JPH082961A - Sintered compact of metal particle-dispersed aluminum oxide base and its production - Google Patents

Abstract

PURPOSE:To obtain a sintered comapact of metal particle-dispersed aluminum oxide base having high mechanical strength and toughness at a high temperature and to provide a method for producing the sintered compact. CONSTITUTION:This sintered compact of metal particle-dispersed aluminum oxide base comprises a matrix phase substantially composed of aluminum oxide and 0.5-40wt.% of metal niobium particles having 0.05-30mum average particle diameter are dispersed in the matrix phase. The sintered compact is produced by molding mixed powder comprising 0.5-40wt.% of metal niobium powder having 0.05-30mum average particle diameter and the rest substantially composed of aluminum oxide powder and sintering the molded article in vacuum or a hydrogen gas atmosphere at 1,300-1,700 deg.C. Consequently, the sintered compact showing texture of metal niobium particles having high toughness, a low modulus of elasticity and a high melting point dispersed into the parent phase substantially constituted of aluminum oxide is obtained and has >=600MPa traverse strength at room temperature and >=550MPa at 1,200 deg.C and 26MPam<1/2> high toughness and high reliability as a structural material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal particle-dispersed aluminum oxide-based sintered body having excellent mechanical strength and toughness at high temperatures.

[0002]

2. Description of the Related Art Aluminum oxide is widely used as a representative ceramic because of its excellent properties such as chemical stability, wear resistance and high rigidity.

However, since it has a low toughness, it is brittle, and in some cases, it is unreliable for use as a member for mechanical structures.

For the purpose of overcoming this low toughness, addition of various transition metal carbonitride boride particles such as titanium carbide has been attempted, and improvement in toughness has been recognized.

Further, improvement in strength and toughness is also recognized in a material system in which refractory metal particles such as tungsten and molybdenum are added.

However, in these particle dispersion materials,
When used as a mechanical structural member, there was a problem in that high toughness was not obtained to obtain sufficient reliability and dispersed particles were expensive.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. An object of the present invention is to provide a metal particle-dispersed aluminum oxide-based sintered body having high mechanical strength and high toughness at high temperatures, and a method for producing the same.

[0008]

The metal particle-dispersed aluminum oxide-based sintered body of the present invention comprises substantially aluminum oxide as a matrix phase, and a metal having an average particle diameter of 0.05 to 30 μm in the matrix phase. Niobium particles are 0.5-4
It is characterized by being dispersed in the range of 0% by weight.

The mother phase of the sintered body of the present invention consists essentially of aluminum oxide. Magnesium oxide, zirconium oxide, or aluminum oxide as a sintering aid for aluminum oxide,
An oxide such as calcium oxide or silicon oxide may be contained in a necessary amount as its auxiliary agent.

Magnesium oxide and zirconium oxide have the effect of suppressing the abnormal grain growth of aluminum oxide during the sintering process, and calcium oxide and silicon oxide form a liquid phase at the grain boundaries during the sintering process and burn the aluminum oxide. It has the function of lowering the freezing temperature.

The addition amount of each sintering aid is preferably 5% by weight or less, and more preferably 1% by weight or less, in order not to impair the excellent corrosion resistance of aluminum oxide.

The niobium metal used in the dispersed particles of the present invention is
It has significantly higher toughness than aluminum oxide, and has a Young's modulus of 100 GPa at room temperature, which is lower than 400 GPa of other typical refractory metals such as metal tungsten of 400 GPa and metal molybdenum of 330 GPa.
Since it is as small as about 1/4 compared to 90 GPa, when metal niobium is used as dispersed particles in aluminum oxide, the fracture energy at the time of fracture is improved and the toughness is improved as compared with the case where dispersed particles are not contained. Hold.

Further, the melting point of niobium metal is 2520 ° C., which is higher than the melting point of 2053 ° C. of aluminum oxide, and since it does not melt during sintering of aluminum oxide, a high-density sintered body can be easily obtained and obtained. The high-temperature strength characteristics of the sintered body are also such that the refractory metal niobium particles in the aluminum oxide crystal grains suppress the movement of dislocations, and when the metal niobium exists in the aluminum oxide crystal grain boundaries, the grain boundary slip of the aluminum oxide crystal grains occurs. Is expected to be suppressed, so that it does not significantly deteriorate as compared with room temperature strength. Therefore, a sintered body having both high temperature strength and toughness can be obtained.

The average particle size of the dispersed metal niobium particles in the present invention is 0.05 to 30 μm, but if the particle size is less than 0.05 μm, the contribution to the improvement of toughness is small,
On the other hand, if it exceeds 30 μm, the strength of the obtained sintered body is significantly deteriorated.

To achieve both high strength and toughness, 0.0
It is more desirable to use metal niobium particles having a particle size in the range of 5 to 10 μm.

Further, the sintered body of the present invention contains dispersed metal particles in an amount of 0.5 to 40% by weight, but if it is less than 0.5% by weight, sufficient contribution to the improvement of strength and toughness is not recognized, and If the amount exceeds 5% by weight, a sufficiently dense sintered body cannot be obtained.

The method for producing the aluminum oxide-based sintered body in which the metal particles are dispersed according to the present invention includes an average particle diameter of 0.05 to 30 μm.
a mixed powder of 0.5 to 40% by weight of niobium metal of m and the balance substantially consisting of aluminum oxide powder,
1300 to 170 in vacuum or hydrogen gas atmosphere
It is characterized in that it is sintered in a temperature range of 0 ° C.

The metal niobium powder used in the present invention may be a powder obtained by an atomizing method, a rotating electrode method, a plasma method or the like as a powder having a desired average particle diameter of 0.05 to 30 μm.

In order to obtain fine particles of 1 μm or less, it is particularly preferable to use the plasma method. The shape of the powder is preferably spherical because it is easily densified during sintering, but it may be irregular such as needle-like.

The aluminum oxide powder used in the present invention is preferably a powder having an α-type crystal structure from the viewpoint of sinterability, and is fine particles having a purity of 99.5% or more and an average particle diameter of 1 μm or less. .

If the purity is less than 99.5% and the particle size exceeds 1 μm, a sufficiently high bulk density cannot be obtained during sintering.

The aluminum oxide sintering aid is not necessarily used when the aluminum oxide powder is fine and of high purity, but magnesium oxide, zirconium oxide, calcium oxide, silicon oxide and the like are not more than 5% by weight in total. You may add it.

If it exceeds 5% by weight, the excellent corrosion resistance of aluminum oxide is impaired. Desirably, addition of 1% by weight or less is preferable.

When these oxide powders are used as the sintering aid, fine particles having an average particle diameter of 1 μm or less are preferable in order to obtain a homogeneous and high density sintered body.

In the method of the present invention, these components are mixed using purified water, a solvent such as acetone or ethanol, and a planetary ball mill using an aluminum oxide or nylon pot and balls, an attritor, or the like. In a mixer, the niobium metal particles are sufficiently mixed so as to be uniformly dispersed in the aluminum oxide powder.

The mixed powder thus prepared is pressure-molded to obtain a molded product having a predetermined shape. As a molding method, a known molding method can be used, and a press molding method, a casting molding method, an injection molding method, or the like can be used.

The compact is heated and sintered at 1300 to 1700 ° C. in a vacuum or hydrogen gas atmosphere to obtain a sintered compact.

As a sintering method, a pressureless sintering method or a hot pressing method can be used. 1700 ° C
If sintered above 1700 ° C, abnormal grain growth of aluminum oxide crystal grains will occur and the strength of the sintered body will deteriorate significantly.
Sintering below is preferable, while if it is less than 1300 ° C., a sintered body having a sufficiently high bulk density cannot be obtained.

In order to obtain a sufficiently high bulk density at the time of sintering, it is preferable to hold at the sintering temperature for 1 hour or more.

In order to inexpensively manufacture a sintered body having a complicated shape, it is preferable to use the pressureless sintering method.

Sintering is carried out in a hydrogen gas atmosphere in vacuum. The reason for sintering in a hydrogen gas in a vacuum is to suppress the oxidation of dispersed metal niobium particles during the sintering process and to obtain a sintered body having a high bulk density.

When sintering in vacuum, the degree of vacuum is 10 ^-2 t.
When sintering is performed in a high vacuum of orr or higher in a hydrogen gas atmosphere, it is desirable to use a gas having a purity of 99% or higher.

When a low-purity hydrogen gas having a vacuum of less than 10 ^-2 torr and a purity of less than 99% is used, high bulk density cannot be obtained and sufficient strength and toughness cannot be obtained.

When a sintered body having a particularly high bulk density is required, as a primary sintering, it is densified to a relative density of 95% or more which eliminates open pores in a vacuum or a hydrogen gas atmosphere, and then secondary firing. As a result, gas pressure sintering or hot isostatic pressing sintering may be performed in an atmosphere of argon gas or nitrogen gas.

[0035]

The metal particle-dispersed aluminum oxide-based sintered body of the present invention contains metal niobium particles having high toughness, a low elastic modulus, and a high melting point, and is contained in a sintered body substantially made of aluminum oxide. It exhibits a structure in which metal particles are dispersed, and the bending strength is 600 MPa or more at room temperature and 55 at 1200 ° C.
It has a high strength of 0 MPa or more and a toughness of 6 MPam ^1/2 or more, and is highly reliable as a structural material.

Next, examples of the present invention will be described together with comparative examples.

[0037]

EXAMPLE Aluminum oxide (Al ₂ O ₃ ) powder (α-A
L ₂ O ₃ , purity 99.9%, average particle size 0.3 μm), and metal niobium powder (average particle size 0.
03-40 μm), magnesium oxide (MgO)
The powder (average particle size: 0.05 μm) was added in a predetermined amount (% by weight) shown in Table 1, and the mixture was kneaded for 24 hours in a ball mill made of aluminum oxide using purified water as a solvent.

Next, the obtained mixed powder was dried, molded and sintered. Molding conditions include uniaxial mold pressure of 100MP
a, pressure of 150 MPa by cold hydrostatic pressure, 60 mm
A plate-like body of x60 mm x 10 mm was obtained.

As the sintering, the sintering method shown in Table 1,
The temperature, holding time, and atmosphere were used.

When the hot press sintering method is used, the pressure is 30 MPa and the pressure is 90 mm × in a carbon die.
A 60 mm × 10 mm sintered body was obtained.

When sintered in vacuum, the degree of vacuum is 10 ⁻⁵ to
rr, purity 9 when sintered in hydrogen gas atmosphere
A gas of 9.9% was used.

The characteristics of each sintered body obtained according to the present invention are shown in Table 1 together with the amount of metallic niobium particles added, the amount of sintering aid added, and the sintering conditions.

Table 1 shows, as comparative examples, an example using TiC and W as dispersed particles and an example sintering in a nitrogen gas atmosphere.

As the density, the relative density was measured by the Archimedes method. Regarding mechanical strength, JIS R160
In accordance with JIS No. 1, a room temperature four-point bending test was carried out, and in accordance with JIS R1604, a four-point bending test was carried out at 1200 ° C. in a high temperature atmosphere, and the bending strength was measured.

Regarding toughness, SE of JIS R1607
The fracture toughness value K _IC was measured at room temperature by the PB method.

As shown in Table 1, in any of the samples according to the present invention, the room temperature strength is 600M.
It is excellent in all of Pa or higher, 1200 ° C. strength, high 550 MPa or higher fold strength, and 6.0 MPam ^1/2 or higher toughness, but the samples corresponding to Comparative Examples are particularly inferior in toughness as compared with the Examples of the present invention. It was confirmed.

[0047]

[Table 1]

[0048]

EFFECTS OF THE INVENTION According to the present invention, in the metal particle-dispersed aluminum oxide-based sintered body as described above, it is possible to produce a highly reliable sintered body having both high mechanical strength and toughness at high temperature. It becomes possible and its industrial utility is very large.

Claims (2)

[Claims] 1. An aluminum oxide is substantially a matrix phase, and the matrix phase has an average particle size of 0.05 to 0.05.
A metal particle-dispersed aluminum oxide-based sintered body, wherein 30 μm of metal niobium particles are dispersed in a range of 0.5 to 40% by weight. 2. A mixed powder comprising 0.5 to 40% by weight of niobium metal powder having an average particle size of 0.05 to 30 μm and the balance substantially consisting of aluminum oxide powder is molded, and the mixture is vacuumed or in a hydrogen gas atmosphere. A method for producing a metal particle-dispersed aluminum oxide-based sintered body, which comprises sintering in a temperature range of 1300 to 1700 ° C.