JP6173778B2 - Thermal barrier coating materials - Google Patents

Description

  The present invention relates to a thermal barrier coating material used for forming a film having excellent low thermal conductivity and durability.

  2. Description of the Related Art Conventionally, in a gas turbine engine for power generation, an aircraft jet engine, and the like, since the combustion gas is high temperature, a thermal barrier coating (Thermal Barrier Coating) is applied to the surface of a high-temperature component such as a moving blade, a stationary blade, or a combustor. A coating referred to as TBC) is applied. The surface of the thermal barrier coating is provided with corrosion resistance, oxidation resistance, heat resistance, and the like. Although materials containing yttria-stabilized zirconia are widely used for the formation of this film, in recent years, a search has been made for materials that give lower thermal conductivity than yttria-stabilized zirconia.

Patent Document 1 discloses a metal object having a film containing a compound having a pyrochlore structure represented by A ₂ B ₂ O ₇ (such as La ₂ Zr ₂ O ₇ ).
Patent Document 2 discloses a thermal barrier coating member having a thermal barrier layer made of a ceramic obtained by adding 0.1 to 10 mol% of lanthanum oxide to rare earth stabilized zirconia and rare earth stabilized zirconia-hafnia.
In Patent Document 3, it is represented by Ln ₃ Nb _1-x Ta _x O ₇ (0 ≦ x ≦ 1, Ln is one or more atoms selected from the group consisting of Sc, Y and lanthanoid). A thermal barrier coating material mainly comprising a compound is disclosed.
In Patent Document 4, Ln _1-x M _x O _{1.5 + x} (0.13 ≦ x ≦ 0.24, Ln is one or more atoms selected from the group consisting of Sc, Y and lanthanoids, A thermal barrier coating material mainly containing a compound represented by M being Ta or Nb) is disclosed.
Further, Patent Document _{5, Ln x + y-3xy} Ti x Ta x Zr (1-3x) (1-y) O 2 + 1.5xy-0.5y (0.05 ≦ x ≦ 0.25,0 ≦ y ≦ 0.15, Ln is a thermal barrier coating material mainly containing one or more atoms selected from the group consisting of Y, Sm, Yb and Nd).

Japanese Patent Laid-Open No. 10-212108 JP 2004-270032 A JP 2006-298695 A JP 2009-221551A JP 2010-235415 A

In a high-temperature structural material including a thermal barrier coating material, inclusion of a compound that causes a phase transformation (phase transition) at the time of temperature increase or decrease causes a volume change due to the temperature change and causes cracking of the film or the like. Therefore, as a thermal barrier coating material, a material having a lower thermal conductivity than yttria-stabilized zirconia and hardly causing phase transformation is required particularly in the range of 25 ° C. to 1,000 ° C.
The object of the present invention is excellent in low thermal conductivity, and hardly causes phase transformation due to temperature rise or fall in the range of 25 ° C. to 1,200 ° C., and deformation, breakage, etc. due to volume change accompanying phase transformation are suppressed. It is to provide a thermal barrier coating material used for forming a film having excellent durability, and an article (composite) provided with a film formed using this material.

The present invention is shown below.
1. A thermal barrier coating material comprising at least one compound selected from a compound represented by the following general formula (1) and a compound represented by the following general formula (2).
Y _1-x La _x Ta ₃ O ₉ (1)
(In the formula, x is 0.15 to 0.30 .)
Y _{1 + y} Ta _3-3y Zr _3y O ₉ (2)
(In the formula, y is 0.05 to 0.10.)
2. An article comprising a coating containing the thermal barrier coating material according to 1 above.

The thermal barrier coating material of the present invention is suitable for forming a film having excellent low thermal conductivity such as a thermal conductivity of less than 2.0 W / (m · K) in the range of 25 ° C. to 1,000 ° C. The compounds represented by the above general formulas (1) and (2) are less likely to undergo phase transformation due to temperature rise or fall in the range of 25 ° C. to 1,200 ° C., and the melting point is 1,700 ° C. It is high as above and is thermally stable. Therefore, when a film is formed on the surface of the substrate using the thermal barrier coating material of the present invention, cracking occurs from the substrate at temperatures below the melting point of the compounds represented by the general formulas (1) and (2). Generation | occurrence | production of peeling etc. is suppressed and it is excellent in durability (shape retention property). An article (composite) having a film formed on the surface of a member made of a metal, an alloy, a heat-resistant oxide, etc. using the thermal barrier coating material of the present invention by utilizing such properties is structurally Is stable.
The article of the present invention preferably comprises a substrate and a film (thermal barrier coating) formed on the surface thereof directly or via an intermediate layer using a thermal barrier coating material. , 400 ° C to 1,700 ° C, and suitable for applications requiring long life in low thermal conductivity, corrosion resistance, oxidation resistance, heat resistance, heat insulation, and the like.

It is the schematic which shows the structure of the compound represented by General formula (1) and (2). 3 is a graph showing X-ray diffraction images of Y—La—Ta based composite oxides obtained in Example 1, Example 2 and Comparative Example 1. FIG. 4 is a graph showing an X-ray diffraction image of a Y—Ta—Zr composite oxide obtained in Example 3. FIG. It is a graph which shows thermal conductivity, such as complex oxide obtained by Examples 1-3 and Comparative Example 1. FIG. 5 is a graph showing the coefficient of linear expansion of a composite oxide obtained in Comparative Example 1. 2 is a graph showing the linear expansion coefficient of the composite oxide obtained in Example 1. FIG. 4 is a graph showing the linear expansion coefficient of the composite oxide obtained in Example 2. 6 is a graph showing the linear expansion coefficient of the composite oxide obtained in Example 3.

The thermal barrier coating material of the present invention comprises a compound represented by the following general formula (1) and at least one compound selected from the compounds represented by the following general formula (2): To do.
Y _1-x La _x Ta ₃ O ₉ (1)
(In the formula, x is 0.15 to 0.30 .)
Y _{1 + y} Ta _3-3y Zr _3y O ₉ (2)
(In the formula, y is 0.05 to 0.10.)

The compounds represented by the general formulas (1) and (2) are cation deficient defect perovskite complex oxides (hereinafter also referred to as “composite oxides”), and have a structure as shown in FIG. Have. This structure is a structure in which 2/3 of the A ions (marked with x in FIG. 1) are missing from the perovskite structure represented by A ₃ B ₃ O ₉ .
The compound represented by the general formula (1) has a structure in which a Y atom and a La atom are contained in the A site, and a Ta atom is contained in the B site. On the other hand, the compound represented by the general formula (2) has a structure in which a Y atom is contained in the A site and x mark, and a Ta atom and a Zr atom are contained in the B site.

In the above general formula (1), x is 0.15 to 0.30 , preferably 0.18 to 0.30 , more preferably 0.20 to 0.30 , and particularly preferably 0.20 to 0. .30.
In the general formula (2), y is 0.05 to 0.10, preferably 0.06 to 0.09, more preferably 0.07 to 0.08, and particularly preferably 0.08. It is.
When x and y are in the above range, the composite compound is unlikely to undergo phase transformation due to temperature rise or temperature fall in the range of 25 ° C. to 1,200 ° C., and volume change associated with phase transformation is suppressed. As a result, when a film or the like is formed using the thermal barrier coating material of the present invention containing the above compound, it is possible to suppress inconveniences such as deformation and breakage due to volume change, particularly at a temperature in the above range. . In the general formula (1), when x is less than 0.15, there is an orthorhombic to tetragonal phase transformation (phase transition), resulting in poor durability of the film. On the other hand, in the case of a compound where x is greater than 0.50, the average thermal expansion coefficient tends to be small.
In addition, the phase transformation is performed using, for example, a thermomechanical analyzer or the like in an atmosphere of air, oxygen gas, argon gas, etc., in a temperature range of 25 ° C. to 1,200 ° C. with a constant temperature increase and decrease. Heating and cooling can be performed, and the dimensional change can be observed and confirmed by the behavior of the linear expansion coefficient.

The melting point of the composite oxide represented by the general formulas (1) and (2) is usually 1,700 ° C. or higher, and the thermal conductivity (measurement temperature) measured by the laser flash method in accordance with JIS R1611. : 25 ° C. to 1,000 ° C.) is preferably less than 2.0 W / (m · K), more preferably less than 1.8 W / (m · K).
When the thermal barrier coating material of the present invention contains a complex oxide having these structures, a film having excellent low thermal conductivity and durability can be obtained.

The composite oxide contained in the thermal barrier coating material of the present invention may be only one type or two or more types.
The thermal barrier coating material of the present invention preferably comprises only the above complex oxide.

  The thermal barrier coating material of the present invention is made of a desired material by being subjected to methods such as electron beam physical vapor deposition (EB-PVD), plasma spraying, vacuum plasma spraying, flame spraying, high-speed spraying, and sintering. A stable film can be formed on the surface of a substrate or the like.

The method for producing the composite oxide represented by the general formula (1) includes a compound containing a Y element (hereinafter referred to as “compound (m1)”) and a compound containing a La element (hereinafter referred to as “compound (m2)”). And a compound containing Ta element (hereinafter referred to as “compound (m3)”) in such a manner that the molar ratio of each atom is a predetermined ratio, and this is heat treated. It is.
The method for producing the composite oxide represented by the general formula (2) also includes a compound containing a Y element (hereinafter referred to as “compound (m1)”) and a compound containing a Ta element (hereinafter referred to as “compound (m3)”. ) ") And a compound containing a Zr element (hereinafter referred to as" compound (m4) ") are generally blended so that the molar ratio of each atom is a predetermined ratio, and this is heat treated. Is.
In any of the above cases, in order to obtain a more homogeneous composite oxide, for example, there is also a method of heat-treating a mixture containing urea.

  As the compound (m1), the compound (m2), the compound (m3), and the compound (m4), oxides, hydroxides, sulfates, carbonates, nitrates, phosphates, halides, and the like can be used. . Among these, when obtaining a complex oxide having a more uniform composition, a water-soluble compound is preferable, but a water-insoluble compound can also be used.

  A preferred method for producing the composite oxide represented by the general formulas (1) and (2) will be described.

In the case of the composite oxide represented by the general formula (1), first, the compound (m1) compounded so that the molar ratio of the total amount of Y atoms and La atoms to Ta atoms is 1: 3 Then, a mixed solution composed of an aqueous solution or an aqueous dispersion (suspension) containing the compound (m2) and the compound (m3) and urea is prepared. The concentrations of the compound (m1), the compound (m2), the compound (m3) and the urea contained in this mixed solution are preferably 0.02 to 0.1 mol / l, 0.02 to 0.1 mol / l, 0.02-0.1 mol / l and 2-10 mol / l, more preferably 0.02-0.05 mol / l, 0.02-0.05 mol / l, 0.02-0.05 mol / l and 2 ~ 5 mol / l.
In the case of the composite oxide represented by the general formula (2), first, the compound (m1) and the compound (m3) are blended so that the charge balance of Y atom, Ta atom and Zr atom is maintained. And a mixed solution composed of an aqueous solution or aqueous dispersion (suspension) containing the compound (m4) and urea. The concentrations of the compound (m1), the compound (m3), the compound (m4) and the urea contained in this mixed solution are preferably 0.02 to 0.1 mol / l, 0.02 to 0.1 mol / l, 0.02-0.1 mol / l and 2-10 mol / l, more preferably 0.02-0.05 mol / l, 0.02-0.05 mol / l, 0.02-0.05 mol / l and 2 ~ 5 mol / l.
Hereinafter, the composite oxide represented by the general formulas (1) and (2) is manufactured by the same operation.

Next, the mixed liquid is heated at a temperature of 80 ° C. to 95 ° C. under reflux cooling to perform a urea hydrolysis reaction. The reaction time is usually 10 to 20 hours.
Thereafter, depending on the form of the reaction product contained in the reaction system, centrifugation or the like is performed as necessary to collect the reaction product. And it wash | cleans using water, alcohol, etc., it is made to dry, and the powder which consists of a 1st precursor compound is obtained by grind | pulverizing as needed.
Next, the powder composed of the first precursor compound is sized and, if necessary, subjected to press molding or the like to produce a molded product such as a plate or lump. And this molded product is heat-treated (calcination) for about 1 to 3 hours at a temperature of 1,200 ° C. to 1,500 ° C. in an atmosphere containing oxygen gas, and a calcined product made of the second precursor compound is obtained. obtain.
Thereafter, the obtained calcined product is pulverized and sized as necessary. Then, if necessary, it is subjected to press molding or the like to produce a molded product such as a plate or a lump, and this molded product is subjected to a temperature of 1,400 ° C. to 1,700 ° C. in an atmosphere containing oxygen gas. Then, heat treatment is performed for about 1 to 3 hours to obtain the composite oxide.

  Using the thermal barrier coating material of the present invention, a thermal barrier coating (film) is formed directly or indirectly on the surface of a substrate made of a material such as a metal or an alloy, and an integrated article (shield) is formed. Thermally coated articles), ie composites can be obtained.

  The method for forming the thermal barrier coating (film) may be the method exemplified above. In addition, the thickness of the thermal barrier coating (film) is appropriately selected according to the purpose, application, etc. From the viewpoint of low thermal conductivity, corrosion resistance, oxidation resistance, heat resistance, heat insulation, etc., the lower limit is Usually, it is 300 μm.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples as long as the gist of the present invention is not exceeded. In the following, “part” and “%” are based on mass unless otherwise specified.

Comparative Example 1 (Production of thermal barrier coating material containing Y _0.90 La _0.10 Ta ₃ O ₉ )
Distilled water 900 g were housed in a fluororesin-made reactor, with a purity of 99.99% or more _{Y (NO 3) 3 · 6H} 2 O powder (manufactured by Kanto Chemical Co., Inc.) 9 g (0.023 mol), purity and 99.99% of _{La (NO 3) 3 · 6H} 2 O powder (manufactured by Kanto Chemical Co., Inc.) 1 g (0.002 mol), put, stirred for 1 hour at room temperature (25 ° C.), colorless and transparent An aqueous solution of was obtained. Next, 90 g (3 mol) of urea was added to this aqueous solution, and the mixture was stirred at room temperature (25 ° C.) for 1 hour. Thereafter, 17 g (0.038 mol) of Ta ₂ O ₅ powder (manufactured by Rare Metallic) having a purity of 99.9% or more was added to the obtained colorless and transparent aqueous solution and stirred at room temperature (25 ° C.) for 7 hours. To obtain a suspension.
Next, the suspension was heated to 95 ° C. and reacted (urea hydrolysis reaction) with stirring while cooling under reflux (reaction time: 15 hours). Thereafter, the obtained reaction solution was centrifuged at 25 ° C. and 4,800 rpm for 30 minutes to recover the lower layer gel. When this gel was poured into a large amount of distilled water and sufficiently stirred, it was centrifuged under the same conditions as above to recover the lower layer gel. The gel was poured into a large amount of isopropyl alcohol, and when sufficiently stirred, the gel was centrifuged under the same conditions as described above to collect the precipitate.
Thereafter, the precipitate was heated in an air atmosphere at 120 ° C. for 24 hours to obtain a dry powder. The dried powder was then sieved (100 mesh) to collect a fine powder. And this fine powder was used for press molding (pressure 5MPa), and the disk-shaped molded object was produced. Then, this molded object was heat-processed (calcination) for 1 hour at 1,400 degreeC in air | atmosphere atmosphere, and the temporary baking molded object was obtained. The obtained calcined shape was dry-ground with a mortar at room temperature (25 ° C.).
Next, the dry pulverized product was sieved (100 mesh) to collect a fine powder. The fine powder was subjected to press molding (pressure 25 MPa), and further subjected to cold isostatic pressing (load 2.5 tons) to produce a disk-shaped molded body. Thereafter, the compact was heat-treated at 1,650 ° C. for 1 hour in an air atmosphere. The obtained fired body was dry pulverized with a mortar at room temperature (25 ° C.) and subjected to X-ray diffraction measurement. As a result, the fired body was substantially made of Y _0.90 La _0.10 Ta ₃ O _9. It was found that it is a monoclinic system (see FIG. 2A). Moreover, when the fired body was visually observed, it was confirmed that it was not melted by high-temperature heat treatment at 1,650 ° C. The density ρ was 6.83 g / cm ³ .
The fired body obtained as described above was directly used as a thermal barrier coating material.

Further, the fired body was subjected to a laser flash method (based on JIS R1611), and the thermal conductivity at 25 ° C., 200 ° C., 400 ° C., 600 ° C., 800 ° C. and 1,000 ° C. was measured. It is known that the thermal conductivity of a solid is easily affected by the pores of the measurement sample, and has a lower value if it has pores. Therefore, in order to obtain a dense thermal conductivity, it is preferable to use the correction formula (C. Wan, et al., Acta Mater., 58, 6166-6172 (2010)) shown in the following formula (10). It is said.
k ′ / k = 1−4 / 3φ (10)
(K ′: measured thermal conductivity, k: dense thermal conductivity, φ: porosity)
The thermal conductivity at each temperature is shown in FIG. 4 as k corrected by the above equation (10). For comparison, FIG. 4 also shows yttria-stabilized zirconia (YSZ) data cited from MR Winter, et al., J. Am. Ceram. Soc., 90, 533-540 (2007). .

In addition, using a thermomechanical analyzer “TMA8310” (model name) manufactured by Rigaku Corporation, heating the fired body in the range of 25 ° C. to 1,200 ° C. in the air at a heating rate and a cooling rate of 10 ° C. per minute. Then, the dimensional change was measured by the compression load method (load: 98 mN), and the linear expansion coefficient was calculated. The result is shown in FIG. Moreover, the linear expansion coefficient in the said temperature range was 9.61 * 10 < ^-6 > / degreeC.

Example 1 (Production of thermal barrier coating material containing Y _0.80 La _0.20 Ta ₃ O ₉ )
The amount of Y (NO ₃ ) ₃ · 6H ₂ O powder, La (NO ₃ ) ₃ · 6H ₂ O powder, urea, and Ta ₂ O ₅ powder was 8 grams (0.02 mol), 2 A fired body was produced in the same manner as in Comparative Example 1, except that the amount was changed to Gram (0.004 mol), 90 g (3 mol), and 17 g (0.038 mol). Next, X-ray diffraction measurement revealed that the fired body was a tetragonal system substantially composed of Y _0.80 La _0.20 Ta ₃ O ₉ (see FIG. 2B). Moreover, when the fired body was visually observed, it was confirmed that it was not melted by high-temperature heat treatment at 1,650 ° C. The density ρ was 7.30 g / cm ³ .
Thereafter, in the same manner as in Comparative Example 1, the thermal conductivity and the linear expansion coefficient were obtained. The results are shown in FIGS. Moreover, the linear expansion coefficient in the range of 25 degreeC-1,200 degreeC was 8.43 * 10 < ^-6 > / degreeC.

Example 2 (Production of thermal barrier coating material containing Y _0.70 La _0.30 Ta ₃ O ₉ )
The amount of Y (NO ₃ ) ₃ · 6H ₂ O powder, La (NO ₃ ) ₃ · 6H ₂ O powder, urea, and Ta ₂ O ₅ powder was 7 grams (0.018 mol), 3 A fired body was produced in the same manner as in Comparative Example 1 except that it was changed to Gram (0.007 mol), 90 g (3 mol), and 17 g (0.038 mol). Next, X-ray diffraction measurement revealed that the fired body was a tetragonal system substantially composed of Y _0.70 La _0.30 Ta ₃ O ₉ (see FIG. 2C). Moreover, when the fired body was visually observed, it was confirmed that it was not melted by high-temperature heat treatment at 1,650 ° C. The density ρ was 7.37 g / cm ³ .
Thereafter, in the same manner as in Comparative Example 1, the thermal conductivity and the linear expansion coefficient were obtained. The results are shown in FIGS. Moreover, the linear expansion coefficient in the range of 25 degreeC-1,200 degreeC was 7.86 * 10 < ^-6 > / degreeC.

Example 3 (Production of thermal barrier coating material containing Y _1.08 Ta _2.76 Zr _0.24 O ₉ )
Distilled water 900 g were housed in a fluororesin-made reactor, with a purity of 99.99% or more _{Y (NO 3)} (manufactured by Kanto Chemical Co., Inc.) 3 · 6H ₂ O powder 10 grams (0.025 mol), purity 3 g (0.007 mol) of 99.95% or more of ZrCl ₂ O.8H ₂ O powder (manufactured by Kanto Chemical Co., Inc.) was added and stirred at room temperature (25 ° C.) for 1 hour to give a colorless and transparent aqueous solution. Obtained. Next, 90 g (3 mol) of urea was added to this aqueous solution, and the mixture was stirred at room temperature (25 ° C.) for 1 hour. Thereafter, 12 g (0.026 mol) of Ta ₂ O ₅ powder (manufactured by Rare Metallic) having a purity of 99.9% or more was added to the obtained colorless and transparent aqueous solution and stirred at room temperature (25 ° C.) for 7 hours. To obtain a suspension.
Next, the suspension was heated to 95 ° C. and reacted (urea hydrolysis reaction) with stirring while cooling under reflux (reaction time: 15 hours). Thereafter, the obtained reaction solution was centrifuged at 25 ° C. and 4,800 rpm for 30 minutes to recover the lower layer gel. When this gel was poured into a large amount of distilled water and sufficiently stirred, it was centrifuged under the same conditions as above to recover the lower layer gel. The gel was poured into a large amount of isopropyl alcohol, and when sufficiently stirred, the gel was centrifuged under the same conditions as described above to collect the precipitate.
Thereafter, the precipitate was heated in an air atmosphere at 120 ° C. for 24 hours to obtain a dry powder. The dried powder was then sieved (100 mesh) to collect a fine powder. And this fine powder was used for press molding (pressure 5MPa), and the disk-shaped molded object was produced. Then, this molded object was heat-processed (calcination) for 1 hour at 1,400 degreeC in air | atmosphere atmosphere, and the temporary baking molded object was obtained. The obtained calcined shape was dry-ground with a mortar at room temperature (25 ° C.).
Next, the dry pulverized product was sieved (100 mesh) to collect a fine powder. The fine powder was subjected to press molding (pressure 25 MPa), and further subjected to cold isostatic pressing (load 2.5 tons) to produce a disk-shaped molded body. Thereafter, the compact was heat-treated at 1,650 ° C. for 1 hour in an air atmosphere. The obtained fired body was dry-ground with a mortar at room temperature (25 ° C.) and subjected to X-ray diffraction measurement. As a result, the fired body was substantially Y _1.08 Ta _2.76 Zr _0.24 O. ₉ was found to be tetragonal (see FIG. 3). Moreover, when the fired body was visually observed, it was confirmed that it was not melted by high-temperature heat treatment at 1,650 ° C. The density ρ was 7.25 g / cm ³ .
The fired body obtained as described above was directly used as a thermal barrier coating material.
Thereafter, in the same manner as in Comparative Example 1, the thermal conductivity and the linear expansion coefficient were obtained. The results are shown in FIGS. Moreover, the linear expansion coefficient in the range of 25 degreeC-1,200 degreeC was 8.87 * 10 < ^-6 > / degreeC.

  As is clear from FIGS. 4 to 8, Comparative Example 1 is the same as Examples 1 to 3 using the thermal barrier coating material containing the compounds represented by the general formulas (1) and (2) according to the present invention. In addition, in the range of 25 ° C. to 1,200 ° C., the thermal conductivity of yttria-stabilized zirconia (YSZ) is lower and it can be seen that the heat shielding property is excellent. However, in the thermal barrier coating material according to Comparative Example 1, an orthorhombic-tetragonal phase transformation was confirmed (FIG. 5), whereas in the thermal barrier coating material according to Examples 1 to 3, the phase transformation was confirmed. The transformation was not confirmed (FIGS. 6 to 8). That is, the thermal barrier coating material according to Examples 1 to 3 is suitable for forming a film having excellent durability by suppressing deformation, breakage, and the like accompanying volume change in the range of 25 ° C. to 1,200 ° C. I understand that there is.

  According to the thermal barrier coating material of the present invention, a film having excellent low thermal conductivity and durability is conventionally formed by a known method such as thermal spraying, or a layer (intermediate layer) disposed on the surface of a member made of metal, an alloy, or the like. Can be efficiently formed on the surface of the layer. This configuration is suitable for application to a combustor in an aircraft jet engine, a high-temperature component in a power generation gas turbine, and other high-temperature components in various plants.

Claims (2)

A thermal barrier coating material comprising at least one compound selected from a compound represented by the following general formula (1) and a compound represented by the following general formula (2).
Y _1-x La _x Ta ₃ O ₉ (1)
(In the formula, x is 0.15 to 0.30 .)
Y _{1 + y} Ta _3-3y Zr _3y O ₉ (2)
(In the formula, y is 0.05 to 0.10.)   An article comprising a coating comprising the thermal barrier coating material according to claim 1.

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