JP2528780B2 - Oxidation resistant carbon fiber reinforced carbon composite material and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon fiber reinforced carbon composite material having oxidation resistance and a method for producing the same.

[0002]

2. Description of the Related Art Carbon fiber reinforced carbon composite materials (abbreviated as C / C materials) are extremely excellent in high temperature strength and heat resistance, and are applied to aerospace fields and high temperature members such as reactor members. Are beginning to be implemented, and it is expected that the fields of application will expand. C
Since the / C material suffers from oxidative damage from about 500 ° C, it is usually used for high temperature parts used in an atmosphere containing oxygen.
/ C Material Surface Chemical Vapor Deposition (Chemical Vapor Deposition)
The silicon carbide coating (SiC-CVD) by the por deposition method is used. However, the coefficient of thermal expansion of the C / C material (coefficient of thermal expansion between room temperature and 1000 ° C .: about 1.2 × 10 ⁻⁶ / ° C.) and the SiC-CVD layer (about 4.8 × 10 ⁻⁶ / ° C.) Because it is different, C
After the VD treatment, cracks are generated on the surface of the SiC / CVD layer and problems such as deterioration of adhesion strength occur. Oxygen penetrates through these cracks and cannot completely impart oxidation resistance. A silicon nitride coating (Si ₃ N ₄ · CVD: about 2.8 × 10 ⁻⁶ / ° C.) having a small coefficient of thermal expansion may be used, but the same problem occurs.

As a countermeasure against this crack, SiO ₂ , Al ₂ O
Glass-based ceramics such as ₃ , B ₂ O ₃ and SiC-C
The method used for sealing the cracks in the VD layer is first mentioned. FIG. 2 shows the above conventional example, in which a SiC layer 12 is provided on the surface of a carbon fiber reinforced carbon composite material (C / C material) 10,
In order to seal the cracks 14 in the SiC layer 12, B ₂ O
_{The three} layers 16 are provided.

As another method, C / C material and SiC-
A method of relaxing the stress concentration of the SiC-CVD layer and reducing cracks by providing a porous SiC layer or a CVD coating layer having a composition that gradually changes from carbon to SiC between the CVD layers has also been studied. FIG. 3 shows the above conventional example, in which the porous SiC layer 1 is formed on the surface of the C / C material 10.
8 is provided, the SiC layer 12 is provided on the surface of the porous SiC layer 18, and the SiO ₂ .Al ₂ O ₃ layer 20 is provided for sealing the cracks 14 in the SiC layer 12. Further, the matrix carbon on the surface of the C / C material is changed to SiC by a gas phase or liquid phase reaction,
There is also a technique for improving the adhesion with the C-CVD layer.

Further, Japanese Patent Laid-Open No. 2-74668 discloses that
Porous SiC as an oxidation resistant film on the surface of C / C material
An oxidation resistant C / C material is described which has an inner layer of the coating and an outer layer of a SiC coating by the diffusion method on this inner layer.

Further, in Japanese Patent Laid-Open No. 1-2496959, carbon and / or
Alternatively, a method for producing a C / C material having oxidation resistance, in which ceramics is deposited by deposition and then the surface of the filling material is deposited by vapor phase decomposition to deposit ceramics or both ceramics and carbon, is described.

[0007]

The object of the invention is to be Solved by the above-mentioned SiO _2, Al
_The method of using glassy ceramics such as ₂ O ₃ and B ₂ O ₃ as a crack sealing material is very effective in a short time in the atmosphere, but due to volatilization and scattering of the sealing material, low pressure It is not satisfactory for use under high or high-speed gas flow and long-term use. In addition, C / C material and SiC-C
The method of providing a porous SiC layer or a CVD coating layer having a composition gradually graded from carbon to SiC between VD layers is considered to be very effective for adhesion and the like.
Although it is considered to have an effect of slightly reducing the cracks in the iC-CVD layer, a coating method having excellent durability has not been confirmed yet.

Finally, Si of the surface matrix of C / C material
Carbonization is effective in terms of adhesion between the coating layer and the base material, but is not effective in reducing cracks in the SiC-CVD layer. Further, in Japanese Patent Application Laid-Open Nos. 2-74668 and 1-249659, the technical idea of "a plurality of coating layers made of at least two kinds of ceramics are further laminated" which is a feature of the present invention. Has not disclosed anything.

The present invention has been made in view of the above points, and an object of the present invention is to provide a C / C material having few surface cracks, a narrow crack width, and excellent oxidation resistance, and a method for producing the same. .

[0010]

In order to achieve the above object, the oxidation-resistant C / C material of the present invention has a plurality of coating layers 22 made of at least two kinds of ceramics, as shown in FIG. A multilayer coating layer formed by further laminating a plurality of layers 24 is provided on the surface of the carbon fiber reinforced carbon composite material 10.

In this case, it is preferable that the ceramic of the inner coating layer 22 has a higher coefficient of thermal expansion than the ceramic of the other coating layer 24. Moreover, as one of the constituent materials of the multilayer coating layer, SiC or Si _{3 is used.}
It is preferred to use N ₄ .

The method for producing the oxidation resistant C / C material of the present invention is as follows:
The following steps (a) to (c), that is, (a) a step of forming a plurality of coating layers made of at least two kinds of ceramics on the surface of the carbon fiber reinforced carbon composite material, (b) the (a) Forming a multi-layer coating layer by repeating the above-mentioned step at least twice, (c) 300-3000 ° C. until the completion of the construction of the multi-layer coating layer.
And the step of holding.

Also in this case, it is preferable to use ceramics having a higher coefficient of thermal expansion than the ceramics of the other layers on the inner layer side. Further, it is preferable to use SiC or Si ₃ N ₄ as one of the constituent materials of the multilayer coating layer.

On the surface of the C / C material 10 several μm to several hundred μm
A plurality of layers 22 and 24 of two or more kinds of ceramics having a thickness (for example, several μm to 10 μm) are repeatedly laminated to form a multilayer, and several tens of μm to 1 mm (for example, 100 to 200 μm) on the outermost surface
By providing the ceramic coating layer 12 which is one of the constituent materials of the multi-layer coating having a thickness of 1) (preferably thicker than the above layers), a C / C material having excellent oxidation resistance can be obtained. . It should be noted that these coating treatments are performed in the furnace for 300 to 3000 until the end of all steps.
It is carried out continuously while maintaining a high temperature of ℃. Examples of the coating method include a chemical vapor deposition (CVD) method, an ion plating method, a sputtering method, and a thermal spraying method, but they are not limited thereto.

In the case of the manufacturing method of forming a multi-layer coating by introducing a temperature lowering process to less than 300 ° C. for each coating of each layer, the coating is caused by the difference in thermal expansion from the C / C material when the first layer is cooled. The layer cracks and the second
In the coating layers after the layer, cracks are generated at the same position without stress relaxation, and wide cracks that penetrate the multilayer coating layer as in the case of the single layer coating are generated. Therefore, in the present invention, it is necessary to maintain a high temperature of 300 ° C. or higher. The upper limit of temperature is 3000
° C is sufficient.

Referring again to FIG. 1, on the outermost surface of the multilayer coating layer, as described above, the ceramic coating layer 12 which is one of the constituent materials of the multilayer coating layer.
(24) is provided. Further, in order to seal the cracks 14 in the coating layer 12 (24), SiO 2 is used.
_{A 2} · Al ₂ O ₃ layer 20 is provided.

The SiO ₂ .Al ₂ O ₃ layer 20 is made of TE.
OS (Tetraethyl Ortho Silic)
ate) processing and MAP (Mono Aluminium)
mPhosphate) treatment. The TEOS treatment is a treatment in which, for example, a surface of a silicon carbide coating is impregnated with an organic silicon solution containing oxygen, and then thermally decomposed to deposit quartz glass (SiO ₂ ).
In addition, in the MAP treatment, aluminum phosphate is impregnated on the TEOS-treated silicon carbide coating surface to obtain about 1000
Aluminum oxide (Al ₂ O ₃ ) by thermal decomposition at ℃
A layer is formed.

The ceramic material used in the present invention is preferably one having excellent heat resistance and oxidation resistance.
Specifically, carbide-based materials such as SiC, TiC, HfC, ZrC and NbC, nitride-based materials such as Si ₃ N ₄ , TiN, HfN and ZrN, oxides such as Al ₂ O ₃ and ZrO ₂ and TiB.
Borides such as ₂ can be used. In the C / C material having the above multi-layer coating, a single layer of Si is used.
C-CVD layer or C having Si ₃ N ₄ · CVD layer
Compared with the / C material, cracking of the outermost surface coating layer is significantly reduced.

The reason for the improvement will be shown below by taking a multilayer coating by alternately laminating two kinds of ceramics as an example. In the temperature decreasing process after coating, cracks are first generated in the coating layer (first layer) closest to the substrate. When the crack generated in the first layer reaches the next layer (second layer), the stress state is different between the first layer and the second layer, so that the crack propagation slows at the interface. This is repeated,
It is considered that the closer to the surface, the slower the crack propagation, resulting in a considerable reduction of cracks in the outermost main coating layer. It is also possible to subject the C / C material having the above-mentioned multilayer coating to the sealing treatment with the above-mentioned glassy ceramics or the like. It is also possible to apply a coating such as ZrO ₂ or Al ₂ O ₃ which is being studied as a measure against erosion resistance and high temperature. Further, it can be used in combination with a technique for converting the surface carbon matrix of the C / C material into SiC.

In the present invention, as described above, when the ceramics of the inner layer has a higher coefficient of thermal expansion than the ceramics of the other layer, a particularly excellent effect is exhibited. For example, this is a case where the inner layer is a TiC layer and the surface layer of this TiC layer is a SiC layer. Hereinafter, the reason why it is advantageous in strength when the TiC / SiC multilayer coating is adopted will be described.

First, Table 1 shows the physical property values of C / C, SiC and TiC.

[Table 1]

SiC to C / C, 1
In the case of layer coating, a relatively large tensile stress is generated in the SiC layer due to the difference in thermal expansion during cooling (the coefficient of thermal expansion of SiC is larger than that of C / C, and the layer thickness is C / C).
SiC is thinner than C). Therefore, the SiC layer is cracked by tensile stress. When C / C is coated with one layer each of TiC and SiC in this order, Ti due to the difference in thermal expansion during cooling
A large tensile stress occurs in the C layer (because the coefficient of thermal expansion of TiC is larger than that of SiC). Therefore, it is expected that the tensile stress generated in the SiC layer will be more relaxed than in the case of, and cracking of the SiC layer will be less likely to occur.

In the TiC layer, a tensile stress higher than the tensile stress generated in the SiC layer in the case of occurs, and a crack occurs, but the interface between TiC and SiC has an effect of preventing the crack from progressing. Expected to be, T
It is considered that the cracks generated in the iC layer do not easily propagate to the surface. Further, in order to reduce cracks generated in the TiC layer, a material having high tensile strength and high ductility may be used instead of the TiC layer (in this case, since the SiC layer is present on the surface, there is a problem in oxidation resistance. It may be a metallic material). When C / C is multilayer-coated in the order of TiC and SiC, the TiC layer closest to C / C has a large tensile stress due to the difference in thermal expansion during cooling. Therefore, Ti closest to C / C
The C layer is cracked. The cracks in the TiC layer are
Propagation will be stopped at each interface of the C and SiC multilayer coatings. The other TiC layer is not directly bonded to the C / C layer, and the stress is released when the TiC layer closest to the C / C is cracked, so the tensile stress generated is the TiC layer closest to the C / C. It is considered to be smaller than that of, and cracking is unlikely to occur.

[0024]

EXAMPLES The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to the following examples, and various modifications may be made without departing from the scope of the invention. Is possible. Example 1 After alternately laminating a 5 μm TiC layer and a SiC layer on the surface of a C / C material twice, a 5 μm TiC layer was formed on the surface of this layer, and a 100 μm SiC layer was continuously formed by CVD. Laminated. Construction temperature is 800 when TiC layers are laminated
The temperature was kept at 1,200 ° C. when the SiC layer was laminated. FIG.
It is a scanning electron micrograph (magnification: 500 times) of this sample. As a result of surface observation, it was confirmed that surface cracks were extremely small and the width of the cracks was small as compared with the conventional method shown in Comparative Example 1 described later. It was There was almost no change in the weight of this sample after 10 times repeated oxidation tests of 1500 ° C. for 1 hour in the air, and no change in the surface condition was observed.

Comparative Example 1 A 100 μm SiC single layer was applied to the surface of a C / C material by CVD. FIG. 5 is a scanning electron microscope photograph (magnification: 500 times) of this sample. As a result of observing the surface of this sample,
The presence of numerous wide surface cracks was confirmed. The weight loss of this sample was 100 mg / cm ² after two repeated oxidation tests of 1500 ° C. for 1 hour, and the C / C material was severely damaged by oxidation.

[0026]

As described above, the present invention has the following effects. (1) Since multilayer coating is performed by repeating alternating lamination of two or more types of ceramics two or more times,
The stress state differs between the first layer and the second layer, and crack propagation slows down at the interface. By repeating this, the closer to the surface, the slower the crack propagation, and the cracks in the outermost main coating layer are reduced. (2) It is more effective when the inner layer ceramics has a higher coefficient of thermal expansion than the other layer ceramics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of an oxidation resistant carbon fiber reinforced carbon composite material (C / C material) of the present invention.

FIG. 2 is a sectional view showing an example of a conventional oxidation resistant C / C material.

FIG. 3 is a sectional view showing another example of a conventional oxidation resistant C / C material.

FIG. 4 is a scanning electron micrograph (magnification: 500 times) showing the structure of the ceramic material on the surface of the oxidation resistant C / C material in Example 1 of the present invention.

[5] on the surface of the oxidation resistant C / C material in Comparative Example 1
3 is a scanning electron micrograph (magnification: 500 times) showing the structure of the ceramic material in the sample.

[Explanation of symbols]

10 carbon fiber reinforced carbon composite material (C / C material) 12 SiC layer 14 crack 16 B ₂ O ₅ layer 18 porous SiC layer 20 SiO ₂ · Al ₂ O ₃ layer 22 coating layer (TiC layer) 24 coating layer (SiC layer) )

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ken Takashima 1-1 Kawasakicho, Akashi-shi, Hyogo Kawasaki Heavy Industries Ltd. Akashi factory (72) Inventor Hitoshi Tabata 1-1 Kawasakicho, Akashi-shi, Hyogo Kawasaki Heavy Industry Co., Ltd. Akashi Plant (72) Inventor Takao Yoshikawa 1-1 Kawasaki-cho, Akashi City, Hyogo Prefecture Kawasaki Heavy Industries Ltd. Akashi Plant (72) Inventor Hiroyasu Nishikawa 1-1, Kawasaki-cho, Akashi City, Hyogo Prefecture Kawasaki Heavy industry Co., Ltd. Akashi factory

Claims (6)

(57) [Claims] 1. A surface of a carbon fiber reinforced carbon composite material (10) comprising a multi-layer coating layer formed by laminating a plurality of coating layers (22), (24) made of at least two kinds of ceramics. An oxidation resistant carbon fiber reinforced carbon composite material. 2. The oxidation resistant carbon fiber reinforced carbon composite material according to claim 1, wherein the ceramics of the inner layer has a higher coefficient of thermal expansion than the ceramics of the other layer. 3. The oxidation resistant carbon fiber reinforced carbon composite material according to claim 1, wherein one of silicon carbide and silicon nitride is used as one of constituent materials of the multi-layer coating layer. 4. The following steps (a) to (c), namely, (a) a step of forming a plurality of coating layers made of at least two kinds of ceramics on the surface of the carbon fiber reinforced carbon composite material, (b) ) A step of forming the multi-layer coating layer by repeating the step (a) at least twice, and (c) a step of completing the multi-layer coating layer until the construction is completed.
The method for producing an oxidation resistant carbon fiber reinforced carbon composite material, which comprises a step of maintaining the temperature at 00 to 3000 ° C. 5. The oxidation resistant carbon fiber reinforced carbon composite material according to claim 4, wherein a ceramic having a higher coefficient of thermal expansion than the ceramic of the other layer is used on the inner layer side, and the method for producing the same. 6. The oxidation resistant carbon fiber reinforced carbon composite material according to claim 4 or 5, wherein one of silicon carbide and silicon nitride is used as a constituent material of the multilayer coating layer. Method.