JPH11314985A - Heat resistant/oxidation resistant carbon fiber reinforced carbon material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat-resistant/oxidation-resistant material having excellent durability by successively forming a silicon carbide layer by silicon diffusion, a dense silicon carbide-coated layer, and a metal silicate layer on the surface of a base body comprising a carbon fiber reinforced carbon composite material. SOLUTION: On the surface of a C/C base body 1 comprising a carbon fiber reinforced carbon composite material, a porous silicon carbide layer (SiC layer) 2 as a thermal stress relaxing layer is formed by diffusing silicon by diffusing method. Then a dense silicon carbide layer (SiC layer) 3 is formed by chemical vapor phase vapor deposition on the silicon carbide layer 2, and further metal silicide 4 or a mixture 5 of metal silicide and metal boride is applied on the surface of the silicon carbide layer 3. The metal elements which constitute the metal silicide and metal boride are preferably selected from Mo, Zr and W, and the mixing ratio of the metal silicide to metal boride is preferably about 10:1 to 1:10. The porous silicon carbide layer 2 and dense silicon carbide layer 3 are formed preferably to have about 10 to 200 μm and about 100 to 300 μm thickness, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant and oxidation-resistant carbon fiber reinforced carbon material, and more particularly, to a structure material for a space plane, a turbine blade, a member for a nuclear reactor, and the like, which can withstand repeated use in a high-temperature oxidizing atmosphere. It relates to a carbon material as a material.

[0002]

2. Description of the Related Art Generally, carbon materials are oxidized in an oxidizing atmosphere from about 500 ° C., and their excellent physical and chemical properties are deteriorated. It was not possible unless. In order to prevent this phenomenon, various studies have been made on the oxidation-resistant treatment of carbon materials.

[0003] Among these methods, a chemical vapor deposition method (C
Ceramic coating on a carbon material by the VD method is one of the most common methods, and a dense film can be obtained by this method. According to this method, SiC, TiC,
Carbides such as HfC and TaC, Si ₃ N ₄ , TiN, B
Nitride such as N and ZrN, oxide such as Al ₂ O ₃ and ZrO ₂ , and other borides can be coated.

Generally, in this method, the deposition temperature is 1000 ° C.
Since it is before and after, the ceramic coating on the surface often peels off or cracks occur when the substrate is cooled. This is because the difference in thermal expansion coefficient between the substrate and the ceramic to be deposited is large, and can be solved by making the expansion coefficient of the substrate approximately equal to that of the ceramic to be deposited.

Therefore, in order to improve the adhesion between the substrate and the ceramic, a method has been adopted in which the surface of the substrate is converted into ceramics by a diffusion method and then coated by a chemical vapor deposition method (CVD method).

[0006] Among the CVD coated ceramics, silicon carbide and silicon nitride are widely used as heat and oxidation resistant coatings of carbon fiber reinforced carbon materials because of their excellent heat and oxidation resistance. 1 to 4 at a high temperature of 1400 to 1700 ° C, such as cones and leading edges
When exposed under a reduced pressure environment of 000 Pa, silicon carbide;
Silicon nitride becomes SiO gas due to active oxidation and is severely consumed.

As a method for preventing active oxidation, a method has conventionally been developed in which a compound or metal containing no silicon is coated as an intermediate layer on a silicon carbide film, and an outermost layer is coated with an oxide. No., JP-A-4-285
No. 068, HfC, TaC, ZrC, W
₂ C, NbC, ThC, ZrB, HfB ₂ , BN, Hf
N, ZrN, AlN, Pt, Ir, Os, Rh, Ru,
ThO, ZrO ₂ , HfO ₂ , L
A method of coating a ₂ O ₃ and Y ₂ O ₃ and a method of coating an outermost layer with an oxide SiO ₂ glass are disclosed.

However, these include oxidation of the coating layer and SiO ₂
The life time is short due to the reaction between the base glass and silicon carbide,
Lack of practicality. A metal coating has also been developed as an active antioxidant film. However, when a single metal such as metal silicon is used, the durability is not so high because the corrosion resistance of silicon carbide and the oxidation resistance of the coated metal silicon itself are poor. Absent. Moreover, since metallic silicon has a melting point of about 1400 ° C., it has the drawback that it melts during use in a spacecraft and moves when it is flowed by air.

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention relates to a method of forming a silicon carbide layer, which is an oxidation-resistant barrier of carbon fiber reinforced carbon material, on the basis of the ac content.
Heat resistance with excellent durability that can prevent tive oxidation
An object of the present invention is to provide an oxidation-resistant carbon fiber reinforced carbon material.

[0010]

The heat- and oxidation-resistant carbon fiber-reinforced carbon material of the present invention for solving the above-mentioned problems is characterized in that the surface of a carbon fiber-reinforced carbon composite material as a base material is porous by diffusion of silicon. Silicon carbide layer, a dense silicon carbide coating layer is formed on the silicon carbide layer, and a metal silicide or a mixture of a metal silicide and a metal boride is formed on the surface of the silicon carbide coating layer. Is coated.

In the above heat-resistant and oxidation-resistant carbon fiber reinforced carbon material of the present invention, the dense silicon carbide coating layer is formed by a chemical vapor deposition method or a silicon carbide powder in an organic silicon resin. It is preferable that the dispersion is formed by applying a heat treatment after application to convert the organic silicon resin into silicon carbide.

In the above heat-resistant and oxidation-resistant carbon fiber reinforced carbon material of the present invention, the metal element constituting the metal silicide is:
Preferably, it is selected from Mo, Zr, and W.

In the heat-resistant and oxidation-resistant carbon fiber reinforced carbon material of the present invention, the mixture of the metal silicide and the metal boride is a metal silicide composed of a metal element selected from Mo, Zr and W. 1-20% of TiB ₂ , TaB ₂ ,
It is preferable that a metal boride selected from ZrB ₂ is mixed.

In the heat-resistant and oxidation-resistant carbon fiber reinforced carbon material of the present invention, the coating of a metal silicide or a mixture of a metal silicide and a metal boride may be formed by a plasma spraying method or an organic coating. It is preferably formed by applying a heat treatment after forming a slurry mixed with a silicon resin or a glass component.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the heat-resistant and oxidation-resistant carbon fiber reinforced carbon material of the present invention will be described. As shown in FIG. 1, a silicon carbide layer (SiC layer) 2 serving as a thermal stress relaxation layer is formed on a surface of a C / C substrate 1 made of a carbon fiber reinforced carbon composite material by diffusing silicon by a diffusion method. A dense silicon carbide layer (SiC layer) on the silicon carbide layer (SiC layer) 2.
Layer 3 is formed, and the surface of silicon carbide layer (SiC layer) 3 is coated with metal silicide 4 or a mixture 5 of metal silicide and metal boride.

As the carbon fibers constituting the carbon fiber reinforced carbon composite material, use is made of two-way laying such as plain weave, satin weave, twill weave, one-way laying, three-way laying, n-direction laying material, felt, tow and the like. As the binder, a thermosetting resin such as a phenol resin and a furan resin, and a thermoplastic resin such as tar and pitch are used. As a method for producing a carbon fiber reinforced carbon composite material, for example, the carbon fiber is prepreg by impregnation with a binder, coating, or the like, and is then heated under pressure to form a molded body. The molded body is cured by heat to completely cure the binder, then fired, and if necessary, graphitized to obtain a carbon fiber reinforced carbon composite material. After that, depending on the application, the thermosetting substance, pitches, etc. are impregnated and densified by an impregnation method of recarburizing, for example, a CVD method of thermally decomposing a hydrocarbon gas such as methane or propane to obtain carbon. By repeating the process, a carbon fiber reinforced carbon composite material having higher strength can be obtained.

As a method for forming a porous silicon carbide layer (SiC layer) by the diffusion method into the carbon fiber reinforced carbon composite material, silicon / silicon carbide / alumina = 15 to 50/28 to
The carbon fiber reinforced carbon composite material is buried in the mixed powder of 85/3 to 25% by weight, and the surface layer of the material is converted into silicon carbide (SiC) by a heat treatment at 1500 to 1800 ° C. The reaction time can be selected according to the desired coating film thickness. The film thickness may be 1 μm or more, preferably 1 μm.
It is preferably from 0 to 200 μm. This porous silicon carbide layer (Si
C layer) becomes a thermal stress relaxation layer.

As the dense silicon carbide coating layer formed on the porous silicon carbide layer (SiC layer), for example, CH ₃ SiCl ₃ , CiCl + CH ₄ or the like as a source gas, or H ₂ or a carrier gas as a carrier gas Using a mixed gas of H ₂ + Ar or the like, a reaction temperature of 900 to 1700 ° C. and a reaction pressure of 760 Torr
In the following, it is preferable to perform the chemical vapor deposition under the condition that the flow ratio of the raw material gas and the carrier gas is (the flow rate of the raw material gas) / (the flow rate of the carrier gas) = 1/5 to 10, and the organic silicon resin, for example, A silicon carbide powder having a particle size of 0.1 to 0.5 μm dispersed in a 20% xylene solution of polycarbosilane at a weight ratio of 1: 1 is coated with a porous silicon carbide layer (Si
It is also preferable that the organic silicon resin is converted into silicon carbide (SiC) by heat treatment at 1000 to 1400 ° C. after application on the (C layer). The film thickness of the dense silicon carbide coating layer formed in this manner may be 50 μm or more, and preferably 100 to 300 μm.

In the metal silicide coated on the surface of the dense silicon carbide coating layer, the metal element constituting the metal silicide is Mo,
It is preferable to select from Zr and W. For example, MoSi ₂ (melting point 2020) composed of these metal elements
° C), Mo ₅ Si ₃ (melting point 2190 ° C), ZrSi (melting point 2095 ° C), Zr ₅ Si ₃ (melting point 2110 ° C), W
Si ₂ (melting point 2160 ° C.), W ₅ Si ₃ (melting point 2350)
C) is a high melting point metal silicide.

The mixture of the metal silicide and the metal boride coated on the surface of the dense silicon carbide coating layer is Mo, Z
MoS composed of a metal element selected from r and W
In metal silicides of i ₂ , ZrSi ₂ and WSi ₂ , 1 to 2
Preferably, it is a mixture of 0% of a metal boride selected from TiB ₂ , TaB ₂ , and ZrB ₂ . The mixing ratio between the metal silicide and the metal boride is preferably from 10: 1 to 1: 1.

The outermost metal silicide coating layer or the mixture layer of the metal silicide and the metal boride is formed by a plasma spraying method or has a higher oxidation resistance than metal silicon, and An organic silicon resin that does not melt after heat treatment, such as a xylene solution of polycarbosilane or a glass component such as silica sol, which has a high temperature (close to 1700 ° C.) at which it begins to soften and flow, and a metal silicide powder or a high melting point metal boron Slurry with a mixture powder with a compound, and apply it to the surface of a dense silicon carbide coating layer.
It is formed by a heat treatment at 0 to 1700 ° C. This film thickness may be 10 μm or more, preferably 50 to 200 μm.
Is good. When a mixture of a metal silicide and a metal boride is coated by the plasma spraying method, a mixture having a predetermined mixing ratio is sprayed, but it may be performed without forming the mixture in advance.

The heat-resistant and oxidation-resistant carbon fiber reinforced carbon material of the present invention having the above-described structure is used to form a carbon fiber reinforced carbon composite material coated with a dense silicon carbide coating layer by a chemical vapor deposition method. High melting point metal silicide with extremely low chemical interaction with silicon and excellent heat resistance and oxidation resistance, or extremely low chemical interaction with silicon carbide and high melting point metal silicide, Since the coating with the excellent metal boride is coated, this coating layer is tough and extremely dense, and can suppress the occurrence of peeling and pores due to the difference in thermal expansion from the underlying silicon carbide. Active oxidation of silicon carbide as a barrier can be suppressed. In addition, the refractory metal silicide itself is protected from oxidation by cutting off the contact with oxygen. The melting point of the refractory metal silicide in the coating layer is 1700, which is the expected temperature of space equipment.
Since the temperature is higher than ℃, the carbon material of the present invention is used for spacecraft, and active oxidation of silicon carbide generated in an environment such as when a spacecraft reenters the atmosphere is effectively prevented. In addition, the life time of the coating layer is significantly increased as compared with the conventional non-oxide coating, so that a heat-resistant and oxidation-resistant carbon fiber reinforced carbon material having excellent durability can be realized.

[0023]

[Example] Ten prepregs in which a phenolic resin was impregnated in a carbon fiber woven fabric were laminated, pressed and heated, fired in an inert atmosphere, and then densified using a coal tar pitch. Four times, a carbon fiber reinforced composite material was obtained. After pressurizing the obtained carbon fiber reinforced composite material to a predetermined size, the carbon fiber reinforced carbon composite material is embedded in a mixed powder having a composition ratio of silicon / silicon carbide / alumina = 25/75/5% by weight. And 1700 ° C., 24
A diffusion reaction was performed for 0 minutes to form a porous silicon carbide layer on the surface of the carbon fiber reinforced carbon composite material. The thickness of this silicon carbide layer was 20 μm. Next, on the surface of the silicon carbide layer,
A dense silicon carbide coating layer was formed by a chemical vapor deposition method. The gas composition was CH ₃ SiCl ₃ / H ₂ = 25/100
Gas flow rate 3 liter / min, pressure 30 To
The reaction was performed at a reaction temperature of 1300 ° C. for 150 minutes. The layer thickness of this dense silicon carbide coating layer was 100 μm. Next, a coating layer of a metal silicide and a coating layer of a mixture of a metal silicide and a metal boride were formed on the surfaces of the dense silicon carbide coating layers of the plurality of carbon fiber reinforced carbon composite materials. The metal silicide coating layers are MoSi ₂ and ZrS, respectively.
It was formed to a layer thickness of 20 μm by plasma spraying of i ₂ and WSi ₂ . The coating layer of the mixture of the metal silicide and the metal boride was formed as follows. That is, MoSi ₂ , ZrS
i, metal silicide of WSi ₂ and TiB ₂ , TaB ₂ , Zr
Mixed powder (mixture ratio of the metal boride B ₂ in a molar ratio of 5:
1) were mixed with a 20% xylene solution of polycarbosilane to form a slurry. The mixing ratio was a mixed powder: polycarbosilane: xylene = 5: 1: 4 by weight. This slurry is applied to the surface of a dense silicon carbide coating layer, dried at room temperature for 12 hours or more, and then heat-treated at 1400 ° C. for 120 minutes in an argon atmosphere to coat a mixture of a metal silicide and a metal boride. A layer was formed. The thickness of this coating layer was 30 μm.

Evaluation Method Six kinds of the heat-resistant and oxidation-resistant carbon fiber reinforced carbon materials of Examples 1 to 6 obtained as described above were heated at 1700 ° C. in the atmosphere of 1000 Pa. The temperature history was about 3 minutes from room temperature to the set temperature, 18 minutes and 20 seconds at the set temperature, and 10 minutes from the set temperature to room temperature. The evaluation was carried out based on the consumption of the underlying dense silicon carbide layer and the observation of the surface and cross section. As a comparative example, there is no metal silicide coating layer on the outermost side,
The sample in which the dense silicon carbide layer was exposed was evaluated. The results are shown in Table 1 below.

[0025]

[Table 1]

[0026]

As can be seen from the above description, the heat resistance of the present invention
Oxidation-resistant carbon fiber reinforced carbon material has a very dense outermost metal silicide coating layer or a mixture of metal silicide and metal boride coating layers, and peeling due to the difference in thermal expansion between the underlying silicon carbide and the silicon carbide. Generation and pores can be suppressed, and active oxidation of silicon carbide, which is the main oxidation-resistant barrier, can be suppressed. Moreover, the carbon material of the present invention has a melting point higher than the expected attainment temperature of space equipment of 1700 ° C., so that the outermost coating layer can be used in space equipment and can be sufficiently used even in an environment such as when a space plane enters the atmosphere. In addition, a heat-resistant and oxidation-resistant carbon material having a significantly increased life time as compared with a conventional carbon material having a non-oxide coating layer and having excellent durability is realized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of a heat-resistant and oxidation-resistant carbon fiber reinforced carbon material of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 C / C base material (carbon fiber reinforced carbon composite material) 2 Porous silicon carbide layer 3 Dense silicon carbide layer 4 Metal silicide 5 Mixture of metal silicide and metal boride

Claims (5)

[Claims] 1. A silicon carbide layer is formed on a surface of a carbon fiber reinforced carbon composite material serving as a base material by diffusion of silicon, and a dense silicon carbide coating layer is formed on the silicon carbide layer.
A heat-resistant and oxidation-resistant carbon fiber reinforced carbon material, wherein the surface of the silicon carbide coating layer is coated with a metal silicide or a mixture of a metal silicide and a metal boride. 2. The heat-resistant and oxidation-resistant carbon fiber reinforced carbon material according to claim 1, wherein the dense silicon carbide coating layer is formed by a chemical vapor deposition method, or carbonized in an organic silicon resin. A heat-resistant and oxidation-resistant carbon fiber reinforced carbon material, which is formed by applying a material in which silicon powder is dispersed and applying heat treatment to convert an organic silicon resin into silicon carbide. 3. The heat-resistant and oxidation-resistant carbon fiber reinforced carbon material according to claim 1, wherein a metal element constituting the metal silicide is selected from Mo, Zr, and W. Heat and oxidation resistant carbon fiber reinforced carbon material. 4. The heat- and oxidation-resistant carbon fiber reinforced carbon material according to claim 1, wherein the mixture of a metal silicide and a metal boride is a metal element selected from Mo, Zr, and W. 1-20% of TiB ₂ ,
A heat-resistant and oxidation-resistant carbon fiber reinforced carbon material characterized by being mixed with a metal boride selected from TaB ₂ and ZrB ₂ . 5. The heat resistance according to claim 1,
In the oxidation-resistant carbon fiber reinforced carbon material, a coating of a metal silicide or a mixture of a metal silicide and a metal boride is formed by a plasma spraying method, or a slurry is mixed with an organic silicon resin or a glass component. A heat- and oxidation-resistant carbon fiber reinforced carbon material formed by heat treatment after application.