WO1993023347A1

WO1993023347A1 - Wear-resistant zirconia sinter and production thereof

Info

Publication number: WO1993023347A1
Application number: PCT/JP1993/000627
Authority: WO
Inventors: Hiroshi Ohnishi; Toshio Kawanami
Original assignee: Nikkato Corp.
Priority date: 1992-05-14
Filing date: 1993-05-12
Publication date: 1993-11-25
Also published as: JP2676008B2; JPH05319923A

Abstract

A wear-resistant zirconia sinter comprising a ZrO2-MgO sinter wherein: (i) the content of MgO is 6-10 mole %, (ii) the content of at least either CaO or Y2O3 is 0.2-2 mole %, (iii) the content of monoclinic ZrO2 is 50 vol. % or less, (iv) the bulk density is 5.55 g/cm3 or above, and (v) the diameter of the crystal grain is 4 νm or less. The invention can provide a zirconia sinter which is comparatively inexpensive and has an excellent wear resistance in every use thereof.

Description

Specification

Wear resistant zirconia sintered body and method for producing the same

Technical field

The present invention relates to a wear-resistant zirconia sintered body and a method for producing the same.

Background technology

Jirukonia (Z r 0 ₂₎ is heat-resistant member, oxygen sensors, it is widely used we as a raw material of Serra mission-box product heater first class.

Meanwhile, pure Jirukonia (Z r 0 ₂₎ is tetragonal from monoclinic when heated, transforms into cubic to the al, have the property that when this is cooling the reverse transformation occurs. In this case, the transformation from tetragonal to monoclinic involves a large volume expansion, and the sintered body is destroyed when cooled to room temperature. For this reason, stabilized zirconia or partially stabilized zirconia is adopted in the above various products. Stabilized zirconia is obtained by adding oxides such as calcia (Ca0), yttria (Y ^ 0), and magnesia (Mg0) to zirconia, and is cubic even at room temperature. Consists of The partially stabilized zirconia has a higher thermal shock resistance than the above-mentioned stabilized zirconia by allowing cubic and monoclinic to coexist.

However, these stabilized or partially stabilized zirconia A sintered body made of a material has good thermal shock resistance, heat resistance, etc., but has a relatively large porosity and a crystal grain size of more than 20 m. However, it has the drawback of poor abrasion resistance.

—On the other hand, recently, high-strength zirconia sintered bodies made of tetragonal zirconia have been developed. Unlike such stabilized zirconia, such a sintered body can exhibit excellent wear resistance.

However, the high-strength zirconia sintered body has a problem that the production cost is extremely high. In particular, ZrO

(2) High-strength zirconia sintered compacts of the Mg0 type require firing at 170 ° C or higher, and require a lot of time to control the cooling rate, heat treatment after firing, and so on an industrial scale. Not suitable for production at In addition, its wear resistance is excellent for some applications such as wire drawing dies, but it is not sufficient for all applications.

Accordingly, it is a main object of the present invention to provide a zirconia sintered body that is relatively inexpensive and can exhibit excellent wear resistance in all uses.

Disclosure of the invention

The object of the present invention is achieved as follows. In view of the above-mentioned problems of the prior art, the present inventor has focused on research. At the same time, a specific amount of magnesia, calcia and yttria is added to and mixed with the zirconia, and the raw material for molding is crushed to form a monoclinic crystal of zirconia. It was found that the amount, bulk density, and crystal grain size could be controlled, and further, it was found that a zirconia sintered body in which these values were controlled within a specific range exhibited excellent wear resistance. Completed the invention.

That is, the present invention provides the following wear-resistant zirconia sintered body and a method for producing the same;

In the M g O-based sintered body, - 1. Z r 0 ₂

(i) containing 6 to 10 mo 1% of MgO,

(ii) C a O and Y ₂ 0 ₃ of at least one 0. 2 containing 2 mol%,

(ill) monoclinic Z r 0 ₂ content is 5 0% by volume or less, there is (iv) a bulk density of 5. 5 5 g / cm ³ or more,

(v) the crystal grain size is 4 // m or less,

A wear-resistant zirconia sintered body characterized by this.

2. (a) M g O powder. 6 to 1 0 mol% and (b) C a O powder and Y _₂ 0 ₃ Z r 0 ₂ also have contains one 0.. 2 to 2 mol% powder least for the in 2. The method for producing a wear-resistant zirconia sintered body according to the above item 1, wherein the system powder is pulverized to a specific surface area of 3111 ng or more, then molded and fired.

3. the Z r 0 ₉ powder Batterai preparative ores or refining raw 3. The method for producing a wear-resistant zirconia sintered body according to the above item 2, using a material.

Abrasion resistance Jirukonia sintered body of the present invention, (i) M g O to 6 ~: L 0 contains mol%, (ii) C a 0 and Y _Q 0 ^ least 0.1 2 one of 2 containing mol%, (iii) monoclinic Z r 0 ₂ content is 5 0% by volume or less, there is (iv) a bulk density of 5. 5 5 g cm ³ or more, (V) grain It has the feature that the diameter is 4 m or less.

MgO is a component necessary for imparting wear resistance to the sintered body of the present invention. Therefore, when the above content is less than 6 mol%, the proportion of monoclinic zirconia increases, and a large number of microcracks due to transformation from tetragonal to monoclinic during the cooling process during firing occur. As a result, the wear resistance is reduced due to the presence of the microcracks, even if the collapse of the sintered body does not occur. On the other hand, if it exceeds 10 mol%, the proportion of cubic zirconia increases, and the crystal grain size increases. In this case, the wear resistance also decreases.

On the other hand, when trying to obtain a sintered body having a monoclinic amount, bulk density, and crystal grain size within the range of the present invention, the addition of MgO alone may cause the monoclinic to monoclinic in the firing step. It is very difficult to control the transformation to Therefore, such control is made as easy as possible, and a microstructure suitable for wear resistance For controlling, using a C a O and Y ₂ 0 ₃ 1 or even least for of the present invention. If the content is less than 0.2 mol%, the sinterability decreases, and the above microstructure cannot be obtained.If the content exceeds 2.0 mol%, the proportion of cubic zirconia increases. However, it is not preferable because the crystal grain size becomes large and the wear resistance is reduced.

The proportion (monoclinic amount) of monoclinic zirconia is less than 50% by volume. The monoclinic zirconia particles in the sintered body of the present invention are present at the grain boundaries and in the grains, and the monoclinic zirconia particles that have undergone volume expansion generate a compressive stress inside the sintered body. Contributes to the improvement of wear resistance. If the amount of monoclinic crystal is more than 50% by volume, the volume expansion will be excessive, and micro cracks will occur, reducing wear resistance. The zirconia other than the monoclinic crystal is preferably 80% by volume or less of cubic zirconia and 70% by volume or less of tetragonal zirconia in the sintered body of the present invention. The amount of the monoclinic zirconia was determined by polishing the surface of the obtained sintered body to a mirror surface and then performing X-ray diffraction analysis at a diffraction angle of 27 to

It was measured in the range of 34 ° and determined from the following formula from the monoclinic diffraction peak I _M , the cubic diffraction peak I c, and the tetragonal diffraction peak I _τ . M = [I MC111) + IM (111)] / [IM (111) + IM (llT) + I C + T (111)]

X recitation (Volume The cubic (c) and tetragonal (T) are measured in the range of 70 to 7 ° in the same way as the amount of monoclinic crystal is determined. And the height of the tetragonal diffraction peak I _τ were determined by the following equation.

C = [I C + T (111) [IM (IID + ΙΜ (ΙΙΪ) + i C + Tdll)] J ^X

[Ic (400) / I _C (400) + IT (400) + l T (004)] XlOOC volume

T = l 00-MC (volume ¾) The bulk density is 5.55 g Zcm ³ or more, preferably 5.60 g / cm ³ or more. If the bulk density is less than 5. 5 5 g Xcm ^u, correspondingly increases the number of pores, not properly desirable because tuna want to decrease the abrasion resistance.

The crystal grain size shall be 4 m or less. During cooling from the sintering temperature, volume expansion occurs due to the transformation from tetragonal to monoclinic, and a crack at the mouth is formed.However, when the crystal grain size exceeds 4 m, the microcrack density increases. It is not preferable because particles are detached on the surface of the sintered body due to impact or sliding, thereby reducing wear resistance. In the present invention, the crystal grain size is observed by a scanning electron microscope after polishing the surface of the obtained sintered body to a mirror surface and then performing thermal etching or chemical etching. Then, an average of 10 points is obtained by the intercept method. The calculation formula was D = l.5Xn / L (D: average crystal grain size, !!: number of crystals per length, L: measured length).

Next, a method for producing a wear-resistant zirconia sintered body of the present invention will be described. First, the above-mentioned predetermined amounts of powder of magnesium, yttria, and potassium lucia are added to the zirconia powder. The type of zirconia powder is not particularly limited, and for example, zirconia purified from zircon sand can be used.Battery ore or its refined raw material can be used from the viewpoint of cost. More preferred. It is preferable that the particle size of the zirconia powder is usually about l to 5 wm. Further, as magnesia powder, powder of magnesium hydroxide, magnesium carbonate, magnesium salt, etc. may be used in addition to magnesia. The magnesia powder preferably has a particle size of usually about 0.5 to 2 am. As the powder of yttria and lucia, powders of hydroxide and carbonate of yttrium and calcium can be used in addition to yttria and lucia. It is preferable that the particle size of the italian powder and the raw lucia powder is usually about 0.5 to 2 m.

These raw materials are mixed and pulverized to form a molding powder. In this case, mixing and pulverization may be performed in accordance with a conventional method, for example, pot milling or abrasion in water or an organic solvent by a wet method. This can be performed using a pulverizer such as a mill. In this case, if necessary, after drying, it may be calcined at about 110 to 140 ° C., pulverized again, dispersed, and dried to obtain a powder for molding. The powder for molding has a specific surface area of 3 m ² Zg or more. If the specific surface area is less than 3 m "Zg, the sinterability deteriorates, which is not preferable.

Next, the above-mentioned molding powder is molded into a predetermined shape. In this case, as a molding method, various known molding methods such as, for example, injection molding, injection molding, extrusion molding, and press molding (CIP, HIP) can be employed as they are.

Thereafter, the obtained molded body is fired according to a conventional method. The sintering temperature is usually about 140 to 170 ° C, preferably about 150 to 160 ° C. As described above, the wear-resistant zirconia sintered body of the present invention is obtained.

According to the production method of the present invention, a zirconium sintered body having a specific structure can be obtained relatively easily.

The zirconia sintered body having a specific structure can exhibit excellent wear resistance in practically all uses. In particular, (a) It has excellent wear resistance under high load due to its excellent strength, toughness and impact resistance, and (mouth) It has excellent wear resistance under high-speed conditions because of its excellent thermal shock resistance. . Also, despite its excellent wear resistance, it has a low elastic modulus compared to aluminum etc., so it does not easily damage the mating material. Furthermore, when the sintered body of the present invention is used as a pulverizer member, there is almost no mixing of abrasion powder, and even if the abrasion powder mixes with the material to be pulverized, the generated abrasion powder is generated. Since they are very fine, they do not substantially impair the uniformity of the material to be ground.

The abrasion-resistant zirconia sintered body of the present invention, which can exhibit such excellent effects, is most suitable for various uses such as crushing balls, lining materials, crushing containers, nozzles, rollers, gauges, dies, and the like. .

Examples and comparative examples are shown below to further clarify the features of the present invention.

Examples 1 to 9

Zirconia raw material with an average particle size of 1.0 m, magnesia or magnesium carbonate with an average particle size of 0.5 // m, and calcium or yttria or its salt are shown in Table 1. The resulting mixture was mixed into a pot mill, and the mixture was pulverized until the specific surface area became 8 m / g to obtain a molding powder. Incidentally, Jirukonia raw material, in Example 1, 3, 5 and Batterai DOO For the _{8 (Z r 0 n 9 9} . 5%, S i 0 2 0. 2%, A 1 2 0 3 0. 0 1% ) And zirconia raw materials purified from zircon sand. 0

Next, the molding powder is formed into a ball having a diameter of 15 mm at a pressure of 1 ton / cm ² by an isostatic press molding method (CIP), and the formed body is heated at a temperature of 1450 to 170 ° C. Fired. After firing, the ball was barrel-polished to obtain a ball made of the wear-resistant zirconia sintered body of the present invention. This sintered body, a bulk density (g ZCM ^u), were examined for grain size (fi m), monoclinic Akiraryou (volume) and wear rate (%). The results are shown in Table 1. The wear rate was measured by the following method.

Wear rate> 2 liters of aluminum pot mill (alumina purity)

9 296), 1 kg of the sintered body ball of the present invention and 0.8 liter of water were put into it, and subjected to a slip test at 100 rpm for 48 hours to reduce the weight of the ball after the test. The ball was evaluated as a percentage () of the weight of the ball before the test.

table 1

NO. MgO γ ₂ 0 ₃ CaO bulk density grain size monoclinic Akiraryou milling rate

(Mol%) (mol 5 (mol) g / cm ³ ) (volume (%) Example 1 9.0 0, 5 5.73 1, 6 40 1.3 Example 2 9.5 0.5 5. 65 3.5 5 25 2.4 Difficult 3 8.5 0.5 0.5 1. 0 5.63 3.8 8 2.0 Difficult 4 8.0 1.0 5.68 1. 9 45 1, 6 Difficult Example 5 9. 0 1. 0 5. 74 2. 0 30 1.2 Difficult 6 9.0 0 0.5 5. 62 2. 8 35 2.2

7. 0 1. 5. 5. 65 1, 8 28 1.6 Dislike 8 9. H 1. 5. 5. 70 3. 5 1. 9 Example 9 8. 5, 0 1. 0 5. 66 2.8 15 2.0 1

Table 1 shows that the wear-resistant zirconia sintered body of the present invention exhibits excellent wear resistance due to the structure unique to the present invention. Comparative Examples 1 to 7 Sintered balls were manufactured in the same manner as in the example except that the compositions were as shown in Table 2, and the characteristics were examined. The results are shown in Table 2. Incidentally, Jirukonia raw material, Comparative Example 1, 3, 5 and 7 Batterai you for the other (Z r 〇 _{2 9 9. 5%, S i} 0 9 0. 2%, A 1 2 0 3 0. 0 1%) The other materials used were zirconia raw materials purified from zircon sand.

Table 2

From Table 2, it can be seen that each ball of the comparative example has a raw material composition out of the range of the present invention, and thus does not have a sintered body characteristic peculiar to the present invention and is inferior in wear resistance.

Claims

The scope of the claims

In M g 0-based sintered body, - ① Z r 0 ₂

(i) containing 6 to 10 mol% of MgO,

(ii) C a O and Y. 0. Contains at least one of 0.2 to 2 mol%

(iii) monoclinic Z r 0 ₂ content is 5 0% by volume or less, there is (iv) a bulk density of 5. 5 5 g / cm ³ or more,

(V) the crystal grain size is 4 m or less,

A wear-resistant zirconia sintered body characterized by this.

② (3)] ^ 0 powder. 6 to 1 0 moi% and (b) C a O powder and Y ₂ 0 ₃ Z r 0 where at least the powder having including one 0. 2~ 2 mol%. It is characterized by pulverizing the system powder to a specific surface area of 3 Zg or more, then molding and firing

(i) M g O 6-: containing L 0 mol%,

(ii) C a O and Y ₂ 〇 ₃ of at least one 0.2-2 containing mol%,

(iii) monoclinic Z r 0 ₂ content is 5 0% by volume or less, shall apply in (iv) the bulk density is 5 · 5 5 g Xcm, ° or more,

(V) the crystal grain size is 4 m or less,

A method for producing a wear-resistant zirconia sintered body.

③ Z r 0 ₂ Made in powder and to Batterai preparative ore or wear resistant Jirukonia sintered body according to claim 2, wherein using the purified raw material Three

Construction method