JPH0769760A - Method for applying stress-removing type antioxidative coating - Google Patents

Abstract

PURPOSE:To provide a C/C structure member or heat-protecting member excellent in heat resistance, oxidation resistance, thermal shock resistance, etc., not generating cracks and peeling in a SiC coating layer are not generating oxidation, cracks, etc., also in a C/C substrate, even when exposed to a high temperature exceeding an SiC-CVD layer-forming temperature. CONSTITUTION:This method for applying the stress-removing type antioxidative coating comprises subjecting a C/C substrate 1 to a SiC-diffusing treatment to form an SiC diffusion-treated layer 2, subjecting the product to an SiC-CVD treatment to form an SiC-CVD layer 3, subjecting the product to a stress- removing calcination treatment at a using temperature or high in the atmosphere of an inert gas such as Ar or N2 to intentionally spread microcracks 5 produced by the difference between the thermal expansions of the C/C substrate 1 and the SiC or to produce new microcracks 5, and subsequently subjecting the product to a sealing treatment for filling up the microcracks 5 to form a crack sealing 4, thus reducing or eliminating the generation of a compression stress in the surface coating layer due to the difference between thermal expansions at the using temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a high-strength, heat-resistant and oxidation-resistant member such as a main structural member or an auxiliary structural member or a heat protection material which is required to have excellent strength and heat / oxidation resistance. C / C base material (carbon fiber /
Carbon composite material), particularly, oxidation / oxidation-resistant coating (SiC) of C / C base material by thermal cycle or thermal shock
C / C applied to more effectively prevent cracking or peeling of the layer) and cracking of the C / C base material.
The present invention relates to a stress relieving type oxidation resistant coating application method for a C base material.

[0002]

2. Description of the Related Art Carbon fiber / carbon composite material (C / C material) is
A lightweight material with high strength, heat resistance, and corrosion resistance that is manufactured through a C / C conversion process in which fiber-reinforced resin (FRP) is fired and carbon components are replenished to carbonize and densify it It is a material suitable for fields such as chemical equipment.

However, since this C / C material is inferior in oxidation resistance, various oxidation resistant coatings have been conventionally applied.

FIG. 6 shows an example of a conventional oxidation resistant coating technique for C / C substrates.
An SiC-diffusion treatment layer 12 and an SiC-CVD layer 13 are sequentially formed on the surface (a part or the whole surface) of the C base material 11,
Furthermore, the structure is such that crack sealing 14 is applied.

The oxidation resistant coating for the C / C substrate 11 is prepared by first adding 20 parts of fiber reinforced resin (FRP).
SiC-diffusion treatment (gas phase or solid phase) was performed at 1900 to 2000 ° C. on the C / C substrate 11 obtained by firing at 00 to 2800 ° C. and supplementing carbon components such as pitch to carbonize and densify. Phase diffusion treatment) to form a SiC-diffusion treatment layer (SiC gradient layer) 12, and then a SiC-CVD treatment at 1200 to 1300 ° C. to obtain a strong and precise SiC-CVD layer 1.
3 is formed, and the difference in thermal expansion between the C / C base material 11 and SiC (the coefficient of thermal expansion of the C / C base material is 1 × 10 ⁻⁷ , SiC
The coefficient of thermal expansion of (3) is obtained by performing crack sealing 14 by performing a sealing process for filling the microcracks 15 generated by 3 × 10 ⁻⁶ ).

Here, the SiC-diffusion layer 12 is C /
As a layer for relaxing the stress generated by the difference in thermal expansion between the C base material 11 and SiC, and an oxidation resistant layer for ensuring the oxidation resistance performance of the C / C base material 11 when the SiC-CVD layer 13 is peeled off. Function as.

Further, the SiC-CVD layer 13 functions as an oxidation resistant layer for improving the oxidation resistance performance of the C / C base material 11 whose oxidation resistance is not so good.

Further, the crack ceiling 14 is C /
The microcracks 15 generated due to the difference in thermal expansion between the C base material 11 and SiC are filled, and the temperature near the operating temperature (for example, 170
It has a function of melting at around 0 ° C.) to prevent oxygen attack, and as a sealing material, zircon-based (SiO ₂ —Z
rO ₂ type or mullite type (Al ₂ O ₃ —SiO ₂
System) etc. are used.

[0009]

However, in the C / C substrate 11 provided with such an oxidation resistant coating, the final heat treatment temperature is 1200 to 1300 ° C. at the time of the SiC-CVD treatment, and therefore the temperature is further increased. When exposed to a temperature environment of 1,200, the microcracks 15 generated by the difference in thermal expansion between the C / C substrate 11 and SiC are 1200
The SiC-CVD layer is closed when it closes at ˜1300 ° C. and further rises in temperature to cause thermal expansion to generate a compressive stress in the closed portion of the microcrack 15 and when it cannot withstand this compressive stress. 13 may be chipped or peeled off, and the crack sealing 14 may be blown off together with the SiC-CVD layer 13 chipped or peeled off.
1 is exposed, and the C / C substrate 11 itself may be cracked or peeled off, or may be consumed by oxidation.

In this case, when the rate of temperature rise to the operating temperature of 1200 to 1300 ° C. or higher (for example, 1700 ° C.) is slow, first, at a temperature of 1200 to 1300 ° C., as shown in FIG. , SiC-CVD layer 13
The microcracks 15 formed on the SiC-diffusion layer 12 are almost completely closed and the sealing material 14a of the crack sealing 14 is extruded to the surface, and the microcracks 15 formed on the SiC-diffusion layer 12 are not completely closed. In addition, when the temperature slowly rises to 1700 ° C., as shown in FIG.
The micro cracks 15 formed in 3 are completely closed. At this time, the compressive stress due to thermal expansion has a slow temperature rising rate, so the stress is removed during the temperature rising process of the SiC-CVD layer 13, so that no peeling occurs. However, the microcracks 15 rather spread due to stress relief, and the C / C substrate 11
Of the C / C base material 1 because the microcracks 15 are opened when the temperature drops from 1700 ° C. to room temperature as shown in FIG. 7C.
1 was exposed to an oxidizing atmosphere, which sometimes caused oxidative consumption.

Further, when the rate of temperature rise to the operating temperature of 1200 to 1300 ° C. or higher (for example, 1700 ° C.) is fast, first, at a temperature of 1200 to 1300 ° C., as shown in FIG.
(A), the microcracks 15 formed in the SiC-CVD layer 13 are almost closed and the sealing material 14a of the crack sealing 14 is extruded to the surface and is formed in the SiC-diffusion treated layer 12. The microcracks 15 present are not completely closed, and when the temperature rapidly rises to 1700 ° C., as shown in FIG. 8B, a rapid thermal expansion of the SiC-CVD layer 13 causes a rapid thermal expansion. The SiC-CVD layer 13 to cause large cracks or peeling or further cracks or peeling 11a of the C / C base material 11, and then 1700 ° C. to room temperature. When descending, as shown in (c) of FIG.
A part of the C / C base material 11 was consumed by oxidation, and the C / C base material 11 was sometimes cracked or peeled off to cause strength reduction or shape destruction.

Therefore, even when the SiC coating layer is exposed to a temperature higher than 1200 to 1300 ° C. which is a temperature during the SiC-CVD process, the SiC coating layer is cracked or peeled off, and the C / C base material itself is oxidized or reduced in strength, or has a shape. There has been a problem that the development of an oxidation resistant coating construction technique for C / C base materials that can prevent breakage and the like from occurring is desired.

[0013]

SUMMARY OF THE INVENTION The present invention has been conceived in view of the above-mentioned conventional problems, and is for a C / C substrate.
Even when exposed to a high temperature of, for example, 1700 ° C. that exceeds 1200 ° C. to 1300 ° C. during C-CVD treatment, defects such as cracking and peeling of the SiC coating layer do not easily occur, and oxidation of the C / C base material and Strength reduction due to cracking,
It is an object of the present invention to provide a main structural member, an auxiliary structural member, or a heat protection material having excellent heat resistance and oxidation resistance that does not cause problems such as shape destruction.

[0014]

A method for applying a stress-relief type oxidation resistant coating according to the present invention is a method of applying SiC to a C / C substrate.
-Diffusion treatment is performed to form a SiC-diffusion treated layer, then SiC-CVD treatment is performed to form a SiC-CVD layer, and then stress is applied at an operating temperature or higher and in an inert gas atmosphere. After removing and firing, C /
A microcrack caused by a difference in thermal expansion between the C substrate and SiC is intentionally spread or a new microcrack is generated, and then a sealing treatment for filling the microcrack is performed to perform crack sealing, and thermal expansion at a use temperature. It is characterized in that the generation of compressive stress in the surface coating layer due to the difference is reduced or eliminated, and in the embodiment adopted as required, N ₂ is used as an inert gas. , N ₂ gas atmosphere, a stress-relieving firing process is performed to convert the surface of the SiC-CVD layer into Si ₃ N ₄ .

FIG. 1 shows an oxidation resistant coating C / C which is obtained by carrying out the stress relieving type oxidation resistant coating method according to the present invention.
1 shows a base material, and the SiC-diffusion layer 2 and the SiC-C are provided on the surface (a part or the whole surface) of the C / C base material 1.
The VD layer 3 is sequentially formed, and the crack sealing 4 is further applied.

The oxidation-resistant coating for the C / C substrate 1 is prepared by first adding 200 parts of fiber reinforced resin (FRP).
SiC-diffusion treatment (gas phase or solid phase diffusion treatment) is applied to the C / C substrate 1 obtained by firing at 0 to 2800 ° C. and supplementing carbon components such as pitch to carbonize and densify. The SiC-diffusion treatment layer (SiC
Gradient layer 2 is formed, and then SiC-CVD treatment is performed at 1200 to 1300 ° C. to form a strong and dense SiC-CVD layer 3 and further at a working temperature (for example, 1700 ° C.) or The stress-relieving firing treatment is performed at the above temperature and in an inert gas atmosphere to obtain C /
After the microcracks 5 caused by the difference in thermal expansion between the C base material 1 and SiC are intentionally spread or new microcracks are generated, a crack sealing 4 for filling the microcracks 5 with a sealing material is applied, and the operating temperature is increased. The generation of compressive stress in the surface coating layer due to the difference in thermal expansion between the C / C substrate 11 and SiC at (for example, 1700 ° C.) is reduced or eliminated.

Here, the SiC-diffusion layer 2 is C / C.
An oxidation resistant layer for relieving the stress generated by the difference in thermal expansion between the base material 1 and SiC, and for ensuring the oxidation resistance of the C / C base material 1 when the SiC-CVD layer 13 is peeled off. Function as.

This SiC-diffusion process is performed in the range of 1900 to 20.
By reacting the C / C substrate 1 with silicon monoxide at a temperature of 00 ° C. as shown in the following formula, carbonization which is excellent in heat resistance, abrasion resistance, thermal shock resistance, peeling resistance and chemically stable is achieved. A diffusion layer is formed of silicon.

2C + SiO = SiC + CO

In addition to this, for example, 1050 to 12
H ₂ and SiCl were formed on the surface of the C / C substrate 1 heated to 50 ° C.
CV, in which a mixed gas of ₄ and ₄ was caused to flow, SiCl ₄ was reduced by H _2, and Si was deposited on the surface of the C / C substrate 1.
A coating layer of Si is formed by the D method, and then heat treatment is performed near the melting temperature of Si (1400 to 1450 ° C.) to react Si with the C / C base material 1 to form a SiC diffusion layer of SiC-. The diffusion treatment layer 2 can also be formed.

Further, the SiC-CVD layer 3 functions as an oxidation resistant layer for improving the oxidation resistance performance of the C / C substrate 1 whose oxidation resistance is not so good.

When forming the SiC-CVD layer 3, a metal halide is used to form SiCl ₄ (g) + CxHy (g) + H ₂ (g) → Si.
It is possible to form the SiC-CVD layer 3 on the surface of the SiC-diffusion layer 2 by performing the CVD process by the reaction of C (s) + HCl (g) + [C, H] (g). .

Further, by utilizing the thermal decomposition on the surface of the heated substrate, CH ₃ SiCl ₃ (g) → SiC (s) + 3HCl
By the decomposition of (g), SiC-C is formed on the surface of the SiC-diffusion treated layer 2.
It is also possible to form the VD layer 3.

In this way, after the SiC-CVD layer 3 is formed on the surface of the SiC-diffusion treated layer 2, stress is applied at an operating temperature (for example, 1700 ° C.) or higher and in an inert gas atmosphere. After removing and firing, C
/ C base material 1 and micro cracks 5 caused by the difference in thermal expansion between SiC are intentionally spread or new micro cracks are generated. In this case, the temperature rising rate up to the use temperature is C / C base material 1 The temperature rising pattern is set so that thermal shock is not applied to, for example, as shown in FIG.
It is desirable to heat at a temperature rising rate of not more than ° C / Hr.

Regarding the holding time in such a stress relieving firing process, the above-mentioned effect occurs once the temperature is raised or lowered, so basically it is not necessary to give the holding time, but C / C In some cases, it is desirable to hold the substrate for about 30 to 60 minutes in consideration of the temperature distribution of the entire substrate.

Further, it is desirable that the temperature lowering rate after the firing treatment be about 100 ° C./Hr or less by, for example, furnace cooling.

After the microcracks 5 are intentionally spread or new microcracks are formed in this way, the microcracks 5 are melted near the operating temperature to fill the microcracks 5 and a sealing treatment is performed to prevent oxygen attack. Then, the crack sealing 4 is applied to the surface and the microcracks 5.

At this time, as the sealing material, zircon type (SiO ₂ —ZrO ₂ type) or mullite type (A)
1 ₂ O ₃ —SiO ₂ system) and the like are used.

By using argon as the inert gas atmosphere, the SiC-CVD layer 3 is formed below the crack sealing 4,
This SiC has a decomposition melting point of 2830 ± 40 ° C. and is 200
Sublimation begins to decompose at 0 ° C, sublimates at 2200 ° C, 900 ° C
SiO ₂ is formed in the oxidizing atmosphere from the vicinity, and excellent oxidation resistance performance is exhibited from 900 ° C. to 1700 ° C.

On the other hand, when nitrogen gas is used as an atmosphere gas in the stress relieving firing process, SiC--
The surface of the CVD layer 3 becomes Si ₃ N ₄ .

As described above, by using nitrogen as the inert gas atmosphere, the SiC-CVD layer 3 whose surface is converted to Si ₃ N ₄ is formed in the lower layer of the crack sealing 4, and this Si ₃ N is formed. No. ₄ decomposes at 1900 ° C., forms SiO ₂ in an oxidizing atmosphere at a decomposition temperature or lower, and exhibits sufficient oxidation resistance.

In this way, in the heat / oxidation-resistant main structural member or auxiliary structural member or thermal protective material, etc., in which the stress-relieving type oxidation resistant coating is applied to the C / C base material 1, for example, As shown in (a) of FIG.
In an environment of about 1300 ° C., the microcracks 5 intentionally expanded by the stress relieving firing process and provided with the crack sealing 4 are completely closed in both the SiC-CVD layer 3 and the SiC-diffusion treated layer 2. The sealing material 4a is pushed out slightly upward.

Then, when the temperature further rises and reaches, for example, about 1700 ° C. as shown in FIG. 2B, the SiC coating layers (2, 3) further expand, but at this time as well. Micro crack 5 is SiC-CV
Neither the D layer 3 nor the SiC-diffusion treated layer 2 is completely closed, so that the compressive stress is not generated or reduced, and the SiC coating layers (2, 3) do not peel. Will be things.

Further, even when the temperature is lowered from 1700 ° C. to room temperature, as shown in FIG. 2C, the crack sealing 4 is formed on the surface, so that C
The / C base material 1 is not oxidized.

[0035]

In the method for applying a stress-relieving type oxidation resistant coating to the C / C substrate 1 according to the present invention, as shown in FIG. 4, first, in the step (a) of FIG. 1 is prepared, and then in step (b) of FIG.
SiC-diffusion treatment at 900-2000 ° C
-Diffusion treatment layer 2 is formed (at this time, C / C base material 1 is thermally expanded.) Then, when the temperature is returned to room temperature in step (c) of FIG. 4, C / C base material 1 and SiC The micro-cracks 5 are generated in the SiC-diffusion treated layer 2 due to the difference in thermal expansion from the above, and then in the step (d) of FIG.
Perform SiC-CVD processing at 300 ° C to obtain SiC-CVD
A layer 3 is formed (at this time, the microcracks 5 of the CVD-diffusion treated layer 2 become smaller again, but they do not close). Then, in the step (e) of FIG. When returned, microcracks 5 are also generated in the SiC-CVD layer 3 due to the difference in thermal expansion between the C / C substrate 1 and SiC.

Next, in the step (f) of FIG. 4, a stress relieving firing process is performed at an operating temperature (for example, 1700 ° C.) and in an inert gas atmosphere to perform thermal expansion of the C / C substrate 1 and SiC. The microcracks 5 caused by the difference are intentionally destroyed by thermal expansion of SiC to spread the microcracks 5 or generate new microcracks 5 when the microcracks 5 are returned to room temperature, and then the step (g) in FIG. In the above, since the oxidation resistant coating is finished by applying crack sealing 4 by performing crack sealing treatment, even when used at a temperature of 1300 to 1700 ° C., as shown in (h) of FIG.
The microcracks 5 will not be completely closed, and therefore the SiC coating layer (2, 3) will not or will not have the compressive stress as if the microcracks 5 were completely closed,
The peeling does not occur in the SiC coating layers (2, 3), and the reduction in oxidation resistance due to the exposure of the C / C base material 1 is prevented.

On the other hand, in the conventional oxidation resistant coating method for the C / C base material 11, as shown in FIG. 5, first, in the step (a) of FIG.
1 is prepared, and then, in step (b) of FIG.
SiC diffusion treatment is performed at 00 to 2000 ° C. to form a SiC-diffusion treatment layer 12 (at this time, the C / C base material 1 is thermally expanded), and then at room temperature in step (c) of FIG. Returning to 1, the microcracks 15 are generated in the SiC-diffusion treated layer 12 due to the difference in thermal expansion between the C / C base material 1 and SiC, and then, in step (d) of FIG.
Perform SiC-CVD treatment at 1300 ° C to obtain SiC-CV
D layer 13 is formed (at this time, CVD-diffusion treatment layer 12
The microcracks 15 of No. 1 become smaller again, but do not close. ) Then, when the C / C substrate 11 is returned to room temperature in the step (e) of FIG. 5, microcracks 15 are also generated in the SiC-CVD layer 13 due to the difference in thermal expansion between the C / C substrate 11 and SiC. .

Next, in the step (f) of FIG. 5, the surface and the microcracks 15 are subjected to the crack sealing 14 by the sealing treatment to finish the oxidation resistant coating. Thus, when used at a temperature of 1300 to 1700 ° C., the micro cracks 15 of the SiC-CVD layer 13
Completely closes, and the temperature rises, and SiC-CVD
Due to the thermal expansion of the layer 13, compressive stress concentrates in the closed portion of the microcracks 15 and SiC-C
The VD layer 13 is chipped or peeled off, and the SiC-CVD layer 1
3, the crack sealing 14 was blown off, and the C / C base material 11 might be consumed by oxidation as shown in (h) of FIG.

[0039]

[Examples] C / C base material obtained by firing a fiber reinforced resin (FRP; carbon fiber used as fiber, epoxy resin used as resin) and supplementing carbon components such as pitch to carbonize and densify 1 was brought into contact with silicon monoxide (SiO) at 1900 ° C. to form a SiC-diffusion treated layer 2 on the surface thereof, and then a CVD treatment using a metal halide (SiCl ₄ ) was performed.
The SiC-CVD layer 3 was formed on the surface of the diffusion treatment layer 2.

Then, as shown in FIG. 3, the temperature is raised to the operating temperature (here, 1700 ° C.) in Ar inert gas at a heating rate of 600 ° C./Hr or less, and then,
Hold for 30 to 60 minutes, then 100 ° C /
A stress relief treatment of cooling at a cooling rate of Hr or less was performed.

Next, a mullite type (Al ₂ O ₃ --SiO ₂
By sealing process using a _{two-component} system) sealant, by filling a sealant into microcracks 5 is performed with the crack sealing 4 on the surface of the SiC-CVD layer 3, stress relief according to the invention embodiment A test material having a mold oxidation resistant coating was obtained.

On the other hand, for comparison, the oxidation resistant coating according to the conventional example in which the crack sealing 14 is applied to the surface of the SiC-CVD layer 13 and the microcracks 15 are filled with the sealing material without performing the stress relieving firing process, is made. The tested material was obtained.

Next, a thermal cycle test (1700 ° C. × 1100 seconds × 10 cycles (normal temperature → 17
00 ° C; 5 to 6 seconds, 1700 ° C → 200 ° C: 10 minutes) to perform a heat cycle test) to determine the weight reduction rate and C / C.
Substrate (1,11) and coating layer (2,3,1)
When the presence or absence of peeling of (2, 13) was examined, the results shown in Table 1 were obtained.

[0044]

[Table 1]

As shown in Table 1, in the invention examples 1 and 2 in which the stress relieving type oxidation resistant coating was applied, the initial weight loss rate was small, and even if the weight loss rate increased as the number of cycles increased, C The peeling of the / C substrate 1 and the SiC coating layer (2, 3) did not occur.

On the other hand, in the comparative example in which the conventional oxidation resistant coating was applied, the initial weight loss rate was high and
Peeling was observed on the C / C substrate 11 and the SiC coating layers (12, 13) as early as the cycle.

[0047]

EFFECTS OF THE INVENTION In the method for applying a stress-relieving type oxidation resistant coating to a C / C substrate according to the present invention, a C-C substrate is subjected to a SiC-diffusion treatment to form a SiC-diffusion treated layer, and then a SiC- A CVD treatment is performed to form a SiC-CVD layer, and then a stress relief firing treatment is performed at an operating temperature or higher and in an inert gas atmosphere to perform a thermal expansion difference between the C / C substrate and SiC. By intentionally expanding the microcrack caused by or to generate a new microcrack, and then perform a sealing treatment to fill the microcrack to perform crack sealing, compressive stress of the surface coating layer due to the thermal expansion difference at the use temperature. Since the structure is designed to reduce or eliminate the occurrence, C /
For example, 1200 at the time of the SiC-CVD process for the C base material.
Even when exposed to a high temperature exceeding 1300 ° C., for example, about 1700 ° C., the compressive stress due to the difference in thermal expansion does not decrease or does not occur in the SiC coating layer.
Main structural member made of C / C material, which is excellent in heat resistance / oxidation resistance and thermal shock resistance, which does not easily cause defects such as cracking or peeling of the C coating layer and does not cause oxidation or cracking of the C / C base material. Alternatively, a remarkably excellent effect that the auxiliary structural member or the heat protection material can be obtained is brought about.

[Brief description of drawings]

FIG. 1 shows a model structure ((a) of FIG. 1) and a sectional structure (FIG. 1) of a C / C substrate and an oxidation resistant coating layer showing an embodiment of a stress relieving type oxidation resistant coating according to the present invention.
It is an explanatory view showing (b) of.

FIG. 2 shows the C / C base material subjected to the stress relieving type oxidation resistant coating shown in FIG. 1 at 1300 ° C. (FIG. 2 (a)), 1700 ° C. (FIG. 2 (b)) and 1700 ° C.
It is explanatory drawing which shows the change of sectional structure at the time of falling from (degree C) to normal temperature ((c) of FIG. 2).

FIG. 3 is a graph showing a time-temperature pattern during the stress relieving firing process.

FIG. 4 shows a cross-sectional structure of a C / C substrate on which a stress relieving type oxidation-resistant coating according to the present invention is applied, from the initial stage of the oxidation-resistant coating to the time of being exposed to a temperature of 1300 ° C. or higher after the oxidation-resistant coating. It is explanatory drawing which shows a change sequentially with action.

FIG. 5 shows the changes in the cross-sectional structure of the conventional C / C substrate coated with an oxidation-resistant coating from the initial stage of the oxidation-resistant coating to the time of being exposed to a temperature of 1300 ° C. or higher after the oxidation-resistant coating, together with the action. It is an explanatory view shown.

FIG. 6 shows C / C which has been subjected to an oxidation resistant coating according to a conventional example.
Model structure of C substrate and oxidation resistant coating layer (Fig. 6)
(A)) and a cross-sectional structure ((b) of FIG. 6).

FIG. 7: C / C coated with an oxidation resistant coating as shown in FIG.
1300 ° C when the temperature rising rate is slow in the substrate
FIG. 8A is an explanatory diagram showing changes in the cross-sectional structure at (700 a in FIG. 7), 1700 ° C. ((b) in FIG. 7) and when the temperature drops from 1700 ° C. to room temperature ((c) in FIG. 7).

FIG. 8 is a C / C coated with an oxidation resistant coating shown in FIG.
1300 ° C when the temperature rising rate is high in the substrate
It is explanatory drawing which shows the change of sectional structure at the time ((a) of FIG. 8), 1700 degreeC ((b) of FIG. 8), and when it falls to normal temperature from 1700 degreeC ((c) of FIG. 8).

[Explanation of symbols]

 1 C / C base material 2 SiC-diffusion treatment layer 3 SiC-CVD layer 4 Crack sealing 5 Micro crack

Claims (2)

[Claims] 1. A C / C substrate is subjected to a SiC-diffusion treatment to form a SiC-diffusion treatment layer, and then subjected to a SiC-CVD treatment to form a SiC-CVD layer, and then at a working temperature or higher. The stress-relieving firing treatment is performed at a temperature of 10 ° C. and in an inert gas atmosphere to intentionally widen or generate new micro-cracks caused by a difference in thermal expansion between the C / C base material and SiC, and thereafter, A stress relieving type oxidation resistant coating application method for C / C base material, which comprises performing sealing treatment for filling micro cracks to perform crack sealing. 2. A using N ₂ as an inert gas, N ₂
SiC-CV by performing stress relief firing in a gas atmosphere
The stress relieving type oxidation resistant coating application method for a C / C substrate according to claim 1, wherein the surface of the D layer is converted to Si ₃ N ₄ .