JP2835618B2 - Method for producing whisker reinforced ceramic sintered body - Google Patents

Description

The present invention relates to a method for producing a high-density whisker-reinforced ceramic sintered body containing ceramic whiskers.

More specifically, the present invention relates to a method for easily and inexpensively producing a whisker-reinforced composite ceramic sintered body having high density, high strength, and high toughness suitable as a ceramic material for a structure such as a cutting tool. It is.

[Related Art] In recent years, ceramic materials are expected as new structural materials due to their excellent heat resistance, wear resistance, and chemical stability.

Among them, particularly, its application as a material for high-temperature structures such as gas turbines and automobile engine members attracts attention, and research and development in this field are active.

[Problem to be Solved by the Invention] The conventional technology has the following problems.

One of them is that sintering of the target material is extremely difficult, which reflects the excellent mechanical properties of the target material at high temperatures.

Another is that the processing of the sintered material is difficult.

This difficulty in processing also reflects the high strength and hardness of the target material, and is a problem that cannot be handled separately from the properties of the material.

Another problem, which is also due to the inherent properties of the ceramic material, is that it is brittle, is prone to sudden breakdown, and has low reliability as a material.

Research on overcoming the difficulty of sintering of powders of materials aimed at high-temperature structures has been made more vigorously than before, mainly called sintering aids that have a role to help sintering in raw material powders The method of adding the second phase has been adopted.

However, although these sintering aids generate a small amount of liquid phase during sintering and assist sintering, they have a problem of deteriorating the high-temperature strength of the sintered body, which is not preferable.

At present, improvement of starting material powders and search for new sintering methods are being continued.

Secondly, the difficulty in processing of ceramic materials stems from their excellent mechanical properties.

Although ceramic materials are generally brittle, they are often high in strength, high in hardness and difficult to process.

Recently, a high-purity, high-hardness diamond sintered body has also been developed, and cutting using this has been attempted, but satisfactory results in terms of cutting performance and processing cost have not yet been obtained.

At present, it is mainly processed by an expensive diamond grindstone, which contributes to high processing cost.

As described above, ceramic powder intended for high-temperature structural materials is generally difficult to sinter, and a method is employed in which sintering is performed while applying pressure even when an auxiliary agent is used.

This method is suitable for sintering a material having a simple shape such as a flat plate or a column, but is not suitable for sintering a material having a complicated shape.

For this reason, forming an actual member from a material manufactured by this method requires a large machining allowance and is not only inefficient, but also unusually increases the processing cost.

Therefore, in order to reduce the processing cost, which accounts for a large proportion of the product cost, it is strongly desired to develop a technology for manufacturing a sintered body as close as possible to the final part shape.

The brittleness of a ceramic material is essentially related to the mode of chemical bonding of its constituent atoms. Many attempts have been made to improve this fragility, with some success.

However, the characteristics required of materials are becoming increasingly strict, and new material design and development are indispensable to respond to them.

One method of strengthening the ceramic material is to combine it with a metal component capable of plastic deformation, and the other is to use a mixture of a second ceramic phase that increases or disperses the energy of fracture. This is a dispersion strengthening method. The former method of compounding with a metal component certainly improves the brittleness of the material.

However, metal has a large decrease in strength at high temperatures, and materials obtained by this method cannot be used as high-temperature structural materials.

On the other hand, in the case of the ceramic-ceramic composite, there is no fear of such deterioration, and this is a preferable method for the structure of the high-temperature structural material.

Among them, especially, the whisker strengthening method of dispersing high strength and high elasticity ceramic whiskers in a ceramic material has a remarkable effect of compounding, and is attracting much attention as one of the ceramic toughness improving methods.

For example, U.S. Pat. No. 4,543,345 describes an alumina sintered body in which silicon carbide (hereinafter referred to as SiC) whiskers are dispersed in alumina fine powder and a method for producing the same.

The patent discloses that 20% by volume SiC whiskers are dispersed in alumina to increase the fracture toughness (Kic value). It is stated that the effect of improving the toughness was remarkable.

In this method, a method is employed in which SiC whiskers are uniformly mixed with fine alumina powder, and the compact is sintered at a temperature of 1600 to 1950 ° C. while being pressed at a pressure of 27 MPa to 70 MPa, followed by sintering by a hot press method.

Such a whisker reinforced ceramic material is manufactured using a powder sintering method in the process. In this method, it is preferable that the density of the compact before sintering is as high as possible from the viewpoint of uniform sintering in consideration of shrinkage and reduction in processing cost of the sintered compact.

However, in the molding of ceramic powder mixed with whiskers, the dispersed high-strength, high-elastic whiskers impede the filling of ceramic powder particles. There is a problem that can not be.

This phenomenon is the same even in the heating stage in sintering, which inhibits the shrinkage of the ceramic powder as the matrix and makes it difficult to make the ceramic powder dense.

Therefore, at present, sintering of this type of material powder without using pressure is extremely difficult, and a hot press method using high temperature and pressure is indispensable to obtain a dense and high strength material.

It is effective to use a high pressure for densification of the ceramic powder, but the upper limit is several tens MPa due to the relationship with the strength of the hot press mold at high temperatures. For this reason, a method of raising the sintering temperature can be considered, but this temperature also has the following two restrictions.

One is that the temperature of the whisker is low enough not to cause a chemical reaction between the whisker and the ceramic matrix in order to exert the effect of the dispersion strengthening. The temperature and the temperature do not cause the occurrence.

Since these temperature conditions are not satisfied, there is a problem that the temperature range in which the densification can be achieved is considerably narrow in general ceramic materials.

In addition, for this reason, there is a defect in quality control that it is difficult to obtain a sintered body having constant characteristics under optimum conditions.

In addition, as described above, in the conventional manufacturing method, a pressure of several tens of MPa is indispensable in order to promote the subsequent densification,
For this purpose, a hot press method had to be used.

In this method, simple shapes can be manufactured relatively easily, but it is extremely difficult to directly sinter complicated shapes such as turbine blades and bolts / nuts in a system close to those shapes.

There has been no other method to produce such a complex-shaped part except for processing the pellet-shaped or columnar sintered body mainly by grinding using a diamond grindstone and taking a long time.

As a result, the processing cost can account for more than 50% of the product cost, which leads to a further increase in the cost of whisker-reinforced ceramic materials, which hinders the widespread use of such excellent materials. Was.

The present invention has been made in view of the above circumstances, and while improving the deficiencies of the conventional manufacturing method as described above while maintaining the excellent characteristics of the whisker reinforced ceramic material, the present invention has been applied to cutting tools and the like. It is an object of the present invention to provide a method for producing a whisker-reinforced ceramic sintered body having high density, high strength, and high toughness suitable as various structural materials.

[Means for Solving the Problems] The present inventors have intensively studied to develop a method of manufacturing a whisker-reinforced ceramics sintered body using simpler devices and means.

As a result, first, the starting material powder obtained by uniformly mixing and dispersing the ceramic whiskers in the ceramic powder serving as the matrix was subjected to impact compression to obtain a molded body having a relative density of 90% or more having a strength capable of being machined. Then, this compact is cut into the required material shape in consideration of sintering shrinkage, and this processed material, that is, the compact is sintered without using pressure, so that high-density whiskers extremely close to the final shape are obtained. We found that a reinforced ceramic sintered body could be obtained,
The present invention has been made.

That is, the present invention provides a method for producing a whisker-reinforced ceramic sintered body containing 10 to 50% by volume of a ceramic whisker, wherein the ceramic whisker is uniformly dispersed and mixed in a ceramic powder, and the mixed powder is formed into a molding die. A whisker-reinforced ceramic, characterized in that a powder compact having a relative density of 90% or more (porosity of 10% or less) is formed by filling and impact-compressing the mixed powder, and then sintered at a temperature of 1400 to 2000 ° C. Provided is a method for manufacturing a sintered body.

In this case, the ceramic powder may be made of at least one of alumina powder, silicon carbide powder, silicon nitride powder, boron powder, boron carbide powder, and aluminum nitride powder, and the ceramic whisker may be an alumina whisker, SiC whisker, silicon nitride (Si ₃ N ₄ )
It can also consist of at least one kind of whisker.

In the case of an ordinary powder molding method using a mold, it is difficult to increase the density of a ceramic powder obtained by uniformly mixing and dispersing ceramic whiskers as compared with the case of using a single ceramic powder for the above-described reason.

When a ceramic powder containing 20% by volume SiC whiskers is molded at about 200 MPa, the density of the compact that can be reached is at most about 55% (45% pores) of the true density.

Therefore, in this case, in order to obtain a dense sintered body, it is necessary to densify at least the remaining 45% during sintering.

However, in practice, as described above, densification during sintering is also hindered by dispersed ceramic whiskers, so a method of slowly densifying while applying pressure at a higher temperature than in the case of ceramic powder is used. Taken.

However, under a normal pressure of several tens of MPa, sufficient densification does not occur, and in this case, a method of adding a small amount of an auxiliary agent that assists sintering is used.

The sintering aid here is also not preferable because it causes a reduction in the high-temperature strength of the obtained sintered body.

One way to solve the above difficulties, including the problem of pressurization, is to use static and dynamic ultra-high pressure sintering technology that can use high pressures of several GPa in order to increase the density. The other is a method in which a high-density compact is first formed by using the ultrahigh-pressure technology, and the compact is sintered without pressure.

Among the former methods, the method using the static ultra-high pressure technique has the disadvantage that the required equipment is large-scale and expensive, and the driving operation is difficult.

On the other hand, the dynamic method is effective for densification and sintering of the powder, but is not practical because there is a problem that large and small cracks are formed in the obtained sintered body.

Further, the point common to these two methods is that although the densification is easy, it is extremely difficult to produce a sintered body having a complicated shape.

For this reason, the amount of processing to make it the final part increases,
As a result, the cost is high, and it is desired to solve the problems of the conventional method.

On the other hand, in the latter method, before the main sintering, the starting material is formed into a high-density compact having a strength that can be cut, and then processed into the required shape, and then subjected to final sintering. The amount of processing when finishing to a minimum can be minimized. Although the latter method can use the static high-pressure technique, this method is not practical because of the above-mentioned problems.

According to the present invention, a whisker-containing ceramic powder is first formed at a high density by dynamic ultra-high pressure, that is, impact compression,
The compact is cut and main-sintered to provide an inexpensive, high-density,
An object is to obtain a whisker-reinforced ceramic sintered body having high strength and high toughness.

It is also possible to sinter the powder at the same time as densification by the impact compression method, but this requires high pressure and temperature, and the sintering obtained by the impact compression treatment under such conditions Many cracks occur in the body.

However, it is empirically known that cracking is unlikely to occur at a pressure level that does not reach sintering but merely causes densification of the powder.

The present invention seeks to take advantage of such trends.

A compact body can be made by utilizing the impact pressure instantaneously generated due to the explosion of an explosive or the collision of an object flying at high speed.

By this method, Si which is difficult to densify by ordinary
High-strength ceramic powders such as C and Si ₃ N ₄ can be relatively easily densified.

One of the characteristics of shock compression is that it can be used in a short time of 10 ^-6 seconds.
It is capable of generating a high pressure of GPa to several tens of GPa.
% Or more.

The temperature under impact compression can be adjusted by the pressure generally used, provided that the initial powder molding density is the same.

On the other hand, if the pressure is constant, the pressure is determined by the molding density of the powder.

In order to obtain a uniform, high-density compact without cracking by the impact compression method, the impact temperature must be low enough not to cause sintering of the powder, and the pressure to be used is limited to the obtained compact. Is preferably as low as possible from the viewpoint of reducing the residual strain of the steel.

[Operation] The effect will be described.

Embodiments of the present invention will be described with reference to the drawings.

Methods for obtaining a high-density molded body by impact compression include a method using explosives and a method of colliding a high-speed flying object fired by high-pressure gas.

When using any of these methods, it is important to collect the sample as one lump without scattering the sample.

 Fortunately, this sample collection technology is making progress.

In FIG. 1, reference numeral 1 denotes a flat impact compression device which can be used in the method of the present invention, and comprises a lower portion 2 and an upper portion 3.

Reference numeral 2A denotes a sample container having a sample chamber 2B for filling a mixed powder 4 obtained by uniformly mixing ceramic powder and ceramic whiskers.

An iron momentum trap 2C for facilitating the recovery of the sample container 2A after the shock treatment is disposed outside thereof, and an iron momentum trap 2D is similarly disposed therebelow.

The sample container 2A is composed of a bottom plate 2A1 and a lid 2A2 having a U-shaped cross section that is detachably fitted to the bottom plate 2A1 from above.

The momentum trap 2C absorbs the momentum mainly in the lateral direction of the sample container, and the momentum trap 2D absorbs the momentum in the downward direction of the sample container, and as a result, facilitates the collection of the sample after the shock treatment. Things.

Although it is not easy to mix the whiskers in the ceramic powder as much as possible with uniformity, it is not easy to mix them.However, mix each component separately in a wet ball mill or stirrer, mix and then mix again with a ball mill or stirrer. By the mixing method, whisker breakage can be reduced and relatively uniform mixing can be achieved.

The dispersion state of the ceramic whiskers in the matrix greatly affects the characteristics of the obtained sintered body and is important.

In filling the mixed powder into the sample container 2A, it is desirable to fill the sample powder as densely as possible, and the relative density is preferably 40% or more.

Further, as the material of the sample container 2A, a wide range of materials can be selected depending on the impact treatment conditions required for molding the target material, but iron, copper, brass and stainless steel are suitable from the viewpoint of cost.

The upper part 3 of FIG. 1 is the explosive component of this device, but the conical explosive lens 3A is ignited at its apex by a primer 3B, and the combustion at the explosive lens 3A is propagated downward in a plane. .

In addition, the planar combustion is propagated to the explosive 3C below, and the explosive causes bottom combustion and propagates downward, and the detonation impact pressure generated by this combustion causes the lower metal plate, the flying plate 3D
Is accelerated at a high speed and collides with the lower sample container 2A.

This collision generates a plane shock wave in the sample container, which propagates further to the mixed powder 4, and the mixed powder is shock-compressed and formed.

The pressure and temperature generated in the portion of the mixed powder by the passage of the shock wave can be controlled mainly by the amount of explosive used and the filling rate of the mixed powder, and the flying time as shown in FIG. In case, it can be changed by the thickness, but 3mm
The pressure duration when the steel plate of the above was made to collide with the sample container at about 2 km / s is about 1.5 × 10 ^-6 seconds, which is extremely short.

Further, in the method as shown in FIG. 1, a pressure up to 50 GPa can be generated relatively easily in the sample portion.

FIG. 2 is a longitudinal sectional view showing one embodiment of the cylindrical impact compression device 5 which can be used in the method of the present invention.

Reference numeral 6 denotes an explosive container, which comprises an outer cylinder 6A, an upper plate 6B and a lower plate 6C arranged above and below the outer cylinder.

Reference numeral 7 denotes a cylindrical sample container coaxially located at the center of the explosive container 6, and upper and lower plugs 7A and 7B are provided above and below it.

Reference numeral 4 denotes a mixed powder filled in the cylindrical sample container 7.

This figure shows a state in which the explosive 3C is disposed in contact with the cylindrical sample container 7, and the explosive 3C is detonated by the primer 3B.

The detonation wave propagates downward, and the accompanying detonation shock wave first compresses the inner cylindrical sample container 7 in the axial direction, and then similarly compresses the mixed powder 4 in the inner side. Is done.

The pressure generated at the portion of the mixed powder 4 can be adjusted by the type and amount of the explosive used.

Here, the outer cylinder 6A of the cylindrical sample container 7 and the explosive container 6
Metal, paper, wood, and plastic can be used as the material of.

The conical plug 7A located above the cylindrical sample container 7 can be made of metal or wood.
Before the detonation wave exploded in 3B and the detonation wave spreading in a spherical shape in the explosive 3C reaches the cylindrical sample container 7, the detonation wave spreading in the spherical shape serves to arrange the detonation wave into a planar detonation wave. It is indispensable for uniformly compressing the sample by impact.

In the method of the present invention, the whisker-containing ceramic molded body is heated to 1400 to 2000 ° C. without pressure to obtain a sintered body having a true density, but for this purpose and
In order to process the compact before the main sintering, the relative density of the compact is required to be 90% or more.

Although it depends on the type of ceramic used as the matrix and the mixing ratio of the whiskers, in the compact having a relative density of 90% or less, the denseness does not sufficiently advance even with the present sintered body, and a high-strength sintered body cannot be obtained. .

Further, the strength of such a molded product is not sufficiently high, and cutting is difficult. 10 ~ 50% by volume of ceramic whisker
The impact pressure required to densify the contained ceramic powder to a relative density of 90% or more is determined by the physical properties of the target ceramic powder and whiskers, and the conditions must be determined experimentally for each material combination. It is necessary to determine

If the degree of impact pressure is in an appropriate range, the relative density
When it is 90% or more, a uniform molded body without cracks can be obtained.

However, if the processing pressure exceeds the limit pressure determined by the combination of each material, seizure between powder particles, that is, intergranular bonding due to sintering occurs, and as a result, large and small cracks occur in the recovered compact. Is not preferred.

The range of the impact pressure used in the method of the present invention is limited to a moderate pressure at which no sintering occurs during the impact treatment or no grain growth occurs even if it occurs.

On the other hand, if the pressure is too low, the mixed powder will have a relative density of 90%
Unable to densify to the above, as described above, the strength of the obtained molded body is also low, not only can not be cut, but also densification does not progress by the main sintering, resulting in high strength at low cost A whisker-reinforced ceramic sintered body having toughness cannot be obtained.

Hereinafter, the present invention will be described in more detail with reference to examples.

(Example) Alumina powder having an average particle diameter of 1 μm and an average whisker diameter of 0.
5μm, average length 30μm SiC whisker 4: 1 by volume ratio
First, each powder was separately added to water, and then ball-milled so as to be in a slurry state, then mixed, and then ball-milled again.

After the powder mixed with the ball mill was dried, it was subjected to vacuum degassing at 600 ° C. to obtain a mixed powder of this example.

This mixed powder was subjected to impact treatment using the flat impact compression apparatus shown in FIG.

Here, the mixed powder is placed in the sample chamber 2B shown in FIG.
Filled to 53%.

Stainless steel is used as the material for the sample chamber 2B,
2B had a diameter of 25 mm and a height of 10 mm.

Explosive 3C explosion speed 7.2km / s manufactured by Dupont
A 3.2 mm thick iron plate was used as a flying plate using a sheet.

Here, a molding test was performed at each flying plate speed shown in Table 1.

After the shock treatment, the sample container was recovered, the stainless steel portion outside the sample was removed by cutting, the sample was taken out, and the upper and lower surfaces were lightly polished with abrasive paper, and the appearance was observed.

The bulk densities of the recovered molded articles were measured by the Archimedes method using water, and the relative densities of the molded articles were calculated.

The cutting test of each compact was performed at a peripheral speed of about 35 m / min using a diamond sintered body as a cutting tool, and cutting was possible due to the occurrence of cracks and chipping at that time.
Judgment was impossible.

Next, the compacts were heated at a temperature of 1500 ° C. using a vacuum furnace.
Sintering was performed at 1700 ° C. and 1900 ° C. for 1 hour, and the relative density and Kic of the obtained sintered body were measured.

The Kic value is determined by the Vickers indentation method assuming a load of 5 kg.
It was calculated based on the length of cracks generated from all sides of the indentation at that time.

Table 1 summarizes the results obtained for the samples at each flying plate speed. At a flying plate speed of 0.3 km / s, the appearance of the recovered compact was good without cracking, but the density of the compact was low, and in the cutting test, it was broken at the jig for processing. Oops.

At this level of compact density, as shown in Table 1, no significant densification was observed even after the subsequent heat treatment at 1500 to 1900 ° C.

On the other hand, when the flying plate speed was increased to 1.8 km / s, the relative density of the collected compact certainly reached 96%, but cracks occurred. Broken into small pieces.

Observation of the fracture surface of the cracked small piece showed that alumina sintering was partially caused by the impact treatment alone.

The relative densities of the compacts obtained at the flying plate speed of 0.6 to 1.4 km / s were 90 to 95%, and none of them had cracks and had cutting strength.

In addition, the compacts obtained by sintering these compacts at 1700 to 1900 ° C have been sufficiently densified, and the Kic value is also high. It showed a high value.

Example 2 Si ₃ N ₄ having an average particle diameter of 0.6 μm and an average whisker diameter of 3 μm,
Alumina whiskers having an average length of 30 μm were separately weighed so as to have a volume ratio of 2: 1, and the respective components were mixed by the same method and procedure as in Example 1.

The obtained powder was subjected to a vacuum degassing treatment to obtain a mixed powder of this example. This mixed powder was subjected to impact treatment in the same manner as in Example 1 using the flat impact compression device shown in FIG.

Here, a forming test was performed at a flying plate speed of 0.1 to 1.6 km / s shown in Table 2.

The sample after the impact treatment was recovered by the same method as in Example 1, and after observing the appearance and measuring the density, a cutting test was performed.

Next, each of the obtained compacts was placed in a nitrogen atmosphere of 1 atm.
Sintering was carried out at 00 ° C, 1600 ° C, and 1800 ° C for 1 hour. The relative density and Kic value of the obtained sintered body were measured.

Table 2 shows the results for the samples obtained at each flying plate speed.

The molded product obtained at a flying plate speed of 0.1 km / s was good without any apparent cracking, but had a low relative density and was not able to be cut. In addition, this sample showed only a slight densification by heat treatment at 1400 to 1800 ° C.

On the other hand, the sample obtained at a flying plate speed of 1.6 km / s had already broken into small pieces at the time of recovery.

The relative density measured on the small piece reached 99%, indicating that sintering had progressed considerably from the state of the fracture surface.

At a flying plate speed of 0.4 to 1.2 km / s, a solid compact with a relative density of 93 to 98% was obtained, and all could be cut.

In addition, all treatments at 1400 to 1800 ° C show excellent sinterability, Up to a high Kic value.

(Example 3) SiC powder having an average particle diameter of 3 μm and an average whisker diameter of 1 μm
m, Si ₃ N ₄ whiskers having an average length of 40 μm were weighed so as to have a volume ratio of 5: 1, mixed, dried and vacuum degassed by the same method and procedure as in Example 1. Was obtained.

This mixed powder was subjected to impact treatment using a cylindrical impact compression device shown in FIG.

Here, the cylindrical sample container 7 has an inner diameter of 20 mm and an outer diameter of 25 mm.
The length of the sample part was 100 mm using an iron pipe of mm.

In addition, an ampho explosive is used as explosive 3C, and its thickness is reduced.
Molding tests were performed for 10 mm, 30 mm, 60 mm, and 100 mm.

After the shock treatment, the cylindrical sample container was recovered, and the container was divided into two pieces vertically and the sample inside was taken out.

After examining the overall appearance in this state, a cylindrical sample having a thickness of 5 mm was cut out from the central portion in the axial direction with a diamond cutter, and the density was measured.

Further, in the cutting test of the molded body, it was determined whether machining was possible or not by cutting one end of the molded body using diamond as in Example 1.

Next, the molded body was placed in a nitrogen atmosphere at 1 atm.
The temperature was maintained at 2000 ° C. for 1 hour to obtain a sintered body.

The relative densities and Kic values of these sintered bodies were measured in the same manner as in Example 1.

The results obtained for the samples at each explosive thickness are summarized in Table 3.

No cracks were apparently observed in the molded product obtained with an explosive thickness of 10 mm, but the relative density was as low as 82% and cutting was impossible.

In addition, the molded article obtained with an explosive thickness of 100 mm had several layered cracks, and could not be collected as a lump of molded article.

Observation of the cracked surface showed that this sample had already been sintered.

Molded articles obtained with explosive thicknesses of 30 mm and 60 mm have a relative density of 90
% And 95%, and were uniformly shrunk, and cutting was possible.

The samples obtained by sintering these samples at 1800 ° C and 2000 ° C show high relative density, Showed high values.

Example 4 Boron powder having a particle diameter of 1 μm or less and boron carbide powder having an average particle diameter of 3 μm were mixed at a volume ratio of 1: 1 to prepare a ceramic powder for a matrix.

A SiC whisker similar to the whisker used in Example 1 was weighed to 10% by volume of this ceramic powder, and mixed, dried and vacuum degassed by the same method and procedure as in Example 1. A mixed powder of this example was obtained. This mixed powder was prepared using the same apparatus as in Example 1 to obtain a flying plate speed of 0.5.
Forming tests were performed at 6 km / s and 1.0 km / s.

The relative densities of the compacts obtained at 0.6 km / s and 1.0 km / s were 9
They were 1% and 93%, and were uniform without appearance cracks.

When a cutting test was performed on these compacts in the same manner as in Example 1, all of the compacts had a strength capable of cutting.

The relative densities of the sintered bodies obtained by holding these compacts at 1700 ° C and 1900 ° C for 1 hour in vacuum reach 98% for both the samples obtained at 0.6 km / s and 1.0 km / s, and the Kic value is Each Met.

(Example 5) Aluminum nitride powder having a particle size of 10 µm or less and an average particle size of 3
μm Si ₃ N ₄ powder was mixed at a volume ratio of 3: 2 to prepare a ceramic powder for a matrix.

The same SiC whiskers as the whiskers used in Examples 1 and 2 and Si ₃ were added so that the volume percentage of this ceramic powder was 50%.
N ₄ whiskers were weighed 1: 1 and mixed, dried and vacuum degassed by the same method and procedure as in Example 1 to obtain a mixed powder of this example.

Using the same apparatus as in Example 1, a molding test was performed on the mixed powder at a flying plate speed of 0.5 km / s and 1.0 km / s.

The relative densities of the compacts obtained at the flying plate speeds of 0.5 km / s and 1.0 km / s were as high as 93% and 95%, respectively, and were uniform without cracks.

 In addition, all could be cut.

Next, these samples were placed in a nitrogen atmosphere at 1 atm.
And 1850 ° C for 1 hour for sintering. 0.5km / s, 1.0km / s
The relative densities of the sintered compacts from the compacts obtained by the impact treatment are 99% and 100%, respectively, and the Kic values are respectively Met.

[Effects of the Invention] As described above, according to the method of the present invention, a ceramic powder containing 10 to 50% by volume of ceramic whiskers can be relatively easily densified to a relative density of 90% or more by impact compression, and cutting is possible. It is possible to obtain a molded body having a certain degree of strength.

The ceramic powder particles constituting the high-density compact obtained by this impact treatment are activated by the impact treatment,
It is easy to sinter, and a uniform and strong sintered body can be easily obtained by sintering without using pressure.

Further, in the method for producing a whisker-reinforced ceramic sintered body according to the method of the present invention, since the shrinkage in the sintering step of the high-density compact is extremely small, the processing cost after sintering can be significantly reduced, and its industrial significance Is big.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a flat impact compression apparatus applicable to the method for producing a whisker-reinforced ceramic sintered body of the present invention, and FIG. 2 is a longitudinal sectional view of a cylindrical impact compression apparatus. 1 ... Flat impact compression device, 2 ... Lower part, 2A ... Sample container, 2B ... Sample chamber, 2C, 2D ... Momentum trap, 3 ... Upper part, 3A ... Explosive lens, 3B ... Detonator, 3C explosive, 3D flying board, 4 mixed powder, 5 cylinder impact compression device, 6 explosive container, 6A outer cylinder, 6B upper plate, 6C lower plate , 7 ... Cylindrical sample container, 7A, 7B ... Plug.

Claims (3)

(57) [Claims] 1. A ceramic whisker containing 10 to 50% by volume.
In a method for producing a whisker-reinforced ceramic sintered body containing, ceramic whiskers are uniformly dispersed in ceramic powder, mixed, and the mixed powder is filled in a mold,
The mixed powder was subjected to impact compression to form a powder compact having a relative density of 90% or more (porosity of 10% or less).
A method for producing a whisker-reinforced ceramic sintered body, comprising sintering at a temperature of 00 ° C. 2. The method for producing a whisker-reinforced ceramic sintered body according to claim 1, wherein said ceramic whisker comprises at least one of alumina whisker, silicon carbide whisker, and silicon nitride whisker. 3. The method according to claim 1, wherein said ceramic powder is alumina powder, silicon carbide powder, silicon nitride powder, boron powder, boron carbide powder,
The method for producing a whisker-reinforced ceramic sintered body according to claim 1, comprising at least one kind of aluminum nitride powder.