JP3414835B2 - Metal particle-dispersed aluminum oxide-based sintered body and method for producing the same - Google Patents

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.

[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]

The present invention has been made to solve the above 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, 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 the matrix phase contains Elinvar and Invar having an average particle diameter of 0.05 to 30 μm. 0.5 to 30 weight of at least one spherical alloy particle selected from Super Invar, Stainless Invar, 42 Nickel and Kovar
% , And the relative density is 98% or more .

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.

A typical main component of the alloy used for the dispersed particles of the present invention is 36Ni.12Cr.F in the case of Elinvar.
e, 36Ni ・ Fe for Invar, 31Ni ・ 5Co ・ Fe for Super Invar, 36Fe ・ 10Cr ・ Co for Stainless Invar, 4 for 42 Nickel
2Ni ・ Fe, 29Ni ・ 17Co ・ F for Kovar
It is e.

The typical values of the Young's modulus at room temperature and the average coefficient of thermal expansion in the temperature range from room temperature to 400 ° C. for each alloy are 80 GPa and 8 × 10 ⁻⁶ / ° C. in the case of Elinvar,
For Invar 147GPa and 9 × 10 ^-6 / ℃, when the Super Invar 150GPa and 8 × 10 ^-6 / ℃, when stainless invar 180GPa and 8 × 10 ^-6 / ℃,
In the case of 42 nickel, it is 145 GPa and 7 × 10 ⁻⁶ / ° C., and in the case of Kovar, it is 180 GPa and 5 × 10 ⁻⁶ / ° C.

Elinvar, Invar, Super Invar, Stainless Invar, 42 used for the dispersed particles of the present invention
Nickel and Kovar each have significantly higher toughness than aluminum oxide, and have a Young's modulus of 80 to 180 GPa at room temperature and 390 of aluminum oxide as described above.
Since it is as small as half or less than GPa, when these alloys are used as dispersed particles, the fracture energy at the time of fracture is improved and toughness is improved as compared with the case where dispersed particles are not contained.

When the coefficient of thermal expansion (coefficient of linear expansion) is from room temperature to 400 ° C., it is about 5 to 9 × 10 ⁻⁶ / ° C., which is equal to or smaller than 8 × 10 ⁻⁶ / ° C. of aluminum oxide, If the coefficient of thermal expansion is smaller than that of aluminum oxide, a thermal residual stress is generated in the aluminum oxide near the alloy particles due to the difference in the coefficient of thermal expansion with aluminum oxide during the sintering temperature reduction process, and the fracture energy at the time of fracture Has the effect of further improving the toughness and further improving the toughness.

In particular, in order to obtain a particle-dispersed aluminum oxide-based sintered body having both high strength and toughness, which is the object of the present invention, Elinvar having a particularly small Young's modulus or 42 nickel having a small Young's modulus and a small thermal expansion coefficient. Is more preferably used.

Further, in order to obtain a sintered body having high corrosion resistance in addition to strength and toughness, it is preferable to use stainless steel invar.

The average particle size of the dispersed alloy particles in the present invention is 0.05 to 30 μm, but the particle size is 0.05.
If it is less than μm, the contribution to the improvement of toughness is small,
When it exceeds 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 alloy particles having a particle size in the range of 5 to 10 μm.

The sintered body of the present invention contains dispersed alloy particles in an amount of 0.5 to 30% by weight, but if the amount is less than 0.5% by weight, sufficient contribution to improvement of strength and toughness is not observed. If the amount exceeds 5% by weight, a sufficiently dense sintered body cannot be obtained.

As the method for producing the metal particle-dispersed aluminum oxide-based sintered body of the present invention, at least one selected from Elinvar, Invar, Super Invar, Stainless Invar, 42 Nickel and Kovar having an average particle diameter of 0.05 to 30 μm.
Mold a mixed powder consisting of 0.5 to 30 wt% of one type of spherical alloy powder and the balance substantially aluminum oxide powder, and sinter in a temperature range of 1300 to 1420 ° C in a vacuum or hydrogen gas atmosphere. It is characterized by.

As the alloy powder used in the present invention, those obtained as a powder having a desired average particle diameter of 0.05 to 30 μm by an atomizing method, a rotating electrode method, a plasma method or the like can be used.

[0023] The shape of the powder spherical not preferred from the ease of densification during sintering.

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 is more than 1 μm, the bulk density cannot be made sufficiently high at the melting point of the dispersed alloy or less 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, a planetary ball mill using a pot and balls made of aluminum oxide, nylon, etc., an attritor, etc. In a mixer, the alloy 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 body 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.

This compact is heated and sintered at 1300 to 1420 ° 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.

The melting points of the alloys used in the present invention are 1420 ° C. for Elinvar, 1425 ° C. for Invar, 1430 ° C. for Super Invar, 1450 ° C. for Stainless Invar, and 1430 for 42 Nickel.
℃, 1450 ℃ for Kovar, 1420
If sintered above ℃, the dispersed alloy particles will be melted or decomposed during the sintering process, and the desired particle dispersion material cannot be obtained.
If it is less than ℃, 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. The pressureless sintering method is preferably used to inexpensively manufacture a sintered body having a complicated shape.

Sintering is performed in a vacuum and hydrogen gas atmosphere. The reason for sintering in a hydrogen gas in a vacuum is to suppress the oxidation of the dispersed alloy 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 a secondary firing is performed. As a result, gas pressure sintering or hot isostatic pressing sintering may be performed in an atmosphere of argon gas or nitrogen gas.

[0038]

The metal particle-dispersed aluminum oxide-based sintered body of the present invention has at least one selected from the group consisting of Elinvar, Invar, Super Invar, Stainless Invar, 42 Nickel and Kovar, which have high toughness, low elastic modulus and low thermal expansion coefficient.
Includes seed alloy particles, exhibiting a structure in which the alloy particles are dispersed in a sintered body substantially consisting of aluminum oxide,
High strength with a bending strength of 580 MPa or more and a toughness of 6 MPa
It has a high toughness of at least m ^1/2 and is highly reliable as a structural material.

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

[0040]

EXAMPLE Aluminum oxide (Al ₂ O ₃ ) powder (α-A
l ₂ O ₃ , purity 99.9%, average particle size 0.3 μm), Erinvar powder, Invar powder, Super Invar powder, stainless Invar powder,
42 Nickel powder, Kovar powder (average particle size 0.03 ~
50 μm range), magnesium oxide (MgO) powder (average particle size 0.05 μm) in a predetermined amount (% by weight) shown in Table 1, and kneaded in a ball mill made of aluminum oxide for 24 hours using purified water as a solvent. .

Then, 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 using the hot press sintering method, the pressure is 40MP in the carbon die.
A 90 mm × 60 mm × 10 mm sintered body was obtained under the condition a.

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 addition amount of various alloy particles, the addition amount of the sintering aid and the sintering conditions.

Table 1 also shows, as comparative examples, examples using S15C, TiC, and W as dispersed particles and examples sintering in a nitrogen gas atmosphere.

As the density, the relative density was measured by the Archimedes method. Regarding mechanical strength, JIS R160
A 4-point bending test was performed at room temperature in accordance with No. 1 and the bending strength was measured. Regarding toughness, SEP of JIS R1607
The fracture toughness value K _IC was measured by the method B at room temperature.

As shown in Table 1, the samples according to the examples of the present invention are excellent in all samples in terms of high bending strength of 580 MPa or more and high toughness of 6.0 MPam ^1/2 or more. It was confirmed that the samples corresponding to the comparative examples are particularly inferior in toughness as compared with the examples of the present invention.

[0048]

[Table 1]

[0049]

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. Its industrial utility is enormous.

Claims (2)

(57) [Claims] 1. An aluminum oxide is substantially a matrix phase, and the matrix phase has an average particle size of 0.05 to 30 μm.
At least one kind of spherical alloy particles selected from m of Erinvar, Invar, Super Invar, Stainless Invar, 42 nickel, and Kovar is dispersed in the range of 0.5 to 30% by weight , and the relative density is 98% or more. A metal oxide-dispersed aluminum oxide-based sintered body. 2. 0.5 to 30% by weight of at least one spherical alloy powder selected from Elinvar, Invar, Super Invar, Stainless Invar, 42 Nickel and Kovar having an average particle size of 0.05 to 30 μm and the balance substantially. Of a metal particle-dispersed aluminum oxide-based sintered body, which is characterized in that a mixed powder consisting of aluminum oxide powder is compacted and sintered in a temperature range of 1300 to 1420 ° C. in a vacuum or hydrogen gas atmosphere. Method.