JPH0627038B2 - Ceramics sintered body and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a ceramic sintered body containing sialon as a main component and having an improved toughness value.

(Prior Art) A sialon-based sintered body containing Si-Al-ON as a main constituent element
It has a small coefficient of thermal expansion and is excellent in heat resistance, oxidation resistance, corrosion resistance, etc., and it has been attempted to be used as a structural material together with a Si ₃ N ₄ system sintered body or a SiC system sintered body.

Compared with the Si ₃ N ₄ system sintered body, such a sialon system sintered body has a small strength decrease in a high temperature range and is excellent in oxidation resistance, but on the other hand, there is a defect that the toughness is not sufficient. Therefore, to use it as a structural material,
It was inferior in reliability.

Therefore, it has been attempted to disperse particles that do not form a solid solution with sialon, for example, particles of SiC, in a sialon-based sintered body, and to improve the toughness value by the combined effect of the dispersed particles.

(Problems to be Solved by the Invention) However, as described above, in the sialon-based sintered body,
If dissimilar particles such as SiC are added to the powder satisfying the sialon composition in order to disperse particles such as SiC, the sinterability is significantly lowered.

Therefore, in order to densify and sinter under non-pressurized sintering conditions, it is possible to add only 5 parts by weight of SiC or the like as dispersed particles to 100 parts by weight of sialon powder. The effect of improving the toughness was not obtained.

On the other hand, by using the hot pressing method, it is possible to add up to about 50 parts by weight of SiC, etc. to 100 parts by weight of sialon powder, but the hot pressing method limits the shape to simple shapes and High cost, etc.
There is a problem that it is not suitable for mass production and that mechanical strength such as fracture toughness value is not sufficient. The same applies to HIP and the like.

Therefore, it is strongly desired to obtain a sialon-based sintered body having an excellent fracture toughness value by non-pressure sintering suitable for mass production, which has a high degree of freedom in the shape of the obtained sintered body and also has a low manufacturing cost. ing.

The present invention has been made to address such a problem, and uses sialon as a mother phase, which is dense and has an excellent toughness value and which can be obtained by pressureless sintering suitable for mass production. It is an object of the present invention to provide a ceramics sintered body and a method for manufacturing the same.

[Structure of the Invention] (Means and Actions for Solving the Problem) That is, the ceramic sintered body of the present invention has a ceramic sintered body whose main constituent phase substantially satisfies the sialon composition as a mother phase. 1 to 100 parts by weight of the mother phase
It is characterized in that hafnium oxide in the range of 60 parts by weight and silicon carbide in the range of 5 to 30 parts by weight are dispersedly contained. Further, the ceramic sintered body of the present invention comprises silicon nitride containing aluminum oxide in the range of 2.5 to 20% by weight, hafnium oxide in the range of 1 to 60 parts by weight, and 5 to 5 parts by weight based on 100 parts by weight of the silicon nitride. It is characterized by being formed and sintered from a mixture with 30 parts by weight of silicon carbide.

In addition, the method for producing a ceramics sintered body of the present invention comprises a silicon nitride powder containing aluminum oxide powder in a range of 2.5 to 20% by weight, and a range of 1 to 60 parts by weight with respect to 100 parts by weight of the silicon nitride powder. Hafnium oxide powder and
Mixing with a silicon carbide powder in the range of 30 parts by weight,
A step of shaping the mixed powder into a desired shape and sintering the obtained compact in a non-pressurized atmosphere.

The mother phase of the ceramics sintered body of the present invention may be one in which the main constituent phase satisfies the sialon composition, and does not necessarily have to be all sialon. That is, if 90% by weight or more of the matrix phase is sialon, the effect of the present invention can be obtained, and thus a grain boundary phase such as a glass phase may be included. Therefore, the raw material powder for obtaining the mother phase does not necessarily have to strictly satisfy the sialon composition.

It should be noted that the sialon has a β-sialon composition and an α-sialon composition, but the mother phase of the ceramic sintered body of the present invention is substantially a β-sialon. However,
It is also possible to use α-sialon.

Further, as described above, the ceramic sintered body of the present invention has hafnium oxide and silicon carbide dispersedly contained in the matrix phase. Since these hafnium oxide and silicon carbide do not form a solid solution in the crystal grains of sialon, they exist in the form of particles in the matrix structure and constitute a dispersed phase.

The hafnium oxide has a function as a sintering aid for the ceramic powder containing silicon carbide and substantially satisfying the sialon composition, and contributes to the improvement of the mechanical strength of the sintered body as dispersed particles after sintering. To do. That is, even in a system containing silicon carbide, the presence of hafnium oxide facilitates densification and sintering, and a large amount of silicon carbide can be added. The amount of hafnium oxide added is in the range of 1 to 60 parts by weight, preferably 5 to 50 parts by weight, and more preferably 100 parts by weight of the above mother phase.
The range is 10 to 30 parts by weight. If the amount of hafnium oxide added is less than 1 part by weight, sufficient densification cannot be achieved,
If it exceeds 60 parts by weight, on the contrary, the sinterability is impaired and the specific gravity is increased.

Silicon carbide is a component for improving the toughness of the mother phase that substantially satisfies the above sialon composition, and when used in combination with the above hafnium oxide, it is added in an amount of 5 to 30 parts with respect to 100 parts by weight of the mother phase.
It is possible to add as much as a weight part. The toughness improving effect of silicon carbide becomes remarkable from about 5 parts by weight,
If it exceeds 30 parts by weight, it will be difficult to achieve sufficient densification even when used in combination with hafnium oxide.

The ceramic sintered body having sialon as a mother phase of the present invention is manufactured, for example, as follows.

First, about 2.5 to 20% by weight of Al ₂ O ₃ powder is added to Si ₃ N ₄ powder to prepare a matrix powder that approximately satisfies the β-sialon composition. Al ₂ O ₃ forms a solid solution in Si ₃ N ₄ to form sialon, but if the addition amount exceeds 20% by weight, the strength decreases and the secondary formation such as grain boundary layer occurs. The amount of the two phases increases, and if it is less than 2.5% by weight, it becomes difficult to densify. The optimum amount of Al ₂ O ₃ blended is 10% by weight.

Here, the powder for the mother phase is not limited to the above-mentioned powder, but Si ₃ N
_Although it is possible to use only _4- Al ₂ O ₃ -AlN type, Si ₃ N ₄ -AlN-SiO ₂ type, and commercially available synthetic β-sialon powder, the above Si ₃ N ₄ -Al ₂ O _{3 is used.} According to the system, since the effect of refining the crystal grains can be obtained, the effect of improving the characteristics is higher than that of the synthetic β-sialon powder and the mixed powder satisfying the usual β-sialon composition. Further, since the β-sialon phase is formed only by Al ₂ O ₃ , it is possible to use water as the dispersion medium.

Then, a predetermined amount of HfO ₂ and SiC are added to the above-mentioned matrix powder, and they are sufficiently mixed to prepare a raw material powder for the ceramic sintered body of the present invention.

Here, the starting material of HfO ₂ has an average particle size of 2 μm.
Hereafter, a fine powder of 1 μm or less is preferable. Further, as a starting material of SiC, a particle-shaped material or a fiber-shaped material such as whiskers can be used.
However, when using particle-shaped SiC, if the particles are too large, defects may occur and the mechanical strength may decrease, so the average particle size is 50 μm or less and the maximum particle size is 100 μm.
It is preferable to use the following:

Next, the raw material powder of the ceramics sintered body is formed into a desired shape by a known forming method such as a press forming method. Then, the molded body in an unpressurized atmosphere of an inert gas,
The ceramic sintered body of the present invention can be obtained by sintering at a temperature of about 1700 ° C to 1900 ° C.

The ceramic sintered body of the present invention can be densified even by the above-mentioned non-pressure sintering, and the fracture toughness value can be improved. However, other firing methods such as atmosphere pressure sintering,
It does not prevent the application of the hopless method, the hot isostatic pressing method (HIP) and the like.

(Examples) Hereinafter, the present invention will be described with reference to Examples.

Examples 1 to 12 First, Si ₃ N ₄ powder having an average particle size of 0.7 μm and an average particle size of 0.9
A plurality of powders for the mother phase were prepared by using Al ₂ O ₃ powder of μm and each compounding ratio shown in Table 1.

Next, with respect to 100 parts by weight of each matrix powder, HfO ₂ powder with an average particle size of 0.9 μm and SiC powder with an average particle size of 0.5 μm or SiC whiskers with an aspect ratio of 1:20 are shown in Table 1. Each was added in a ratio (parts by weight), and these were mixed in a ball mill for 48 hours with ethanol as a dispersion medium and then dried to obtain raw material powders for ceramics sintered bodies.

Next, add about 5 parts by weight of the binder to 100 parts by weight of the raw material powder for each of the above-mentioned sintered compacts, and apply a molding pressure of about 1000 kg / cm ^{2 to} a length of 50 mm
Plate-shaped compacts each having a width of 50 mm and a thickness of 5 mm were produced.
After that, degreasing each of these compacts in a nitrogen gas atmosphere, and then at 1850 ° C. in a nitrogen gas atmosphere at normal pressure.
Sintering was performed for 2 hours to prepare a ceramic sintered body having sialon as a mother phase.

The sintering density and the fracture toughness value K _IC by the microindentation method of each ceramic sintered body thus obtained were measured. The results are also shown in Table 1.

It should be noted that Comparative Example 1 in the table is provided for comparison with the present invention, and the amount of HfO ₂ powder used in the above Examples is outside the range of the present invention.

Further, in Comparative Example 2, the raw material powder was prepared without using HfO ₂ in the above Example, and hot press sintering was performed in a nitrogen gas atmosphere at 1850 ° C. for 1 hour. .

[Effects of the Invention] As is clear from the above examples, the ceramic sintered body having the sialon of the present invention as the mother phase has a non-crystalline structure after the addition amount of hafnium oxide is increased. Densification sintering can also be performed by pressure sintering. Further, it has an excellent fracture toughness value even when compared with a sintered body densified by hot pressing without adding hafnium oxide. Therefore, it is possible to obtain a highly reliable sialon-based sintered body having an excellent fracture toughness value by non-pressure sintering which is excellent in mass productivity.

Claims (3)

[Claims] 1. A ceramic sintered body having a main constituent phase substantially satisfying a sialon composition as a mother phase. Hafnium oxide in the range of 1 to 60 parts by weight based on 100 parts by weight of the mother phase. And a ceramics sintered body characterized by containing 5 to 30 parts by weight of silicon carbide dispersed therein. 2. Silicon nitride containing aluminum oxide in the range of 2.5 to 20% by weight, hafnium oxide in the range of 1 to 60 parts by weight, and 5 to 5 parts by weight based on 100 parts by weight of the silicon nitride.
A ceramics sintered body, which is obtained by molding and sintering a mixture with 30 parts by weight of silicon carbide. 3. A silicon nitride powder containing aluminum oxide powder in the range of 2.5 to 20% by weight, and this silicon nitride powder.
A step of mixing hafnium oxide powder in the range of 1 to 60 parts by weight and silicon carbide powder in the range of 5 to 30 parts by weight with respect to 100 parts by weight, and molding the mixed powder into a desired shape And a step of sintering the compact in a non-pressurized atmosphere.