JPH03137060A - Production of high strength ceramic sintered compact - Google Patents

Abstract

PURPOSE:To obtain a ceramic sintered compact having high density and high strength by filling a compacting die with a powder mixture of specific metal and nonmetal, exerting impact compacting, and igniting and allowing exothermic chemical reaction to proceed by means of pressurization and heating. CONSTITUTION:At least one kind among the metal group consisting of the group VIa, Va, and VIa metals of the periodic table and at least one kind among the nonmetal group consisting of carbon, boron, boron carbide, and boron nitride are mixed. Subsequently, a compacting die is filled with the resulting powder mixture, and impact compacting is exerted to form a powder green compact of >=90% relative density (<=10% porosity). Then, by heating a part or the whole of the above powder green compact while pressurizing this powder green compact at >=1MPa pressure, sintering is applied to this powder green compact while igniting and allowing exothermic chemical reaction between at least one kind among the metal group mentioned above and at least one kind among the nonmetal group mentioned above to proceeds, by which the desired sintered compact can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a high-strength ceramic sintered body.

More specifically, the present invention provides a high-strength ceramic sintered body that can easily and inexpensively produce a high-density and high-strength ceramic sintered body useful as various wear-resistant and heat-resistant materials including cutting tools. The present invention relates to a method for producing a solid.

[Prior Art] Conventionally, carbides and nitrides, including diamond, cubic boron nitride, and metals in groups 4a, 5a, and 6a of the periodic table, have been used as ceramic materials that have high strength both at room temperature and at high temperatures. materials, borides and silicon carbides,
In addition to nitrides, oxides such as alumina are known.

Because these powders have strong covalent bonds between their constituent elements, if these raw powders are sintered without applying pressure, the volumetric diffusion of atoms that promotes shrinkage of the entire green compact sample, that is, densification of the structure, will not easily occur. It is also known that it is difficult to produce dense sintered bodies because this does not occur and surface diffusion of particles takes precedence over volumetric diffusion of atoms.

In this way, it is extremely difficult to sinter high-strength ceramic materials alone, so additives that act as auxiliaries to assist the movement of atoms between powder particles are usually added and sintered under pressure. methods have been adopted.

For example, in sintering TiB1 or SiC powder to which a sintering aid has been added, hot pressing has been mainly performed using a graphite mold that can pressurize up to several tens of MPa.

However, although the pressure applied in this hot press method is effective for densifying the structure, the pressure that can be generated is limited by the strength of the graphite mold at high temperatures, so the pressure that can be generated decreases at high temperatures. There are drawbacks.

The sintering temperature also needs to be low enough to prevent the sample from reacting with the graphite mold.

Due to such restrictions, it has been difficult to produce a high-density hard ceramic sintered body having strong intergranular bonds in the hot press method using a graphite mold.

On the other hand, as a method to reduce the sintering temperature and make the structure denser,
Although a method of lengthening the sintering holding time has been considered, in this case there is a problem that particles tend to become coarser, which reduces the strength of the sintered body.

The sinterability of such high-strength ceramics reflects the material's excellent mechanical properties at both room and high temperatures.

Another hurdle in producing high-strength ceramic materials as practical materials lies in the difficulty of processing the sintered material into the desired shape.

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 material saga.

Although ceramic materials are generally brittle, they also have high strength and hardness (and many are 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 the material manufactured by this method, not only does the machining allowance increase, resulting in inefficiency, but also the machining cost becomes abnormally high.

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.

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

Sintering of high-strength ceramic powder requires the addition of an auxiliary agent that aids in the sintering, and there is a problem in that this auxiliary agent significantly deteriorates the high-temperature properties of the sintered body.

Furthermore, when processing a sintered body obtained by such a method, the processing cost may account for more than 50% of the product cost, leading to further increases in the cost of this type of material.
There has been a problem in that it has hindered the expansion of wider applications of high-strength ceramic sintered bodies.

The present application was created in view of such problems with the conventional technology, and its purpose is to provide something that addresses the following issues.

This invention was made in view of the above circumstances, and while maintaining the excellent properties of high-strength ceramic materials, it improves the drawbacks of the conventional manufacturing method as described above, and is intended to improve cutting tools and other products. The purpose of this invention is to provide a method for producing a high-density, high-strength ceramic sintered body suitable for various structural material widths.

Rather than directly sintering high-strength ceramic materials from their compound powders (as described above), the present inventors synthesize these compounds from their constituent elements using an exothermic chemical reaction, and at the same time synthesize them from their constituent elements. We have discovered that by sintering using reaction heat, a dense and high-strength ceramic sintered body can be obtained with simpler equipment and means than conventional sintering methods.

In addition, by selecting a type of exothermic chemical reaction that involves metal powder, molding of the mixed powder serving as the starting material becomes extremely easier compared to molding a high-strength ceramic compound powder. It was also found that even when molded to high density, the occurrence of defects such as cracks can be significantly reduced.

Based on these two main findings, the present inventor has developed carbides and nitrides of metals from groups 4a5a and 6a of the periodic table, which have particularly excellent thermal and mechanical properties among high-strength ceramic materials.
We have been conducting intensive research with the aim of developing a method for producing dense sintered bodies made of borides and their solid solutions in a simpler and cheaper manner.

As a result, carbides of metals from groups 4a, 5a, and 6a of the periodic table,
Nitride, boride, and a solid solution thereof can be produced by an exothermic chemical reaction. At least one of the above-mentioned metals and at least one non-metal such as carbon, boron, boron carbide, and boron nitride. After uniformly mixing the two components and impact-compressing this mixed powder with an appropriate strength to form a molded body with a relative density of 90% or more and having strength that allows machining such as cutting, this molded body is By machining the material into the required shape taking into account sintering shrinkage and heating the processed material, that is, part or all of the molded body, under a pressure of IMPa or higher, the gap between the metal component and the non-metal component is created. The present inventors have discovered that a high-strength ceramic sintered body having a shape extremely close to the final shape can be obtained by sintering the above-mentioned molded body while igniting and allowing the exothermic chemical reaction to proceed, leading to the present invention. .

That is, this invention applies to periodic table 4a.

A method for producing a ceramic sintered body made of carbides, nitrides, borides, and solid solutions of group 5a and 6a metals, including at least lfl in the metal group consisting of metals from groups 4a, 5a, and 6a of the periodic table; At least one of the nonmetallic group consisting of carbon, boron, boron carbide, and boron nitride is mixed with the powder, and this mixed powder is filled into a mold and subjected to impact compression to reduce the relative density to 90% or more (void voids). 10% or less), and by heating a part or the whole of the powder compact while pressing at a pressure of I MPa or more, at least 1 fl of the above metal group and the above non-containing material are heated. Provided is a method for producing a high-strength ceramic sintered body, characterized in that the powder compact is sintered while igniting and advancing an exothermic chemical reaction between at least one metal group.

[Means for Solving the Problems] In order to achieve the above object, the present invention is as follows.

That is, in the synthesis of a certain type of ceramic, especially a high melting point ceramic, the heat of reaction for synthesizing a compound from its constituent elements reaches tens to hundreds of KJ per mole. This large heat of formation propagates one after another into the compact of the raw material mixed powder, and the excitation, initiation, and synthesis of one reaction are sustained in sequence (.

For example, when synthesizing titanium carbide (1 ric) from titanium fTil and carbon fcl powder, titanium carbide fTic
) matching the stoichiometric ratio of titanium fTil and carbon fcl
When the powder is mixed and molded, and a heating wire made of tungsten or the like is used to ignite the powder from one end to start the reaction, the reaction proceeds throughout the molded body.
Titanium carbide fTicl without the need for external heating
can be synthesized.

In some cases, sintering occurs simultaneously with this synthesis, but the resulting sintered body is extremely porous.

Such a ceramic synthesis method does not require a special furnace for synthesis and is economical.

Depending on the nature of the reaction, the above reaction may be a self-heating reaction or
This reaction is called a self-combustion reaction, and we will use the former term here.

Carbides, nitrides, borides, and solid solutions of metals of groups 4a and 5a6a of the periodic table, which are the object of the present invention, are typical materials that can be synthesized by self-heating reactions.

For example, the following examples can be given:

Type 1 W+C-WC 2) fTa, Zrl+2B-+ (Ti, Zr1Bx
316Ti+284C→2TiC+4TiB*41Ti
+CN4'Ti (C,Nl) The temperature increase due to heat accompanying the self-heating reaction can be calculated on the assumption that all of the heat of formation is used to increase the temperature of the product.

For example, the generation energy in the case of Ti+C-*TiC is 185KJ/mol, and the temperature rise at that time is 32KJ/mol.
It reaches as high as 10K, which corresponds to the melting point of the product TiC.

This indicates that a liquid phase appears during the reaction, which facilitates the mass transfer by diffusion, and the appearance of the liquid phase is effective in producing a strong sintered body. .

In addition, the generation of this liquid phase makes it extremely easy to deform the target material in both micro and macro aspects, requiring the high pressure of several hundred MPa required for hot pressing of high-strength ceramic materials without using additives. It is possible to obtain a dense sintered body without causing any sintering.

In the present invention, a pressure of 1 MPa or more is used during the sintering of the compact formed into a high-density molded body through a chemical reaction, and the reason for this is as follows.

One reason is that although a compact having a relative density of 90% or more is used in the present invention, it still contains voids, and these voids are to be eliminated from the sintered body.

The other reason is to compensate for volume loss due to the nature of this type of chemical reaction.

For many self-heating reactions, the volume loss from the raw material system to the product system is 10%-25%, and if the mass transfer cannot keep up with this volume loss, the resulting sintered body will contain this volume loss. are left behind as pores.

Therefore, in order to obtain a dense sintered body, it is necessary to eliminate 10 to 35% of the voids caused by the above two causes by means such as pressurization during sintering.

Although a simple uniaxial method can be used as the pressurizing means, a method that allows hydrostatic pressurizing is more suitable.

In addition, the pressure required at this time can be lowered by the appearance of the liquid phase as described above, but the amount of liquid phase produced during the reaction varies depending on the target material, and the amount of voids included also differs, so It is necessary to set the pressure necessary for

In the production of the sintered body according to the present invention, as a result of experiments, a pressure of at least 1 MPa or more was required.

Another advantage of sintering the powder of a high-hardness ceramic material as a starting material, instead of sintering it directly as a starting material, is to use the constituent elements of the compound and sinter it simultaneously with the synthesis reaction. It is extremely easy to increase the density of the molded body.

As mentioned above, the starting materials according to the present invention must include 4a and 5a.
, contains 50% by volume or more of group 6a metal powder,
A compact having a relative density of about 60% (porosity: 40%) can be obtained relatively easily even by using a powder compaction method using an ordinary mold. This effect is thought to be due to the contained metal powder being easily plastically deformed and filling the voids.

On the other hand, when compound powders such as carbides and borides are used as starting materials, the mechanical strength of these compounds is quite high, and when a normal mold is used, the relative density of the molded product is at most 5.
It only reaches about 0%.

Although molding the mixed powder according to the present invention is relatively easy for the reasons mentioned above, it is difficult to obtain a high-density molded body having the strength to be machined by cutting or cutting after molding.
This is extremely difficult considering the strength of the mold.

As a means for obtaining a high-density molded body strong enough to be subjected to such mechanical processing, static or dynamic ultra-high pressure techniques that can utilize ultra-high pressures of several GPa can be used.

However, the former 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.

The present invention attempts to obtain a high-density molded body having a strength that allows machining by using the latter dynamic ultra-high pressure, that is, impact compression.

It is also possible to densify and sinter the powder at the same time by impact compression, but this requires high pressure and temperature, and if impact compression is performed under such conditions, the resulting sintered body will contain many particles. Cracks will occur.

However, it is known from experience that cracks are less likely to occur if the pressure level is such that the powder merely becomes densified without reaching sintering.

This invention attempts to take advantage of such a tendency.

One of the characteristics of impact compression is that it can generate a high pressure of several GPa to several tens of GPa, although it takes an extremely short time of 10-6 seconds.

Under such high pressures, metallic materials exhibit a superplastic state and densification occurs with high-speed mass transfer.

The mixed powder of the starting raw material according to the present invention contains 50% by volume or more of such metal components, and can be densified to a relative density of 90% or more by impact compression.

It is believed that this metal component promotes the densification of the entire molded body, resulting in a high-density molded body that is strong enough to be machined.

Further, the entanglement of the metal components due to deformation during this densification plays an important role in improving the strength of the obtained molded product.

In the method for producing a ceramic sintered body according to the present invention, the mixed powder serving as the starting material undergoes a self-heating reaction to produce carbides,
It is made of powder that can produce borides, etc., but if the reaction heat here is too large and the amount of liquid phase produced is too large, or if the temperature is too high and the particle growth is too significant, the mixed powder Ceramic powder as a compound can also be added to an extent that does not impair moldability.

[Effect 1 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, reference numeral 1 denotes a planar impact compression device that can be used in the method of the present invention, and is composed of a lower portion 2 and an upper portion 3.

2A is at least one component in the metal group consisting of group 4a, 5a, and 6a metals of the periodic table, carbon, boron, boron carbide,
This is a sample container having a sample chamber 2B filled with a mixed powder 4 obtained by uniformly mixing at least one component of the non-metal group consisting of boron nitride.

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

The sample container 2A includes a bottom plate 2Al and a lid 2A2 having a downward U-shaped cross section and detachably fitting into the bottom plate 2AI from above.
It consists of

The momentum trap 2C mainly absorbs the momentum in the side direction of the sample container, and the momentum trap 2D absorbs the momentum in the downward direction of the sample container, thereby facilitating the collection of the sample after impact treatment. .

A dry method or a wet method can be used to mix the metal component powder and the non-metal component powder that constitute the mixed powder 4, but the wet method is suitable when the powder used is fine.

When a wet method is used, after mixing, drying and vacuum degassing are performed to obtain mixed powder 4.

Here, a hydride of the metal component can be used as the powder of the metal component, considering handling safety, and the mixing operation is performed in this state, dehydrogenated in the next degassing process, and mixed as the metal component. You can also take a method.

This method using a hydride is easy to crush, and is particularly effective when using fine metal powder.

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 from the viewpoint of cost, iron, copper, brass, stainless steel, etc. are suitable.

The upper part 3 in FIG. 1 is the explosive component of this device. A circular 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. It has become so.

Furthermore, the planar combustion is propagated to the explosive 3C below, causing planar combustion in the explosive and propagating 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 collides with the sample container 2A below.

This collision generates a plane shock wave in the sample container, which is further propagated to the mixed powder 4, and the mixed powder is impact-compressed and 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. It can be changed depending on the thickness.

When a 3cm iron plate collides with a sample container at approximately 2 km/s, the pressure duration is approximately 1.5 x 10-' seconds,
Extremely short.

In addition, in the method shown in Figure 1, the sample area is heated to ~1500℃.
Temperatures up to 50 GPa and pressures up to 50 GPa can be generated relatively easily.

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.

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

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 shock wave first shock-compresses the cylindrical sample container 7 inside the sample container 7 in the axial direction, and then the mixed powder 4 inside the same. be done. The pressure generated in the mixed powder 4 portion can be adjusted by the type and amount of explosive used.

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

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

In the method according to the present invention, an exothermic reaction of the compact is started and progressed under a pressure of IMPa or higher to sinter the compact. However, if there are too many voids in the initial compact, densification during this process becomes difficult. .

Furthermore, in the method according to the present invention, the molded body is machined into the required shape before sintering, and for that purpose, the relative density of the molded body must be at least 90% or more.

Although it depends on the blending ratio of metal components and non-metal components in the mixed powder, if the compact has a relative density of 90% or less, the densification in the sintering process described above will not be sufficient and a sintered compact with high strength will not be obtained. was difficult.

In addition, the strength of such molded bodies was not sufficiently high and could not withstand machining such as cutting or cutting.

The impact pressure required to densify the mixed powder to a relative density of 90% depends on the nature and content of the metal component in the mixed powder, and it is necessary to find the optimal conditions.

If it is not possible to increase the impact pressure above a certain level, or if you want to obtain a molded product with higher strength, add an extra metal component to the extent that does not impair the strength of the resulting sintered product, in order to aid the molding of the mixed powder. It can also be used by adding it.

At this time, not only metal components involved in the reaction but also metal components not involved in the reaction can be used.

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 metal component particles, or intergranular bonding due to sintering, will occur, resulting in small and large cracks in the resulting compact. , undesirable.

Furthermore, if the pressure increases to the extent that a reaction occurs, many cracks and pores will occur in the molded product.

Therefore, the range of impact pressure used in the method of this invention is limited to a moderate pressure that does not cause sintering during the impact treatment, or even if it does, does not cause grain growth.

On the other hand, if the pressure is too low, the mixed powder will not be able to be densified to a relative density of 90% or more, and as mentioned above, the strength of the resulting compact will be low, and not only will it not be possible to machine it, but it will also not be possible to densify it by sintering. As a result, an inexpensive and high-strength ceramic sintered body cannot be obtained.

The present invention will be explained in more detail with reference to Examples below.

Example 1 Tantalum (Tal powder with an average particle size of 1 ous and boron carbide (B, C) powder of 325 mesh or less in a molar ratio of 3:1)
N-hexane was added and mixed in a ball mill.

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 subjected to impact treatment using a planar impact compression device shown in FIG.

Here, the mixed powder is placed in the sample chamber 2B of the first section at a relative density of 5.
It was filled to a concentration of 5%.

Iron was used as the material for the sample chamber 2B, and the size of the sample chamber 2B was 25 mm in diameter and 10 mm in height.

A data sheet made by Shubon with a detonation speed of 7.2 kffi/s was used as the explosive 3C, and a thickness of 3.2 mm was used as the flying plate.
An iron plate was used.

Here, +I is added to the flight plate speed 03 to 2.5 shown in Table 1.
A molding test was conducted at /s.

After the impact treatment, the sample container was recovered, the iron part 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.

Next, the bulk density of these recovered molded bodies was measured by the Archimedes method using water, and the relative density of the molded bodies was calculated. The cutting test for each compact was performed using a diamond sintered body as a cutting tool at a circumferential speed of 35 m/min.
At that time, it was determined whether cutting was possible or not based on the degree of cracking and chipping.

In addition, as a result of X-ray diffraction, the sample obtained at a flying plate speed of 2.5 km/s shows that at this point, the exothermic reaction has already progressed by about half, and it is in a semi-sintered state, with many lamellar cracks. was. For this reason, cutting work was also impossible.

Next, each molded body is placed on a flat zirconia sintered body under an argon pressurized atmosphere of 5 MPa, and one end of the molded body is heated and ignited by applying electricity to an ignition jig (tungsten wire) to cause a reaction. I started it.

The reaction was completed in a few seconds.

After cooling, the relative density of the sintered body was measured, and one end of the sintered body was polished with a diamond rotary grindstone, then mirror-finished, and the fracture toughness value (hereinafter referred to as Kic value) was measured by the Vickers indentation method using a load of 20 kg. did.

Next, using the same mirror-finished sample, the Vickers microhardness was measured at room temperature using a load of 100 g. The results for the samples obtained at each flying plate speed are summarized in Table 1.

Table 1 Mixed powder: 3 moles of tantalum + 2 moles of boron carbide, Sintering: 5 MPa argon atmosphere △ Small cracks and chips on the outer periphery Although the appearance was good with no cracks, the density of the compact was low and did not have enough strength to allow cutting.

In this molded body, the reaction could be started by heating with a tungsten wire, but the relative density of the obtained sintered body was as low as 89%.

As shown in Table 1, the molded bodies obtained at flying plate speeds in the range of 0.7 to 1.9 km/s had no defects such as cracks in appearance, and the relative density of the molded bodies was 90% or more. , and cutting processing was also possible.

The sintered bodies of these samples reached a relative density of 96% or more, and Ki
The c value was also about 3.8 MPaJm or more, indicating that it had sufficiently high toughness. Further, the microhardness of these sintered bodies was 2470-2850 kg/1 m''.

As a result of X-ray diffraction, the main constituent phases of the obtained sintered body were TaBm,
It was TaC, and no unreacted Ta, B, or C diffraction particles were observed.

For comparison, a molded body obtained at a flying plate speed of 1 and 3 km/s was heated in the same manner as above in an argon atmosphere of 0.5 MPa to initiate a reaction, and a sintered body was obtained, but the relative density was 80%, which was lower than that of the molded body.

Also, as another comparison, T with an average particle size of 10LLm
aB1 and TaC powder were mixed at a molar ratio of 2:1, and the mixed powder was impact compressed at a flying plate speed of 1.3 km/s.

The obtained compact was broken into several small pieces upon recovery, and the relative density measured in one of the small pieces was as low as 88%.

Example 2 Vanadium fVl powder with an average particle size of 15 LLm and a particle size of 0.
After preparing and mixing 6 am amorphous carbon (C) powder at a molar ratio of 2:1, vacuum degassing treatment was performed at 600 ° C.
A mixed powder of this example was obtained.

This mixed powder was subjected to impact treatment using the same apparatus as in Example 1 at a flying plate speed of 02 to 2.0 km/s.

In this case, the initial packing density of the mixed powder was 60%.

The sample after the impact treatment was collected in the same manner as in Example 1, and evaluated in the same manner as in Example 1.

Table 2 shows the results obtained under each condition.

As a result of X-ray diffraction, for the sample with a flying plate speed of 2.0 km/s,
An exothermic reaction had already occurred, producing vanadium carbide, creating a porous structure and cracks of various sizes.

On the other hand, the sample obtained at 0.2 km/s had no problems in appearance but lacked strength.

On the other hand, the molded body obtained at +a/s of 0.2 to 1.5 was placed on a graphite jig, placed in a pressure vessel, and then pressurized to 7 MPa with nitrogen gas, using the same method as in Example 1. The sample was heated to ignite and start the reaction.

The obtained sintered body was evaluated in the same manner as in Example 1, and the results are summarized in Table 2.

X Ii! As a result of diffraction, the obtained sintered bodies were all VC
1VN, and slight generation of V fcNl was also observed. All of the sintered bodies reached a relative density of 981 or higher, with the exception of the one obtained at 0.2 +++/s, and sufficiently high values of fracture toughness and microhardness were obtained.

Table 2 Mixed powder: 2 moles of vanadium + 1 mole of carbon Sintered: 7M
F'a nitrogen atmosphere *O △ × No chips or cracks Small chips or cracks on the outer periphery Cracks or pores Occurrence Example 3 Molybdenum (Mat powder with an average particle size of 10 μm or less, hafnium fHfl powder with an average particle size of 10 μm or less, Amorphous boron (Bl powder with an average particle size of 1 μm or less and carbon (C) powder with an average particle size of 0.6 LLm or less were mixed in a molar ratio of 2:1:4:2, respectively, and using toluene. The mixture was warmly mixed to obtain the mixed powder of this example.

This mixed powder was subjected to impact treatment using the same apparatus as in Example 1 at a flying plate speed of 0.3 to 2.4 +n/s.

In this case, the initial packing density of the mixed powder was 60%.

Each sample was collected by the same method as in Example 1, and
The molded bodies were evaluated in the same manner as described above.

Table 3 shows the results obtained under each condition.

In the molded product obtained at a flying plate speed of 2.4 km/s, the reaction had already progressed, and cracks were observed as well as pores.

On the other hand, the compact obtained at 0.3 km/s had a low density and did not have sufficient strength.

Next, the sample obtained at 0.3 to 1.8 km/s was heated and ignited in the same manner as in Example 1 to initiate a reaction and obtain a sintered body.

The test results for the obtained sintered bodies are summarized in Table 3.

Except for the sample obtained at 0.3 km/s, the others exhibited high relative density and excellent physical properties.

As a result of x1 type diffraction, the main constituent phases of these sintered bodies are lJo*c, HfC, MoB, 1(fBi, and slightly fMo, Hfl ClfMo, Hfl B
The formation of was also observed.

Table 3 Sintering: 5 MPa argon atmosphere *O △ × No chips or cracks Small chips or cracks on the outer periphery Cracks or pores generated Example 4 Titanium hydride (TiHz) with a particle size of 325 mesh or less
T with a particle size of 1 uI or less obtained by ball milling the powder
iHm powder and boron nitride fBN with an average particle size of 1 μm or less
) The powders were mixed in a ball mill using n-hexane so that the molar ratio was 3.2+2.

After drying the mixed powder, it was heated at 600°C under vacuum to reduce TiHs to Ti metal, thereby converting Ti and ON.
A mixed powder 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 301 and an outer diameter of 3.
A 5a+m brass vibrator was used, and the length of the sample section was 100m+l+.

In addition, an anho explosive is used as an explosive, and its thickness is 5~
A molding test was conducted with the length set at 60 mm.

After the impact treatment, the sample was collected, and after observing its appearance, a disk-shaped sample with a thickness of 5 mm was cut out from the center in the axial direction, and the density was measured.

The cutting test was the same as in Example 1 (one end of the molded body was cut using a diamond tool,
It was decided that it was not possible. The results are shown in Table 4,
When the explosive thickness was 5-, the densification was not sufficient and the strength was low.

On the other hand, when the explosive thickness was 60 mm, the reaction had already progressed almost completely, many cracks and pores were generated in the sample, and the relative density was as low as 82%.

The relative density of the molded body obtained with an explosive thickness of lO~40ff1m reached 90% or more, and cutting was possible.

A disk-shaped sample of these molded bodies was cut out using 3M
The mixture was heated to 1000° C. for 1 hour in argon gas of Pa to ignite and start the reaction, and a sintered body was obtained. As a result of X-ray diffraction, the main constituent phases of the obtained sintered body were TiN and TiBs, and no unreacted Ti was observed.

The evaluation results for each sintered body are summarized in Table 4.
Samples obtained with explosive thicknesses of 1O to 40n+m had high relative densities and exhibited sufficiently high values for both fracture toughness and hardness.

Table 4 Mixed powder: Titanium hydride fTiH*) 3.Boron 2ide I
Sintering with 12 moles of BN: 3 MPa argon atmosphere moles + nitrogen*O No chips or cracks △ Small chips or cracks on the outer periphery × Cracks or pores generated [Effects of the invention] As described above, according to the method of the present invention, impact compression ,
A mixed powder serving as a starting material for obtaining a high-strength ceramic sintered body can be relatively easily densified to a relative density of 90% or more, and a molded body having a strength that can be machined can be obtained.

In the method of the present invention, the mixed powder serving as the starting material is
The high-density compact obtained by the above-mentioned impact treatment is sintered by heating one end of the powder, which is made of powder that can generate carbides, borides, etc. through a self-heating reaction.
A high-strength ceramic sintered body made of carbides, borides, etc. with excellent high-temperature strength can be obtained by simply igniting and starting the reaction.

In addition, in the method for producing a high-strength ceramic sintered body according to the present invention, the shrinkage of the high-density compact during the sintering stage is small;
This can significantly reduce processing costs after sintering.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of a planar impact compression device that can be applied to the method for producing a high-strength ceramic sintered body of the present invention, and FIG. 2 is a high-strength ceramic sintered body 1 of the present invention. 2. 2A. B2C. 3A. 3B. 3C. 3D. 4. 5. 6A. 6B. C7. FIG. 2 is a longitudinal cross-sectional view showing an example of a cylindrical impact compression device that can be applied to the manufacturing method of FIG. Planar impact compression device, lower part, sample container, sample chamber, 2D, momentum trap 1, upper part, explosive lens, detonator 1, explosive, flight plate, mixed powder, cylindrical impact compression device 1, explosive container, outside Cylinder, upper plate, lower plate, cylindrical sample container, 7A, 7B. plug.

Claims (1)

[Scope of Claims] A method for producing a ceramic sintered body comprising carbides, nitrides, borides, and solid solutions of metals of groups 4a, 5a, and 6a of the periodic table,
At least one member of the metal group consisting of group 5a and 6a metals is mixed with at least one member of the non-metal group consisting of carbon, boron, boron carbide, and boron nitride, and the mixed powder is molded into a mold. The relative density is 90 by filling the
% or more (porosity 10% or less), after forming a powder compact, 1
By heating a part or the whole of the powder compact while pressurizing at a pressure of MPa or more, the exothermic property between at least one member of the metal group and at least one member of the non-metal group is reduced. A method for producing a high-strength ceramic sintered body, characterized by sintering a powder compact while igniting and advancing a chemical reaction.