JPH08253861A - C/c composite material having high oxidation resistance - Google Patents

Abstract

PURPOSE: To provide a C/C composite material coated with an oxidation resistant coating film, which is improved in adhesiveness of the C/C composite material to a ceramic coating film and has high strength. CONSTITUTION: Oxidation resistance is imparted to the C/C composite material by forming a thermally decomposed carbon 3 with about 30μm film thickness on the surface of a C/C layer 2 by a CVD method, next applying molybdenum 4 with 10μm thickness as a high m.p. metal by sputtering, applying silicon carbide 5 with 100μm thickness by CVD method and providing a vitreous coating film layer 6 thereon.

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 (hereinafter referred to as C / C) composite material which has a high oxidation resistance and can be used for a long time in a high temperature atmosphere.

[0002]

2. Description of the Related Art A C / C composite material is a composite material in which carbon fiber is used as a reinforcing material and carbon is used as a matrix, and is excellent in heat resistance, chemical resistance, and abrasion resistance, and has high strength and light weight. Is. Therefore, it is used for rocket nozzles and aircraft disc brakes. However, C / C
The composite material is oxidized in an oxygen atmosphere from about 500 ° C, and its excellent physical and chemical performance deteriorates, so use in a high temperature atmosphere is impossible except for an extremely short time. there were. In order to prevent this phenomenon, various studies have hitherto been made on a method of enhancing the oxidation resistance performance of the carbon material. Among these methods, the coating of ceramics by the chemical vapor deposition method (hereinafter referred to as CVD) is one of the most commonly used methods, and it is possible to obtain a dense coating film by this method. it can. However, in this method, the C / C composite material as the base material is not
In many cases, it was necessary to heat up to a temperature of around 00 ° C., and when cooling to room temperature after completion of the coating treatment, the ceramic coating on the surface was often peeled off or cracked. This is mainly due to the large difference in the coefficient of thermal expansion between the C / C composite material and the ceramics. The thermal expansion coefficient of the C / C composite material is determined by the thermal expansion coefficient of the carbon fiber itself, and there is no ceramic coating material having the same thermal expansion coefficient as the C / C composite material. It was difficult to use a ceramic coating film.

In Japanese Examined Patent Publication No. 2-54778, before coating the ceramic layer by the CVD method, the surface layer of the C / C composite material is converted to SiC by reacting metallic silicon with the C / C composite material by the pack diffusion method. It describes a method of increasing the adhesion to a CVD-SiC layer by providing a conversion coating of SiC. Although this method is excellent in improving the adhesion, there is a problem that the material strength of the C / C composite material is reduced because a part of the reinforcing fibers in the surface layer of the C / C composite material is converted to SiC. It was

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above problems in the prior art, to provide excellent adhesion between the C / C composite material and the ceramic coating film, and to provide a high strength, which is resistant to oxidation. The purpose is to provide a coated C / C composite material.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the present inventors have made a difference in the coefficient of thermal expansion between the plane direction and the thickness direction of a C / C composite material and the C / C composite material. As a result of intensive studies focusing on the difference in the coefficient of thermal expansion between ceramics and ceramics, it was concluded that the difference in the coefficient of thermal expansion between the two can be alleviated by pyrolytic carbon and a metal layer that plastically deforms at high temperatures. .

That is, according to the present invention, the surface of the C / C composite material is coated with pyrolytic carbon, and B, Cr, Ir, M are further coated thereon.
O, Nb, Pt, Ti, V and W, at least one kind of metal having a high melting point is coated, and further, a ceramic such as silicon carbide or silicon nitride is coated on the oxidation resistant C. / C composite material and its oxidation resistance C /
It is intended to provide a C / C composite material in which a C composite material is further coated with a glass-like substance.

In the C / C composite material of the present invention, the difference in the thermal expansion coefficient between the plane direction and the thickness direction is alleviated by the pyrolytic carbon, and the difference in the thermal expansion coefficient is caused by the metal layer which is plastically deformed at a high temperature. In order to relieve the generated stress, the ceramics such as silicon carbide or silicon nitride coated on the outer layer have excellent adhesiveness and the C / C composite material has excellent adhesiveness at the interface even when subjected to cycle heating between room temperature and 1000 ° C. Hardly decreases.

[0008]

The present invention will be described below in more detail. C / C
As the reinforcing carbon fiber of the composite material, PAN-based, rayon-based or tar-pitch-based carbon fiber can be used, and the most excellent one is obtained by using PAN-based one in terms of strength. For example, Toho Rayon's "High Strength Bethfight (HT
A) ”,“ high-elasticity vesphite (HM40) ”, etc. which are generally commercially available can be used. The form of the reinforcing fiber is 100 to 12000 long filaments.
It is possible to use a bundle of rovings aligned in one direction and / or a woven fabric. As the binder, a thermosetting substance such as phenol resin or furan resin, or a thermoplastic substance such as pitch can be used.

As a method for producing a C / C composite material, for example, a prepreg sheet is made by impregnating and applying carbon fiber with a bander, laminated, heated and pressed into a molded body, and the molded body is filled with nitrogen, argon or the like. After firing in an inert atmosphere, graphitization is further performed as required to obtain a C / C composite material. Then, depending on the required performance, densification is repeated by an impregnation method in which a thermosetting substance or a plastic substance is impregnated and baked, or a CVI method in which a hydrocarbon gas such as methane or propane is thermally decomposed to obtain carbon, A method of increasing the density and the strength of the C / C composite material can be mentioned.

A layer of pyrolytic carbon is produced on the surface of the C / C composite material obtained as described above. Pyrolytic carbon is obtained by a CVD method that thermally decomposes a hydrocarbon gas such as methane or propane. The crystal structure of pyrolytic carbon changes depending on the treatment conditions, but isotropic pyrolytic carbon works most effectively in the present invention. Anisotropic pyrolytic carbon easily causes cracks in the layer direction during heating and cooling. The temperature for depositing pyrolytic carbon is 15 because the temperature at which the C / C composite material is used is approximately 1500 ° C. or higher.
It is preferably 00 ° C. or higher. Pyrolytic carbon deposited at a temperature lower than the use temperature causes a structural change during use and causes a decrease in adhesion between the C / C composite material and the ceramic layer. The film thickness of isotropic pyrolytic carbon is 1μ.
The range of m or more and 100 μm or less is preferable, and if it is less than the range, the effect as a relaxation layer is low and cracks in the ceramic layer
Peeling is likely to occur. If the film thickness exceeds the above range, the pyrolytic carbon is likely to be peeled off.

Next, B, Cr, Ir, Mo, Nb, P
At least one metal selected from t, Ti, V and W is coated. The reason why the metal is selected is that it has a high melting point. When the melting point is 1500 ° C or lower, usually C /
It cannot be used because the C composite material is completely melted at a temperature of 1500 ° C. or higher and the outermost ceramic layers such as silicon carbide and silicon nitride are peeled off.
It should be noted that Hf and Zr, which have a problem in peeling resistance even if the metal has a melting point of 1500 ° C. or higher, are excluded. As a method for coating a metal, a method usually used for metal coating such as a CVD method or a sputtering method can be used. The film thickness of the refractory metal is preferably 1 μm or more, and if it is less than 1 μm, the effect of relaxing the thermal stress becomes poor, and the outermost ceramic layer peels off.

A ceramic layer of silicon carbide or silicon nitride is formed on the coating layer of refractory metal. In particular, these are selected because of their high temperature stability, low vapor pressure at high temperature, low reactivity with carbon, and low oxygen permeability. The CVD method is suitable as a method for coating these ceramic layers, and the densest layer can be obtained. The thickness of the ceramic layer is preferably 5 μm to 200 μm. If it is less than 5 μm, the oxidation resistance in an oxidizing atmosphere is deteriorated. More preferably, when it is 30 μm or more, the oxidation resistance performance is further improved. On the other hand, if the thickness exceeds 200 μm, peeling is likely to occur due to repeated heating due to the difference in thermal expansion coefficient from the C / C composite material. It is more preferably 150 μm or less.

Defects such as fine cracks are likely to occur in the coated ceramic layer during cooling. Oxygen that has entered through this defect will start oxidation of the C / C composite at about 50
In the temperature range from 0 ° C. to a thousand and several hundreds of degrees Celsius where fine cracks in the ceramic layer are closed by thermal expansion, significant oxidation is caused. Therefore, for example, an insulator material containing oxygen oxide, silicon oxide, aluminum oxide, zirconium oxide as a main component is applied. 50% of these insulators
The crack closes because it melts at a temperature near 0 ° C. where oxidation of the C / C composite material starts and seals the crack, and when the fine crack of the ceramic layer starts to close due to thermal expansion, it has fluidity. At the same time, it can easily deform and flow, and keeps sealing cracks. As a method for coating the glassy material, for example, triethyl borate, tetraethyl silicate, a method of applying a solution which is made into an insulator by a reaction of aluminum phosphate, an aluminum-alkoxide, an organic compound which precipitates an oxide by a reaction of zirconium-alkoxide, etc. The method of applying the solution of can be mentioned.

[0014]

EXAMPLE FIG. 1 is a schematic partial sectional view of a C / C composite material of an example. The C / C composite material 1 of the example is C / C.
A layer of pyrolytic carbon 3 is formed on layer 2 and has a layer of silicon carbide or silicon nitride 5 with refractory metal 4 interposed. Further, a glassy coating layer 6 is formed on the uppermost surface.

The present invention will be specifically described below based on Examples and Comparative Examples. Example 1 A film of about 30 μm of pyrolytic carbon was formed on the surface of a C / C composite material by a CVD method in which propane was introduced into a furnace heated to about 1600 ° C. with argon as a carrier gas at a partial pressure of 1%. Formed thick. Then, molybdenum was coated to a thickness of 10 μm by a sputtering method. Thereafter, a mixed gas of carbon tetrachloride, methane, hydrogen and argon was added to about 1100.
The C / C composite material was coated with 100 μm of silicon carbide by the CVD method introduced into the furnace heated to 0 ° C. to impart oxidation resistance to the C / C composite material. The C / C composite material was inserted into a furnace heated to 1400 ° C. in an air atmosphere, held for 6 minutes, taken out, and then rapidly cooled. An oxidation test was conducted. The silicon carbide coating film was repeatedly heated and cooled 30 times. No peeling was observed, C / C
The weight loss due to oxidation of the composite material was 0.8%.

Example 2 Oxidation resistance was imparted to a C / C composite material in exactly the same manner as in Example 1 except that the refractory metal was changed to titanium 15 μm. When the C / C composite material was subjected to an oxidation test in the same manner as in Example 1, no peeling of the silicon carbide coating was observed and the weight loss was 0.9%.

Example 3 The refractory metal of Example 1 was changed to boron 20 μm and the silicon carbide coating was changed to silicon nitride 150 μm to impart oxidation resistance to the C / C composite material. This C
An oxidation test was conducted on the C / C composite material in the same manner as in Example 1. As a result, no peeling of the silicon carbide coating film was observed and the weight loss was 0.
It was 6%.

Example 4 A solution of tetraethyl silicate polymerized by polymerization reaction in advance under an acid catalyst was applied to the C / C composite material having the oxidation resistance of Example 1 and then 5
After drying at 00 ° C for 30 minutes, the glass was once melted by heating to 1000 ° C, and the surface of the C / C composite material was coated with glass. When this C / C composite material was subjected to an oxidation test in the same manner as in Example 1, no peeling of the silicon carbide coating was observed, and the weight loss due to oxidation of the C / C composite material caused by peeling was 0.5%, which is favorable. It was performance.

Example 5 A C / C composite material in which the refractory metal of Example 4 was changed to 7 μm of chromium and coated with glass was subjected to an oxidation test in the same manner as in Example 1, and the silicon carbide coating was peeled off. Was not observed, and the weight loss was 0.5%. [Embodiment 6] The refractory metal of Embodiment 1 is replaced with Nb having a thickness of 5 μm.
The oxidation resistance was imparted to the C / C composite material in exactly the same manner except that it was changed to. When the C / C composite material was subjected to an oxidation test in the same manner as in Example 1, no peeling of the silicon carbide coating film was observed and the weight loss was 1.1%.

[Embodiment 7] The C / C composite material was provided with oxidation resistance in the same manner except that the refractory metal of Example 1 was changed to Pt having a thickness of 5 μm. When the C / C composite material was subjected to an oxidation test in the same manner as in Example 1, no peeling of the silicon carbide coating was observed and the weight loss was 1.0%.

[Embodiment 8] The C / C composite material was provided with oxidation resistance in exactly the same manner as in Embodiment 1 except that the refractory metal was changed to V having a thickness of 10 μm. When this C / C composite material was subjected to an oxidation test in the same manner as in Example 1, no peeling of the silicon carbide coating film was observed and the weight loss was 0.9%.

[Example 9] The C / C composite material was provided with oxidation resistance in exactly the same manner as in Example 1 except that the refractory metal was changed to W having a thickness of 3 µm. When this C / C composite material was subjected to an oxidation test in the same manner as in Example 1, no peeling of the silicon carbide coating film was observed and the weight loss was 1.1%.

[Embodiment 10] Oxidation resistance was imparted to a C / C composite material in exactly the same manner as in Embodiment 1 except that the refractory metal was changed to Ir having a thickness of 5 μm. When this C / C composite material was subjected to an oxidation test in the same manner as in Example 1, no peeling of the silicon carbide coating film was observed and the weight loss was 1.0%.

Comparative Example 1 A C / C composite material was coated with silicon carbide to a thickness of 100 μm by the method shown in Example 1.
When this material was subjected to an oxidation test in the same manner as in Example 1, the silicon carbide coating film was peeled off during the first heating and cooling. [Comparative Example 2] The C / C composite material was coated with silicon nitride to a thickness of 150 µm by the method described in Example 1. When this material was subjected to an oxidation test in the same manner as in Example 1, the silicon nitride film was peeled off during the first heating and cooling.

[Comparative Example 3] A coating of silicon carbide was performed by the CVD method in exactly the same manner as in Example 1 except that the coating of the refractory metal was not carried out. It was not possible to make a proper film. [Comparative Example 4] Silicon carbide was coated in a thickness of 100 µm in the same manner as in Example 1 except that the pyrolytic carbon was not coated. When this material was subjected to an oxidation test in the same manner as in Example 1, peeling of the silicon carbide coating was observed and the weight loss was 1.5%.

Comparative Example 5 An oxidation test was conducted on a C / C composite material produced in exactly the same manner as in Example 1 except that the refractory metal of Example 1 was changed to Zr having a thickness of 3 μm. ,
The silicon carbide coating was peeled off. [Comparative Example 6] The refractory metal of Example 1 was added to Hf having a thickness of 7 μm.
The C / C composite material manufactured in exactly the same manner except that the above was subjected to the same oxidation test as in Example 1, but the silicon carbide coating film was peeled off.

[0027]

Since the present invention is constructed as described above, the C / C composite material of the present invention has high oxidation resistance and can be used as a heat resistant member of a space shuttle.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a C / C composite material of an example.

[Explanation of symbols]

1 C / C composite material 2 C / C layer 3 Pyrolytic carbon 4 Refractory metal 5 Silicon carbide or silicon nitride 6 Vitreous coating layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location // D06M 101: 40 (72) Inventor Tomoyuki Tahara 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made by Kawasaki Iron Technology Co., Ltd. (72) Inventor Noriyoshi Fukuda 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Kawasaki Steel (72) Inventor Tomoyuki Uruno 1 Kawasaki-cho, Chuo-ku, Chiba Prefecture Kawasaki Iron Co., Ltd. Chiba Steel Works (72) Inventor Zhu Jianping No. 1 Daegu Road, Tainan City, Taiwan National Succeeding University of Technology, Materials Engineering

Claims (3)

[Claims] 1. A C having a high oxidation resistance characterized by having a pyrolytic carbon coating layer on the surface thereof, a refractory metal coating layer thereon, and a silicon carbide or silicon nitride coating layer thereon. / C composite material. 2. The refractory metal is B, Cr, Ir, M
The C / C composite material according to claim 1, which has a high oxidation resistance, characterized by being at least one kind of metal selected from the group consisting of o, Nb, Pt, Ti, V and W. 3. A high oxidation resistance performance according to claim 1, further comprising an insulator coating layer made of at least one kind of oxide of silicon, aluminum and zirconium on the silicon carbide or silicon nitride. C / C composite material.