystal grains of the aluminum oxide. The above-mentioned metal carbon/nitrogen/oxides with the following fine grain sizes must be present as hard dispersed phase forming components at a ratio of 0.1 to 30% by weight (however, the above-mentioned metal carbon/nitrogen/oxides at the grain boundaries and within the grains) (The total amount of oxides is 50% by weight or less). An aluminum oxide-based ceramic having high toughness and strength. (2) As raw material powder, aluminum oxide powder with an average particle size of 0.6 μm or less, Y, Mg, Cr, with an average particle size of 1 μm or less,
Metal oxide powder consisting of one or more of oxides of Ni, Co, and rare earth elements, and an average particle size of 1.5 μm or less, with a particle size of 0.3 μm or less being 10
Carbides of Ti, Zr, and Hf containing at least % by weight,
Metallic carbon/nitrogen/carbonitride consisting of one or more of nitrides, carbonitrides, carbonates, nitrides, and carbonitrides.
Oxide powder is prepared, and these raw material powders are composed of, in weight percent, metal oxide powder: 1 to 12%, metal carbon/nitrogen/oxide powder: 2.1 to 50%, and aluminum oxide powder: the remainder. After mixing and forming into a powder compact under normal conditions, the compact is heated to 1680 to 1000 ml in an atmosphere of Ar or a mixed gas of Ar and inert gas at 0.8 to 5 atm. Hold at 1830°C for 10-40 minutes, sinter at high temperature for a short time under the following conditions, then continuously or intermittently sinter in Ar or a mixed gas atmosphere of Ar and inert gas at 100-2000 atm, temperature: 1300°C. ~1450℃2~
A method for producing an aluminum oxide-based ceramic having high toughness and high strength, comprising: holding the aluminum oxide for 10 hours and subjecting the aluminum oxide to crystal grain growth heat treatment under the following conditions.