JPS5941954B2 - Manufacturing method of high-density ceramic sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of a high-density ceramic sintered body, and more specifically, the present invention relates to the production of a high-density ceramic sintered body by sintering a porous ceramic body under high temperature isostatic pressure (hereinafter referred to as HIP). Concerning a new manufacturing method for obtaining.

Recently, as ceramics are the only materials used in harsh environments such as extremely high temperatures, high vacuums, large stresses, and high corrosivity, research and development on various ceramic materials that are difficult to sinter have been actively conducted.

In particular, in order to improve the thermal efficiency of various heat engines for the purpose of energy conservation, it is required to dramatically increase the inlet temperature of the heat engine, and efficient high-temperature structural materials to prevent heat loss have been studied. There is.

However, conventional heat-resistant alloys cannot provide sufficient thermal and mechanical strength for materials used under such high temperatures, and ceramics, which are abundantly produced in terms of resources, have great expectations as metal substitute materials. This is the current situation.

Furthermore, since such ceramic materials have excellent wear resistance, they are attracting attention as materials for various die-casting shapes, nozzles, and the like.

In general, it is said that hot pressing is preferable for manufacturing such ceramic sintered bodies, but in this method, a ceramic material is hot pressed in a mold with a relatively simple shape. For example, it is difficult to mold parts with complex shapes such as gas turbine impellers or mechanical gears, and since the mold materials used are made of graphite or alumina, hot pressing pressure is limited at best. The pressure is several hundred atmospheres, which is a major technical constraint for manufacturing various ceramic sintered products.

However, recently, in ceramic molding, argon gas (Ar gas), A HIP method has been proposed in which high-temperature, high-pressure gas medium such as nitrogen gas (N2 gas) is used to sinter to increase the density.

That is, in the HIP method, a ceramic molded body or pre-sintered body is placed in a high-pressure container capable of applying high temperature and high pressure.
A gas pressure of 0 to 3,000 atmospheres and a temperature of 1,300 to 2,500°C are applied, and ceramics are pressure-sintered more uniformly by the action of high pressure and temperature.

Since the HIP method uses Ar gas or N2 gas as a pressure medium, it is essential that the surface of the preformed body or presintered body be gas impermeable.

Therefore, when using the HIP method on ceramics,
The preformed body or presintered body is densified to a density of 93% or higher, preferably 95% or higher, and is made gas impermeable, and the HIP method is secondarily applied to the molded body to further increase the density. The density of the preformed body or presintered body is 9307
0 or less, the capsule is sealed in a gas-impermeable capsule, and the capsule is densified by applying high-temperature, high-pressure gas pressure from the outside of the capsule. There are known methods such as coating and sealing with a substance and HIPing to densify.

However, all of these methods have drawbacks.

That is, in the method (2) above, it is necessary to sinter the ceramic material twice at a relatively high temperature, and as a result, ceramic molding becomes quite expensive, and the utility value is limited only to ceramic materials with high added value. It's just being discovered.

In addition, method (1) allows sintering to be performed with a single high-temperature treatment, so it is possible to sinter the ceramic molded body to a higher density at a lower cost than method (2). It is difficult to obtain a sintered body having a complicated shape by the HIP process.

In this regard, the method (2) above is the most promising method because it allows the HIP treatment to be performed by covering the sealing material in a state close to the final shape.

Pyrex glass, quartz glass, and Vycor glass (high silicate glass) are known as sealing materials that can form a high-pressure gas-impermeable membrane.

However, as mentioned above, many ceramic materials that are effective as heat engines and highly wear-resistant materials require a sintering temperature of 1500°C or higher, and therefore, all sealants known to date are unsuitable. be.

For example, Pyrex glass has an alkali content of about 4, so it has a low viscosity at high temperatures and is easy to coat on ceramic porous bodies, but the glass tends to penetrate into the porous body after ceramic firing after HIP treatment. It has the disadvantage that the function of the body is significantly inhibited.

Furthermore, quartz glass and Vycor glass have very high viscosity even at high temperatures and do not have the drawbacks of Pyrex glass, but high temperatures of 1500°C or higher are required to form a glass film, and the glass Since crystallization progresses and devitrification occurs at 1300° C., it has the disadvantage that it is difficult to coat gas-impermeable quartz glass and Vycor glass films that can be subjected to HIP treatment.

In view of the current situation, the inventors of the present invention have conducted extensive research to develop a new sealing material that does not have the drawbacks of conventional sealing materials, and have found that highly silicic acid porous glass or its nitride glass is desirable. discovered that it can be used as a sealing material.

The present invention was completed based on this knowledge.

That is, the present invention provides a method for manufacturing a high-density ceramic sintered body by covering a preformed or presintered ceramic porous body with a sealing material and sintering it under high temperature isostatic pressure.
The present invention relates to a method for manufacturing a high-density ceramic sintered body, characterized in that a high-silicate porous glass or a nitride glass thereof is used as a sealing material.

The high silicic acid porous glass used in the present invention is 110
It vitrifies at a relatively low temperature of 0 to 1200℃, and once it becomes non-porous, it exhibits a high viscosity equal to or higher than quartz, making it possible to easily form a gas-impermeable film on the surface of a porous ceramic material. Moreover, there is no fear that glass will enter the inside of the ceramic porous body and significantly impede the function of the ceramic sintered body after HIP treatment.

Furthermore, according to the method of the present invention, a high-density sintered body can be easily obtained by HIPing a ceramic body in a state close to the final molded product shape.

In the present invention, the preformed or presintered ceramic porous body is not specified in any way as long as the base material is an oxide, carbide, nitride, or boride of an n, I, or TV group element. Rather, for example, it is molded into a predetermined shape by a generally known molding method, that is, mold molding, rubber press molding, insertion molding, injection molding, etc., or it is molded into a predetermined shape by a conventional hot pressing method, normal pressure sintering method, For nitrides and carbides, porous ceramic compacts obtained by preliminary sintering using a reaction sintering method or the like can be widely used.

Further, in the present invention, there is no problem with the addition of various binders and the pre-mixing of known additives as sintering aids, which are added during these molding steps as necessary.

Furthermore, the ceramic porous body used in the present invention has a density of 9
A preform having a density of 3 or less may be used, and a high-density preform having a density higher than this can be subjected to HIP treatment without using the method of the present invention.

The method of the present invention can be applied to any ceramic porous body with a density of 93 coefficients or less that can maintain strength to prevent breakage during subsequent processing, but even if it is a ceramic porous body with a density of 93 coefficients or higher. It is of course possible to apply the method of the invention.

The highly silicate porous glass used in the present invention is produced by heat-treating borosilicate glass to form Na2O, B2O3 phases and 5i0
Separate into two phases, soluble Na 20 and B 203
It is a glass made by eluting the components with acid.

The chemical composition of this glass is 810294-98%.

B2030.5~5%, A72030~2%, N
a200.01%.

Its pore size is 40-2000. Pore volume 0.3-1
cc/g, pore surface area of 50 to 6 oom/I, and is a highly reactive glass material with a large specific surface.

When this material is heated to 1000 to 1200°C, it becomes non-porous and becomes a uniform glass.

In the present invention, the glass is applied to the surface of the ceramic preform or the presintered ceramic porous body.

The coating method may include making a slurry in a solvent such as water or alcohol, dipping it in the slurry, spraying, brushing, or other methods.

At this time, cellulose acetic acid is added to the slurry. By adding 0.1 to 2 parts of various glues such as PVA, the properties after coating can be improved.

The thickness to be applied is about 10μ or more, preferably 10μ
It is preferable to apply a coating of 0μ or more, but it is not necessary to make it thicker than several mr/L.

The ceramic porous body coated with glass powder may have a complex shape, and is usually heated at temperatures of 900°C or higher, preferably 10°C.
If fired at 00 to 1200°C, a gas-impermeable glass membrane seal can be formed on the surface of the ceramic porous body, allowing HIP treatment.

The atmosphere during the main firing may be any atmosphere, but firing in the air or an inert atmosphere will result in a highly silicic acid glass, and firing in a nitrogen atmosphere, an ammonia atmosphere, or a mixed atmosphere will result in the highly silicic acid porous glass. When glass becomes non-porous, it easily becomes nitride glass.

These glasses have a higher viscosity than quartz glass and Vycor glass, and the amount of glass that penetrates into the ceramic porous body is reduced, making it possible to seal only the surface layer with gas impermeability.

Quartz glass has low reactivity and is difficult to convert into nitride glass through the above treatment.

In addition, in the present invention, rather than applying a high silicic acid porous glass powder, the glass is nitrided in advance to form a powder as nitride glass, and the powder is applied to the surface of the ceramic porous body using the method described above and heat-treated. A similar HIP treatment is also possible by covering and sealing.

In addition, in the method of applying glass powder as a slurry and baking it to seal the gas-impermeable glass, it is possible to perform the glass coating and sintering treatment at the same time in a HIP high-pressure container, making the process extremely simple. .

In addition, a ceramic porous body is buried in high silicic acid porous glass or nitride glass powder obtained by nitriding it.
It is also possible to use a method in which the porous body is hot-pressed at 00 to 1100° C. under a pressure that does not damage the porous body, and a gas-impermeable glass-coated seal is formed.

Table 1 below shows the softening points and high temperature viscosity of main glasses.

In the present invention, the firing conditions during HIP treatment are not particularly specific and can be appropriately selected within a wide range.
The HIP treatment is usually carried out at a temperature of 1300° C. or higher and a gas pressure of 500 to 3000 atm.

The glass-coated sealing material obtained by nitriding this highly silicic acid porous glass does not devitrify even under HIP treatment conditions, has a viscosity higher than that of quartz glass (which devitrifies at temperatures above 1300°C), and is sintered at high temperatures. It is an optimal sealing material for HIP processing of nitride-based, carbide-based, and ferride-based ceramic materials that require bonding. Since it is possible to cover and seal the HIP sintered body in a state close to the final molded shape, it is possible to obtain a HIP sintered body in a state close to the final molded shape.

Examples and comparative examples are listed below.

Example 1 ¥20 for si3N4 powder (LC-10 manufactured by Stark)
8 parts by weight of 3-A1203 type sintering aid were added, and after thorough mixing, rubber press molding was carried out at 3000 atm.

The bulk density thus obtained was 63% and the porosity was 37%.

This is a high silicic acid porous glass powder (pore volume Q, 3c
c/g, average pore diameter 150 g, pore surface area 180 mnia g, average particle size 0.1 mm) and cellulose acetate 1
% in a slurry made with an alcohol solution,
A coating film with a thickness of 1 mvt was applied to the surface.

After drying, it was treated with 12008C for 30 minutes in a flow of N2 gas (flow rate 50 cc/ml) through an ammonia bath.

The treated material was placed in a HIP device and subjected to HIP treatment according to the temperature increase schedule shown in FIG.

Final HIP conditions were 1800°C temperature, 60 minutes, 200°C
The Ar gas pressure is 0 atm.

The results obtained are shown in Table 2.

Comparative Example 1 A ceramic porous body under the conditions described in Example 1 above was coated with quartz glass powder slurry and heat treated at 1300° C. for 30 minutes.The material was then subjected to HIP treatment in the same manner as in Example 1.

The results are shown in Table 2. Table 2 shows that the obtained sintered body was not densified.

Example 2 SiC powder (manufactured by Fujimi +5ooo) was rubber press molded in the same manner as in Example 1 above.

The bulk density is 58.

A slurry made from highly silicic acid porous glass powder was applied to this using a brush, and after drying, it was processed at 1200°C in an atmosphere of N2 gas through an NH3 bath (flow rate 50cc/m1n). was sintered according to the HIP schedule shown in FIG.

The results are shown in Table 2.

In this table, quartz glass powder subjected to the same treatment is also listed.

Example 3 Same as Example 1 for si3N4 powder ￥203-A12
03 type auxiliary agent was added in an amount of 12 weight, and after rubber pressing, normal pressure sintering was performed at 1800° C. for 1 hour under 9.8 atmospheres of N2.

The compacted density was 91% relative density.

One is coated with high silicic acid porous glass powder and heat treated in the same manner as in Example 1, and the other is embedded in high silicic acid porous glass powder in a hot press mold. A glass-sealed product was prepared by applying a pressure of 100 kg/kg for 10 minutes at 1000°C.

This was performed using the same HIP processing schedule as in Example 1.
P was sintered.

The results are shown in Table 2. At the same time, HIP-treated sintered bodies without glass sealing were also shown.

Example 4 Z r C, Z r B (both manufactured by Cerac) 16000C 10 minutes 200 kg/cI? The relative densities of those hot press molded under the conditions of L are 77% and 83%, respectively.

Table 2 shows the results obtained by the same treatment as in Example 1.

[Brief explanation of drawings]

FIG. 1 shows the HIP firing schedule for Si3N4 ceramics, and FIG. 2 shows the HIP firing schedule for SiC ceramics.

Claims (1)

[Claims] 1 In a method of producing a high-density ceramic sintered body by covering a preformed or presintered ceramic porous body with a sealing material and sintering it under high temperature isostatic pressure, a high-silicate porous glass is used as the sealing material. Or a method for producing a high-density ceramic sintered body, characterized by using the nitride glass.