JP5411460B2 - Barrier performance evaluation method and barrier performance evaluation apparatus - Google Patents

Description

  The present invention may also be referred to as an environmental barrier coating film [hereinafter referred to as “EBC film” (Environmental Barrier Coating film). ] Barrier performance evaluation method and barrier performance evaluation apparatus. More specifically, the present invention provides a simple evaluation of the barrier performance of an EBC film using an alumina thin film forming material capable of suppressing the permeation of corrosive gas and forming an EBC film having excellent barrier performance. The present invention relates to a method and a simple structure evaluation apparatus used therefor.

Since the EBC film is used by being coated on the surface of a substrate having excellent heat resistance, it is exposed to a steep potential gradient of a corrosive gas such as oxygen and water vapor in an environment where the heat-resistant member is used. Under this potential gradient, in addition to the diffusion of corrosive species in the EBC film inward / outward, the constituent components of the film may cause phase separation and segregation. Therefore, the EBC film is required to suppress permeation of corrosive species caused by the potential gradient, phase separation in the film, segregation, etc., as well as stability against ultra-high temperature oxygen and water vapor. As this EBC film, a film is known in which a silicon carbide layer is formed on a surface of a carbon material that is a heat-resistant substrate via a silicon layer, and silicon dioxide and mullite are covered (for example, non-coated). (See Patent Document 1). A film in which the surface of a carbon material is coated with silicon carbide, YSix, and Y ₂ SiO ₅ in this order is also known (see, for example, Non-Patent Document 2).

On the other hand, other EBC films that are not silicon compounds have been studied. For example, Al ₂ O ₃ has excellent high-temperature stability, corrosion resistance, and the like, is used as a protective coating for various heat-resistant substrates, and is known to have sufficient protective performance. Furthermore, at a high temperature of 1600 ° C. or higher, the high oxygen partial pressure side has a p-type semiconductor and the low oxygen partial pressure side has an n-type semiconductor property at about 10 ⁻⁵ atm, and holes are formed in each oxygen partial pressure region. It is known to exhibit conductivity and electron conductivity.

Fritz et al., “Journal of European Ceramic Society” (UK), 1998, p. 2351-2364 Masayuki Kondo and three others, Journal of the Japan Institute of Metals, 1999, 63, p. 851-858

However, although the EBC films described in Non-Patent Documents 1 and 2 have a multilayer coating structure, sufficient oxidation resistance may not be exhibited because the oxide layer is not dense. The environment where the EBC film is placed is exposed to a wide range of oxygen potential gradients, with the oxygen partial pressure on the surface on the corrosive gas side being 1 atm and the oxygen partial pressure at the boundary between the EBC film and the substrate being ^10-15 atm level. The Therefore, when Al ₂ O ₃ is used alone as an EBC film, a plurality of mass transfer mechanisms are simultaneously involved, which may affect not only the oxygen permeation mechanism but also the stability of the material itself.

  The present invention has been made in view of the above-described conventional situation, and uses an alumina thin film forming material capable of suppressing the permeation of corrosive gas and forming an EBC film having excellent barrier performance. An object of the present invention is to provide a simple evaluation method for the barrier performance of an EBC film and a simple structure evaluation apparatus used therefor.

The present invention is as follows.
1. An alumina thin film forming material containing an alumina powder and a rare earth compound powder and used for forming an environmental barrier coating film, wherein the rare earth element is at least one of Sm, Eu, Tm and Lu. The amount of permeation of the corrosive gas in the thickness direction of the environmental barrier coating film when supplying a corrosive gas having different partial pressures to one side and the other side of the environmental barrier coating film using the alumina thin film forming material. In measurement, when the partial pressure is changed, the dependency of the permeation amount on the change is evaluated, and the permeation coefficient of the corrosive gas at each partial pressure is calculated. And evaluating the barrier performance of the environmental barrier coating film based on the correlation.
2. When the total of the alumina powder and the oxide-converted rare earth compound powder is 100 mol%, the rare earth compound powder is 0.1 to 0.5 mol%. The barrier performance evaluation method described in 1.
3. An alumina thin film forming material containing an alumina powder and a rare earth compound powder and used for forming an environmental barrier coating film, wherein the rare earth element is at least one of Sm, Eu, Tm and Lu. Corrosion gas supply means for supplying a corrosive gas having a different partial pressure to one side and the other side of the environmental barrier coating film using the alumina thin film forming material, and the corrosive gas in the thickness direction of the environmental barrier coating film. Measuring means for measuring the permeation amount; coefficient calculating means for determining a permeation coefficient of the corrosive gas based on the permeation amount at each partial pressure when the partial pressure is changed; and the partial pressure and the permeation amount An evaluation unit that evaluates the barrier performance of the environmental barrier coating film based on the correlation with the coefficient.
4). 2. The above rare earth compound powder is 0.1 to 0.5 mol% when the total of the alumina powder and the oxide-converted rare earth compound powder is 100 mol%. The barrier performance evaluation apparatus according to 1.

According to the barrier performance evaluation method of the present invention, although it is a simple method, it is possible to quantitatively evaluate the inward / outward diffusion behavior of corrosive species including oxygen. In addition, the correlation between the partial pressure of the corrosive gas and the permeation coefficient can be easily obtained. Based on this correlation, the barrier performance of the EBC film and the barrier performance such as the permeation amount of the corrosive gas can be accurately evaluated. it can.
According to the barrier performance evaluation apparatus of the present invention, although it is a simple apparatus, the correlation between the partial pressure of the corrosive gas and the permeability coefficient can be easily obtained, and the barrier performance of the EBC film can be accurately determined as described above. Can be evaluated.

The present invention will be described in detail below.
[1] Alumina thin film forming material
The material for forming an alumina thin film of the reference invention contains an alumina powder and a rare earth compound powder, and is used for forming an environmental barrier coating film.

  The material for forming an alumina thin film is a mixed powder containing alumina powder and rare earth element compound powder. The average particle size of the alumina powder is not particularly limited. For example, when the EBC film is formed by firing, if the alumina powder has a small average particle size, a denser sintered body is obtained by firing at a low temperature. Is preferable. However, if the average particle size of the alumina powder is too small, it is difficult to handle and the workability at the time of forming the EBC film may be inferior. On the other hand, if the average particle size is excessive, there is a problem that it cannot be densified unless it is fired at a high temperature, which is not preferable.

The rare earth compound powder is a powder of a compound having a rare earth element. Rare earth elements, Sm, Eu, Ri least 1 Tanedea of Tm and Lu, Lu is preferable. When the rare earth element is Lu, an EBC film in which the diffusion and permeation of corrosive species, phase separation in the film, segregation, and the like can be more sufficiently suppressed can be obtained. The rare earth compound powder is not particularly limited, and powders of rare earth oxides, carbonates, hydroxides and the like can be used, and are often used as oxide powders and carbonate powders.

  The content ratio of the alumina powder and the rare earth compound powder is preferably 0.05 to 1.0 mol% of the rare earth compound powder when the total of these is 100 mol%, More preferably, it is mol%, and particularly preferably 0.1 to 0.3 mol%. If the content of the rare earth compound powder is 0.05 to 1.0 mol%, particularly 0.1 to 0.5 mol%, the diffusion and permeation of corrosive species, phase separation in the film, segregation, etc. The EBC film can be sufficiently suppressed. Further, this rare earth compound powder acts as a sintering aid when an EBC film is formed by firing, and if it is a content within this range, it is sufficiently densified by firing and the alumina sintered body originally has Excellent strength and heat resistance are not impaired.

  Furthermore, when the alumina thin film forming material is 100% by mass, the total of the alumina powder and the rare earth compound powder is preferably 90 to 100% by mass, and particularly preferably 95 to 100% by mass. If the total of the alumina powder and the rare earth compound powder is 90% by mass or more, the excellent strength and heat resistance, etc. inherent in the sintered alumina body are not impaired, and the EBC has more excellent strength and heat resistance. A film can be formed. The other components other than the alumina powder and the rare earth compound powder contained in the material for forming an alumina thin film are not particularly limited as long as they do not impair the barrier performance of the EBC film. Examples of other components include various auxiliary agents such as a structure control agent such as magnesium oxide that also acts as a structure control agent in addition to the sintering auxiliary described later.

[2] Heat resistant member
The heat-resistant member of the reference invention includes a heat-resistant substrate and an environmental barrier coating film provided on the surface of the heat-resistant substrate using the alumina thin film forming material of the reference invention.

The heat-resistant substrate is not particularly limited, and various substrates that require the formation of an EBC film on the surface thereof are used because they are used at a high temperature. As the material of the heat-resistant substrate, a carbon / carbon composite material (a composite material obtained by reinforcing a graphite material with carbon fibers) and a heat-resistant metal can be used. Examples of the heat-resistant metal include Fe-based alloys such as stainless steel, nickel-based alloys, and chromium-based alloys. Examples of the stainless steel include ferritic stainless steel, martensitic stainless steel, and austenitic stainless steel. Examples of the nickel-based alloy include Inconel 600 (registered trademark), Inconel 718 (registered trademark), Incoloy 802 (registered trademark), and the like. Further, examples of the chromium-based alloy include Ducrloy CRF (94Cr5Fe1Y ₂ O ₃ ).

  The product using the heat-resistant substrate is not particularly limited, and examples thereof include (1) various plant relations, (2) transportation equipment relations, and (3) other facilities, equipment, and equipment. (1) Various plant relations include internal combustion engines, boilers (superheated organs, headers / main steam pipes, high-temperature high-pressure valves, etc.), steam turbines, gas turbines ( High temperature rotors, inner casings, steam valves, low pressure rotors, etc.), heat exchangers, reformers, piping, heat shields, heat insulating materials, fixed parts, etc. Etc. In addition, (2) Transportation equipment related to internal combustion engines, boilers (superheated organs, headers / main steam pipes, high-temperature and high-pressure valves) used in various vehicles such as automobiles and railway vehicles, ships, aircraft, space equipment, etc. Etc.), steam turbine, gas turbine (high temperature rotor, inner casing, steam valve, low pressure rotor, etc.), heat exchanger, reformer, piping, heat shield, heat insulating material, fixed parts, etc. Examples include parts and parts used at high temperatures. In addition, (3) Other facilities, equipment, and equipment include internal combustion engines and boilers (superheated organs, headers, etc.) used in various facilities, equipment, and equipment in fields other than (1) and (2) above. Main steam pipes, high-temperature high-pressure valves, etc.), steam turbines, gas turbines (high-temperature rotors, inner casings, steam valves, low-pressure rotors, etc.), heat exchangers, reformers, piping, heat shields, heat insulating materials, fixed parts Examples include parts and parts used at a high temperature of 800 ° C. or higher.

  A method for providing an EBC film on the surface of the heat-resistant substrate using the material for forming an alumina thin film is not particularly limited. This method includes (1) physical vapor deposition such as thermal vapor deposition, electron beam vapor deposition, ion beam vapor deposition, sputtering, reactive sputtering, and (2) thermal chemical vapor deposition, plasma chemical vapor deposition, electron cyclotron resonance source plasma chemical vapor deposition, etc. Examples thereof include chemical vapor deposition, (3) thermal spraying such as plasma spraying, and (4) film formation using a slurry-like alumina thin film forming material such as sol-gel, dip coating and spray coating.

  Among the above-mentioned various methods, the physical vapor deposition method and the thermal spraying method are methods in which the alumina thin film forming material is linearly emitted toward the heat-resistant base material. It is not easy to efficiently form a uniform EBC film having a uniform thickness on the surface of a component. In addition, chemical vapor deposition can form an EBC film having a predetermined thickness and a high density even for various parts and parts having complicated shapes, but it is expensive and the film forming speed is also high. Not necessarily big.

Furthermore, the sol-gel method can form a high-density EBC film at a low cost and efficiently even for various parts and parts having complicated shapes, but a film having a sufficient thickness is formed. It's not easy. In addition, in the dip coating method and the spray coating method, an EBC film can be efficiently formed at low cost even for various parts having complicated shapes, but the adhesion to the heat resistant substrate is not sufficient. Sometimes. Furthermore, the film forming method using the slurry-like material for forming an alumina thin film usually has a somewhat complicated operation and process.
As described above, since each method has its own characteristics, it is preferable to select them appropriately in consideration of them.

  The film forming method using the slurry-like material for forming an alumina thin film can efficiently form an EBC film on the surface of various parts having complicated shapes at low cost. In this method, the EBC film is formed by drying the coating film and then baking it. Hereinafter, this method will be described.

  The slurry-like material for forming an alumina thin film is, for example, blended with a predetermined amount of alumina powder, rare earth compound powder, organic solvent, etc., and then wet-mixed with a ball mill or the like, and then an organic binder, plasticizer, organic solvent, etc. It can mix | blend and it can prepare by further wet-mixing after that. Further, it can be prepared by blending alumina powder, rare earth compound powder, organic binder, plasticizer, organic solvent and the like and then wet-mixing with a ball mill or the like.

  As an organic binder, a plasticizer, and an organic solvent, what is generally used in the ceramic slurry which has an alumina powder as a main component can be used without being specifically limited. Examples of the organic binder include butyral resins, acrylic resins, celluloses such as ethyl cellulose and hydroxyethyl cellulose. Examples of the plasticizer include phthalic acid esters such as dibutyl phthalate and dibutyl adipate. Examples of the organic solvent include alcohols such as butyl carbitol, terpineol and isopropyl alcohol; ketones such as methyl ethyl ketone and acetone; aromatic solvents such as toluene and xylene; and toluene and methyl ethyl ketone are used. Many. Only one organic binder, plasticizer, or organic solvent may be used, or two or more organic binders may be used in combination.

  The slurry-like alumina thin film forming material prepared as described above is applied to the surface of the heat-resistant substrate to form a coating film, and then the coating film is dried to remove the organic solvent, An EBC film can be formed by firing. This firing is performed by holding the dried coating film at a predetermined temperature for a required time. The firing temperature can be set according to the average particle diameter of the alumina powder, the type and blending amount of the rare earth compound powder, and the like. This firing is usually performed after so-called degreasing, in which the coating film is heated at a predetermined temperature lower than the firing temperature to remove the organic binder. In this case, after degreasing, the temperature may be raised to the firing temperature without lowering the temperature as it is, or after degreasing, the temperature may be once lowered, for example, lowered to room temperature (25 to 35 ° C.), and then You may bake.

  The firing atmosphere is not particularly limited, and may be any of an oxidizing atmosphere such as an air atmosphere, an inert atmosphere such as an inert gas atmosphere such as a nitrogen gas atmosphere and an argon gas atmosphere, and a reducing atmosphere containing hydrogen gas. Further, it may be a dry atmosphere or a humidified atmosphere. The firing atmosphere is preferably a humidified reducing atmosphere, and this firing atmosphere is advantageous for the decomposition of the organic binder and can be densified at a lower temperature. Furthermore, the alumina sintered body can be fired in an air atmosphere, and the air atmosphere is advantageous in terms of production cost and the like.

In order to sinter the alumina powder, a sintering aid powder is usually blended. In the material for forming an alumina thin film of the reference invention, when the rare earth compound powder contained acts as a sintering aid and can be sufficiently densified only with this rare earth compound powder, other sintering aids are used. do not need. On the other hand, when sufficient densification cannot be achieved with the rare earth compound powder alone, an appropriate amount of a sintering aid of a kind that does not impair the barrier performance as the EBC film can be blended. As the sintering aid, a sintering aid generally used for firing alumina powder can be used without any particular limitation.

  As the sintering aid, powders of Si, Ti, Zr, and oxides, carbonates, hydroxides, etc. of Group 2 elements in the periodic table such as Mg, Sr, Ca and Ba can be used. . Of these, Si, Ti, Zr and the like are often used as oxide powders. In addition, group 2 elements in the periodic table are often used as oxide powders and carbonate powders. These sintering aids may be used alone or in combination of two or more. By using two or more kinds in combination, it can be densified at a lower temperature.

  When the sintering powder other than the rare earth compound powder is mixed with the alumina powder, the content ratio of the other sintering auxiliary powder is 100 mol% of the total of the alumina powder, the rare earth compound powder and the sintering auxiliary powder. In this case, it is preferably 3 mol% or less, particularly preferably 1 mol% or less. If the content ratio is within this range, the EBC is sufficiently densified by firing and does not impair the excellent strength, heat resistance, etc. inherent in the alumina sintered body, and has more excellent strength, heat resistance, etc. A film can be formed.

Even when the EBC film is formed by any method, it is preferable that the EBC film is sufficiently densified in order to obtain an EBC film having excellent strength and heat resistance. When the relative density is used as an index for densification, the relative density is preferably 95% or more, particularly 98% or more, and more preferably 99.5% or more. For example, when an EBC film is formed by firing, the relative density depends on the average particle diameter of the alumina powder contained in the material for forming an alumina thin film, the kind and blending amount of the rare earth compound powder, the firing temperature, etc. It can be adjusted to a preferred range.
The relative density can be calculated by dividing the bulk density measured by the Archimedes method using pure water as a solvent by the theoretical density.

[3] Barrier performance evaluation method The barrier performance evaluation method of the present invention is a method in the thickness direction of an environmental barrier coating film when corrosive gases having different partial pressures are supplied to one side and the other side of the environmental barrier coating film. In the measurement of the permeation amount of corrosive gas, the dependency of the permeation amount on the change when the partial pressure is changed is evaluated, and the permeation coefficient of the corrosive gas at each partial pressure is calculated. The correlation is obtained, and the barrier performance of the environmental barrier coating film is evaluated based on the correlation.

In the barrier performance evaluation method described above, a test piece is prepared using an alumina thin film forming material, and corrosive gases having different partial pressures are supplied to one side and the other side of the test piece. This corrosive gas is, for example, a gas that oxidizes this member when the heat-resistant member is used at a high temperature, and examples thereof include oxygen gas and water vapor.
In the low corrosion gas partial pressure region where alumina behaves as an n-type semiconductor, an inert gas such as Ar gas is supplied to the high partial pressure side, and an inert gas and a small amount of hydrogen gas are supplied to the low partial pressure side. Although a mixed gas is supplied, since a trace amount of corrosive gas is contained in both the inert gas and the mixed gas, it is expressed as “supply corrosive gas having different partial pressures”.

Then, due to the difference in partial pressure, the corrosive gas permeates from the high partial pressure side to the low partial pressure side, and this permeation amount is measured by a gas sensor or the like suitable for each corrosive gas. Further, based on the partial pressure at the time when the partial pressure of the corrosive gas reaches equilibrium on the low partial pressure side, the permeability coefficient is calculated according to the following formula (1).
PL (transmission coefficient) = C _p · Q · L / V _st · S (1)
(C _p ; concentration of permeated corrosive gas, Q: flow rate of corrosive gas, V _st ; ideal gas molar volume, S: area of specimen, L: thickness of specimen)

  Further, when the partial pressure of the corrosive gas is changed by changing the gas flow rate or the like, the above formula is obtained for each equilibrium partial pressure based on the partial pressure at the time when the partial pressure of the corrosive gas reaches equilibrium on the low partial pressure side. Each transmission coefficient is calculated according to (1). In this way, the correlation between the equilibrium partial pressure and the permeation coefficient is obtained, and a log-log graph with the horizontal axis of the equilibrium partial pressure and the vertical axis of the permeation coefficient is created. Evaluation is made, the permeation mechanism of the corrosive gas is estimated by the slope of the obtained straight line, and the barrier performance of the EBC film is evaluated by the absolute value of the permeation coefficient.

[4] Barrier performance evaluation apparatus The barrier performance evaluation apparatus of the present invention includes a corrosive gas supply means for supplying corrosive gases having different partial pressures to one side and the other side of the environmental barrier coating film, and the thickness of the environmental barrier coating film. Measuring means for measuring the permeation amount of the corrosive gas in the vertical direction, coefficient calculating means for obtaining a permeation coefficient of the corrosive gas based on the permeation amount at each partial pressure when the partial pressure is changed, and partial pressure and permeation Evaluation means for evaluating the barrier performance of the environmental barrier coating film based on the correlation with the coefficient.

  The barrier performance evaluation apparatus is an example of an evaluation apparatus used in the barrier performance evaluation method. The corrosive gas supply means provided in the apparatus is not particularly limited as long as the corrosive gas can be supplied at a constant flow rate. For example, various constant flow pumps can be used. The measuring means is not particularly limited, and an appropriate measuring instrument can be used depending on the type of corrosive gas. Examples of the measuring instrument include an oxygen gas sensor such as an oxygen sensor using a solid electrolyte such as zirconia having oxygen conductivity when the corrosive gas is oxygen gas, and when the corrosive gas is water vapor, Examples include a water vapor sensor and a dew point meter using a solid electrolyte body having conductivity.

  Further, as the coefficient calculating means, as described above, there is a means for calculating a permeation coefficient according to the equation (1) based on the concentration of the permeated corrosive gas. As the evaluation means, as described above, there is a means for evaluating by the slope of a straight line in a log-log graph with the equilibrium partial pressure as the horizontal axis and the transmission coefficient as the vertical axis.

Hereinafter, the present invention will be specifically described by way of examples.
Using a test piece produced using Al ₂ O ₃ and a test piece produced using Al ₂ O ₃ / Lu ₂ O ₃ , the effect of rare earth elements was confirmed using oxygen gas as the corrosive gas. did.
[1] Manufacture of test specimens Using Al ₂ O ₃ powder (manufactured by Daimei Chemical Co., Ltd., trade name “TMDAR, purity 99.99% or more) as a starting material, press molding at a pressure of 20 MPa, then CIP molding at a pressure of 600 MPa Then, it was fired in an air atmosphere at a temperature of 1500 ° C. Thereafter, it was cut to produce a test piece having a diameter of 23.5 mm and a thickness of 0.25 mm.

As _for the Al _{2 O 3 -Lu 2} O 3 based test piece, _Al 2 _{O 3} powder (manufactured by Taimei Chemicals Co., Ltd., trade name "TMDAR, purity 99.99%), nitrate lutetium hydrate [Lu (NO) ₃ × H ₂ O, manufactured by Sigma-Aldrich, purity 99.999% or higher] is a predetermined amount (Al ₂ O ₃ powder and the total of the Lu compound powder converted to Lu ₂ O ₃ is 100 mol%. In this case, the compounding amounts were such that the Lu compound powder was 0.05 mol% and 0.20 mol%.) Wet mixing, then press molding at a pressure of 20 MPa, then CIP molding at a pressure of 600 MPa, Thereafter, it was baked in an air atmosphere at a temperature of 1500 ° C. Next, cutting was performed to produce a test piece having a diameter of 23.5 mm and a thickness of 0.25 mm. Well, both sides Both had a mirror finish.

[2] Evaluation and results of oxygen permeation characteristics The oxygen permeation characteristics under low oxygen partial pressure, in which Al ₂ O ₃ has properties as an n-type semiconductor, were evaluated. That is, the evaluation was performed under a low corrosive gas partial pressure in which the partial pressure of oxygen gas was lower than 10 ⁻⁵ atm.
A gas permeability coefficient measuring apparatus 100 (see FIG. 1, each gas flows in the direction of the arrow) was used. Specifically, the test piece 3 is disposed between the two alumina protective tubes via the Pt seal rings 21 and 22, a constant load is applied to the upper alumina protective tube 11 with a weight, and the test piece 3 A surface pressure was applied between the Pt seal rings 21 and 22. Thereafter, high purity Ar gas was supplied to both sides of the test piece 3 at a flow rate of 100 cc / min. Here, in order to prevent the influence of gas leakage between the Pt seal rings 21 and 22 and the test piece 3, an alumina protective tube (outer alumina protective tube 13) is further arranged outside the upper and lower alumina protective tubes 11 and 12. The high purity Ar gas was supplied between the outer and inner protective tubes at the same flow rate. Moreover, high purity Ar gas passes through the Ar gas supply pipe 4 through an ethanol bath (cooling bath 5) filled with dry ice and is cooled to −72 ° C., so that Ar gas to be supplied is an impurity in the supplied Ar gas. The amount of water vapor contained was reduced.

  Thereafter, while the oxygen partial pressures in the upper and lower chambers are measured by oxygen sensors (zirconia sensors) 61 and 62, respectively, the temperature is raised to 1600 to 1700 ° C. by the electric furnace 8 to complete the seal by the Pt seal rings 21 and 22. Then, the temperature was lowered to the measured temperature. The oxygen partial pressure was measured with the oxygen sensors 61 and 62 held at 700 ° C. Thereafter, when the output of each sensor became constant, the equilibrium oxygen partial pressure in the upper and lower chambers was measured and used as a background value.

Next, the supply gas of the upper chamber is a low oxygen partial pressure gas (Ar gas containing 0.01 to 1% by volume of H ₂ gas, and the oxygen partial pressure is higher than that of the high purity Ar gas supplied to the lower chamber. (The amount of H ₂ gas is measured by gas chromatography 7.) The sample was supplied at a flow rate of 100 cc / min, and the change in oxygen partial pressure in the upper and lower chambers was monitored. And when the output of each sensor becomes constant, the equilibrium oxygen partial pressure of the upper chamber is measured, and from the difference from the background value, the permeation coefficient PL related to oxygen gas is calculated based on the equation (1). Calculated.

Thereafter, the flow rate of the low oxygen partial pressure gas supplied to the upper chamber is changed, the equilibrium oxygen partial pressure of the upper chamber at each flow rate is measured, and from the difference from the background value, based on the formula (1), The permeation coefficient PL at each oxygen partial pressure was calculated. According to the log-log graph of FIG. 2 showing the correlation between the equilibrium oxygen partial pressure and the permeation coefficient PL, in the case of Al ₂ O ₃ alone, 0.05 mol% and 0.20 mol% of Lu ₂ O _3. In both cases, the equilibrium oxygen partial pressure and the permeability coefficient PL have a linear relationship, and the slope thereof is constant at -1/6.

As described above, since the slope of the straight line is the same between the case of Al ₂ O _{3 and} the case of containing Lu ₂ O _{3, the} case of only Al ₂ O ₃ and the case of Lu It is presumed that the oxygen gas permeation mechanism is the same when ₂ O ₃ is contained. That is, in any case, under a low oxygen partial pressure of 1600 ° C. or higher and 1 × 10 ⁻⁵ atm or lower, oxygen deficiency occurs, oxygen vacancies are formed, and electron conductivity through the oxygen vacancies is reduced. Inferred to have. Further, when 0.05 mol% of Lu ₂ O ₃ is contained as compared with the case of only Al ₂ O ₃ , there is no great difference in the oxygen transmission coefficient, and the large effect by containing the rare earth oxide is I can't see it. On the other hand, when 0.20 mol% of Lu ₂ O ₃ is contained, the oxygen permeation coefficient is greatly reduced, the permeation of corrosive gas is suppressed, and sufficient effects are achieved by containing rare earth oxides. I understand that

In addition, for each test piece when only Al ₂ O ₃ is contained and when 0.20 mol% of Lu ₂ O ₃ is contained, the above-described gas permeability coefficient measuring apparatus is used to raise the lower chamber. Oxygen partial pressure side (using high-purity Ar gas, oxygen partial pressure; 2 × 10 ⁻⁵ atm), upper chamber using low oxygen partial pressure side (using mixed gas of Ar gas and 2% by volume of H ₂ gas, (Oxygen partial pressure; 6 × 10 ⁻¹³ atm), the surface of each test piece when heat-treated at 170 ° C. was observed with a scanning electron microscope (SEM).

As a result, in the case of only Al ₂ O _{3 and} the case of containing 0.20 mol% of Lu ₂ O ₃ , grains generally observed on both the high oxygen partial pressure side and the low oxygen partial pressure side are observed. It showed the appearance of thermal etching at the boundary, and no grain boundary bulge or deep grain boundary groove was observed. In this way, on the low oxygen partial pressure side, only desorption of oxygen occurs, and no movement of the Al component occurs, so that no bulges of grain boundaries and deep grain boundary grooves are observed on the sample surface after processing. It is presumed that the grain boundary portion of the film is in the form of thermal etching. Further, when 0.20 mol% of Lu ₂ O ₃ is contained, the etching level is lower than when only Al ₂ O ₃ is used, and the effect of suppressing mass transfer due to the addition of Lu appears at the grain boundary. It is considered that when Lu ₂ O ₃ is contained, a more excellent EBC film can be formed.

As described above, in the region where the n-type is expressed (oxygen partial pressure <10 ⁻⁶ atm), when Al ₂ O ₃ contains a predetermined amount of rare earth element, the diffusion and permeation of corrosive species are sufficiently achieved. In addition, the phase separation and segregation in the film can be suppressed, and an EBC film having excellent barrier performance can be formed. A member is obtained.

  The present invention can be used in various heat-resistant members that require an environmental barrier coating. For example, various parts such as internal combustion engines, boilers, steam turbines, gas turbines, etc. in various plants, transportation equipment, other facilities, equipment, equipment, etc. Can also be used when forming a uniform EBC film having a uniform thickness.

It is typical explanatory drawing of the apparatus used for the measurement of an oxygen permeability coefficient. It is a graph of the oxygen partial pressure dependence of _{Al 2 O 3 / Lu 2 O} 3 based oxygen permeability coefficient. It is an explanatory view by SEM photographs of the surface of the fine structure of the high oxygen partial pressure side of the oxygen potential gradient under the exposed the _{Al 2 O 3 / Lu 2 O} 3 sintered body. Is an explanatory view by SEM photographs of the surface of the microstructure of the low oxygen partial pressure side of the oxygen potential Al 2 _O were exposed to a gradient _{3 /} Lu ₂ O 3 sintered body. Is an explanatory diagram of a high oxygen partial pressure side of the surface of the exposed to an oxygen potential gradient polycrystalline Al ₂ O ₃ sintered body by SEM photograph of the microstructure. It is an explanatory view by SEM photographs of the surface of the microstructure of the low oxygen partial pressure side of the exposed to an oxygen potential gradient polycrystalline Al ₂ O ₃ sintered body.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100; Gas permeation coefficient measuring apparatus, 11: Upper alumina protective tube, 12: Lower alumina protective tube, 13: Outer alumina protective tube, 21, 22; Pt seal ring, 3; Disk-shaped specimen, 4; Ar gas Supply piping, 5; cooling bath, 61, 62; oxygen sensor, 7; gas chromatography, 8; electric furnace, 91; upper substrate, 92;

Claims (4)

An alumina thin film forming material containing an alumina powder and a rare earth compound powder and used for forming an environmental barrier coating film, wherein the rare earth element is at least one of Sm, Eu, Tm and Lu. The amount of permeation of the corrosive gas in the thickness direction of the environmental barrier coating film when supplying a corrosive gas having different partial pressures to one side and the other side of the environmental barrier coating film using the alumina thin film forming material. In measurement, when the partial pressure is changed, the dependency of the permeation amount on the change is evaluated, and the permeation coefficient of the corrosive gas at each partial pressure is calculated. And evaluating the barrier performance of the environmental barrier coating film based on the correlation. The barrier performance evaluation according to claim 1, wherein the rare earth compound powder is 0.1 to 0.5 mol% when the total of the alumina powder and the rare earth compound powder converted to oxide is 100 mol%. Method. An alumina thin film forming material containing an alumina powder and a rare earth compound powder and used for forming an environmental barrier coating film, wherein the rare earth element is at least one of Sm, Eu, Tm and Lu. Corrosion gas supply means for supplying a corrosive gas having a different partial pressure to one side and the other side of the environmental barrier coating film using the alumina thin film forming material, and the corrosive gas in the thickness direction of the environmental barrier coating film. Measuring means for measuring the permeation amount; coefficient calculating means for determining a permeation coefficient of the corrosive gas based on the permeation amount at each partial pressure when the partial pressure is changed; and the partial pressure and the permeation amount An evaluation unit that evaluates the barrier performance of the environmental barrier coating film based on the correlation with the coefficient. The barrier performance evaluation according to claim 3, wherein the rare earth compound powder is 0.1 to 0.5 mol% when the total of the alumina powder and the oxide-converted rare earth compound powder is 100 mol%. apparatus.