JPS62275058A - High toughness zirconia base ceramics and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention The present invention relates to a high-toughness zirconia-based ceramic and a method for producing the same, and provides a highly tough zirconia-based ceramic and a preferred method for producing the same. The aim is to make this product widely available for various high-strength parts.

Industrial applications Zirphea ceramics whose main component is zirconium oxide (ZrOl) and their manufacturing technology.

Conventional technology Zirconia ceramics have excellent dielectric constant, etc.
L7 is widely used in cutting tools, sensors, etc. due to its excellent electrical properties, hardness, toughness, and corrosion resistance. Especially recently, it is being used for cutlery and machine parts, taking full advantage of its high toughness and strength. By the way, it is well known that the toughness value of such ceramics improves depending on the amount of alumina added to the ceramics, and it is well known that the toughness value of such ceramics is improved by changing the amount of alumina added to the ceramics.
,:ZrO,=90~80 wt%:10~2Q w
The bending strength is close to that of alumina in the t% range, but
Mechanistically, it is thought that the partially stabilized 9-zirconia is appropriately dispersed in the alumina ceramic matrix, and the stress relaxation mechanism, which is a characteristic of the partially stabilized Zirphere, acts on the generated cracks.

However, as the amount of zirconia added increases, the internal pressure within the phase during Sisera glass sintering and cooling increases due to the differences in thermal properties such as thermal expansion coefficient and thermal conductivity between alumina and zirconia. As is known, the stress relaxation properties of partially stabilized zirconia are exhausted during cooling, resulting in not only a significant decrease in toughness value but also a decrease in bending strength. Japanese Patent Publication No. 60-251171
In the publication, the composition range of zirconia is 10 to 40 m0.
6%, 1 is in the vicinity of the conventional range of high toughness alumina-zirconia, and basically the increase in internal pressure during firing and cooling of the alumina-zirconia ceramic glass mentioned above is beyond the conventional range. This shows that the composition range of zirconia is 40 mot% (44%).
wt%), the hardness decreases and, as a result, it cannot exhibit a hardness higher than that of alumina ceramics.

The attached drawing, Figure 4, is a data diagram regarding the strength and toughness values of high-toughness alumina-zirconia ceramics, which is quoted from the technical catalog of MEL Ltd. in the UK. 21wt
%) is the maximum amount of zirconia added, and the composition is the same as described above. Furthermore, JP-A No. 61-26561
It has been announced that ceramic powder is first melted at a temperature exceeding 2000°C, cooled, and then shaped and fired by a conventional method.

Problems to be Solved by the Invention However, even if the above-mentioned conventional techniques have certain effects, it is clear that they still have various problems. In other words, even though improvements and innovations have been made in the past as described above, in terms of toughness, for example, conventional ceramic glass is considerably inferior to competing materials such as metals and glasstex. It's obvious. Also, those used as high-strength, high-toughness Zilfair ceramics contain Y, O, t- as a stabilizer.
It is common to add 3 to 10%, usually 5 to 6%.
%, the strength properties are excellent, but since Y and 05ti used in this case are rare resources, even this small amount of addition makes the ceramic expensive.

Zirconia content increases from 40 to 60 m06% (44
~66 wt%), it is clear that the hardness decreases.

The method disclosed in Japanese Patent Application Laid-Open No. 61-26561 requires melting and cooling at 2000° C. or higher, followed by further molding and firing, which also results in high costs.

Means for solving the tank bottom problem of the invention Alumina 5-4 Q wt%, Zirconia 90-5 Q
High toughness zirconia ceramics and alumina powder 5 to 4, which are sintered bodies containing 2 to 4 wt% of ittria and 2 to 4 wt% of ittria, and characterized in that the average diameter of the alumina is 5 times or more the average diameter of the zirconia. Q wt%, zirconia powder 90-5
using 0 wt% and 2-4 wt% of intoria flour,
Moreover, the high-toughness zirconia ceramic is produced by uniformly mixing raw material powders in which the average diameter of the alumina powder is 5 times or more than the average diameter of the zirconia powder, molding and drying, and then firing at 1500 to 1650°C. manufacturing method.

Action Silconi 7 minutes 90-50wt% and alumina content 5-40w
By adding t% in a dispersed manner, the toughness value is preferably improved.

As mentioned above, by using the alumina component, the amount of zirconia and yttoria used per unit volume or weight of the ceramic can be reduced, and the cost of the product can be reduced.

By mixing alumina and itria with the above-mentioned zirconia content range, high hardness and toughness can be obtained, and the bending strength is also comparable to that of 100% zirconia.

By setting the alumina content to 10% or more, the point of action on the crack-generating crank is substantially satisfied, and by setting the alumina content to 40% or less, zirconia ceramics can be appropriately obtained as a matrix, and costs can be reduced.

By setting the ittria content to 12 wt% or more, Zylfair is stabilized and mechanical strength is increased, and by setting the ittria content to 4 wt% or less, the cost of the product can be reduced.

EXAMPLE The present invention was created through repeated research and speculation in order to solve the problems of the conventional products as described above. We have solved this problem and succeeded in manufacturing and supplying alumina-zirconia ceramics at low cost, which have almost the same high strength as Zirfea, and also have higher toughness and hardness than zirconia ceramics.

That is, in the present invention, the toughness value is appropriately increased by dispersing and adding alumina in a specific range, and in addition, zirconia,
The general aspect of the bending strength of the product according to the present invention is shown in Figure 1, and the toughness is shown in Figure 1.
The hardness is as shown in Fig. 3, and the bending strength is similar to that of zirconia as shown in Fig. 1, and as shown in Figs. 2 and 3, 100 wt% zirconia.
higher toughness values (K, c) and hardness I than ceramics of
I (Fly). This was achieved by discovering that alumina that acts on generated cracks without damaging the zirconia matrix must satisfy certain conditions. That is, if the amount of alumina added is less than 10%, there will be insufficient points of action for the generated crank, approaching K■C9Hv Hazirconia ceramics, and if it is too large (40% alumina).
Above) The zirconia ceramic matrix is insufficient as a whole, and the internal pressure cannot be increased.
This will reduce the strength.

The alumina powder is preferably calcined in advance at 1500°C or higher,
Alternatively, the molten material is cooled and then crushed. i.e. 1500
If it is below ℃, it becomes reactive and absorbs zirconia and reactive leitria during firing, which is undesirable.
When melted at a temperature above the melting point (2400° C.), it becomes a single crystal, the impurities contained therein are discharged, and it becomes chemically stable, which is preferable. 'd! It is desirable that the particle size of the alumina powder is 3QIXn or less (50% uniform particle size) and at least 5 times, preferably 5 to 15 times, the particle size of the zirconia powder. That is, if it is 5 times or less, less tetragonal crystals will be formed among the zirconia present in the produced zirconia-based ceramics, and the mechanical strength of the fired ceramics will be insufficient, which is undesirable. If this is the case, large racks tend to form around the alumina grains, resulting in a decrease in mechanical strength.

To make the heavy metal content of zirconia 90 to 50 wt%,
This is because a high internal stress occurs in the combination of zirconia and alumina, resulting in high mechanical strength.If it is less than 50wt% or more than 9wt%, it is inferior as shown in Fig. 2.3. It's like this.

Itria is added to stabilize zirconia, and is essential when obtaining a mechanically strong at-zirconia ceramic glass. In particular, it is desirable that the crystalline form is partially stabilized, and therefore K needs to be added in an amount of 5 to 15% relative to zirconia, but according to the present invention, the content of zirconia is As a result, the addition of IJT, which is a rare resource and is expensive, can be kept low.

The preparation and molding of the raw material powder can be done in the same way as normal ceramic manufacturing methods, but what about pressure molding and extrusion molding? It is more preferable to use a molding material such as lipinyl alcohol or methyl cellulose.

To describe the effects of the present invention described above, first, by adding a predetermined amount of selected alumina, a ceramic with higher toughness than zirconia ceramics can be obtained. The increase in manufacturing costs due to the addition of rare earth elements is due to the fact that the addition of alumina results in a decrease in the content of zirconia in the fired ceramic packaging, which in turn results in a decrease in the amount of rare earth elements. , is reduced. Resources can be reused by pulverizing defective products that occur in the Mayu alumina porcelain manufacturing factory and products that are damaged during use and into a predetermined particle size.

A specific manufacturing example of the product according to the present invention will be described below.

Production Example 1 Norconia powder with an average particle size of 0.7 μm and IJT were added to melted and pulverized alumina with an average particle size of 4 to 8 μm, and the mixture was mixed in a coarse mill. During the mixing, 0.5 part of starch powder and P are used as organic binders.
0.5 part of VA was added in advance to 100 parts of raw material powder. This was press-molded at a bottom pressure of 5ooky/at to obtain a molded plate with dimensions of 1100x25x4, and heated at 1600°C.
The firing process was performed for 2 hours. This obtained piece SoJI
The bending strength (σB) was measured using the S1601 method, and the toughness value (KIC) and hardness (Hv) were also measured using the method described below. The results are shown in Tables 1 to 4 of Table 1, where σB,
Both KIC and HV showed high values, and toughness value (Krc)
Fi vine = + = Acela d-nx value 6.5MN/m 2
It exceeds. The toughness value was measured by the indentation method and by an MI7 Vikers hardness meter.

Comparative Example 1 As alumina powder, LS-23 manufactured by Kuchigaru Kako Co., Ltd., average particle size 0
．． A fired ceramic was obtained and measured under the same conditions as Production Example 1, except that a ceramic having a diameter of 6 μm was used.

The obtained results are shown in &10 to 13 of Table 1. 2) ζ Compared to the above production example (ml-4) according to the present invention, σ
The B value is generally 1/2 or less, and the KIC value also does not reach 1/2. Moreover, the hardness is H
V is inferior by about 100 to 200 ky/ad,
It is clear that the manufacturing examples of the present invention are greatly improved in any case.

Production Example 2 As alumina powder, LS-23 alumina fr manufactured by Kuchigaru Kako Co., Ltd., which was heat treated at 1600°C and 1800°C and then crushed, was used, zirconia powder and hyttria powder were added, and +3Hrs- was mixed with Lumil. After, 650IKIi
/cd to form a 100X25X4 plate and then. During the mixing, 0.5 parts of methylcellulose was added as a molding binder to 100 parts of the raw material powder. The obtained molded body was fired at 1650°C under IHr to obtain fired ceramics. The obtained results i1 are shown in column 5.6 of Table 1 above.

Comparative Example 2 Alumina A31 manufactured by Nippon Light Metal Co., Ltd. (α-alumina with an average particle size of 5 am) was used as the alumina powder, and a fired ceramic was obtained and measured under the same conditions as in Production Example 1 except for the sinter.

The results obtained are shown in columns 7 to 9 of Table 1 above. In other words, the inventive manufacturing example with a flatness of 5.6 and this comparative example are the same in terms of the number of combinations, and the Keta comparative example is higher in terms of Ittria, but the bending strength σB is generally higher. It can be said that the toughness of the example manufactured according to the present invention is about twice as high as that of the example manufactured according to the present invention, and the toughness value KIC
However, it is more than twice as large, and the hardness is HV, which is 200kl.
The value of the present invention is about il/cIIt.

"Effects of the Invention" According to the present invention as explained above, hardness is high;
It is possible to obtain ceramics that are excellent in both strength and toughness, and the desired product can be obtained at a relatively low cost, making it an invention that has great industrial effects.

[Brief explanation of the drawing]

The drawings show the technical content of the present invention, and Figures 1 to 3 are charts summarizing changes in mechanical properties due to changes in the amount of zirconia in alumina, and Figure 1 shows changes in bending strength, FIG. 2 shows toughness values, FIG. 3 shows changes in hardness, and FIG. 4 is a chart of characteristic values of conventionally known alumina-zirconia ceramics.

Claims (1)

[Claims] 1 Alumina 5-40wt%, zirconia 90-50w
t% and 2 to 4 wt% of indria, and the average diameter of the alumina is 5 times or more the average diameter of the zirconia. 2. The high-toughness zirconia-based ceramic according to claim 1, wherein the alumina is previously heat-treated at a temperature of 1500° C. or higher. 3 Alumina powder 5-40wt%, zirconia powder 90-5%
Raw material powders using 0wt% and 2 to 4wt% of ittria powder and in which the average diameter of the alumina powder is 5 times or more the average diameter of the zirconia powder are uniformly mixed, molded and dried, and then heated at 1500 to 1650°C. A method for producing high-toughness zirconia ceramics, which involves firing. 4. The method for producing high-toughness zirconia ceramics according to claim 3, wherein alumina is heat-treated at a temperature of 1500° C. or higher in advance.