JP3228489B2 - Surface treatment method for C / C material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a C / C material (carbon / carbon composite material) used as a material for parts, parts and products requiring heat resistance, oxidation resistance, corrosion resistance and the like. The present invention relates to a surface treatment method for a C / C material used for further improvement.

[0002]

2. Description of the Related Art With the recent development of material development technology,
Beyond conventional metal-based materials, ceramic-based materials have been developed, and fiber-reinforced metals (FRM), fiber-reinforced ceramics (FRC), and carbon / carbon composites (C / C materials) have been developed. Has been reached.

[0003] The C / C material is lightweight, has good heat and corrosion resistance, and suffers much less wear and strength reduction due to heat than conventional metal-based materials. Suitable for applications exposed to a severe thermal environment.

[0004] Even with such lightweight and heat / corrosion resistant C / C material, its surface characteristics are further improved, especially its oxidation resistance is improved. It can also be applied to parts that are thermally strict and require high strength and rigidity, such as the nose cap and leading edge of round-trip aircraft, where the maximum temperature at reentry into the atmosphere greatly exceeds the heat resistance limit of metal structural materials. to be able to do,
An oxidation-resistant surface coating method for forming a SiC coating on the surface of a C / C material has been developed.

In this oxidation-resistant surface coating method, the surface of the C / C material is subjected to SiC diffusion treatment and SiC vapor deposition treatment (for example, H ₂
/ CH ₃ SiCl ₃ CVD atmosphere in mixed gas atmosphere)
There is known a method of forming a SiC coating layer by combining the above.

In the SiC coating method using the combination of the SiC diffusion process and the SiC vapor deposition process, oxidation treatment to a curved surface is easy, a surface coating of a complicated shape is possible, and the thickness of the SiC coating layer is increased. Can be easily controlled, but in the process of cooling after forming the SiC coating layer, the thermal expansion coefficient of the C / C material (about 1.2 to 2 × 10 ⁻⁶ / ° C.) Due to the difference from the thermal expansion coefficient (about 3.5 to 4 × 10 ⁻⁶ / ° C.) of the SiC coating layer, for example, a width of about 1 to 10 μm and a depth of 1
Since a large number of fine cracks of about 00 μm are generated, the resistance such as heat resistance and oxidation resistance against hot air at the time of re-entry into the atmosphere is impaired, so that crack sealing must be performed.

At the time of the crack sealing, for example, the fine cracks are impregnated with tetraethyl orthosilicate (TEOS) and heat-treated, so that the fine cracks contain Si.
In addition to a method of adhering O ₂ , a method of impregnating a fine crack with a silicic acid coating agent as a silicon modifier and heat-treating the same to deposit SiO ₂ in the fine crack, etc. Mullite (Al ₂ O
₃・ SiO ₂ ) is adhered by sol-gel method,
Methods for further improving resistance such as oxidation resistance have also been developed.

FIG. 5 shows an example of a mullite crack sealing method by the sol-gel method.
After washing and drying the surface of the C / C material, Al ₂ O ₃ powder and SiO ₂ powder (having a particle size on the order of tens of angstroms) were prepared at a molar ratio of 1: 1 to obtain a powder such as methanol. The C / C material is immersed in a colloid solution (sol) by mixing with a solvent, vacuum impregnation and ultrasonic application are performed, and then the vacuum process is completed to complete the immersion step. Then, as shown in FIG. Drying in air at 60 ° C. for 10 minutes (excessive solvent and liquid are quickly dried) and 15
Drying in the air at 0 ° C. for 20 minutes (removing unreacted and high-boiling-point solvent) is performed to complete the drying step.
At low temperature in the atmosphere (the mullite ceramic for sealing is buried in the fine cracks by degassing and shrinking of the alcohol in the gel body and fixed to the surface of the SiC coating layer).
To complete the low-temperature firing step, and by repeating such immersion, drying and low-temperature firing steps for several cycles,
As shown in FIG. 7A, a SiC coating layer 13 having a thickness of about 100 ± 20 μm covered with a SiC diffusion layer 12 having a depth of about 50 ± 20 μm formed on the surface of the C / C material 11. The microcracks 14 formed in the above are sealed with the mullite ceramics for sealing 15 (15a), and the surface of the SiC coating layer 13 is coated with the same mullite ceramics for sealing 15 (15b) having a film thickness of about several μm.

Here, the sealing mullite ceramics 15 (15a, 15b) are in a semi-crystalline state, and about 10% by weight of the solvent remains.

[0010]

The surface of such a C / C material is subjected to SiC diffusion treatment + SiC vapor deposition (CVD) treatment +
C / C with mullite ceramics for sealing
As a simulation test for the C material, the nose cone of the flying object and the back side of the leading edge are in a reduced pressure state of about 1 Pa when re-entering the atmosphere.
a, When the high temperature resistance test for 1100 seconds was performed for 10 cycles, the surface of the SiC coating layer 13 was under reduced pressure and high temperature as shown in FIG.
+ O ₂ → SiO (g) + CO (g)), and the solvent remaining in the sealing mullite ceramics 15 evaporates and scatters and the crystallization of the sealing mullite ceramics 15 in a semi-crystalline state. Of the mullite ceramics for sealing 15 (15a, 15b)
The mullite ceramics 15 for sealing is peeled off from the SiC coating layer 13 and the fine cracks 14 due to the low fixing force to the C / C material 11 due to the occurrence of an oxygen attack inside the fine cracks 14. Because it is oxidized (a reaction of C + O ₂ → CO ₂ occurs),
Since there was a problem that the oxidation resistance might be reduced, it was a problem to prevent the reduction of the heat resistance and the oxidation resistance particularly under a reduced-pressure and high-temperature environment.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has an object to improve the surface of a C / C material by using SiC.
Surface of SiC coating layer coated via diffusion layer and Si
In the case where the fine cracks formed in the C coating layer are subjected to ceramic sealing, a C / C material capable of preventing a decrease in heat resistance and oxidation resistance even when exposed to a reduced pressure and high temperature environment. It is intended to provide a surface treatment method.

[0012]

The surface treatment method for a C / C material according to the present invention comprises:
The C / C material on which the coating layer has been formed is brought into contact with a solvent (sol-like colloid solution) containing the ceramic powder for sealing, and the fine ceramic cracks formed on the surface of the SiC coating layer and on the SiC coating layer. After adhering to the inside of the
At 550 ° C. and in the air, the solvent is removed (gelling), and the sealing ceramic is fixed to the surface of the SiC coating layer and the inside of the fine cracks. High temperature firing for increasing the temperature is performed at 1100 to 1250 ° C. in a non-oxidizing atmosphere to fix the ceramic sealing material on the surface of the SiC coating layer and inside the fine cracks.

[0013] In an embodiment of the surface treatment method for a C / C material according to the present invention, the SiC diffusion layer and the SiC coating layer may be formed by a diffusion treatment and a chemical vapor deposition (CVD) method. In the same manner, in the embodiment, vacuum impregnation can be used together with the solvent containing the ceramic powder for sealing, and ultrasonic waves can be given when contacting with the solvent containing the ceramic powder for sealing. be able to.

In an embodiment of the method for surface treating a C / C material according to the present invention, the ceramic sealing material may be a mullite sealing material, and the solvent may be an alcohol. Alternatively, crack sealing can be made sufficiently satisfactory by repeating contact, drying, and low-temperature firing a plurality of times and then firing at a high temperature, or by repeating contact, drying, low-temperature firing, and high-temperature firing multiple times. Or the sealing can be made sufficiently good.

The C / C material to which the surface treatment method for a C / C material according to the present invention is applied is formed on the surface of the C / C material through a SiC diffusion layer.
iC coating layer is formed, for example, 10% by weight
A powder composed of Al ₂ O ₃ +30 wt% Si + 60 wt% SiC is packed around a C / C material in a graphite container, and heated at about 1650 ° C. in an argon atmosphere to convert the surface of the C / C material into SiC. Invert,
It may have a SiC coating layer formed on the surface via a SiC diffusion layer, or a C / C material may be charged into a high-temperature, low-pressure vessel and mixed with an H ₂ / CH ₃ SiCl ₃ gas atmosphere.
/ C material surface by vapor deposition method (CVD method)
C is deposited, and a combination of the SiC diffusion process and the SiC deposition process allows the
It may have a coating layer.

In the process of cooling after forming the SiC coating layer, the thermal expansion coefficient of the C / C material (about 1.2 to
2 × 10 ⁻⁶ / ° C.) and the thermal expansion coefficient of the SiC coating layer (about 3.5 to 4 × 10 ⁻⁶ / ° C.), the width of the SiC coating layer is about 1 to 10 μm and the depth is 100 μm. Since a minute crack is generated, the minute crack is sealed to enhance heat resistance and oxidation resistance.

Therefore, in the present invention, at the time of crack sealing, a colloidal solution (sol) obtained by mixing a ceramic powder for sealing with a solvent is brought into contact with a SiC coating layer of a C / C material, and the ceramic powder for sealing is made of SiC. Attached to the surface of the coating layer and inside the fine cracks.

At this time, the colloid solution (sol) and C / C
When the C / C material is brought into contact with the SiC coating layer of the material, the C / C material can be immersed in a colloid solution.
In the immersed state, vacuum impregnation may be used together or ultrasonic waves may be applied so that the ceramic powder for sealing can sufficiently penetrate into the fine cracks.

As ceramics for sealing, mullite (Al ₂ O ₃ .S
iO ₂ ) can be used, in which case Al ₂ O ₃
A colloid solution prepared by mixing powder and SiO ₂ powder at a molar ratio of 1: 1 can be used, and an alcohol such as methanol can be used as the solvent.

Thereafter, drying and low-temperature baking are performed to remove the solvent to make a gel state, and the sealing ceramic is fixed to the surface of the SiC coating layer and the inside of the fine cracks.

In this drying and firing at a low temperature, 50 to 70
The excess solvent or liquid is quickly dried by drying at about
Unreacted and high boiling solvent is removed by drying at about 30 to 170 ° C, solvent in the gel is further removed by drying at low temperature of about 450 to 550 ° C, and the ceramic for sealing is embedded in the fine cracks. At the same time, it can be made to adhere to the surface of the SiC coating layer. In this way, it is desirable to divide into a plurality of stages and dry and fire at a low temperature for an appropriate time.

Further, by sintering at a high temperature, the remaining solvent is completely eliminated, and the crystallization of the ceramic for sealing such as mullite is promoted. It is firmly fixed on the surface of the coating layer and inside the fine cracks.

The temperature at the time of high-temperature sintering is Si
C coating (CVD) processing temperature of 1250-1350 ° C
The temperature is preferably lower than the temperature, and the temperature is preferably set to 1100 ° C. or higher so that the remaining solvent can be sufficiently removed.

At this time, as the temperature at the time of firing at a high temperature is higher, the crystallization of the ceramic for sealing such as mullite progresses. For example, the melting point of mullite is 1584 ° C., and the temperature is lower than the SiC coating (CVD) processing temperature. If the temperature is too high, the microcracks will be closed more and the semi-crystalline mullite may be extruded from between the microcracks. , 1100-125
A suitable temperature is 0 ° C.

The atmosphere for the high-temperature firing is preferably a non-oxidizing atmosphere, for example, an Ar gas atmosphere. When the high-temperature firing is performed in a state where the crack seal has not been made well, the C / C material is formed. It is desirable to prevent oxidation from occurring.

By performing high-temperature baking after performing the above-described immersion, drying, and low-temperature baking a plurality of times, it is possible to perform a sufficiently good crack sealing while shortening the process, but it is further improved. From the viewpoint of enabling crack sealing, immersion, drying, low-temperature firing,
It is also desirable to perform high-temperature baking a plurality of times (that is, perform high-temperature baking for each impregnation step in one cycle), if necessary.

[0027]

In the surface treatment method for a C / C material according to the present invention, since the above-mentioned structure is employed, no solvent remains inside the ceramic sealing material fixed to the fine cracks and the ceramic for sealing is used. The ceramic sealing material after firing at a high temperature is firmly fixed to the surface of the SiC coating layer and the inside of the fine cracks. Even when the ceramic sealing material is exposed to a high temperature environment, the ceramic sealing material does not peel off, and the ceramic sealing material on the surface of the SiC coating layer gradually sublimates when re-entering the atmosphere, and then the SiC
Even if the coating layer sublimates gradually, the ceramic cracking material is firmly fixed inside the fine cracks in combination with the closing of the fine cracks at high temperatures. The / C material itself does not oxidize. Further, by performing low-temperature baking at 450 to 550 ° C., sufficient degassing of the solvent is achieved, and by performing high-temperature baking at 1100 to 1250 ° C., the residual solvent inside the ceramic sealing material is almost completely eliminated and fine cracks are generated. The internal ceramic sealing material is not extruded to the outside due to the shrinkage or blockage of fine cracks at excessively high temperatures, and furthermore, low-temperature firing is performed in the air, and high-temperature firing is performed in a non-oxidizing atmosphere. By doing so
Even when crack sealing is not performed well in the middle of the process, the C / C material does not oxidize.

In the embodiment of the method for treating the surface of a C / C material according to the present invention, the SiC diffusion layer and the SiC
When the coating layer is formed by a diffusion process and a chemical vapor deposition method, the formation of the SiC coating layer is performed well and the SiC coating is hardly peeled off. Oxidation treatment can be performed sufficiently well, and by using vacuum impregnation together with the solvent containing the ceramic powder for sealing, the ceramic for sealing can sufficiently penetrate into the fine cracks. And also
By applying ultrasonic waves upon contact with the solvent containing the ceramic powder for sealing, the ceramic for sealing penetrates sufficiently and uniformly into the inside of the fine cracks, and the sealing of the fine cracks is good. It can be done in.

Further, in the embodiment of the surface treatment method for a C / C material according to the present invention, by making the ceramic sealing material a mullite sealing material, it is possible to perform a sealing with more excellent heat resistance and oxidation resistance. By using the alcohol as the solvent, the S of the ceramic for sealing by the sol-gel method can be obtained.
Adhesion to the surface of the iC coating layer and the inside of the fine cracks is sufficiently performed.

Similarly, in the embodiment of the surface treatment method for the C / C material according to the present invention, the contact, drying, and low-temperature firing are repeated a plurality of times, and then the high-temperature firing is performed. Or
By repeating contacting, drying, low-temperature firing, and high-temperature firing a plurality of times, the number of steps is slightly increased, but the formation of the crack sealing layer is further improved.

[0031]

EXAMPLE 1 A C / C in which a SiC coating (CVD) layer having a thickness of about 100 μm was provided on the surface through a SiC diffusion layer having a depth of about 50 μm by a SiC diffusion process and a SiC coating (CVD) process.
Materials were prepared. The SiC coating layer of the C / C material has a width of 1
Many fine cracks having a depth of about 10 to 10 μm and a depth of about 100 μm are generated.

Next, after performing a stress relieving treatment of the SiC coating layer, as shown in FIG. 1, the surface of the C / C material is washed and dried, and Al ₂ O ₃ powder and SiO ₂ powder (particle size is several The C / C material is immersed in a colloidal solution (sol) obtained by mixing a powder prepared by mixing a powder having a molar ratio of 10 angstroms) at a molar ratio of 1: 1 with a solvent composed of methanol, and performing vacuum impregnation and ultrasonic application. After 20 minutes, the immersion step is completed by evacuating for 10 minutes,
As shown in FIG. 2, drying at 60 ° C. in the air for 10 minutes (excessive solvent and liquid are quickly dried) and 150 ° C.
To dry in the air for 20 minutes (to remove unreacted and high-boiling-point solvent) to complete the drying process. Burying the mullite ceramics in the fine cracks and fixing it to the surface of the SiC coating layer) to complete the low-temperature firing step,
By repeating the low-temperature firing step (step by the sol-gel method) for 5 cycles, as shown in FIG.
S / C having a depth of about 50 μm formed on the surface of the C / C material 1
The microcracks 4 formed on the SiC coating layer 3 having a thickness of about 100 μm covered with the iC diffusion layer 2 are sealed with the mullite ceramics for sealing 5 (5a), and the surface of the SiC coating layer 3 is formed to have a thickness of several μm. Degree (C / C
(Corresponding to 0.4 to 0.5% by weight of the material 1) with the same mullite ceramics 5 for sealing (5b).

Here, the mullite ceramics for sealing 5 (5a, 5b) is in a semi-crystalline state,
About 10% by weight of the solvent remained.

Next, the immersion, drying and low-temperature sintering are repeated five times in this manner, and then the immersion, drying, and
Firing was performed at 200 ° C. for 60 minutes. During this firing, the fine cracks 4 formed in the SiC coating layer 3 are narrowed as shown in FIG. 3B due to the difference in thermal expansion coefficient between the SiC coating layer 3 and the C / C material 1. (However, it is not completely closed), and the fine cracks 4 are slightly spread after firing as shown in FIG. And
In this state, the mullite sealing material 6 (6a, 6b)
When the solvent therein has almost completely disappeared, the remaining solvent is substantially absent, and the crystallization of mullite has been advanced. The mullite sealing material 6 (6a, 6b) was firmly fixed inside the crack 4.

Next, the C / C material obtained by performing the SiC diffusion layer + SiC vapor deposition (CVD) layer + mullite sealing + high-temperature firing on the surface of the C / C material in this way, As a simulation test in which the back side of the nose cone and the leading edge is reduced in pressure to about 1 Pa, 10 cycles of a high-temperature resistance test at 1700 ° C. for 1 Pa and 1100 seconds were performed, and the mullite sealing adhered to the surface of the SiC coating layer 3. Lumber 6 (6
b) gradually sublimated, and further, as shown in FIG. 3D, the SiC coating layer 3 gradually sublimated and the thickness was reduced to about 50 μm after the test, but at a high temperature of 1700 ° C., fine cracks were observed. Since the mullite sealing material 6 (6 a) is firmly fixed inside the fine cracks 4 in combination with the narrowing of the mullite sealing material 4, the mullite sealing material 6 (6 a) remains inside the fine cracks 4. The C / C material 1 was not oxidized even when it was later placed in an environment that caused an oxygen attack in the air atmosphere.

Example 2 A C / C having a SiC coating (CVD) layer having a thickness of about 100 μm provided on the surface thereof through a SiC diffusion layer having a depth of about 50 μm by a SiC diffusion process and a SiC coating (CVD) process.
Materials were prepared. The SiC coating layer of the C / C material has a width of 1
Many fine cracks having a size of about 10 to 10 μm and a depth of about 100 μm are generated.

Next, after performing the stress removing treatment of the SiC coating layer, as shown in FIG. 4, the surface of the C / C material is washed and dried, and the Al ₂ O ₃ powder and the SiO ₂ powder (particle size is several The C / C material is immersed in a colloidal solution (sol) by mixing powder prepared by mixing 1: 1 in a molar ratio of 10 angstrom) with a solvent consisting of methanol, and vacuum impregnation and ultrasonic application. After 20 minutes, the immersion step is completed by evacuating for 10 minutes,
As shown in FIG. 2, drying in air at 60 ° C. for 10 minutes (excessive solvent and liquid are quickly dried) and 15
Drying is completed at 0 ° C. for 20 minutes in the air (removing unreacted and high-boiling-point solvent), followed by low-temperature baking at 500 ° C. in the air (degassing and shrinkage of alcohol in the gel body). Then, the mullite ceramic for sealing is buried in the cracks and fixed to the surface of the SiC coating layer.) To complete the low-temperature firing step.

Next, 1200 hours in an argon atmosphere.
Firing was performed at 60 ° C. for 60 minutes. During this firing,
Due to the difference in thermal expansion coefficient between the SiC coating layer and the C / C material, S
The fine cracks formed in the iC coating layer are narrowed (but not completely closed), and after firing, the fine cracks 4 are in a slightly expanded state. In this state, the solvent in the mullite sealing material is almost completely removed. As a result, the residual solvent is substantially absent, and the crystallization of the mullite has progressed, so that the mullite is strongly solidified on the surface of the SiC coating layer and inside the fine cracks. Is fixed.

By repeating the steps of immersion, drying, low-temperature calcination, and high-temperature calcination (steps by the sol-gel method) for four cycles, the solvent in the mullite sealing material has completely disappeared, and The mullite sealing material in which crystallization of mullite is almost finished is S
It was firmly fixed on the surface of the iC coating layer and also firmly inside the fine cracks.

Next, the C / C material obtained by performing the SiC diffusion process + SiC vapor deposition (CVD) process + mullite sealing + high temperature firing on the surface of the C / C material as described above is as follows.
As a simulation test in which the backside of the nose cone and the leading edge of the flying object at the time of re-entry into the atmosphere becomes a reduced pressure state of about 1 Pa, 10 cycles of a high temperature resistance test at 1700 ° C. for 1 Pa for 1100 seconds were performed. The adhered mullite sealing material gradually sublimates, and further, as shown in FIG.
The coating layer gradually sublimates. At a high temperature of 1700 ° C., the fine cracks become narrower, and the mullite sealing material is firmly fixed inside the fine cracks, so that the mullite sealing material remains inside the fine cracks. 3E after the test, and the C / C material was not oxidized even when it was again placed in an environment that caused an oxygen attack in the air atmosphere.

[0041]

According to the surface treatment method for a C / C material according to the present invention, since the above structure is employed, no solvent remains inside the ceramic sealing material fixed to the fine cracks and the ceramic for sealing is used. The ceramic sealing material after firing at a high temperature is firmly fixed to the surface of the SiC coating layer and the inside of the fine cracks. Even when exposed to a high temperature environment, it is possible to prevent the ceramic sealing material from peeling off, and the ceramic sealing material on the surface of the SiC coating layer gradually sublimates when re-entering the atmosphere, and then the SiC coating layer gradually becomes Even if sublimation occurs, at high temperatures, the ceramic cracks are contained inside the fine cracks, coupled with the closing of the fine cracks. Since the ring material is firmly fixed, a remarkably excellent effect that the C / C material itself can be prevented from being oxidized even when returned to the atmospheric pressure and subjected to an oxygen attack is brought about. . Further, by performing low-temperature baking at 450 to 550 ° C., sufficient degassing of the solvent is achieved, and high-temperature baking is performed at 1100 to 1250 ° C.
It is possible to almost completely eliminate the residual solvent inside the ceramic sealing material by performing the above, and to prevent the ceramic sealing material inside the fine cracks from being extruded to the outside due to the shrinkage or blockage of the fine cracks at an excessively high temperature. By performing low-temperature firing in the air and performing high-temperature firing in a non-oxidizing atmosphere, C / C can be prevented even when crack sealing is not performed well in the middle of the process. C
An excellent effect is obtained that oxidation of the material can be prevented.

In the embodiment, the SiC diffusion layer and the SiC coating layer are formed by a diffusion process and a chemical vapor deposition method, so that the SiC coating layer can be formed well. It is possible to make it difficult for the SiC coating layer to peel off, and it is possible to sufficiently perform the oxidation resistance treatment on the C / C material. By using vacuum impregnation at the time of contact, it is possible to sufficiently penetrate the ceramic for sealing into the inside of the fine cracks, and to apply ultrasonic waves when contacting with the solvent containing the ceramic powder for sealing. As a result, the ceramic for sealing can be sufficiently and deeply introduced into the fine cracks. It is possible to ingress to one results in excellent effect that it is possible to satisfactorily carry out the sealing of fine cracks.

Further, in the same embodiment, by making the ceramic sealing material a mullite sealing material, it becomes possible to perform sealing with even better heat resistance and oxidation resistance, and the solvent is alcohol. This has an excellent effect that the ceramics for sealing by the sol-gel method can sufficiently adhere to the surface of the SiC coating layer and the inside of the fine cracks.

Similarly, in the embodiment, by repeating contact, drying and low-temperature firing a plurality of times and then performing high-temperature firing, the process can be shortened, or contact, drying and low-temperature firing can be achieved. By repeating high-temperature baking a plurality of times, an excellent effect is obtained in that the number of steps is slightly increased, but the formation of a crack sealing layer can be further improved.

[Brief description of the drawings]

FIG. 1 is a process explanatory view showing one embodiment of the present invention.

FIG. 2 is an explanatory view showing the drying and low-temperature firing steps of FIG.

FIG. 3 is an explanatory view showing a state in which a ceramic for sealing is adhered to a SiC coating layer and a fine crack in one embodiment of the present invention, and then a low-pressure and high-temperature oxidation resistance test is performed.

FIG. 4 is a process explanatory view showing another embodiment of the present invention.

FIG. 5 is a process explanatory view in a conventional example.

FIG. 6 is an explanatory view showing the drying and low-temperature firing steps of FIG. 5;

FIG. 7 is an explanatory view showing a state in which a sealing ceramic is attached to a SiC coating layer and a fine crack in a conventional example, and then a low-temperature high-temperature oxidation resistance test is performed.

[Explanation of symbols]

 Reference Signs List 1 C / C material 2 SiC diffusion layer 3 SiC coating layer 4 Fine crack 5 Ceramic for sealing 5 a Ceramic for sealing inside fine crack 5 b Ceramic for sealing on surface of SiC coating layer 6 Mullite sealing material (ceramic sealing material) 6 a Inside fine crack Mullite sealing material 6b mullite sealing material on SiC coating layer surface

Claims (8)

(57) [Claims] 1. A C / C material having a SiC coating layer formed on the surface thereof via a SiC diffusion layer is brought into contact with a solvent containing a ceramic powder for sealing, and the ceramic powder for sealing is coated on the surface of the SiC coating layer and the SiC coating. After adhering to the inside of the fine cracks formed in the layer, drying and low-temperature baking are performed at 450 to 550 ° C. and in the air to remove the solvent and to remove the sealing ceramic by SiC.
It is fixed to the surface of the coating layer and the inside of the fine cracks, and is further subjected to high-temperature firing of 1100 to 1250 to promote crystallization of the ceramic for sealing and to increase the fixing force.
C. and C. in a non-oxidizing atmosphere to fix a ceramic sealing material on the surface of the SiC coating layer and inside the fine cracks. 2. The SiC diffusion layer and the SiC coating layer are formed by a diffusion process and a chemical vapor deposition method.
3. The surface treatment method for a C / C material according to item 1. 3. The surface treatment method for a C / C material according to claim 1, wherein vacuum impregnation is used in combination with the solvent containing the ceramic powder for sealing. 4. The method according to claim 1, wherein ultrasonic waves are applied upon contact with a solvent containing ceramic powder for sealing.
The surface treatment method for a C / C material according to any one of the above. 5. The surface treatment method for a C / C material according to claim 1, wherein the ceramic sealing material is a mullite sealing material. 6. The surface treatment method for a C / C material according to claim 1, wherein the solvent is an alcohol. 7. The method for surface treating a C / C material according to claim 1, wherein the contact, drying and low-temperature firing are repeated a plurality of times and then the high-temperature firing is performed. 8. The C / C according to claim 1, wherein the contacting, drying, low-temperature firing, and high-temperature firing are repeated a plurality of times.
Surface treatment method for materials.