JPH1170617A - Coating method for oxidation-resistant multilayered coating film of carbon fiber reinforced carbon composite material, and coated material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating method for a coating film having practical heat resistance of 1700 deg.C or higher and markedly good in the close adhesiveness with a carbon fiber reinforced carbon composite material and the oxidation- resistant multilayered coating film on the composite material and a material coated by this coating method. SOLUTION: In a material wherein a multilayered coating film is applied to the surface of a carbon fiber reinforced carbon composite material and a method for producing the same, a coating film of an intermetallic compd., a coating film of a noble metal, a coating film of first oxide and a coating film of second oxide are formed on the carbon fiber reinforced carbon composite material in this order.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for multi-layer coating a carbon fiber reinforced carbon composite material with a high temperature heat resistant material and / or an oxidation resistant material, and a coated material.

[0002]

2. Description of the Related Art Carbon fiber reinforced carbon composite materials are lightweight and excellent in heat resistance. However, since they are carbon materials, they are easily oxidized, so that they need to be coated with an oxidation resistant film when used in the atmosphere. Conventional oxidation resistant coatings on carbon fiber reinforced carbon composite materials are formed by coating SiC or the like by a conversion method, CVD method, or the like, and cracks generated due to the difference in thermal expansion between the carbon fiber reinforced carbon composite material and SiC are made of a glass material Research has focused on technologies such as sealing.
However, the application temperature of these materials in the atmosphere was limited to about 1700 ° C. due to the material characteristics of SiC.

[0003]

In view of the above situation,
An object of the present invention is to provide a method for forming a coating having a practical oxidation resistance of about 1700 ° C. or higher and having extremely good adhesion between a carbon fiber reinforced carbon composite material and an oxidation resistant multilayer coating thereon, and a coated material. It is to provide.

[0004]

Means for Solving the Problems In order to achieve the above object, the present inventors have made intensive studies, and as a result, the present invention provides
In the method for forming an oxidation-resistant multilayer coating of a carbon fiber reinforced carbon composite material, a carbide is formed on the surface of the carbon fiber reinforced carbon composite material, a coating of a noble metal is formed on the carbide, and the carbide and the noble metal are reacted by heat treatment. Forming a film of an intermetallic compound, forming a noble metal film thereon, forming a first oxide film on this film, and then forming a second oxide film. In an oxidation-resistant composite material obtained by forming an oxidation-resistant multilayer coating on a carbon fiber-reinforced carbon composite material,
An intermetallic compound coating on the carbon fiber reinforced carbon composite material, a noble metal coating on the intermetallic compound coating, a first oxide coating on the noble metal coating and a second oxide coating on the first oxide coating An oxide film is formed.

[0005] The substrate material of the present invention is a carbon fiber reinforced carbon composite material (hereinafter abbreviated as C / C). For example, graphite or carbon fiber obtained from polyacrylonitrile (PAN), pitch or rayon is used as a reinforcing material, The matrix is made of a resin, for example, graphite or carbon obtained by graphitizing or carbonizing a phenol resin.

It is desirable that, for example, an oil agent, dust and the like be removed from the C / C surface before forming a film.

[0007] The multilayer film coated on the surface of C / C is
An intermetallic compound film is formed on C / C, a noble metal film is formed on this film, a first oxide film is formed on the noble metal film, and a second oxide film is formed on the first oxide film. It consists of doing.

These films are formed by a low pressure plasma spraying method, a sol-gel method, a CVD method, an ion plating method, a sputtering method or the like.

The particle size of the oxide and the noble metal forming the coating by the low pressure plasma spraying method of the present invention is preferably 5 to 100 μm, particularly preferably 5 to 50 μm. The thickness of the coating by the thermal spraying method of the present invention is preferably 1
0-50 microns.

In the sol-gel method of the present invention, an object for forming a film is brought into contact with a metal precursor solution obtained by hydrolyzing a metal alkoxide, and the precursor solution penetrates and / or adheres to the surface of the object, especially voids, recesses and the like. After drying, heat treatment is performed to form a film made of a metal oxide on the object. Examples of a method of injecting and / or attaching the precursor solution to the target object include immersing the target object in the precursor solution, spraying the precursor solution on the target object surface, and applying the precursor solution to the target object surface. Any method is applicable as long as the precursor solution can penetrate and / or adhere to the object surface. In order to allow the precursor solution to sufficiently penetrate into voids and the like, immersion treatment under reduced pressure is particularly preferable. A preferred precursor concentration is
0.2 to 1.1 mol / l, particularly preferably 0.3 to 1.1 mol / l
0.5 mol / l.

Examples of alkoxides of metal hafnium include tetraethoxyhafnium {Hf (OC ₂ H ₅ ) ₄ } and tetrabutoxy hafnium {Hf (OC ₄ H ₉ ) ₄ }. Propoxide, aluminum butoxide and the like can be exemplified.

The present invention employs a noble metal having a low oxygen permeability and a high melting point as a coating material in order to improve the oxidation resistance. The noble metal and C / C have a large difference in thermal expansion, so that the adhesion is sufficient. However, it is easy to cause peeling, but the carbide formed on and in C / C reacts with the noble metal to form an intermetallic compound on and in C / C to improve their adhesion. I let it.

The oxide film for forming carbides is preferably formed by a sol-gel method. According to the sol-gel method, a metal precursor solution for forming an oxide is formed by a C / C method.
Since it can be penetrated into recesses, voids and the like in the inside, the contact surface area between C / C and the coating is increased. When the oxide film is converted into a carbide by a conversion method, the adhesion is improved as compared with the case where another method is used. The oxide is preferably hafnium oxide (HfO ₂ ). The preferred carbide thickness is 2-5 microns.

A noble metal film is formed on the obtained carbide by preparing a noble metal slurry using, for example, a noble metal powder and a binder, and applying and drying the slurry. The preferred film thickness is 5
〜１０10 microns. Next, heat treatment is preferably performed at about 1700 ° C. in an inert gas or in a vacuum to react the carbide with the noble metal to form an intermetallic compound. The noble metal includes iridium, rhodium, platinum and the like, and iridium (Ir) is particularly preferable. Iridium has a high melting point of about 2450 ° C., low oxygen permeability, excellent reactivity with hafnium carbide, and promotes formation of intermetallic compounds. At this point, carbides such as C / C surfaces, recesses, and voids are converted to intermetallic compounds, and a film is formed on C / C with sufficient adhesion.

Further, a thick film of a noble metal is formed on the compound by a low pressure plasma spraying method in order to enhance the oxidation resistance. It is preferable to use the same noble metal as the noble metal of the intermetallic compound. The preferred film thickness is between 10 and 50 microns. In order to densify the sprayed layer, usually about 19
Heat treatment is performed at 00 ° C. in an inert atmosphere or in a vacuum.

A first oxide is formed on the sprayed film to prevent iridium from being oxidized and volatilized in practical use. The first oxide is, for example, hafnium oxide, for example, yttrium oxide (III) oxide (Y ₂ O ₃ ) in order to prevent its transformation.
Is added at about 15% by weight. The preferred thickness of the first oxide is 10 to 100 microns.

A second oxide is formed on the first oxide film. This film formation is to prevent oxidation of C / C from cracks due to a difference in thermal expansion between C / C and the coating.
The preferred second oxide is hafnium oxide and alumina (aluminum oxide), and is preferably formed by a sol-gel method. The preferred thickness of the second oxide is 1-5 microns.

[0018]

【Example】

1) Formation of Conversion Method Hafnium Carbide (HfC) A metal precursor solution such as a solution of tetramethoxyhafnium in C / C by sol-gel method in order to form a HfO ₂ coating on unidirectional material and / or woven material C / C. (0.4
mol / l) was impregnated in vacuo and dried sufficiently at 120 ° C. Heat treatment is performed at 1700 ° C. for 3 hours in an inert gas or in a vacuum to cause carbon in C 2 / C to react with HfO ₂ to form HfO _2.
C was formed.

2) Film formation of intermetallic compound An iridium slurry (a mixture of iridium powder, a binder and an organic solvent) was applied on hafnium carbide. 1
After sufficiently drying at 20 ° C, the mixture is dried in an inert gas or in a vacuum.
Heat treatment was performed at 00 ° C. to react iridium and hafnium carbide to form an intermetallic compound (Ir ₃ Hf). At this time, iridium diffused not only into the C / C surface but also inside through the hafnium carbide, and an intermetallic compound was formed in the range schematically illustrated in FIG.

3) Film formation of iridium by low-pressure plasma spraying Iridium was formed on the intermetallic compound by low-pressure plasma spraying. After the film formation, heat treatment was performed at 1900 ° C. in an inert gas or in a vacuum in order to densify the sprayed layer.

4) Formation of First Oxide A low-pressure plasma spraying of an oxidizing compound consisting of 85% by weight of hafnium oxide and 15% by weight of yttrium (III) oxide as the first oxide on the iridium film by plasma spraying. A stabilized hafnium oxide film was formed by thermal spraying.

5) Formation of Second Oxide Film A solution of a metal precursor such as tetramethoxyhafnium (0.4 mol / mol) was formed on the first oxide film by a sol-gel method.
l) is vacuum impregnated, dried sufficiently at 120 ° C.,
It baked for 1-3 hours at 00-500 degreeC.

Evaluation of Oxidation Resistance After performing oxidation exposure in the air at 1800 ° C. or 1900 ° C. for 30 minutes, a high-temperature tensile test was performed at each of the above temperatures in a vacuum.
a At 1900 ° C., a strength of about 250 MPa was obtained.
These strengths were about 80% and about 56%, respectively, with respect to room temperature strength.

[0024]

According to the multilayer coating obtained by the method of the present invention and the material having the multilayer coating, iridium as an intermetallic compound and C / C are particularly excellent in adhesion, and therefore, peeling at the interface between them. However, it is extremely unlikely to occur, and oxidation of iridium is suppressed in a high-temperature environment, and therefore, it has excellent oxidation resistance in a high-temperature environment of 1700 ° C. or more.

[Brief description of the drawings]

FIG. 1 is a schematic view of an oxidation-resistant multilayer coating of the present invention.

Claims (11)

[Claims] 1. A method for forming an oxidation-resistant multilayer coating of a carbon fiber reinforced carbon composite material, comprising: forming a carbide on the surface of the carbon fiber reinforced carbon composite material; forming a film of a noble metal on the carbide; Reacting the carbide and the noble metal to form a coating of an intermetallic compound, forming the noble metal coating thereon, forming a first oxide coating on the coating,
Next, a second oxide film is formed. 2. The method according to claim 1, wherein the carbide is formed by heat-treating a hafnium oxide film by a sol-gel method. 3. The method according to claim 1, wherein the noble metal is iridium. 4. The method according to claim 3, wherein the intermetallic compound is an iridium-hafnium-based intermetallic compound.
The described method. 5. The method according to claim 1, wherein the first oxide is stabilized hafnium oxide. 6. The method according to claim 1, wherein said second oxide film is formed of hafnium oxide or aluminum oxide formed by a sol-gel method. 7. An oxidation-resistant composite material in which an oxidation-resistant multilayer film is formed on a carbon fiber-reinforced carbon composite material, wherein an intermetallic compound film is formed on the carbon fiber-reinforced carbon composite material and a noble metal film is formed on the intermetallic compound film. An oxidation-resistant composite material comprising a first oxide film formed on a film and a noble metal film, and a second oxide film formed on the first oxide film. 8. The material according to claim 7, wherein said noble metal is iridium. 9. The intermetallic compound according to claim 8, wherein the intermetallic compound is an iridium-hafnium-based intermetallic compound.
The described material. 10. The material according to claim 7, wherein the first oxide is stabilized hafnium oxide. 11. The method according to claim 7, wherein said second oxide is hafnium oxide or aluminum oxide.
11. The material according to any one of items 1 to 10.