JPH0312370A - Production of whisker-reinforced ceramic sintered compact - Google Patents

Abstract

PURPOSE:To obtain a whisker-reinforced ceramic sintered compact having high density, high strength, and high toughness by uniformly dispersing ceramic whiskers into a ceramic powder, subjecting the resulting powder mixture to impact compression in a forming die, and then sintering the resulting powder green compact. CONSTITUTION:Ceramic whiskers are uniformly dispersed and mixed into a ceramic powder by 30-50vol.%. Subsequently, a forming die is filled with the resulting powder mixture and impact compression is performed, by which a green compact having a strength as high as to enable machining and also having >=90% relative density is prepared. The above green compact is machined into a required material shape in consideration of compression by sintering and then sintered at 1400-2000 deg.C without using pressure. By this method, the high- density whisker-reinforced ceramic sintered compact having a shape extremely close to the final shape can be obtained. This sintered compact is suitable for various structural materials, including cutting tools.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] 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 inexpensively and easily manufacturing a whisker-reinforced composite ceramic sintered body that has high density, high strength, and high toughness and is suitable as a structural ceramic material such as cutting tools. It is.

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

Among these, applications as materials for high-temperature structures such as gas turbines and automobile engine components are attracting particular attention, and research and development in this field is active.

[Problems to be Solved by the Invention] The conventional techniques described above have the following problems.

One is that the materials of interest are extremely difficult to sinter, reflecting their excellent mechanical properties at high temperatures.

Another reason is that the sintered material is difficult to process.

This difficulty in processing also reflects the high strength and hardness of the target material, and is an issue that cannot be treated separately from the properties of the material.

Another problem, which is also due to the inherent properties of ceramic materials, is that they are brittle, prone to sudden breakage, and have low reliability as a material.

Research has been actively conducted to overcome the difficulty of sintering of powders of materials that are self-damaged when used in high-temperature structures.
A method has been adopted in which a second phase called a sintering aid, which has the role of assisting sintering, is added to the raw material powder.

However, these sintering aids produce a small amount of liquid phase during sintering, which helps sintering, but has the problem of degrading the high temperature strength of the sintered body, which is not preferable.

Currently, efforts are being made to improve the starting material powder and search for new sintering methods.

Next, the difficult-to-process nature of ceramic materials stems from their excellent mechanical properties.

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

Recently, high-purity, high-hardness diamond sintered bodies have been developed, and cutting processes using these bodies have been attempted, but satisfactory results have not yet been obtained in terms of cutting performance and processing costs.

Currently, processing is mainly performed using expensive diamond grindstones, which contributes to high processing costs.

As mentioned above, ceramic powder intended for high-temperature structural materials is generally difficult to sinter, and even when an auxiliary agent is used, a method of sintering under pressure is used.

This method is suitable for sintering materials with simple shapes such as flat plates and cylinders, but is not suitable for sintering materials with complex shapes.

For this reason, when molding an actual member from a material manufactured by this method, the machining allowance is large, resulting in not only inefficiency but also an abnormally high machining cost.

Therefore, in order to reduce processing costs, which account for a large proportion of product costs, there is a strong desire to develop a technology for manufacturing sintered bodies as close to the final part shape as possible.

The fragility of ceramic materials is essentially related to the chemical bonding of the atoms that make up the material. Many attempts have been made to improve this fragility, and some results have been achieved.

However, the properties required of materials are becoming stricter by the minute, and new material design and development are essential to meet these requirements.

One method of strengthening ceramic materials is by compounding them with metallic components that have the ability to plastically deform, others by mixing a second ceramic phase that increases or disperses the energy of fracture. This is a distributed reinforcement method. The former method of compounding with metal components certainly improves the brittleness of the material.

However, the strength of metals decreases significantly at high temperatures, and materials produced by this method cannot be used as materials for high-temperature structures.

On the other hand, ceramic-ceramic composites do not have to worry about such deterioration and are a preferred method for producing materials for high-temperature structures.

Among these methods, the whisker strengthening method in which high-strength, high-elasticity ceramic whiskers are dispersed in a ceramic material has an extremely remarkable compounding effect, and is attracting a lot of attention as a method for improving the toughness of ceramics.

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

This patent states that by dispersing 20% by volume of SiC whiskers in alumina, the fracture toughness value (hereinafter referred to as KIc value) increased from 4.6'MPaJm to 9,000MPaJm, which had the effect of significantly improving toughness. That is stated.

In this method, fine-grained alumina powder is uniformly mixed with SiC whiskers, and the molded product is sintered by a hot press method in which the mixture is heated at 1600 to 1950° C. while being pressed at a pressure of 28 MPa to 70 MPa.

Such whisker-reinforced ceramic materials are manufactured using a powder sintering method. 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 of processing costs of the sintered compact.

However, when molding ceramic powder mixed with whiskers, the dispersed high-strength, high-elasticity whiskers inhibit the filling of the ceramic powder particles. The problem is that it can't be done.

Furthermore, this phenomenon also occurs during the heating stage of sintering, which inhibits the shrinkage of the ceramic powder that is the matrix, making it difficult to achieve densification.

Therefore, it is currently extremely difficult to sinter this type of material powder without using pressure, and a hot press method using high temperature and high pressure is essential to obtain a compact, high-strength material.

Although it is effective to use high pressure to densify ceramic powder, the pressure is limited to several tens of hlPa due to the strength of the hot press mold at high temperatures. For this reason, a method of increasing the sintering temperature may be considered, but this temperature also has the following two restrictions in this case.

One is that in order to exhibit the effect of dispersion strengthening, the temperature must be low enough that no chemical reaction occurs between the whiskers and the ceramic matrix, and the other is that
The temperature is such that one grain of the matrix does not undergo significant grain growth.

A problem with general ceramic materials is that the temperature range in which densification can be achieved while satisfying these temperature conditions is quite narrow.

Additionally, there was also a drawback in terms of quality control that it was difficult to obtain a sintered body with constant characteristics under optimal conditions.

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

With this method, products with simple shapes can be produced relatively easily, but it is extremely difficult to directly sinter products with complex shapes, such as turbine plates or bolts and nuts, into shapes close to those.

The only way to make parts with such complex shapes was to process pellet-like or cylindrical sintered bodies through time-consuming grinding, mainly using a diamond grindstone.

For this reason, the processing cost can account for more than 50% of the product cost, leading to further increases in the cost of whisker-reinforced ceramic materials and hindering the wider use of this type of superior material. Ta.

This invention was made in view of the above circumstances, and aims to improve the drawbacks of the conventional manufacturing method described above while maintaining the excellent properties of whisker-reinforced ceramic materials, and to improve the quality of cutting tools and other products. The purpose of the present invention is to provide a method for manufacturing whisker-reinforced ceramic sintered bodies that have high density, high strength, and high toughness and are suitable for various structural materials.

[Means for Solving the Problems] The present inventor has conducted extensive research with the aim of developing a method for manufacturing whisker-reinforced ceramic sintered bodies using simpler equipment and means.

As a result, first, the starting material powder obtained by uniformly mixing and dispersing ceramic whiskers in the ceramic powder that becomes the matrix is impact compressed, and the powder has a strength that can be cut.
After obtaining a molded body with a relative density of 90% or more, this molded body is cut into the required material shape taking into account sintering shrinkage, and this processed material, that is, the molded body, is sintered without using pressure. The inventors have discovered that a high-density whisker-reinforced ceramic sintered body having a shape extremely close to the final shape can be obtained by doing so, and have completed the present invention.

That is, this invention uses ceramic whiskers in volume %
A method for producing a whisker-reinforced ceramic sintered body containing 10 to 50% of ceramic whiskers, which includes uniformly dispersing and mixing ceramic whiskers in ceramic powder, filling a mold with this mixed powder, and impact-compressing the mixed powder. Provided is a method for producing a whisker-reinforced ceramic sintered body, which comprises forming a powder compact having a relative density of 90% or more (porosity of 10% or less), and then sintering it at a temperature of 1400 to 2000°C.

In this case, the ceramic powder is alumina powder, silicon carbide powder, silicon nitride powder, boron powder, boron carbide powder,
The ceramic whiskers may be composed of at least 1 fl of aluminum nitride powder;
sNa ) At least 1f of whiskers! You can also become more.

In the case of the normal powder compaction method using a mold, the ceramic powder with ceramic whiskers uniformly mixed and dispersed is
For the reasons mentioned above, it is much more difficult to increase the density than in the case of ceramic body powder.

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

Therefore, in this case, at least the remaining 45'% densification is required during sintering to obtain a densified sintered body.

However, in reality, as mentioned above, densification during sintering is also inhibited by the dispersed ceramic whiskers, so a method of slowly densifying while applying pressure at a higher temperature than in the case of ceramic powder is recommended. taken.

However, under the usual pressure of several tens of MPa, sufficient densification does not occur, and in this case also, a method of adding a small amount of auxiliary agent to aid sintering is used.

The sintering aid used here is also undesirable because it causes a decrease in the high temperature strength of the obtained sintered body.

Solving the above difficulties including processing problems 1
One method is to use static and dynamic ultra-high pressure sintering techniques that can utilize pressures as high as several GPa in order to promote densification. This is a method of creating a high-density molded body and sintering the molded body without applying pressure.

Among the former methods, the method using static ultra-high pressure technology has the disadvantage that the required equipment is large-scale and expensive, and it is difficult to operate.

On the other hand, although the dynamic method is effective for densification and sintering of powder, it is not practical because it has the problem of large and small cracks in the obtained sintered body.

Furthermore, what these two methods have in common is that although densification is easy, it is extremely difficult to produce a sintered body with a complicated shape.

For this reason, the amount of processing required to produce the final part increases, resulting in an increase in cost and does not solve the problems of the conventional method.

On the other hand, in the latter method, the starting material is made into a high-density compact with enough strength to be cut before main sintering, and after being processed into the required shape, the main sintering is carried out. The amount of machining required for finishing can be kept to a minimum. Although static high pressure technology can also be used in this latter method, this method has the aforementioned problems and is not practical.

This invention first molds whisker-containing ceramic powder to a high density using dynamic ultra-high pressure, that is, impact compression, then cuts the molded body and sinters it. The aim is to obtain a whisker-reinforced ceramic sintered body with toughness.

It is also possible to densify the powder and sinter it at the same time using the impact compression method, but this requires high pressure and temperature, and the sintered material obtained by impact compression under such conditions Many cracks occur on the body.

However, it is known from experience that cracks are less likely to occur if the pressure level does not reach sintering but merely densifies the powder.

This invention attempts to take advantage of such a tendency.

Dense compacts can be made by using the instantaneous impact pressure generated by the explosion of explosives or the collision of high-speed objects.

With this method, SI, which is difficult to insulate using the mold molding method used in schools, can be
High-strength ceramic powders such as C and 5IsN4 can also be densified relatively easily.

One of the characteristics of impact compression is that it can generate high pressures of several GPa to several tens of GPa in a short time of 10-6 seconds, which instantly increases the relative density of high-strength ceramic powder to over 90%. It becomes possible to increase the density.

The temperature during impact compaction can be adjusted by the commonly used pressure, provided the initial compaction density of the powder remains the same.

Conversely, if the pressure is constant, it is determined by the compacted density of the powder.

In order to obtain a uniform high-density compact without cracks using the impact compression method, it is important to use the impact compression method. The temperature needs to be low enough to prevent sintering of the powder, and the pressure used is preferably as low as possible in order to reduce residual strain in the resulting compact.

[Effect] Explain along with the effects.

[Embodiments of the invention] Examples will be described with reference to the drawings.

There are two ways to obtain a high-density compact by impact compression: using explosives and colliding high-speed projectiles fired with high-pressure gas.

When using any of these methods, it is important to collect the sample as a single lump without scattering the sample into pieces.

Fortunately, this sample collection technology is improving.

In FIG. 1, 1 is a plane 2 that can be used in the method of this invention.
It is a shadow compression device and is composed of a lower part 2 and an upper part 3.

2A is a sample container having a sample chamber 2B filled with a mixed powder 4 obtained by uniformly mixing ceramic powder and ceramic whiskers.

A steel momentum trap 2C is arranged outside of the sample container 2C to facilitate recovery of the sample container 2A after impact treatment, and a steel momentum trap 2C is placed below it.
Install D.

Note that the sample container 2A includes a bottom plate 2A1 and a bottom plate 2A1.
1 with a downward U-shaped cross section that is removably fitted from above.
It is composed of i2A2.

Momentum trap 2C mainly absorbs momentum in the side direction of the sample container, and momentum trap 2D absorbs momentum in the downward direction of the sample container, resulting in easy recovery of the sample after i*lA treatment. It is for.

It is not easy to uniformly mix the ceramic powder with minimal whisker damage, but each component is first made into a slurry state using a wet ball mill or stirrer, then blended, and then mixed again using a ball mill or stirrer. The method provides relatively uniform mixing with less whisker breakage.

The state of dispersion of ceramic whiskers in the matrix is important because it greatly influences the properties of the obtained sintered body.

When filling the sample container 2A with this mixed powder, it is desirable to fill it as densely as possible, and a relative density of 40% or more is preferable.

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

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

Furthermore, the planar combustion is propagated to the explosive 3C below, which causes bottom combustion and propagates downward, and due to the detonation impact pressure generated by this combustion, the flying plate 3D, which is the metal plate below, accelerates at high speed. and the lower sample container 2A&: collides.

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

The pressure and temperature generated in the mixed powder area 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 duration can be controlled by using a flying plate as shown in Figure 1. In case, it can be changed depending on the thickness, but 3I
When the steel plate I11 collides with the sample container at about 2 km/s, the pressure duration is about 1.5 x 10-' seconds, which is extremely short.

In addition, in the method shown in Figure 1, the sample area is exposed to a pressure of 50 GPa.
It is relatively easy to generate pressures up to

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

Reference numeral 6 denotes an explosive container, which is composed of an outer cylinder 6A, and 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.

4 is a mixed powder filled in a cylindrical sample container 7.

This figure shows a state in which an explosive 3C is placed in contact with a cylindrical sample container 7 and is detonated by a detonator 3B.

The detonation wave propagates downward, and the accompanying detonation mlE wave first shock-compresses the cylindrical sample container 7 inside it in the axial direction, and then the mixed powder 4 inside it is similarly Compressed.

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

Here, the outer circle M6A of the cylindrical sample container 7 and explosive container 6
The materials used include metal, paper, wood, and plastic.

Further, the conical plug 7A located above the cylindrical sample container 7 can be made of metal or wood, and this part is detonated by the detonator 3B and causes a detonation wave that spreads in a spherical shape inside the explosive 3C. It plays the role of shaping this spherical spreading detonation wave into a flat detonation wave before reaching the cylindrical sample container 7, and is essential for uniform impact compression of the sample. .

In the method of this invention, a whisker-containing ceramic molded body is heated to 1400 to 2000°C without pressure to obtain a sintered body close to true density. In order to process the shaped body beforehand, the relative density of the shaped body must be greater than 90%.

Although it depends on the type of ceramic used as the matrix and the blending ratio of whiskers, in a compact having a relative density of 90% or less, sufficient densification does not proceed even with the main sintering, and a sintered compact with high strength cannot be obtained.

Moreover, the strength of such a molded body is not sufficiently high, and cutting is difficult. The impact pressure required to densify a ceramic powder containing 10 to 50% by volume of ceramic whiskers to a relative density of 90% or more is determined by the target ceramic powder and the physical properties of the whiskers, and varies depending on each material. It is necessary to experimentally determine the conditions for each sheet combination.

When the degree of impact pressure is in a suitable range, the relative density is 9
At 0% or more, a uniform molded product without cracks can be obtained.

However, if the processing pressure exceeds the limit pressure determined by the combination of materials, seizure between powder particles, or intergranular bonding due to sintering, will occur, resulting in small and large cracks occurring in the recovered compact. , undesirable.

The range of impact pressure used in the method of the present invention is limited to a moderate pressure that does not cause sintering during impact processing, or even if sintering does occur, grain growth does not occur.

On the other hand, if the pressure is too low, the mixed powder will have a relative density of 90%
It is not possible to densify the product to the above level, and as mentioned above, the strength of the obtained molded product is low, and not only can it not be cut, but also the densification does not proceed due to main sintering, resulting in a high strength and high quality product that is inexpensive. It is not possible to obtain a whisker-reinforced ceramic sintered body with toughness.

Hereinafter, this invention will be explained in more detail with reference to Examples.

(Example 1) Alumina powder with average particle size lμI and average whisker diameter 0
．． SiC whiskers with a diameter of 5 μm and an average length of 30 μl were weighed separately at a volume ratio of 4:1, and each powder was first ball-milled with water to form a slurry. They were mixed and ball milled again.

After drying this ball mill mixed powder, it was vacuum degassed at 600°C to obtain the mixed powder of this example.

This mixed powder was compressed using the flat surface 7 compression device shown in Figure 1. IIA managed.

Here, the mixed powder was filled into the sample chamber 2B in FIG. 1 so that the relative density was about 53%.

Stainless steel was used as the material for the sample chamber 2B, and the size of the sample chamber 2B was 25 mm in diameter and 1 ha in height.

As the explosive 3C, a data sheet made by Shuppon with a detonation speed of 7.2 km/s was used, and as the flying plate, an iron plate with a thickness of 3.2 mm was used.

Here, molding tests were conducted at each flying plate speed shown in Table 1.

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

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

The cutting test for each compact was performed using a diamond sintered body as a cutting tool at a circumferential speed of about 35+a/win, and it was determined whether cutting was possible or not based on the degree of occurrence of cracks and chipping.

Next, these molded bodies were heated to 1500°C using a vacuum furnace.
, 1700° C., and 1900° C. for 1 hour and sintered, and the relative density and Kic value of the obtained sintered body were determined by measurement.

The KiC value was calculated by the Vickers indentation method under a load of 5 kg based on the lengths of cracks generated from all sides of the indentation.

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 molded product was good with no cracks, but the density of the molded product was low, and in the cutting test, it broke when it was sandwiched between the processing jigs. It happened.

Furthermore, with this level of compact density, as shown in Table 1, no significant densification was observed even after the subsequent heat treatment at 1,500 to 1,900°C.

On the other hand, when the flying plate speed increased to 1.8 km/s, the relative density of the recovered compacts certainly reached 96%.
Cracks had occurred, and in this case as well, it broke into small pieces when it was set in a processing jig.

When we observed the fracture surface of the small piece that caused the crack, we found that 'fIg
It was found that some alumina sintered due to the treatment alone.

The molded bodies of the samples obtained at flying plate speeds of 0.6 to 1.4 km/s had relative densities of 90 to 95%, had no cracks, and had the strength to be cut.

In addition, the sintered bodies obtained by sintering these molded bodies at 1700 to 1900°C were sufficiently densified and exhibited high 1c values of 7 to aMPaJm.

Table 1 Alumina + SIC whisker × Crack occurrence (Example 2) Si3N4 with average particle size of 0.6 μm and average whisker diameter
Alumina whiskers having a diameter of 3 μm and an average length of 30 μm were weighed separately at a volume ratio of 2:1, and the respective components were mixed using the same method and procedure as in Example 1.

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

Here, the molding test was carried out at a flying plate speed of Q,l shown in Table 2 to 1.6 km/s.

The sample after the IA process was collected in the same manner as in Example 1, and after appearance observation and density measurement, a cutting test was conducted.

Next, each of the obtained molded bodies was placed in a nitrogen atmosphere of 1 atm for 14 hours.
Sintering was carried out by holding at 00°C, 1600'e, and 1800°C for 1 hour. The relative density and Klc 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 appeared to be in good condition with no cracks, but the relative density was low and cutting was impossible. In addition, this sample has 1400 to 180
Heat treatment at 0° C. also showed only slight densification.

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

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

At flight plate speed 0.4-1.2 + a/s, relative density 9
A molded article having a strength of 3 to 98% was obtained, and all of them could be cut.

Further, in the treatment at 1400 to 1800°C, all exhibited excellent sinterability and exhibited high KIc values of up to 9 MPaJm.

Table 2 Sl, N4 + Alumina Whiskers
1. Sl, N, and whiskers with an average length of 40 μm were weighed at a volume ratio of 5:1, mixed, dried, and vacuum degassed using the same method and procedure as in Example 1. A mixed powder was obtained.

This mixed powder is placed in the cylinder shown in Figure 2? Shock treatment was performed using an IN compression device.

Here, an iron vibrator with an inner diameter of 20 m+e and an outer diameter of 25+s+a is used as the cylindrical sample container 7, and the length of the sample portion is l.
oOam.

In addition, a molding test was conducted using an anho explosive as the explosive 3C and setting the thickness to 10+am, 30 mm, 60 mm, and 100 mm.

After the processing, the cylindrical sample container was collected, split vertically into two, and the sample inside was taken out.

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

In addition, in the cutting test of the molded body, one end of the molded body was cut using diamond in the same manner as in Example 1, and it was determined whether machining was possible or not.

Next, the molded body was heated to 1,600°C in a nitrogen atmosphere of 1 atm.
A sintered body was obtained by maintaining the temperature at 2000° C. and 2000° C. for 1 hour.

The relative densities and Ki 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.

Although no cracks were observed in the molded body obtained with the explosive thickness of 10 μm, the relative density was as low as 82%, and cutting was impossible.

Moreover, the molded body obtained with an explosive having a thickness of 10 hm had several layered cracks, and could not be recovered as a lumpy molded body.

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

The molded bodies obtained with explosive thicknesses of 30 ma+ and 60 am had relative densities of 90% and 95%, were uniformly shrunk, and could be cut.

In addition, samples obtained by sintering these samples at 1800°C and 2000°C showed high relative density and Kic values of 5 to 6 M.
It showed a high value of PaJm.

Table 3 StC-5IsN4 Whisker Created ceramic powder.

SiC whiskers similar to those used in Example 1 were weighed into this ceramic powder to give a volume percentage of 10%, and mixed, dried, and mixed in the same manner and procedure as in Example 1.
A mixed powder of this example was obtained by vacuum degassing treatment.

Using the same device as in Example 1, this mixed powder was applied to a flying plate at a speed of 0. [The forming test was carried out at tkm/s, 1.0 + g/s.

0.8km/s, 1. The relative densities of the molded bodies obtained at OKM/s were 91% and 93%, respectively, and the molded bodies were uniform with no cracks in appearance.

When these molded bodies were subjected to a cutting test in the same manner as in Example 1, all of the molded bodies had the strength to be cut.

These molded bodies were heated at 1700°C in vacuum.

The relative density of the sintered body obtained by holding it at 1900°C for 1 hour is
Both the samples obtained at 0.6 km/s and 1.0+a/s reached 98%, and the Klc value was 5.5 MPaJ ra.
.

It was 5.8 MPaJm.

(Example 5) Aluminum nitride powder with particle size of 10 μm or less and average particle size
A matrix ceramic powder was prepared by mixing 3 μm Si and N4 powders at a volume ratio of 3:2.

SiC whiskers and Sl mountain whiskers, which are the same as those used in Example 1.2, were weighed to 1z1 to give a volume percentage of 50%, and mixed, dried, and mixed in the same manner and procedure as in Example 1. After vacuum degassing,
A mixed powder of this example was obtained.

This mixed powder was subjected to a molding test using the same apparatus as in Example 1 at flying plate speeds of 0.5 k11/s and 1.0 km/s.

The relative densities of the compacts obtained at flying plate speeds of 0.5 km/s and 1.0 km/s were as high as 93% and 95%, respectively, and the compacts were uniform with no cracking.

Moreover, all of them were able to be cut.

These samples were then exposed to 1600 ml of nitrogen in a 1 atm nitrogen atmosphere.
℃, and held at 1850°C for 1 hour for sintering. 0.5k
The relative densities of the sintered bodies from the compacts obtained by impact treatment at m/s and 1.0 km/s are 99% and 100%, respectively, and K
The tc values are 7.311Pa-/”m and 7.7M, respectively.
It was PaJIa.

[Effects of the Invention] As described above, according to the method of the present invention, ceramic powder containing 10 to 50% by volume of ceramic whiskers can be densified relatively easily to a relative density of 90% or more by impact compression, and can be cut. It is possible to obtain a molded article with 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, and are easily sintered, and can be easily sintered into a uniform and strong sintered body even by sintering without pressure. is obtained.

In addition, in the method of manufacturing a whisker-reinforced ceramic sintered body according to the method of the present invention, shrinkage during the sintering process of the high-density compact is extremely small, so the processing cost after sintering can be significantly reduced, which has industrial significance. is big.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a planar impact compression device that can be applied to the method of manufacturing a whisker-reinforced ceramic sintered body of the present invention, and FIG. 2 is a longitudinal sectional view of a cylindrical impact compression device. 190. Planar impact compression device, 231. Lower part, 2A, Sample container, 2B, Sample chamber, 2C, 2D, Momentum trap, 311. Upper part, 3A, Explosive lens, 3B, Detonator, 3C, Explosive, 3D. 4 5. 6. A B C 7A. Flying plate, mixed powder, cylindrical impact compression device, explosive container, outer cylinder, upper plate, lower plate, cylindrical sample container, 7B, plug.

Claims (3)

[Claims] 1. In a method for manufacturing a whisker-reinforced ceramic sintered body containing 10 to 50% by volume of ceramic whiskers, ceramic whiskers are uniformly dispersed and mixed in ceramic powder, the mixed powder is filled into a mold, and the mixed powder is A method for producing a whisker-reinforced ceramic sintered body, which comprises forming a powder compact with a relative density of 90% or more (porosity of 10% or less) by impact compression, and then sintering at a temperature of 1400 to 2000°C. . 2. the ceramic whiskers are alumina whiskers;
The method for producing a whisker-reinforced ceramic sintered body according to claim 1, which comprises at least one of silicon carbide whiskers and silicon nitride whiskers. 3. 2. The method for producing a whisker-reinforced ceramic sintered body according to claim 1, wherein the ceramic powder comprises at least one of alumina powder, silicon carbide powder, silicon nitride powder, boron powder, boron carbide powder, and aluminum nitride powder.