JPH04132668A - Ceramic sintered compact and production thereof - Google Patents

Abstract

PURPOSE:To obtain a ceramic sintered compact excellent in toughness value even by unpressured sintering by providing a structure in which a specific amount of hafnium oxide and silicon carbide are dispersed in a sialon-based sintered compact. CONSTITUTION:A ceramic sintered compact is obtained by dispersing and containing hafnium oxide in an amount within the range of 1-60wt.% based on 100 pts.wt. parent phase of a ceramic sintered compact having the main constituent phase substantially satisfying the sialon composition and silicon carbide in an amount within the range of 5-30 pts.wt. based on 100 pts.wt. aforementioned parent phase therein.

Description

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

(Prior art) Sialon-based sintered bodies whose main constituent element is St-AI-0-N have a small coefficient of thermal expansion and are excellent in heat resistance, oxidation resistance, corrosion resistance, etc., and are similar to 513N4-based sintered bodies and Attempts have been made to use it as a structural material together with SiC-based sintered bodies.

Although such sialon-based sintered bodies have characteristics such as less strength loss in high temperature ranges and excellent oxidation resistance compared to 5J3N4-based sintered bodies, they have the disadvantage that they do not have sufficient toughness. Therefore, it was too unreliable to be used as a construction material.

Therefore, attempts have been made to disperse particles that do not form a solid solution with sialon, such as particles of SiC, in the sialon-based sintered body, and to improve the toughness value through the combined effect of the dispersed particles.

(Problem to be Solved by the Invention) However, as described above, in order to disperse and contain particles such as SiC in a sialon-based sintered body, when dissimilar particles such as SiC are added to powder that satisfies the sialon composition. However, there was a problem in that the sinterability was significantly reduced.

Therefore, in order to perform densification sintering under non-pressure sintering conditions, it is necessary to add only about 5 parts by weight of SiC, etc., which will become dispersed particles, to 100 parts by weight of SiAlON powder, which is sufficient. No significant toughness improvement effect was obtained.

On the other hand, by using the hot press method, it is possible to add up to 50 parts by weight of SIC etc. to 100 parts by weight of Sialon powder, but the hot press method is limited to simple shapes; There are problems such as high manufacturing cost, which makes it unsuitable for mass production, and there is also a problem that mechanical strength such as fracture toughness is insufficient. The same applies to HIP and the like.

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

The present invention was made to address these issues, and uses SiAlON as a matrix, which is dense, has excellent toughness, and can be obtained by non-pressure sintering, which is suitable for mass production. The object of the present invention is to provide a ceramic sintered body and a method for manufacturing the same.

[Structure of the Invention] (Means and Effects for Solving the Problems) 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 matrix, and this matrix 1 per 100 parts by weight of the matrix in
~60 parts by weight of oxide/% funium and 5 to 30 parts by weight
It is characterized by containing dispersed silicon carbide in the range of parts by weight. Furthermore, the ceramic sintered body of the present invention contains silicon nitride containing aluminum oxide in a range of 2.5 to 20% by weight, and hafnium oxide in a range of 1 to 60 parts by weight per 100 parts by weight of the silicon nitride. 5～
It is characterized by being formed by molding and sintering a mixture with 30 parts by weight of silicon carbide.

In addition, the method for producing a ceramic sintered body of the present invention includes silicon nitride powder containing aluminum oxide powder in an amount of 2.5 to 20% by weight, and 1 to 60 parts by weight based on 100 parts by weight of this silicon nitride powder. A step of mixing hafnium oxide powder in the range of 5 to 30 parts by weight of silicon carbide powder, molding the mixed powder into a desired shape, and sintering the resulting molded body in a non-pressurized atmosphere. It is characterized by having a process.

The parent phase of the ceramic sintered body of the present invention may be one in which the main constituent phase satisfies the sialon composition, and does not necessarily need to be entirely sialon. That is, if 90% by weight or more of the parent phase is sialon, the effects of the present invention can be obtained, and therefore a grain boundary phase such as a glass phase may also be included.

Therefore, the raw material powder for obtaining the matrix does not necessarily have to strictly satisfy the sialon composition.

Although sialon has a β-sialon composition and an α-sialon composition, the matrix of the ceramic sintered body of the present invention is substantially β-sialon. however,
It is also possible to use α-type sialon.

Furthermore, as described above, the ceramic sintered body of the present invention contains hafnium oxide and silicon carbide dispersed in the parent phase. These hafnium oxide and silicon carbide do not dissolve solidly in the crystal grains of Sialon, so they exist in the form of particles in the matrix structure and constitute a dispersed phase.

The above hafnium oxide has a function as a sintering aid for ceramic powder that contains silicon carbide and substantially satisfies the SiAlON composition, and also contributes to improving the mechanical strength of the sintered body as dispersed particles after sintering. It is something to do. That is, even in a system to which silicon carbide is added, the presence of hafnium oxide facilitates densification and sintering, making it possible to add a large amount of silicon carbide. The amount of hafnium oxide added is in the range of 1 to 60 parts by weight, preferably in the range of 5 to 50 parts by weight, and more preferably in the range of 10 to 30 parts by weight, based on 100 parts by weight of the above-mentioned matrix. If the amount of hafnium oxide added is less than 1 part by weight, sufficient densification cannot be achieved, and if it exceeds 60 parts by weight, sinterability may be inhibited or the specific gravity may increase.

In addition, silicon carbide is a component that aims to improve the toughness of the matrix that substantially satisfies the above-mentioned sialon composition, and when used in combination with the above-mentioned hafnium oxide, silicon carbide can be
It becomes possible to add as much as 30 parts by weight. The toughness-improving effect of silicon carbide becomes noticeable from about 5i1L part, but if it exceeds 30 parts by weight, it becomes difficult to achieve sufficient densification even when used in combination with hafnium oxide.

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

First, approximately 2.5 to 20% by weight of Al203 powder is added to Si3N4 powder to prepare a matrix powder that approximately satisfies the β-type sialon composition. A1□03 is 9i,
It dissolves in N4 to form sialon, but if the amount added exceeds 20% by weight, the strength decreases and the amount of secondary phases such as grain boundary layers increases. , also 2, 5
If it is less than % by weight, densification becomes difficult. The optimal blending amount of AI203 is 10 parts by weight.

Here, the matrix powder is not limited to the above-mentioned powder, but also Si3
N 4 Al2 03 AIN system, Si3N 4
Although it is possible to use only AlN5in2 type powder or commercially available synthetic β-type sialon powder, the above-mentioned Si3N
According to the 4AI203 series, since effects such as grain refinement can be obtained, the effect of improving properties is higher than that of a synthetic β-sialon powder or a mixed powder that satisfies the usual β-sialon composition. In addition, the formation of the β-type iron phase was suppressed by A1□0. It is also possible to use water as a dispersion medium.

Next, a predetermined amount of Hf'02 and SiC are added to the above matrix powder and thoroughly mixed to prepare a raw material powder for the ceramic sintered body of the present invention.

Here, the starting material of 11fO□ has an average particle size of 2
Fine powder with a particle size of 1 μm or less, preferably 1 μm or less, is suitable. Further, as the starting material for SiC, a particle-shaped material or a fiber-shaped material such as a whisker can be used. However, when using particle-shaped SjC, if the particles are too large, they may cause defects and reduce mechanical strength, so use particles with an average particle size of 50 μm or less and a maximum particle size of 100 μm or less. It is preferable to do so.

Next, the raw material powder for the ceramic sintered body is molded into a desired shape by a known molding method such as a press molding method. After this, the above molded body is placed in a non-pressurized atmosphere of 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 by the above-mentioned non-pressure sintering, and the fracture toughness value can be improved. However, this does not preclude the application of other firing methods such as atmosphere pressure sintering method, hot press method, hot isostatic pressure sintering method (HIP), etc.

(Example) Hereinafter, the present invention will be explained by examples.

Examples 1 to 12 First, a plurality of matrix powders were prepared using Si3N4 powder with an average particle size of 0.7 μm and Al2O3 powder with an average particle size of 0.9 μm at each blending ratio shown in Table 1.

Next, for each part by weight of the above powder for matrix, 1 lro with an average particle size of 0.9 μm, powder and an average particle size of 0.5 μm
SiC powder or SiC with an aspect ratio of 1:2o
Whiskers were added in the composition ratios (parts by weight) shown in Table 1, and each was placed in a ball mill for 48 hours using ethanol as a dispersion medium, and then dried to obtain raw material powder for ceramic sintered bodies.

Next, approximately 5 parts by weight of a binder was added to 100 parts by weight of the raw material powder for each of the above sintered bodies, and a molded plate having a length of 50 mm, a width of 50 mm, and a thickness of 5 ml was produced using a molding pressure of approximately 1000 kg/cm2. . After that, each of these molded bodies was degreased in a nitrogen gas atmosphere, and then sintered at 1850°C for 2 hours in a nitrogen gas atmosphere at normal pressure to form a ceramic sintered body with Sialon as the matrix. A concretion was produced.

Sintered density of each ceramic sintered body thus obtained and fracture toughness value KIC determined by microindentation method
and were measured respectively. The results are also shown in Table 1.

Comparative Example 1 in the table is provided for comparison with the present invention, and the amount of Lf02 powder used in the above example was outside the scope of the present invention.

In Comparative Example 2, the raw material powder was prepared without using III'02 in the above example, and hot press sintering was performed at 1850°C for 1 hour in a nitrogen gas atmosphere. be.

(The following is a blank space) [Effect of the invention] As is clear from the above examples, the ceramic sintered body of the present invention having sialon as a matrix has an increased amount of silicon carbide by adding hafnium oxide. Densification sintering can also be achieved by non-pressure sintering. moreover,
Even when compared with a sintered body densified by hot pressing without adding hafnium oxide, it has an excellent fracture toughness value. Therefore, it becomes possible to obtain a highly reliable sialon-based sintered body with excellent fracture toughness by non-pressure sintering, which is excellent in mass production.

Applicant: Toshiba Corporation

Claims (3)

[Claims] (1) A ceramic sintered body whose main constituent phase substantially satisfies the SiAlON composition is used as a matrix, and the matrix contains 10% of the matrix.
A ceramic sintered body characterized in that hafnium oxide in the range of 1 to 60 parts by weight and silicon carbide in the range of 5 to 30 parts by weight are dispersed and contained relative to 0 parts by weight. (2) silicon nitride containing aluminum oxide in a range of 2.5 to 20% by weight, and hafnium oxide in a range of 1 to 60 parts by weight per 100 parts by weight of this silicon nitride;
The mixture with silicon carbide in the range of ~30 parts by weight is molded,
A ceramic sintered body characterized by being made by sintering. (3) Silicon nitride powder containing aluminum oxide powder in a range of 2.5 to 20% by weight, and this silicon nitride powder 1
00 parts by weight of 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; 1. A method for producing a ceramic sintered body, comprising the step of sintering the molded body in a non-pressurized atmosphere.