JPH09157048A - Composite ceramics and their manufacturing method - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a carbide composite ceramic excellent in unprecedented strength and toughness and a manufacturing method thereof. A composite ceramic comprising a ceramic sintered body containing plate-shaped silicon carbide particles having a solid solution of tungsten boride in the ceramic, which improves brittleness of the carbide ceramic, and which is difficult to apply conventionally. It is excellent as a member that is required to have wear resistance, corrosion resistance, and heat resistance such as a cutting tool, a sliding member, a gas turbine component, and a nuclear component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high toughness ceramic which overcomes the brittleness of ceramics, especially carbide ceramics, and more particularly to a composite ceramic in which plate-like silicon carbide particles are dispersed, a method for producing the same, and its use.

[0002]

2. Description of the Related Art Carbide ceramics have advantages such as high hardness, high abrasion resistance, high melting point, chemical stability, and high corrosion resistance, but have the problem of being brittle. In order to overcome this brittleness, aluminum oxide is used as a sintering aid to achieve toughness by grain growth of silicon carbide particles [Journal of Materials Research (J. Mater. Re.).
s. ), Vol. 8, No. 7, pp. 1635-1643, 19
1993], a method of growing silicon carbide particles by liquid-phase sintering of aluminum oxide or yttrium oxide with a sintering aid [Journal of American Ceramic Society (J. Am. Ceram. Soc.),
Vol. 77, No. 2, pp. 519-523, 1944].

[0003]

It is said that the toughness of ceramics grown by grain growth slightly improves the toughness because the entire structure becomes acicular crystals or columnar crystals, but decreases the strength because the crystal grain size increases. There's a problem. In addition, the needle-like or columnar-crystal silicon carbide particles have a problem that the cracks easily pass through the inside of the grains and do not greatly contribute to the improvement in toughness.

An object of the present invention is to reduce the strength without reducing the strength.
An object of the present invention is to provide a composite ceramic having significantly improved toughness.

[0005]

Means for Solving the Problems In order to solve the above problems, the present inventors have studied various toughness materials with respect to toughening methods using silicon carbide particles of acicular or columnar crystals. As a result, a high-strength and high-toughness carbide ceramic was successfully obtained by dispersing plate-like silicon carbide particles in which tungsten boride was dissolved in a fine carbide matrix.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Plate-like silicon carbide particles in which tungsten boride is dissolved are obtained by sintering a powder obtained by alloying a mixed powder composed of Si powder, C powder, B powder and W powder by mechanical alloying. Is obtained by The powder after mechanical alloying is a fine powder of 1 micron or less,
As a result of powder X-ray diffraction analysis, it was found that β-silicon carbide having a broad diffraction peak was produced.

When this powder is heated to 2000 ° C., it changes into plate-like silicon carbide in which tungsten boride is dissolved. Button-shaped tungsten boride can be observed on the plate-like silicon carbide surface.

FIG. 1 is a schematic diagram showing a button-shaped tungsten boride 2 formed on the surface of a plate-like silicon carbide 1 in which tungsten boride is dissolved. The mechanism by which such plate-like silicon carbide particles are generated is unknown.

[0009] The plate-like silicon carbide particles of the present invention in which tungsten boride is dissolved as solid solution cannot be obtained by simply mixing and sintering tungsten boride and silicon carbide.
Since it cannot be obtained by sintering a mixed powder of B and W, when Si and C react by mechanical alloying to produce silicon carbide, a compound of W and B or a compound of W and B forms a solid solution. (Reaction). Then, it is considered that tungsten boride plays a role of a growth promoter for promoting the growth of the plate-like crystal.

Here, as the powder to be subjected to mechanical alloying, the mixing molar ratio of Si powder and C powder is set to 1: 1 and the mixing molar ratio of W powder and B powder is set to 5: 1 to 1: 5. Thus, plate-like silicon carbide particles in which tungsten boride is dissolved as a solid solution can be obtained efficiently.

The alloy powder can also be obtained by performing mechanical alloying with a tungsten container and tungsten balls or a silicon carbide container and tungsten balls. That is, it is possible to supply and mix a W source from a container or a ball without using W powder as the mechanical alloying raw material powder.

In the powder obtained by mechanical alloying,
2 mass% of boron carbide as a sintering aid, and 1 mass% of polyvinyl butyral (PVB) as a molding binder
Added and mixed with ethanol. By treating the obtained molded body at 2000 ° C. for 1 hour in an Ar atmosphere, a sintered body of plate-like silicon carbide in which tungsten boride is dissolved can be obtained.

Here, by controlling the amount of the sintering aid and the sintering conditions, it is possible to produce a sintered body having a porosity close to 0 to a porous body having a porosity of 40%.

Si, Cr, Ti, Hf, B, Zr, M
An appropriate amount of the powder obtained by mechanical alloying is mixed with a carbide powder composed of at least one of o and W, and a sintering aid and a molding binder are further mixed to form a compact, which is sintered at a high temperature. In the sintered body of fine carbide particles,
It is possible to disperse plate-like silicon carbide particles in which tungsten boride is dissolved. The dispersion amount at this time is 1 to 50 vol.
%, In particular, 5 to 20 vol% is preferable for improving the mechanical properties.

The advantage of the dispersion of the plate-like silicon carbide particles in which tungsten boride is dissolved is that the solid solution of tungsten boride improves the toughness of the particles themselves as compared with the needle-like or columnar silicon carbide particles alone. The point is that the crack detours without passing through the grain. Thereby, it becomes possible to improve the toughness by 1.5 times or more.

FIG. 2 is a schematic view of a carbide sintered body in which plate-like silicon carbide particles in which tungsten boride is dissolved are dispersed. Particles of plate-like silicon carbide 3 in which tungsten boride is dissolved are uniformly dispersed in fine carbide matrix 4.

Further, Si, Cr, Ti, Hf, B, Z
A predetermined amount of the powder obtained by mechanical alloying is mixed with a 1: 3 molar ratio of a mixed powder of a carbide powder composed of at least one of r, Mo, and W and a metal Si powder, and a sintering aid and a forming binder are mixed. By sintering the compact at a high temperature, it is possible to disperse the plate-like silicon carbide particles in which tungsten boride is dissolved in a sintered body composed of fine carbide particles. Can also disperse silicide particles such as molybdenum silicide generated by the above chemical reaction.

[0018]

## STR1 ## Although MoC + 3Si ⇒ MoSi ₂ + SiC Figure 3 is a schematic illustration thereof, uniformly dispersed in the carbide matrix 4 of the particles of the plate-like silicon carbide 3 which tungsten boride is dissolved and silicide particles 5 and fine particles ing.

As a sintering aid for producing a carbide sintered body, B, C, boron carbide, an oxide of group II to VIII, a nitride of group II to VIII, or the like can be used. The compounding amount is 0.
It is about 5 to 20 mass%.

Regarding the high toughness ceramic of the present invention,
Sintering can be performed by pressureless sintering, gas pressure sintering, hot press sintering, hot isostatic press sintering, spark plasma sintering, microwave plasma sintering, etc. Various molding methods can be selected according to the shape and required characteristics, such as casting, rubber press molding, extrusion molding, and mold powder molding, and a ceramic having a complicated shape can be obtained.

With respect to the sintering temperature, time, pressure and atmosphere, conditions for densification are found and controlled depending on the composition. Further, the sintering temperature is preferably selected according to the type of the ceramic to be the matrix.

In the ceramic of the present invention, carbon, SiC, Si—C—O, Si—C—N—O, Si ₃
Whisker and / or long fiber composed of at least one of N ₄ , Si—Ti—C—O, Si—NO, and Al—O can be oriented and dispersed, and can be mixed with ordinary whisker mixing method or long fiber. It is possible by law.

FIG. 4 is a schematic view in which long fibers are oriented.
Particles of plate-like silicon carbide 3 in which tungsten boride 3 forms a solid solution are uniformly dispersed in carbide matrix 4 of fine particles and reinforced with long fibers 6.

The composite carbide ceramics of the present invention is suitable for cutting tools and sliding members because it can achieve unprecedented high strength and high toughness. It can be used for moving blades, stationary blades, combustors, shrouds, nuclear parts and the like for gas turbines. Next, the present invention will be specifically described based on examples.

[0025]

【Example】

[Examples 1 to 5] 50 g of a 1: 1 (molar ratio) mixed powder of 1 μm Si powder and 20 nm C powder, and 2 μm W
Of a 5: 1 (molar ratio) mixed powder of powder and 2 μm B powder
A mixed powder with 0 g was prepared. The powder was subjected to mechanical alloying treatment for 24 hours by a planetary ball mill using a tungsten container (inner diameter 100 mm × height 120 mm) and tungsten balls (diameter 5 mmφ).

The obtained powder was mainly β-silicon carbide having a broad X-ray diffraction peak of 1 μm or less.

Next, mechanical alloying powder was added to 0.5 μm β-silicon carbide powder so as to have a sintered body composition shown in Table 1, and boron carbide was added as a sintering aid in an amount of 2 mass%.
2 mass% of a binder (PVB) for press molding was mixed together with ethanol, dried, and used as a molding raw material. A molded body having a size of 50 mm square and a thickness of 10 mm was produced by a press molding method.

The obtained molded body was placed in an argon atmosphere for 21 days.
The sintering was performed at 00 ° C. for 1 hour. According to X-ray diffraction analysis and SEM analysis, the composition of the sintered body was composed of β-silicon carbide and tungsten boride (mainly WB, W ₂ B ₅ ), and the surface of tungsten boride was contained in a fine β-SiC matrix of several microns. Plate-like solid solution (size 40μm,
A sintered body having a thickness of 5 μm and β-SiC dispersed therein was obtained.

Table 1 shows the composition, bending strength, and fracture toughness of the obtained sintered body. The composition indicates the ratio of plate-like silicon carbide in which tungsten boride adheres to the surface and forms a solid solution and β-silicon carbide forming the matrix.

Further, as Comparative Example 1, 0.5 μm β-
2 mass% of boron carbide as a sintering aid in silicon carbide powder
Table 1 also shows the results of bending strength and fracture toughness of the sintered body obtained by similarly forming and sintering the added material.

The toughness value of the material of the present invention is 1.
It has improved by 5 to 2 times. Observation of the fracture surface revealed that the plate-like particles were protruding, and the cracks were bypassed to improve the toughness.

[0032]

[Table 1]

[Examples 6 to 12] As in Example 3,
Table 2 shows the results of investigations on combinations with other carbide ceramics instead of β-silicon carbide. The sintering temperature was in the range of 1700 ° C to 2500 ° C. The composition indicates the ratio of plate-like silicon carbide in which tungsten boride adheres to the surface and forms a solid solution and carbide particles forming the matrix.

From Table 2, the fracture toughness values of the carbides of Comparative Examples 2 and 3 are all about 3 MPa√m. On the other hand, it was found that the material of the present invention in which plate-like β-silicon carbide in which tungsten boride was dissolved was dispersed had better toughness than carbide ceramics alone.

[0035]

[Table 2]

Example 13 50% of a 1: 1 (molar ratio) mixed powder of 0.5 μm Si powder and 0.1 μm C powder was used.
g, 1 μm W powder and 0.5 μm B powder 3: 1
(Molar ratio) A mixed powder with 10 g of the mixed powder was prepared. The powder was placed in a tungsten container (inner diameter 100 mm x height 12
0 mm) and a tungsten alloy ball (diameter 5 mmφ) using a planetary ball mill for 24 hours of mechanical alloying.

The obtained powder was mainly β-silicon carbide having a broad X-ray diffraction peak of 1 μm or less.

Next, boron carbide was used as a sintering aid in 2mas.
s%, binder for press molding (PVB) 2 mass%
Was mixed with ethanol, dried and used as a molding raw material. A molded body having a size of 50 mm square and a thickness of 10 mm was produced by press molding. The obtained molded body in an argon atmosphere,
Sintering was performed at a temperature in the range of 1800 ° C. to 2300 ° C. for 1 hour. As a result, a plate shape (size: 30 to 200 μm, thickness: 3 to 10 μm) in which tungsten boride adheres and forms a solid solution on the surface
Of β-SiC three-dimensionally intertwined with a sintered body having a porosity of 40 to 1%.

Example 14-17 1: 1 (molar ratio) mixed powder of 1 μm Si powder and 20 nm C powder was prepared.
A mixed powder (60 g) of 10 g of a 1: 3 (molar ratio) mixed powder of g and 2 μm W powder and 2 μm B powder was prepared. The powder was placed in a silicon carbide container (inner diameter 100 mm × height 1).
Mechanical alloying treatment was performed for 24 hours by a planetary ball mill using tungsten balls (diameter: 5 mmφ) and tungsten balls (diameter: 5 mmφ).

The obtained powder was mainly β-silicon carbide of 1 μm or less having a broad X-ray diffraction peak.

Next, a 1: 1 (molar ratio) mixed powder of a 0.5 μm molybdenum carbide powder and a metal Si powder (140
g), a predetermined amount of the mechanically alloyed powder was mixed, and aluminum oxide was added as a sintering aid by 7 mass.
% And 2 mass% of a binder for press molding (PVB) were mixed with an organic solvent, dried, and used as a raw material for molding. A molded body having a size of 50 mm square and a thickness of 10 mm was produced by press molding.

The obtained molded body was sintered at 2050 ° C. for 2 hours in an argon atmosphere of 0.5 MPa. Table 3 shows the composition and characteristics of each of the obtained sintered bodies.

According to X-ray diffraction analysis and SEM analysis, the composition of the sintered body was composed of β-silicon carbide, tungsten boride (mainly WB, W ₂ B ₅ ), and molybdenum silicide, and was a fine β-SiC matrix of several microns. Tungsten boride adheres to the surface and forms a solid solution (size 40μm, thickness 5μ)
m) β-SiC was dispersed, and a sintered body in which nano-sized molybdenum silicide particles were further dispersed was obtained. By dispersing the nano-sized molybdenum silicide particles, the strength and toughness could be further improved.

[0044]

[Table 3]

Example 18 1 μm Si powder and 20 μm
50 g of a 1: 1 (molar ratio) mixed powder with nm C powder;
5: 1 (molar ratio) of 2 μm W powder and 2 μm B powder
A mixed powder (60 g) with 10 g of the mixed powder was prepared. The powder was placed in a tungsten container (inner diameter 100 mm x height 12
0 mm) and a tungsten alloy ball (5 mm in diameter) using a planetary ball mill for 24 hours of mechanical alloying.

Next, 0.3 μm α-silicon carbide powder (1
20 g), the above-mentioned mechanical alloying powder was added thereto, and a slurry obtained by mixing 1 mass% each of carbon and boron as a sintering aid and an aqueous solvent was poured into the voids of the three-dimensional carbon fiber preform wire molded product, and dried. The obtained compact was heated to 2000 ° C. by a hot isostatic press under a pressure of 100 kg / cm ² and held for 2 hours to prepare a sintered body.

The bending strength of the obtained sintered body from room temperature to 1500 ° C. (in vacuum) was 520 MPa, which was not observed to decrease with temperature. Further, the fracture toughness value is 15 MPa.
√m.

Similarly, SiC, Si—CO, Si—C
_{-O-N, Si 3 N 4} , Si-Ti-C-O, Si-N-
Sintering was similarly performed using the O, Al-O long fiber preform wire, and similar characteristics were obtained.

[Embodiment 19] 1500 ° C. rotating a turbine by combustion gas in a thermal power plant system
Class gas turbine test equipment, a combustor lining constituting the gas turbine, a transition piece for the combustor,
The member made of the ceramics of Example 3 was used for each of a bypass valve, a turbine blade, a turbine vane, a turbine disk, a spindle bolt, a turbine casing, a shroud, a diffuser cone, a turbine exhaust casing, and an exhaust duct.

As a result of a 1000-hour operation test using the above test equipment, no abnormality was found. By applying the ceramic member of the present invention, the amount of cooling air can be reduced, and the efficiency can be improved by 5% or more as compared with the conventional one using a metal-based member.

Similarly, the present invention is applied to a regenerative single-shaft gas turbine for cogeneration, a regenerative twin-shaft gas turbine for cogeneration, a regenerative two-shaft gas turbine for portable power generation, a gas turbine for aircraft, a gas turbine for automobiles, and the like. By providing the above ceramic material, it is possible to obtain a heat-resistant, oxidation-resistant and highly efficient device.

Example 20 A 1: 1 (molar ratio) mixed powder of 0.5 μm Si powder and 0.1 μm C powder was used.
g, 1 μm W powder and 0.2 μm B powder 3: 1
(Molar ratio) A mixed powder with 10 g of the mixed powder was prepared. The powder was placed in a tungsten container (inner diameter 100 mm x height 12
0 mm) and a planetary ball mill using tungsten balls (diameter 5 mm) were subjected to mechanical alloying treatment for 48 hours.

Next, boron carbide was used as a sintering aid for 2mas.
s%, binder for press molding (PVB) 2 mass%
Was mixed with ethanol, dried and used as a molding raw material. A compact having a size of 10 mm square and a thickness of 10 mm was produced by press molding. The obtained molded body was sintered in an argon atmosphere by a discharge plasma sintering method at 2100 ° C. for 1 hour. As a result, a plate-shaped (size of 30 to 200 μm, thickness of 3 to 10 μm) β-SiC in which tungsten boride was adhered and solid-dissolved on the surface, and a sintered body having a three-dimensionally entangled structure was obtained.

A throw-away tip for a cutting tool was cut out from the above sintered body and subjected to a cutting test. The cutting test
Using Ikegai NC lathe 25kW, cutting speed 500m / min,
The cut was made at 0.5 mm, the feed was 0.36 mm / rotation, and the cut material SUS304 (diameter 300 mm) was used.

The life was determined to be V _B = 0.2 mm, and it was confirmed that this embodiment was useful as a cutting tool material.

Example 21 Using the sintered body composition obtained in Example 1, a guide rail 7 for an actuator of a magnetic disk drive as shown in FIG. 5 was manufactured. In FIG. 5, reference numeral 8 denotes a bearing (made of SUS304), 9 denotes a coil, and 10 denotes a frame.

[0057] The roughness of the sliding surface and 0.1 [mu] m, the maximum speed of 1.4 m / sec, the magnetic head at a frequency 60Hz is reciprocated 10 ⁹ times. The roughness of the sliding surface after the test was 0.1 μm or less, and it was confirmed that there was no change from before the sliding.

The material of this example was found to be excellent in wear resistance and suitable for actuators.

The material of the present invention is a sealing material for various pumps,
It can be applied as various bearing materials, and its durability and reliability can be significantly improved.

[0060]

According to the present invention, there is obtained a carbide ceramic in which plate-like silicon carbide particles in which tungsten boride is dissolved are dispersed, and the composite ceramic is formed by plate-like silicon carbide particles in which tungsten boride is dissolved. Suppress crack growth,
The fracture toughness value can be improved. Thereby, it can be applied to a member used under severe conditions which could not be applied conventionally. For example, wear resistance, corrosion resistance, and heat resistance of cutting tools, sliding members, moving blade components for gas turbines, stationary blade components, combustor components, shroud components, nuclear power components, and the like can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic view of a plate-like silicon carbide in which tungsten boride is dissolved.

FIG. 2 is a schematic diagram of a carbide sintered body in which plate-like silicon carbide particles in which tungsten boride is dissolved are dispersed.

FIG. 3 is a schematic view of a plate-shaped silicon carbide particle in which tungsten boride is solid-dissolved and a carbide sintered body in which silicide particles are dispersed.

FIG. 4 is a schematic diagram of a long fiber-reinforced carbide sintered body in which plate-shaped silicon carbide particles in which tungsten boride is solid-dissolved are dispersed.

FIG. 5 is a schematic view of an actuator section of the magnetic disk drive.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Plate-shaped silicon carbide with solid solution of tungsten boride, 2 ... Tungsten boride, 3 ... Plate-shaped silicon carbide with solid solution of tungsten boride, 4 ... Carbide matrix, 5 ... Silicon particles,
6 ... long fiber, 7 ... guide rail, 8 ... bearing, 9 ...
Coil, 10 ... frame.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Motoyuki Miyata 7-1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Yuichi Sawai 7-chome, Omika-cho, Hitachi-shi, Ibaraki No. 1 Hitachi Co., Ltd. Hitachi Research Laboratory

Claims (18)

[Claims] 1. A composite ceramic comprising a ceramic sintered body containing plate-like silicon carbide particles in which tungsten boride is dissolved. 2. Si, Cr, Ti, Hf, B, Zr, M
In a carbide sintered body composed of at least one of o and W, 1 to 50 plate-like silicon carbide particles having a solid solution of tungsten boride are contained.
A composite ceramic characterized by containing vol%. 3. Si, Cr, Ti, Hf, B, Zr, M
1 to 50 v plate-like silicon carbide particles in which tungsten boride is dissolved in a carbide sintered body comprising at least one of o and W
ol%, and 1 to 20 vol% of molybdenum silicide particles. 4. Carbon, SiC, Si—CO, Si
—C—N—O, Si ₃ N ₄ , Si—Ti—C—O, Si—
The composite ceramic according to claim 1, 2 or 3, wherein whiskers and / or long fibers comprising at least one of NO, Al-O are dispersed in 2 to 50 vol%. 5. At least Si powder, C powder, B powder,
Mechanically alloying a mixed powder of W powder, mixing the sintering aid and a molding binder with the mechanically alloyed powder to form a molded body, and forming the compact in an inert gas or a reducing gas or in a vacuum. A step of heating at 1700 to 2500 ° C. for 1 to 600 minutes to produce a sintered body. 6. At least Si powder, C powder, B powder,
Mechanical alloying of mixed powder of W powder, S
The powder obtained by mechanically alloying is mixed with a carbide powder composed of at least one of i, Cr, Ti, Hf, B, Zr, Mo, and W in an amount of 1 to 50 vol% in terms of a sintered body. A molding binder is mixed and molded, and the molded body is mixed with an inert gas, a reducing gas, or a vacuum.
Heating the composite at 700 to 2500 ° C. for 1 to 600 minutes to produce a sintered body. 7. At least Si powder, C powder, B powder,
Mechanical alloying of mixed powder of W powder, S
i: Cr, Ti, Hf, B, Zr, Mo, W Carbide powder of at least one kind and metal Si powder 3: 1 to 1
The mechanically alloyed powder was mixed with a mixed powder of 1: 5 (molar ratio) in an amount of 1 to 50 vol% in terms of a sintered body, and a sintering aid and a forming binder were mixed with the mixed powder, followed by molding. A step of heating at 1700 to 2500 ° C. for 1 to 600 minutes in an inert gas, a reducing gas or vacuum to produce a sintered body. 8. The mechanical alloying step is performed using a tungsten container and a tungsten ball or a silicon carbide container and a tungsten ball.
Or a method for producing a composite ceramic according to 7. 9. The method according to claim 9, wherein the mechanically alloyed powder is β
-The method for producing a composite ceramic according to claim 5, 6 or 7, containing silicon carbide. 10. The method for sintering the green body is pressureless sintering,
8. The method for producing a composite ceramic according to claim 5, which is any one of gas pressure sintering, hot press sintering, hot isostatic press sintering, spark plasma sintering, and microwave plasma sintering. 11. The mixing molar ratio of the Si powder and the C powder is 1: 1 and the mixing molar ratio of the W powder and the B powder is 5: 1.
8. The method for producing a composite ceramic according to claim 5, wherein the ratio is 1: 5. 12. The sintering aid is B, C, boron carbide,
Beryllium oxide, scandium oxide, vanadium oxide,
Selected from iron oxide, selenium oxide, strontium oxide, chromium oxide, hafnium oxide, zirconium oxide, molybdenum oxide, tungsten oxide, yttrium oxide, niobium oxide, tantalum oxide, boron oxide, silicon oxide, aluminum oxide, titanium oxide, and rare earth oxide The method for producing a composite ceramic according to claim 5, 6 or 7, wherein at least one selected from the group consisting of 0.5 to 20 mass% is blended. 13. A cutting tool, wherein at least a cutting edge of the cutting tool is formed of a composite ceramic made of a ceramic sintered body containing plate-like silicon carbide particles in which tungsten boride is dissolved. 14. The cutting tool according to claim 1, wherein at least the cutting edge is S
Composite comprising 1 to 50 vol% of plate-like silicon carbide particles in which tungsten boride is dissolved in a carbide sintered body made of at least one of i, Cr, Ti, Hf, B, Zr, Mo, and W. A cutting tool characterized by being formed of ceramics. 15. The cutting tool according to claim 15, wherein at least the cutting edge is S
In a carbide sintered body composed of at least one of i, Cr, Ti, Hf, B, Zr, Mo, and W, 1 to 50 vol% of plate-like silicon carbide particles in which tungsten boride is dissolved, and molybdenum silicide particles are contained. A cutting tool comprising a composite ceramic containing 1 to 20 vol%. 16. A composite ceramic in which at least one sliding member of a sliding portion of a mechanical device in which two members slide with each other is a ceramic sintered body containing plate-like silicon carbide particles in which tungsten boride is dissolved. A sliding member characterized by being formed of: 17. At least one sliding member of a sliding portion of a mechanical device in which two members slide with respect to each other is formed of Si, Cr,
It is formed of a composite ceramic containing 1 to 50 vol% of plate-like silicon carbide particles in which tungsten boride is dissolved in a carbide sintered body made of at least one of Ti, Hf, B, Zr, Mo and W. A sliding member characterized by the following. 18. A sliding device according to claim 18, wherein at least one of the sliding portions of the mechanical device in which the two members slide with respect to each other is made of Si, Cr,
In a carbide sintered body composed of at least one of Ti, Hf, B, Zr, Mo, and W, 1 to 50 vol% of plate-like silicon carbide particles in which tungsten boride is dissolved, and 1 to 20 vol% of molybdenum silicide particles. A sliding member characterized by being formed of a composite ceramic contained therein.