JPH0380149A - Production of alumina/zirconia sintered body - Google Patents

Abstract

PURPOSE:To obtain the sintered body excellent in wear resistance and strength at high mass-productivity at low cost by mixing alumina, zirconia and a stabilizer and hot-pressing the mixture while regulating the atmosphere and temp. and sintering this mixture and thereafter heattreating it at the prescribed temp. higher than the hot-pressing temp. CONSTITUTION:A stabilizer (e.g. yttria) of zirconia is mixed with alumina and zirconia. Then the obtained material is arranged in the weakly oxidative atmosphere or the atmosphere and hot-pressed under the temp. conditions of 1100-1400 deg.C and sintered. An alumina/zirconia sintered body is obtained by heat-treating the sintered body at a temp. higher than the hot-pressing temp. and also not higher than 1500 deg.C in the weakly oxidative atmosphere or the atmosphere. Thereby manufacturing cost can be lowered because the sintered body can be hot-pressed at a low temp. not lower than 50 deg.C in comparison with the conventional calcination temp. and it is unnecessary that the ultrafine and expensive powder obtained by dissolution and coprecipitation is utilized as powder of a raw material.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing an aluminum-zirconia sintered body having excellent wear resistance and mechanical properties.

(Conventional technology) Alumina obtained by adding zirconia to alumina.
Improving the mechanical properties of zirconia sintered bodies is generally known, as typified by Japanese Patent Publication No. 59-24751.

Methods for producing such alumina-zirconia sintered bodies can be roughly divided into the following two types.

(1) As shown in JP-A-61-117153, powders of alumina, zirconia, ittria, etc. are crushed, mixed, molded, and sintered under normal pressure in air at a temperature of 1500 to 1650°C. .

(2) As shown in JP-A No. 61-58857, a powder containing alumina and zirconia with an average particle size of 1.0 μm or less is molded, calcined, placed in a graphite mold, and heated to 1500°C.
A method of sintering in a hot press for about 1 hour at a temperature of .

(Problem to be solved by the invention) However, in method (1), the sintering temperature is different for alumina and zirconia (zirconia is sintered at a lower temperature than alumina), and a compact of mixed and dispersed powder is simply fired. Then, due to the difference in sintering temperature.

Cracks occur between alumina particles and zirconia particles,
The disadvantage is that a high-performance aluminum/zirconia sintered body cannot be obtained. As a countermeasure to this problem, Japanese Patent Application Laid-Open No. 62-91419 discloses a method in which the components are dissolved once to make the mixture uniform and the sintering temperature is lowered by forming fine composite precipitates. A transition metal of 0.01 to 1 weight is added as a sintering aid to the entire powder composition containing fine alumina and zirconia of 1.5"/kg or more, and
Japanese Patent Application Laid-Open No. 62-59565 discloses methods that enable sintering at temperatures of 50 to 1500°C, but these methods have problems in terms of cost and performance, and are difficult to mold. be.

On the other hand, method (2) prevents cracks and provides a high-performance sintered body without defects, but the mold material that can be used at high temperatures of 1500°C or higher is limited to graphite.
Furthermore, when graphite is used, it has to be reduced and fired in a vacuum or neutral atmosphere in order to prevent oxidation, resulting in high costs.

As shown above, in conventional technology, it is known that adding zirconia to alumina improves performance.
Currently, the technology and manufacturing conditions for manufacturing it at a low cost like alumina sintered bodies have not been established.

The object of the present invention is to provide a method for producing an alumina-zirconia sintered body that does not have the above-mentioned drawbacks.

(Means for Solving the Problems) The present invention provides a method for producing an alumina-zirconia sintered body by sintering materials containing alumina, zirconia, and a zirconia stabilizer in a weakly oxidizing atmosphere or in a slightly oxidizing atmosphere. After hot pressing and sintering in the atmosphere at a temperature of 1100 to 1400 ° C.
This invention relates to a method for producing an alumina-zirconia sintered body that is heat-treated at temperatures below ℃.

As a stabilizer for zirconia in the present invention.

It is best to use ceria, ittoria, etc.

There is no particular restriction as long as it has the effect of stabilizing zirconia and produces tetragonal zirconia crystals. The content of zirconia shall be appropriately selected depending on the type and amount of the stabilizer. *There is no limit to the content of zirconia, but if mechanical and thermal properties and ease of hot pressing are taken into account, It is preferable to contain 15 to 30 volumes. Although zirconia contains Hf 02 as an impurity, it poses no problem when used.

On the other hand, alumina is preferably contained in the total composition by 50 volumes or more.

The material containing alumina, zirconia, and a zirconia stabilizer may be hot-pressed in the form of powder, or may be hot-pressed using a molded body of powder, with no particular restriction.

When using powder for materials containing alumina, zirconia, and zirconia stabilizers, mix and disperse each oxide or a powder that becomes an oxide at a temperature below the hot press temperature, or stabilize it with alumina powder. It is preferable to use a powder obtained by mixing and dispersing zirconia powder in which a curing agent is already dissolved. The average particle size of these powders is 0.3 to 1.
．． If it is 0 μm, it is favorable in terms of ease of handling and properties, and if the specific surface area is not more than so o o m2/ka, it is preferred because it is easy to mold.

The hot pressing conditions are not limited to 2%, but it is preferable to perform it in an atmosphere where the s 02 partial pressure is I x 102 Pa or more! IX 10"Pa ~ 3X 10'Pa
It is more preferable to carry out the reaction in an atmosphere within the range of . Further, it is preferable that the pressure in the hot press is 2 MPa or more, and it is even more preferable that the pressure is 5 MPa or more.

Hot pressing and heat treatment must be carried out in a weakly oxidizing atmosphere or in the air, and if hot press and heat treatment are carried out in an atmosphere other than this, there will be a drawback that the mechanical strength will be reduced.

The temperature of the hot press is 1100 to 1400°C.

Preferably, the temperature is in the range of 1250 to 1350°C.

If the temperature is less than 1100°C, sintering may become difficult,
It is not possible to sinter through the mold, and if the temperature exceeds 1400°C, the mold oxidizes and wears out, and the mold and sintered body tend to react, and furthermore, the zirconia in the sintered body grows grains and deteriorates its performance. This results in drawbacks such as a decrease in the amount of data and an increase in variation.

The heat treatment temperature is at a high temperature such as hot press temperature.

Furthermore, if the heat treatment is carried out at a temperature of 1500° C. or lower, which is equal to or lower than the hot press temperature, it becomes difficult to obtain stabilization of zirconia.The two objects of the present invention cannot be remotely related. Moreover, if the temperature exceeds 1500° C., grain growth of the alumina-zirconia sintered body becomes remarkable, and the mechanical strength deteriorates.

(Example) The present invention will be explained in detail below.

Example 1 Alumina powder (manufactured by Showa Denko, trade name 1608G) was added in an amount of 75% by volume (67 weight %) and zirconia powder (manufactured by Daiki Genso Kagaku Kogyo, trade name 5PZ) was 29% by weight.

Ittria powder (manufactured by Nippon Yttria, purity 99.9%)
Weighed 25 volumes of a zirconia component obtained by mixing 0.9 Dah by weight and ceria powder (manufactured by Nippon Yttrium, purity 99.913.1 Dah), and mixed it with a ball to an average particle size of 0.9 Dah.
The powder was wet-pulverized in an 8-μm case, mixed, and then dried to obtain a powder for hot press raw material. The specific surface area of this powder is 390
It was 0 m2/kg.

Next, the obtained powder was placed in a hot press mold made of silicon carbide with a diameter of 50INII11 (φ), and held for 30 minutes under the conditions shown in Table 1 (hot press temperature, pressure + OR partial pressure) to make it hot. It was pressed and then heat treated in the air at the temperatures shown in Table 1 to obtain an alumina-zirconia sintered body.

Thereafter, the obtained alumina-zirconia sintered body was cut to obtain a sample having dimensions of 3 x 4 x 40 mm. The bending strength of each of the five samples obtained was measured.

The average value was calculated. The results are shown in Table 1.

The bending strength was measured based on the standard of JIS R1601-1981.

No. table * indicates that the present invention does not include brass.

As is clear from Table 1, the alumina-zirconia sintered body of the present invention has excellent bending strength.

Example 2 The hot press raw material powder obtained in Example 1 had a diameter of 50 mm.
Place it in a 1n (φ) hot press mold made of silicon carbide.
Hot press was performed under the conditions shown in the table for 30 minutes.
Then, alumina-zirconia sintered bodies were obtained by heat treatment in the air at the temperatures shown in Table 2, and the bending strength was then measured.

Including the results, the 9th It is shown in Table 2.

An X mark indicates something not included in the present invention.

As is clear from Table 2, the alumina-zirconia sintered body of the present invention has excellent bending strength.

Example 3 Alumina powder, zirconia powder, ittria powder, and ceria powder (all used in the same manner as in Example 1) were weighed in the proportions shown in Table 3, pulverized and mixed, and then heated in the air at a temperature of 1300°C. Heat treatment was performed for 2 hours.

The powder was then pulverized until the average particle size became 0.4 μm to obtain a powder for hot press raw material containing a mixture of regular 10-gonal crystals and monoclinic crystals. The specific surface area of Nakako powder is 3200m”/
It was kg.

Next, the obtained powder was placed in a hot press mold made of silicon carbide with a diameter of 50 mm (φ), held for 30 minutes under the conditions shown in Table 3, and hot pressed. Alumina-zirconia sintered bodies were obtained by heat treatment at the temperatures shown in the table, and then the bending strength was measured. The results are also included in the third
Shown in the table.

Example 4 Alumina powder, zirconia powder, ittria powder, and ceria powder (all of which were used in the same manner as in Example 1) were weighed in the proportions shown in Table 4, and then subjected to the same steps as in Example 3 to obtain hot press raw materials. A powder for use was obtained.

Next, the obtained powder was placed in a hot press made of silicon carbide with a diameter of 50 mm (φ), held for 30 minutes under the conditions shown in Table 4, and then hot pressed under the conditions shown in Table 4. Alumina-zirconia sintered bodies were obtained by heat treatment at the indicated temperatures, and the bending strength was then measured. Including the results, the fourth
Shown in the table.

13 4- As is clear from Table 4, the aluminum zirconia sintered body according to the present invention has excellent bending strength.

As a comparative example, the hot press raw material powder obtained in Example 1 was placed in a hot press mold made of silicon carbide with a diameter of 50 holes (φ) and hot pressed at a temperature of 1450°C. The mold was oxidized and the mold and sintered body reacted.

In each example, the atmosphere during hot pressing was N.
A gas prepared by mixing 02 and 02 and adjusting the 02 partial pressure to p+ was introduced into an electric furnace attached to a press mold and used. The 02 partial pressure was adjusted by measuring the gas sucked in from near the press mold with a zirconia oxygen sensor.

(Effects of the invention) The alumina-zirconia sintered body obtained by the production method of the present invention can be hot-pressed at a temperature of 50°C or more lower than the conventional firing temperature, and the raw material powder is an ultrafine powder obtained by melting and co-precipitating. Since no expensive powder is used, the alumina-zirconia sintered body is inexpensive, excellent in mass production, and has excellent mechanical strength, making it extremely suitable for industrial use.

Claims (1)

[Claims] 1. In a method of producing an alumina-zirconia sintered body by sintering materials containing alumina, zirconia, and a zirconia stabilizer using a hot press, the material is sintered at a temperature of 1100 to 1400°C in a weakly oxidizing atmosphere or in the air. 1. A method for producing an alumina-zirconia sintered body, which comprises hot pressing and sintering, followed by heat treatment at a temperature higher than the hot pressing temperature and 1500° C. or lower in a weakly oxidizing atmosphere or air.