JPH0867549A - Ceramics of layer structure - Google Patents

Abstract

PURPOSE: To produce a ceramics of a layer structure, excellent in mechanical properties such as strength even at high temperatures and oxidation and corrosion resistances and having high reliability. CONSTITUTION: This ceramics of a layer structure has a surface layer 1 consisting essentially of an oxide ceramics, an inner layer 2 consisting essentially of a nonoxide ceramics and a thermal stress relaxing layer 3, formed in the interfacial part of the surface layer and the inner layers and having the thermal expansion coefficient in the intermediate between those of both or changing the composition thereof. Furthermore, a fiber layer 4 containing one or more three-dimensionally compounded ceramic fibers is constituted in a part, etc., extending from the vicinity of the thermal stress relaxing layer of the surface layer through the thermal stress relaxing layer to the vicinity of the interfacial part of the inner layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has excellent mechanical properties such as strength, oxidation resistance, and corrosion resistance. Moreover, even if a crack should occur, the entire part will not be broken. , A layered structure that exhibits high reliability, especially under high temperature and harsh environment, by playing its role until the operation of the device etc. composed of parts using this material can be safely stopped Regarding ceramics.

[0002]

2. Description of the Related Art Conventional structural ceramics have many excellent characteristics such as high strength and heat resistance centering on silicon carbide, silicon nitride, sialon, etc., and therefore, they are vigorously applied as mechanical parts. It is being advanced. In particular, it is expected to be used at high temperatures such as gas turbine parts and automobile engine parts, and many results have been obtained. However, the materials obtained up to now correspond to about 1300 ° C class at the gas inlet temperature of the gas turbine at most, and the oxidation resistance of the non-oxide ceramics at the temperature higher than that (for example, 1500 ° C class), It cannot be used as it is because of the problem related to the material nature of corrosion resistance. In other words, even these non-oxide ceramics which have excellent corrosion resistance and oxidation resistance are inevitable to be oxidized at high temperatures around 1500 ° C or higher because they are non-oxide, and the required life is obtained. I can't.

On the other hand, many oxides have a marked decrease in strength at high temperatures, but have no problem of oxidation resistance, and many have excellent corrosion resistance against alkali and the like.

Therefore, it is considered to make the surface layer an oxide having excellent oxidation resistance and corrosion resistance. However, the influence of thermal stress caused by the difference in the physical property values of the two, particularly the difference in the thermal expansion coefficient, is considered. It is large, and cracks are likely to occur particularly on the oxide side. Therefore, it is necessary to take some measure for relaxing the thermal stress at the interface between the two. For example, in Japanese Patent Application No. 4-66430, the inventors of the present invention have proposed a combination of alumina and silicon nitride or the like, and in the case of containing sialon in the middle, the solid solution amount of Al in the combination is continuous or It has been found that it is effective to form an interface part that changes discontinuously.

However, at high temperatures around 1500 ° C. or higher, the stability of the interface has been insufficient until now. In addition, even if the strength is high, the strength of the non-oxide ceramics also begins to decrease in such a temperature range, so that the difference between the design stress applied to the material and the actual strength decreases, and the strength margin decreases. Therefore, if a small crack is generated somewhere due to flying objects, etc., it will lead to catastrophic destruction of the whole due to rapid deterioration of the non-oxide layer due to peeling of the oxide layer. This raises concerns that it could happen.

For example, when it is used as a blade of a gas turbine, catastrophic destruction may spread not only to the destruction of the member but also of other components, so that it is scattered at least from the time when the destruction occurs until the operation is stopped. It is especially important that you do not get sick.

As described above, in a material such as a high temperature gas turbine material in the future which is required to withstand long-term use in a high temperature environment, in addition to high strength, high toughness and excellent oxidation resistance, high fracture In terms of satisfying both the resistance characteristics, the current situation is that a sufficient solution has not yet been made.

[0008]

High-strength non-oxide ceramics and ceramics such as oxides which are responsible for oxidation resistance and corrosion resistance at high temperatures of around 1500 ° C. or higher and in an atmosphere of oxidative corrosion. In order to combine and fuse the two so as to exert their merits, it is the most important task to find a structure having high reliability at the interface between the two and also with respect to the occurrence of cracks.

The present invention is intended to solve the above-mentioned problems and to provide a highly reliable layered structure ceramic which is excellent in mechanical properties such as strength even at high temperature, and is excellent in oxidation resistance and corrosion resistance. is there.

Further, according to the present invention, it is possible to achieve both strength / toughness and oxidation resistance by laminating oxide-based ceramics on the surface layer of non-oxide-based ceramics for the purpose of use under high temperature and oxidizing atmosphere. With respect to the material to be solved, the problem that the fundamental solution to prevent catastrophic destruction due to peeling off of the oxide layer and the occurrence of defects has not been solved, in addition to high strength / toughness and oxidation resistance, It is an object of the present invention to provide a layered structure ceramic that satisfies both high resistance to fracture damage.

[0011]

In the present invention, the thermal stress when the surface layer is made of oxide and the inner layer is made of non-oxide is relaxed,
The interface has consistency, and even if a crack occurs, it suppresses crack growth and has high reliability. It can be used at a temperature around 1500 ° C or higher and in an oxidative corrosive atmosphere. The means for realizing such a structure was clarified.

That is, the first aspect of the present invention is a layered structure ceramic comprising a surface layer containing oxide ceramics as a main component and an inner layer containing non-oxide ceramics as a main component. At the interface with the layer, one or two or more thermal stress relaxation layers having a thermal expansion coefficient intermediate between the two, or the composition of both layers, is continuously formed.
Or having a thermal stress relaxation layer that changes discontinuously,
Furthermore, the part of the surface layer extending from the vicinity of the thermal stress relaxation layer to the vicinity of the interface part of the internal layer via the thermal stress relaxation layer, the part of the middle of the thermal stress relaxation layer to the vicinity of the internal thermal stress relaxation layer, and the heat of the surface layer The part from the vicinity of the stress relaxation layer to the middle of the thermal stress relaxation layer,
It is characterized in that a fiber layer in which one kind or two or more kinds of ceramic fibers are three-dimensionally composited is formed near either the thermal stress relaxation layer of the surface layer.

In a second aspect of the present invention, the ceramic constituting the surface layer is made of one of aluminum oxide, magnesium oxide, yttrium oxide, magnesium aluminum spinel, chromium oxide, titanium oxide, silicon oxide and mullite. The fiber forming the fiber layer is made of a fiber containing at least one selected from silicon carbide, silicon nitride and aluminum oxide as a main component, and the ceramic forming the inner layer is at least selected from silicon carbide, silicon nitride and sialon. It is characterized by being composed of one kind or two or more kinds of composite ceramics.

According to a third aspect of the present invention, there is provided a layered structure ceramic comprising a surface layer containing oxide ceramics as a main component and an inner layer containing non-oxide ceramics as a main component. Side part,
A central portion of the inner layer or a portion between the surface layer and the inner layer is reinforced with an oxide long fiber or a non-oxide long fiber.

According to a fourth aspect of the present invention, in a layered structure ceramics composed of a surface layer containing oxide ceramics as a main component and an inner layer containing non-oxide ceramics as a main component, the surface layer and the internal layer are provided. A ring-shaped ceramic fiber, a bow-shaped ceramic fiber that is convex toward the surface layer, or a corrugated ceramic fiber is compounded in such a manner that both layers are connected to the interface.

[0016]

First, the operation of the inventions of claims 1 and 2 will be described.

When the surface layer is made of oxide ceramics,
The internal non-oxide ceramics are not directly exposed to the oxidizing or corrosive atmosphere, and the oxidation resistance and corrosion resistance are greatly improved. However, if the surface layer is simply made to be an oxide, tensile residual stress is generated in the surface layer due to a difference in thermal expansion coefficient and the like, and cracks may occur or strength may be reduced.

Therefore, as a result of accumulating many experimental studies, these interfaces have a coefficient of thermal expansion intermediate between them.
It has been found that it is effective to have a layer, a thermal stress relaxation layer of two or more layers, or a thermal stress relaxation layer in which the composition of both changes continuously or discontinuously.

1 having an intermediate coefficient of thermal expansion between the two at the interface
Layer or two or more thermal stress relaxation layers, or by providing a thermal stress relaxation layer in which the composition of both changes continuously or discontinuously, the continuity of physical properties such as thermal expansion coefficient and elastic modulus However, it is possible to use it at a temperature around 1500 ° C or higher and in an oxidative and corrosive atmosphere. Is not enough.

Therefore, (1): a portion extending from the vicinity of the thermal stress relaxation layer of the surface layer to the vicinity of the interface portion of the internal layer via the thermal stress relaxation layer, (2): the thermal stress of the internal layer from the middle of the thermal stress relaxation layer (3): Part of the surface layer near the thermal stress relaxation layer to the middle of the thermal stress relaxation layer, (4): Both parts of (2) and (3), or (5): A material that can be used under such harsh conditions is to form a fiber layer in which one or more ceramic fibers are three-dimensionally composited between (2) and the thermal stress relaxation layer of the surface layer. It has been found to be effective in realizing In this case, three-dimensional means that the fibers are arranged both parallel and perpendicular to the interface.

Since the fibers arranged in the direction perpendicular to the interface and across the interface are present over the different layers, they connect the two and serve to increase the consistency at the interface. Further, the fibers arranged in the direction parallel to the interface stop the progress and opening of the cracks when the surface layer (oxide layer) is cracked by flying objects, etc. Layer) and plays a role in preventing rapid oxidation from occurring. That is, even if a crack is generated on the surface of the oxide, the crack is designed to stop in the middle of the oxide or at least at the interface between the oxide and the non-oxide (stress relaxation layer).

The arrangement of the fibers is set to the above-mentioned (1) to (5) because, when only the effect of the fibers is considered, from the vicinity of the interface portion (thermal stress relaxation layer) of the surface layer to the interface portion and the inside. It may be inserted near the interface of the layer. However, putting such a layer of long fibers in a ceramic material does not necessarily mean so-called strengthening as has been conventionally said, and especially at high temperature, rather than increasing the strength of the entire material, rather than increasing the strength of the entire material. It may even be lowered slightly.

Therefore, when designing a material in which high strength is strongly kept in mind, it may be effective to use a small amount of fiber layers. At this time, the fiber layer may be inserted either from the middle of the interface (thermal stress relaxation layer) to the vicinity of the interface of the inner layer or from the vicinity of the interface of the surface layer to the middle of the interface. Depending on the combination of materials,
In some cases, it is preferable to put a fiber layer in both of them and to have a structure in which the fiber layer is not provided at the center of the interface.

When the fibrous layer is inserted from the middle of the interface to the vicinity of the interface of the inner layer, when the crack stops at the interface, the interface reacts with the atmospheric gas, and the crack propagates. It is necessary to design the composition and the like of the interface portion so as not to cause this. When the fiber layer is inserted from the middle of the interface part to the vicinity of the interface part of the inner layer, it is also effective to insert the fiber layer near the interface part of the surface layer.

The reason why the ceramic fiber is made of one kind or two or more kinds is that, as described above, the role of the fiber layer is to maintain the consistency of the interfaces between different kinds of ceramics and to prevent the crack growth. It is also effective to add fibers suitable for the role of. For example, fibers arranged in the direction parallel to the interface and fibers arranged in the direction perpendicular to the interface are changed according to their respective roles (that is, a three-dimensional structure is formed by two or more kinds of fibers), or a fiber layer is put over two layers. Sometimes it is effective to change the fibers that make up each.

Therefore, it is not necessary to insert the fibers as in the conventional case, but the present invention plays two roles of the effect of the fibers to make the interfaces of different ceramics consistent with each other and the prevention of crack propagation. Focusing on that, he clarified the combination of arrangement and constituent materials to realize it.

As a specific material applied to such a structure, the surface layer is one of aluminum oxide, magnesium oxide, yttrium oxide, magnesium-aluminum spinel, chromium oxide, titanium oxide, silicon oxide and mullite. Is the basic idea of the present invention, at a temperature of around 1500 ° C. or higher and in an atmosphere of oxidative corrosion, keeping in mind that it is a material that can be used, in such an environment, This is the result of experimentally selecting a material that can play its role in a sufficiently stable manner, and that can achieve the intended effect with compatibility with the fiber layer and the inner layer described below. of course,
It is needless to say that each substance also has its own characteristic. For example, when the atmosphere contains a specific impurity, a suitable constituent material is selected in consideration of the reactivity with the impurity. It was also found that sialon, which is an oxynitride, is also effective as the surface layer when the corrosive atmosphere is not so strong. However, it is a condition that it is a pure sialon containing no rare earth element.

The fibers constituting the fiber layer are mainly composed of at least one selected from silicon carbide, silicon nitride and aluminum oxide because of their stability at high temperatures, crack growth inhibiting ability, strength and the like. In addition, it is the result of the experimental selection and selection.

The reason why the inner layer is made of at least one type or two or more types of composite ceramics selected from silicon carbide, silicon nitride and sialon is that they are selected experimentally on the basis of strength and stability at high temperature.

The invention according to claim 3 relates to a ceramic material which satisfies both strength and toughness at high temperature and oxidation resistance which have hitherto been incompatible, and fracture damage resistance for preventing catastrophic fracture in advance. It can be applied to high temperature structural members such as gas turbines.

In the present invention, the basic structure is a layered structure in which the surface layer of non-oxide ceramics is covered with oxide-based ceramics. In addition to the strength, toughness, and resistance to oxidation at the same time, it simultaneously achieves fracture damage resistance characteristics that prevent fracture due to catastrophic crack growth. There are several means for the form and arrangement of such long fibers, which will be described below.

That is, the portion of the inner layer on the surface layer side, that is, the non-oxide layer immediately below the oxide layer is reinforced with the non-oxide long fibers. In addition, the central portion of the non-oxide layer side is composite reinforced with non-oxide long fibers.

In this case, preferably, a plurality of layered non-oxide long fiber reinforced layers are compounded in the non-oxide layer, and the oxide layer in the surface layer portion is made of oxide long fibers or non-oxide long fibers. Combine to strengthen.

Further, the surface layer oxide layer is composite reinforced with oxide long fibers, and the non-oxide layer is composite reinforced with non-oxide long fibers,
Alternatively, except for the surface layer portion, the oxide layer and the non-oxide phase or different non-oxide layers are compositely reinforced with non-oxide type long fibers across the layers.

More preferably, long fibers are compounded across the layers of the oxide layer and the non-oxide layer, and the long oxide fibers are on the oxide layer side and the non-oxide long fibers are on the non-oxide side. Are arranged. Thereby, the above-mentioned characteristics are simultaneously realized.

In the invention of claim 4, since the fibers are compounded at the interface between the surface layer of the oxide ceramics and the inner layer of the non-oxide ceramics, the interface is strengthened and the oxide and the non-oxidized layer are mixed. Even if a crack enters the interface with the object, the two do not instantly separate and the fracture energy increases. At this time, when a ring-shaped fiber is used, the stress applied to the fiber is dispersed because it is ring-shaped, the fiber is less likely to break, and when the fiber is compounded into an arc shape or a wavy shape,
The elastic force of the fiber also has the effect of preventing crack opening on the surface. Furthermore, if the fiber is composed of oxide and non-oxide,
By arranging the oxide portion on the oxide ceramic side of the surface layer and the non-oxide portion on the non-oxide ceramic side of the inner layer, the oxidation resistance and the corrosion resistance are further improved.

[0037]

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

Example 1 (FIGS. 1 to 3, Tables 1 and 2) FIG. 1 is a schematic view of a cross section of a ceramic according to this example. FIG. 1A shows a configuration example of the first embodiment, in which a surface layer 1 containing oxide ceramics A as a main component, an inner layer 2 containing non-oxide ceramics B as a main component, and an interface between these The thermal stress relaxation layer 3 is formed, and the thermal stress relaxation layer 3 has a graded composition in which the composition of both ceramics A and B changes continuously or discontinuously. The same figure (b) is the second
The following is an example of the configuration of the above, wherein the thermal stress relaxation layer 3 has a plurality of layers of ceramics C having an intermediate coefficient of thermal expansion between the surface layer 1 and the inner layer 2.
It is composed by.

Table 1 is an application of the type shown in FIG. 1A, and shows the constitution of the surface layer, fiber layer and inner layer shown in the table.
Samples up to 24 were prepared.

At the interface portion which becomes the thermal stress relaxation layer 3, the composition of the surface layer 1 and the internal layer 2 (oxide ceramics A
And non-oxide B) were changed by 10 wt% to form a total of 9 layers. When the inner layer 2 is made of silicon carbide (SiC), when boron (B) and carbon (C) are added as 1 wt% each as a sintering aid and silicon nitride (Si ₃ N ₄ ) is made, , 5% by weight of Yb ₂ O ₃ and HfO as sintering aids
₂ 2 wt% were added and when a sialon, z =
The Si ₃ N ₄ to 0.5 by adding Al ₂ O ₃ and AlN.

Then, predetermined powders were mixed by a ball mill so that the composition of each of the thermal stress relaxation layers 3 constituting the inner layer 2 and the interface portion was obtained, and dried to obtain a mixed powder as a starting material. These respective powders and the powders of the respective materials constituting the surface layer 1 were dispersed in water to prepare respective slurries.

At the time of manufacture, a rectangular mold (50 × 60 mm) made of gypsum was prepared, and the slurry constituting the inner layer 2 was poured into the mold for casting. A preform obtained by three-dimensionally knitting continuous fibers containing SiC as a main component is placed on this molded body, and the rest of the slurry that forms the inner layer 2 and then the thermal stress relaxation layers 3 that form the interface are formed. The slurry and finally the slurry of the oxide constituting the surface layer 1 are sequentially poured, and moisture is sucked to perform molding. This is repeated as shown in (1) of FIG. A multilayer molded body having a fiber layer 4 arranged so as to cross the thermal stress relaxation layer 3 from above to reach the thermal stress relaxation layer 3 of the inner layer 2 was obtained.

These molded bodies were hot pressed under the conditions of 1700 ° C., a pressing pressure of 400 kg / cm ² and 120 minutes.
However, when SiC is used as the inner layer 2, the surface layer 1 is
If other than iO ₂ , set the hot press temperature to 1900 ° C,
When the surface layer 1 was made of SiO ₂ , the atmosphere was set at 1800 ° C. with argon at 9.5 atm.

The atmosphere was nitrogen when the inner layer 2 was Si ₂ N ₄ and sialon, and was argon when the inner layer 2 was SiC. These samples were subjected to HIP treatment under the conditions of 1700 ° C., 2000 atmospheric pressure and 30 minutes. Gas is the same as above
Was Si ₃ N ₄ and sialon, nitrogen was used, and SiC was argon.

The obtained sintered body sample is 4 mm × 3 mm × 40 mm
Was processed into a test piece of and the strength was determined at 1500 ° C. and 1550 ° C. by a three-point bending test based on JIS. However, the measurement was carried out by setting so that tensile stress was applied to the oxide side which becomes the surface layer 1. As a result of this measurement, as shown in Table 1, it was confirmed that all the samples had high strength.

For each test piece of the same size,
After Vickers indentation was applied to the center of the surface layer 1 with a load of 1 kg, a bending test was carried out by setting the surface layer 1 side so that tensile stress was applied in the same manner as above, and the load-displacement curve at that time was recorded. As schematically shown in FIG. 3, this curve represents the load when the crack starts to move from the indentation (point D) and the load when the crack is stopped by the fiber layer 4 (point E). Subsequent loads will be almost constant. The ratio of the two loads was calculated as R (%), and the results are shown in Table 1. It is shown that the larger the value of R, the larger the crack growth inhibiting ability of the fiber layer 4. When the fiber layer 4 is not present, the brittle fracture occurs, so that the point E does not appear and the load drops, so the value of R becomes almost zero.

From these results, it was revealed that the layered structure ceramics according to the structure of this example exhibited excellent strength at a very high temperature of 1500 ° C. or higher and also had excellent crack growth inhibiting ability.

Table 2 shows, as a comparative example to this embodiment,
Samples without the thermal stress relaxation layer 3 or the fiber layer 4 were tested as 1a to 16
The result when a is manufactured by the same method as this example and evaluated by the same method as Example 1 is shown.

When the thermal stress relaxation layer 3 of FIG. 1A is included but the fiber layer 4 is not included (Samples 1a to 8a), the value of R becomes zero, but not only that, but also the strength is Compared with the case where the fiber is included, the amount is obviously lower. This is because the conformity at the interface is insufficient, and it is understood that the effect is small with only the thermal stress relaxation layer 3 at the interface. However, when the surface layer 1 is made of magnesium oxide, yttrium oxide, magnesium aluminum spinel, chromium oxide, titanium oxide, or silicon oxide, it is lower than that in combination with the fiber layer 4, but other aluminum oxide or mullite is used. It was also found that it retains some strength as compared with the case of. For this, the inner layer 2
However, when the inner layer 2 is made of SiC, even when the surface layer 1 is made of aluminum oxide or mullite, the same strength level as other surface layers is obtained. It was

From Table 2, when the interface portion does not include the thermal stress relaxation layer 3 but only the fiber layer 4 (Samples 9a to 16a), the strength is lowered and the effect of preventing the crack growth by the fiber layer 4 is very high. It turns out to be low.

Example 2 (Table 3) Samples having the constitution shown in Table 3 were prepared in the same manner as in Example 1 and evaluated. Here, the results of changing the types of fibers, the arrangement of the fiber layers 4, etc. are shown.

The arrangement of the fiber layer 4 is shown in FIG.
The arrangements schematically shown in (5) to (5) are applied. That is,
The type of the fiber layer 4 is (1): a portion extending from the vicinity of the thermal stress relaxation layer 3 of the surface layer 1 to the vicinity of the thermal stress relaxation layer 3 of the inner layer 2, (2)
: A portion extending from the middle of the thermal stress relaxation layer 3 to the vicinity of the thermal stress relaxation layer 3 of the inner layer 2, (3): A portion extending from the vicinity of the thermal stress relaxation layer 3 of the surface layer 1 to the middle of the thermal stress relaxation layer 3, ( 4): (2) (3)
, Or (5): (2) and one or more kinds of ceramic fibers are three-dimensionally composited in the vicinity of the thermal stress relaxation layer 3 of the surface layer 1. The thermal stress relaxation layer 3
1 has the gradient composition shown in FIG. 1A as in the first embodiment.

The sample 27 of this example has a structure in which fibers containing Si ₃ N ₄ as a main component are arranged in the direction perpendicular to the interface, and fibers containing SiC as a main component are arranged in the parallel direction. The preform of is used. Further, as to the sample 28 of this example, a preform composed of fibers containing SiC as a main component in a direction perpendicular to the interface and fibers containing Al ₂ O ₃ as a main component in the parallel direction was used. .

In the sample 33, the thermal stress relaxation layer 3 of the surface layer 1 was used.
A fiber containing Al ₂ O ₃ as a main component is arranged between the vicinity of the thermal stress relaxation layer 3 and SiC as a main component from the middle of the thermal stress relaxation layer 3 to the vicinity of the thermal stress relaxation layer 3 of the inner layer 2. It has a structure in which fibers are arranged. In addition, sample 34
Then, a fiber containing Al ₂ O ₃ as a main component is arranged near the thermal stress relaxation layer 3 of the surface layer 1, and SiC is provided from the middle of the thermal stress relaxation layer 3 to the vicinity of the thermal stress relaxation layer 3 of the inner layer 2. The fibers that are the main components are arranged.

According to this example, as in Example 1, the strength is high and the value of R is large, and it is recognized that the application to the high temperature member is effective.

Example 3 (Table 4) Samples having the constitution shown in Table 4 were prepared in the same manner as above,
An evaluation was made. The results are also shown in Table 4. Here, the structure of the thermal stress relaxation layer 3 has the intermediate composition shown in FIG.
That is, mullite was used as the thermal stress relaxation layer 3 having a thermal expansion coefficient intermediate between those of the surface layer 1 and the internal layer 2. Mullite 1
Instead of layers, between the mullite and the surface layer 1 and the inner layer 2, there was a three-layer interface portion in which layers each composed of 50% by weight were arranged.

As a result, it was revealed that even if the interface portion was constituted by the third component other than the surface layer and the inner layer, excellent results were obtained at high temperatures.

Example 4 (FIGS. 4 to 7) FIG. 4 schematically shows a layered composite ceramic according to an example.

In this embodiment, the surface layer 1 is made of alumina (Al which is an oxide ceramic having excellent heat resistance and corrosion resistance).
₂ O ₃ ), mullite (3Al ₂ O ₃ · 2SiO ₂ ), M
gO, Y ₂ O ₃ , MgAl ₂ O ₄ , Cr ₂ O ₃ , TiO
_2, consists of SiO ₂ or the like, preferably alumina or mullite.

The inner layer 2 has strength, toughness, and
Si, which is a non-oxide ceramic with excellent thermal shock resistance
₃ N _4, SiC, consists sialon and the like, preferably S
i ₃ N ₄ layer.

The thermal stress relaxation layer 3 is, for example, the surface layer 1.
In order to relieve internal stress at the interface between the inner layer 2 and the inner layer 2, a basic structure is a laminated structure composed of a graded composition or the like. Further, in the embodiment, the heat resistance of the inner layer 2 immediately below the surface layer 1 is improved. The fiber layer 4 is formed of a fiber composite ceramic that is composite-reinforced with SiC-based non-oxide ceramic long fibers such as Nicalon.

The long fibers used here may be a stack of one-dimensional fibers, a laminate of two-dimensionally knitted ones, or a three-dimensionally knitted one, but more preferably two-dimensionally knitted ones. It is a dimensional or three-dimensional knit.

The thicknesses of the surface layer 1 and the fiber layer 4 are 15% or less and 50% or less, respectively, of the total thickness of the constituent layers, and preferably the fiber layer 4 is 5 to 40%. These layers are
If it is too thick, the strength of the layered structure will be reduced, and if it is too thin, it will not serve its role in terms of oxidation resistance or prevention of crack growth.

The manufacturing method will be described below.

An example is shown in which Al ₂ O ₃ is applied as the oxide ceramics forming the surface layer 1 and Si ₃ N ₄ is applied as the non-oxide ceramics forming the inner layer 2. α
Type or β type silicon nitride powder as a sintering aid, for example, 5 wt%
Yb ₂ O ₃ +2 wt% HfO ₂ +3 wt% AlN is added and uniformly wet mixed in a ball mill, then dried and sieved to prepare a mixed powder. The mixed powder is put into a mold and molded into a predetermined size with a light molding pressure. For example, Al ₂ O ₃ used as the surface layer 1 also has a thickness of 15% of the total layer thickness during sintering.
Weigh as follows and lightly mold to the same size.

Further, the SiC long fiber preform is
A molded body is prepared by impregnating a powder in which ₃ N ₄ or Si ₃ N ₄ and Al ₂ O ₃ are mixed in an appropriate ratio. The total fiber content should be approximately 30% by volume. A carbon mold having the same cross-sectional area is prepared, first, Si ₃ N ₄ is placed, a long-fiber composite molded body is stacked thereon, and an Al ₂ O ₃ molded body is further stacked thereon, and the whole is pressed and pressed again.

The laminated body formed in this manner is treated with N
_{In a 2} atmosphere, hot press sintering is performed at 1700 ° C. to obtain a sintered body. The hot press pressure is 300 kg / cm ² . Furthermore, under N ₂ gas atmosphere, 1700 ° C., 2000 atn
HIP processing was performed on the conditions of.

In this example, the obtained sintered body was processed into a JIS-R1601 bending test piece such that the laminating direction was the thickness direction. A three-point bending strength test from room temperature to 1500 ° C. was performed with the Al ₂ O ₃ side of this test piece as the lower surface to obtain the relationship between fracture strength and stress-strain.

FIG. 5 shows the strength of the laminated sintered body against the test temperature.
Is indicated by the characteristic line F. Although the strength decreases with increasing test temperature, 600MP even at 1500 ℃
It has strength exceeding a. This is considered to be an effect due to the improvement of heat resistance and oxidation resistance due to the oxide of the surface layer 1.

In FIG. 6, the breaking behavior is schematically shown by a characteristic line G. Due to the effect of the long fiber composite, the fracture did not cause catastrophic fracture and exhibited a stable crack growth pattern. The cracks that have entered the surface layer 1 have stopped once, and the load is further increased with slow progress. Although a little unstable fracture was shown after the maximum load, the stability of the material according to the present example is clearly recognized as compared with the characteristic line H of catastrophic fracture of the conventional material shown in FIG.
In addition, the result of the impact test showed that the materials did not fall apart and the fracture damage resistance was high.

Example 5 (FIGS. 8 to 9) FIG. 8 schematically shows a fiber composite type layered structure ceramics according to this example. The structure of this embodiment is similar to that of the fourth embodiment, but the difference is that the central portion of the non-oxide ceramic as the inner layer 2 is composite reinforced by the fiber layer 4.

1500 of a sintered body having such a structure
The characteristic curve I is schematically shown in FIG. 9 for the fracture behavior at a high temperature of ° C. As shown in the figure, the material of this example showed a relatively high strength, and the development of cracks accompanied by a rapid load drop for a moment after the maximum load was hindered by the fibers, and a particularly large fracture resistance was exhibited.

Example 6 (FIGS. 10 and 11) FIG. 10 schematically shows a fiber-composite layered structure ceramics according to this example.

In this embodiment, three reinforcing fiber layers 4 are formed in the inner layer 2. In manufacturing such ceramics, a carbon mold is used, for example, in Example 4.
Put the Si ₃ N ₄ mixed powder containing the auxiliary agent prepared in the same manner as above, press lightly, put the two-dimensionally or three-dimensionally knitted long fiber, put Si ₃ N ₄ / Al ₂ O ₃ mixed powder, and A long fiber is placed, and a Si ₃ N ₄ / Al ₂ O ₃ mixed powder is placed.

Then, Si ₃ N ₄ / Al ₂ O ₃ was gradually changed, this was repeated several times, and finally 100% Al ₂ O _{3 was} added.
Form the layers. After that, it is strongly mechanically pressed to be integrally molded, and hot pressed and sintered at 1700 ° C. in an N ₂ atmosphere.

With respect to the layered structure ceramic having three fiber layers 4 thus produced, the test temperature was 1500.
The stress-strain relationship at ° C is schematically shown in Fig. 11. As shown by the characteristic line J in the figure, the fracture behavior was almost the same as in Example 4 up to the maximum load, but thereafter, the progress-stoppage of the fracture was repeated according to the number of fiber layers. The fiber layer 4 was confirmed to have an effect of effectively suppressing the development of cracks generated from the surface layer 1.

Example 7 (FIGS. 12 to 14) FIG. 12 schematically shows a fiber composite type layered structure ceramics according to this example. In this embodiment, a fiber layer 4 is formed on the surface layer 1 by a cloth made of long fibers for the purpose of reinforcing an oxide ceramic material having poor mechanical properties.

FIG. 12 shows the manufacturing method thereof. For example, on a sintered body 2a of Si ₃ N _4, a preform 4a is made of a cloth in which Al ₂ O ₃ long fibers are woven, and then Al ₂
Impregnate oxide slurry 1a such as O ₃ or mullite,
The fiber-reinforced oxide ceramic layer as the surface layer 1 was formed by performing heat treatment at 00 to 1500 ° C.

A JIS-R1601 test piece was cut out from the produced sintered body, and a bending test was conducted at a test temperature of 1500 ° C. with the oxide ceramic layer on the tensile side. The stress-strain curve at that time is schematically shown in FIG.

As indicated by the characteristic line K in the figure, the strength characteristics are improved by strengthening the surface layer 1, and the fiber layer 4 works so as to suppress the fluidity of Al ₂ O ₃ , and the fracture resistance is slightly increased. After that, the Si ₃ N ₄ transitions to fracture due to the grain boundary slip. In this case as well, the long fibers work as an effect of suppressing crack growth. Even if the oxide-based long fibers were replaced with non-oxide-based long fibers, a larger effect could be expected in terms of mechanical properties, but a sharp decrease due to oxidation and corrosion of the fibers was observed after the cracks once occurred.

Example 8 (FIGS. 15 and 16) FIG. 15 schematically shows a fiber composite type layered structure ceramics according to this example.

The present invention has a structure in which the fourth or fifth and sixth embodiments and the seventh embodiment are combined. Figure 15 shows is an example of combining the Example 4 and Example 7, for example, Al ₂ Al reinforced with O ₃ long fiber ₂ O ₃ layer 4A and Si ₃ reinforced by SiC filament It is a laminated material with N ₄ 4B.

FIG. 16 schematically shows the stress-strain relationship. As shown by the characteristic line L in the figure, Al ₂ O _{3 is used.}
When the layer 4A and the Si ₃ N ₄ layer 4B are broken, the fiber composite effectively acts, and is characterized by maintaining the strength and increasing the breaking energy.

Example 9 (FIGS. 17 and 18) FIG. 17 schematically shows the fiber-composite layered structure ceramics according to this example. As shown in the figure, in this embodiment, the fiber layer 4 is compounded across the surface layer 1 made of oxide ceramics and the inner layer 2 made of non-oxide ceramics. For example, the surface layer 1 is Al
₂ O ₃ , the inner layer 2 is made of Si ₃ N ₄ , and SiC long fibers are compounded between these two layers.

FIG. 18 is a schematic view of a slip cast-based manufacturing method. For example, the Al ₂ O ₃ slurry 1b is injected into the SiC long fiber preform 4b placed in the mold 5 and dehydrated to form the first layer, and then the Si ₃ N ₄ slurry is overlapped and injected, followed by dehydration to the second. Form the layers. However, the surface layer 1 was an Al ₂ O ₃ 100% layer.

In the ceramics manufactured by such a method, it is possible to form a structure between the Al ₂ O ₃ and Si ₃ N ₄ layers having a graded composition by slightly changing the composition of both.

The obtained molded body was degreased and hot pressed and sintered at 1700 ° C. The fracture characteristics of this material are shown in Example 4.
It was almost the same as that shown in. On the other hand, this structure has a feature that stress generated by a physical property mismatch between two different layers can be relaxed, and is promising in the future.

Example 10 (FIG. 19) FIG. 19 schematically shows the fiber-composite layered structure ceramics according to this example. The features of this embodiment are similar to those of the ninth embodiment, and the basic structure is almost the same.

However, the oxide-based long fiber layer 4 is used as the surface layer 1.
C and the inner layer 2 are formed by braiding long fibers so that a non-oxide long fiber layer 4D is formed.

According to such a structure, even if a crack is formed in the oxide layer, it will not immediately lead to material deterioration. For example, Al ₂ O ₃ fiber-Al ₂ O ₃
/ The SiC fibers -Si ₃ N ₄ was prepared a laminate in Examples. The manufacturing method and mechanical properties were almost the same as in Example 9. As for the oxidation characteristics, it showed better characteristics.

Example 11 (FIG. 20, Table 5) In the layered structure ceramics of this example, the fibers 6 were formed at the interface between the silicon nitride as the inner layer 2 as the substrate and the oxide ceramics as the surface layer 1. It is compounded. Since the surface layer 1 is formed of an oxide having excellent oxidation resistance and corrosion resistance, it prevents the substrate from being directly exposed to an oxidizing or corrosive atmosphere. Also, the fiber at the interface increases the failure energy.

The thickness of the surface layer 1 is 2 times the total thickness of the sintered body.
It is preferably 0% or less. A certain amount of thickness is required to fully exhibit the original high oxidation resistance and other effects of surface layer 1, but if it exceeds 20%, the effect of the surface layer will increase and the strength of the sintered body will increase. And toughness decreases.

The sintered body of this example was obtained by stacking oxide raw material powder, silicon nitride powder, and fibers in a mold,
It can be formed by molding and sintering. When the fiber 6 is a whisker, a predetermined amount is compounded with a powder which is a matrix, and the powder obtained by mixing with a ball mill is laminated in the same manner as described above.

Further, yttria (Y ₂ O ₅ ) and alumina (Al ₂ O ₃ ) as a sintering aid are mixed with the silicon nitride powder which is a raw material of the inner layer 2 by a ball mill.

In producing the sintered body of this example using the raw material thus prepared, first, a mold of an arbitrary shape is filled with silicon nitride powder for forming a substrate.
Then, a powder in which whiskers are compounded or an oxide powder is laminated with fibers, and a preform is prepared by cold pressing. The obtained preformed body is hot-press sintered to obtain the sintered body of this example. Hereinafter, the present embodiment will be specifically described.

Alumina powder, titania (TiO ₂ ) powder, spinel (MgAl ₂ O ₄ ) powder, magnesia (MgO) powder, chromia (Cr ₂ O ₃ ) powder and yttria powder were used as raw materials for the layered structure ceramics of this example. And silicon nitride powder was used. Silicon carbide (SiC) long fibers are used for the fiber 6, and silicon nitride, which is the substrate, is
As a sintering aid, yttria 5 wt% and alumina 2
Weight% was added and mixed using a ball mill.

A laminate was prepared using the above oxide powder, silicon nitride powder, and silicon carbide fiber. First, a silicon nitride powder serving as the inner layer 2 is filled in a mold having an arbitrary shape, and the ring-shaped fiber 6 is perpendicular to the bottom surface of the mold,
The fibers are arranged so that they are parallel to each other. The oxide powder which is the surface layer 1 is filled from above and cold pressed to obtain a molded body. Then, hot press sintering was performed in a carbon mold to obtain a sintered body sample.

The sintering conditions are a sintering temperature of 1800 ° C., a pressing pressure of 30 MPa, and a sintering temperature holding time of 1 hour. The atmosphere was 1 MPa nitrogen. The obtained sintered body,
4 mm x 3 m so that the surface layer and the substrate are provided in the thickness direction.
A test piece of m × 40 mm was processed and used as a sample.

FIG. 20 schematically shows a cross-sectional state of the obtained ceramic sintered body, which is taken by a micrograph. A ring-shaped silicon carbide fiber 6 is provided at the interface between the inner layer 2 made of silicon nitride ceramics and the surface layer 1 made of oxide ceramics.

Example 12 (FIG. 21, Table 5) In this example, instead of the silicon carbide fiber at the interface of Example 11, silicon carbide-alumina fiber 6 was applied, and the same method as in Example 11 was applied. A laminated body was produced. At this time, the alumina portion 6a of the fiber 6 is located on the oxide ceramics of the surface layer 1, and the silicon carbide portion 6b of the fiber 6 is located on the silicon nitride of the inner layer 2.

FIG. 21 schematically shows a cross-sectional state of the obtained layered structure ceramics, which is taken by a micrograph. A composite ring-shaped silicon carbide-alumina fiber 6 is arranged at the interface between the silicon nitride ceramics of the inner layer 2 and the oxide ceramics of the surface layer 1.

Example 13 (FIG. 22, Table 5) In this example, fibers 6c are formed in an arc shape and are combined. Other configurations are almost the same as those of the eleventh and twelfth embodiments. In the production, the fibers 6c compounded so as to have a large radius of curvature were positioned inside the fiber 6c compounded so as to have a small radius of curvature on the surface perpendicular to the bottom surface of the carbon mold.

FIG. 22 schematically shows an image of a cross section of the obtained ceramic, taken by a micrograph. As shown in the figure, at the interface between the silicon nitride ceramics of the inner layer 2 and the oxide ceramics of the surface layer 1, silicon carbide fibers 6c which are compounded in an arc shape are arranged.

Example 14 (FIG. 23, Table 5) In this example, the fiber 6d is silicon carbide-alumina fiber. The other structure is the same as that of the thirteenth embodiment. At the time of fabrication, the alumina portion of the fiber 6d is located on the oxide ceramic side of the surface layer 1, and the silicon carbide portion of the fiber 6d is located on the silicon nitride side of the inner layer 2.

FIG. 23 schematically shows an image of a cross section of the obtained ceramic, taken by a micrograph. As shown in the figure, at the interface between the silicon nitride ceramics of the inner layer 2 and the oxide ceramics of the surface layer 1, a silicon carbide-alumina fiber 6 which is composited in an arc shape is formed.
d is arranged.

Example 15 (FIG. 24, Table 5) In this example, the fiber 6e is a corrugated silicon carbide fiber. The other structure is the same as that of the eleventh embodiment. At the time of manufacture, the fibers 6e with the corrugated phase of which the phase is changed are arranged so as to be stacked on the surface perpendicular to the bottom surface of the carbon mold.

FIG. 24 is a schematic diagram showing an image of a cross section of the obtained ceramic, taken by a micrograph. As shown in the figure, a composite corrugated silicon carbide fiber 6e is arranged at the interface between the silicon nitride ceramics of the inner layer 2 and the oxide ceramics of the surface layer 1.

Example 16 (FIG. 25, Table 5) In this example, the fiber 6f is a corrugated silicon carbide-alumina fiber. Other configurations are the same as those of the fifteenth embodiment.
Is the same as. In the production, the alumina portion of the fiber 6f is arranged on the oxide side of the surface layer 1, and the silicon carbide portion of the fiber 6f is arranged on the silicon nitride side of the inner layer 2.

FIG. 25 schematically shows an image of a cross section of the obtained ceramic, taken by a micrograph. As shown in the figure, the corrugated silicon carbide-alumina fiber 6f is compounded at the interface between the silicon nitride ceramics of the inner layer 2 and the oxide ceramics of the surface layer 1.
Has been placed.

Comparative Example (FIG. 26, Table 6) In this example, fibers were not compounded at the interface. Otherwise, the configuration and manufacturing method are the same as in Example 11 above.

FIG. 26 schematically shows an image of a cross section of the obtained ceramic, taken by a micrograph. As shown in the figure, the silicon nitride ceramics of the inner layer 2 and the oxide ceramics of the surface layer 1 form a layered structure.

Example 17 (FIGS. 27 and 28, Table 7) In this example , as the ceramic raw material, alumina powder,
Alumina whiskers, silicon nitride powder, and silicon nitride whiskers were used. 5% by weight of yttria and 2% by weight of alumina were added to the silicon nitride as the inner layer 2 as a sintering aid, and they were mixed using a ball mill.

The intermediate layer as the thermal stress relaxation layer 3 in which the composition of alumina and silicon nitride changes in a gradient,
Alumina powder and silicon nitride whiskers, or alumina whiskers were mixed with the above silicon nitride powder using a ball mill. At this time, whiskers were used for the one having a relatively low mol% compared to alumina and silicon nitride, and conversely, a normal powder was used for the one having a relatively high mol%.

The above alumina powder, alumina whiskers,
Using silicon nitride powder and silicon nitride whiskers,
The method for producing the layered structure ceramics is as follows. First, a mold having an arbitrary shape is filled with silicon nitride powder serving as a substrate as the inner layer 2. An intermediate layer to be the thermal stress relaxation layer 3 is laminated thereon so that the composition gradually changes, and finally the alumina powder of the surface layer 1 is filled and cold pressed to obtain a molded body.

Then, hot press sintering is carried out in a carbon mold to obtain a sintered body sample. Sintering conditions are sintering temperature 1
The temperature is 800 ° C., the pressing pressure is 30 MPa, and the sintering temperature holding time is 1 hour. The atmosphere is, for example, 1 MPa nitrogen. The obtained sintered body is processed into a test piece of 4 mm × 3 mm × 40 mm so that the surface layer 1 and the inner layer 2 are laminated in the thickness direction, and used as a sample.

FIG. 27 schematically shows a cross-sectional state of the obtained ceramics, which is taken by a micrograph. As shown in the figure, an intermediate layer as a thermal stress relaxation layer 3 whose composition changes in a gradient is formed at the interface between the silicon nitride ceramics of the inner layer 2 and the alumina ceramics of the surface layer 1. In the intermediate layer, silicon nitride whiskers 7 and alumina whiskers 8 are dispersed together with the alumina ceramic particles 1 and the silicon nitride ceramic particles 2 '.

Further, FIG. 28 shows the results of examining the element distribution of aluminum (Al) and silicon (Si) near the interface by EPMA. Aluminum is the amount of alumina,
Further, silicon means the amount of silicon nitride.

Comparative Example (FIG. 29) In this comparative example, the alumina whiskers and silicon nitride whiskers used for the intermediate layer were ordinary alumina powder and silicon nitride powder, respectively. A sintered body was obtained in the same manner as in Example 17.

FIG. 29 is a schematic view showing an image of a cross section of the obtained ceramic, taken by a micrograph. As shown in the figure, an intermediate layer as a thermal stress relaxation layer 3 is formed at the interface between the silicon nitride ceramics of the inner layer 2 and the alumina ceramics of the surface layer 1, and the silicon nitride particles 9 and Alumina particles 1
0 is dispersed.

Example 18 (FIG. 30, Table 7) In this example, a ring-shaped silicon carbide fiber was added to the intermediate layer of Example 17 in the same manner as in Example 11, and the same procedure as in Example 17 was performed. The sintered body was obtained by the method of.

FIG. 30 is a schematic view showing an image of a cross section of the obtained ceramic, taken by a micrograph. As shown in the figure, an intermediate layer as a thermal stress relaxation layer 3 is formed at the interface between the silicon nitride ceramics of the inner layer 2 and the alumina ceramics of the surface layer 1, and the silicon nitride whiskers 7 and the alumina whiskers 8 are formed in the intermediate layers.
And ring-shaped silicon carbide fibers 6 are dispersed.

Example 19 (FIG. 31, Table 7) In this example, the intermediate layer of Example 17 was further compounded with ring-shaped silicon carbide-alumina fiber in the same manner as in Example 12 to prepare Example 17. A sintered body was obtained in the same manner as in.

FIG. 31 schematically shows an image of a cross section of the obtained ceramic, taken by a micrograph. As shown in the figure, an intermediate layer as a thermal stress relaxation layer 3 is formed at the interface between the silicon nitride ceramics of the inner layer 2 and the alumina ceramics of the surface layer 1, and the silicon nitride whiskers 7 and the alumina whiskers are formed in the intermediate layers. 8 and ring-shaped silicon carbide-alumina fibers 6 are dispersed.

Example 20 (FIG. 32, Table 7) This example was similar to Example 17 in that the intermediate layer of Example 17 was further compounded with silicon carbide fibers in the shape of an arc in the same manner as in Example 13. The sintered body was obtained by the method of.

FIG. 32 schematically shows an image of a cross section of the obtained ceramic laminate, taken by a micrograph. As shown in the figure, an intermediate layer as a thermal stress relaxation layer 3 is formed at the interface between the silicon nitride ceramics of the inner layer 2 and the alumina ceramics of the surface layer 1,
Silicon nitride whiskers 7, alumina whiskers 8 and bow-shaped composite silicon carbide fibers 6c are provided in the intermediate layer.

Example 21 (FIG. 33, Table 7) In this example, a silicon carbide-alumina fiber was compounded in an arc shape in the same manner as in Example 14 in the intermediate layer of Example 17 described above. A sintered body was obtained in the same manner as in.

FIG. 21 schematically shows an image of a cross section of the obtained ceramic, taken by a micrograph. As shown in the figure, an intermediate layer as a thermal stress relaxation layer 3 is formed at the interface between the silicon nitride ceramics of the inner layer 2 and the alumina ceramics of the surface layer 1, and the silicon nitride whiskers 7 and the alumina whiskers 8 are formed in the intermediate layers.
And silicon carbide-alumina fiber 6d composited in an arc shape
Are dispersed.

Example 22 (FIG. 34, Table 7) In this example, a corrugated silicon carbide fiber was further added to the intermediate layer of Example 17 in the same manner as in Example 15, and the same procedure as in Example 17 was performed. The sintered body was obtained by the method.

FIG. 22 schematically shows an image of a cross section of the obtained ceramic, taken by a micrograph. As shown in the figure, an intermediate layer as a thermal stress relaxation layer 3 is formed at the interface between the silicon nitride ceramics of the inner layer 2 and the alumina ceramics of the surface layer 1, and the silicon nitride whiskers 7 and the alumina whiskers 8 are formed in the intermediate layers.
And corrugated silicon carbide fibers 6e are dispersed.

Example 23 (FIG. 35, Table 7) This example is the same as the intermediate layer of Example 17 except that Example 16 was used.
In the same manner as in the above, composite arcuate silicon carbide-alumina fibers,
A sintered body was obtained by the same method as in Example 17.

FIG. 23 schematically shows an image of a cross section of the obtained ceramic, taken by a micrograph. As shown in the figure, an intermediate layer as a thermal stress relaxation layer 3 is formed at the interface between the silicon nitride ceramics of the inner layer 2 and the alumina ceramics of the surface layer 1, and the silicon nitride whiskers 7 and the alumina whiskers 8 are formed on this intermediate layer. , And corrugated silicon carbide-alumina fibers 6f are dispersed.

Effects of Examples 11 to 23 For the samples 39 to 81 of Examples 11 to 23,
Each was subjected to a three-point bending test based on JIS to determine the breaking energy at room temperature. The strength was measured by setting the sample so that tensile stress was applied to the oxide ceramics side of the surface layer 1. The obtained measurement results are shown in Tables 5 and 7 together with the types and shapes of the oxide and the reinforcing fibers of the surface layer 1 of each sample. In Table 7, all oxides on the surface are alumina.

From Tables 5, 6 and 7, comparing each of Samples 39 to 81 of Examples 11 to 23 with each of Samples 39a to 44a of Comparative Example, the fact that the fibers are compounded at the interface increases the breaking energy. As a result, it can be seen that even if a crack enters the interface, the oxide layer and the silicon nitride layer are difficult to separate.

Next, the layered structure ceramics in each of the above examples were exposed to an oxidizing atmosphere to examine the oxidation resistance. It is most preferable to prepare a sintered body having an oxide surface layer on all the surfaces of the inner layer 2 made of silicon nitride, but it is considered that only one surface is sufficient to verify the oxidation resistance. Therefore, the ceramic sintered bodies of Examples 11 to 23 were used as samples for the oxidation resistance test. In addition, an oxide sintered body made only from the oxide raw material powder used for the surface layer was prepared as a comparative example.

Using the obtained sintered body as a sample, 1500 ° C.
The oxidation resistance test was performed for 1000 hours in the atmosphere. As a result, in the ceramic laminates of all the above examples,
As in the case of the oxide alone, the amount of increase in oxidation was sufficiently small, and the results of the oxidation resistance test were good.

From this, it is clear that the layered structure ceramics of this example has the same oxidation resistance as the oxide sintered body of the surface layer 1.

[0137]

[Table 1]

[0138]

[Table 2]

[0139]

[Table 3]

[0140]

[Table 4]

[0141]

[Table 5]

[0142]

[Table 6]

[0143]

[Table 7]

[0144]

As described in detail above, according to the present invention, at a temperature of 1500 ° C. or higher, it exhibits excellent strength and has an excellent ability to prevent the development of cracks. Since such an oxide is used, it is possible to obtain a material structure exhibiting oxidation resistance and corrosion resistance that can be used even in an environment where conventional non-oxides cannot withstand. Further, it is possible to obtain the layered structure ceramics having improved fracture energy and having the oxidation resistance and the corrosion resistance equivalent to those of the oxide ceramics, which are suitable for the structural material for high temperature.

[Brief description of drawings]

FIG. 1 shows Examples 1 to 3 of the present invention and is a schematic view of an interface structure.

FIG. 2 is a schematic diagram of a load displacement curve in the first embodiment.

FIG. 3 is a schematic diagram showing a total fiber arrangement in Example 1;

FIG. 4 is a diagram showing a sectional structure of a layered structure ceramics according to Example 4 of the present invention.

5 is a graph showing the influence of the test temperature on the strength of the layered structure ceramics according to Example 4. FIG.

FIG. 6 is a schematic diagram of the fracture behavior of the layered structure ceramics according to Example 4.

FIG. 7 is a schematic diagram showing a fracture behavior according to a conventional example as a comparison corresponding to the example.

FIG. 8 is a diagram showing a cross-sectional structure of a layered structure ceramics according to Example 5 of the present invention.

FIG. 9 is a schematic diagram showing the fracture behavior of the layered structure ceramics according to Example 5.

FIG. 10 is a diagram showing a cross-sectional structure of a layered structure ceramics according to Example 6 of the present invention.

FIG. 11 is a schematic diagram showing the fracture behavior of the layered structure ceramics according to Example 6.

FIG. 12 is a diagram showing a sectional structure of a layered structure ceramics according to Example 7 of the present invention.

FIG. 13 is a view showing a method for manufacturing a layered structure ceramics according to the seventh embodiment.

FIG. 14 is a schematic diagram showing the fracture behavior of the layered structure ceramics according to Example 7.

FIG. 15 is a diagram showing a sectional structure of a layered structure ceramics according to Example 8 of the present invention.

FIG. 16 is a schematic diagram showing the fracture behavior of the layered structure ceramics according to Example 8.

FIG. 17 is a diagram showing a cross-sectional structure of layered structure ceramics according to Example 9 of the present invention.

FIG. 18 is a view showing a method for producing a layered structure ceramics according to the ninth embodiment.

FIG. 19 is a diagram showing a sectional structure of a layered structure ceramics in accordance with Example 10 of the present invention.

FIG. 20 is a diagram schematically showing an image taken by a micrograph of the cross-sectional state of the layered structure ceramics of Example 11 of the present invention.

FIG. 21 is a diagram schematically showing an image taken by a micrograph of the cross-sectional state of the layered structure ceramics of Example 12 of the present invention.

FIG. 22 is a diagram schematically showing a microscopic image of the cross-sectional state of the layered structure ceramics of Example 13 of the present invention.

FIG. 23 is a diagram schematically showing an image taken by a micrograph of the cross-sectional state of the layered structure ceramics of Example 14 of the present invention.

FIG. 24 is a view schematically showing a microscopic image of a cross-sectional state of the layered structure ceramics of Example 15 of the present invention.

FIG. 25 is a diagram schematically showing an image taken by a micrograph of the cross-sectional state of the layered structure ceramics of Example 16 of the present invention.

FIG. 26 is a diagram schematically showing an image taken by a micrograph of a cross-sectional state of a layered structure ceramic of a comparative example corresponding to the present invention.

FIG. 27 is a view schematically showing an image taken by a micrograph of the cross-sectional state of the layered structure ceramics of Example 17 of the present invention.

FIG. 28 shows the layered structure ceramics of Example 17,
The figure which shows the element distribution by EPMA analysis of the interface vicinity.

FIG. 29 is a diagram schematically showing an image taken by a micrograph of a cross-sectional state of a layered structure ceramic of a comparative example corresponding to the present invention.

FIG. 30 is a diagram schematically showing a microscopic image of a cross-sectional state of the layered structure ceramics of Example 18 of the present invention.

FIG. 31 is a diagram schematically showing an image taken by a micrograph of the cross-sectional state of the layered structure ceramics of Example 19 of the present invention.

FIG. 32 is a diagram schematically showing an image taken by a micrograph of the cross-sectional state of the layered structure ceramics of Example 20 of the present invention.

FIG. 33 is a diagram schematically showing an image taken by a micrograph of the cross-sectional state of the layered structure ceramics of Example 21 of the present invention.

FIG. 34 is a view schematically showing a microscopic image of a cross-sectional state of the layered structure ceramics of Example 22 of the present invention.

FIG. 35 is a diagram schematically showing an image taken by a micrograph of the cross-sectional state of the layered structure ceramics of Example 23.

[Explanation of symbols]

 1 Surface Layer 2 Inner Layer 3 Thermal Stress Relaxation Layer 4 Fiber Layer 1b Slurry 4b Long Fiber Preform 4C Oxide Long Fiber 4D Non-Oxide Long Fiber 5 Form 6 Ring Silicon Carbide Fiber 6 (6a, 6b) Ring-shaped silicon carbide-oxide fiber 6c Silicon carbide fiber composited in an arc shape 6d Silicon carbide-oxide fiber composited in an arc shape 6e Corrugated silicon carbide fiber 6f Corrugated silicon carbide-oxide fiber 7 Silicon nitride whiskers 8 Alumina whiskers 9 Silicon nitride particles 10 Alumina particles

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI technical display location // F01D 5/28 (72) Inventor Toshiaki Mizutani 1 Komukai Toshiba-cho, Kawasaki-shi, Kanagawa Prefecture Incorporated company Toshiba Research and Development Center (72) Inventor Fumio Ueno 1 Komukai Toshiba-cho, Kouki-ku, Kawasaki City, Kanagawa Prefecture

Claims (4)

[Claims] 1. A layered structure ceramic composed of a surface layer containing oxide ceramics as a main component and an internal layer containing non-oxide ceramics as a main component, wherein an interface between the surface layer and the internal layer comprises: One or two or more thermal stress relaxation layers having a thermal expansion coefficient intermediate between the two, or a thermal stress relaxation layer in which the composition of the both changes continuously or discontinuously, and further the surface Of the thermal stress relaxation layer of the layer, from the vicinity of the thermal stress relaxation layer to the vicinity of the interface of the internal layer, from the middle of the thermal stress relaxation layer to the vicinity of the thermal stress relaxation layer of the internal layer, and the thermal stress relaxation layer of the surface layer The part from the vicinity to the middle of the thermal stress relaxation layer, near the thermal stress relaxation layer of the surface layer,
In any one of the above, a layered structure ceramics characterized by comprising a fiber layer in which one kind or two or more kinds of ceramic fibers are three-dimensionally composited. 2. The ceramic constituting the surface layer is aluminum oxide, magnesium oxide, yttrium oxide,
It is made of one of magnesium / aluminum spinel, chromium oxide, titanium oxide, silicon oxide, and mullite, and the fiber constituting the fiber layer has at least one selected from silicon carbide, silicon nitride, and aluminum oxide as a main component. 2. The layered structure ceramics according to claim 1, wherein the ceramics which is made of fibers and which constitutes the inner layer is at least one kind selected from silicon carbide, silicon nitride and sialon, or two or more kinds of composite ceramics. 3. A layered structure ceramic comprising a surface layer containing oxide ceramics as a main component and an inner layer containing non-oxide ceramics as a main component, wherein a portion of the inner layer on the surface layer side, The central portion of the inner layer, or the portion extending between the surface layer and the inner layer,
A fiber-reinforced layered structure ceramics characterized by being reinforced by oxide long fibers or non-oxide long fibers. 4. A layered structure ceramic composed of a surface layer containing oxide ceramics as a main component and an internal layer containing non-oxide ceramics as a main component, wherein both layers are provided at an interface between the surface layer and the internal layer. A layered ceramic structure comprising a ring-shaped ceramic fiber, a bow-shaped ceramic fiber convex to the surface layer side, or a corrugated ceramic fiber in a combined form.