JP2858811B2 - Ceramic composite sintered body and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a ceramic composite sintered body having improved toughness and strength, and a method for producing the same.

[Related Art] Ceramics have long been used as refractories and chemical materials because of their excellent heat resistance and corrosion resistance and high hardness. In addition, with the recent development of chemical technology, the precision of high-purity raw materials and the synthesis technology have advanced, and with the progress of process control technology, the characteristics of ceramics have also changed significantly, and many expectations have been raised. In particular, heat-resistant alloys have been used in applications where they are exposed to high temperatures or adverse environments such as gas turbine blades. Has been required, and ceramics have begun to attract attention as an important material satisfying these requirements. This is because the ceramic material is remarkably excellent in heat resistance, oxidation resistance and corrosion resistance as compared with other materials.

However, ceramics such as silicon nitride, alumina and silicon carbide are generally brittle, for example, having a fracture toughness of 5 MNm.
^{Many are -3/2} or less. For this reason, various methods for improving the toughness and strength of ceramics have been proposed and implemented.

For example, Japanese Patent Application Laid-Open
As disclosed in JP-A-59-30770, a method of adding a material having a needle-like form such as whisker or fiber as a reinforcing material is known. In this case, it is considered that the improvement in toughness is achieved by a crack deflecting effect in which cracks generated in the ceramics are bent by the whiskers and the like dispersed in the ceramics, a whisker pull-out effect, and the like.

However, it is difficult to uniformly disperse the acicular reinforcing material in the ceramic. This is because, in the case of a fiber or the like, the fibers are entangled with each other in the ceramic,
Due to the tendency to clump.

On the other hand, as a method for toughening alumina ceramics, a method of adding zirconia as a reinforcing material has been proposed as shown in JP-B-59-25748. In this method, a metastable tetragonal crystal of zirconia is allowed to remain in alumina at room temperature, and a volume expansion of about 4% of a crystal transformation from tetragonal to monoclinic induced by stress at a crack tip. The mechanical properties at room temperature are remarkably improved by the residual compressive stress caused by the above.

However, also in this method, when the material is kept for a long time in the atmosphere at the above transformation temperature of about 900 ° C. or more, a reaction proceeds between the zirconium oxide and the non-oxide base material, and the base material characteristics Cannot be maintained, the above toughening effect could not be expected.

Further, Japanese Patent Application Laid-Open No. 61-174165 proposes a method of increasing the strength by dispersing silicon carbide in an alumina base material in order to solve the above-mentioned problems of the prior art. In this method, silicon carbide particles having an average particle diameter of 3 μm or less, or silicon carbide fibers (whiskers) having a diameter of 1 μm or less and a length of 20 μm or less are independently dispersed in an alumina matrix, and locally dispersed in the alumina matrix. It is intended to impart a high residual stress and improve mechanical properties at high temperatures.

[Problems to be Solved by the Invention] However, in the case of high toughness and high strength by dispersing whiskers and fibers in the above ceramics, it is difficult to uniformly disperse whiskers and fibers. Even if they can be dispersed relatively uniformly, a ceramic composite sintered body with good characteristics cannot be obtained unless special treatment is performed in the manufacturing process. However, there is a problem in that the use of a high price increases the cost. Further, in the case of increasing the toughness by dispersing the zirconium oxide particles, the toughening effect is lost at a high temperature at which the transformation does not proceed. Furthermore, when held at a high temperature for a long time, the reaction between zirconium oxide and the non-oxide as a base material proceeds,
There were problems such as the inability to maintain the properties of the base material.

An object of the present invention is to provide a ceramic composite sintered body having high toughness and high strength by adding silicon carbide particles having a predetermined shape as a reinforcing material to an oxide base material or a non-oxide base material, and a manufacturing method thereof. Is to do.

[Means for Solving the Problems] In order to achieve the above object, a ceramic composite sintered body according to the present invention comprises an oxide ceramic such as alumina, mullite, magnesia or a non-oxide ceramic such as silicon nitride or sialon. Is used as a base material, and as a reinforcing material, silicon carbide particles having a size of 1 μm or less and ranging from 5 to 20 μm are included in a volume ratio of 10 to 50%. Sintering at a temperature in the range of 11900 ° C., and in the case where the base material is the oxide ceramic, sintering at a temperature in the range of 1500-2000 ° C.

Further, the present invention has a size of 1 μm or less and 5 to 20 μm.
Containing 10 to 50% by volume of silicon carbide particles over both ranges, the remainder substantially forming a mixed powder of oxides such as alumina, mullite, magnesia or non-oxides such as silicon nitride and sialon, A molded body obtained from the mixed powder is prepared using an oxide ceramic as a base material.
It is characterized in that sintering is performed at a temperature in the range of 1400 to 1900 ° C. or a temperature of 1500 to 2000 ° C. for non-oxide ceramics as a base material.

Furthermore, the present invention is based on any one of oxide ceramics such as alumina, mullite and magnesia or non-oxide ceramics such as silicon nitride and sialon as a base material, as a reinforcing material, silicon carbide particles having a size of 1 μm or less, and It is characterized by containing plate-like silicon carbide particles having a maximum diameter of 5 to 50 μm and a thickness of 1/3 or less of the maximum diameter in a volume ratio of 10 to 50%.

Also, the present invention contains 10 to 50% by volume of silicon carbide particles having a size of 1 μm or less and plate-like silicon carbide particles having a maximum diameter of 5 to 50 μm and a thickness of 1/3 or less of the maximum diameter, with the balance being the rest. A mixed powder substantially formed of an oxide such as alumina, mullite, magnesia or a non-oxide such as silicon nitride or sialon is formed, and a molded body obtained from the mixed powder is formed using an oxide ceramic as a base material. It is characterized by sintering at a temperature in the range of 1400 to 1900 ° C. for those that do, or at a temperature of 1500 to 2000 ° C. for those using non-oxide ceramics as a base material.

[Function] In the present invention, silicon carbide particles having a size of 1 μm or less and 5 to 20 μm as a reinforcing material are both added to a base material of an oxide ceramic such as alumina or a non-oxide ceramic such as silicon nitride in a volume ratio of 10 to 10 μm. A mixed powder is formed by adding 50%, preferably 20/40%, or silicon carbide particles having a size of 1 μm or less and a maximum diameter of 5 to 50 μm, preferably 10 to 50 μm.
A molded product obtained by adding 40 to 50%, preferably 20 to 40% by volume of silicon carbide particles in a plate shape having a thickness of 40 μm and a thickness of 1/3 or less of the maximum diameter, and forming a mixed powder. Sintered in a temperature range of 1400 to 1900 ° C for those based on oxide ceramics, or at a temperature range of 1500 to 2000 ° C for those based on non-oxide ceramics. Thus, a high-strength ceramic composite sintered body can be obtained.

EXAMPLES Next, preferred examples of the high-toughness, high-strength ceramic composite sintered body and the method for producing the same according to the present invention will be described in detail with reference to the accompanying drawings.

The sintered body according to the present invention is composed of oxide ceramics such as alumina, magnesia, and mullite as a base material, or non-oxide ceramics such as silicon nitride and sialon, and silicon carbide particles as a reinforcing material. You. In this case, a small amount of other components contained as impurities in the raw material may be present. It is preferable to include a sintering aid, as in the case of a sintered body based on ordinary oxide ceramics or non-oxide ceramics. As the molding method, all ordinary molding methods such as press molding, slip casting, injection molding, and extrusion molding can be applied.
Sintering was performed in a vacuum or non-oxidizing atmosphere using a hot press (HP), but normal pressure sintering and pre-sintering HIP (sin
The same effect can be obtained with ter-HIP) or capsule HIP (encapsulated in a capsule).

The sintering temperature is 1400-1900 ° C when using oxide ceramics as the base material, 1500 when using non-oxide ceramics.
~ 2000 ℃ range. When the base material is a non-oxide ceramic, if the sintering temperature is 1700 ° C or higher, the decomposition of silicon nitride and sialon used as the base material will be severe,
The pressure in the nitrogen atmosphere was increased, and the reaction was usually performed at 9 to 9.9 kg · f / cm ² .

When the sintering temperature is lower than the above range, the density of the obtained sintered body is low, and conversely, when the sintering temperature is higher than that, the base material is decomposed as described above. Could not be obtained. The optimum sintering temperature in this case is the conditions of normal pressure sintering, hot pressing, sinter HIP, capsule HIP,
And it changed depending on the size and amount of silicon carbide particles of the reinforcing material. On the other hand, if the added amount of silicon carbide is less than 10% by volume, the effect of improving fracture toughness and strength is not recognized, and if it is more than 50%, the density of the obtained ceramic composite sintered body is low, and Not achieved. Further, when the size of the silicon carbide particles did not fall in both the range of 1 μm or less and 5 to 20 μm, the characteristics were not improved. That is,
When particles of 1 μm or less are not included, there is no effect of improving strength, while when particles of 5 to 20 μm are not included, that is, only particles of 1 to 5 μm and particles of 1 μm or less and 1 to 5 μm are included. In the case of the combination with the particles, the fracture toughness was not improved. Furthermore, in the case of a combination of only the particles of 20 μm or more and the combination of the particles of 1 μm or less and the particles of 20 μm or more, the density of the obtained ceramic composite sintered body was reduced and the densification was not achieved.

The characteristics are not improved when silicon carbide particles having a size of 1 μm or less and plate-like silicon carbide particles having a maximum diameter of 5 to 50 μm and a thickness of 1/3 or less of the maximum diameter are not included at the same time. That is, when particles of 1 μm or less are not contained, there is no effect of improving strength, while the maximum diameter is 5 to 50 μm and the thickness is 1/3.
When the following plate-like particles were not contained, that is, in the case of a combination of particles of 1 μm or less and plate-like particles having a maximum diameter of 5 μm or less, the fracture toughness was not improved. Furthermore, 1μ
In the case of a combination of particles of m or less and plate-like particles having a maximum diameter of 50 μm or more, the density of the obtained ceramic composite sintered body was low, and densification was not achieved.

The four-point bending strength test was measured in accordance with JIS R1601 "Bending strength test method for fine ceramics". The fracture toughness is measured by the SEPB method (Single Edge Pre-cracked Beam method).
Was measured by That is, a sample conforming to JIS R1601 is prepared, and after indenting by Vickers indentation,
A load was applied to create a pre-crack, and pop-in (Pop-In) was detected with earphones. Subsequently, coloring was performed to measure the length of the pre-crack, and a bending test was performed to measure the breaking load. After measuring the pre-crack length of the fractured sample, the fracture toughness value was determined by the fracture toughness calculation formula.

 Next, specific examples will be described.

FIG. 1 is an explanatory view showing the method of the present invention. First, the base material and the reinforcing agent are placed in a pot mill and mixed in water or ethanol for 24 hours to form a mixture. As described above, the reinforcing agent may be used when the oxide ceramic is used as the base material or when the non-oxide ceramic is used.
The volume content ratio is 10-50%, and the size is 1 μm
Silicon carbide particles ranging both below and 5-20 μm,
Alternatively, both silicon carbide particles having a size of 1 μm or less and plate-like silicon carbide particles having a maximum diameter of 5 to 50 μm and a thickness of 1/3 or less of the maximum diameter were used.

FIG. 2 is an explanatory diagram showing the definition of silicon carbide particles in the present invention. As shown in FIG. 2 (a), the silicon carbide particles are defined as those having a minor axis diameter (interval at a minimum interval between two parallel lines) of 5 to 20 μm. Further, the plate-like silicon carbide particles have a preferable shape in the present invention, and the definition is shown in FIG. 2 (b). That is, the plate-like particles are defined as having a maximum diameter of 5 to 50 μm and a thickness of 1/3 or less of the maximum diameter.

Next, the obtained mixture was dried at 120 ° C. for 24 hours, and passed through a sieve having a mesh size of 149 μm to obtain a molding powder.

Next, press molding is performed at a pressure of 200 kg / cm ² , and in some cases, rubber press molding is performed at a pressure of 7 ton / cm ² and firing is performed. The HP temperature under 1atm Ar atmosphere using oxide ceramics as base material is
1400-1900 ° C, 1atm N _{2 for} non-oxide ceramics
To 1500 to 2000 ° C. HP pressure was 300 kg / cm ² . In the case of non-oxide ceramics, at a temperature of 1700 ° C. or higher, the N ₂ pressure was set to 9.5 atm for the reason already described.

Tables 1-1 and 1-2 show the results of the toughening and high strength obtained in this manner. Alumina, mullite, and magnesia were used as the oxide ceramics of the base material, and non-oxide The values are shown in the case where silicon carbide is added as a reinforcing material to silicon nitride and sialon as ceramics under the conditions shown in the table, respectively.

[Effect of the Invention] The ceramic composite sintered body according to the present invention has a high toughness by dispersing and adding silicon carbide particles of an appropriate size and shape at an appropriate volume ratio to an oxide or non-oxide base material. There is an effect that ceramics exhibiting high strength can be obtained. In addition, special equipment is not particularly required, and only ordinary ceramic manufacturing equipment is used, so that the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of a method for producing a ceramic composite sintered body according to the present invention, and FIG. 2 is an explanatory view defining dimensions of silicon carbide particles of a reinforcing material.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-78975 (JP, A) JP-A-64-79063 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 35/71-35/84

Claims (4)

(57) [Claims] The present invention relates to a base material made of one of oxide ceramics such as alumina, mullite and magnesia and non-oxide ceramics such as silicon nitride and sialon, and a reinforcing material having a size of 1 μm or less and 5 to 20 μm. It contains 10 to 50% by volume of silicon carbide particles over the range, and when the base material is the oxide ceramic, it is sintered at a temperature in the range of 1400 to 1900 ° C., and when the base material is the non-oxide ceramic, it is 1500 A ceramic composite sintered body characterized in that it is sintered at a temperature in the range of -2000 ° C. 2. The method according to claim 1, wherein said silicon carbide particles have a volume ratio of 10 to 50% in a range of 1 μm or less and 5 to 20 μm, and the remainder substantially consists of oxides such as alumina, mullite, magnesia, silicon nitride, and sialon. Form a mixed powder made of non-oxide such as, the molded body obtained from the mixed powder, the temperature in the range of 1400 ~ 1900 ℃, or non-oxidized A method for producing a ceramic composite sintered body, comprising sintering a ceramic-based material as a base material at a temperature in the range of 1500 to 2000 ° C. 3. A silicon carbide particle having a size of 1 μm or less as a reinforcing material, wherein one of oxide ceramics such as alumina, mullite and magnesia or non-oxide ceramics such as silicon nitride and sialon is used as a base material. A ceramic composite sintered body containing 10 to 50% by volume ratio of plate-like silicon carbide particles having a maximum diameter of 5 to 50 μm and a thickness of 1/3 or less of the maximum diameter. 4. A silicon carbide particle having a size of 1 μm or less and plate-like silicon carbide particles having a maximum diameter of 5 to 50 μm and a thickness of 1/3 or less of the maximum diameter in a volume ratio of 10 to 50%, with the balance being the rest. A mixed powder substantially composed of an oxide such as alumina, mullite, magnesia or a non-oxide such as silicon nitride or sialon is formed, and a molded body obtained from the mixed powder is formed using an oxide ceramic as a base material. A ceramic composite sintered body characterized in that it is sintered at a temperature in the range of 1400 to 1900 ° C for the material to be heated, or at a temperature in the range of 1500 to 2000 ° C for the material based on non-oxide ceramics. Manufacturing method.