JP6649115B2 - Laminated structure - Google Patents

Description

  The present invention relates to a laminated structure having excellent heat resistance, and more particularly to a laminated structure provided in an engine of an aircraft or the like to provide a high-temperature component used in an atmosphere containing high-temperature oxygen, water vapor, and the like.

In the aviation industry, studies are being conducted to improve the heat resistance of high-temperature components such as high-pressure turbine members or to reduce the weight in order to improve fuel efficiency of engines and reduce carbon dioxide emissions. I have. This high-temperature component generally has a structure including a base made of a heat-resistant material and a protective film disposed on the surface thereof.
Conventionally, as a constituent material of a base (substrate) in a high-temperature component, a nickel-based superalloy or a silicon carbide fiber reinforced carbon steel having a lighter weight and excellent heat resistance and a large specific strength in a high temperature range has been used. Attention has been focused on silicon composite materials (hereinafter, referred to as “CMC (ceramic matrix composite)”). CMC is an SiO ₂ layer was formed in a high-temperature oxidizing atmosphere, the SiO ₂ layer acts as a protective film against further oxidation of the CMC. However, in a steam environment of 1100 ° C. or higher, such as a high-pressure turbine, the SiO ₂ layer reacts with the steam to form a volatile hydroxide. Deterioration becomes a problem. Therefore, an attempt has been made to form an environment-resistant coating (hereinafter, referred to as “EBC (Environmental Barrier Coating)”) on the surface of the CMC to suppress the oxidative deterioration and the thickness reduction of the member and to improve the durability. For example, the following techniques are known.

Patent Document 1 discloses a first layer containing silicon carbide and a second layer containing a rare earth silicate compound represented by the general formula RE ₂ Si ₂ O ₇ (RE: Y, Yb, Er, Dy). And a third ceramic layer containing silicon oxide and joining a first layer and a second layer.
Patent Document 2 discloses a ceramic in which the surface of a sintered SiC fiber composite is covered with a layer mainly composed of a rare earth oxide, and has a strength retention of 70% or more after heat treatment at 1700 ° C. for 100 hours in air. A composite material is disclosed.
Further, Patent Document 3 discloses that an intermediate layer made of a mixture of aluminosilicate-based crystallized glass and a rare earth silicate is provided on the surface of the base material based on a silicon carbide fiber-reinforced ceramic composite material. A laminated material in which a rare earth silicate layer is provided as a top coat is disclosed.

JP-A-11-12050 JP-A-2002-104892 JP 2008-308374 A

On the other hand, the present inventors have described a laminated structure in which mullite having excellent creep resistance and a thermal expansion coefficient relatively close to that of the composite material (CMC) is provided as an EBC for oxygen shielding on the surface of a base made of CMC. , Has been considered. In a practical environment, the chemical potential of oxygen (oxygen partial pressure equilibrating therewith) differs between the surface layer side of the EBC and the base material side, so that oxygen molecules are deposited on the mullite surface on the higher oxygen partial pressure side. After adsorption and dissociation, it diffuses as ionic ions in mullite to the side with a low oxygen partial pressure at the grain boundary. At the same time, the aluminum ions constituting the mullite diffuse from the low oxygen partial pressure side to the high oxygen partial pressure side. That is, oxygen molecules are transmitted through the grain boundaries of the mullite as oxygen ions and aluminum ions diffuse at the grain boundaries. In addition, aluminum ions move to the side where the oxygen partial pressure is high, and mullite decomposition products (such as silica) are unevenly distributed on the side where the oxygen partial pressure is low.
In addition, the SiO ₂ layer formed by the decomposition of mullite generates cristobalite, which is one of the SiO ₂ crystal phases, at a high temperature. Cristobalite undergoes a significant volume change (high to low temperature: 3.9 vol% shrinkage) accompanying the β → α transition (high to low temperature) at about 270 ° C., so that during the cooling process after the glass melt coating, around the cristobalite crystal particles Cracks were formed, and as a result, the adhesion to EBC was greatly reduced, and as a result, there was a problem that oxidation resistance could not be maintained.
An object of the present invention is to provide a laminated structure having a mullite layer on the surface of a base made of a heat-resistant base material and having excellent heat resistance and a stable overall layer structure including the mullite layer.

The present invention is described below.
1. A laminated structure formed on a surface of a base containing an inorganic compound, wherein the laminated structure comprises a layer (A) containing mullite and a layer (B) containing alumina sequentially.
2. 2. The laminated structure according to the above 1, wherein the inorganic compound contains at least one ceramic selected from silicon carbide, silicon nitride, and sialon.
3. 3. The laminated structure according to the above 2, wherein the base is made of a silicon carbide fiber reinforced ceramic composite material in which silicon carbide fibers are dispersed in a matrix made of the ceramic.

The laminated structure of the present invention has excellent heat resistance, and specifically, has a stable overall layer structure at a high temperature of 1100 ° C. or higher, preferably 1300 ° C. or higher (upper limit is about 1600 ° C.). Then, a material or a high-temperature component in which the layer (A) and the layer (B) are sequentially laminated on the surface of the base containing the inorganic compound is used in an atmosphere containing the above high temperature and containing oxygen, water vapor, and the like. In this case, the decomposition of mullite contained in the layer (A) located on the lower side of the oxygen partial pressure and the diffusion of aluminum ions toward the layer (B) or the formation of SiO ₂ crystals based on the mullite can be suppressed. Excellent in durability. Therefore, the laminated structure of the present invention is suitable as a component of a high-temperature component (such as a turbine component) disposed in an aircraft engine or the like. Further, it is possible to further improve the fuel efficiency by further increasing the high-pressure turbine inlet temperature and reducing the member cooling gas.

It is the schematic which shows the partial cross section of the laminated material provided with the laminated structure of this invention. It is the schematic which shows the heat processing apparatus used by [Example]. 6 is a cross-sectional image showing a single-layer structure after heat treatment in Comparative Example 1. 6 is an enlarged cross-sectional image showing a surface portion on a low oxygen partial pressure side in a single-layer structure after heat treatment in Comparative Example 1. 5 is a cross-sectional image showing a laminated structure after heat treatment in Example 1. 4 is an enlarged cross-sectional image showing a surface portion of a mullite layer (low oxygen partial pressure side) in a laminated structure after heat treatment in Example 1.

Hereinafter, the present invention will be described in detail.
The laminated structure of the present invention is a laminated structure formed on the surface of the base 11 containing an inorganic compound to give the laminated material 1 shown in FIG. 15 sequentially.

The material constituting the base is an inorganic compound. The inorganic compound is preferably a nitride, a carbide, a boride or the like, and these may be used alone or in combination of two or more.
As the nitride, silicon nitride, sialon, aluminum nitride, titanium nitride, zirconium nitride, tantalum nitride, or the like can be used.
As the carbide, silicon carbide, titanium carbide, zirconium carbide, tantalum carbide, or the like can be used.
As the boride, titanium boride, zirconium boride, tantalum boride, or the like can be used.
Among these, the material forming the base preferably includes silicon carbide, silicon nitride, or sialon.

When the base is made of a plurality of materials, a fiber reinforced ceramic in which carbon fibers or ceramic fibers are dispersed in a matrix containing the above oxide, nitride, carbide, boride and the like can be used. Examples of the ceramic fibers include alumina fibers, silicon carbide fibers, titanium carbonitride fibers, and boron carbide fibers. The content ratio of the carbon fibers or ceramic fibers contained in the matrix is not particularly limited, but from the viewpoint of mechanical strength, fracture toughness, etc., preferably 10 to 50% by volume, more preferably Is from 20 to 45% by volume.
As the fiber reinforced ceramic, a silicon carbide fiber reinforced ceramic in which silicon carbide fibers are dispersed in a matrix containing silicon carbide is preferable.

  The shape of the base is not particularly limited, and may be a fixed shape such as a plate shape, a tubular shape, a rod shape, various complicated three-dimensional shapes, or an irregular shape obtained by deforming them. Further, the shape of the base in the portion where the layer (A), the layer (B), and the like are formed may be either a flat surface or a curved surface.

The layer (A) is a layer containing mullite. _Mullite is preferably a compound represented by _{Al4 + 2xSi2-2xO10 -x} ( _{0.20≤x≤0.39} ), and a plurality of compounds in the range of _{0.20≤x≤0.39} . May be used. In the present invention, when an article (high-temperature component) having a laminated structure is used at a high temperature of 1100 ° C. or higher (upper limit is about 1600 ° C.) and in an atmosphere containing oxygen, water vapor, or the like, Al _{4 + 2x} Si _2-2x O _10-x (0.20 ≦ x), since the layer (B) located on the side with a low oxygen partial pressure has an excellent effect of suppressing the movement to the surface side (base side). ≦ 0.34), more preferably a compound represented by Al _{4 + 2x} Si _2-2x O _10-x (0.23 ≦ x ≦ 0.30). The layer (A) may include only mullite having a limited chemical composition, or may include two or more mullites having different chemical compositions. In the latter case, the plurality of mullites may be in a mixed state, or the distribution of the mullite having a specific chemical composition may be inclined from one end of the layer toward the other end. When mullite having a different chemical composition is inclined, the difference in thermal expansion coefficient between the mullite and the constituent material of the layer (B) (described later) becomes smaller, and the vaporization resistance on the surface of the base can be increased. It is preferable to increase the Al / Si ratio from the base side to the surface side of the layer (A).

  The layer (A) is preferably a layer composed of mullite alone, but may be a layer composed of mullite and another compound as long as the effects of the present invention are not impaired. Other compounds include alumina and the like. When the layer (A) contains another compound, the upper limit of the content ratio is preferably 30% by volume, more preferably 20% by volume, when the total of mullite and other compounds is 100% by volume. Preferably, it is 10% by volume.

  The thickness of the layer (A) is preferably from 5 to 800 μm, more preferably from 10 to 600 μm, since the effects of the present invention can be reliably obtained.

  The layer (B) is a layer containing alumina. Examples of the alumina include α-alumina, ρ-alumina, χ-alumina, κ-alumina, η-alumina, pseudo-γ-alumina, γ-alumina, δ-alumina, θ-alumina and the like. The alumina contained in the layer (B) may be only one kind of these, or may be two or more kinds. The layer (B) may contain only alumina having a limited crystal structure, or may contain two or more aluminas having different crystal structures. In the latter case, the plurality of aluminas may be in a mixed state, or the distribution of the specific alumina may be inclined from one end side to the other end side of the layer.

  The layer (B) is preferably a layer composed of only alumina, but may be a layer composed of alumina and another compound as long as the effects of the present invention are not impaired. When the layer (B) contains another compound, the upper limit of the content ratio is preferably 30% by volume, more preferably 20% by volume, when the total of alumina and other compounds is 100% by volume. Preferably, it is 10% by volume.

  The thickness of the layer (B) is preferably from 3 to 500 μm, more preferably from 4 to 400 μm. In order to more reliably obtain the effect of the present invention, the thickness of the layer (B) is 0.005 to 3.0 times the thickness of the layer (A), and is preferably. It is 0.008 times to 3.0 times.

  As described above, the layered structure of the present invention includes the layer (A) and the layer (B) in this order. However, if necessary, another layer is provided on the surface of the layer (B). You may.

The method for producing the laminated structure of the present invention is not particularly limited. Usually, it can be manufactured by sequentially forming a layer (A) and a layer (B) on the surface of an object (hereinafter, referred to as “base material”) constituting a base.
In the case of forming the layer (A) and the layer (B), it is preferable to form a film (layer) at a temperature of about 20 ° C to 1500 ° C in order to suppress deterioration of adjacent layers. Since a dense film (layer) can be formed, it is preferable to apply a film forming method such as aerosol deposition, electron beam physical vapor deposition, or laser chemical vapor deposition.

  After the formation of the layer (B), the surface of the layer (B) may be subjected to a smoothing treatment, a heat treatment of the laminate, or the like, if necessary. In the case of manufacturing a laminated structure including another layer, it is preferable to form the layer (A) and the layer (B) by a method that does not alter the components.

The laminated structure of the present invention has a high temperature of 1100 ° C. or more, for example, in an atmosphere containing oxygen, water vapor, and the like, the decomposition of mullite contained in the layer (A) and the aluminum ion layer (B) side based thereon. it is possible to diffuse or suppress the formation of SiO ₂ crystals to the, 1100 ° C. or higher, preferably higher temperature above 1300 ° C. (upper limit is about 1600 ° C.) heat resistance in the (oxidation resistance, steam resistance, resistance to It is suitable for applications where peelability is required.
For example, a high-temperature component such as a turbine component disposed in an aircraft engine or the like has a high temperature (for example, a component surface temperature is low) in a high-temperature gas environment containing steam (for example, a partial pressure of steam in a combustion gas is 101.3 kPa). (700 ° C. to 1400 ° C.) and a low temperature (for example, the component surface temperature is 50 ° C. or less). When a high-temperature component is formed using the laminated structure of the present invention, not only does the layer (A) or the layer (B) not peel off or the laminated structure becomes thinner, but also includes the entire layer (A). Is stable.

  The heat resistance, which is an effect of the present invention, can be confirmed using a laminated structure having a base and having a layer (A) and a layer (B). For example, aerosol deposition is performed on a mullite thin plate. It can be confirmed by forming an alumina layer by the method described above and performing an oxygen permeation test in a cross-sectional direction of the obtained laminated structure.

  Hereinafter, embodiments of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these embodiments.

Comparative Example 1
After mullite powder (trade name “KM-101” manufactured by Kyoritsu Materials Co., Ltd.) made of Al ₆ Si ₂ O _{13 is} subjected to press molding (pressure: 20 MPa), CIP molding (pressure: 250 MPa) is performed to obtain a plate-like material. Was. Next, heat treatment was performed at 1750 ° C. for 5 hours in an air atmosphere. Then, the obtained fired product was cut to obtain a mullite thin plate having a diameter of 11.5 mm and a thickness of 0.5 mm. In addition, both surfaces were mirror-finished.
Next, using this mullite thin plate (disc-shaped test piece), a heat treatment was performed under the following conditions of high temperature and oxygen partial pressure difference, and heat resistance was evaluated.

Using the heat treatment apparatus shown in FIG. 2, heat treatment was performed under different oxygen partial pressure conditions on one side and the other side of the mullite thin plate (disc-shaped test piece).
Specifically, a mullite thin plate (disc-shaped test piece) is arranged between two alumina protective tubes via a Pt seal ring, and a constant load is applied to the upper alumina protective tube by a weight. In addition, a surface pressure was applied between the mullite thin plate and the Pt seal ring. Subsequently, when it is labeled "Ar-1% H _2" on the lower side of FIG. 2, and, from where it is labeled "O _2" on the upper side, on both sides of the mullite thin plate, dry ice turned has been highly purified Ar-1% H ₂ gas and cooled to -72 ° C. by passing ethanol bath, was fed at a flow rate per minute 50 ml.
Next, while measuring the oxygen partial pressures of the upper chamber and the lower chamber of the mullite thin plate with an oxygen sensor (zirconia sensor), respectively, the electric furnace was driven to raise the temperature to 1620 ° C., and sealing was performed using a Pt seal ring. Was completed. Then, the temperature was lowered to 1300 ° C., and the O ₂ gas was continuously supplied only to the upper chamber, where P _O2 (lo) = 10 ⁻¹⁰ Pa on the lower surface side and P _O2 (hi) = 10 ⁵ Pa on the upper surface side. Heat treatment was performed at 1300 ° C. for 200 hours as each oxygen partial pressure difference.
After the heat treatment, the disc-shaped test piece was cut in a cross-sectional direction near its center, and a smooth surface by ion milling was observed with a scanning electron microscope. The results are shown in FIGS. FIG. 4 is an enlarged image of the cross section on the lower surface side of the mullite thin plate (disc-shaped test piece), and it can be seen that the mullite layer is decomposed at a depth of about 12 μm.

Example 1
After mullite powder (trade name “KM-101” manufactured by Kyoritsu Materials Co., Ltd.) made of Al ₆ Si ₂ O _{13 is} subjected to press molding (pressure: 20 MPa), CIP molding (pressure: 250 MPa) is performed to obtain a plate-like material. Was. Next, heat treatment was performed at 1750 ° C. for 5 hours in an air atmosphere. Then, the obtained fired product was cut to obtain a mullite thin plate having a diameter of 11.5 mm and a thickness of 0.5 mm. In addition, both surfaces were mirror-finished.
Next, alumina powder (trade name “TM-DAR” manufactured by Daimei Chemical Co., Ltd.) was continuously impinged on one side of the mullite thin plate by aerosol deposition to form an alumina layer having a thickness of 4 μm. Thus, a disk-shaped laminated structure was obtained. Using this laminated structure, a heat treatment was performed under the following conditions of high temperature and oxygen partial pressure difference, and the heat resistance of the laminated structure was evaluated.

Then, in the same manner as in Comparative Example 1, using the heat treatment apparatus shown in FIG. Were selected as P _O2 (lo) = 10 ⁻¹⁰ Pa and P _O2 (hi) = 10 ⁵ Pa, and heat treatment was performed on the laminated structure (disc-shaped test piece). The laminated structure (disc-shaped test piece) was arranged such that the alumina layer was on the upper surface side.
After the heat treatment, the disc-shaped test piece was cut in a cross-sectional direction near its center, and a smooth surface by ion milling was observed with a scanning electron microscope. The results are shown in FIGS. FIG. 6 is an enlarged image of the mullite layer side, and it can be seen that decomposition of the mullite layer is suppressed.

  The laminated structure of the present invention can be used for a moving blade component, a stationary blade component, or a shroud component of a high-pressure turbine portion in an aircraft engine or a power generation turbine used in a high-temperature gas environment containing steam, and further, a thruster and a combustion gas of a rocket engine. It is suitable for forming high temperature parts such as tubes.

  1: laminated material, 11: base, 13: layer (A), 15: layer (B)

Claims (3)

A layered structure formed on the surface of the base containing an inorganic compound, comprising a layer (A) containing mullite and a layer (B) containing alumina sequentially ,
The mullite is a compound represented by Al _{4 + 2x} Si _2-2x O _10-x (0.23 ≦ x ≦ 0.30),
The content of the mullite in the layer (A) is 90% by volume or more;
Layered structure, characterized in der Rukoto content above 90% by volume of the alumina in the layer (B).   The laminated structure according to claim 1, wherein the inorganic compound includes at least one type of ceramic selected from silicon carbide, silicon nitride, and sialon.   The laminated structure according to claim 2, wherein the base is made of a silicon carbide fiber reinforced ceramic composite material in which silicon carbide fibers are dispersed in a matrix made of the ceramic.