JPS60100646A - High toughness sintered body of ceramic - Google Patents

Abstract

PURPOSE:To obtain a sintered body of ceramics having superior toughness by dispersing a specified amount of an oxidation resistant alloy having a specified average particle size in a sintered body of ceramics. CONSTITUTION:An oxidation resistant alloy having <=0.5mum average particle size is dispersed in a sintered body of ceramics such as zirconia or alumina by 0.5- 6wt%. An alloy consisting of, by weight, 0.1-0.2% C, 5-20% Cr, 3-10% Mo, 3-10% W, 2-5% Al, 2-5% Ti and the balance Ni or Co is used as the oxidation resistant alloy. A sintered body having superior oxidation resistance and strength at high temp. as well as improved toughness is obtd.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a high-toughness ceramic sintered body, and in particular to ultrafine powder of zirconia and alumina, which is formed by adding ultrafine powder of an oxidation-resistant alloy as a binder. This invention relates to a ceramic sintered body with excellent toughness that is obtained by sintering.

[Background of the invention]

Conventionally, heat-resistant alloys have been widely used as materials used in high temperatures and corrosive gas atmospheres. Heat-resistant alloys have a limited use temperature. Therefore, there is a growing trend to use ceramics in fields where it is impossible to use metal materials.

For example, structural members for gas turbines and engine parts are made of ceramics. Ceramics are heat resistant.

Although it has excellent corrosion resistance, it has the major drawback of being extremely brittle. Therefore, various studies are currently being conducted to overcome this drawback. One possible way to overcome this problem is to combine heat-resistant and corrosion-resistant ceramics with tough metals. For example, as disclosed in Japanese Patent Publication No. 54-8371 (Metal Ceramics), a metal ceramic containing a high melting point oxide and a metal chromium is disclosed, where the high melting point metal oxide is made of metal chromite. ing. Furthermore, as shown in Japanese Patent Publication No. 52-4564, metal molybdenum and tungsten are added to alumina to make it tougher. However, conventional techniques have not yet sufficiently overcome the toughness of ceramics.

Furthermore, the drawbacks of ceramics such as zirconia and alumina are that they are significantly more brittle than metals and have poorer thermal shock resistance. A material called cermet has been generally known as a material made by adding a tough metal to ceramics to strengthen it. This cermet can be used as a binder for metal oxides, carbides, silicides, etc.
It is a type of composite material to which metals such as Co and Ni are added. This is used in mechanical cutting tools. However, this cermet has the disadvantage that a large amount of metal as a binder is added, and the properties inherent to ceramics are lost.

[Purpose of the invention]

An object of the present invention is to provide a strong ceramic sintered body which has improved brittleness in a sintered body mainly composed of ceramics such as zirconia and alumina.

[Summary of the invention]

In particular, the ceramic sintered body according to the present invention has 0.5 to 6% by weight of an oxidation-resistant alloy having an average particle size of 0.5 μm or less dispersed in the zirconia and alumina sintered body. It is characterized by

In particular, the present invention provides a ceramic sintered body with an average grain size of 0.5
It is characterized by the addition of ultrafine powder of an oxidation-resistant alloy of micrometers or less as a binder.

An important factor in making ceramics tough is the size of the ceramic and metal powders that serve as important starting materials. It is generally known that the finer the average particle size of ceramics, the better the toughness of the sintered body. This is because the contact area between powders increases during sintering, making sintering easier. The sintered body thus obtained has finer crystal grains, an increased relative density, and fewer internal defects.

On the other hand, as a method for improving the toughness of a dense sintered body, an appropriate amount of tough metal powder is added. In this method, the metal acts as a crack arrester or buffer, and it is fully expected that the degree of crack propagation can be reduced and toughness can be improved.

However, when the amount of metal powder added exceeds a certain level, although the toughness is improved, the strength decreases and the original characteristics of ceramics are lost. In addition, the metal powders come into contact with each other and coagulate, and the effect of improving toughness is no longer exhibited. This is because the metal particles coagulate between the ceramic powders during the sintering process after forming the mixture of ceramic powder and metal powder, thereby forming voids between the ceramic particles. These voids serve as starting points for stress concentration and reduce toughness.

The present inventors have discovered that by mixing ceramic grains and metal powder with varying average particle diameters, the mixed powder is molded and sintered, and the sintered body becomes dense. Furthermore, in order to improve the toughness, it is preferable to add metal powder of 0.5 μm or less to the ceramic powder in a weight ratio of 0.5 to 6 times. When metal powder with an average particle size of about 0.5 μm or less is added to ceramics with an average particle size of several μm or more,
Metal powder tends to aggregate in the voids where ceramics come into contact with each other. When such a powder compact is fired, when the aggregated powder is sintered or melted and solidified, small voids remain at the boundaries of the ceramic particles. , a dense sintered body cannot be obtained and the toughness deteriorates. That is, in order to improve toughness by adding metal powder τ to ceramic powder, the key point is to use finely divided ceramics and metal powder to disperse the metal powder finely and uniformly in the matrix. Furthermore, the present invention is a ceramic in which ultrafine powder of an oxidation-resistant alloy with excellent leakage properties is added to zirconia and alumina, such as a Ni-based alloy containing Cr and having improved oxidation resistance, or a Co-based alloy. There are characteristics.

As a 1'Ji-based alloy, C: 0.1 to 0.2 in weight ratio
%, Cr: 5-20%, Mo: 3-10%, W
: 3 to 10%, J, t: 2 to 5%, 'pi: 2 to 5%, and the balance is preferably Ni.

Further, as a Co-based alloy, C: 0.1 to 0.2%.

Cr: 5-20%, Mo: 3-10%, W: 3
-10%, At: 2-5%, Pi: 2-5%, and the balance is preferably CO. In such Ni-based alloys or Co-based alloys, they contain At and Ti or their oxides, which improve the strength and toughness of the sintered body. The reason why the chemical compositions of the Ni-based alloy and Co-based alloy, which are oxidation-resistant alloys, are limited as described above will be described below.

Cr: 5 to 20% Cr is an element that improves the oxidation resistance of Ni and Co groups, and its effect is small when it is less than 5%, but its effect is saturated when it exceeds 20%, so the upper limit is set to 20%. And so.

C: 0.1 to 0.2 qb C is an element effective in strengthening Ni-based alloys and Co-based alloys by forming oxidation-resistant solid carbides, and the amount added is 0.1 to 0.2 qb. Section 2 is appropriate.

MO: 3 to 10 g, W: 3 to 10 g6 Mo and W are effective elements for improving oxidation resistance.
If it exceeds 0%, its effect will be saturated and it will be economically unfavorable since it is an expensive element. Therefore, the amount of MO and W was limited to 3 to 10 inches.

At: 2 to 5%, Ti: 2 to 5% At and Ti have good wettability with ceramics and are effective for toughening, but if it is less than 2%, it is ineffective, and if it is more than 5%, the oxidation resistance deteriorates, so At , Ti were both limited to 2 to 5%.

Remaining Nl: Remaining C0 Note that 3 to 10% of Co is added to the Ni group, and 3 to 1% of Co is added to the Co group.
Addition of 0% Ni significantly improves oxidation resistance. Ni-based alloys and Co-based alloys with such chemical compositions are made into ultrafine powder (average particle size 0.05 μm) by evaporation.
It is easy to manufacture. Especially Rene'80 (
C:0.17. Co:9.5. Mo+W: 8+ A
t: 3. Ti: 5. Cr:14. The remaining Ni has good oxidation resistance and is therefore effective as a binding material for zirconia and alumina.

[Embodiments of the invention] <Example 1> Zirconia powder with an average particle size of 0.03 μm (3wt/.

partially stabilized with Y2O3) with a particle size of 0.05 μm.
Each Ni-based heat-resistant alloy (lene'
3Q) The powders were mixed using a mechanical mixing method (for example, using a milling machine and a centrifugal ball mill), and intermediate compacts were formed from each mixed powder using a press. When producing this mixed powder, the metal powder relative to zirconia was kept constant at 3w10. Each intermediate compact was then sintered at 1500c under high vacuum of 10'-') or more. 3 MX 4 from each sintered body
A test piece of MX 30 rent was cut out, polished to a mirror surface, and then subjected to a four-point bending test. The test was conducted on 30 pieces each, and the average value was calculated.

The results are as shown in FIGS. 1 and 2.

Figure 1 shows the bending strength, and Figure 2 shows the bending strength after making an impression of 4 under a load of 20 using a Vickers hardness tester. As is clear from FIG. 1, there was a slight decrease in the average metal particle size up to 0.5 μm, but as the average metal particle size further increased, the bending strength tended to decrease. In Figure 2, the sintered body to which metal powder with an average particle size of 0.05 μm is added has a sintered body of about 6 h /
rta 2 also showed a high value. This suggests that the zirconia sintered body containing fine metal powder has excellent toughness.

In other words, a plain zirconia sintered body with small defects on its surface would easily break due to a small external force, whereas a zirconia sintered body with fine metal powder added could withstand an external force about 25% higher. can. To confirm this, an indentation was made on each sintered body using a Vickers hardness tester, and the stress intensity coefficient KC was calculated from the relationship between the load and the scraped length using the following formula.

Here, P is the Vickers indenter load, φ is the angle of the Vickers indenter tip, and C is the crack length. FIG. 3 is a diagram showing the relationship between the particle size of metal powder and the KC value calculated from the above. As shown in the figure, the same tendency as the bending strength shown in FIG. 2 was observed.

A sintered body containing metal powder with a particle size of 0.05 μm exhibits a KC that is about 15 times that of a sintered body made of simple zirconia, and it significantly decreases when the particle size is 2 μm or more. The state of cracking was observed when a diamond indentation was made on the sintered body using a Vickers hardness tester. The crack length in a sintered body made of single zirconia is determined by the average grain size O according to the present invention,
It was confirmed that the crack length in the longitudinal direction of sintered body B containing OSμm metal powder was larger, and that the crack length of the sintered body of the present invention was about half that of the conventional sintered body. .

For improving the brittleness of zirconia sintered bodies, it is effective to use metal powder with an average particle size of 0.5 μm or less based on the above.

Next, the average particle size of KNi-based heat-resistant alloy powder was kept constant at 0.05 μm, and the amount added was varied. After the metal powder was dispersed in zirconia, the mixed powder was molded, and then sintered. A sintered body was produced. A test piece was prepared from this sintered body as described above and subjected to a bending strength test. In the bending test, an indentation was made using a Vickers hardness tester, and then a bending test was performed.

FIG. 4 shows the relationship between the amount of metal powder added and the bending strength of the sintered body. As is clear from the figure, the metal powder is
The bending strength increased when wt 10 or more was added, and reached the maximum when the amount added was 2.5Wt10, and the strength tended to decrease when more than that amount was added. Therefore, the amount of metal powder added is preferably in the range of 0.5 to 6%. The reason for this is that the fine metal powders come into contact with each other, causing the fine metal powders to coagulate and enlarge.

As a result of observing an optical micrograph of a sintered body to which 7.5 W tlo of metal powder was added, it was found that the metal powder aggregated and enlarged in the matrix. Therefore, the bending strength of the sintered body decreases.

Therefore, in order to increase the toughness of zirconia, metal (R
The ultrafine powder of ene' 130) is 0.5-6Wt10
It is important that the zirconia sintered body be uniformly dispersed in the matrix of the zirconia sintered body within this range.

As described above, it has been found that toughness can be improved by dispersing 0.5 to 6W10 of ultrafine metal powder having an average particle size of 0.5 μm or less in zirconia. Alumina (AI40m) was also tested in the same manner as in this example, and the present invention was also found to be effective in improving the brittleness of alumina. Therefore, it is clear that similar effects can be expected even if ultrafine powder is added to other ceramics such as SjC and 5j3N4. It is possible to produce the ultrafine powder in the present invention based on the current state of the art, and it is very effective to add the ultrafine powder of the Ni-based oxidation-resistant alloy used in this example.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to improve the toughness of a sintered body mainly made of ceramics such as zirconia and alumina, and the sintered body has excellent high-temperature oxidation resistance and high-temperature strength. It is possible to provide a dog with its effects.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the particle size of metal powder and bending strength. Figure 2 is a diagram showing the relationship between particle size of metal powder and bending strength of the sintered body after Vickers indentation. Figure 3 shows KC with respect to the particle size of the metal powder. Figure 4 is a diagram showing the relationship between the amount of ultrafine metal powder added and the bending strength after diamond indentation. Agent Patent Attorney Tatsuyuki Unuma Rice Grain Diameter (J, LTn Sumo 3rd Rice Grain Diameter

Claims (1)

[Claims] 1. In the sintered body made of ceramics, the average grain size is 0,
A high-toughness ceramic sintered body, characterized in that an oxidation-resistant alloy having a diameter of 5 μm or less is dispersed in a weight ratio of 0.5 to 6. 2. In claim 1, the oxidation-resistant alloy has a weight ratio of C: 0.1 to 0.2% and Cr: 5 to 20.
Chi, Mo: 3-10 chi, W: 3-10%, A4: 2-s
A high toughness ceramic sintered body characterized by comprising: s, Ti:z~5% and the balance Ni. 3. In claim 1, the oxidation-resistant alloy has a weight ratio of C: 0.1 to 0.3% and Cr: 5 to 20.
Chi, Mo: 3-10 chi, W: 3-10%, At: 2-s
A high-toughness ceramic sintered body characterized by comprising: s, Ti: 2 to 5 ti and the balance being CO.