JPH06102574B2 - High toughness ceramic sintered body excellent in heat resistance stability and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high toughness ceramic sintered body, and more specifically, zirconia containing Y ₂ O ₃ and CeO ₂ or CeO ₂ as a stabilizer, and Al and Si. , B and borides, carbides, nitrides and Cr ₂ O ₃ (above the second component) of elements of groups 4a, 5a and 6a of the periodic table, or Al ₂ O ₃ and MgO · Al ₂ O as the third component.
₃ (spinel), composed of a 3Al ₂ O ₃ · 2SiO selected from ₂ (mullite) (predominantly) variance components, excellent in wear resistance and thermal stability at high strength, very little of the strength and toughness of the time degradation The present invention relates to a high toughness ceramic sintered body and a method for manufacturing the same.

[Prior Art and Problems] A zirconia sintered body undergoes a phase transition from a cubic crystal to a tetragonal crystal in a high temperature region to a monoclinic crystal. At that time, a volume change occurs, and a tetragonal crystal to a monoclinic crystal phase is particularly generated. There is a drawback that the volume change of the transition is large, and therefore the sintered body is destroyed by this volume change. In order to eliminate this drawback, ZrO ₂ was added to CaO, M
A large number of stabilized zirconia consisting of cubic crystals or partially stabilized zirconia consisting of cubic crystals and monoclinic crystals are disclosed at room temperature, in which gO, Y ₂ O _{3 and the} like are dissolved to prevent the transition. In addition, it has been announced that partially stabilized zirconia obtained by allowing a tetragonal crystal, which is a metastable phase, to exist in a sintered body at room temperature exhibits high strength. This is partly because, when a mechanical external stress is applied, a phase transition from a metastable tetragonal crystal to a monoclinic crystal that is a room temperature stable phase is induced and the stress is absorbed.

Y ₂ O ₃ has been mainly used as a stabilizer for obtaining a sintered body composed of a tetragonal crystal that is mainly metastable at room temperature, and has exhibited particularly high toughness and high strength.
However, since the partially stabilized zirconia mainly composed of tetragonal crystals is a metastable phase generated as a result of bringing a high temperature phase to a low temperature region, its structure and properties change with time, particularly, 200 ° C to 400 ° C. The heating at a relatively low temperature causes a phase transition to a monoclinic crystal, and the deterioration of strength with time is extremely large. Further, this strength deterioration is remarkably promoted in the presence of water or the like, and such deterioration of characteristics over time poses a problem. Hereinafter, withstanding such deterioration over time under heating at a relatively low temperature is referred to as “heat resistance stability”.

For high toughness ceramics that utilize the tetragonal → monoclinic phase transformation of zirconia, a different method is to incorporate microcracks in the alumina matrix and sinter the stress generated when a load is applied. A method for producing a ceramic molded body having high fracture toughness which is absorbed by microcracks existing in the body is disclosed. (JP-A-52
-86413) Also, unlike the incorporation of microcracks, zirconium oxide (zirconia) containing no stabilizer is incorporated up to 50% by volume in a sintered body mainly composed of a dense non-metal cemented carbide,
A sintered compact having improved strength is disclosed. (JP Sho
54-61215) However, since the zirconia contained in these two examples does not contain a stabilizer at all, it is remarkably improved in terms of toughness and bending strength, but is not very thermally effective. It is stable.

On the other hand, alumina, mullite, spinel, Si ₃ N ₄ ,
5-50% by volume of monoclinic or tetragonal zirconia containing no stabilizer as a ceramic embedding material in a ceramic matrix such as yttria partially stabilized zirconia
2 mol% Y ₂ O ₃ as a molding containing or embedding material
A ceramic sintered compact containing mainly tetragonal zirconia stabilized at 5 to 30% by volume is disclosed (Japanese Patent Laid-Open No. 59-64567). However, the former does not contain a stabilizer in zirconia and the latter partially stabilizes zirconia with yttria. Therefore, it is thermally unstable and easily deteriorates with time.

In addition, as a high toughness ceramic sintered body, Y ₂ O ₃ , MgO, CaO
Zirconia containing 0.5 to 60% by weight of Al ₂ O ₃ as a stabilizer (JP-A-58-32066) and Y ₂ O ₃ , MgO,
There is disclosed a sintered body containing Al ₂ O ₃ or various boride, carbide, nitride and Al ₂ O ₃ in zirconia containing CaO as a stabilizer (Japanese Patent Laid-Open No. 58-120571).

However, among these disclosed zirconia sintered bodies, Mg
The ones that use O and CaO as stabilizers have lower mechanical strength than those that use Y ₂ O ₃ as a stabilizer, and also have a theoretical stabilization, that is, tetragonal crystal to single crystal, by holding for a long time near 1000 ° C. Since it is transformed into orthorhombic crystals, resulting in a decrease in mechanical strength, its use as a structural material is limited. Furthermore, the high toughness zirconia sintered body stabilized by Y ₂ O ₃ easily undergoes a phase transition at a low temperature of 200 ° C to 400 ° C as described above, and transitions from the surface of the sintered body toward the inside with time. And the deterioration of strength and toughness is remarkable, and the mechanism of toughness does not work, and there is a serious defect that microcracks are generated and eventually destroyed due to volume expansion accompanying the phase transition. However, it is poor in reliability as a structural material.

Also disclosed is a method for producing high-strength zirconia ceramics having higher bending strength by adding alumina to ZrO ₂ having Y ₂ O ₃ as a stabilizer and performing HIP treatment (JP-A-60- 86073).

In the publication, although the strength of zirconia ceramics is improved, since zirconia containing Y ₂ O ₃ as a stabilizer is the main component, there is still a problem that deterioration with time occurs at 200 ° C to 400 ° C.

On the other hand, zirconia porcelain with Y ₂ O ₃ and CeO ₂ as stabilizers and its manufacturing method (JP-A-60-141673), zirconia with CeO ₂ as stabilizer and zirconia-based calcination containing alumina Associations are also disclosed. (JP-A-60-108367).
The zirconia ceramics containing CeO ₂ shown in these publications have a slightly improved thermal stability as compared with zirconia having Y ₂ O ₃ as a stabilizer, but have the problem of insufficient strength. However, its use as a structural material is limited.

[Problems to be Solved by the Invention] Y ₂ O ₃ containing Y ₂ O ₃ -ZrO ₂ zirconia ceramics and this alumina comprises thus the Y ₂ O ₃ as a stabilizer
-ZrO ₂ -Al ₂ O ₃ zirconia ceramics, 200-400
℃ has the disadvantage of deterioration with time in the low temperature, also Y ₂
O ₃ and CeO ₂ and a stabilizer Y ₂ O ₃ -CeO ₂ -ZrO ₂ zirconia ceramics or, CeO ₂ for the CeO ₂ and stabilizer -
ZrO ₂ -based and CeO ₂ —ZrO ₂ —Al ₂ O ₃ -based zirconia ceramics have a drawback that they have a low strength although their deterioration over time is slightly improved.

Further, as a problem common to these zirconia ceramics, there is a problem that the wear resistance is poor due to the low hardness, and the application is limited.

The present invention has been made to solve such a problem of high toughness zirconia, and has a dramatic increase in the thermal stability of zirconia and excellent durability (that is, heat stability) without deterioration with heat. Moreover, it is intended to provide a sintered body having high strength, high toughness, and excellent wear resistance, improving the performance of the high toughness zirconia sintered body as a structural material, and expanding its application. .

[Means for Solving Problems] The high toughness ceramic sintered body excellent in heat resistance stability of the first invention of the present invention is mainly a tetragonal crystal containing Y ₂ O ₃ —CeO ₂ or CeO ₂ as a stabilizer. For partially stabilized zirconia consisting of Al, Si, B as a second component, and one or more selected from boride, carbide and nitride of Group 4a, 5a and 6a elements of the Periodic Table, and Cr ₂ O _3. It is a sintered body containing 1 to 70% by weight of two or more kinds, and the average particle diameter of the tetragonal zirconia crystal particles contained in the sintered body is 2 μm or less, and the heat resistance is excellent. It is a summary.

The high toughness ceramic sintered body excellent in heat resistance stability of the second invention of the present invention is the above-mentioned with respect to partially stabilized zirconia mainly composed of tetragonal crystal containing Y ₂ O ₃ and CeO ₂ or CeO ₂ as a stabilizer. The second component, and as the third component, Al ₂ O ₃ , MgO.
Al ₂ O ₃ (spinel), there at 2Al ₂ O ₃ · 2SiO ₂ (mullite) from selected one or two or more second, sintered body containing 1 to 70 internal wt% in total of the third component And the average particle size of the tetragonal zirconia crystal particles contained in the sintered body is 2 μm.
The main points are as follows.

Here, "excellent heat resistance stability" means 300
The primary condition is to have a bending strength of 100 kg / mm ² or more after a heat deterioration test at 300 ° C for 300 hours. Deterioration in heat stability is also confirmed by an increase in monoclinic crystals after the heat deterioration test.

Further, the high toughness ceramic sintered body having excellent heat resistance stability of the present invention can be dramatically increased in strength, toughness and heat stability by being subjected to hot pressing or hot isostatic pressing.

ZrO ₂ , YO _1.5 , CeO _{2 of} partially stable zirconia contained in the high toughness ceramic sintered body excellent in heat stability of the present invention,
As shown in the attached drawing, the composition range of point A (ZrO ₂ 87.5 mol%, YO _1.5 12 mol% is shown on the trigonometric coordinates in which ZrO ₂ , YO _1.5 , and CeO ₂ mol% are displayed on the three axes intersecting the equilateral triangle. , CeO ₂ 0.5mol%) Point B (ZrO ₂ 95.5mol%, YO _1.5 4mol%, CeO ₂ 0.5mol%) Point C (ZrO ₂ 95.5mol%, YO _1.5 2mol%, CeO ₂ 2.5mol%) Point D ( _{ZrO 2 92.0mol%, YO 1.5 0mol} %, CeO 2 8.0mol%) point _{E (ZrO 2 84.5mol%, YO} 1.5 0mol%, surrounded by a point connecting the specific 5 composition point indicated by CeO ₂ 15.5 mol%) The characteristics can be further improved by setting the composition within the range.

Further, among the second components contained in the high toughness ceramic sintered body having excellent heat resistance stability of the present invention, Al, Si, B and the periodic table.
Borides, carbides, and nitrides of 4a, 5a, and 6a elements are AlN, T
iC, TiN, TiCN, TiB ₂ , Si ₃ N ₄ , SiC, B ₄ C, WC, Ta
C, NbC, Cr ₃ C ₂ , Cr ₂ B, ZrN, ZrB ₂ , ZrC, HfN, HfB ₂ , Hf
Can be C, BN.

The method for producing a high toughness ceramic sintered body excellent in heat stability according to the present invention (third invention) is a ZrO ₂ powder containing Y ₂ O ₃ and CeO ₂ or CeO ₂ as a stabilizer, or Y ₂ O ₃ Powder, CeO ₂ powder and ZrO ₂ powder or the total amount of CeO ₂ powder and ZrO ₂ powder as the second component, Al, Si, B and Periodic Table 4a, 5
Borides, carbides and nitrides of a and 6a group elements, and Cr ₂ O ₃
A mixture of 1 or 2 or more powders selected from ZrO ₂ powder or a mixed powder obtained by blending the powder in the range of 1 to 70% by weight based on the total amount under the specified conditions. It is what is sintered. That is, the tetragonal zirconia crystal particles contained have an average crystal particle diameter of 2 μm or less and are sintered under the condition that a sintered body having excellent heat resistance stability is obtained.

The manufacturing method according to the fourth aspect of the present invention is the method of adding Al ₂ O ₃ , MgO as a third component in addition to the second component in the _{third aspect} .
· Al ₂ O ₃ (spinel), 3Al ₂ O ₃ · 2SiO ₂ second one or more powders selected from (mullite) with respect to the total amount of ZrO ₂ powder or the, the third component A mixture powder obtained by blending in a total amount of 1 to 70% by weight is fired, and the tetragonal zirconia crystal particles contained have an average particle diameter of 2 μm or less and are excellent in heat resistance stability. The main point is to sinter so as to obtain a sintered body.

This Y ₂ O ₃ , CeO ₂ , ZrO ₂ used in the production method of the present invention
As shown in the attached drawing, the composition ratio of the powder is as follows: Point A (ZrO ₂ 87.5 mol%, YO _1.5 12 mol) in the triangular coordinate system in which the three axes intersecting the equilateral triangle represent the mol% of ZrO ₂ , YO _1.5 , and CeO ₂ , respectively. %, CeO ₂ 0.5 mol%) Point B (ZrO ₂ 95.5 mol%, YO _1.5 4 mol%, CeO ₂ 0.5 mol%) Point C (ZrO ₂ 95.5 mol%, YO _1.5 2 mol%, CeO ₂ 2.5 mol%) Point D _{(ZrO 2 92.0mol%, YO 1.5} 0mol%, CeO 2 8.0mol%) point _{E (ZrO 2 84.5mol%, YO} 1.5 0mol%, CeO 2 15.5mol%) bounded by a line connecting a specific 5 composition point represented by The composition can be within the specified range.

Further, among the second components used in the production method of the present invention, A
i, Si, B, periodic table 4a, 5a, borides 6a group element, carbides, AlN nitride, TiC, TiN, TiCN, TiB 2, Si 3 N 4, Si
C, B ₄ C, WC, TaC, NbC, Cr ₃ C ₂ , Cr ₂ B, ZrN, ZrB ₂ , Zr
It can be C, HfN, HfB ₂ , HfC, BN.

Furthermore, the ZrO ₂ powder containing Y ₂ O ₃ and / or CeO ₂ as a stabilizer used in the production method of the present invention is a sol of ZrO ₂ and / or a water-soluble salt of Y ₂ O ₃ and CeO ₂ . The resulting ZrO ₂ powder can be obtained by uniformly mixing the resulting water-soluble salt in a solution state and then separating it in the form of a precipitate. In addition,
Through the first and second inventions, some or all of ZrO ₂
It can be replaced by HfO ₂ .

[Operation] The high toughness ceramic sintered body of the present invention will be described later due to the presence of tetragonal ZrO ₂ stabilized by a specific stabilizer and a predetermined highly elastic second component (or further third component). As is clear by referring to the strength, fracture toughness value, and thermal deterioration test result of the sintered body of the example, high strength and high toughness are developed, and in the temperature range where thermal instability is conventionally caused. It shows almost no change even after a long-term heat deterioration test, exhibits extremely high strength, and is extremely excellent in heat resistance stability.

This is because, firstly, the crystal structure of tetragonal zirconia stabilized by the addition of both CeO ₂ and Y ₂ O ₃ or CeO ₂ is better than that of tetragonal zirconia stabilized by conventional Y ₂ O ₃ alone. This is because it is closer to the cubic crystal structure that is a high temperature stable phase of. Secondly, the addition of a highly elastic second component, which is mainly a dispersive component, increases the tetragonal content, contributes to an increase in fracture energy due to an increase in elastic modulus, exhibits high strength and the presence of the second component. It is thought that it helps to strengthen the grain boundary part of ZrO ₂ , also enhances the stability of metastable tetragonal zirconia, and as a result of the synergistic effect of stability due to the presence of CeO ₂ component, the heat stability is significantly improved. . That is, the ZrO ₂ grain boundary has a fine structure in which a highly elastic substance exists around the grain, the ZrO ₂ particles are surrounded by the highly elastic substance in the surroundings, and the tetragonal → monoclinic phase transition accompanied by volume expansion (during thermal degradation) And the phase transition phenomenon that occurs in the stress concentration part at the time of fracture of the sintered body)
It is presumed that it contributes to the improvement of strength and thermal stability. Further, the presence of the second component improves the hardness, further improves the wear resistance of ZrO ₂ , and improves the mechanical properties such as hardness, strength and creep of the zirconia sintered body at high temperature.

Contained in the sintered body of the present _{invention, Y 2 O 3 -CeO 2 -ZrO} 2 system and tetragonal zirconia CeO ₂ -ZrO ₂ system does not exhibit the stable deterioration by thermal is metastable tetragonal Therefore, when stress is concentrated in the vicinity of the ZrO ₂ particles, it transforms into a monoclinic crystal, which is a stable phase at low temperature, and has the effect of relaxing the stress. Therefore, the high toughness ceramic sintered body of the present invention has a significantly high strength,
It shows high toughness.

In the present invention, the second component is Al, Si, B, and the periodic table 4a, 5
Borides, carbides, nitrides or Cr ₂ O _{3 of} group a and 6a
Since it contains one or more selected from
Compared with zirconia ceramics that do not contain these,
Especially excellent in hardness. In addition to the second component, further for Al ₂ O ₃ third component, MgO · Al ₂ O ₃ (spinel), 3Al ₂ O ₃ · 2
By coexisting one or more selected from SiO ₂ (mullite), the sintered body is increased, the density is improved, and the stability of the tetragonal zirconia crystal in the sintered body is excellent.
Further, the second component (or further third component) (hereinafter, also collectively referred to as “dispersion component”) is contained and subjected to hot pressing or hot isostatic pressing to obtain a sintered body. It becomes more dense and more remarkably (that is, about 1.5 times or more compared with the case of normal pressure sintering), the strength and hardness are improved. That is, the hot pressing process or the hot isostatic pressing process removes defects such as pores contained in the sintered body and further promotes densification. This densification, combined with the presence of highly elastic materials, makes it more difficult for the tetragonal to monoclinic phase transition (phase transition that occurs during thermal degradation, phase transition that occurs when the sintered body breaks) with volume expansion. Therefore, it is presumed that it contributes to the improvement of heat stability and strength. The heat resistance stability is supported by the results of the heat deterioration test, and is primarily confirmed by measuring the bending strength after the heat deterioration test (see Tables 1 to 3).

The present invention requires Y ₂ O ₃ and CeO ₂ or CeO ₂ as a stabilizer for zirconia. The compounding amounts of the three components of Y ₂ O ₃ , CeO ₂ and ZrO ₂ are as follows:
It is recommended to select within the range surrounded by the line connecting B, C, D and E. Within this range, the stability of the tetragonal crystal is high and the heat stability is excellent, but outside this range, the heat stability is significantly reduced and the mechanical properties are also poor. That is, if the content of YO _1.5 is larger than that of the point A (YO _1.5 12 mol%), the toughness is lowered, and if the content of YO _1.5 is smaller than that of the point B (YO _1.5 4 mol%), the heat stability is lost. Point C (YO _1.5 2mol
%, CeO ₂ 2.5 mol%), the heat stability becomes poor when YO _1.5 and CeO ₂ are less than the above. In addition, point D (CeO ₂ 8 mol
%) Is less than CeO ₂ , heat stability is poor, and point E (Ce
If CeO ₂ is more than O _{2 (} 15.5 mol%), sufficient mechanical strength cannot be obtained.

In order to make the present invention more effective, in the triangular coordinates as shown in the drawing, the blending amounts of the above three components are point A (ZrO ₂ 87.5 mol%, YO _1.5 12 mol%, CeO ₂ 0.5 mol%) point _{H (ZrO 2 94.5mol%, YO} 1.5 4mol%, CeO 2 1.5mol%) point _{G (ZrO 2 94.5mol%, YO} 1.5 2.5mol%, CeO 2 3mol%) point _{F (ZrO 2 81mol%, YO} 1.5 0mol %, CeO ₂ 9mol%) point _{E (ZrO 2 84.5mol%, YO} 1.5 0mol%, may be selected within the range surrounded by the solid line connecting the CeO ₂ 15.5mol%). In addition,
It is also possible to replace a part of Y ₂ O ₃ with a rare earth metal oxide such as Nd ₂ O ₃ , Yb ₂ O ₃ , La ₂ O ₃ and Er ₂ O ₃ .

In the present invention, it is necessary to contain the dispersion component in an amount of 1 to 70% by weight. The reason for limiting the addition amount of the dispersion component is 1 internal weight%
This is because if the content is 70% by weight or more, the content of tough ZrO ₂ is reduced.

In order to make the present invention more effective, it is advisable to select the addition amount of the dispersion component in the range of 5 to 50% by weight. If it exceeds this range, the dispersed component may become a continuous phase in the entire sintered body depending on the particle size of the dispersed component.

These dispersion components include Al ₂ O ₃ , MgO · Al ₂ O ₃ (spinel), 3Al ₂ O ₃ · 2SiO ₂ (mullite) (the above third component), Cr ₂ O ₃ , AlN, TiC, TiN, TiCN. , TiB ₂ , Si ₃ N ₄ , Si
C, B ₄ C, WC, TaC, NdC, Cr ₃ C ₂ , Cr ₂ B, ZrN, ZrB ₂ , Zr
C, HfN, HfB ₂ , HfC, BN, and mutual solid solutions thereof (the above second component) are preferable, which are preferable. Especially as the second component, AlN, TiC, TiN, TiCN, TiB ₂ , Si ₃ N ₄ , Si
Al ₂ O ₃ is preferable as C, B ₄ C, WC, TaC and NdC as the third component.

The manufacturing method of the present invention is usually carried out as follows. Y ₂ O ₃
And ZrO ₂ powder or Y ₂ O ₃ and CeO ₂ and ZrO ₂ powder containing CeO ₂ as a stabilizer, Al, Si as a dispersion powder,
B, powder containing one or more powders selected from boride, carbide, nitride and Cr ₂ O _{3 of} group 4a, 5a and 6a of the periodic table in an amount of 1 to 70% by weight. After pulverizing and mixing, or Al, Si, B as a dispersion component, Periodic Table 4a,
One or more powders selected from borides, carbides, nitrides and Cr ₂ O _{3 of} 5a and 6a group elements, and Al ₂ O ₃ and MgO.Al ₂
O ₃ (spinel), 3Al ₂ O ₃ · 2SiO ₂ After the powder was added in a range of 1 to 70 internal wt% in total of one or more powders selected from (mullite) were mixed and ground, must the predetermined shape by adding a molding aid such as polyvinyl alcohol in accordance with, the atmosphere when the dispersion component is an oxide, in vacuum, in an oxygen atmosphere, a hydrogen atmosphere, N _2, such as argon gas- active gas atmosphere, also in a vacuum if the dispersion component comprises a non-oxide, N _2, an inert gas atmosphere such as argon gas in a non-oxidizing atmosphere, atmospheric pressure, under pressure, from 1,350 to 1,650
Bake for 0.5 to 5 hours at ℃.

Particularly when the amount of the non-oxide dispersed component is large, it is preferable to apply the hot pressing method (HP method) or the hot isossotactic pressing method (HIP method). In the case of HP method, the molded product is loaded into the mold in a non-oxidizing atmosphere and
Baking at 1350 to 1650 ° C under a pressure of 0 kg / cm ² . In the case of the HIP method, after obtaining a non-breathable sintered body with a relative density of 95% or more in advance by atmospheric pressure sintering, gas pressure sintering, hot pressing, etc., 1000 kg / cm ² in a hot isostatic press. Above gas pressure, 1100 ℃ or above 18
It is preferable to perform sintering for 0.5 hr or more under the temperature condition of 00 ° C. Alternatively, a method in which the mixed powder is filled in a capsule and hot isostatic pressing is performed as it is is also suitable.

As the ZrO ₂ powder, a specific surface area of 10 m ² / g or more, preferably 15
m ² / g or more, more preferably 25 m ² / g or more is used.

The partially stabilized zirconia of the present invention comprises a raw material obtained by uniformly mixing a sol of ZrO ₂ and / or a water-soluble salt with a water-soluble salt of a stabilizer in a solution state, and then separating it in the form of a precipitate. If used, the stabilizer can be uniformly dispersed in ZrO ₂ , and a raw material can be an easily sinterable powder composed of extremely fine particles. As a result, a sintered body having fine particles and a uniform composition and almost no micropores is obtained, and initial values of strength and toughness are obtained.

In the present invention, the purity of the raw material used as the dispersion component is
It is preferably 98% or more, but 90 to 98% can be effectively used. In the case of ultrafine particles, it is appropriate to express the specific surface area by the specific surface area rather than the average particle diameter. To achieve the object of the present invention, a specific surface area of 5 m ² / g or more, preferably 10 m ² / g or more is used. Good to do.

Incidentally, the high toughness ceramic sintered body of the present invention, the relative density of the sintered body is preferably 95% or more in order to enhance heat stability,
More preferably 98% or more (more preferably 99% or more,
Most preferably, it is 99.5% or more). Further, the higher the relative density, the higher the stability of the tetragonal zirconia contained in the sintered body, and the better the heat stability, the strength and the toughness.

Since the zirconia sintered body having the composition of the present invention is a partially stabilized zirconia mainly composed of tetragonal crystals, it has high strength.
Shows high toughness. Since the tetragonal system is a metastable phase by nature, a part of the sample surface is transformed into a monoclinic structure by grinding and the residual compressive stress of the surface layer contributes to strengthening of the sintered body. The degree of this strengthening depends on the surface roughness due to grinding and the grain size of the sintered body. Therefore, the partially stabilized zirconia mainly composed of tetragonal crystals according to the present invention means zirconia containing at least 50% or more of tetragonal system in a mirror state in the measurement of the crystal phase by X-ray diffraction. If the tetragonal system is 50 or less, the toughness is lowered, so that it is necessary that the tetragonal system is contained in 50% or more.

In the sintered body of the present invention, the average crystal grain size of tetragonal zirconia contained in the sintered body needs to be 2 μm or less. It is preferably 1 μm or less. More preferably, it is 0.5 μm or less. Average crystal grain size is 2 μm
If it exceeds 1.0, it changes to monoclinic and the toughness decreases. Further, the smaller the average particle size of the tetragonal zirconia, the higher the stability and the more excellent the heat resistance stability becomes.

In the present invention, the average crystal particle size of zirconia is CuKα
It was carried out by an X-ray diffraction method using an X-ray, and was obtained from the equation as D = 0.89λ / (B−b) cos θ. Here, D is the crystal grain size of the zirconia to be obtained, λ is the wavelength of the CuKα line, 1.541, and B is the largest half-value width (radian) of the diffraction line of the monoclinic (111) plane or tetragonal (111) plane of zirconia. Value, b is the half-value width (radian) of the (101) plane of α-quartz with a crystal grain size of 3000 or more to be added as an internal standard, and θ is the diffraction angle 2θ of the diffraction line used to measure the half-value width of zirconia The value is / 2.

The ZrO ₂ of the zirconia sintered body of the present invention exhibits the same characteristics even if a part or more of the ZrO ₂ is replaced with HfO ₂ .

[Examples] Examples of the present invention will be described below to clarify the effects of the present invention.

(Example 1) Purity 99.9% so that the obtained powder has the ratio shown in Table 1.
To a zirconia sol solution obtained by hydrolysis of an aqueous solution of zirconium oxychloride, 99.9% pure yttrium chloride and 99.9% pure cerium chloride were added, and the homogeneously mixed solution was condensed with an alkali to form a hydroxide precipitate. ,
This was dehydrated and dried, and calcined at 900 ° C. to obtain partially stabilized zirconia powder. This powder exhibits a specific surface area of 25 m ² / g.

To this powder, Al ₂ O ₃ having an average particle size of 0.3 μm and a purity of 99.9% and fine TiN having an average particle size of 0.1 μm and a purity of 99.9% were added at the ratio shown in Table 1, and the powder obtained by wet mixing and drying was added to 1.5 ton. It was molded isotropically at a pressure of / cm ² and fired in nitrogen at a temperature of 1400-1650 ° C. for 2 hours. The average crystal grain size of the tetragonal zirconia contained in the obtained sintered body was 2 μm or less.

The obtained sintered body was cut and polished into 3 × 4 × 40 mm, and the bulk density, crystal phase, bending strength, fracture toughness, and crystalline phase and bending strength of the surface of the sintered body after the heat deterioration test were measured. The results are shown in Table 1.

As a method of measuring each physical property, bending strength was measured in accordance with JIS standards using a 3 × 4 × 40 mm sample piece, and an average value of 10 pieces was shown by 3-point bending at a span of 30 mm and a crosshead speed of 0.5 mm / min.

The fracture toughness was measured by the microindentation method with an indentation at a load of 50 kg, and the KIC value was calculated using the Nihara's equation.

The quantitative measurement of the crystal phase was performed by the X-ray diffraction method. That is, the integrated intensity IM of the monoclinic (111) face and the (111) face of the sample mirror-polished with diamond paste and the integrated intensity IT, IC of the tetragonal (111) face and the cubic (111) face A more monoclinic amount is It was determined by the formula Next, the sintered body was finely pulverized to 5 μm or less, and the integrated strengths IM ^* and IC ^* of monoclinic ZrO ₂ and cubic ZrO ₂ were determined by X-ray diffraction under the same conditions. It is considered that tetragonal ZrO ₂ existing in the sintered body during the pulverization process is transformed into monoclinic ZrO ₂ by mechanical stress. Therefore, the cubic amount is From this, the tetragonal crystal was determined by (tetragonal crystal amount) = 100-{(monoclinic crystal amount) + (cubic crystal amount)}.

In the heat deterioration test, after holding in an electric furnace at 300 ° C. for 3000 hours, a sample was taken out and the physical properties were measured. The amount of monoclinic crystals after the heat deterioration test is the same as the above (1) according to the X-ray diffraction of the sample surface.
Calculated from the formula.

In this example, a fixed amount of Al ₂ O ₃ and TiN (20% by weight and 10% by weight in this example) were added as additive components, and YO _1.5 was gradually increased to 0 to 10 mol% while CeO ₂ was gradually increased. Was added at various mol%.

In Table 1, the examples of the present invention have a bending strength of 100 kg / mm ² or more after the heat deterioration test, while the comparative examples show a much lower strength. In addition, when looking at the monoclinic crystals after the same test, those that greatly increased show deterioration in bending strength. (The same applies to the following examples.) In Table 1, sample Nos. 1 to ₅ are obtained by not adding YO _1.5 at all and gradually increasing the number of moles of CeO ₂ added. Comparative Example No. 1 contains less CeO ₂ than the composition point D on the triangular coordinate showing mol% of ZrO ₂ , YO _1.5 , and CeO ₂ , but the amount of monoclinic crystals after the heat deterioration test is large. Bending strength is extremely low. On the contrary, No. 5 containing a larger amount of CeO ₂ than the composition point E of the triangular coordinate has low fracture toughness and bending strength. On the other hand, an example of the present invention having a composition between point D and point E
Nos. 2 to 4 exhibited high values of relative density, fracture toughness, and bending strength, and it was found that no transition to monoclinic crystals was observed even after the heat deterioration test, and bending strength hardly deteriorated.

Sample Nos. 6 to 9 have YO _1.5 at 2.5 mol% and CeO ₂ addition mol%
Is a change. Comparative example No. 6 is ZrO ₂ , Y
The composition is out of the range surrounded by five composition points of ABCDE in the triangular coordinate showing the molar percentage of O _1.5 and CeO ₂ , which is less on the side with less CeO ₂ , but the bending strength and fracture toughness are both high values. However, there are many monoclinic crystals after the heat deterioration test, and the deterioration of strength is remarkable. Sample No. 9 is a comparative example in which there is more CeO ₂ than the range surrounded by the five composition points of ABCDE in the triangular coordinate showing the mol% of ZrO ₂ , YO _1.5 , and CeO ₂ , but the relative density Although high, the fracture toughness and bending strength cannot be sufficiently obtained.
On the other hand, in Invention Examples Nos. 7 to 8 which are within the range surrounded by the five composition points of ABCDE in the triangular coordinate, both fracture toughness and bending strength were high, and the monoclinic crystal was obtained by the heat deterioration test. It was confirmed that no change in strength occurred and no deterioration in strength was observed.

Sample Nos. 10 to 14 had a YO _1.5 composition of 4 mol% and had a CeO ₂ addition mo
It is a variation of l%. Comparative Example No. 10 has no CeO ₂ added and is outside the range surrounded by the five composition points of ABCDE in the above-mentioned triangular coordinate, but both bending strength and fracture toughness show high values, but thermal degradation There are many monoclinic crystals after the test, and the deterioration of strength is remarkable. In addition, CeO ₂ is AB of the above-mentioned triangular coordinate.
Comparative Example No. 14, which was added more than the range surrounded by the five composition points of CDE, had a high relative density but could not obtain sufficient values for fracture toughness and bending strength. On the other hand, in the invention examples Nos. 11 to 13 in which the amount of CeO ₂ added was in the range surrounded by the five composition points of ABCDE in the above-mentioned triangular coordinates, both fracture toughness and bending strength were high, and the heat deterioration test was performed. It was clarified that the transition to monoclinic crystal did not occur and the strength did not deteriorate.

Similarly, sample Nos. 15 to 18 have a YO _1.5 composition of 6 mol%, and sample Nos. 19 to 22 have a YO _1.5 composition of 8 mol%, and each CeO ₂ is added to 0 to 12 mol%. , Sample No.
No. 23 has a composition of YO _1.5 of 10 mol% and 2 mol% of CeO ₂ added. No. 15 which is a comparative example without adding CeO ₂ at all
In No. 19 and No. 19, although the relative density was high, there were many transitions to monoclinic crystals after the heat deterioration test, and the bending strength was significantly deteriorated. Also,
The CeO _2, the ZrO _2, YO _1.5, is more comparative examples were added than the range surrounded by the 5 composition point of ABCDE of the triangular coordinates displaying the mol% of CeO ₂ No.18 and No.22, the relative Although the density is high, sufficient values cannot be obtained for fracture toughness and bending strength. In comparison with this, m of ZrO ₂ , YO _1.5 , and CeO ₂ , which are composition ranges of the present invention, are compared.
Sample Nos. 16 to 17 and No. ₂₀ to ₂ containing YO _1.5 and CeO ₂ within the range surrounded by 5 composition points of ABCDE with triangular coordinates showing ol%
In No. 1 and No. 23, both high fracture toughness and high bending strength were obtained, and it was confirmed by the heat deterioration test that the transition to monoclinic crystal did not occur and the strength was not deteriorated. In addition,
It was confirmed that the same results as in this example were obtained with other dispersion components and addition amounts of the present invention. NO.23 shows an example close to the lower limit of 50% of tetragonal.

Example 2 To monoclinic zirconia having a specific surface area of 25 m ² / g and a purity of 99% or more, Y ₂ O ₃ and CeO ₂ as stabilizers were added at the ratios shown in Table 2 and added thereto. Average particle size of 0.3μ
m, purity 99.9% Al ₂ O ₃ , average particle size 0.3 μm, pure 99.9%
MgO ・ Al ₂ O ₃ (spinel), specific surface area 28 m ² / g, Al ₂ O ₃ / SiO
₂ Synthetic mullite (3Al ₂ O ₃ · 2SiO ₂ ) with a ratio of 71.8 / 28.2,
Cr ₂ O _{3 with an} average particle size of 0.5 μm and a purity of 99% and a purity of 98% or more,
AlN, TiC, TiN, TiCN, TiB ₂ , Si _{3 with a} specific surface area of 10 m ² / g or more
N ₄ , SiC, B ₄ C, WC, TaC, NbC, Cr ₃ C ₂ , Cr ₂ B, ZrN, Zr
B _2, ZrC, added at a rate of _2, BN Table 2 HfB, filled with powder obtained by drying after the wet mixture in a carbon mold, 200kg / cm ^2, 140
Firing was performed for about 1 hour by the hot pressing method under the condition of 0 to 1500 ° C.

The average crystal grains of tetragonal zirconia contained in the obtained sintered body were all 2 μm or less. The obtained sintered body is
The bulk density, crystal phase, flexural strength, fracture toughness, and crystal and flexural strength of the crystal surface after the heat deterioration test were measured in the same manner as in Example 1, and the results are shown in Table 2.

In this example, 3 mol% of YO _1.5 and 6 of CeO ₂ were used as stabilizers.
Mol% was added, and 30% by weight of various dispersion components were added thereto.

Sample Nos. 28 to 31, 33 to 34 are AlN, TiC, TiN, TiCN, Si ₃ N
₄ , SiC alone is added at 30% by weight. In addition, sample Nos. 27, 32, 36 to 43, and 45 are Al ₂ O ₃ 25 wt%, Cr
₂ O ₃ , TiB ₂ , B ₄ C, WC, TaC, NbC, Cr ₃ C ₂ , Cr ₂ B, ZrN, Zr
5% by weight of B ₂ , ZrC and BN are added respectively,
Sample Nos. 44 and 46 contain 25% by weight of Si ₃ N ₄ and HfB ₂ or TiN.
5% by weight is added. As is clear from Table 2, both the dispersion component added alone and the two types added both contained about 90% of tetragonal crystals in ZrO ₂ and had high relative density, fracture toughness and bending strength. In the heat deterioration test, no transition to monoclinic crystals was observed, and bending strength was hardly deteriorated. Sample No. 47 is a comparative example containing only Y ₂ O ₃ as a stabilizer, but even if a total of 30% by weight of the dispersant was added, the heat deterioration was severe, and after the heat deterioration test, simple deterioration was observed. The amount of orthorhombic crystals increases, and bending strength deteriorates significantly.

(Example 3) Purity 99.9% so that the obtained powder has the ratio shown in Table 3.
Zirconia sol solution obtained by hydrolysis of zirconium oxychloride solution in water was added with yttrium chloride with 99.9% purity and cerium chloride with 99.9% purity, and the uniformly mixed solution was condensed with alkali to precipitate hydroxide. This was dehydrated, dried, and calcined at 900 ° C. to obtain a partially stabilized zirconia powder. This powder exhibits a specific surface area of 25 m ² / g.

This powder contains Al ₂ O ₃ with an average particle size of 0.3 μm and a purity of 99.9%, and TiCN, SiC, Si _{3 with a} specific surface area of 10 m ² / g or more and a purity of 98% or more.
N _4, AlN was added at a ratio of Table 3 as a dispersion component, a powder obtained by drying after the wet mixing, shaping isotropically at a pressure of 1.5 ton / cm ^2, 2 hours at a temperature of from 1,350 to 1,500 ° C. Pre-sinter, or
Alternatively, hot pressing was performed at 200 kg / cm ² 1350 to 1500 ° C. for 1 hour to obtain a non-breathable sintered body having a theoretical density of 95% or more. This sintered body was subjected to a pressure of 2000 kg / cm ^{2 in} an Ar gas atmosphere at 1450 to
Sintering was performed in a hot isostatic press at 1600 ° C for 1 hour. The average particles of tetragonal zirconia contained in the obtained sintered body were all 2 μm or less.

The obtained sintered body was measured for bulk density, crystal phase, bending strength, fracture toughness, and crystal and bending strength on the surface of the sintered body after the heat deterioration test in the same manner as in Example 1, and It is shown in Table 3. No. 48 to 52, No. 60 and No. 65 to 76 are missing numbers.

In Table 3, sample Nos. 53 to 54 are 4 mol as stabilizers.
% YO _1.5 and 4 mol% CeO ₂ were added, and three kinds of dispersion components, Si ₃ N ₄ , Al ₂ O ₃ and AlN, were added in a total amount of 50 to 70% by weight. 0.55 to 56 have the same amount of stabilizer and 25 to 40% by weight of Si ₃ N ₄ is added as a dispersion component. Sample Nos. 57 to 59 also have the same amount of stabilizer, and as a dispersion component, Al ₂ O ₃ is combined with Sic and TiCN at 25 to 40.
It is the one added by weight%. Relative density of all samples,
The fracture toughness and the bending strength are both high, and the transition to the monoclinic crystal was not measured even after the thermal deterioration test, and the bending strength was hardly deteriorated, and the effect of the present invention was confirmed.

In Sample Nos. 61 to 63, YO _1.5 as a stabilizer was kept constant at 6 mol% and the addition amount of the dispersion component was changed with and without addition of CeO ₂ . In Samples Nos. 61 to 63 in which CeO ₂ was not added at all, even if the dispersive component was added, the heat deterioration was remarkable, and after the heat deterioration test, the crystals were transformed into monoclinic crystals, and the bending strength was significantly deteriorated. Sample No. 64 is
This is a comparative example in which 6 mol% of YO _1.5 and _1.5 mol% of CeO _{2 are} added as stabilizers and no dispersing component is added, but thermal deterioration similarly occurs.

Further, among the samples of this example, No. 55 to 57, 59, and 61 were measured for hardness with a load of 45 kg using a Rockwell Superficial hardness meter, and the results are shown in Table 4.

From Table 4, sample N which is an example of the present invention in which 4 mol% of YO _1.5 and CeO ₂ were added as stabilizers, and a dispersion component was further added
o.55 to 57 and 59 are comparative examples in which only 6 mol% of YO _1.5 is added as a stabilizer and no dispersion component is added.
It can be seen that the hardness is remarkably improved as compared with the partially stabilized zirconia sintered body of No. 61.

Toughened ceramic sintered body having excellent heat stability [Effect of the Invention] The present invention, Y ₂ O ₃ -CeO ₂ -ZrO and ₂ system or partially stabilized zirconia CeO ₂ -ZrO ₂ system, the second component (Borides, carbides and nitrides of elements such as Al and Si, Cr ₂ O ₃ ) or a dispersion component consisting of a second component and a third component (Al ₂ O ₃ , spinel, mullite), and the average By controlling the particle size, the strength is improved and at the same time excellent heat stability, strength,
It is a high toughness ceramic sintered body with extremely little deterioration of toughness due to heat. When the high toughness ceramic sintered body of the present invention excellent in heat stability is used as a sliding member, 3 mol Y ₂ O ₃
Compared with a partially stabilized zirconia sintered body, about 10 times or more abrasion resistance is obtained. As described above, the present invention improves the hardness of the partially stabilized zirconia sintered body and further improves the wear resistance. Moreover, by adding the dispersant component, the mechanical properties such as hardness, strength, and creep are excellent as compared with the conventional zirconia sintered body at high temperature.

The high toughness ceramic sintered body having excellent heat stability of the present invention has excellent properties at room temperature and high temperature as described above, and therefore, the wear resistant ceramic screw and brass rod for injection molding machines of thermoplastic resins and ceramics. Extrusion dies such as copper and copper pipe shells, gas turbine parts, internal combustion engines such as diesel engine parts, pump parts, industrial cutters, cutting tools, parts for grinding machines, sliding members, artificial bones, artificial teeth, cast ceramics It greatly contributes to application and practical application to mechanical tools such as bridge core materials for artificial teeth, artificial tooth roots, and gauges, and performance improvement.

[Brief description of drawings]

Figure 1 shows triangular coordinates showing the composition range of ZrO ₂ , YO _1.5 , and CeO _2.

Claims (11)

[Claims] 1. For partially stabilized zirconia mainly composed of tetragonal crystals containing Y ₂ O ₃ and CeO ₂ or CeO ₂ as a stabilizer, Al, Si, B and 4a, 5a of the periodic table as second components, A sintered body containing 1 to 70% by weight of one or two or more selected from boride, carbide and nitride of a 6a group element, and Cr ₂ O ₃ , which is a tetragonal contained in the sintered body. A high toughness ceramic sintered body, characterized in that the average particle size of the crystal grains of cubic zirconia is 2 μm or less and that it has excellent heat resistance stability. 2. The high toughness ceramic sintered body according to claim 1, which is sintered by a hot pressing method or a hot isostatic pressing method. 3. Partially stabilized zirconia is included in this.
As shown in the attached drawing, Y ₂ O ₃ and CeO ₂ intersect with an equilateral triangle, and the three axes intersecting ZrO ₂ , YO _1.5 , and CeO ₂ , respectively, in the triangular coordinates, point A (ZrO ₂ 87.5 mol%, YO _1.5 12mol%, CeO ₂ 0.5mol%) Point B (ZrO ₂ 95.5mol%, YO _1.5 4mol%, CeO ₂ 0.5mol%) Point C (ZrO ₂ 95.5mol%, YO _1.5 2mol%, CeO ₂ 2.5mol%) connecting the point _{D (ZrO 2 92.0mol%, YO} 1.5 0mol%, CeO 2 8.0mol%) point _{E (ZrO 2 84.5mol%, YO} 1.5 0mol%, CeO 2 15.5mol%) specific 5 composition point indicated by The high toughness ceramic sintered body according to claim 1 or 2, which has a composition within a range surrounded by dots. 4. The second component is AlN, TiC, TiN, TiCN, T
iB ₂ , Si ₃ N ₄ , SiC, B ₄ C, WC, TaC, NbC, Cr ₃ C ₂ , Cr ₂ B, Z
The high toughness ceramic calcination according to any one of claims 1 to _3, which is at least one selected from rN, ZrB ₂ , ZrC, HfN, HfB ₂ , HfC, BN and Cr ₂ O _3. Union. 5. The method according to any one of claims 1 to 4, wherein the amount of zirconia monoclinic crystals contained in the sintered body after a holding test in air at 300 ° C. for 3000 hours is 30% or less. High toughness ceramic sintered body. 6. A partially stabilized zirconia mainly composed of tetragonal crystals containing Y ₂ O ₃ and CeO ₂ or CeO ₂ as a stabilizer, and Al, Si, B as the second component and Periodic Tables 4a, 5a, One or more selected from borides, carbides and nitrides of 6a group elements, and Cr ₂ O ₃ , and as the third component, Al ₂ O ₃ , MgO.Al ₂ O ₃ (spinel), 3A
l ₂ O ₃・ 2SiO ₂ , 1 or 2 selected from (mullite)
A sintered body containing 1 to 70% by weight of the second and third components in total, and the average particle size of tetragonal zirconia crystal particles contained in the sintered body is 2 μm or less, and High toughness ceramic sintered body characterized by excellent heat resistance stability. 7. ZrO ₂ powder containing Y ₂ O ₃ and CeO ₂ or CeO ₂ as a stabilizer, or the total amount of Y ₂ O ₃ powder, CeO ₂ powder and ZrO ₂ powder, or CeO ₂ powder and ZrO ₂ Based on the total amount of the powder, as the second component, one or two selected from Al, Si, B and boride, carbide and nitride of the elements of 4a, 5a and 6a of the Periodic Table, and Cr ₂ O _3. The average particle size of the tetragonal zirconia crystal particles contained is a ZrO ₂ powder or a mixed powder compact obtained by blending ZrO ₂ powder in the range of 1 to 70% by weight with respect to the total amount. Is 2
A method for producing a high-toughness ceramic sintered body, which comprises sintering to be a sintered body having a particle size of μm or less and excellent heat resistance stability. 8. The composition ratios of Y ₂ O ₃ , CeO ₂ and ZrO ₂ are respectively ZrO ₂ and YO on three axes intersecting an equilateral triangle as shown in the attached drawings.
_1.5, in the triangular coordinates displaying the mol% of CeO _2, the point _{A (ZrO 2 87.5mol%, YO} 1.5 12mol%, CeO 2 0.5mol%) point _{B (ZrO 2 95.5mol%, YO} 1.5 4mol%, CeO 2 0.5 mol%) point _{C (ZrO 2 95.5mol%, YO} 1.5 2mol%, CeO 2 2.5mol%) point _{D (ZrO 2 92.0mol%, YO} 1.5 0mol%, CeO 2 8.0mol%) point E (ZrO ₂ 84.5 mol%, YO _1.5 0mol%, high toughness ceramic sintered to in paragraph 7 of claims in the composition in the range surrounded by the points connecting the specific 5 composition point indicated by CeO ₂ 15.5 mol%) Body manufacturing method. 9. The second component is AlN, TiC, TiN, TiCN, T
iB ₂ , Si ₃ N ₄ , SiC, B ₄ C, WC, TaC, NbC, Cr ₃ C ₂ , Cr ₂ B, Z
Claims 7 or 8 which is one or more selected from rN, ZrB ₂ , ZrC, HfN, HfB ₂ , HfC, BN and Cr ₂ O ₃ .
A method for producing a high toughness ceramic sintered body according to item. 10. A ZrO ₂ powder containing Y ₂ O ₃ and CeO ₂ or CeO ₂ as a stabilizer is a water-soluble ZrO ₂ sol and / or a water-soluble salt which forms Y ₂ O ₃ and CeO _2. The high-toughness ceramic sintered body according to any one of claims 7 to 9, which is a ZrO ₂ powder obtained by uniformly mixing with a salt in a solution state and then separating in the form of a precipitate. Manufacturing method. 11. ZrO ₂ powder containing Y ₂ O ₃ and CeO ₂ or CeO ₂ as a stabilizer, or the total amount of Y ₂ O ₃ powder, CeO ₂ powder and ZrO ₂ powder, or CeO ₂ powder and ZrO ₂ powder. Based on the total amount of the powder, one or two selected from Al, Si, B as the second component and boride, carbide and nitride of the elements of the periodic table 4a, 5a and 6a, and Cr ₂ O _3. and more powders, Al ₂ O ₃ as a third component, MgO · Al ₂ O ₃ (spinel), 3Al ₂
One or more selected from O ₃ .2SiO ₂ (mullite) and ZrO ₂ powder or the total amount of the second and third components in the range of 1 to 70 internal weight% with respect to the total amount. The mixed powder compact thus obtained is fired, and the average particle size of the tetragonal zirconia crystal particles contained is 2
A method for producing a high-toughness ceramic sintered body, which comprises sintering to be a sintered body having a particle size of μm or less and excellent heat resistance stability.