JPH02160669A - Silicon nitride-silicon carbide multiple sintered compact and production thereof - Google Patents

Abstract

PURPOSE:To provide the title sintered compact of high hardness excellent in high-temperature mechanical strength, fracture toughness, thermal insulation, processability and wear resistance, having such structure that fine SiC dispersed within Si3N4 and on the boundary of Si3N4 grains. CONSTITUTION:A mixture of SiC<1mum in average grain size and noncrystalline Si3N4 powder is further mixed with, as sintering auxiliary, 0.1-20wt.% of MgO, Al2O3, Y2O3, AlN, CeO2, etc. The resultant mixed powder raw material is then press-molded followed by sintering through hot press or HIP process at 1500-3000 deg.C. During the sintering process, a liquid phase is formed due to the presence of the sintering auxiliary. and the SiC several-several hundreds nm in grain size is dispersed within the Si3N4 grains while the SiC<=0.5mum in average grain size is dispersed on the boundary of the Si3N4 grains. Thus the objective SiC-Si3N4 multiple sintered compact excellent in high-temperature mechanical strength, hardness and wear resistance can be obtained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a silicon nitride-silicon carbide composite sintered body and a method for manufacturing the same. A silicon carbide composite sintered body and its manufacturing method, which form a unique microstructure in which silicon carbide is dispersed within silicon nitride particles and at grain boundaries, and
The present invention relates to a composite sintered body that has excellent high-temperature strength, fracture toughness, and heat insulation properties, has a low elastic modulus and is excellent in workability, and has high hardness and excellent wear resistance.

[Prior art and its problems]

Silicon nitride and silicon carbide have recently attracted much attention as engineering ceramic materials for high-temperature structural materials. In particular, silicon nitride has excellent thermal shock resistance and fracture toughness, and silicon carbide has excellent oxidation resistance and high-temperature strength.

For this reason, silicon nitride and silicon carbide are being developed in fields that take advantage of their respective properties.

On the other hand, various attempts have been made to develop silicon nitride-silicon carbide composites in order to take advantage of the advantages of both.

Conventionally, methods for obtaining silicon nitride-silicon carbide composite ceramics include (1) silicon nitride (S13N4) powder and silicon carbide (S
iC) A method in which powder or silicon carbide whiskers are mechanically mixed and sintered under pressure such as normal pressure sintering or hot pressing or HIP.

(2) A molded body made of silicon carbide powder and silicon (SiC) powder is subjected to a nitriding reaction to generate silicon nitride, or a molded body made of silicon nitride powder and carbon is infiltrated with silicon to generate silicon carbide. how to.

(3) A method of producing a silicon nitride-silicon carbide composite by using an organosilicon polymer or an organosilicon polymer to which silicon powder is added as a raw material and molding it directly or after heat treatment and then heating it.

And so on. However, among these, (2), (3)
Although the method generally has the advantage of good dimensional accuracy and excellent moldability, the resulting sintered body tends to be porous and it is difficult to obtain a dense sintered body with high density. For this reason, the physical properties of the sintered body obtained are often inferior to those of a dense sintered body of silicon nitride or silicon carbide alone.For example, the strength of the sintered body is generally lower than that of a sintered body of silicon nitride or silicon carbide alone. low.

Therefore, in order to obtain a high-density and dense composite sintered body, the method (1) above is generally employed. This method can be roughly divided into a method in which silicon carbide whiskers are added to silicon nitride, and a method in which silicon carbide powder is added to silicon nitride.

A silicon nitride-silicon carbide composite sintered body in which silicon carbide whiskers are dispersed has improved fracture toughness compared to silicon nitride, but it is difficult to uniformly disperse silicon carbide whiskers, so the strength is generally low. Become. Furthermore, with this method, the thermal conductivity and elastic modulus of the silicon nitride-silicon carbide composite sintered body obtained are higher than those of silicon nitride, as can be predicted according to the law of compounding.

On the other hand, examples of silicon nitride-silicon carbide composite sintered bodies using silicon carbide powder include U and S.

P, 4.184.882. Or J, Am, Cer
am, Sac, 56.445 (1973).
) powder (maximum 40 Vo1%) to silicon nitride (Si3N)
s) It is disclosed that by adding it to powder, a molded body with improved thermal conductivity and high temperature strength compared to silicon nitride can be obtained.

According to this method, when the added silicon carbide powder has a large particle size, the fracture toughness value is higher than that of silicon nitride, but the strength is rather lower than that of silicon nitride.

On the other hand, when the particle size of the added silicon carbide is small, the room temperature strength is comparable to that of silicon nitride, but the fracture toughness value is lower than that of silicon nitride. Moreover, the high temperature strength is higher than that of silicon nitride in any case, and the effect is greater when the particle size is smaller.

In this method as well, the thermal conductivity is increased by the addition of silicon carbide powder, similar to the method of adding silicon carbide whiskers.

Further, JP-A No. 58-91070 discloses a composite sintered body having excellent high-temperature strength and thermal shock resistance using a composite powder of silicon nitride and silicon carbide obtained by a gas phase reaction. Furthermore, in JP-A-61-183107, a sintered body with better thermal conductivity than silicon nitride can be obtained by sintering a mixed powder obtained by hydrolyzing silicon alkoxide in which carbon powder is dispersed. It is shown. Furthermore, in Japanese Patent Application Laid-Open No. 62-65910, silica and carbon were mixed with N2 and Ar.

It has been stated that a sintered body with superior thermal conductivity and bending strength compared to silicon nitride can be obtained by using a mixed powder obtained by heating a TIE in a specific mixed air flow at a specific temperature range. There is.

In this way, the method of dispersing silicon carbide powder is easier to uniformly disperse silicon carbide than the method of dispersing whiskers, and the silicon nitride-silicon carbide composite sintered body obtained using silicon carbide powder is Compared to a sintered body made of silicon nitride alone, it has superior strength, especially high-temperature strength, and thermal conductivity.

The reason why the conventional silicon nitride-silicon carbide composite sintered body has excellent high-temperature strength is mainly because the silicon carbide particles in the sintered body exist at the grain boundaries of the silicon nitride particles. This is to suppress slippage, and it is thought that the reason why the thermal conductivity is higher than that of silicon nitride is that silicon carbide has a higher thermal conductivity than silicon nitride, so the thermal conductivity increases according to the law of compositeness.

However, the high-temperature strength of the silicon nitride-silicon carbide composite sintered body obtained in this way is still insufficient to meet the strength required for heat-resistant components such as gas turbines in recent years, and it also requires heat insulation properties. It was unsuitable for parts.

In view of these problems, the present inventors first uniformly dispersed silicon carbide with an average particle size of 1 μm or less in silicon nitride, and by forming the silicon nitride particles into columns, the room temperature strength and fracture toughness values were improved. In both cases, it was shown that a silicon nitride-silicon carbide composite sintered body superior to that of silicon nitride could be obtained (Japanese Patent Laid-Open No. 159256/1983). The present inventors further investigated the silicon nitride-silicon carbide composite sintered body.

The present invention has high room temperature/high temperature strength and fracture toughness that could not be achieved with conventional silicon nitride-silicon carbide composite sintered bodies, and also has low thermal conductivity, that is, excellent heat insulation properties, and low elastic modulus. An object of the present invention is to provide a silicon nitride-silicon carbide composite sintered body with excellent workability.

[Means for solving problems]

The present invention provides a silicon nitride-silicon carbide composite sintered body in which silicon carbide particles with an average particle size of 1 μm or less are dispersed at the grain boundaries, and silicon carbide particles with a size of several nanometers to several hundred nanometers are contained within the silicon nitride particles. A silicon nitride-silicon carbide composite sintered body consisting of a dispersed microstructure, in particular, the constituent silicon nitride rings and silicon carbide have an average particle size of submicron size and are uniformly dispersed, and have an average particle size of 1 μm or less. A silicon nitride-silicon carbide composite sintered body having a microstructure in which silicon carbide is uniformly dispersed at grain boundaries and silicon carbide particles ranging in size from several nanometers to several hundred nanometers are dispersed within silicon nitride particles. Regarding its manufacturing method.

The silicon nitride-silicon carbide composite sintered body of the present invention, which has such a microstructure, has high room temperature/high temperature strength, fracture toughness, and composite law not found in conventional silicon nitride-silicon carbide composite sintered bodies. It exhibits low thermal conductivity, that is, heat insulation, and low elastic modulus, which cannot be predicted from steel, and also exhibits high hardness and excellent wear resistance.

The reason why the silicon nitride-silicon carbide composite sintered body of the present invention exhibits unique physical properties not found in conventional composite sintered bodies is due to the uniqueness of the microstructure of the sintered body.

For example, silicon nitride obtained by the method of the present invention -
In a silicon carbide composite sintered body, when the proportion of silicon carbide is small, silicon nitride has a well-developed structure consisting of many columnar particles and equiaxed particles with a large aspect ratio of the columnar particles.

Furthermore, most of the silicon carbide exists inside the silicon nitride particles with a size of several nanometers to several hundred nanometers, and some of it exists at the grain boundaries with a submicron size. Because the columnar particles of silicon nitride are well developed, the fracture toughness value of the obtained sintered body is higher than that of silicon nitride, and as a result of the higher fracture toughness value, the strength is improved compared to that of silicon nitride. .

In addition, silicon carbide present in the particles causes distortion to the crystal structure of silicon nitride, resulting in a decrease in the elastic modulus of the silicon nitride-silicon carbide composite sintered body, which cannot be predicted from the compounding law. It is presumed that this scatters phonons, which serve as a medium for heat conduction, and lowers thermal conductivity.

When there is a large amount of silicon carbide, the development of columnar grains of silicon nitride is suppressed, and most of them become equiaxed grains with a smaller grain size, so that silicon carbide is present not only within the silicon nitride grains but also at the grain boundaries. Become. Therefore, although the fracture toughness value is lower than when there is less silicon carbide, the size of defects in the sintered body becomes smaller, and as a result, the strength is improved compared to that of silicon nitride. In addition to silicon carbide particles existing at grain boundaries suppressing the slippage of silicon nitride grain boundaries,
It is presumed that large internal stress is generated by silicon carbide particles existing at grain boundaries or within silicon nitride particles, resulting in improved high-temperature strength compared to silicon nitride. Further, as the amount of silicon carbide present at grain boundaries increases, thermal conductivity and elastic modulus tend to increase. Furthermore, as the amount of silicon carbide increases, the hardness also increases.

One of the methods for manufacturing the silicon nitride-silicon carbide composite sintered body of the present invention having a microstructure exhibiting such characteristics is to use a sintering aid that generates a liquid phase during the sintering process. An example of this is liquid phase sintering at a temperature of 1500 to 2300°C in the presence of fine silicon carbide having an average particle size of 0.5 μm or less.

Traditionally, the mechanism of liquid phase sintering of silicon nitride is
It is said that a liquid phase is generated by the sintering aid, and sintering progresses by (1) dissolution of silicon nitride into the liquid phase, (2) precipitation of β phase, and growth of zero grains.

In the present invention, fine silicon carbide particles present in the system contribute as nuclei when silicon nitride precipitates during the liquid phase sintering process, forming the microstructure observed in the sintered body of the present invention. It is presumed that this is the case. In the present invention, the silicon carbide present in the system has a smaller particle size than conventionally used silicon carbide, so the number of nuclei present is large even for the same volume %, and the silicon nitride produced in the sintered body is grainy. The number of columnar particles with a small diameter increases. Furthermore, since the grain size of silicon carbide is small, it is thought that sintering progresses as silicon carbide is incorporated into the grains of silicon nitride during the process of precipitation and grain growth of silicon nitride. When there is a large amount of silicon carbide m, the silicon carbide dispersed in the system becomes an obstacle when silicon nitride grains grow, so grain growth is suppressed and equiaxed silicon nitride grains are present. Become.

At first, silicon carbide is incorporated into the silicon nitride grains, but once it reaches a certain amount, it can no longer be incorporated into the silicon nitride particles and is dispersed to the grain boundaries, and the silicon carbide dispersed at the grain boundaries remains as it is. It is presumed that grain growth begins.

In the present invention, since the silicon carbide present in the system functions as described above, the fine structure of the silicon nitride-silicon carbide composite sintered body produced differs depending on the amount of silicon carbide, resulting in a unique structure as in the present invention. It is presumed that it forms a fine structure.

In order to obtain the sintered body of the present invention, silicon carbide must be present with an average particle size of 0.5 μm or less during sintering. In the present invention, the silicon carbide powder used as a raw material may have an average particle size of 0.5 μm or less, or an amorphous powder that produces silicon carbide particles of 0.5 μm or less during the sintering process. Examples of such raw material fine powder include fine silicon carbide powder obtained by a synthesis method such as a gas phase reaction method using thermal plasma or laser.

Furthermore, conventionally used crystalline or amorphous powders can be used as silicon nitride. Further examples include amorphous composite powders made of silicon, carbon, nitrogen, and oxygen that were previously reported by the present applicant.

Such amorphous composite fine powder is already intimately mixed with silicon carbide and silicon nitride at the raw material stage so that silicon carbide and silicon nitride are mixed well, and silicon carbide can be uniformly dispersed. It is suitable for obtaining such a composite sintered body. The above-mentioned silicon, carbon, the above-mentioned amorphous composite powder consisting of silicon, carbon, nitrogen and oxygen are, for example,
200812, JP 60-200813, JP 60-221311, JP 60-23
It can be obtained by the method shown in JP-A No. 5707° and JP-A-61-117108.

Specifically, an amorphous fine powder is obtained by vaporizing an organosilicon compound and thoroughly mixing it with a non-oxidizing gas containing ammonia, and then introducing the mixture into a reactor heated to a predetermined temperature and causing a reaction.

Examples of organosilicon compounds used in the synthesis of the above-mentioned amorphous composite powder consisting of silicon, carbon, nitrogen, and oxygen include [(C1l3)-3l)-NH.

[(Ct13)-3iN11),,[1ISi(CI!
3) 2] Yo NH.

((C113) ass]7 MCll5, [(C1l
a) A silazane compound such as zsi-MCll3)) or a 6-membered cyclic tris(N-methylamino)triN-methyl-cyclotris having the following chemical formula and having an N-methylamino group as a substituent on silicon. Silazane, or CtlaSi (NIICIIs),
(Clls) 2si (NHCfls) *, (CHa
)zsi [:N(C)13)2], (C)Is)sSiCN, (CHs)2s
i(CN)i, (Cs)Is)asicN.

(C6Hs) -S i (CN) 2,ll5S 1
CN1 (CII=CII) CHsS i (CN)
*, cyanosilicon compounds such as (CHs)nsi.

[(Clla) 3Sil, C(CHa)-8s]J
CIIs, [(C1ls) JSi %C1,CH3 (CHs)SiCj! , (CHs)-SiC1 and the like are exemplified.

As the sintering aid that generates a liquid phase in the sintering process used in the present invention, any of those conventionally used as sintering aids for silicon nitride and silicon carbide can be used. As such a sintering aid, for example, MgO
, A120a, YsOs, AIN.

Other examples include CeO*, La20a, etc., and these can be used alone or in combination.

The amount of these sintering aids used is usually in the range of 0.1 to 20% by weight. The method of mixing the silicon nitride, silicon carbide mixed powder, or the above-mentioned amorphous composite powder with the sintering aid may be any conventionally used dry or wet method.

As the sintering method in the present invention, conventional methods such as ordinary pressureless sintering, hot pressing, gas pressure sintering, or HIP can be applied as they are. During this sintering, it is necessary to sufficiently generate a liquid phase; for example, by holding the temperature for a while above the temperature at which the liquid phase is generated so that the liquid phase is well distributed between the particles before starting the sintering process. As a result, the fine structure of the present invention is uniformly generated in the sintered body.

Furthermore, by performing this maintenance, it is possible to control the amount of silicon carbide present within the grains and at the grain boundaries.
The appropriate sintering temperature is usually 1500 to 2300°C, preferably 1600 to 18°C, at which silicon nitride decomposition does not occur.
Performed at 50°C.

For example, in the typical hot press method, 1600 to 185
0℃, 200~400 kg/cm2.0.5~10h
Sintered under rs conditions. By such sintering, the sintered body finally obtained is mostly composed of silicon nitride mainly in the β phase and silicon carbide mainly in the β phase.

On the other hand, when using HIP or gas pressure sintering, the sintering temperature can be increased because the decomposition temperature of silicon nitride can be increased. By such a sintering method, it is also possible to change the silicon carbide in the silicon nitride-silicon carbide composite sintered body to a phase rich in α phase. Also, depending on the sintering temperature, the sintering aid may react with silicon nitride or silicon carbide to form a crystalline phase, which strengthens the grain boundary phase and is particularly desirable for high-temperature strength. This is not a particular problem since it gives results.

The composite sintered body of the present invention obtained by such a method has a unique microstructure that is not observed in conventional composite sintered bodies, as seen in a TEM (transmission electron microscope) photograph. It is a solid body with high strength and fracture toughness at room and high temperatures, and exhibits values such as thermal conductivity and elastic modulus that cannot be predicted from conventional compound rules. It also has high hardness and excellent wear resistance.

Figure 1 shows the microstructure of the composite sintered body according to the present invention.
M (transmission electron microscope) photograph.

In the photograph of FIG. 1, the whitish parts are silicon nitride particles, and the dispersion of the black silicon carbide particles can be seen within these particles.

Dispersion of silicon carbide particles is also observed at the grain boundaries of silicon nitride particles. In FIG. 1, A shows typical silicon carbide particles present within silicon nitride particles, and B shows typical silicon carbide particles dispersed at grain boundaries.

FIG. 2 is an enlarged photograph showing the presence of silicon carbide particles within silicon nitride particles.

FIG. 3 shows the thermal conductivity of the composite sintered body of the present invention in comparison with that of a silicon nitride-silicon carbide composite sintered body obtained by a conventional method. The thermal conductivity of conventional composite sintered bodies is
It increases monotonically as the amount of silicon carbide increases according to the compound law. On the other hand, the sintered composite according to the present invention shows a lower value than silicon nitride when the amount of silicon carbide is small, and shows a tendency to increase as the amount of silicon carbide increases. This is a phenomenon that cannot be predicted from conventional silicon carbide-silicon nitride composite sintered bodies.

FIG. 4 shows a comparison of the elastic modulus of the composite sintered body between the sintered body according to the present invention and the conventional composite sintered body. The composite sintered body according to the present invention exhibits a lower elastic modulus than conventional composite sintered bodies.

Next, examples of the present invention will be shown together with comparative examples. The examples shown below are merely examples of the present invention, and are not intended to be limiting unless they go beyond the gist of the present invention.

In addition, in the present invention, the room temperature strength test is 3x4x>36
Using a test piece with a size of mm, the span is 3 with 3-point bending strength
The crosshead speed was 0.5 mm/min. In addition, the high temperature strength test used a test piece with a size of 2X3X>24mm, and a span of 20mm at 3-point bending strength.
The crosshead speed was 0.5 m+n/min. The bulk density of the sintered body was measured by the Archimedes method, and the hardness was measured by Vickers hardness using a microhardness meter (19.6N load, held for 20 seconds). In addition, the thermal conductivity was calculated by determining specific heat and thermal diffusivity using the laser flash method, and combining them with the density value.

Furthermore, the elastic modulus was determined by the resonance method.

Examples 1 to 4 A vertical resistance heating furnace equipped with an alumina reaction tube of 90 mm (diameter) xiaoo mm (length) was
The temperature was maintained at 050°C. On the other hand, the reaction raw material hexamethyldisilazine:/[:Si(Clls)-)NH was introduced into the evaporator at a feed rate of about 500 g/hr, and after complete vaporization, the mixture ratio shown in Table 1 was The mixture was thoroughly mixed with the Ni1-/Ar mixed gas and introduced into the reactor for reaction. Fill an alumina container with 200 g of the generated powder, and
0℃, 4hrs.

Si, N, C for forming a sintered body by heat treatment under N2 gas flow
The obtained powder was an amorphous powder according to X-ray diffraction, and was found to be spherical particles of 0.5 μm or less when observed by SEM photography.

The obtained raw material powder contains Y2L 6 wt%, Aji! 2
After adding 032 wt% and wet mixing in ethanol and dry explosion, it was filled into a graphite die with a diameter of 50 mm and heated at 1800°C for 2 hours at a pressure of 350 kg/cm2 in nitrogen gas.
Hot press sintering of s was performed. The obtained sintered bodies were cut and ground with diamond grindstones of $100 and $600, and then polished with diamond paste of 3 μm and 1 μm, and the physical properties were measured. The results are shown in Table 1 (next page).

Table-1 (Hereafter blank) In the table, (book 1) other components are Si and impurities Fe, A
j! .

Ca, etc. (Book 2) All carbon in the raw material is SiC
Calculated on the assumption that it was converted to

Comparative Example 1 Commercially available high-purity crystal army 5isN4 powder (90% α phase, average particle size 0.(1+um, impurities Fe, AJ, Ca,
<50ppmO<1wt%) and Y*Os 6wt%,
Aj! Add Js 2wt% and 5i with ethanol.
After 5 hours of mixed mixing using an aNn ball, hot press sintering was performed under the same conditions as in Example 1 to obtain a sintered body. As a result of measuring the physical properties of the obtained sintered body, the density was 3.26 g/
c, Vickers hardness 14.5 GPa, 3-point bending strength approximately 87 kg/mm at room temperature, 60 kg at 21200°C
'/mm', fracture toughness value is 5.2 MN/m'', thermal conductivity is 0.087 Cal/Cm-8・℃, elastic modulus is 3
Ivy at 056Pa.

Example 5 Amorphous silicon nitride (Si3N4) powder (average particle size 0.3 μm, impurity P
e, ACCa < 50ppm C=0.9wt%
, O < 1 wt%), β-3i with an average particle size of 0.2 μm
20 wt% of C powder and 56 wt% of Y2O, Aj! ,0
．． After adding 2 wt % and mixing with ethanol in a 5ia114 pole for 5 hours, hot press sintering was performed under the same conditions as in Examples 1 to 4 to obtain a sintered body. As a result of measuring the physical properties of the obtained composite sintered body, the density was 3.26 g/c,
Vickers hardness: 16°8 GPa, 3-point bending strength: 110 kg/mm' at room temperature, 76 kg/m at 1200°C
In', the fracture toughness value is 5.81N/m, the thermal conductivity is 0.060Ca1/CIo・8・℃, and the elastic modulus is 310.
It was GPa.

Comparative Example 2.3 Si3N similar to that used in Comparative Example 1, β-phase silicon carbide (average particle size 0.7 μm1 impurity PeO, 02 wt.
%, Af 0010 wt%, Ca O, 04wt
%, 00.04wt%) in the ratio shown in Table 2, and Y2ks 6 wt%, Aj! 20.2% II
After adding t% and mixing with ethanol for 5 hours, hot press sintering was performed under the same conditions as in the example to obtain a sintered body. The physical properties are shown in Table-2.

(The following is a blank space) Table 2 [Effects of the invention] As described above, the composite sintered body according to the present invention has a unique microstructure not seen in conventional silicon nitride-silicon carbide composite sintered bodies, and has a unique microstructure that can be used both at room temperature and at high temperatures. It has high strength, excellent fracture toughness, and high hardness. Furthermore, the thermal conductivity and elastic modulus show low values that cannot be predicted from the compound law.

Therefore, the silicon nitride-silicon carbide composite sintered body according to the present invention exhibits characteristics such as particularly excellent strength at high temperatures, low thermal conductivity and low elastic modulus, and has excellent workability, and is used in gas turbines, turbochargers, etc. It can be used as a suitable material for high-temperature, high-strength members and members that require heat insulation, and because it has high hardness and excellent wear resistance, it can be used as a suitable material for sliding members and members that require wear resistance.

[Brief explanation of the drawing]

The right side of FIG. 1 and FIG. 2 are TEM (transmission electron microscope) photographs showing the fine structure of the composite sintered body according to the present invention. In the photograph of FIG. 1, the whitish parts are silicon nitride particles, and the dark parts within these are silicon carbide particles. In FIG. 1, A represents typical silicon carbide particles present within silicon nitride particles, and B represents typical silicon carbide particles dispersed at grain boundaries. FIG. 2 is an enlarged photograph showing the presence of silicon carbide particles within silicon nitride particles. FIG. 3 is a graph showing the thermal conductivity of a composite sintered body of the present invention and a silicon nitride-silicon carbide composite sintered body obtained by a conventional method. FIG. 4 is a graph showing the elastic modulus of the sintered body according to the present invention and the conventional silicon nitride-silicon carbide composite sintered body. Patent applicant Mitsubishi Gas Chemical Co., Ltd. agent (9070) Patent attorney Sadafumi Kobori iC content (voH) C content (vol$)

Claims (3)

[Claims] (1) A silicon nitride-silicon carbide composite sintered body in which silicon carbide with an average grain size of 1 μm or less is dispersed in the grain boundaries, and fine particles of silicon carbide with a size of several nanometers to several hundred nanometers are silicon nitride. A silicon nitride-silicon carbide composite sintered body consisting of a fine structure dispersed within the particles. (2) In the presence of a sintering aid that generates a liquid phase during the sintering process, the average particle size is 0.5μ at a temperature of 1500 to 2300℃.
1. A method for producing a silicon nitride-silicon carbide composite sintered body, which comprises carrying out liquid phase sintering in the presence of microscopic silicon carbide. (3) As a raw material powder, the average particle size is 0 in liquid phase sintering system.
．． 3. The method according to claim 2, wherein an amorphous silicon nitride-silicon carbide composite powder or a silicon nitride-silicon carbide mixed powder is used which produces fine silicon carbide of 5 μm or less.