JP2690571B2 - Zirconia cutting tool and its manufacturing method - Google Patents

Description

The present invention relates to a cutting tool made of a zirconia-based sintered body having high strength and high toughness as well as high hardness and high thermal conductivity, and a method for manufacturing the cutting tool.

[Conventional technology]

In recent years, attention has been paid to ceramics as a material for high-speed cutting tools, and tools such as Al ₂ O ₃ , Al ₂ O ₃ -TiC, and SiN ₄ series have already been developed.

However, these conventional ceramic tools
Although it shows excellent cutting performance with respect to cast iron, steel, etc., it has the drawback that it lacks strength and toughness due to its material and is susceptible to chipping. Furthermore, it has been difficult to cut aluminum alloys and copper alloys because of their high chemical affinity with the metal to be cut.

Therefore, in recent years, application of zirconia-based materials having excellent strength and toughness to tools has been attempted, and in Japanese Patent Publication No. 58-9784, Y ₂ O ₃ , CaO and MgO called so-called partially stabilized zirconia are called.
A zirconia-based cutting tool partially stabilized with at least one of the above is disclosed. However, these partially stabilized zirconia cutting tools have the drawbacks of insufficient hardness and high wear.

Therefore, various improvements have been made. Among them, JP-A-60-239357 discloses a zirconia-based cutting tool called high-strength zirconia. This cutting tool contains ZrO ₂ 50-30 containing 1.5-5 mol% Y ₂ O _3.
A high-strength zirconia-based cutting tool characterized by comprising 50% by weight of Al ₂ O ₃ or 50 to ₂ % by weight of spinel (Mg AlO ₄ ) and having a three-point bending strength of 1700 MPa or more.

[Problems to be solved by the invention]

However, while a cutting tool made of a zirconia-based sintered body having these compositions has excellent strength and toughness, it still has the required properties such as hardness and thermal conductivity as a cutting tool,
There is a problem of poor thermal stability.

Particularly, partially stabilized ZrO ₂ has a thermal conductivity of 0.007c.
Al / cm ・ sec ・ ° C is the lowest among ceramics, and as a result, when using a cutting tool made of zirconia sintered body, the friction heat generated by friction between the metal to be cut and the tool is not propagated well At present, it cannot be used satisfactorily due to abnormal heat storage phenomenon and seizure.

The problem to be solved in the present invention is, without losing the excellent strength and toughness originally possessed by the high-strength zirconia sintered body,
It is to find out the control conditions for exhibiting the excellent thermal conductivity and hardness required for a cutting tool.

[Means for solving the problem]

The zirconia-based cutting tool of the present invention comprises a zirconia ceramic component and 10 to 50% by volume of WC, SiC, AlN, TiN, ZrB ₂ and T.
The composite zirconia-based sintered body contains at least one ceramic component selected from iB ₂ .

In the present invention, as the zirconia ceramics component, one in which one kind of oxide of Y ₂ O ₃ , MgO, CaO or CeO ₂ is in solid solution is used, but a combination thereof may be used. In addition to this, a small amount of a rare earth oxide such as La ₂ O ₃ , Yb ₂ O ₃ or Er ₂ O ₃ may be added for stabilization.

Zirconia that does not contain oxides such as Y ₂ O ₃ and MgO has a crystal structure at high temperatures of tetragonal, cubic, or a mixed phase of tetragonal and cubic, and the tetragonal crystal transforms to monoclinic during cooling. At that time, volume expansion is accompanied, and as a result, the ceramic is destroyed.
In order to avoid this, oxides such as Y ₂ O ₃ and MgO are solid-dissolved in pure zirconia for stabilization. As a result, the crystal structure of zirconia after sintering is tetragonal, a mixed phase of tetragonal and cubic, or cubic.

In some cases, these crystal structures may partially include a monoclinic structure, but the amount thereof is 10% based on the whole.
It is preferably not more than mol%.

The type of crystal structure described above depends on the type and proportion of the stabilizer to be added. In order to obtain a zirconia-based sintered body with excellent strength and toughness, Y ₂ O ₃ should be 2 to 5 mol%, MgO
6 to 10 mol%, CaO to 4 to 9 mol%, and CeO ₂ to 8 to 15 mol% as a solid solution to form a tetragonal system with a crystal structure of 50 mol% or more. To do.

The zirconia-based ceramics of the present invention are WC, SiC, AlN, T
It is a composite ceramic compounded with at least one selected from the group consisting of iN, ZrB ₂ and TiB ₂ .

However, the added ceramic component is WC, AlN, T
For iN, ZrB ₂ and TiB ₂ , at less than 20% by volume, S
In the case of iC, if it is less than 30% by volume, the thermal conductivity of the zirconia-based sintered body cannot be increased, and when used as a cutting tool, the effect against heat generation due to friction is reduced. Further, if the addition amount exceeds 50% by volume, a dense zirconia-based sintered body cannot be obtained, and mechanical properties such as strength, toughness and hardness deteriorate.

As described above, the total amount of the ceramic component added to form a composite with the zirconia ceramic component is high in the above volume%, and the contribution ratio of the parallelized model is high.

Furthermore, the zirconia-based cutting tool of the present invention is WC, SiC, A
lN, TiN, ZrB ₂ and TiB _{2 and the} like, in the composite ceramic composition consisting of the group IVa, Va, VIa group element boride, carbide, nitride, their composites and at least alumina One type may be contained in an amount of 20% by volume or less. By adding the second composite ceramic component, a dense zirconia-based sintered body can be obtained at a low temperature, a sintered body excellent in strength and hardness can be obtained, and electric conductivity is improved. Or, the thermal shock strength can be improved.

Furthermore, the zirconia-based cutting tool of the present invention is required to have a contribution ratio γ _P of the parallelized model in the compound rule in the range of 0.2 to 0.6.

In the present invention, the contribution rate γ _P of the parallelized model is defined as follows.

When the thermal conductivity K of the zirconia-based sintered body is replaced with an equivalent electric circuit, the heat flow velocity corresponds to the electric current, the temperature difference corresponds to the voltage, and the thermal conductivity corresponds to the electric conductivity.

Therefore, if the thermal conductivity of a zirconia-based sintered body made of two different types of ceramics is K, the thermal conductivity of each ceramic is K ₁ , K ₂ , and the volume fractions are V ₁ , V ₂ , the series The thermal conductivity K _D for the model is Can be represented as

Further, in the parallel type model, the thermal conductivity K _P is expressed as K _P = V ₁ K ₁ + V ₂ K ₂ (2), where one or more additives are added to zirconia as a zirconia-based sintered body. In the case of the contained composite ceramics sintered body, the same definition can be made. Therefore, the general formula of the n component K _{D in} the case of the series model is Can be represented as

Moreover, the general formula of n components · K _P in the case of parallel _{models, K P = V 1 K 1} + V 2 K 2 + V 3 K 3 + ·· + V n K n ...... (4) become.

Here, a two-component zirconia-based sintered body containing, for example, ZrO ₂ and WC will be described as an example.

Assuming that each component hardly forms a solid solution, K of the composite zirconia-based sintered body is K = K _D γ _D ＋ K _P γ _P …… from the combination of the thermal conductivity of the series type and the parallelized model. (5) However, γ _D + γ _P = 1 (6)

Here, γ _D is the serial contribution rate, and γ _P is the parallel contribution rate.

As a result, the contribution ratio γ _P of the parallelized model in the compound rule of the zirconia-based sintered body is calculated from the equations (1), (2), (5) and (6). Can be represented as

FIG. 1 to FIG. 3 show the dispersion state of the ceramic component particles (WC) in the zirconia (ZrO ₂ ) as an equivalent electric circuit.

FIG. 1 shows a series type, FIG. 2 shows a parallel type, and FIG. 3 shows a mixed type as a model. That is,
The distribution form in each figure is on the left side, the equivalent electric circuit is on the right side, and the relational expressions (corresponding to the above relational expressions (3) and (4)) between the thermal conductivities K _D and K _P at that time are respectively given as Shown in Figures 1 and 2. Further, FIG. 3 shows the relationship in the dispersion state of the ceramic component particles (WC) in the zirconia (ZrO ₂ ).
It is shown as expressed by the above relational expressions (5) and (6).

That is, K is the thermal conductivity of the zirconia-based sintered body, K ₁
If V ₁ is the thermal conductivity and capacity% of ZrO ₂ , and K ₂ and V ₂ are the thermal conductivity and capacity% of the added ceramics component, respectively,
These relationships can be expressed by the above respective relational expressions, and particularly in the present invention, the contribution ratio expressed as γ is a control factor for the zirconia-based ceramics.

Furthermore, the thermal conductivity of the size, strength, the parallel type of contribution gamma _P in terms of mechanical properties such as hardness, and controls the degree of dispersion of the ceramic components, gamma _P in the above (7) When 0.5 is 0.5, it is considered to be a structure in which ZrO ₂ and WC are uniformly dispersed. In the present invention, γ _P according to the equation (7) is 0.2 to 0.
A range of 6 is acceptable. Preferably, it is controlled to be 0.4 to 0.6.

When it is less than 0.2, ZrO ₂ and WC have a non-uniform structure, resulting in a decrease in porosity, strength and hardness. On the other hand, when it exceeds 0.6, the thermal conductivity is improved but the porosity and the strength are lowered.

The contribution ratio in the compounding rule is the structure of the zirconia-based sintered body, that is, the particle size of the ZrO ₂ and the additive, the shape and morphology of the particle, and the distribution of the particle size, that is, the dispersed state of the particle, the size and distribution of the pores, and the sintered body It is considered that this depends on the fine structure of, that is, the bonding state of the grain boundary between ZrO ₂ and WC and the structure inside the grain.

By setting the parallel type contribution ratio γ _P within the above range, a sintered body having high thermal conductivity and excellent hardness, strength and thermal shock strength can be obtained. Further, in the preferable range of 0.4 to 0.6, a more uniform structure is obtained, and one having excellent mechanical and thermal properties is obtained.

Further, the zirconia-based sintered body of the present invention is improved in the disadvantage that the high-temperature strength of conventional high-strength zirconia is low,
Even at 0 ° C or higher, there is an advantage that the strength is not significantly reduced.

The reason for this is not clear, but due to the uniform dispersion of ceramic components that are difficult to plastically deform in ZrO ₂ even at high temperatures, crack propagation due to the dispersion strengthening mechanism and the interaction between precipitates and cracks, etc. Is suppressed at high temperatures, so high temperature strength is considered to improve.

The particle size of the zirconia-based sintered body of the present invention is preferably such that the particle size of ZrO ₂ is in the range of 0.3 to 0.8 μm. 0.3μ
When m or less, the tetragonal zirconia particles are transformed into monoclinic crystals to improve the strength and toughness. As a result, the action of a so-called stress-induced transformation mechanism is reduced, resulting in a reduction in strength and toughness. On the other hand, if it exceeds 0.8 μm, the tetragonal zirconia particles are easily transformed into monoclinic zirconia in the cooling process after sintering, resulting in a decrease in strength and toughness.

In addition, in a sintered body in which AlN is added to zirconia, zirconia reacts with AlN depending on the sintering temperature and atmosphere, and Al ₂ O ₂
In some cases, a compound such as or ZrN is formed. Also, ZrO ₂ and S
iC reacts to form another compound (for example, glass phase) at the grain boundary, and cubic or tetragonal ZrO ₂ grain refinement or tetragonal
The transformation of ZrO ₂ particles into monoclinic crystals causes a problem such as a decrease in strength.

Therefore, the grain structure of the zirconia-based sintered body of the present invention, zirconia particles and WC, SiC, AlN, TiN, ZrB ₂ and TiB ₂
The particles of the ceramic component such as etc. do not form a solid solution with each other,
It is preferred that they are evenly dispersed in each other.

Here, in order to avoid the reaction between ZrO ₂ and AlN, it is effective to form a film of Al ₂ O ₃ particles around the AlN particles in the process of preparing the mixed powder and sinter. An Al ₂ O ₃ film can be formed around AlN by using a powder obtained by heat treating AlN powder in air at a temperature of 300 ° C. to 800 ° C. for several hours to several tens of hours.

In order to avoid the reaction between ZrO ₂ and SiC, Al
_It is effective to use a mixed powder containing 1 to 10% by weight of ₂ O ₃ , Er ₂ O ₃ , B ₄ C or C.

The zirconia-based cutting tool material of the present invention having the above characteristics can be manufactured, for example, as follows.

First, zirconia powder with a purity of 99.5% or higher has a purity of 9
9.5% or more of yttria (Y ₂ O ₃ ), magnesia (MgO), calcia (CaO), and ceria (CeO ₂ ) at least one oxide is a solid solution powder, and the purity is 99.5% 20
A mixed powder with at least one ceramic powder selected from ˜50% by volume of WC, AlN, TiN, ZrB ₂ , TiB ₂ , and 30 to 50% by volume of SiC is prepared.

The mixed powder is wet-mixed and pulverized by a ball mill or an attritor so that the 90% particle diameter is 2 to 4 μm, the 50% particle diameter is 0.5 to 1.0 μm, and the specific surface area is 3 to 15 m ² / g. Next, the slurry of the mixed powder is granulated and dried by a spray dryer, or dried by uniformly stirring with a mixer or the like to prepare a homogeneous dry powder.

In particular, in order to make the contribution ratio of the compound rule in the range of 0.2 to 0.6, 90% particle diameter is 2 to 4 μm, 50% particle diameter is 0.5 to
WC, SiC, AlN, Ti with 1.0μm and specific surface area of 1.5-15m ² / g
After uniformly wrapping around the N, ZrB ₂ and TiB ₂ powder with a sol of Y ₂ O ₃ , MgO, CaO or CeO dissolved in ZrO ₂ , the mixture was mixed.
By calcining at 500 ° C to 900 ° C, pulverizing, and then granulating or drying with uniform mixing with a mixer etc.
It is preferable to prepare a ZrO ₂ based powder. At this time, a dispersant can be used if necessary in order to reduce aggregation. When granulating and stirring and drying, a predetermined zirconia and additive components are mixed in a slurry. In wet mixing with a mixer, etc., the ratio of powder to solvent (water, acetone, etc.),
When mixing and pulverizing with a ball mill or attritor, powder,
Selection is made to optimize the respective proportions of solvent and balls. At this time, by using a static drying method such as an ordinary dryer, zirconia powder in which the above oxide is a solid solution,
That is, it is a partially stabilized zirconia powder and an additive component.
Due to the large difference in specific gravity from WC, SiC, AlN, TiN, ZrB ₂ and TiB _2, etc., the zirconia powder and additive components will aggregate separately, resulting in a homogeneous sintered body after molding and sintering. Cannot be achieved, resulting in a decrease in thermal conductivity, strength, hardness, etc. More preferably, the powder after granulation and drying is pulverized with the amount of the solvent being half or less of the amount of the usual mixed pulverization, and dried while preventing precipitation, so that a more homogeneous powder can be obtained.

The additive component used in the present invention is inferior in oxidation resistance to zirconia. Therefore, in the granulation drying using an oxidizing solvent such as water, it is necessary to set the rotation speed of the atomizer and the drying temperature condition of the population through which the mixed slurry first passes so that the additive component is not oxidized.
Especially in the case of WC, the drying temperature of the population is 130 to 230 ° C.
In addition, the number of revolutions is set in the range of 10,000 to 15,000 ppm for dry granulation, or granulation and drying are performed by using an organic solvent in a N ₂ or inert gas closed circulation type device with an oxygen partial pressure of 1% or less. By doing so, a homogeneous powder can be obtained without oxidation.

By molding and sintering this powder, a better zirconia-based sintered body can be created.

The above-mentioned mixed powder can be molded by a usual molding method, for example, hydrostatic molding (rubber press), mold molding, injection molding, extrusion molding method or the like, which is used for binder selection and binder degreasing. Unlike oxide ceramics, requires degreasing under neutral or vacuum atmosphere. In the case of the zirconia-based sintered body of the present invention having high thermal conductivity and hardness, and excellent strength, toughness and thermal shock strength, pressure sintering (PAS) or hot pressure molding (hot pressing, HP It is preferable to apply hot isostatic pressing (HIP) after pre-sintering according to (4).

Compared with vacuum sintering and pressureless sintering in a neutral atmosphere, pressure sintering is more convenient for producing a dense sintered body. For example to ZrO ₂
In vacuum sintering, open pores remain in the zirconia-based sintered body containing 20 to 50% by volume of WC, so that a dense sintered body cannot be obtained even by the hot isostatic pressing (HIP). In some cases, when the pressure sintering method is used, the open pores disappear at a relative density of 95 to 97%, so that the HIP treatment is effective in obtaining a sintered body having a theoretical density.

In pressure sintering, a molded body prepared by a normal molding method is treated under an inert atmosphere, for example, in a nitrogen (N ₂ ) or argon (Ar) gas atmosphere, at a pressure of 5 to 300 kg / cm ² and a temperature of 1550 to 1800 ° C. The temperature is raised to and maintained at that temperature. Preferably, the application of pressure sintering at a pressure of 50 to 300 kg / cm ² avoids the additive component reacting with the stabilized zirconia to form another compound during sintering, or the additive component. From the stoichiometric composition, evaporation, or preventing the added components from reacting with carbon or atmospheric gas at high temperature to form another compound. In the case of pressure sintering,
Since the crystal grain growth can be suppressed up to a high temperature, it becomes possible to sinter at a higher temperature.

In hot pressing, the mixed powder is placed in a carbon die of the required shape in a non-oxidizing atmosphere at a pressure of 100 kg / cm ²
As described above, a sintered body is prepared at a temperature of 1450 ° C to 1750 ° C.

Thus, by pressure sintering or hot pressing,
After pre-sintering under the condition that the relative density of the sintered body is 96% or more, preferably 98% or more, the pressure is 1,00 in a non-oxidizing atmosphere.
Sinter by the HIP method at 0 kg / cm ² or more and at a temperature of 1450 ° C to 1700 ° C.

In the above, the relative density of the pre-sintered body is set to 96% or more as compared with the zirconia powder, since the additive component is a hardly sinterable material and plastic deformation is difficult, there is a relative density of 96% or more. This is because a denser sintered body cannot be obtained even by HIP treatment.

Under these conditions 0.015 ~
It is possible to obtain a zirconia-based sintered body having a thermal conductivity K of 0.1 cal / cm · sec · ° C.

〔Example〕

Example 1 Y ₂ O ₃ as a stabilizer containing 2.5 mol% of average particle diameter 0.5 μ
m ZrO ₂ powder and WC (purity 99%, average particle size 0.6 μm), Si
C (purity 99.5%, average particle size 0.4 μm) powder was wet pulverized and mixed into the composition shown in Table 1. 90% particle size of powder after mixing
The powder was 3.2 μm, 50% particle size was 0.9 μm, and specific surface area was 11.5 m ² / g.

Next, this mixed powder was granulated and dried in water while stirring with a mixer. The drying condition is 200 ° C on the inlet side of dry air.
℃, outlet side temperature was 107 ℃, atomizer speed was 12,000 rpm.

Next, the dried powder was rubber-pressed at a molding pressure of ² ton / cm ² and then pressure-sintered. The pressure sintering was performed in an argon atmosphere at a pressure of 50 kg / cm ² at a temperature of 1650 ° C. and 1700 ° C. for 2 hours. The relative density of the pre-sintered body thus obtained is 96.
It was ~ 97.5%.

Next, this pre-sintered body is heated at a temperature in a non-oxidizing gas atmosphere.
A sintered body was obtained by holding at 1550 ° C. and 1600 ° C. under a pressure of 2000 kg / cm ² for 90 minutes and performing hot isostatic pressing (HIP).

For comparison, ZrO ₂ powder containing Y ₂ O ₃ 2.5 mol% as a stabilizer and having an average particle diameter of 1.0 μm and WC (purity 99%, average particle diameter 1.5 μm), SiC (purity 99%, average) Particle size 1.3μ
The powder of m) was wet mixed in a mixer so that the compositions would be 20 and 30% by volume, respectively. The powder after mixing has a 90% particle size of 4.5 μm, a 50% particle size of 1.2 μm and a specific surface area of 6 m ² / g.
Met.

Next, the powder after the wet mixing was statically dried in a dryer. Further, this mixed powder was filled in a graphite mold, and the sintering temperature was set to 1500.
The sintered body was prepared by hot pressing at 200 ° C. and 1600 ° C. under a pressure of 200 kg / cm ² for 1 hour.

Bending test of 3 × 4 × 40 and diameter 19 from these sintered bodies
After forming a test piece for thermal conductivity measurement of × 2 by cutting and processing, the physical properties as shown in Table 1 and the contribution rate of the parallelized model of the compound rule were measured.

From Table 1, it is clear that the cutting tool material of the present invention is a high strength, high toughness material having high thermal conductivity.

Further, it can be seen that when the contribution ratio (γ _P ) of the parallelized model is within the range of the present invention, the thermal conductivity is high, the porosity is low, and the strength (TRS) and hardness are high, which is excellent.

In the table, various physical properties were measured as follows.

(1) Bending strength (TRS) is measured according to JIS R1601, and the average value of 5 is shown.

(2) Vickers hardness is 20kg with Vickers hardness tester
Was measured.

(3) The thermal conductivity was measured by a laser flash method at room temperature (24 ° C) using TXP-400 manufactured by Sanku Engineering.

In addition, from the No. 5 sintered body shown in Table 1, 13 mm square, thickness 5.0 m
A cutting tool sample was prepared by grinding and polishing to have a m and a nose radius of 0.5 mm. Attach these samples to the lathe,
An aluminum alloy containing 13% Si was turned at a cutting speed of 500 m / min, a depth of cut of 1.0 mm, and a feed rate of 0.15 mm / rev. The results of this cutting test are shown in Table 2.

As is clear from Table 2, the zirconia-based cutting tool material of the present invention has less flank wear and is superior to the other ceramic materials without chipping. The turning surface was almost the same as when the diamond tool was used.

Example 2 0.5 μm average particle size containing 2.5 mol% Y ₂ O ₃ as a stabilizer
m of ZrO ₂ powder and WC (purity 99%, average particle size 0.6 μm) were wet pulverized and mixed in the composition shown in Table 3 to obtain the same powder properties as in Example 1.

Furthermore, the ZrO ₂ powder _{above, Er 2 O 3, Al 2} O 3 mixed powder 20% by volume was added and 30 and a volume percent mixed wet milling in SiC,
A powder having the composition shown in Table 3 was prepared.

The powder after mixing was a fine powder having a 90% particle size of 2.5 to 4.0 μm, a 50% particle size of 0.7 to 1.0 μm and a specific surface area of 6 to 11 m ³ / g.

Next, the wet-milled slurry having the above composition was taken out into a container, placed in a vessel kept at a temperature of 90 ° C., and the slurry was uniformly stirred with a mixer to evaporate water and dried.

Furthermore, the powder after drying is filled in a graphite mold and the sintering temperature is set to 15
Hot pressing was carried out at a temperature of 00 ° C. and 1600 ° C. at a pressure of 200 kg / cm ³ for 1 hour to hot-press to prepare a sintered body. Further, this sintered body was HIP-treated under the same conditions as in Example 1 to prepare a sintered body,
The results shown in Table 3 were obtained.

In the sintered body of the present invention, the contribution ratio of the parallelized model of the compound rule is 0.
It can be seen that in the range of 2 to 0.6, the sintered body has high thermal conductivity, hardness, and strength, and has few pores.

From the No. 4 sintered body shown in Table 3, JIS SNGN432 (0.1
× 30 °) was ground and a cutting tool sample was prepared. These samples were attached to a lathe, and non-oxidized copper was turned at a cutting speed of 100 to 300 m / min. The results of this cutting test are shown in Table 4.

As is apparent from Table 4, the zirconia diameter cutting tool material of the present invention has a higher speed than the cemented carbide (JIS V ₁ ; V ₂ ; V ₃ ) which is most often used as a copper and copper alloy cutting tool material at present. It can be seen that cutting is possible and there is little wear. Further, the zirconia-based cutting tool of the present invention showed less copper adhesion and the cutting surface texture was better than that of the cemented carbide tool.

[Advantages of the Invention] The zirconia-based cutting tool material of the present invention has a uniform structure, high thermal conductivity, and excellent mechanical and thermal properties such as strength, toughness, hardness, and thermal shock strength. It can be used effectively even under extremely severe cutting conditions, and because it has low affinity with metals and is chemically stable, it has excellent machinability for difficult-to-cut materials such as aluminum alloys and copper alloys. It is a thing.

[Brief description of the drawings]

FIG. 1 to FIG. 3 are diagrams showing the state of heat conduction in the dispersed state of the ceramic component particles (WC) in the zirconia (ZrO ₂ ) as an equivalent electric circuit.

Claims (2)

(57) [Claims] 1. A zirconia ceramic component, 20 to 50% by volume of WC, AIN, TiN, ZrB ₂ , TiB ₂ , and 30 to 50% by volume of SiC.
A composite zirconia sintered body containing at least one ceramic component selected from, Y ₂ O ₃ wherein the zirconia ceramic component to zirconia, MgO, CaO and CeO ₂
Is a solid solution of at least one oxide selected from the above, and the contribution ratio of the parallelization model in the compound rule is 0.
A zirconia-based cutting tool with a thermal conductivity of 0.015 to 0.1 cal / cm · sec · ° C within the range of 2 to 0.6. 2. A zirconia powder containing 20 to 50% by volume of WC, AIN, T.
A mixed powder containing iN, ZrB ₂ , TiB ₂ and at least one ceramic powder selected from 30 to 50% by volume of SiC was wet mixed and pulverized to have a 90% particle diameter of 2 to 4 μm and
Zirconia characterized in that it is made into a slurry of 50% particle size 0.5 to 1.0 μm and specific surface area 3 to 15 m ² / g fine powder, and then the slurry is dried, and the obtained powder is molded and sintered. Manufacturing method of cutting tools.