JP2008069403A - Anti-oxidation coating structure and coating method of heat-resistant alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-resistant alloy having a coating structure superior in anti-oxidation, by suppressing the peeling of a surface oxide layer for intercepting oxygen from the alloy and the progress of oxidation. <P>SOLUTION: In the anti-oxidation coating structure of the heat-resistant alloy, a first layer alloy film for preventing diffusion is formed on the surface of the heat-resistant alloy as needed, and on the first layer alloy film, a second layer composite film, in which oxide fibers and particles are dispersed in an alloy layer containing at least Al or Si, is formed. Specially in the case where the heat-resistant alloy is a niobium-based alloy, the first layer alloy film is made to contain Re and at least two kinds of elements forming a stable phase with Re, and the second layer film is made to be a film, in which oxide fibers and oxide particles are scattered in an alloy layer containing at least Al and at least one kind of Cr and Ni. Here, as the fibers, oxide-based ceramic fibers having an aspect ratio of 2-1,000 or whiskers are used; and as the particles, oxide-based ceramic particles of an average size of 1-50 μm are used. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a heat-resistant alloy such as a niobium-based alloy used in gas turbines, jet engines, etc., and in particular, an oxidation-resistant coating structure of a heat-resistant alloy in which a film for suppressing high-temperature oxidation is formed on a substrate surface and the coating thereof Regarding the method.

  In recent years, a further increase in operating temperature of a gas turbine for power generation has been demanded, and a new heat-resistant material having a higher use temperature limit is required than Ni-based alloys that have been widely used as turbine members. One of such materials is a niobium (Nb) -based heat-resistant material such as a solid solution strengthened or precipitation strengthened Nb alloy or Nb-Al intermetallic compound (in the present invention, these are called niobium-based alloys). ) Is attracting attention.

  These niobium-based alloys are excellent in high-temperature strength, but all of these niobium-based alloys are very easily oxidized in a high temperature range, for example, a temperature range of 800 ° C. or higher, and are difficult to use as they are in a high-temperature oxidizing atmosphere such as a gas turbine. Various studies have been made on coatings aimed at oxidation resistance.

Conventionally, a method of forming a diffusion layer of Cr or Al or a method of ceramic coating has been studied as a heat-resistant / oxidation-resistant coating for a metal member used in a high-temperature oxidizing atmosphere. Particularly in Ni-based alloys, a method called thermal barrier coating (TBC) has become the mainstream. This is formed by laminating a metal bond layer on the substrate surface and a ceramic heat shield layer on the surface. The metal bond layer is MCrAlY alloy (M = Ni, Co, etc.), and the heat shield layer is ZrO. Ceramics mainly composed of ₂ are often used.

  As the oxidation-resistant coating of the niobium-based alloy, an Ir surface coating layer or an Ir surface coating layer and a diffusion prevention layer mainly composed of one or more of Ta, Re, and W are formed below the Ir surface coating layer. An Nb alloy heat-resistant member is disclosed (Patent Document 1 below). Also disclosed is a method for producing an oxidation-resistant coating layer in which Ir is vacuum-deposited on the surface of the substrate and simultaneously irradiated with Al ions to form a coating layer made of an Ir—Al alloy (Patent Document 2 below).

In addition, the present inventors have also proposed a heat-resistant member of a two-obtain base alloy that is excellent in oxidation resistance in addition to heat resistance (Patent Document 3 below). This heat-resistant member has a first layer (diffusion prevention layer) film made of a Re-based alloy for preventing the diffusion of constituent elements on the surface of a two-bobium-based alloy substrate, and an oxide film (Al ₂ O) on the surface. ₃ or SiO ₂ ) and a second layer (antioxidation layer) film made of an Al-based alloy or an Si-based alloy that supplies Al or Si to form a two-layer oxidation-resistant film.

Japanese Patent Laid-Open No. 10-14333 Japanese Patent Laid-Open No. 10-140347 WO02 / 27067A1 (Japanese Patent Application 2002-53027) Shibata, Ichihashi: Gifu Prefectural Research Institute of Product Technology No. 4,2003

The two-obtain base alloy having the above-mentioned two-layer coating previously proposed by the present inventors has both oxygen barrier properties and diffusion resistance of the oxidation-resistant coating, and is excellent in oxidation resistance in addition to heat resistance. In particular, by providing an intermediate coating layer of an Re-based alloy, this suppresses the diffusion of elements between the surface film and the base material, so that alteration of the oxidation resistant film can be prevented, and the durability of the film is ensured. However, the niobium-based alloy that is the subject of the present invention is intended for use in a temperature range of 1200 ° C. or higher, which is not compatible with a nickel-based alloy having the highest heat resistance as a practical metal material. It has been found that in such an ultra-high temperature range, the coating is easily peeled off due to the difference in thermal expansion coefficient between Al ₂ O ₃ formed on the surface and the internal alloy, and the progress of oxidation due to this is not negligible.

In order to solve this problem, the present inventors added a short fiber or whisker-shaped oxide to the antioxidant layer, thereby connecting the Al ₂ O ₃ or SiO ₂ oxide film formed on the surface and the inner alloy. It has been found that separation due to the difference in thermal expansion coefficient, and thus the progress of oxidation, can be remarkably suppressed, and a patent application has been filed earlier (Japanese Patent Application No. 2005-072639).

This method is to add 3% by volume or more of oxide fiber to the antioxidant layer (which produces an Al ₂ O ₃ or SiO ₂ oxide film). In the temperature range of 1350 ° C. or less, the fiber is prevented from being wedged. It has been confirmed that the effect can remarkably reduce the peeling of the oxide film and suppress the progress of oxidation.
However, in subsequent studies, it may be necessary to increase the amount of oxide fiber added to the antioxidant layer alloy in order to exhibit the oxidation resistance function in a higher temperature range (for example, a temperature range of about 1500 ° C.). It was discovered. Moreover, if the fiber content is too high, sintering tends to be difficult. For this reason, it becomes difficult to form a dense antioxidant layer. Accordingly, in a temperature range of about 1500 ° C., if the fiber content is, for example, 20% by volume or more, the oxidation is promoted to have an adverse effect. It was found to occur.
Therefore, in order to sufficiently exhibit the oxidation resistance function in a higher temperature range, further improvement is necessary with respect to prevention of peeling of the oxide film.

Accordingly, the present invention provides a heat-resistant member having an oxidation-resistant layer made of an Al-based alloy or Si-based alloy on the surface of a heat-resistant alloy, particularly a niobium-based alloy, or a diffusion-preventing layer made of a Re-based alloy on the surface of the substrate. In a heat-resistant member having a two-layer oxidation-resistant coating structure with the antioxidant layer on the surface, peeling of the film due to the difference in thermal expansion coefficient between the Al ₂ O ₃ film or SiO ₂ film formed on the outermost surface and the internal alloy It is an object to provide means capable of preventing the occurrence of cracks even under more severe temperature conditions. That is, a further improved means capable of suppressing the exfoliation of the oxide film due to thermal expansion and the progress of oxidation due to thermal expansion even in a higher temperature range (for example, about 1500 ° C. or higher) than the previous application described above. The issue is to provide.

As a result of studying various anti-peeling measures, the present inventors have added oxidation particles in addition to fibers to the surface anti-oxidation layer to oxidize Al ₂ O ₃ or SiO ₂ formed on the surface. The film peeling due to the difference in thermal expansion coefficient between the material film and the inner alloy is suppressed, the connecting action of the oxide film by the fiber and the inner alloy works more reliably, and the effect of suppressing the progress of oxidation is further increased. I found it.
The first of the oxidation-resistant coating structure of the heat-resistant alloy of the present invention based on this knowledge is an oxidation-resistant film in which oxide fibers and particles are dispersed in an alloy layer containing at least Al or Si on the surface of the base material of the heat-resistant alloy. Is formed.

  In the second of the oxidation resistant coating structure of the heat resistant alloy of the present invention, a first layer alloy film for preventing diffusion is formed on the surface of the base material of the heat resistant alloy, and at least Al or Si is further formed on the surface. A second layer film in which oxide fibers and particles are dispersed is formed in an alloy layer containing.

In a second oxidation coating structure described above, when heat-resistant alloy is a niobium-based alloy, an alloy film of the first layer, in the general formula _{Re 1-ab M a R b} ( wherein, M represents Cr, One or more elements of Ni and Al, R is one or more elements of Nb, Mo, W, Hf, and C, and a and b are atomic ratios of M and R, respectively). It is preferable that the second layer film is one in which oxide particles and fibers are dispersed in an alloy layer containing at least Al and at least one of Cr and Ni.

In the oxidation-resistant coating structure of the niobium-based alloy, the alloy film of the first layer has a general formula Re _1-de T _d R _e (where T is one or more elements of Cr and Si, R Is one or more elements selected from the group consisting of Nb, Mo, W, Hf, Zr and C, and d and e are atomic ratios of T and R, respectively. In addition, the second layer coating may be one in which oxide fibers and particles are dispersed in an alloy layer containing at least Si and at least one of Mo, W, and Nb.

In any of the above oxidation-resistant coating structures, the fibers are one or more selected from the group consisting of oxide ceramic fibers or whiskers, and have an average aspect ratio of 2 to 1,000. It is preferable that it consists of a fiber or a whisker, and the content rate of the fiber in a 2nd layer membrane | film | coat is 3-15 volume%.
The oxide particles are one or more of oxide-based ceramic powders, and are composed of particles having an average particle diameter of 1 to 50 μm, and the oxide particles in the second layer film The content is preferably 5 to 40% by volume.
Furthermore, the sum of the content ratios of these oxide fibers and oxide particles is preferably 20 to 50% by volume.
Note that the fibers and particles of the oxide can be used in appropriate combination depending on the heat resistant temperature.

  The first heat-resistant alloy coating method of the present invention is a method for forming the first oxidation-resistant coating structure, wherein the heat-resistant alloy base material surface includes at least Al or Si-containing metal powder and oxide fibers. In addition, a coating film of a paint in which particles and particles are dispersed in a binder is formed, and then heat treatment is performed to sinter the metal powder in the coating film.

The second heat-resistant alloy coating method of the present invention is a method of forming the second oxidation-resistant coating structure, wherein the first layer alloy film is formed on the surface of the heat-resistant alloy substrate,
Further, a heat treatment for forming a coating film of a paint in which metal powder containing at least Al or Si and oxide particles and fibers are dispersed in a binder on the surface and then sintering the metal powder in the coating film It is characterized by giving.

  In any of the above coating methods, two or more metal powders may be reacted by a combustion synthesis method to generate an intermetallic compound during the heat treatment.

According to the present invention, a niobium-based alloy having an antioxidant layer made of an Al-based alloy or Si-based alloy on the substrate surface, or a diffusion-preventing layer made of a Re-based alloy on the substrate surface, and the antioxidant layer on the surface thereof In the niobium-based alloy having the two-layered oxidation-resistant film, the wedge-preventing effect of the fibers contained in the Al ₂ O ₃ or SiO ₂ film formed on the outermost surface, the oxide particles in the antioxidant layer, and Due to the effect of reducing the difference in coefficient of thermal expansion between this layer and the outermost oxide layer by the addition of fibers, it is possible to prevent the peeling of the oxide layer film and the occurrence of cracks, especially at high temperatures. The effect of suppressing the progress of oxidation due to these film defects is great.
The oxidation-resistant coating structure of the present invention is particularly useful in the case of niobium-based alloys, but can also be applied to other heat-resistant alloys such as nickel-base, chromium-base, cobalt-base, and molybdenum-base alloys.

FIG. 1 is a schematic cross-sectional view showing an oxidation resistant coating structure of a niobium-based alloy according to the present invention. The oxidation-resistant coating is composed of two layers, the lower first layer coating 2 is an alloy coating, and the upper second layer coating 3 has oxide particles 4 and fibers 5 dispersed in the alloy layer. This is a composite film. The second layer film 3 contains a metal element (Al or Si) that becomes an oxide in the alloy layer, which is oxidized by an oxidizing gas in the atmosphere, and an oxide layer (Al _{2 on the} surface). By generating O ₃ or SiO ₂ ), non-metallic elements such as oxygen and nitrogen in the atmosphere are blocked. On the other hand, the first layer coating 2 is mainly intended to prevent the diffusion of elements between the substrate 1 and the second layer coating 3.

FIG. 2 is a schematic cross-sectional view showing the change in the coating after the niobium-based alloy having the above oxidation-resistant coating structure is exposed to high-temperature air. As can be seen in the figure, a dense oxide layer 6 is formed on the surface of the alloy film 3 of the second layer. The oxide layer 6 is mainly made of Al ₂ O ₃ or SiO ₂ , and has a high element blocking ability even if the layer thickness is small. Since the first layer film 2 is a very stable phase containing Re and has a large effect of suppressing diffusion, it is possible to prevent the second layer film 3 from being decomposed or altered by thermal diffusion.

  First, the reason why the oxide particles 4 and the fibers 5 are dispersed in the second layer coating 3 in the oxidation resistant coating structure of the present invention will be described. When the oxide layer 6 formed on the surface of the second layer film 3 is detached due to peeling or the like, the oxide layer 6 is regenerated by oxidizing Al or Si on the surface where the alloy layer is exposed. Therefore, it has a self-repair function. However, since the difference in coefficient of thermal expansion between the oxide layer 6 and the alloy layer (second layer coating) 3 main body is extremely large, it is very easy to separate. Therefore, by including the oxide particles 4 and the fibers 5, the thermal expansion coefficient of the second layer is lowered, and the difference from the thermal expansion coefficient of the outermost oxide layer is reduced. Further, the fiber 5 has an effect of preventing the outermost oxide layer 6 from falling off by the wedge-preventing effect even if the outermost oxide layer 6 is cracked or peeled off. It is possible to suppress the progress of oxidation due to the peeling of the physical layer, thereby ensuring the durability of the second layer coating 3.

An example in which the thermal expansion coefficient of the second layer coating 3 is reduced by the addition of the oxide particles 4 will be described. FIG. 3 is data obtained by a linear expansion coefficient measuring apparatus (measurement specimen length 20 mm), and is an integer corresponding to the main composition of the base material and each layer coating, an oxide particle-containing Al—Ni alloy, and the linear expansion integer of alumina. It is a figure which shows comparison of these.
As seen in the figure, the thermal expansion coefficient of the 50 atm% Al—Ni alloy corresponding to the second layer film 3 is large compared to the thermal expansion coefficient of alumina which is a constituent material of the outermost oxide layer 6. In particular, the difference is large at a high temperature range of 1300 ° C. or higher. This is considered to be the main cause of the oxide layer 6 peeling off.

  On the other hand, it is known that when alumina particles are added to a 50Al—Ni alloy, the coefficient of thermal expansion gradually decreases, and particularly when about 50% of alumina particles are added, the difference in coefficient of thermal expansion from alumina is significantly reduced. This is because the additive particles (alumina) itself has the same thermal expansion coefficient as that of the oxide layer constituent material (alumina), and the additive particles act as a kind of cushion to suppress the thermal expansion. I guess that. As a result, it is expected that the oxide layer 6 is difficult to peel off from the second layer film 3.

  The composition of the alloy layer of the second layer coating 3 is roughly divided into a case where the oxide forming element is Al (hereinafter referred to as Al-based) and a case where it is Si (hereinafter referred to as Si-based). The Al-based alloy layer contains at least Al, and contains one or more of Cr and Ni. Al is an element necessary for forming a dense oxide film on the surface, and at least one of Cr and Ni forms a stable phase (alloy or intermetallic compound) at high temperature with Al. It is a necessary element to do. On the other hand, the Si-based alloy layer includes at least Si and includes one or more of Mo, W, and Nb. In this case, Si is an oxide film forming element, and at least one of Mo, W, and Nb is an element that forms a stable phase (alloy or intermetallic compound) with Si at a high temperature.

  As the fiber to be dispersed in the alloy layer of the second layer coating 3, one or more of oxide ceramic fibers or whiskers can be used depending on the heat resistant temperature. As the oxide-based ceramics, alumina-based, high-silica-based, alumina-silica-based, silicate (glass) -based, zirconia-based fibers, and fibers of various metal oxides that can be made into fibers can be used.

In the present invention, it is preferable to use short fibers or whiskers having an average aspect ratio of 2 to 1,000 as the fibers. This is because it is extremely difficult to disperse long fibers in a thin film, and short fibers are easier to disperse uniformly in the second layer film.
As will be described later, since the raw material powder of the alloy layer and the fiber are mixed and sintered, the diameter of the reinforcing fiber is preferably about the same as or smaller than the particle size of the raw material powder. Since any of the above-mentioned fibers can obtain ultrafine fibers of several to several tens of microns, fibers having a particle size almost the same as that of the raw material powder can be used. Moreover, since the diameter of a whisker is usually about several microns or less, it is particularly suitable in the present invention.
As the whisker, for example, non-metallic whiskers such as alumina, potassium titanate, aluminum borate, magnesia, and zinc oxide can be used.

On the other hand, as the oxide particles dispersed in the alloy layer of the second layer coating 3, one or more of the oxide ceramic powders can be used. As oxide ceramics, powders of various metal oxides of alumina, high silica, alumina-silica, silicate (glass), and zirconia can be used.
In the present invention, the oxide powder is preferably a particle having an average particle diameter of 1 to 50 μm. The reason is that, as will be described later, since the raw material powder of the alloy layer and the oxide powder are mixed and sintered, the diameter of the oxide powder may be equal to or larger than the particle diameter of the raw material powder. This is because it is preferable for facilitating sintering.

Furthermore, the content rate of the oxide fiber in the second layer coating is 3 to 15% by volume, the content rate of the oxide particle is 5 to 40% by volume, and the sum of the content rate of the oxide fiber and the oxide particle is 20 to 20%. It is preferably 50% by volume. When the content ratio of the oxide fiber and the oxide particle is less than the above range, the combined effect of suppressing peeling of the oxide film, which is strengthened by the fiber and reduced in the difference in thermal expansion coefficient, is insufficient. Moreover, when the content rate of an oxide fiber and an oxide particle exceeds said range, it will become difficult to produce | generate a precise | minute film | membrane at the time of sintering, and in connection with this, oxidation will be accelerated | stimulated and it will have an adverse effect. These oxide fibers and particles can be used in appropriate combination depending on the heat resistant temperature.
Further, the atomic ratio of the oxide-forming element (Al or Si) in the alloy layer of the second layer film is not particularly limited, but is preferably 0.05 to 0.95.

Next, the constituent material and function of the first layer coating 2 are the same as in the case of Patent Document 3, and the preferred composition is different between Al-based and Si-based. The Al-based, with the general formula _{Re 1-ab M a R b} ( where, Re is rhenium, M is Cr, 1 or two or more elements selected from the group consisting of Ni and Al, R is Nb, 1 or 2 or more elements selected from the group consisting of Mo, W, Hf, Zr and C, and a and b are atomic ratios of M and R, respectively). preferable.
On the other hand, in the Si-based, in the general formula _{Re 1-de T d R e} ( wherein, T 1 or more elements of the Cr and Si, R is the group consisting of Ni, Mo, W, Hf, from Zr and C It is preferable that the composition is represented by one or more elements selected from the group consisting of d and e each having an atomic ratio of T and R).

In both Al and Si systems, Re is an element that plays a major role in preventing diffusion. The reason why the first layer alloy film is composed of a ternary or higher composition is that not only the elements in the alloy layer of the second layer film but also the elements in the base material are included in the first layer film in advance. In addition, diffusion is prevented by keeping the chemical potential in each phase equal for each component. Thereby, decomposition | disassembly and quality change of an oxidation-resistant coating can be suppressed, and durability of a film | membrane can be improved significantly.
Further, the elements M and R in the Al system and the elements T and R in the Si system are preferably elements that form a stable phase with Re at a high temperature. For example, a Re—Cr—Ni sigma phase In addition, an intermetallic compound phase such as a Re- (Nb, Mo, W) -based sigma phase or chi-phase is preferable.

  The coating method of the present invention is for forming an oxidation resistant coating structure as described above. Hereinafter, a case where a two-layered film as shown in FIG. 1 is formed will be described. First, the method of forming the first layer alloy film on the substrate surface may be any of various methods that have been put to practical use. For example, any of PVD method, CVD method, thermal spraying method, electrolytic coating method, diffusion injection method and the like may be used, or a combination thereof may be used.

  On the other hand, the technology of forming a second layer composite coating (a coating in which oxide particles and fibers are dispersed in an alloy layer) on the surface of a base material has not been very practical and has been established. It's hard to say. As a result of various studies, the present inventors prepared a coating material in which a predetermined component of metal or alloy powder, oxide powder and fiber are dispersed in a binder, and applied this to the substrate surface to form a coating film. Then, it was found that a method of heat-treating the coating film and sintering the metal or alloy powder was appropriate. Thereby, oxide particle | grains and a fiber solidify with a metal powder and can form a membrane | film | coat with sufficient intensity | strength. Of course, most of the binder component decomposes and volatilizes during the heat treatment. The binder is not particularly limited, but an organic binder can be used and may be appropriately selected in consideration of viscosity, adhesion to a substrate, drying property, etc. so that a coating film can be easily formed. .

  In the heat treatment of the coating film, an intermetallic compound can be synthesized by a combustion synthesis method. In the combustion synthesis method, two or more kinds of metal powders are heated and reacted, and the reaction heat is used to synthesize an intermetallic compound and produce a sintered body. There is also a report example to be applied to formation (Non-Patent Document 1). As shown in the examples described later, when the second layer film is an Al-based film, a Ni-Al-based intermetallic compound is synthesized from a metal powder of Al and Ni by a combustion synthesis method. Can also be used (heated from the outside if necessary) to advance the sintering of the metal powder particles, oxide particles and fibers.

An Nb-based alloy having a composition of Nb-5Mo-5W-Cr (mol%) was melted in an Ar atmosphere by an arc melting method. As the raw material, 99.99% powder or granular material was used for Nb and 99.9% for Mo, W, and Cr. The melted alloy was heated in a 1 atm Ar stream at 1800 ° C. for 24 hours to obtain a homogenization heat treatment. Thereafter, a test piece base material of 20 × 20 × 2 (thickness) mm was cut out and subjected to a coating treatment.
To form the first layer film, first, metal Re having a thickness of 5 μm was electrodeposited from a molten chloride bath containing rhenium chloride on the surface of the base material. Subsequently, it was embedded in an alumina crucible together with the ferrochrome powder, and Cr vapor diffusion treatment was carried out by holding at 1300 ° C. in a vacuum of 1 × 10 ⁻³ Pa for 10 hours to obtain a first layer alloy film having a thickness of about 10 μm.

Next, about 1 to 20% by volume of Al ₂ O ₃ short fibers and about 3 to 50% by volume of Al ₂ O ₃ powder particles (average particle diameter φ15 μm) are represented in the same mol% of Al and Ni pure metal powder. After adding a combination of 1 and uniformly dispersing using a mill, 10 wt% of paraffin added as an organic binder and mixing the mixture is heated to about 100 ° C and applied to the base material of the test piece. did.
In order to remove organic matter, the sample was held at 550 ° C. in hydrogen for 1 hour after hydrostatic pressing and alloyed and sintered to 50Al—Ni (mol%) intermetallic compound by a combustion sintering reaction. Degreasing was carried out at 10 ° C. for 10 hours. Next, this sample is hot-pressed with alumina powder at 1200 ° C., 15 min, 30 MPa to form a second layer oxidation-resistant alloy film of 50 Al—Ni (mol%) alloy containing fibers and particles having a thickness of about 100 μm. And the coating process was completed.

As a comparison material, Ni electroplating was performed on a test piece having a first layer Re—Cr alloy film having a thickness of about 10 μm as described above, and then embedded in an alumina crucible together with Fe—Al alloy powder. Second layer oxidation-resistant alloy of 50Al-Ni (mol%) alloy that does not contain fibers and particles and is about 100 μm thick by holding Al vapor diffusion treatment at 1000 ° C. for 20 hours in a vacuum of 10 ⁻³ Pa The film was coated.

The test piece of the present invention (the material of the present invention) and the comparative material subjected to the coating treatment according to the above steps were heated in a static atmosphere at 1500 ° C. for 100 hours to be oxidized. As a result, as shown in FIG. 2, the first material alloy film 2 and the second layer oxidation-resistant alloy film 3 on the surface of the base material are laminated together and the oxide layer (Al, A two-batter base heat-resistant member in which O) 6 was formed was obtained. Here, in the material of the present invention, along with the preferential oxidation of Al in the second layer oxidation resistant alloy film, a part of the oxidation resistant alloy layer in the Al ₂ O ₃ oxide film formed on the surface has a short Al ₂ O ₃ short. Fiber was included.

The fiber and particle content of the second layer oxidation resistant alloy film after film formation of the present invention and the comparative material, and the peeling ratio / oxidation of the surface oxide layer (almost all composed of Al ₂ O ₃ ) after the oxidation treatment The increase is shown in Table 1. In the table, those in which the fiber and particle content is within the preferred range are indicated as “present invention” in the remarks column, and those outside the preferred range are indicated as “comparative examples”.
Here, the separation ratio is represented by the following definition.
Peeling ratio = (peeled Al ₂ O ₃ content ÷ total Al ₂ O ₃ content) x 100

From the above results, in the case of containing fibers in the second layer, even if the content of Al ₂ O ₃ short fibers is only 3% by volume, if 20% by volume of Al ₂ O ₃ particles are contained together, It can be seen that after 100 hours of heating in a static atmosphere, the peeling ratio, that is, the adhesion, was remarkably improved.
In the example of the prior application, when the oxidation temperature was 1350 ° C., the separation rate was significantly improved by adding only 3% Al ₂ O ₃ short fibers (without Al ₂ O ₃ particles), but the oxidation temperature was 1500 ° C. In the case, only the Al ₂ O ₃ short fibers had a small peeling improvement effect. In preliminary examination, when only particles were added without fibers, the peeling rate was high at 1500 ° C. This is presumed to be due to the absence of the effect of preventing the fibers from being wedged. It has been known that the peeling rate can be significantly improved even at 1500 ° C. by adding a composite of Al ₂ O ₃ particles and Al ₂ O ₃ short fibers.

On the other hand, even when the content of Al ₂ O ₃ short fibers was 3% by volume, when 50% by volume of Al ₂ O ₃ particles were contained together, the peeling ratio was small and good, but oxidation proceeded very much. . This is presumed to be due to the fact that the packing density decreased due to excessive oxide content, and rather promoted oxidation. As shown in Table 1, it was found that the oxide fiber and particles can be combined with appropriate amounts to obtain an effect of improving the adhesion of the oxide film.

It is a cross-sectional schematic diagram which shows the example of the oxidation-resistant coating structure of the heat-resistant alloy of this invention. It is a cross-sectional schematic diagram which shows the change of the film | membrane after exposing the heat-resistant alloy of this invention to high temperature air | atmosphere. It is a figure which shows the comparison of the linear expansion coefficient of the alloy which consists of a main composition of a base material and each layer membrane | film | coat, particle | grain addition 50Al-Ni, and an alumina.

Explanation of symbols

1 Base material 2 First layer coating (diffusion prevention layer)
3 Second layer coating (antioxidation layer)
4 Oxide particle 5 Oxide fiber 6 Oxide layer

Claims (7)

  An oxidation-resistant coating structure for a heat-resistant alloy, wherein an oxidation-resistant film in which oxide fibers and particles are dispersed in an alloy layer containing at least Al or Si is formed on the surface of the base material of the heat-resistant alloy.   A first layer alloy film for preventing diffusion is formed on the surface of the base material of the heat-resistant alloy, and oxide fibers and particles are dispersed on the surface of the alloy layer containing at least Al or Si. An oxidation resistant coating structure of a heat resistant alloy, characterized in that a two-layered film is formed. The heat resistant alloy is a niobium-based alloy, an alloy film of the first layer, in the general formula _{Re 1-ab M a R b} ( wherein, M represents Cr, Ni, 1 or more elements of Al, R is One or more elements of Nb, Mo, W, Hf, and C, a and b are each an atomic ratio of M and R), and the second layer coating is 3. The oxidation resistant coating structure according to claim 2, wherein oxide fibers and particles are dispersed in an alloy layer containing at least Al and at least one of Cr and Ni. The heat-resistant alloy is a niobium-based alloy, and the alloy film of the first layer has a general formula Re _1-de T _d R _e (where T is one or more elements of Cr and Si, and R is Nb And at least one element selected from the group consisting of Mo, W, Hf, Zr and C, wherein d and e are atomic ratios of T and R, respectively, and 3. The oxidation-resistant coating according to claim 2, wherein the second layer coating is obtained by dispersing oxide fibers and particles in an alloy layer containing at least Si and at least one of Mo, W, and Nb. Construction.   The fibers are one or more selected from the group consisting of oxide ceramic fibers or whiskers, and are composed of short fibers or whiskers having an average aspect ratio of 2 to 1,000, and the particles are oxidized. 1 type or 2 types or more selected from the group consisting of particles of physical ceramics, consisting of particles having an average particle size of 1 to 50 μm, and a content ratio of oxide fibers in the second layer coating of 3 to 15 5. The oxidation resistance according to claim 1, wherein the volume percentage is 5 to 40 volume%, and the sum of the percentage content of oxide fibers and oxide particles is 20 to 50 volume%. Covering structure.   A method for forming an oxidation-resistant coating structure according to claim 1, wherein a coating material is obtained by dispersing metal powder containing at least Al or Si and oxide fibers and particles in a binder on the surface of a base material of a heat-resistant alloy. A heat-resistant alloy coating method comprising forming a coating film, and then performing a heat treatment for sintering the metal powder in the coating film. A method for forming an oxidation resistant coating structure according to any one of claims 2 to 5, wherein an alloy film of the first layer is formed on a surface of a base material of a heat resistant alloy,
Further on the surface of the heat treatment, to form a coating film of paint and fibers and particles of oxide and metal powder containing at least Al or Si dispersed in a binder, and then to sinter the metal powder in the coating film A method for coating a heat-resistant alloy, characterized in that:

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