JPH07108819B2 - Method for manufacturing ceramic sintered body - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a ceramic sintered body, and more particularly to a method for producing a ceramic sintered body using a high temperature isostatic press (HIP).

(Prior Art) Conventionally, as a method for producing a highly dense silicon nitride sintered body using a high temperature isostatic press, a sintering aid and an organic binder are added to silicon nitride powder, and the material is formed by press molding or the like. The formed body is coated with glass and is subjected to high temperature isostatic pressing (Japanese Patent Publication No. 59-35870), or the formed body is formed by press forming, etc. by adding a sintering aid to the nitride powder under normal pressure. A method (Japanese Patent Publication No. 63-57388) is known in which heat treatment is performed in the temperature range of ˜1700 ° C. and the molded body after the heat treatment is hot isostatically pressed.

(Problems to be Solved by the Invention) However, according to the conventional method for producing a ceramic sintered body using a high temperature isostatic press, a sintered body having a composition of a grain boundary phase having a high melting point, or a sintered material having a low sintering property is used. In the case of manufacturing a body, a sintered body or the like made of a composite material, there is a problem that the high temperature strength of the ceramic sintered body cannot be sufficiently enhanced.

The present invention has been made in order to solve such a problem, by forming a surface coating layer using a base material in a molded body in which a reinforcing material is added to the base material and performing heat treatment,
An object of the present invention is to provide a method for producing a ceramic sintered body, which eliminates open pores in a molded body, enables a molded body having a complicated shape to be fired at high density, and is excellent in heat resistance, oxidation resistance and high temperature strength.

(Means for Solving the Problem) Therefore, in the method for manufacturing a ceramic sintered body according to the present invention, a ceramic mixed powder containing a ceramic base material and a ceramic reinforcing material is molded, and the molded body is surface-coated with the ceramic base material powder. It is characterized in that a coating layer is formed, the molded body having the surface coating layer formed thereon is heat-treated at a heat treatment temperature of 1500 to 1950 ° C., then coated with glass and subjected to high temperature isostatic pressing sintering.

As the ceramic base material, oxide ceramics such as alumina and mullite or non-oxide ceramics such as silicon nitride and sialon are used.

The ceramic reinforcing material is preferably at least one of silicon carbide granular particles, silicon carbide plate-like particles, and silicon carbide whiskers.

The heat treatment conditions are such that when the ceramic base material is oxide ceramics such as alumina and mullite, heat treatment is performed at a temperature of 1500 to 1800 ° C., and when the ceramic base material is non-oxide ceramics such as silicon nitride and sialon, the temperature in a nitrogen atmosphere is set. 1750 ~
It is desirable to heat-treat at 1950 ° C and 9.5 atm.

In the above-mentioned method for producing a ceramic sintered body, when the base material is an oxide ceramic, the heat treatment temperature is 1500 to 1800 ° C.
The reason why the range is set is that if the heat treatment temperature is lower than 1500 ° C, the open pores cannot be eliminated and the glass permeates through the open pores during hot isostatic pressing.
The reason below is that when the temperature exceeds 1800 ° C, voids (foaming phenomenon) occur between the base material and the reinforcing material, and open pores are formed on the surface of the molded body after heat treatment, and the glass penetrates through these open pores during hot isostatic pressing. However, the high-temperature strength of the sintered body in which the glass has permeated is affected by the glass component and is lowered.

On the other hand, when the base material is non-oxide ceramics, the heat treatment temperature is set in the range of 1750 to 1950 ° C because the open pores cannot be eliminated when the heat treatment temperature is lower than 1750 ° C and the glass is not pressed during high temperature isostatic pressing. Is permeated through these open pores, and the temperature of 1950 ° C. is that silicon nitride,
This is because the sialon is decomposed and open pores are formed on the surface of the molded body after the heat treatment, the glass permeates through the open pores at the time of hot isostatic pressing, and the high temperature strength of the sintered body in which the glass permeates decreases.

(Example) Hereinafter, the Example of this invention is described based on drawing. The manufacturing process is shown in FIG.

The raw material powder uses oxide ceramics such as alumina and mullite as the base material, or non-oxide ceramics such as silicon nitride and sialon, and uses silicon carbide particles, silicon carbide plate-like particles, and silicon carbide whiskers as the reinforcing material. .
In this case, a small amount of other components contained as impurities in the raw material may be present. Further, it is preferable to include a sintering aid as in the case of a sintered body having a usual oxide ceramic or non-oxide ceramic as a base material.

As the molding method, all the usual molding methods such as press molding, mud casting molding, injection molding, and extrusion molding can be applied.

Next, a surface coating layer is formed on the surface of the obtained molded body with the ceramic base material powder. The surface coating layer is formed by brush coating, spray coating, dipping or the like.

Next, when the base material is an oxide ceramics such as alumina or mullite, the temperature is 1500 with respect to the molded body on which the surface coating layer is formed.
Heat treatment is performed at ~ 1800 ° C under a pressure of 9.5 atm. When the base material is a non-oxide ceramic such as silicon nitride or sialon, the heat treatment is performed in a nitrogen atmosphere at a temperature of 1750 ~ 1950 ° C under a pressure of 9.5 atm.

The heat-treated (pre-sintered) molded body is surface-coated with glass. The surface coating with glass can be carried out by directly coating the surface of the molded article with glass, or by putting it in a glass capsule for deaeration.

By subjecting the pre-sintered body whose surface is coated with glass to high temperature isostatic pressing (HIP), a ceramic sintered body having a high density and excellent heat resistance, oxidation resistance and high temperature strength is obtained.

Examples will be specifically described below.

Examples 1 to 10 The raw material powders of Examples 1 to 10 have an average particle diameter of 0.5 μm, a BET specific surface area of 5.0 m ² / g, and an alumina powder having a purity of 99.5% or more as a base material, silicon carbide granular particles, and a silicon carbide plate. Particles and silicon carbide whiskers were used as the reinforcing material. Table 1 shows the blending ratio of the base material and the reinforcing material and the shape and size of the reinforcing material. The base material and the reinforcing material were mixed using a polyethylene wide-mouthed bottle with an internal volume of 1 and a nylon-coated steel ball boulder.
g, water or 300 ml of ethyl alcohol was added and wet-mixed for 20 hours. At this time, in the case where the reinforcing material was silicon carbide whiskers, they were well dispersed in advance using an ultrasonic cleaner and then wet mixed. The obtained mixture was dried at 120 ° C. for 24 hours and sized using a sieve having a mesh of 149 μm to obtain a molding powder. This molding powder is pressed into a mold and the size is 50 x 40 x 6 m.
A molded body of m was produced. The molded body was rubber-pressed at a pressure of 7 ton / cm ² . Then, a surface coating layer was formed on the obtained molded body with alumina powder. The molded body having this surface coating layer was heat-treated in an argon atmosphere within a temperature range of 1500 to 1800 ° C. Then, the heat-treated molded body was put into a glass capsule, deaerated, and sintered by a high temperature isostatic press in an argon atmosphere. The conditions of heat treatment and hot isostatic pressing are shown in Table 1.

In Table 1, Comparative Examples 1 and 2 are examples of sintering by high-temperature isostatic pressing without heat treatment, and Comparative Examples 3 and 4 are heat-treated outside the heat treatment temperature range of 1500 to 1800 ° C. This is an example of hydraulic pressing.

The density and four-point bending strength of the obtained ceramic sintered bodies (Examples 1 to 10 and Comparative Examples 1 to 4) were measured. The density was measured by the Archimedes method, and the four-point bending strength was measured at room temperature and 1200 ° C according to the "bending strength test method for fine ceramics" (JIS r-1601). The results are shown in Table 1. The values of the density and the four-point bending strength shown in Table 1 are the average values of the test results for the three sintered bodies.

From the results shown in Table 1, it can be seen that the ceramic sintered body obtained by the present invention has high density and high strength at high temperature.

Examples 11 to 20 The raw material powders of Examples 11 to ²⁰ have mullite powder having an average particle size of 1.0 μm and a BET specific surface area of 10 m ² / g as a base material, and have silicon carbide granular particles, silicon carbide plate-like particles, and silicon carbide whiskers. Was used as a reinforcing material. The manufacturing method is in accordance with Examples 1 to 10.

Table 2 shows the blending ratio of the base material and the reinforcing material, the shape and size of the reinforcing material, and the conditions of heat treatment and high temperature isostatic pressing in Examples 11 to 20.

In Table 2, Comparative Example 5 and Comparative Example 6 are examples of sintering by high temperature isostatic pressing without heat treatment, and Comparative Example 7 and Comparative Example 8 are heat treated outside the heat treatment temperature range of 1500 to 1800 ° C. This is an example of hydraulic pressing.

The density and four-point bending strength of the obtained ceramic sintered bodies (Examples 11 to 20 and Comparative examples 5 to 8) were measured. The density was measured by the Archimedes method, and the four-point bending strength was measured at room temperature and 1200 ° C according to the "bending strength test method for fine ceramics" (JIS R-1601). The results are shown in Table 2. The values of the density and the four-point bending strength shown here are the average values of the test results for three sintered bodies.

From the results shown in Table 2, it is understood that the ceramic sintered body obtained by the present invention has high density and high strength at high temperature.

Examples 21 to 34 Examples 21 to 34 are nitrides containing two or more of Y ₂ O ₃ , Er ₂ O ₃ , Tm ₂ O ₃ , Yb ₂ O ₃ , and Lu ₂ O ₃ as a sintering aid. Silicon powder was used as a base material, and silicon carbide granular particles, silicon carbide plate-like particles, and silicon carbide whiskers were used as a reinforcing material and mixed. This mixture is molded, a surface coating layer is formed on the molded body from the above-mentioned silicon nitride base material powder, and the molded body on which the surface coating layer has been formed is subjected to a heat treatment as pre-baking, and then a glass capsule is used for high temperature treatment. Isostatic press sintering.

First, metal or cation impurities (C, Al, Fe, Mg,
Ca, etc.) containing 0.1 wt% oxygen content 2.2 wt%, average particle size 0.5
μm, BET specific surface area 15m ² / g Silicon nitride raw material powder, Y
₂ O ₃ , Er ₂ O ₃ , Tm ₂ O ₃ , Yb ₂ O ₃ or Lu ₂ O ₃ is added to the silicon nitride raw material powder by adding about 8 to 13 wt% of two or more sintering aids. Cobblestone made of silicon nitride porcelain and water were added, and mixed and pulverized using a nylon resin container. At this time, in the mixed pulverization, boulders and water were added to 1.8 g of boulders and 300 ml of water with respect to 200 gr of the above-mentioned silicon nitride raw material powder, and the vibration frequency was set to 1200 by a vibration mill.
Rotation / min was carried out for 3 hours. The resulting mixture was heated at 120 ° C, 2
It was dried for 4 hours and sized using a sieve having a mesh of 149 μm to obtain a base material powder. Next, one kind of silicon carbide particles, silicon carbide plate-like particles, and silicon carbide whiskers were separately mixed with this powder for base material as a reinforcing material, and a polyethylene wide-mouthed bottle having an inner volume of 1 and a nylon-coated steel ball boulder were used. 200 gr
To 1.1 g of boulders, 300 ml of water or ethyl alcohol was added and wet mixed for 20 hours. At this time, in the case where the reinforcing material was silicon carbide whiskers, they were well dispersed in advance using an ultrasonic cleaner and then wet mixed. The obtained mixture was dried at 120 ° C. for 24 hours and sized using a sieve having a mesh of 149 μm to obtain a molding powder. This molding powder is pressed into a die and sized
A 50 × 40 × 6 mm molded body was produced. This molded body is 7ton / cm
Rubber pressed at a pressure of ² . Then, a surface coating layer was formed on the obtained compact by using the above-mentioned base material powder. This molded body was heat-treated at a temperature in the range of 1750 to 1950 ° C under a nitrogen atmosphere at 9.5 atm. After that, the heat-treated molded body is put into a glass capsule and degassed, and 1850 to 1950
Sintered by a high temperature isostatic press at a temperature of 500 to 2000 atm. After sintering, the ceramic sintered body from which the glass capsule was removed was further crystallized at 1400 ° C. for 6 hours in a nitrogen atmosphere.

The compounding ratio of the base material and the reinforcing material and the size of the reinforcing material used for manufacturing the ceramic sintered body are shown in Table 3, and the conditions of the heat treatment and the high temperature isostatic pressing are shown in Table 4.

Comparative examples 9, 10 and 11 in Tables 3 and 4 are examples in which sintering was performed by a high temperature isostatic press without heat treatment, and comparative examples.
12 and Comparative Example 13 are examples of heat treatment outside the heat treatment temperature range of 1750 to 1950 ° C. and high temperature isostatic pressing.

The density and four-point bending strength of the obtained ceramic sintered bodies (Examples 21 to 34 and Comparative Examples 9 to 13) were measured. The density was measured by the Archimedes method, and the four-point bending strength was measured at room temperature and 1400 ° C. according to the “Bending strength test method for fine ceramics” (JIS R-1601). The results are shown in Table 4. The values of density and four-point bending strength shown in Table 4 are average values of the test results for three sintered bodies.

From the results shown in Table 4, it is understood that the ceramic sintered body obtained by the present invention has high density and high strength at high temperature.

Examples 35 to 44 Examples 35 to 44 have an average particle size of 1.7 μm and a BET specific surface area of 5.9 m ² /
As a base material, 0.5 g of Y ₂ O ₃ as a sintering additive was added to g of sialon powder. Silicon carbide granular particles, silicon carbide plate-like particles, and silicon carbide whiskers were used as the reinforcing material.
For the mixing, a polyethylene wide-mouthed bottle having an internal volume of 1 and a nylon-coated steel ball boulder were used, and 1.1 kg of boulder and 300 ml of water or ethyl alcohol were added to a blending amount of 200 gr and wet-mixed for 20 hours.
At this time, when the reinforcing material was a silicon carbide whisker, it was well-dispersed in advance using an ultrasonic cleaner and then wet-mixed. The resulting mixture was dried at 120 ° C for 24 hours and had a mesh of 149 μm
The powder was sized using a sieve of No. 1 to obtain a molding powder. This molding powder was pressed by a mold to produce a molded body having a size of 50 × 40 × 6 mm. This molded body was rubber-pressed at a pressure of 7 ton / cm ² . Then, a surface coating layer was formed on the obtained compact by using the above-mentioned base material powder. This formed body was heat-treated in a temperature range of 1750 to 1950 ° C under a nitrogen atmosphere at 9.5 atm. Then, the heat-treated molded body was placed in a glass capsule, deaerated, and sintered by a high temperature isostatic press under the conditions of 1800 to 1900 ° C and 500 to 2000 atm.

Table 5 shows the mixing ratio of the base material and the reinforcing material used in the production of the ceramic sintered body, and the conditions of heat treatment and high temperature isostatic pressing.

Comparative Examples 14 and 15 are examples of sintering by high temperature isostatic pressing without heat treatment, Comparative Examples 16 and 17 are 17
This is an example of heat treatment outside the heat treatment temperature range of 50 to 1950 ° C. and high temperature isostatic pressing.

The obtained ceramic sintered body (Examples 35 to 44 and Comparative Example
14-17), the density and the four-point bending strength were measured. The density was measured by the Archimedes method, and the four-point bending strength was measured at room temperature and 1400 ° C. according to the “Bending strength test method for fine ceramics” (JIS R-1601). The results are shown in Table 5. The values of the density and the four-point bending strength shown in Table 5 are average values of the test results for three sintered bodies.
From the results shown in Table 5, it is understood that the ceramic sintered body obtained according to the present invention has high density and high strength at high temperature.

(Effects of the Invention) As described above, according to the method for manufacturing a ceramic sintered body of the present invention, a surface coating layer is formed from a ceramic base material powder on a molded body composed of a ceramic base material and a ceramic reinforcement material, and high temperature static By performing the pre-firing process before the hydraulic pressing process, it is possible to obtain a ceramic sintered body that is highly dense and has excellent heat resistance, oxidation resistance, and high-temperature strength, even if the molded body has a complicated shape. The effect is that you can do it.

[Brief description of drawings]

FIG. 1 is a process diagram showing a manufacturing process of an embodiment of the present invention, and FIG.
The figure is a characteristic diagram showing the relationship between temperature and time and pressure and time in the hot isostatic pressing process of the example of the present invention.

Claims (6)

[Claims] 1. A ceramic mixed powder containing a ceramic base material and a ceramic reinforcing material is molded, a surface coating layer is formed on the molded body with the ceramic base material powder, and the molded body having the surface coating layer formed thereon is subjected to a heat treatment temperature of 1500. After heat treatment at ~ 1950 ℃,
A method for producing a ceramic sintered body, which comprises coating with glass and performing high temperature isostatic pressing sintering. 2. The method for producing a ceramic sintered body according to claim 1, wherein the ceramic base material is an oxide ceramic such as alumina or mullite. 3. The heat treatment is performed at a heat treatment temperature of 1500 to 1800 ° C.
The method for producing a ceramic sintered body according to claim 2, wherein 4. The method for producing a ceramic sintered body according to claim 1, wherein the ceramic base material is a non-oxide ceramic such as silicon nitride or sialon. 5. The heat treatment is performed in a nitriding atmosphere at a temperature of 1750-19.
The method for producing a ceramic sintered body according to claim 4, which is carried out at 50 ° C. and under 9.5 atm. 6. The ceramic according to claim 1, wherein the ceramic reinforcing material is at least one of silicon carbide granular particles, silicon carbide plate-like particles and silicon carbide whiskers. Manufacturing method of sintered body.