JPH0873259A - Ceramic sintered compact and method for inspecting the same - Google Patents

Abstract

PURPOSE: To obtain a ceramic sintered compact having function to detect the progress of oxidation, breakage, etc., or self-restoring function and also having satisfactory mechanical characteristics at high temp. and to provide a method for inspecting the ceramic sintered compact by which the oxidation, breakage, etc., of the ceramic sintered compact can be successively inspected during use. CONSTITUTION: A detecting medium which reacts to oxidation or breakage and causes a chemical or physical change is allowed to exist in a part close to the surface of a ceramic sintered compact. based on nonoxide ceramics or a ceramic sintered compact having a layered structure obtd. by forming a surface layer based on oxide ceramics on the surface of a substrate based on nonoxide ceramics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic sintered body having a function of detecting progress such as oxidation and damage or a self-repairing function, and further having good mechanical properties at high temperature, and a ceramic sintered body thereof. The present invention relates to a method for inspecting a ceramic sintered body, which can successively inspect for oxidation, damage, and the like in use.

[0002]

2. Description of the Related Art Non-oxide ceramics having a high covalent bond, such as Si ₃ N ₄ , SiC, and AlN, have a low mechanical density (about 3 g / cc) and a high mechanical fracture strength. It has attracted attention as a high temperature structural material for combustors and gas turbines.

However, when Si ₃ N ₄ or SiC is exposed to an oxidizing atmosphere such as a high temperature combustion gas for a long time, passive oxidation shown in the following (1) and (2) occurs.

[0004]

[Equation 1]

[Equation 2]

In such passive oxidation,
A cristobalite SiO ₂ (melting point: 1713 ° C.) film is formed on the surface, and O diffusion in the SiO ₂ film limits the growth of the film thickness d as shown in (3) below and suppresses the oxidation rate.

[0006]

(Equation 3) That is, with the passage of time, a protective film SiO against oxidation
₂ (Cristobalite) reduces the deterioration of fracture strength over time.

However, elements such as sintering aid B and Al, which are added in small amounts to ordinary SiC ceramics, and ordinary Si
Sintering aid Y added in small amount to ₃ N ₄ ceramics
Oxides such as ₂ O ₃ and Al ₂ O ₃ diffuse on the surface of the sintered body in a long-time high-temperature oxidation test and form a solid solution with the SiO ₂ protective film to lower the eutectic temperature to form a liquid phase. Therefore, the cristobalite film is destroyed (foaming phenomenon) to promote oxidation.

Therefore, it is desired that the amount of the sintering aid is as small as possible. However, even with ideal Si ₃ N ₄ ceramics and SiC ceramics with the amount of auxiliary agent reduced to the limit, Cristobalite S forms a protective film.
When it is exposed to a high temperature combustion gas flow having a melting point (1713 ° C.) or higher of iO _2, the protective film is dissipated and cannot be used at all. However, in order to improve the efficiency of the gas turbine, durability and oxidation resistance up to higher temperatures are desired.

On the other hand, when exposed to an oxidizing atmosphere such as a high-temperature combustion gas for a long time, AlN undergoes passive oxidation, and Al ₂ O ₃ (T _MP = 20) which is stable up to a high temperature as shown in (4) below.
54 ° C.) is produced.

[0010]

[Equation 4]

However, since its thermal expansion coefficient (8 ppm / ° C.) is significantly different from that of the AlN base material (5 ppm / ° C.), fine cracks are generated, and a stable oxidation resistant protective film is formed. Have difficulty. Therefore, the application of AlN ceramics to high temperature structural parts is hindered.

[0012]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As described above, 15
When applying Si ₃ N ₄ , SiC, or AlN ceramics, which has the excellent characteristics of not showing a reduction in immediate fracture strength up to a high temperature of 00 to 1700 ° C., as a high temperature structural member such as a combustor or a gas turbine, high temperature oxidation The problem of life due to deterioration of mechanical properties dominated by corrosion causes the upper limit of the rated operating temperature of the combustor, gas turbine, etc. to be suppressed, and efficiency improvement due to high temperature operation reaches its limit.

For brittle ceramics, early detection of damage such as oxidation and cracks is effective in improving the reliability of the entire member, and if the self-healing function is further advanced, cracks or the like will occur. Will be effective in preventing the progress of

The present invention has been made in view of the above circumstances, and has a ceramic sintered body having a function of detecting progress of oxidation or damage or a self-repairing function, and further having good mechanical properties at high temperature. It is an object of the present invention to provide a method for inspecting a ceramics sintered body, which can sequentially inspect the ceramics sintered body for oxidation, damage and the like under use.

That is, it can be used for application to structural oxide / non-oxide ceramic laminated material parts having excellent high-temperature corrosion resistance without impairing the characteristics of Si ₃ N ₄ , SiC, and AlN ceramic materials related to mechanical fracture strength. To do so.

[0016]

In order to solve the above-mentioned problems, the invention of claim 1 provides a ceramic sintered body mainly composed of non-oxide ceramics or a surface of a base body mainly composed of non-oxide ceramics. A ceramic sintered body having a layered structure formed by forming a surface layer mainly composed of oxide ceramics, in which a detection medium which causes a chemical or physical change in response to oxidation or damage is internally provided near the surface. It is a thing.

Desirably, a composite of carbon fibers, barium oxide, or yttrium oxide is applied as the detection medium.

According to a second aspect of the present invention, the ceramic sintered body according to the first aspect is used in an oxidizing atmosphere, and a chemical or physical change of the detection medium of the ceramic sintered body is electrically or gas changed. A method for inspecting a ceramic sintered body, characterized by performing an analytical or optical measurement and inspecting the oxidation or damage of the ceramic sintered body outside the ceramic sintered body.

According to a third aspect of the present invention, a ceramic sintered body having a layered structure is formed by forming a surface layer mainly composed of oxide ceramics on the surface of a base body mainly composed of non-oxide ceramics with an intermediate layer interposed therebetween. The intermediate layer is made of a material which is oxidized in an oxidizing atmosphere to produce a product mainly containing an oxide constituting the surface layer or an oxide similar thereto.

According to a fourth aspect of the invention, the surface of the SiC ceramic substrate or the AlN ceramic substrate is AlN-Si.
It is covered with a C solid solution layer (SiC: AlN = 1: 2 to 1: 6), and mullite (3Al ₂ O ₃ .2SiO ₂ ) is further coated thereon.
~ 3Al ₂ O ₃ · SiO ₂ ) and alumina (Al ₂ O ₃ )
And is covered with an oxide composite layer.

When manufacturing this ceramic sintered body, an intermediate layer (Sialon, AlN-SiC solid solution, AlN) is formed on the surface of a non-oxide (Si ₃ N ₄ , SiC, AlN) substrate.
A preferred manufacturing method is to perform heat treatment in a high temperature oxidizing atmosphere when forming the oxide composite layer on a member coated with (Si ₃ N ₄ composite).

For example, (1) in a heat treatment in a high temperature oxidizing atmosphere, using a mullite container / sample stand,
Form high quality mullite surface film. (2) In a heat treatment in a high temperature oxidizing atmosphere, an alumina surface film is first formed by treating at a high temperature of 1500 ° C. or higher using an alumina container / sample stage, and then the alumina surface film and the intermediate layer interface. To generate a mullite layer.

Further, as the ceramic sintered body, preferably, the surface of the Si ₃ N ₄ ceramics base material or the AlN ceramics base material is coated with a sialon-based (Z = 4 to 36/7 equivalent) solid solution layer, and further thereon. Mullite (3Al
₂ O ₃ · 2SiO _{2 to} 3Al ₂ O ₃ · SiO ₂ ) and an oxide composite layer of alumina Al ₂ O ₃ are used.

The oxide composite layer is made of mullite (3Al ₂ O _{3
· 2SiO 2 ~3Al 2 O 3 ·} SiO 2) is that,
Alternatively, the oxide composite layer is an inner mullite (3Al ₂ O ₃ ·.
_{2SiO 2 ~3Al 2 O 3 · SiO} 2) and it is desirable that the double structure of the outer alumina Al ₂ O _3.

Sialon type (Z 3.0 to 5.0 equivalent)
The atomic ratio O / N of the composition of the intermediate layer is Al ₂ O ₃ -AlN-S.
Si In iO ₂ -Si ₃ N ₄ system phase diagram ₃ N ₄ -3Al
It is desirable that it is on the nitrogen excess side of the ₂ O ₃ .AlN mixed line and the atomic ratio Si / Al is 2 or more and 6 or less.

Further, in ceramics having a laminated structure,
It is desirable to alleviate the concentration of generated thermal stress by dispersing and distributing closed pores near the interface. Further, in the oxide / non-oxide laminated structure, it is desirable that most of the closed pores are distributed on the oxide side having a large thermal expansion coefficient.

[0027]

In the ceramic sintered body according to the first aspect of the present invention, for example, when carbon fibers are combined as a detection medium in silicon nitride, when the oxidation progresses, the carbon fibers are oxidized to carbon dioxide. Since the diameter of the carbon fiber evaporates and the electric resistance changes, the degree of oxidation can be electrically detected. In addition, even if a crack is formed in the carbon fiber, the electric resistance changes, so that the crack can be detected.

Further, when barium ceramics is laminated in silicon nitride as an oxidation detecting medium, when barium oxide is exposed to an oxidizing atmosphere as the crack progresses, barium oxide evaporates. By monitoring this evaporation pressure, cracks can be detected. At this time, wiring for measuring electric resistance is not necessary.

When eurobium-doped yttrium oxide ceramics are laminated in silicon nitride ceramics, the generation of cracks changes the current value converted from the amount of emitted light, so that cracks can be detected.

According to the second aspect of the invention, while the ceramics sintered body is used in an oxidizing atmosphere, the chemical or physical change of the detection medium of the ceramics sintered body is electrically, gas analytically or optically changed. The measurement is performed and the oxidation or damage of the ceramic sintered body is inspected outside the ceramic sintered body.

According to the first and second aspects of the present invention, for example, a ceramic sintered body is applied to a gas turbine blade, and a detection medium is arranged in the vicinity of the surface of the gas turbine blade, which causes a crack in the surface layer. It becomes possible to apply such as detecting at a point of time and safely stopping the operation etc. before the cracks propagate to the substrate.

Known examples of crack detection by carbon fiber (for example, Journal of the Ceramic Society of Japan, 100
[4] 585-588 (1992)), a means of using a matrix having a low elastic modulus to detect a large deformation of the matrix and fracture of the carbon fibers is also known. However, in this technique, as reported by the authors of the above-mentioned publicly known examples (for example, Proceedings of Autumn Symposium of the Japan Ceramic Society 1993, p262-263), the fiber is not carbon fiber but SiC having higher conductivity. It uses fibers. If ceramics with a high elastic modulus is used for the matrix and the fibers break and an increase in resistance is observed,
The destruction of the matrix has already advanced significantly, and it does not make sense.

On the other hand, in the present invention, under the limitation that it is used in an oxidizing high temperature atmosphere, the fiber is contacted with the atmosphere due to the development of cracks rather than being stressed and broken. Since the invention is intended to increase the electric resistance due to burning and breaking, even a slight crack can be felt sharply and has a very effective detection function. Therefore, as described in the later test example, it becomes possible to detect even a small crack caused by an impact of a flying object or the like.

According to the third aspect of the invention, when applied as a high temperature member such as a turbine, surface cracks generated during the mounting operation are caused by the supplied oxidizing high temperature atmosphere gas and the surface layer / intermediate layer / base material. Back-filled with the reaction product of (3), thereby performing a self-repairing action. In this case, the surface crack of the member generated during the mounting operation may be penetrated into the surface crack by applying a predetermined repair accelerator, and then repaired by the mounting operation or a separate heat treatment. Here, as the predetermined repair accelerator, Al ₂ O ₃ system or SiO _{2 is used.}
It is desirable to be a solution-type organic or inorganic compound of the system.

A ceramics sintered body according to the present invention of claim 4 is based on a non-oxide (Si ₃ N ₄ , SiC, AlN) ceramics having excellent mechanical fracture strength up to a high temperature of 1500 ° C. or higher, An intermediate layer (Sialon,
SiC-AlN solid solution, AlN-Si ₃ N ₄ mixture) is coated, and mullite (3Al ₂ O ₃ .2Si) is further coated thereon.
_{O 2 ~3Al 2 O 3 · SiO} 2) and alumina Al ₂ O ₃
By coating with an oxide composite layer of
It is applied as a structural ceramic laminated material component with heat resistance and oxidation resistance of over 00 ° C.

In the present invention, the base material of Si ₃ N ₄ , SiC, A
There is no special limitation on the type of 1N ceramic. However, for application as a structural material, it is desirable to use a type of member that is a tough base material having high mechanical fracture strength and fracture toughness and that can be manufactured in a complicated shape relatively easily. Therefore, Al ₂ O ₃ -Y ₂
O ₃ system or the like, B-C · Al-C system, _{etc., Al 2 O 3 · Y 2} O
_It is desirable to use a material that has been densified by a non-pressure sintering method by adding a small amount of a densification aid such as ₃ series. In addition, to improve the reliability of the member, there is also a material in which particles such as long fibers and short fibers of carbon, SiC, etc. or boride, carbide, nitride of heat-resistant metal are intentionally dispersed and complexed to improve the toughness value. used. However, when aiming for use in a high temperature range of 1500 to 1700 ° C or higher, which is higher than the temperature range of 1300 to 1500 ° C that has been conventionally assumed, the mechanical fracture strength of the SiC base material is remarkable up to 1500 to 1700 ° C or higher. It is required not to cause significant deterioration. As such a kind of base material, there is, for example, non-pressurized sintered B-C auxiliary SiC ceramics in which the content of the auxiliary B in the sintered body is suppressed to 0.1 wt% or less,
In the future, new Si ₃ N ₄ , SiC, and AlN base material compositions will be developed.

[0037]

[Table 1]

As a means for suppressing the performance deterioration of non-oxide ceramic parts due to high temperature oxidation, the inventors have variously studied a method of covering the surface with an oxide film which is stable at high temperatures and has a low oxygen diffusion coefficient. Although Al ₂ O ₃ having a high melting point is effective as such an oxide,
_Since the difference in the coefficient of thermal expansion between ₃ N ₄ , SiC, AlN ceramics and Al ₂ O ₃ ceramics is large, strain accumulates in the temperature rising / falling cycle after film formation, and cracks / delamination occur in the film. It is difficult to put to practical use. The inventors have paid attention to the low Young's modulus, high melting point, intermediate thermal expansion coefficient of mullite ceramics, and high eutectic point (1840 ° C.) with Al ₂ O _3, and have focused on Si ₃ N ₄ , SiC,
A member in which the surface of the AlN ceramic substrate was covered with a mullite protective film was experimentally studied.

In the process, paying attention to the composition close to the Si / Al atomic ratio of mullite, the sialon (Si _6-z Al _z O _z
N ₈ −z; z = 4.5) and 3AlN—SiC sintered body were subjected to high temperature oxidation treatment to form a mullite surface layer. Furthermore, sialon (Si _6-z Al _z O _z N _8-z ; z
= 4.5) It was discovered that a laminated material of both ceramics and Si ₃ N ₄ ceramics can be easily obtained by hot-press simultaneous firing. This is because the crystal structures of both are the same,
This is probably because the thermal expansion coefficients are similar.

In addition, AlN-SiC solid solution (3AlN-
SiC) ceramics and SiC ceramics or A
2 types by simultaneous hot pressing of 1N ceramics (3AlN-SiC / SiC, 3AlN-SiC / AlN)
It was found that the above laminated material can be easily obtained. This may be because the crystal structure of each is similar to the coefficient of thermal expansion.
Through such a process, the inventors have invented a series of structural ceramic laminated material parts to which heat resistance and oxidation resistance of more than 1500 to 1700 ° C. have been imparted and a basic structure of a manufacturing method thereof.

Next, a method for producing a structural oxide / non-oxide ceramics laminated material component excellent in high temperature corrosion resistance without deteriorating the features of the present invention concerning mechanical fracture strength will be described. When the product of the present invention is commercialized, it can be manufactured by various methods depending on its size and shape and the formed film thickness. Ordinary powder metallurgy can be applied to large simple shaped products such as inner walls of combustors.

Submicron 6H-SiC powder / 2H-A
The solid solution granulated powder prepared by mixing 1N powder in an amount of 3 mol / 1 mol was subjected to mold molding (0.25 ton / cm ² ) to obtain 33 × 44 × 1.
I made a flat plate of 5mm. Granulated powder for simple substance in which a small amount of sintering aid (B and C, Al and C, etc.) is added to SiC powder and a small amount of sintering aid (Al ₂ O ₃ , Y ₂ O) in AlN powder.
₃ , etc.) was added to the granulated powder for simple substance, and a flat plate of 33 × 44 × 9 mm was produced by mold molding (0.25 ton / cm ² ). The solid solution compacts were stacked on the upper and lower sides of each single compact and loaded into a graphite mold (inner dimension 33 × 44 mm) coated with a release agent (BN), and hot press sintering (190
0-2200 ° C-1H-50 MPa). In sintering, the temperature is raised to 1000 ° C. without pressurizing in vacuum to thoroughly remove the adsorbed gas, and then the constant temperature increase (1000 ° C./H) to the sintering temperature after introducing the atmosphere is performed at the beginning of the process ( 1000-15
Hot press pressure to 00 ° C) at a constant rate (50 MPa / H)
And hot press sintering (1900-2200 ° C-1H)
The hot pressing pressure was released when the shrinkage behavior observed inside was saturated. The atmosphere at the time of hot press sintering is Ar gas, N ₂ gas or a mixed gas of both of them at 1 to 9 atm.

The upper and lower surfaces of the two kinds of laminated sintered bodies (roughly 33 × 44 × 5 mm) which could be densified to a porosity of less than 3% were polished and measured by X-ray diffraction. Hexagonal (2H) Only the diffraction peak of was observed and it was an AlN-SiC solid solution single phase. Moreover, when the state of the interface was searched by observing the cut / polished surfaces of the two types of sintered bodies by EDX, the composition gradient width in the direction perpendicular to the interface was determined by any combination of elements (Si, Al, N,
C, etc.) was also within 1 to 100 μm, and was slightly dependent on the sintering conditions (temperature: time: temperature rising / pressurizing program).

Submicron α-Si ₃ N ₄ powder / 2H-
AlN powder / α-Al ₂ O ₃ powder was added to “1 mol / 3 mol / 3 mo
l (Z = 4.5), 1 mol / 2 mol / 2 mol (Z = 4.
0), 1mol / 9mol / 0mol (Si 3 N 4 · 9Al
N) ”, three types of granulated powder for solid solution prepared by metal mold molding (0.25 ton / cm ² ) are used, and 33 × 44: 1.
I made a flat plate of 5mm. Further, a small amount of sintering aid (ZN = 0.25 equivalent of AlN / Al ₂ O ₃ and 2 wt% Y ₂ O ₃ ) was added to the Si ₃ N ₄ powder to form a granulated powder for simple substance into a die (0 A flat plate of 33 × 44 × 9 mm was produced by 0.25 ton / cm ² ).

The same solid solution compacts were stacked on the upper and lower sides of the individual compacts and loaded into a graphite mold (inner dimension 33 × 44 mm) coated with a release agent (BN), followed by hot press sintering (1700-170). 1850 ° C-1H-30 MPa). In addition, “Si ₃ N
Stacking a solid solution for granulation molding of ₄ · 9AlN composition ",
Graphite mold coated with release agent (BN) (inner dimension 33 x 4
4 mm) and hot press sintered (1700-185)
0 ° C-1H-30 MPa). 100 for sintering
Up to 0 ° C, the temperature was raised without vacuum to thoroughly remove the adsorbed gas, and then the temperature was raised at a constant rate up to the sintering temperature after introducing the atmosphere (1
(000 ° C / H) At the initial stage (1000 to 1300 ° C) of the process, the hot press pressure was increased at a constant rate (50 MPa / H), and the shrinkage behavior observed during hopless sintering (1700 to 1850 ° C-1H) was saturated. Then the hot press pressure was released. The atmosphere during hot press sintering is N _{2 at} 1 to 9 atm.
It is gas.

The four types of laminated sintered bodies were able to be densified to a porosity of less than 3%, but unlike other laminated sintered bodies, "Z =
A hexagonal crack was observed in the surface layer of "4.5 composition", and when the surface was polished and X-ray diffraction measurement was performed, a β-sialon phase,
γ-Al ₂ O ₃ phase, 8H-AlN polymorph Si _3-x Al _{1 + x} O
_{There was an x} N _5-x phase (x = 2.20-2.37). Therefore, the amount of Y ₂ O ₃ added to the granulated powder for simple substance of Si ₃ N ₄ is increased (2 wt% → 4 wt%), followed by hot pressing at 1800 ° C., followed by annealing at 1850 ° C.-3H and slow cooling (100%). (° C / H), the hexagonal cracks and γ-Al ₂
The O ₃ phase disappears and the 8H-AlN polymorph Si _3-x Al _{1 + x} O _x N
_{Since the 5-x} phase increased, Al ₂ O with a large coefficient of thermal expansion
It was confirmed that the large amount of _three phases was the cause of the hexagonal crack. The surface layer of “Z = 4.0 composition” was β-sialon single phase. The surface layer of "Si ₃ N ₄ .9AlN composition" was a mixed phase of β-sialon (Z = 0) and 2H-AlN.

Further, the cutting / polishing surfaces of the three types of sintered bodies are E
When the state of the interface was investigated by DX observation, the composition gradient width in the direction perpendicular to the interface was determined by any combination of elements and elements (Si, A
(l, N, O, Y) was within 1 to 100 μm, and was slightly dependent on the sintering method (temperature: time: temperature rise: pressurization program).

In the oxide film stacking test, six types of upper and lower surface-polished sintered body samples (rough size 33 × 44 × 5 mm) were set up on a holder made of Al ₂ O ₃ porous brick, and a Tecorundum heating element was used. Placed in an Al ₂ O ₃ core tube (inner diameter 50φ) parallel to the tube axis of a horizontal annular furnace, and simulating atmospheric flow 80% N ₂ -20%
O ₂ : 0.05 to 5.0 liters / Min.) In temperature (1
The effect was pursued for 200 to 1600 ° C.) time (: 3 to 96 H).

The constituent phases of the produced oxide film changed depending on temperature, time and environment. Organize XRD data, Al ₂
The equilibrium vapor pressure of O ₃ is so small that it can be ignored.
₂ means significant equilibrium vapor pressure (P _eq (atm) = 10 ^-10.4 ； 1
600 ° K, 10 ^-8.3 : 1800 ° K), it was found that the following oxidation reaction occurred.

That is, in the initial stage of oxidation, the dissipation of SiO ₂ is remarkable and the reaction (5), (6) or the reaction (7), (8) occurs.
Alternatively, although the reactions (9) and (10) proceed simultaneously, if the surface is covered with a moderate alumina-mullite phase mixed film, the reactions (5), (7) and (9) are gradually suppressed and the reaction formula ( 6), (7) and (10) are the main reactions.

[0051]

(Equation 5)

(Equation 6)

(Equation 7)

[Equation 8]

[Equation 9]

[Equation 10]

Therefore, when 96H oxidation treatment is carried out in a high temperature (1600 ° C.) high speed air stream (40 mm / s), the oxide film has an α-Al ₂ O ₃ phase on the outermost surface and a mullite phase (3 A) on the inner side.
l ₂ O ₃ · 2SiO _{2 to} 3Al ₂ O ₃ · SiO ₂ ) 2
It has a layered structure. A similar oxide film was also formed by 24H oxidation treatment in a medium temperature (1500 ° C) / medium velocity air stream (8.5 mm / s), but when 96H oxidation treatment, the oxide film reaches the outermost surface in the mullite phase ( 3Al ₂ O ₃・ 2SiO ₂
It became a ~3Al ₂ O ₃ · SiO ₂₎ single-phase.

This is the S supplied from the inner mullite phase
This is because iO ₂ reacts with Al ₂ O _{3 on the} outermost surface to form mullite, and the atomic ratio Al / S on the outermost surface in EDX line analysis.
i is somewhat higher than the inside and is in the stable composition region (3Al ₂ O ₃ .2SiO _{2 to} 3Al ₂ O ₃ .Si) of the mullite phase.
It was confirmed to be within the range of O ₂ ). Furthermore, in oxidation at low temperature (1300 ° C) and low-speed air flow (1.7 mm / s), the oxide film is mullite single-phase (3
Al ₂ O ₃ · 2SiO _{2 to} 3Al ₂ O ₃ · SiO ₂ ).

On the other hand, the porous brick holder and the core tube of the horizontal annular furnace are made of alumina (Al ₂ O ₃ ) and mullite ( _{3 A} ).
In a similar oxide film stacking test conducted by replacing with l ₂ O ₃ .2SiO ₂ ), the constituent phase of the produced oxide film was a mullite (3Al ₂ O ₃ .2SiO ₂ ) single phase in any case. It was

Reference will be made to other manufacturing methods, particularly the method of forming the intermediate layer. When forming a thin intermediate layer of several tens of μm on the surface of a member having a complicated curved surface such as a moving blade or a stationary blade of a gas turbine, the CVD method and the sputtering method can be applied. A dense and high-quality intermediate layer can be formed. However, considering the manufacturing cost and efficiency, a method of applying a suspension in which a mixed powder prepared in a predetermined intermediate layer composition is uniformly dispersed in an organic solvent to a curved surface of a base material having a complicated shape is promising.

The simplest method is to apply with a brush. In order to form a dense and high-quality intermediate layer, it is preferable to heat-dry for each one-layer coating, move to the next coating, heat up to around 1800 ° C. for several coatings and sinter, and then proceed to the next coating. . Also, after each heating and sintering, if the surface is scanned with laser irradiation light to enhance the sintering, a good intermediate layer without pin holes is completed.

Under the conditions and methods as described above, various combustor / gas turbine parts of large and small simple shapes to complex shapes can be finished into structural products having excellent heat resistance and durability.

Desirable ranges of the surface oxidation treatment temperature, the atmospheric flow velocity and the atmospheric environment are as follows. That is,
If the treatment temperature is less than 1200 ° C., the production rate of the surface oxide film is slow and long treatment is required, which is not economical. Also,
At a treatment temperature of more than 1800 ° C., volatilization of SiO ₂ becomes remarkable, the density of the produced surface oxide film is extremely lowered, and internal pores are connected, so that the function of the surface oxide film as a protective film is impaired. 0.85 mm / s. At air velocities below, harmful impurity species (eg C
_{O 2, B 2 O 3,} Y 2 O 3, etc.) is not preferable because the residence incomplete evacuation, 85 mm / s. At air velocities in excess of 10, the temperature distribution in the furnace cannot be ignored, making large-scale batch processing difficult.

The material of the core tube / sample holder, which also serves as a sample container, is limited to alumina or mullite which has a high purity and a high melting point as a co-material of the produced oxide surface layer. This is to avoid the release of seeds.

Each composition of the intermediate layer (Sialon, SiC-A
The desirable range of 1N) is as follows. That is,
When the atomic ratio Al / Si is less than ₂ , SiO ₂ appears in the oxide film (mullite 3Al ₂ O ₃ .2SiO ₂ ) formed by the high temperature oxidation treatment, and the eutectic point (SiO ₂ -3Al ₂ O ₃
・ 2SiO ₂ ; 1535 ° C.) causes a liquid phase to cause a remarkable foaming phenomenon and lowers the durable temperature. Atomic ratio Al /
Si exceeds 6 When oxide film formed by high-temperature oxidation treatment (mullite _{3Al 2 O 3 · 2SiO 2 ~3Al} 2 O 3
・ Since the number of SiO ₂ defects in (SiO ₂ ), the oxygen permeability is improved and the oxidation of the intermediate layer is promoted, a large amount of Al ₂ O ₃ phase is generated in the oxide film to make it porous. Turn into.
Further, due to Al ₂ O ₃ having a high coefficient of thermal expansion, the oxide film is significantly broken in the heating and cooling cycle. In the sialon intermediate layer, the atomic ratio O / N is
When reaching the oxygen excess side above the i ₃ N ₄ -3Al ₂ O ₃ · AlN mixed line, a large amount of Al ₂ O ₃ phase having a large thermal expansion coefficient is generated in the sialon intermediate layer when the Al / Si ratio is large. It becomes difficult to suppress cracks generated in the intermediate layer joined to the base material, and when the Al / Si ratio is small, the low melting point X phase (Si ₃ Al ₆ O ₁₂ N ₂ : 1750 ° C) is contained in the sialon intermediate layer. ) Is generated in a large amount to impair the heat resistance of the intermediate layer.

The preferable range of the thickness of the intermediate layer is as follows. If the minimum thickness of the intermediate layer is less than 10 μm, the intermediate layer will be substantially lost at the stage of forming the surface oxide layer by a normal oxidation treatment, so that the intermediate layer will be removed through the oxide surface layer during use as a mounting component. The Si ₃ N ₄ · SiC · AlN material is oxidized, and the high temperature long-term service life of the laminated material component is compromised. Therefore, the minimum wall thickness of 100 μm or more is desirable for combustor / gas turbine applications that require long life especially in harsh environments. There is no upper limit to the maximum thickness of the intermediate layer, and it does not matter if the laminated component is substantially composed of the intermediate layer composition.

The desirable range of the thickness of the surface oxide layer formed by the high temperature oxidation treatment in which the temperature and atmosphere are controlled is as follows. That is, the minimum thickness of the initial surface oxide layer formed by the high temperature oxidation treatment is 2 μm. When the initial thickness is less than 2 μm, the intermediate layer is oxidized at the interface between the surface oxide layer and the intermediate layer when mounted as a component and exposed to high temperature combustion gas, etc., and the newly generated oxide phase is not always the initial surface layer. It is not always the case that a homogeneous mullite single phase that matches the above is obtained, and the above-mentioned 2 μm is the minimum necessary in order to properly induce the oxide phase generated at the interface between the surface oxide layer and the intermediate layer. It is thick.

The total thickness of the initial surface oxide layer formed by the high temperature oxidation treatment and the total thickness of the oxide layer generated at the interface between the initial surface oxide layer and the intermediate layer after mounting is the upper limit from the surface of the member. There is no. However, a surface oxide layer thickness of more than 100 mm is not practical for using non-oxide / oxide laminated material parts.

[0064]

Embodiments of the present invention will be described below. First, as Examples 1 to 3, a ceramics sintered body according to the invention of claims 1 and 2 and an inspection method thereof will be described.

In these Examples 1 to 3, the ceramics sintered body was composed of silicon nitride (Si ₃ N ₄ ) powder, carbon fiber, barium oxide (B ₂ O ₃ ) powder, and yttrium oxide (Y ₂ O ₃ ). ₃ ) After filling the powder into the mold,
It can be manufactured by molding and sintering. Yttrium oxide and aluminum oxide as a sintering aid are mixed with a silicon nitride powder, which is a raw material of the substrate, in a ball mill. The yttrium oxide powder to be laminated is obtained by adding eurobium and calcining the powder coprecipitated in acetic acid.

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.
After that, one of carbon fiber, barium oxide powder, and yttrium oxide powder is laminated, and finally silicon nitride powder is filled again, and a preform is prepared by cold pressing. The obtained preformed body is hot-press sintered to obtain the sintered body of this example.

Example 1 (FIGS. 1 to 4) In this example, silicon nitride powder and carbon fiber as a detection medium were used as raw materials for the ceramic sintered body. 5% by weight of yttrium oxide and 2% by weight of aluminum oxide were added to the silicon nitride as a base material as a sintering aid and mixed using a ball mill.

Using the above silicon nitride powder and carbon fiber,
A sintered body was produced. First, a silicon nitride powder serving as a substrate was filled in a mold having an arbitrary shape, and carbon fibers were arranged so as to be parallel to the lower surface of the mold. At this time, when the final shape of the sample was 4 mm × 3 mm × 40 mm, the number of carbon fibers was one at the center at a depth of 0.5 mm from the surface. After arranging the carbon fibers, silicon nitride powder was laminated again and cold pressed to obtain a molded body.

Then, hot press sintering was performed in a carbon mold to obtain a sintered body sample. Sintering conditions are sintering temperature 1
800 ℃, Pressing pressure 30MPa, Sintering temperature holding time is 1
It's time. The atmosphere was 0.1 MPa nitrogen. The obtained sintered body was processed into a test piece of 4 mm × 3 mm × 40 mm, which was used as a sample.

FIG. 1 schematically shows a cross-sectional state of the ceramic sintered body 1 obtained by the above method, which is taken by a micrograph. As shown in the figure, the carbon fibers 3 are arranged near the surface of the silicon nitride ceramics as the base 2.

FIG. 2 shows the obtained ceramic sintered body 1.
In the figure, the wiring 5 of the electrical resistance measuring device 4 as the inspection means is provided and put into practical use. As shown in the figure,
The wiring 5 for measuring the electric resistance passes through the ceramic sintered body 1 as a sample, and the measurement can be performed even during exercise.

FIG. 3 shows the results of measuring the electrical resistance of this sample which was subjected to an oxidative test in the air at 1500.degree. As indicated by the characteristic line A in the figure, the electric resistance increases with the passage of time. This is because the carbon of the carbon fiber 3 is converted into carbon dioxide and evaporated by the oxidation, and the fiber diameter is reduced.
Therefore, the progress of oxidation can be detected by monitoring the change in this electric resistance.

FIG. 4 shows a three-point bending test based on JIS for this sample, which was subjected to energization of 0.1 mA.
The result of having measured the load-electrical resistance curve using the direct current 2 terminal method is shown. As indicated by the characteristic line B in the figure, when the load reaches a certain value, the value of the electric resistance sharply increases.
This is because the carbon fiber 3 was broken.

The breakage of the carbon fiber 3 means that a crack has been generated in the silicon nitride ceramics which is the substrate 2, and the crack has grown. Therefore, the occurrence of cracks can be detected by monitoring the change in this electric resistance.

Example 2 (FIGS. 5 and 6) In this example, silicon nitride powder and barium oxide as a detection medium were used as raw materials for the ceramics sintered body. The silicon nitride powder was obtained by the same method as in Example 1 above.

A laminate was prepared using the above silicon nitride powder and barium oxide powder. First, a silicon nitride powder serving as a substrate was filled in a mold having an arbitrary shape, and subsequently barium oxide powder and silicon nitride powder were laminated in this order and cold pressed to obtain a molded body. Then, hot press sintering was performed in a carbon mold to obtain a laminated body sample. The sintering conditions are a sintering temperature of 1800 ° C., a pressing pressure of 30 MPa, and a temperature holding time of 1 hour. The atmosphere was 0.1 MPa nitrogen. The obtained sintered body was processed into a test piece of 4 mm × 3 mm × 40 mm, which was used as a sample. At this time, the barium oxide ceramics were positioned 0.5 mm from the surface of the sample, and the thickness thereof was set to 0.1 mm.

FIG. 5 schematically shows an image of a cross section of the obtained ceramic sintered body 1, taken by a micrograph. A barium oxide ceramic layer 7 is formed near the surface of the silicon nitride ceramic of the base 6.

FIG. 6 shows the results of measuring the vapor pressure of barium oxide at this time by conducting a three-point bending test based on JIS at 1500 ° C. As shown by the characteristic line C in the figure, it can be seen that the vapor pressure begins to rise when the load exceeds a certain value. This is because the crack generated in the substrate 2 reached the barium oxide layer 7 and the barium oxide was evaporated.

From this, it is possible to detect the occurrence of cracks by monitoring the vapor pressure of barium oxide. Specifically, the atmosphere was allowed to flow during the test, and the vapor pressure of barium oxide was monitored at the outlet.

Example 3 (FIGS. 7 and 8) In this example, silicon nitride powder was used as the raw material for the ceramic sintered body and yttrium oxide was used as the detection medium. The silicon nitride powder was obtained by the same method as in Example 1 above. Yttrium oxide is 5% by weight of eurobium
After doping, the powder was mixed in acetic acid, and the powder formed by the coprecipitation reaction was calcined.

A laminate was prepared using the above silicon nitride powder and yttrium oxide powder. First, a silicon nitride powder serving as a substrate is filled in a mold having an arbitrary shape, and then yttrium oxide powder and silicon nitride powder are laminated in this order,
Cold pressing was performed to obtain a molded body. Then, hot press sintering was performed in a carbon mold to obtain a laminated body sample. The sintering conditions are a sintering temperature of 1800 ° C., a pressing pressure of 30 MPa,
The temperature holding time is 1 hour.

The atmosphere was 0.1 MPa nitrogen. The obtained sintered body was processed into a test piece of 4 mm × 3 mm × 40 mm, which was used as a sample. At this time, the yttrium oxide ceramics was located 0.5 mm from the surface of the sample and had a thickness of 5 mm.
It was set to mm.

FIG. 7 schematically shows a cross-sectional state of the obtained ceramics sintered body 1 taken by a micrograph. As shown in the figure, the yttrium oxide layer 9 is formed in the silicon nitride ceramics of the substrate 8.

FIG. 8 shows the results of measurement of the current value obtained by performing a three-point bending test based on JIS on this sample, irradiating the yttrium oxide layer with ultraviolet rays at the same time, and converting the light emission amount using a silicon photodiode. .

As shown by the characteristic line D in the figure, it can be seen that the current value sharply decreases when the load exceeds a certain value.
This is because the yttrium oxide layer 9 was cracked. Since the crack is generated from the silicon nitride ceramic which is the substrate 8, the occurrence of the crack can be detected by monitoring the current value.

Examples 4 to 15 (Reference Examples 1 to 7) (Table 2,
3) These embodiments apply claims 3 and 4,
Table 2 shows the composition range of the intermediate layer, constituent phases, presence or absence of cracks, generated oxides, surface phases, etc. for Examples 4 to 7 and Reference Examples 1 and 2 when the intermediate layer is an AlN / SiC solid solution. There is. Further, Table 3 shows the composition range of the intermediate layer, the constituent phase, the presence or absence of cracks, the produced oxide, the surface phase, etc. of Examples 8 to 15 and Reference Examples 3 to 7 when the intermediate layer is Sialon or the like. There is.

[0087]

[Table 2]

[0088]

[Table 3]

The difficulty of the oxide film laminating process is irrespective of the type of various laminated base materials (Si ₃ N ₄ , SiC, AlN), and the type of crystalline phase constituting the intermediate layer (3AlN.SiC, Sialon, 2H-). AlN-β-Si ₃ N ₄ ) and its composition ratio.

Reference example 1 in which the atomic ratio Si / Al is less than 2,
In Nos. 3 and 6, generation of a large amount of silica (cristobalite phase) in addition to the mullite phase and foaming at 1600 ° C. treatment were observed in the surface oxide phase. This is because the silica / mullite eutectic temperature (1535 ° C.) was exceeded and some melting occurred.

In Reference Examples 2, 4, and 7 in which the atomic ratio Si / Al exceeds 6, a large amount of alumina (α
Phase) was generated and the surface oxide layer became porous, and the consumption of the intermediate layer was not saturated even by the 96H treatment. However, in Examples 7, 11, and 15 in which the atomic ratio Si / Al was 6, the open pores of the surface oxide layer containing a considerable amount of alumina became closed pores, and saturation of the consumption of the intermediate layer was observed. A composition gradient of mullite on the surface of alumina was generated in the oxide surface layer.

Despite the large difference in coefficient of thermal expansion between alumina and mullite, the surface oxide layer was stably and firmly integrated without peeling. The reason for this is that the closed pores dispersed in the oxide phase (particularly on the alumina side) reduce the apparent thermal expansion coefficient of alumina. It turned out from the result.

As described above, the method of appropriately distributing the closed pores in the vicinity of the joint interface to relax the residual stress in the vicinity of the joint interface can be applied to a general laminated composite. (For example, an alumina sintered body having a closed porosity of 10% and a dense Si ₃ N ₄ sintered body are pasted with a 2Al ₂ O ₃ —Si ₃ N ₄ mixed powder slurry and hot pressed (1800 ° C.-30 MPa). A stable and strong joined body was obtained.) Examples 4 to 6 and 8 to 1 in which the atomic ratio Si / Al was 2 to 5
In Nos. 0, 13, and 14, the densely formed oxide surface film is not necessarily a mullite single phase, but a small amount of the second phase cristobalite (high concentration inside the film) or alumina (high concentration outside the film). It didn't matter.

The mullite phase (3Al ₂ O ₃ .2Si
_{O 2 ~3Al 2 O 3 · SiO} 2) of the atomic ratio Al / Si
In each case, it was detected by EDX that it increased from the inside to the outside of the film. As a result, the composition ratio of the mullite phase itself becomes “3Al ₂ O ₃ .2SiO ₂ → 3Al ₂ O
Tendency to tilt to ₃ · SiO ₂ "direction has been found. This is due, in some cases, to both the trace thermal decomposition of the outermost surface alumina and the outermost surface mullite formed in the initial oxidation of the intermediate layer.

The atomic ratio O / N is Si ₃ N ₄ -3Al ₂ O.
_In Reference Example 5 on the ₃ / AlN mixed line, the hexagonal cracks in the intermediate layer were despite the efforts to optimize the hot pressing conditions.
I couldn't control it.

However, no cracks were observed on the outermost surface having the oxide layered thereon. ED of laminated body cross section
X observation revealed that cracks in the intermediate layer and cracks extending to the base material were oxides (mullite rich in SiO ₂ ).
It was found to be backfilled with.

In order to confirm the self-repairing effect of the surface layer oxide, separately, on the surface of the laminate of Examples 5, 9 and 14 (mullite surface layer 0.3 mm: intermediate layer 0.6 mm: substrate 5 mm),
Diamond cutter (0.1mm thickness) 0.5, 1.
A sample with 0, 2.0 mm cuts was placed in a simulated vertical atmosphere of a Keramax heating element alumina core tube in a simulated atmosphere at 175
A 0 ° C. treatment test was conducted.

At the cuts of 0.5 mm and 1.0 mm, the initial groove was completely repaired regardless of the kind of the substrate. With a 2.0 mm incision, the repair status is affected somewhat by the type of substrate, and S
It was confirmed that the repair was incomplete in the order of iC>AlN> Si ₃ N ₄ .

Further, in a simulated atmosphere 1750 ° C. treatment test in a sample in which a slurry of fine powder of Al ₂ O ₃ or SiO ₂ was applied on the surface and impregnated with a notch of 2.0 mm, the initial groove repair effect was partially improved. Was recognized. There are two combinations of Si ₃ N ₄ base material-Al ₂ O ₃ powder and AlN base material-SiO ₂ powder that show remarkable improvement effects, and the combination of SiC base material-Al ₂ O ₃ powder shows some effect. Was given.

Test Example The test method of the present invention is very effective in detecting the occurrence of cracks in a ceramics sintered body having a laminated structure having an oxide as a surface layer. Hereinafter, Test Examples 1 to 5 will be described with reference to FIGS. 9 to 16.

Test Example 1 (FIGS. 9 and 10) As shown in FIG. 9, the test piece 10 used in this example has a non-oxide (SiN ₄ ) substrate 11 and an oxide (Al ₂ O ₃ ) surface layer. 12 is formed, and an intermediate layer 13 having, for example, a gradient composition of both materials is formed at the interface between both layers. The surface layer 12 of this test piece 10 is internally provided with carbon fibers 14.

An electric resistance measuring device is connected to the carbon fiber 14 of the test piece 10 in the same manner as the device shown in FIG. 2, and the bending test of the test piece 10 is performed in an atmosphere of high temperature air of 1500 ° C. I went there.

Then, the change of the electric resistance of the carbon fiber 14 corresponding to the tensile stress on the surface layer 12 side which occurred in this case was examined.

FIG. 10 shows the relationship between the stress and strain of the surface layer 12 (characteristic line E) and the change in the electrical resistance of the carbon fiber 14 (characteristic line F) in this case. From these characteristic lines E and F, it is recognized that the electric resistance increases at a stage well before the fracture of the surface layer 12.

This indicates that even if a slight crack is generated in the surface layer 12 of the test piece 10, the carbon fiber 14 comes into contact with the high temperature atmosphere and is oxidized, thereby significantly increasing the electric resistance. Therefore, it was confirmed that the progress of cracks in the surface layer 12 can be sensitively detected under the limitation that it is used in an oxidizing atmosphere.

Test Example 2 (FIGS. 11 and 12) In this example, as shown in FIG. 11, the surface layer 12 of the same test piece 10 as described above was hit with a hammer 15 to thereby give a carbon fiber 14 when an impact load was applied. This is the result of examining the resistance change of. In the case of this example as well, the test was performed in an atmosphere of high temperature air of 1500 ° C.

In this case, as shown in FIG. 12, the electrical resistance rapidly increased at time point a immediately after the impact. From this,
It was confirmed that the resistance change due to the oxidation of the carbon fiber 14 can be detected even when the crack is suddenly generated.

Therefore, for example, it becomes possible to take measures such as repair at the time when a flying object collides with the gas turbine blade to cause a crack, that is, at an early stage before the entire blade is broken, and complete safety measures are taken. It turned out to be extremely effective on the above.

Test Example 3 (FIGS. 13 and 14) In this example, as shown in FIG. 13, a test piece 10 similar to that described above was placed in an atmosphere of high temperature air at 1500 ° C. for a long time, and the electricity of the carbon fiber 14 in that case was changed. The change in resistance was investigated.

As a result, as shown in FIG. 14, it was confirmed that the electric resistance gradually increased.

From this, it was found that the diffusion of oxygen in the oxide (Al ₂ O ₃ ) partially oxidizes the carbon fiber to reduce its diameter and gradually increase the resistance.

Therefore, the inspection method of the present invention can be effectively applied to, for example, a monitor showing a very weak degree of progress of oxidation.

Test Example 14 (FIG. 15) In this example, the test piece having the structure shown in Example 2 (FIG. 5), that is, not the carbon fiber but the barium oxide layer 7 was used as the substrate 6.
The test piece was tested by the same method as in Test Example 1 above by applying the test piece placed in the vicinity of the surface.

A test piece was placed in an atmosphere of flowing high temperature air (air flow) of 1500 ° C. to perform a bending test, and a vapor pressure monitor of barium oxide was placed downstream of the air flow to detect barium oxide gas. went.

As a result, as shown by characteristic lines E and F (same as Test Example 1) in FIG. 15, it was confirmed that the vapor pressure of barium oxide increased sharply before the bending rupture.
Similarly, it was found that early crack detection can be performed by remote gas detection. From this, for example, if the structure of this test piece is adopted for a blade of a gas turbine and a vapor pressure monitor of barium oxide is arranged at the outlet of the gas passage, the occurrence of blade cracks can be detected early. It is recognized that the invention is useful for safety measures.

Test Example 5 (FIG. 16) In this example, an impact load was applied to a test piece using barium oxide as in Test Example 4 by the same method as in Test Example 2,
The change in the detected gas pressure in that case is examined.

In the same manner as in Test Example 4 described above, this example also
A rise in the vapor pressure of barium oxide was observed at point b early after the impact, and as a result, it was found that the method of this example can also be effectively applied to the prevention of impact damage due to collision of flying objects.

[0118]

As described in detail above, according to the inventions of claims 1 and 2, the progress of oxidation and cracks can be detected by the fibers and other detection media provided inside the ceramic sintered body. Therefore, the parts used in a high temperature oxidizing atmosphere such as a gas turbine can be continuously inspected even during operation, and the reliability of the ceramic sintered body can be improved.

According to the inventions of claims 3 and 4, 170
Si ₃ N ₄ ceramics, SiC ceramics, AlN ceramics-based heat resistant coating composite materials, etc. can be realized as high-strength and oxidation-resistant structural members that can withstand high-temperature combustion gas of 0 ° C or higher. We can find a way to improve efficiency by climbing.

Even if a surface crack occurs in the mounting member,
The self-repairing action works during the high-temperature mounting operation, and the self-repairing can be promoted by applying a predetermined slurry, so that the industrial value of the high-temperature structural laminated ceramic member can be increased.

[Brief description of drawings]

FIG. 1 is a view schematically showing an image of a cross section of a ceramics sintered body according to Example 1 of the present invention, which is taken by a micrograph.

FIG. 2 is a diagram schematically showing a cross section of a rotating body in which a ceramic sintered body according to Example 1 of the present invention is put into practical use by providing wiring for electric resistance measurement.

FIG. 3 is a time-electrical resistance curve obtained when an oxidation test was performed on the ceramic sintered body according to Example 1 of the present invention at 1500 ° C.

FIG. 4 is a load-electrical resistance curve obtained when a three-point bending test based on JIS is performed using the ceramics sintered body according to Example 1 of the present invention.

FIG. 5 is a diagram schematically showing an image of a cross section of a ceramics sintered body according to Example 2 of the present invention, which is taken by a micrograph.

FIG. 6 is a load-vapor pressure curve obtained when a three-point bending test based on JIS is performed using the ceramics sintered body according to Example 2 of the present invention.

FIG. 7 is a diagram schematically showing an image of a cross section of a ceramic sintered body according to Comparative Example 3, taken by a micrograph.

[FIG. 8] Using a ceramic sintered body according to Comparative Example 3,
The load-current value curve obtained when performing the 3-point bending test based on JIS.

FIG. 9 is an enlarged sectional view of a test piece showing Test Example 1 of the present invention.

FIG. 10 is a characteristic diagram showing test results according to Test Example 1 of the present invention.

FIG. 11 is a schematic diagram of a test state showing Test Example 2 of the present invention.

FIG. 12 is a characteristic diagram showing test results according to Test Example 2 of the present invention.

FIG. 13 is an enlarged sectional view of a test piece showing Test Example 3 of the present invention.

FIG. 14 is a characteristic diagram showing test results according to Test Example 3 of the present invention.

FIG. 15 is a characteristic diagram showing test results according to Test Example 4 of the present invention.

FIG. 16 is a characteristic diagram showing test results according to Test Example 5 of the present invention.

[Explanation of symbols]

 2 Substrate (Silicon Nitride Ceramics) 3 Carbon Fiber 4 Electrical Resistance Measuring Device 5 Wiring 6 Substrate (Silicon Nitride Ceramics) 7 Barium Oxide Layer 8 Substrate (Silicon Nitride Ceramics) 9 Yttrium Oxide Layer 10 Test Piece 11 Substrate 12 Surface Layer 13 Intermediate Layer 14 carbon fiber 15 hammer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location G01N 21/78 C 27/04 Z (72) Inventor Masanori Kato Komukai, Kawasaki City, Kanagawa Prefecture Toshiba Town No. 1 Inside Toshiba Research and Development Center

Claims (4)

[Claims] 1. A ceramic sintered body mainly composed of non-oxide ceramics, or a ceramic structure having a layered structure in which a surface layer mainly composed of oxide ceramics is formed on the surface of a base body mainly composed of non-oxide ceramics. A ceramic sintered body, which is a bonded body, in which a sensing medium which causes a chemical or physical change in response to oxidation or damage is internally provided near the surface. 2. The ceramic sintered body according to claim 1 is used in an oxidizing atmosphere, and chemical or physical changes in a detection medium of the ceramic sintered body are detected by electrical, gas analytical or optical changes. The method for inspecting a ceramics sintered body according to claim 1, wherein the oxidation or damage of the ceramics sintered body is inspected outside the ceramics sintered body. 3. A surface layer mainly composed of oxide ceramics is formed on the surface of a base body mainly composed of non-oxide ceramics.
A ceramics sintered body having a layered structure formed through an intermediate layer, wherein the intermediate layer is mainly composed of an oxide or a similar oxide that constitutes a surface layer by oxidizing the intermediate layer in an oxidizing atmosphere. A ceramics sintered body characterized by being formed of a material that produces a product. 4. An AlN-SiC solid solution layer (Si) is formed on the surface of the SiC ceramics base material or the AlN ceramics base material.
C: AlN = 1: 2 to 1: 6) and further mullite (3Al ₂ O ₃ .2SiO _{2 to} 3Al ₂ O _3. )
A ceramics sintered body characterized by being coated with an oxide composite layer of SiO ₂ ) and alumina (Al ₂ O ₃ ).