JPH07277861A - Oxide coated silicon carbide material and its production - Google Patents

Abstract

PURPOSE:To improve oxidation resistance by coating a surface with a silicide which is a reaction product of an oxide of lanthanoid rare earth element or its double oxide with silicon and silicon carbide. CONSTITUTION:A silicon carbide raw material which a raw material almost constituted of silicon carbide, or a platelike carbon material of carbon/carbon composite or the like, or a plate-like silicon nitride sintered body is coated with silicon carbide on all or a part of the surface by a chemical vapor deposition method to form is subjected to interfacial reaction with a lanthanoid silicide which is a reaction product of silicon carbide a oxide of a lanthanoid rare earth element (including yttrium) or its double oxide with silicon and has a composition of 30atm% C and 5atm% O by a sputtering method, a slurry coating and sintering method or the like, allowing a precursor of lanthanoid rare earth element oxide-contg. coating film coated silicon carbide material to be obtained. The surface of this is coated with a lanthanoid oxide or its double oxide with silicon by a plasma spraying method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a lanthanoid-based rare earth element oxide-containing film-coated silicon carbide which is advantageously applied as a heat resistant structural material for space vehicles, next-generation supersonic passenger aircraft, engine parts and gas turbines. The present invention relates to a material, a precursor thereof, a lanthanoid silicide-coated silicon carbide material, and a method for producing a lanthanoid-based rare earth element oxide-containing coating silicon carbide material.

[0002]

2. Description of the Related Art In order to improve the oxidation resistance of a silicon carbide material, there has been proposed a silicon carbide material in which the surface of the silicon carbide material is coated with various metal oxide layers having excellent oxidation resistance. However, silicon carbide cannot provide sufficient oxidation resistance because it has poor adhesion with other metal oxide coatings, except for the silicon dioxide coating formed by oxidation of itself.

Therefore, in order to bring the silicon carbide material and the metal oxide having excellent oxidation resistance into close contact with each other, a method has been proposed in which an intermediate layer is provided between the two to improve the adhesion (Japanese Patent Laid-Open No. 3-221444). Japanese Patent Application No. 4-202230). However, some problems have been recognized in the method of providing the intermediate layer. JP-A-3-221444
The intermediate layer proposed in the publication is composed of a metal oxide and a metal carbide, and both of them form a reaction product in a high temperature environment, so that there is a problem in durability. Also,
The method proposed in Japanese Patent Application No. 4-202230 is based on the combination of a lanthanoid-based rare earth element (including yttrium) oxide and silicon carbide or a lanthanoid-based rare earth element (including yttrium). It does not specifically apply to a combination of silicon oxide and a composite oxide with silicon. In addition, when these combinations are actually applied, depending on the composition of the intermediate layer, leaving them in the air for a long period of time causes dusting due to oxidation, etc., so bonding must be performed within a very short time. There was a possibility that such a problem would occur. Further, in the metals such as thorium and hafnium disclosed in the above-mentioned prior specification, since the thermal expansion coefficient of the metal oxide is different from that of silicon carbide, the thermal stress during heating is large and the adhesion is insufficient. Is.

[0004]

In view of the above-mentioned state of the art, the present invention provides a silicon carbide material and a metal oxide excellent in oxidation resistance,
That is, a lanthanoid-based rare earth element oxide-containing coating-coated silicon carbide material in which an oxide of a lanthanoid-based rare earth element (including yttrium) is firmly adhered, a method for producing the same, and a lanthanoid-based rare earth element oxide-containing coating-coated silicon carbide. It is intended to provide a lanthanoid silicide-coated silicon carbide material which is a precursor of a material.

[0005]

Means for Solving the Problems The present invention is (1) a silicon carbide material having a surface covered with a silicide, wherein the silicide is composed of an oxide of a lanthanoid rare earth element (including yttrium) and silicon carbide. A lanthanoid silicide-coated silicon carbide material, which is a reaction product or a reaction product of a complex oxide of a lanthanoid-based rare earth element (including yttrium) and silicon, and silicon carbide,
(2) The composition of the silicide is characterized in that the lanthanoid-based rare earth element (including yttrium) and silicon are main components, and the rest occupy up to 30 atom% of carbon and up to 5 atom% of oxygen. The (1) lanthanoid silicide-coated silicon carbide material, and (3) the silicon carbide material is a carbon material whose surface is covered with silicon carbide. Silicon material, (4) Carbon material is carbon / carbon composite, lanthanoid silicide-coated silicon carbide material of (3), (5) Lanthanoid silicide coating of any one of (1) to (4) above An oxide of a lanthanoid-based rare earth element (including yttrium) or a lanthanoid-based rare earth element (but it) A lanthanoid-based rare earth element oxide-containing film-coated silicon carbide material, characterized by being coated with a complex oxide of (including um) and silicon; The surface of the silicide-coated silicon carbide material is coated with a lanthanoid rare earth element (including yttrium) oxide or a composite oxide of a lanthanoid rare earth element (including yttrium) and silicon by plasma spraying. A method for producing a film-coated silicon carbide material containing a lanthanoid rare earth oxide. (7) The above (1) to (4)
Of the lanthanoid-based rare earth element (including yttrium) oxide or a composite oxide of lanthanoid-based rare earth element (including yttrium) and silicon on the surface of any of the lanthanoid silicide-coated silicon carbide materials by plasma spraying And then heat-treated in the atmosphere or in an inert gas atmosphere to enhance the denseness and adhesion of the oxide of the lanthanoid rare earth element or the complex oxide coating of lanthanoid rare earth element and silicon. A method for producing a film-coated silicon carbide material containing a lanthanoid-based rare earth element oxide.

[0006]

As the silicon carbide material referred to in the present invention, a material that is mostly composed of silicon carbide, a material whose surface is partially covered with silicon carbide, and a material whose surface is entirely covered with silicon carbide can give. Most of the materials composed of silicon carbide are materials produced by sintering silicon carbide powder with carbon, boron or alumina as an auxiliary agent, and most of the commercially available materials are silicon carbide. is there. As a material whose surface is partially covered with silicon carbide, a material in which one surface of a plate-shaped carbon material such as carbon / carbon composite is coated with silicon carbide by a chemical vapor deposition method, or a plate-shaped silicon nitride sintered body One example is a material in which one surface of the is coated with silicon carbide by a chemical vapor deposition method. Further, as a material whose entire surface is covered with silicon carbide, a carbon material such as carbon / carbon composite is coated with silicon carbide by a chemical vapor deposition method, or one surface is coated with silicon carbide by a chemical vapor deposition method. Examples include a material in which one surface of a silicon nitride sintered body is coated with silicon carbide by a chemical vapor deposition method.

The lanthanoid silicide-coated silicon carbide material of the inventions (1) to (4) has the status of a precursor of the lanthanoid rare earth element oxide-containing film-coated silicon carbide material of (5) to (7). Is. Here, the silicon carbide material whose surface is covered with the lanthanoid silicide is not limited to one in which the lanthanoid silicide covers the entire surface of the silicon carbide material, but also one in which the surface is partially covered. For example, a part of the outer surface (corresponding to a diameter of 1 meter) of a semi-spherical member with a diameter of 2 meters, which is considered to be used in a space shuttle, is coated with one side with a plate-shaped member, The end and the other surface are not covered, and the pipe-shaped member is coated on the outer surface but not the inner surface.

As the lanthanoid rare earth elements (including yttrium, which are included in the lanthanoid silicide of the inventions (1) to (4)), yttrium (Y) and lutetium are used as the lanthanoid rare earth elements (including yttrium. (Lu), ytterbium (Yb), thulium (T
m), erbium (Er), holmium (Ho), dysprosium (Dy), terbium (Tb) and gadolinium (Gd) are selected, but yttrium and then ytterbium are preferable in terms of cost.

The lanthanoid silicide of the inventions (1) to (4) is composed of a substance formed by a chemical reaction between silicon carbide and Ln oxide, and Ln and silicon are the main components. The rest is carbon and oxygen. Here, the Ln oxide includes an oxide of Ln and a complex oxide of Ln and silicon. In this case, as shown in the invention of the above (2), by making the composition of the lanthanoid silicide to be at most 30 atom% of carbon and at most 5 atom% of oxygen, it is possible to suppress dusting of the lanthanoid silicide.

In the above inventions (1) to (4), the silicon carbide material covered with the lanthanoid silicide is a sputtering method of an oxide of Ln or a composite oxide of Ln and silicon, a method of applying a slurry and baking the same. Can be produced by interfacial reaction with a silicon carbide material. Since these lanthanoid silicides are produced as an interfacial reaction product of Ln oxide or a complex oxide of Ln and silicon and silicon carbide, they easily adhere to the silicon carbide which is the raw material, and further, the lanthanoid rare earth element oxidation which is the target product. Also easily adheres to an oxide of Ln or a composite oxide of Ln and silicon applied when manufacturing a substance-containing film-coated silicon carbide material (hereinafter, abbreviated as Ln oxide-containing film-coated silicon carbide material). .

The Ln oxide-containing coating-coated silicon carbide material of the invention (5) is a silicon carbide whose surface is covered with the lanthanoid silicide (1) to (4) (hereinafter, abbreviated as Ln silicide). A film-coated silicon carbide containing an Ln oxide having excellent oxidation resistance, in which the surface of a material precursor is coated with an oxide of Ln or a composite oxide of Ln and silicon. The oxides of Ln and the composite oxides of Ln and silicon have an oxygen barrier function (difficulty in permeation when a certain substance is formed into a film and oxygen atoms are diffused and permeated therein. Good), especially when Ln is yttrium.

Furthermore, since Ln silicide has already been formed on the surface of the precursor, when it is coated with Ln oxide or a complex oxide of Ln and silicon having excellent oxidation resistance, it adheres to the precursor sufficiently firmly. Ln oxide-containing coatings can be formed. Particularly, in a complex oxide (silicate) in which Ln is yttrium, ytterbium, dysprosium, or erbium, the coefficient of thermal expansion of each is about 5 × 10 ⁻⁶ / ° C., which is almost the same as that of the underlying silicon carbide, and Also, the thermal stress hardly occurs, and the adhesion becomes better.

The inventions of the above (3) and (4) are, respectively, in the inventions of the above (1) and (2), wherein the surface of the silicon carbide material is covered with silicon carbide or the surface thereof is covered with silicon carbide. It is made of carbon / carbon composite, and can be a very useful ultimate material because it has the characteristics of carbon material such as light weight, high strength, and heat resistance.

The inventions of (6) and (7) above relate to a method for producing the Ln oxide-containing coating-coated silicon carbide material of the invention of (5) above, and the precursors of the inventions of (1) to (4) above. This is a method of coating the surface of Ln oxide or a composite oxide of Ln and silicon by plasma spraying. This is generally achieved by spraying at atmospheric pressure using argon and helium as the plasma gas and argon gas as the carrier gas. In the invention of (7) above, after the Ln oxide or the composite oxide of Ln and silicon is sprayed on the precursor of the inventions of (1) to (4) by the plasma spraying method of the invention of (6) above, This is a heat treatment method for more firmly adhering the sprayed layer to the precursor, and the heat treatment is performed in the air or an inert gas. The temperature of the heat treatment conditions,
The time and the like cannot be unconditionally specified depending on the kind of the precursor and the kind of the Ln oxide or the composite oxide of Ln and silicon, but one example is heating at 1700 ° C. in argon gas for 1 hour and then 1500 ° C. in the atmosphere. A heat treatment method of heating for 1 hour can be used.

[0015]

EXAMPLES The effects of the present invention will be made clearer by giving various examples of the present invention. Examples 1 to 5 are examples of the method for producing the precursor of the Ln oxide-containing coating-coated silicon carbide material, and Example 6 is an example of the method of producing the Ln oxide-containing coating-coated silicon carbide material.

(Example 1) A slurry of yttria powder was applied to the surface of silicon carbide, dried, and dried in an Ar atmosphere at 1
By performing the heat treatment at 700 ° C., the surface could be coated with yttrium silicide consisting of 45 atom% of yttrium, 30 atom% of silicon, 23 atom% of carbon, and 2 atom% of oxygen.

Example 2 A slurry of yttria powder was applied to the surface of silicon carbide, dried, and heat-treated at 1700 ° C. in a carbon monoxide gas atmosphere to give 45 atomic% of yttrium and 5% of silicon on the surface. Atomic%, carbon 48 atomic%, oxygen 2 atomic% yttrium silicide (however,
Yttrium Carbide).

Example 3 A surface of silicon carbide was slurried with a mixed powder of yttria and silica (SiO ₂ ) in a molar ratio of 1: 1 to form a coating film, which was then dried and heat-treated at 1700 ° C. in an Ar atmosphere. As a result, it was possible to cover the surface with yttrium silicide containing 30 atomic% of yttrium, 60 atomic% of silicon, 8 atomic% of carbon, and 2 atomic% of oxygen.

(Example 4) Of the reaction products of yttria or a composite oxide having a molar ratio of yttria and silica of 1: 1 and silicon carbide, materials having the composition shown in Table A were prepared by a melting method, and Was processed into a sputter target and coated on silicon carbide by a sputtering method, and then heat-treated at 1700 ° C. in an Ar atmosphere to finally produce a silicon carbide material coated with the interface reaction layer shown in Table A. The melting was performed by arc melting in an Ar atmosphere, and tungsten was used for the electrodes. The raw material is yttrium powder having a purity of 99.9 atom%, alloy powder having a composition of yttrium 90.5 atom% and oxygen of 9.5 atom%, purity 99.9 atom% carbon powder, purity 99.9 atom%. The silicon powder of No. 1 was used, and a mixture thereof was pressed into pellets, placed on a water-cooled copper electrode hearth, and melted to prepare a raw material.

(Example 5) Of the reaction products of ytterbium or the complex oxide having a molar ratio of ytterbium and silica of 1: 1 and silicon carbide, the materials having the compositions shown in Table B were prepared by a melting method and then sputtered. After being processed into a target and coating silicon carbide by a sputtering method, heat treatment was performed at 1700 ° C. in an Ar atmosphere to finally produce a silicon carbide material coated with an interface reaction layer having a composition shown in Table B. The melting was performed by arc melting in an Ar atmosphere, and tungsten was used for the electrodes. The raw material is ytterbium powder with a purity of 99.9 atom%, and the composition is ytterbium 9
Alloy powder containing 0.8 atomic% and 9.2 atomic% oxygen, purity 9
Using 9.9 atomic% carbon powder and 99.9 atomic% pure silicon powder, a mixture of the powders was compacted into pellets, placed on a water-cooled copper electrode hearth, and melted to prepare a raw material. .

[0021]

[Table 1]

[0022]

[Table 2]

Of the samples prepared according to Examples 1 to 3, Example 1
The yttrium silicide-coated silicon carbide material produced in Example 3 and Example 3 did not become dust even if left in the atmosphere for 24 hours or more, but the yttrium silicide (including a large amount of yttrium carbide) coated carbonaceous material produced in Example 2 was used. Silicon became dust within 1 hour. However, the adhesion of the coating film when formed was good. Further, from Table A showing the results of examining the one produced in Example 4, regarding the composition of yttrium silicide, the main component was composed of yttrium and silicon, and the balance was 30 atoms% at maximum in carbon and 5 atoms at maximum in oxygen. It was confirmed that dusting can be prevented in the range of%.

Regarding the sample prepared in Example 5 above,
From Table B showing the results of dusting by leaving it in the air, the composition of ytterbium silicide is composed of ytterbium and silicon as the main components, and the balance of carbon is at most 30.
It was confirmed that dusting can be prevented in the range of 5% by atom and at most 5% by atom of oxygen. From the results of these yttria and ytterbium, it is expected that the lanthanoid-based metallic elements have similar effects.

Example 6 The constitution of the Ln oxide-containing coating-coated silicon carbide material of the present invention will be described with reference to FIG. In FIG. 1, 1 is a silicon carbide base material, 2 is an Ln silicide layer, 3 is L
It is a film containing n oxide. The Ln silicide layer 2 is a layer formed according to Example 4 above.

Using the silicon carbide base material having the Ln silicide formed on the surface shown in the above example and the silicon carbide base material having no treatment on the surface as a comparison material, various Ln oxide-containing coatings were plasma-treated. The Ln oxide-containing coating-coated silicon carbide was manufactured by thermal spraying. Plasma spraying was carried out at atmospheric pressure using argon and helium as plasma gases and argon as a carrier gas. After that, a part of the material of the present invention was heated in argon gas at 1700 ° C. for 1 hour and then in the atmosphere. Heat treatment was performed by heating at 1500 ° C. for 1 hour. The results are summarized in Table C.

[0027]

[Table 3]

[0028]

[Table 4]

Table D shows the plasma spray test results and 170
The results obtained by repeating 90 minutes of heating twice in the atmosphere of 0 ° C. are shown. In each of the comparative materials, the sprayed film did not adhere to each other and cracks or peeling occurred in the film, but in the present invention, the adhered Ln oxide-containing coating on the substrate was maintained. Next, regarding the situation after the heating test, in all the comparative materials whose film formation was incomplete, the film peeled off and fell off, and bubbles of silicon oxide were formed on the surface of the silicon carbide substrate, resulting in surface roughness and weight. Although a decrease was confirmed, no change in appearance was observed in any of the materials of the present invention, and a change in weight was slight. In particular, it was observed that the heat treated material after thermal spraying had a smaller change in weight than the non-heat treated material.

[0030]

[Table 5]

[0031]

[Table 6]

[0032]

The present invention provides a silicon carbide material coated with a lanthanoid-based rare earth element oxide film having excellent oxidation resistance, and a lanthanoid silicide coating with less dusting of the coated lanthanoid silicide as a precursor of the silicon carbide material. A silicon carbide material can be provided, and its industrial effect is extremely remarkable.

[Brief description of drawings]

FIG. 1 is a schematic view of a lanthanoid-based rare earth element oxide film-coated silicon carbide material of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kei Notomi 5-717-1, Fukahori-cho, Nagasaki-shi, Nagasaki Sanryo Heavy Industries Ltd. Nagasaki Research Institute

Claims (7)

[Claims] 1. A silicon carbide material whose surface is covered with a silicide, wherein the silicide is a reaction product of an oxide of a lanthanoid-based rare earth element (including yttrium) and silicon carbide or a lanthanoid-based rare earth element (however. , Yttrium) and a complex oxide of silicon and a reaction product of silicon carbide and a lanthanoid silicide-coated silicon carbide material. 2. The composition of the silicide is a lanthanoid-based rare earth element (including yttrium) and silicon as main components, with the balance being carbon at a maximum of 30 at%, and oxygen at a maximum of 5 at%.
The lanthanoid silicide-coated silicon carbide material according to claim 1, characterized in that 3. The lanthanoid silicide-coated silicon carbide material according to claim 1, wherein the silicon carbide material is a carbon material whose surface is covered with silicon carbide. 4. The lanthanoid silicide-coated silicon carbide material according to claim 3, wherein the carbon material is a carbon / carbon composite. 5. A lanthanoid rare earth element (including yttrium) oxide or a lanthanoid rare earth element (including yttrium) is formed on the surface of the lanthanoid silicide-coated silicon carbide material according to claim 1. ) And silicon, a lanthanoid-based rare earth element oxide-containing coating-coated silicon carbide material. 6. A lanthanoid-based rare earth element (including yttrium) oxide or a lanthanoid-based rare earth element (including yttrium) is formed on the surface of the lanthanoid silicide-coated silicon carbide material according to any one of claims 1 to 4. And a silicon compound oxide are coated by a plasma spraying method. A method for producing a film-coated silicon carbide material containing a lanthanoid-based rare earth element oxide. 7. A lanthanoid-based rare earth element (including yttrium) oxide or a lanthanoid-based rare earth element (including yttrium) is formed on the surface of the lanthanoid silicide-coated silicon carbide material according to any one of claims 1 to 4. ) And silicon compound oxide by a plasma spraying method, and then heat-treated in the atmosphere or in an inert gas atmosphere to form a lanthanoid rare earth element oxide or a lanthanoid rare earth element and silicon compound oxide film. A method for producing a film-coated silicon carbide material containing a lanthanoid-based rare earth element oxide, which is characterized by increasing the denseness and the adhesiveness.