JP2003314556A - Bearing of zirconia sinter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing made of zirconia sinter having excellent thermal stability, anti-corrosiveness and abrasion resistance. <P>SOLUTION: (a) It is mainly Y<SB>2</SB>O<SB>3</SB>based tetragonal zirconia sinter and (b) mole ratio of Y<SB>2</SB>O<SB>3</SB>/ZrO<SB>2</SB>is in the range between 1.5/98.5 to 4/96 and (c) SiO<SB>2</SB>is contained in the range of 0.05 of 2.5 weight % and (d) Al<SB>2</SB>O<SB>3</SB>is contained in the range of 0.05 to 3.0 weight % and (e) the average crystal diameter is less than 0.7 μm and (f) SiO<SB>2</SB>(weight %) × average crystal diameter (μm) is in the range of 0.03 to 0.5 and (g) weight ratio of SiO<SB>2</SB>/(total of Na<SB>2</SB>O, K<SB>2</SB>O, CaO, Fe<SB>2</SB>O<SB>3</SB>) is 5 or more and (h) bulk density is over 5.70 g/cm<SP>3</SP>. The bearing consists of the zirconia sinter excellent in the endurance. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing made of a zirconia-based sintered body having excellent durability.

[0002]

2. Description of the Related Art Ceramics have excellent wear resistance and corrosion resistance as compared with metals and are lightweight, so that they have been used in place of conventional metal bearing balls (rolling elements). ing. Bearings using these ceramic bearing balls have been used for hard disk drive in recent years because they enable stable rotation compared to metal in order to increase the recording density by increasing the rotation speed of the hard disk. Spindle motors have come to be used, and silicon nitride bearing balls have been used to improve the lubrication life under high speed and high temperature. However, in a spindle motor, a ball bearing is used with a preload in order to obtain high rotation accuracy, but a bearing ball made of silicon nitride has a linear expansion coefficient higher than that of a ball shaft steel used in a ball bearing. Since it is small, the preload changes greatly due to the temperature increase due to high speed rotation, and the rotation accuracy at high speed rotation cannot be obtained.
There was a problem that leads to the occurrence of read / write errors.

In JP-A-2000-74069, since the coefficient of linear expansion of zirconia is close to that of ball shaft steel, the use of zirconia bearing balls reduces fluctuations in preload due to temperature changes, and rotation accuracy at high speed rotation. It discloses that it can improve. However, the zirconia bearing balls disclosed in this publication merely specify the linear expansion coefficient, and do not specify the mechanical properties or the like of the sintered body to make it excellent as a bearing. I haven't. Further, it has been pointed out that the zirconia-based sintered body is deteriorated as described later, and there is a problem that it cannot be stably used as a bearing in various environments.

The zirconia-based sintered body has excellent mechanical properties, but in a specific temperature range of 200 to 300 ° C., it transforms from tetragonal zirconia to monoclinic zirconia, which causes thermal deterioration leading to strength reduction. Caused by,
Although a lot of prevention methods are described in Japanese Patent No. 21184, etc., it is a practical range as a bearing.
It has been clarified that mechanical properties such as strength and abrasion resistance are deteriorated and minute dimensional fluctuations occur when used for a long time in a high humidity atmosphere at a high temperature of about 150 ° C to 150 ° C. However, it has been found that this problem cannot be solved by a method of preventing thermal deterioration at 200 to 300 ° C. The durability such as wear resistance under load at a relatively low temperature of about 20 ° C. is improved as the crystal structure is made finer, but the resistance to corrosive components such as water is decreased. Therefore, at high temperatures of about 60 to 150 ° C, mechanical properties such as wear resistance deteriorate under load in a high-humidity atmosphere. Therefore, bearings that rotate at high speed under load and increase in temperature As a result, I could not use it because I was fully satisfied.

In Japanese Patent Laid-Open No. 2000-302548, in order to obtain a sintered body having excellent thermal stability, the crystal grain size is limited to a certain range, and a third layer composed of Al ₂ O ₃ , SiO ₂ and TiO ₂ is used. A method of adding specific amounts of components has been proposed. However, even if the third component composed of Al ₂ O ₃ , SiO ₂ , and TiO ₂ is added, the glass phase is formed due to impurities such as alkali metal and alkaline earth metal oxides, which may lead to a decrease in durability. Has properties, Al ₂ O ₃ , SiO ₂ , Ti
Sufficient improvement cannot be obtained only by adding the third component of O ₂ . The protection method described in the above publication can prevent thermal deterioration when exposed to hot water or high-humidity atmosphere near 200 ° C., but within a practical range of temperatures of 60 ° C. to 150 ° C. In particular, it has not been possible to completely prevent the deterioration of durability when a load is applied. In addition, at a temperature of about 60 ° C. to 150 ° C., grain boundaries become brittle when subjected to a load for a long time even in an environment in which no moisture or water vapor is present, and as a result, sudden wear occurs due to crystal grain shedding. I also have problems. From such a fact, at a high temperature of about 60 ° C to 150 ° C, and
A bearing material that has excellent thermal stability, corrosion resistance, mechanical properties and durability for a long period of time in a high humidity atmosphere, and at the same time has excellent wear resistance whether or not in a high humidity atmosphere. Was desired.

[0006]

The object of the present invention is 60
It has excellent thermal stability and corrosion resistance at high temperatures of about ℃ to 150 ℃ and even in high humidity atmosphere, is stable for a long time, has excellent mechanical properties, especially wear resistance, and has high durability. It is to provide a zirconia bearing having excellent wear resistance as a bearing regardless of the presence or absence of a humidity atmosphere.

[0007]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors in view of the present situation as described above, the result is 60 ° C to 1 ° C.
It has been found that the deterioration of mechanical properties as a bearing ball and a bearing at a high temperature of about 50 ° C. and in a high humidity atmosphere is different from that due to thermal stability at 200 to 300 ° C. That is, 200
It is said that the thermal deterioration at ˜300 ° C. is caused by the transformation of metastable tetragonal zirconia into stable monoclinic zirconia, and increasing the amount of stabilizer such as Y ₂ O ₃ and CeO _2. It is known that the thermal deterioration is suppressed by this. On the other hand, at a high temperature of about 60 ° C. to 150 ° C. and a decrease in strength and mechanical properties when exposed to a high-humidity atmosphere, the amorphous phase and glass that are unevenly unevenly distributed at the grain boundaries or the grain interfaces. It is presumed that this is caused by the stress corrosion of the phases, Y ₂ O _3, etc. by water.

SiO_TwoIs ZrO_TwoSegregation near grain boundaries
And has the effect of suppressing thermal deterioration, but at the
When impurities such as genus and alkaline earth metal oxides coexist
ZrO _TwoResists stress corrosion by forming a glass phase at grain boundaries
Resistance and the grain boundary strength
It became clear that it had a point. From this, S
iO_TwoNot only the amount of addition of SiO_TwoArca to quantity
Controlling the amount of impurities such as remetal and alkaline earth metal oxides
I found it important to do. In addition, ZrO
_TwoSiO in grain boundaries_TwoSegregation of Homogeneous and appropriate amount
It is important that the grain boundary surface area varies depending on the crystal grain size.
Therefore, to have excellent durability, it depends on the crystal grain size.
SiO_TwoWe also found that controlling the amount added is important
It was

The present inventors have found that the zirconia-based sintered body
Y_TwoO_Three/ ZrO_TwoMolar ratio, Al _TwoO_ThreeAnd Si
O_TwoContent of third component, crystal grain size, bulk density, and S
iO_TwoRelationship between amount and average crystal grain size, SiO_TwoAmount and Na
_TwoO, K_TwoO, CaO, Fe_TwoO_ThreeAlkali metal,
It has a special relationship with the amount of impurities such as alkaline earth metal oxides.
By controlling the temperature within a fixed range, about 60 ℃ ~ 150 ℃
Suppresses intergranular corrosion in high humidity atmosphere at high temperature
Control, improving the grain boundary strength, and high humidity atmosphere
Excellent wear resistance as a bearing regardless of the presence or absence of
It was found that they have durability, leading to the completion of the present invention.
It was At the same time, it is exposed to high temperatures and corrosive components such as water.
And a member for a crusher that agitates crushing and dispersing media at high speed
Zirconia sintered body with excellent wear characteristics
It has excellent durability such as wear resistance as a bearing.
It was also found that the present invention was completed.

That is, the first aspect of the present invention is (a) mainly positive
Y consisting of tetragonal crystals_TwoO_ThreeSystem zirconia sintered body, (b)
Y_TwoO_Three/ ZrO_TwoMolar ratio is 1.5 / 98.5-4 / 9
In the range of 6 and (c) SiO_Two0.05 to 2.5 times
Content%, (d) Al_TwoO _Three0.05 to 3.0 weight
%, And (e) the average crystal grain size is 0.7 μm or less.
(F) SiO_Two(Wt%) x average crystal grain size (μm)
Is in the range of 0.03 to 0.5, and (g) SiO_Two/
(Na_TwoO, K_TwoO, CaO, Fe_TwoO_ThreeTotal) weight
The ratio is 5 or more, and (h) the bulk density is 5.70 g / cm.
^ThreeZirco with excellent durability characterized by the above
The present invention relates to a bearing made of a near sintered material. The present invention
2 is TiO_TwoContent of 0.3% by weight or less
Zir having excellent durability according to claim 1, characterized in that
The present invention relates to a bearing made of a konia sintered body.

The requirements to be satisfied by the bearing of the present invention, which is made of a zirconia-based sintered body having excellent durability, will be described in detail below. (A) Y in which the crystal phase of ZrO ₂ is mainly tetragonal
Regarding the fact that it is a ₂ O ₃ -based zirconia-based sintered body. When monoclinic zirconia is contained in the zirconia-based sintered body,
When a minute crack is generated around the crystal and a stress is applied, a minute fracture occurs from this minute crack as a starting point, the resistance to friction, impact, crushing, etc. decreases, leading to a reduction in the life of the rolling bearing. Not preferable.
On the other hand, when cubic zirconia is contained, not only the crystal grain size becomes large and the mechanical properties are deteriorated, but also Y ₂ O ₃ tends to be unevenly distributed in the vicinity of the crystal grain boundary, which lowers the durability. It is not preferable because it causes damage.

In the present invention, the presence or absence and the content of monoclinic zirconia (M), which is the crystal phase of zirconia, and the amounts of tetragonal zirconia (T) and cubic zirconia (C) are determined. It is determined by X-ray diffraction by the following method. That is, the surface of the sintered body and the processed sintered body product has been transformed from tetragonal zirconia to monoclinic zirconia by stress-induced phase transformation, and the true crystal phase cannot be identified. The body surface is polished to a mirror surface and measured by X-ray diffraction at a diffraction angle of 27 to 34 degrees, and the presence or absence of monoclinic zirconia and the content thereof are determined from the formulas shown below.

[Equation 1]

Further, tetragonal zirconia and cubic zirconia were measured by X-ray diffraction in a diffraction angle range of 70 to 77 degrees in the same manner as the method for confirming the presence or absence of monoclinic zirconia. Calculate by formula.

[Equation 2] In the present invention, mainly tetragonal zirconia means cubic zirconia obtained from the above X-ray diffraction.
By volume, it means that monoclinic zirconia can be allowed up to 5% by volume.

(B) The Y ₂ O ₃ / ZrO ₂ molar ratio in the zirconia-based sintered body of the present invention is 1.5 / 98.5-4 /.
Regarding the range of 96. The Y ₂ O ₃ / ZrO ₂ molar ratio in the zirconia-based sintered body of the present invention is 1.5 / 9.
8.5-4 / 96, more preferably 2.0 / 98.0
It should be within the range of 3.5 / 96.5. Usually, HfO ₂ which may be contained in a small amount in the ZrO ₂ raw material may be mixed, and ZrO ₂ including this HfO ₂ amount may be included.
The total amount of HfO ₂ and HfO ₂ is the ZrO ₂ amount. Y ₂ O ₃ / Zr
When the O ₂ molar ratio is less than 1.5 / 98.5, the amount of monoclinic ZrO ₂ in the sintered body increases and cracks occur inside the sintered body, which is a condition for using the bearing. It is not preferable because a crack develops in a state where a load is applied for a long period of time, and cracks or chips are generated, resulting in deterioration of durability.
On the other hand, if the Y ₂ O ₃ / ZrO ₂ molar ratio exceeds 4/96, the amount of tetragonal ZrO ₂ decreases, the amount of cubic ZrO ₂ increases, and mechanical properties deteriorate, which is not preferable. In addition,
Up to 30 mol% of the amount of Y ₂ O ₃ added, 1 of other rare earth oxides
It is also possible to use ones or those substituted with two or more kinds. Examples of such rare earth oxides include CeO ₂ and Nd.
₂ O ₃ , Yb ₂ O ₃ , Dy ₂ O _{3 and the} like are preferable because they are inexpensive.

(C) Regarding the content of SiO ₂ in the zirconia-based sintered body of the present invention of 0.05 to 2.5% by weight. SiO in the zirconia-based sintered body of the present invention
₂ is 0.05 to 2.5% by weight, preferably 0.05 to
It is necessary to contain 2.0% by weight. SiO ₂
Is segregated near the ZrO ₂ grain boundary, and SiO ₂ is Z
The presence in the rO ₂ crystal grain boundary suppresses stress corrosion, and further has the effect of strengthening the ZrO ₂ crystal grain boundary bond, which is effective in improving durability. If the SiO ₂ exceeds 2.5 wt%, amorphous phase and a glass phase much be formed on ZrO ₂ grain boundaries reduces the ZrO ₂ grain coupling, the stress corrosion proceeds readily at the same time, The effect of the stress-induced phase transformation from tetragonal to monoclinic is reduced, resulting in deterioration of mechanical properties and durability, which is not preferable. When the amount of SiO ₂ is less than 0.05% by weight, Zr
Since there is a portion where SiO ₂ does not exist in the O ₂ crystal grain boundary, stress corrosion cannot be suppressed and there is no effect on durability, which is not preferable.

(D) In the zirconia-based sintered body of the present invention
Al_TwoO_ThreeContent of 0.05 to 3.0% by weight
About the point. Al in the zirconia-based sintered body of the present invention
_TwoO_ThreeIs 0.05 to 3.0% by weight, preferably 0.05
.About.2.0% by weight is required. Al_Two
O_ThreeIs ZrO_TwoAl at grain boundaries_TwoO_ThreeExists as crystal particles
Not only exist, but also ZrO_TwoNear the grain boundaries and near the grain boundaries
It is segregated. Al_TwoO_ThreeThe addition of
Not only has an effect on the homogenization of the structure, but also 60 ℃ to 150 ℃
Deterioration of characteristics in high humidity atmosphere at high temperature
It has a suppressing effect. Furthermore, ZrO_TwoStrengthening of grain boundaries
Since it is effective, mechanical properties such as impact resistance and wear resistance are
It will be excellent. Al_TwoO_ThreeContent is 0.05 weight
If less than%, Al_TwoO _Three3.0 with no effect of addition
ZrO when the content exceeds_TwoAl at grain boundaries_TwoO_Three
Since there are many crystal particles, the durability is reduced.
It is not preferable because

(E) Regarding the point that the average crystal grain size in the zirconia-based sintered body of the present invention is 0.7 μm or less. The average crystal grain size in the zirconia-based sintered body of the present invention is 0.
It should be 7 μm or less, and more preferably 0.5 μm or less. If the average crystal grain size exceeds 0.7 μm, not only wear resistance and durability are deteriorated, but also mechanical properties such as wear resistance are deteriorated, which is not preferable. The average crystal grain size is the average value obtained by polishing the surface of the sintered body to a mirror surface and then performing thermal etching or chemical etching, observing with a scanning electron microscope and measuring 10 points by the intercept method. The calculation formula is as follows.

(3) D = 1.5 × L / n [Wherein D: average crystal grain size (μm), n: number of crystal particles per length L, L: measurement length (μm) Indicates. ]

(F) The zirconia-based sintered body of the present invention is S
iO ₂ (% by weight) × average crystal grain size (μm) is 0.03 to
Regarding the point that it is in the range of 0.5. The zirconia-based sintered body of the present invention has a SiO ₂ (wt%) × average crystal grain size (μm) of 0.03 to 0.5, preferably 0.03 to.
It should be in the range of 0.3. SiO ₂ is Zr
O ₂ segregates near the crystal grain boundaries to suppress stress corrosion and improves durability, but since the grain boundary surface area varies depending on the crystal grain size, in order to allow SiO ₂ to exist uniformly in the crystal grain boundaries, the crystal grain It is necessary to adjust the amount of SiO ₂ with respect to the diameter within a certain range. SiO ₂ (wt%) x average crystal grain size (μ
When m) exceeds 0.5, SiO ₂ existing in the vicinity of ZrO ₂ crystal grain boundaries becomes excessive, and many amorphous phases and glass phases are formed at the grain boundaries, or ZrO ₂ crystal grain boundary bonds are reduced. However, the stress corrosion is likely to proceed, and at the same time, the effect of the stress-induced phase transformation from tetragonal to monoclinic is reduced, and as a result, mechanical properties, wear resistance, and durability are reduced, which is not preferable. When SiO ₂ (wt%) × average crystal grain size (μm) is less than 0.03, there is a portion where SiO ₂ does not exist in the ZrO ₂ crystal grain boundary, stress corrosion cannot be suppressed, and there is no effect on durability. Not preferable.

(G) In the zirconia-based sintered body of the present invention, SiO ₂ / (Na ₂ O, K ₂ O, CaO, Fe ₂ O)
₃ total) Regarding the weight ratio of 5 or more. In the zirconia-based sintered body of the present invention, SiO ₂ / (Na ₂ O,
It is necessary that the total weight ratio of K ₂ O, CaO, and Fe ₂ O ₃ is 5 or more, preferably 10 or more. SiO ₂ /
(Na ₂ O, K ₂ O, CaO, Fe ₂ O ₃ total) weight ratio of less than 5, SiO ₂ and Na ₂ O, K ₂ O, Ca
O and Fe ₂ O ₃ form a large amount of glass phase at the grain boundaries, so that corrosion occurs, and as a result, the ZrO ₂ grain boundary bond is reduced, and the effect of the stress-induced phase transformation from tetragonal to monoclinic. Is deteriorated, resulting in deterioration of mechanical properties and durability, which is not preferable.

(H) Regarding the point that the zirconia-based sintered body of the present invention has a bulk density of 5.70 g / cm ³ or more. The bulk density of the zirconia-based sintered body of the present invention is 5.70 g / cm ³ or more, preferably 5.80 g / cm ^3.
It must be at least cm ³ . Bulk density is 5.7
When it is less than 0 g / cm ^{3, the} resistance to external stress such as friction and impact is poor, and at the same time, the resistance to corrosion in a high humidity atmosphere at a high temperature of about 60 ° C. to 150 ° C. is unfavorable.

(I) Regarding the point where TiO ₂ in the zirconia-based sintered body of the present invention is 0.3% by weight or less. TiO ₂ in the zirconia-based sintered body of the present invention is 0.3% by weight or less, preferably 0.2% by weight or less, more preferably 0.1% by weight or less. When the amount of TiO ₂ exceeds 0.3% by weight, TiO ₂ forms a solid solution with ZrO ₂ and promotes the growth of the crystal grain size, and the crystal grain size becomes large, resulting in deterioration of wear resistance and durability. It is not preferable because it causes. TiO ₂
Is an impurity, and the smaller the amount is, the better, but in the present technology, the minimum value of the TiO ₂ impurity is about 0.004% by weight.

The bearing made of a zirconia-based sintered body having excellent durability of the present invention can be manufactured by various methods. An example thereof is shown below, but the method is not limited to this. In the present invention, it is necessary to use zirconia powder purified by the liquid phase method. That is, ZrO ₂ and Y ₂ O
An aqueous solution of a zirconium compound (eg, zirconium oxychloride) and an yttrium compound (eg, yttrium chloride) are uniformly mixed and hydrolyzed to obtain a hydrate and dehydrated so that the content of ₃ becomes a predetermined molar ratio. And dried, and then calcined at 400 to 1250 ° C., Y ₂ O ₃ and Al ₂ O
₃ , a method of obtaining a zirconia powder containing few impurities other than SiO ₂ is adopted. The components other than Y ₂ O ₃ may be added in a predetermined amount as an aqueous solution of a salt to a mixture of an aqueous solution of a zirconium compound and an yttrium compound, or a hydroxide or a carbonate at the time of pulverizing and dispersing a calcined powder described later. , Oxide, etc. may be added.

The obtained calcined powder is pulverized and dispersed by a wet method, a known molding aid (wax emulsion, PVA, acrylic resin, etc.) is added if necessary, and dried by a known method such as a spray dryer. Obtain a molding powder. The average particle size of the obtained molded powder particles is preferably 0.5 μm or less. The obtained molded powder can sufficiently obtain the sintered body of the present invention by a known molding method, for example, a molding method such as press molding or rubber press molding, and further, an organic solvent containing water. Alternatively, a method in which a soluble polymer, water, or the like is used as a molding aid in a wet process or in a liquid is also possible. Then, the obtained molded body is 1150 to 1550 ° C.,
Preferably, a sintered body is obtained by firing at 1150 to 1400 ° C., and processed into a desired shape to obtain a bearing. Further, if necessary, HIP treatment can be performed to increase resistance to friction, impact, crushing, etc., and thus mechanical properties and durability can be improved. The HIP treatment is 1100 to 14 in an inert atmosphere such as Ar or in an N ₂ or O ₂ atmosphere after pressureless sintering.
It is preferably carried out at 00 ° C.

[0024]

The present invention will be described below with reference to examples.
The present invention is not limited thereby.

Examples 1 to 17, Comparative Examples 1 to 20 Zirconium oxychloride having a purity of 99.6% and a purity of 99.
9% yttrium nitrate was made into an aqueous solution and mixed so as to have the compositions shown in Tables 1 and 2. Next, this aqueous solution is hydrolyzed under heating reflux to generate a precipitate of hydrated zirconium in which Y ₂ O ₃ is solid-solved, dehydrated and dried, and 400 to 1000 ° C.
After calcination for 1 hour, the obtained zirconia powder was wet pulverized. With respect to the components other than Y ₂ O ₃ , a predetermined amount was added and mixed at the time of pulverization in the form of oxide or salt. Next, the obtained slurry was dried and sized to obtain a molding powder. This molding powder was molded into a spherical shape by the rolling granulation molding method. The obtained molded body was fired at 1000 to 1600 ° C. to obtain a spherical sintered body having a diameter of 1 mm. A spherical sintered body having a diameter of 1 mm was finished by barrel polishing to prepare a sample. The characteristics of these samples are shown in Tables 1-2. Example 1
Reference numeral 17 is a zirconia-based sintered body of the present invention, and Comparative Examples 1 to 1
20 is a comparative product which does not meet at least one of the requirements of the present invention.

Next, a test was conducted on the durability under a load at 60 ° C. for a long time. The spherical sample 1200 cc with a diameter of 1 mm obtained above was used for the internal capacity 1400 c.
c DYNO MILL (manufactured by Shinmaru Enterprises:
Type KDL-PILOT), BaT manufactured by Kyoritsu Kiln
iO ₃ powder (average particle size 1.5 μm, specific surface area 1.2 m
² / g) of 600 g and 2400 cc of water were mixed to maintain a 20 wt% concentration of BaTiO ₃ slurry at 60 ° C.
The wear rate per unit time for each cycle was tested by circulating the disk at a rate of 00 cc / min in the range of 60 to 65 ° C while adjusting the temperature, and at a disk peripheral speed of 8 m / sec for 24 hours as one cycle. Was measured. The wear rate was calculated as the rate of change in weight before and after the test. The maximum wear rate of each sample for each cycle is shown in the table. In Comparative Examples 15 and 19, since the bulk density of the sintered body was not sufficient, the wear rate was not measured. Furthermore, the durability under load in a high humidity atmosphere at a high temperature of 60 to 150 ° C and 200 to 300 ° C.
In order to clarify the difference with heat deterioration at
The spherical sample was put in an autoclave having an internal volume of 50 cc, 20 cc of pure water was added, and the sample was kept at 200 ° C. for 50 hours and then cooled, and the sample taken out was checked for cracks. For those in which cracks could not be confirmed, the cross section of the sample was observed under a microscope to measure the depth of the deteriorated layer.

Durability in the absence of water or water vapor using the samples prepared in Examples 18 to 20 and Comparative Examples 21 to 23 and Examples 3, 6, 13 and Comparative Examples 8, 14 and 16. As a test, use isoparaffin 60 to 6
Circulation was performed while adjusting the temperature in the range of 5 ° C., and a test was performed in which the disk peripheral speed was 8 m / sec, one cycle was 24 hours, and 10 cycles were performed, and the wear rate per unit time in each cycle was measured. A running test was performed, and the wear rate was calculated as the rate of change in weight before and after the test. Table 3 shows the maximum wear rate for each sample for each cycle.
Shown in. In Table 3, Example 18 is a test result of the sample manufactured in Example 3, Example 19 is a test result of the sample manufactured in Example 6, and Example 20 is an example. It is a test result about the sample manufactured in No. 13. Further, Comparative Example 21 is a test result for the sample manufactured in Comparative Example 8, and Comparative Example 22 is a test result for the sample manufactured in Comparative Example 14.
Comparative example 23 is a test result of the sample manufactured in comparative example 16. From the results shown in the table, 60 ℃ ~ 150 ℃
In a high humidity atmosphere at a high temperature of about 200 ° C to 30 ° C
Unlike the thermal deterioration at 0 ° C., the zirconia-based sintered body of the present invention having excellent durability exhibits excellent durability regardless of whether it is in a high humidity atmosphere at a high temperature of about 60 ° C. to 150 ° C. It is clear that the bearing has excellent characteristics as a bearing, and if even one of the requirements of the present invention is not satisfied, the bearing lacks durability.

[0028]

[Table 1]

[Table 2]

[Table 3]

[0029]

According to the present invention, it is possible to provide a bearing made of a zirconia-based sintered body having excellent thermal stability, corrosion resistance, and wear resistance.

Continued front page    (72) Inventor Toshio Kawanami             Osaka Prefecture Sakai City Tozato Onocho 3-22-24 Stock             Company Nikkato F term (reference) 3J101 AA02 BA10 EA75 EA80 FA06                       FA34 GA53                 4G031 AA01 AA04 AA08 AA11 AA12                       AA21 AA29 AA30 BA19 BA20                       CA01 CA04 CA07 GA01 GA06                       GA11 GA19

Claims (2)

[Claims] 1. (a) Y mainly composed of tetragonal crystals_TwoO_Three
System zirconia sintered body, (b) Y_TwoO_Three/ Zr
O_TwoThe molar ratio is in the range of 1.5 / 98.5 to 4/96.
(C) SiO_Two0.05 to 2.5% by weight,
(D) Al_TwoO _Three0.05 to 3.0% by weight,
(E) The average crystal grain size is 0.7 μm or less, and (f) S
iO_Two(Wt%) × average crystal grain size (μm) is 0.03 to
In the range of 0.5, (g) SiO_Two/ (Na_TwoO, K
_TwoO, CaO, Fe_TwoO_ThreeThe total weight ratio is 5 or more
(H) Bulk density is 5.70 g / cm^ThreeThat's all
Zirconia sintered body with excellent durability characterized by
Bearings. _2. A bearing made of a zirconia-based sintered body having excellent durability according to claim 1, wherein the content of TiO ₂ is 0.3% by weight or less.