JPH05279130A - Silicon carbide-silicon nitride composite material and its production - Google Patents

Abstract

PURPOSE:To obtain the subject dense sintered compact little in grain boundary phase, excellent in high-temperature strength, hardness and toughness by forming a mixed powder comprising alpha-SIALON, silicon nitride powder and silicon carbide powder followed by sintering in a nitrogen atmosphere. CONSTITUTION:A powder mixture comprising (A) 30-89.5vol.% of alpha-SIALON powder <=2mum in particle diameter, (B) 10-69.5vol.% of silicon nitride powder >=90% in alpha-rate and <=1mum in mean particle diameter, and (C) 0.5-30vol.% of silicon carbide powder <=0.05mum in particle diameter is formed by one of various means, and the resulting form is sintered in a nitrogen atmosphere under 0.1-10atm at 1600-1900 deg.C, thus giving the objective sintered compact >=95% in relative density, having the above advantages.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon carbide-silicon nitride based composite material which is dense, has few grain boundary phases and is excellent in high temperature strength, hardness and toughness, and a method for producing the same.

[0002]

2. Description of the Related Art Silicon nitride ceramics are excellent in wear resistance and high temperature characteristics and are attracting attention as various automobile materials. For the purpose of further improving high temperature strength, hardness, toughness, etc. Studies on the compounding of carbonaceous materials with silicon carbide are underway.

Since complexing with a silicon carbide material is difficult to sinter, a pressure sintering method such as hot pressing, a gas pressure sintering method for increasing the sintering temperature, and a large amount of sintering are used for the sintering. A sintering method or the like in which a sintering aid is added is adopted.

However, it is difficult to sinter a complex-shaped product by a pressure sintering method such as hot pressing, and there is a problem in productivity and cost. Further, the gas-pressure sintering method has a problem in that a complex-shaped product is difficult to sinter. Sintering is possible, but it still has problems in terms of productivity and cost.

Further, in the sintering method under normal pressure by adding a large amount of sintering aid, the grain boundary phase of the obtained sintered body is thick and the high temperature strength and the hardness are largely lowered. Therefore, the effect of adding silicon carbide is obtained. There is a problem that is low.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and is obtained by sintering at 0.1 to 10 atm, which is dense and has few grain boundary phases.
An object of the present invention is to provide a silicon carbide-silicon nitride based composite material excellent in high temperature strength, hardness and toughness and a method for producing the same.

The inventor of the present invention uses a specific α-sialon powder, a silicon nitride powder and a silicon carbide powder having a specific particle size in specific ratios to obtain a dense, low grain boundary phase, high temperature strength, It has been found that a silicon carbide-silicon nitride based composite material having excellent hardness and toughness can be sintered under 0.1 to 10 atmospheres.

[0008]

The silicon carbide-silicon nitride matrix composite material of the present invention has the general formula ((M _X (Si, Al)
Α-sialon powder 30 to 89 represented by ₁₂ (O, N) ₁₆ (wherein M represents a rare earth element other than La or Ce, Mg or Ca, and x represents 0.1 to 1.0) 0.5 volume%, 10 to 69.5 volume% of silicon nitride powder, and 0.5 to 30 volume% of silicon carbide powder having a particle diameter of 0.05 μm or less are molded, and then nitrogen of 0.1 to 10 atm is used. The means is that it is sintered at 1600 to 1900 ° C. in the atmosphere.

Further, the method for producing a silicon carbide-silicon nitride based composite material of the present invention has a general formula ((M _X (Si, Al)
Α-sialon powder 30 to 89 represented by ₁₂ (O, N) ₁₆ (wherein M represents a rare earth element other than La or Ce, Mg or Ca, and x represents 0.1 to 1.0) 0.5% by volume, 10-69.5% by volume of silicon nitride powder and 0.5-30% by volume of silicon carbide powder having a particle diameter of 0.05 μm or less are mixed, and the resulting mixed powder is molded with 0.1% by volume. Sintering is performed at 1600 to 1900 ° C in a nitrogen atmosphere of 10 atm.

The ratio of the α-sialon powder is 30 to 8
9.5% by volume is preferred. If this ratio is less than 30% by volume, a dense sintered body cannot be obtained, and if it exceeds 89.5% by volume, the toughness and high temperature strength decrease.

The particle size of α-sialon is preferably 2 μm or less.

The ratio of the silicon nitride powder is 10 to 69.5.
Volume% is preferred. If this ratio is less than 10% by volume, the toughness and high temperature strength are reduced, and if it exceeds 69.5% by volume, a dense sintered body cannot be obtained.

The silicon nitride powder preferably has an α ratio of 90% or more and an average particle size of 1 μm or less.

The proportion of the silicon carbide powder is preferably 0.5 to 30% by volume. If this ratio is less than 0.5% by volume, the effect of adding silicon carbide is not sufficiently exhibited, and if it exceeds 30% by volume, a sufficiently dense sintered body cannot be obtained.

The particle size of the silicon carbide powder is 0.05 μm.
m or less is preferable. If the particle size exceeds 0.05 μm, a dense sintered body cannot be obtained.

In the present invention, α-sialon powder, silicon nitride powder and silicon carbide powder in the respective proportions described above are mixed, and the resulting mixed powder is molded by various molding methods, and then 0.1 to 0.1
Sinter in a nitrogen atmosphere of 10 atm.

At this time, the sintering temperature is preferably 1600 to 1900 ° C, particularly preferably 1650 to 1800 ° C. 16
If it is less than 00 ° C, it is not sufficiently densified, and if it exceeds 1900 ° C, the α-sialon and the silicon nitride material are decomposed.

[0018]

In the present invention, α represented by the above general formula
-Sialon powder, silicon nitride powder and particle size is 0.05μ
By using silicon carbide powder of m or less in each of the above proportions, it is possible to sinter under 0.1 to 10 atmospheres, a relative density of 95% or more, a dense, low grain boundary phase, high temperature A silicon carbide-silicon nitride based composite material having excellent strength, hardness and toughness is obtained.

The present invention will be described in detail below with reference to examples.

[0020]

Example: α-sialon powder (Y _0.5 Si _9.75 Al _2.25
O _0.75 N _15.25 ) (average particle size 2.0 μm), α-silicon nitride powder (average particle size 0.5 μm) and silicon carbide powder synthesized by the high frequency plasma CVD method (particle size 0.01 μm)
m) are mixed, and these are mixed in a ball mill with methanol, followed by drying, crushing, and molding (mold molding + CI
P (cold isotropic press) to obtain a molded product (45 × 35 × 10 mm) having the composition shown in Table 1.

The obtained molded product was heated at 1650 to 1850 ° C.
For 4 hours in a nitrogen atmosphere at 1 atm.

The obtained sintered body was subjected to JIS R-1601.
After processing into a 40 × 3 × 4 mm test piece according to the above, the density, hardness, fracture toughness (IN method) and 4-point bending strength (room temperature, 1300 ° C.) of this test piece were measured, and the results were measured. It shows in Table 1.

On the other hand, for comparison, when silicon nitride powder is not used (Comparative Example 1), silicon carbide powder is not used (Comparative Example 2), and neither silicon nitride powder nor silicon carbide powder is used (Comparative Example). 3) and average particle size 0.3μ
Table 1 also shows the characteristics of the sintered body obtained by mixing and sintering in the same manner as described above when using silicon carbide powder of m (Comparative Example 4).

[0024]

[Table 1]

The results shown in Table 1 show that the silicon carbide-silicon nitride based composite material of the present invention is superior in hardness, toughness and high temperature strength as compared with the case of the comparative example.

[0026]

According to the present invention, the α-sialon powder represented by the above general formula, the silicon nitride powder and the particle size of 0.0.
Using silicon carbide powder of 5 μm or less in a specific ratio,
By sintering in a nitrogen atmosphere at 0.1 to 10 atm, a silicon carbide-silicon nitride matrix composite having a relative density of 95% or more, being dense, having few grain boundary phases, and having excellent high temperature strength, hardness and toughness. A material and a manufacturing method thereof can be provided.

Claims (2)

[Claims] 1. The general formula ((M _X (Si, Al) ₁₂ (O,
N) ₁₆ (wherein M represents a rare earth element other than La or Ce, Mg or Ca, and x represents 0.1 to 1.0) 30 to 89.5% by volume of α-sialon powder , Silicon nitride powder 10 to 69.5% by volume and particle size 0.05 μ
After molding a mixed powder of 0.5 to 30% by volume of silicon carbide powder of m or less, 16 in a nitrogen atmosphere of 0.1 to 10 atm.
A silicon carbide-silicon nitride based composite material, characterized by being sintered at 00 to 1900 ° C. 2. The general formula ((M _X (Si, Al) ₁₂ (O,
N) ₁₆ (wherein M represents a rare earth element other than La or Ce, Mg or Ca, and x represents 0.1 to 1.0) 30 to 89.5% by volume of α-sialon powder , Silicon nitride powder 10 to 69.5% by volume and particle size 0.05 μ
characterized in that 0.5 to 30% by volume of silicon carbide powder of m or less is mixed, the obtained mixed powder is molded, and then sintered at 1600 to 1900 ° C. in a nitrogen atmosphere of 0.1 to 10 atm. A method for producing a silicon carbide-silicon nitride based composite material.