JP2015218379A - Thermal barrier coating material for steam turbine, and steam apparatus for power generation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal barrier coating material for a steam turbine, which is usable under high-temperature steam, and excellent in economical efficiency.SOLUTION: A thermal barrier coating material for a steam turbine in an embodiment has a metal intermediate layer, a first layer and a second layer in this order on a metal substrate. The first layer and the second layer contain zirconium oxide respectively. The average pore rate of the second layer is lower than the average pore rate of the first layer. Further, the mass ratio of a stabilizer contained in the second layer is higher than the mass ratio of the stabilizer contained in the first layer.

Description

  Embodiments described herein relate generally to a thermal barrier coating material for a steam turbine and a steam generator for power generation.

  Conventionally, in steam equipment in which high-temperature steam is circulated, for example, steam turbines in thermal power generation facilities, since the steam temperature is less than 600 ° C., high-temperature parts such as turbine rotors, nozzles, and moving blades are economical. Ferritic heat-resistant steel is used from the viewpoint of productivity and productivity.

  A steam turbine having a steam temperature of about 600 ° C. is also operated for the purpose of improving the efficiency of the thermal power generation facility. When the steam temperature is about 600 ° C., sufficient high-temperature strength cannot be obtained with ferritic heat-resistant steel. Therefore, heat-resistant alloys mainly composed of nickel, austenitic heat-resistant steel, and the like are used for high-temperature parts.

  In recent years, steam turbines having a steam temperature exceeding 700 ° C. have been developed for the purpose of further increasing the efficiency of thermal power generation facilities. However, in the case of a steam turbine whose steam temperature exceeds 700 ° C., sufficient high-temperature strength cannot be ensured only by improving the constituent materials.

  As a method for ensuring high temperature strength, it has been studied to cool high temperature parts with cooling steam. However, when the cooling steam is used, the cooling steam reaching several percent of the mainstream is required. In addition, when cooling steam is used, the cooling steam flows into the steam passage, so that the thermal efficiency is lowered.

  On the other hand, in a gas turbine, in order to protect a high-temperature component from a high-temperature combustion gas exceeding 1000 ° C., a heat shield layer containing zirconium oxide having low thermal conductivity is provided on the surface of the high-temperature component. However, when such a thermal barrier layer is applied to a high-temperature component of a steam turbine, the structural stability of zirconium oxide is lowered due to the reaction with the high-temperature steam, and the thermal barrier layer is easily peeled off from the high-temperature component. In addition, since the temperature of the working gas is lower than that of the gas turbine and the temperature difference between the inner and outer surfaces of the steam turbine is small, the heat shield layer can be formed to a sufficient thickness, thereby improving the heat shield property. It must be improved.

JP-A-7-247806 JP 2005-200226 A JP 2011-12287 A

  Conventionally, various improvements have been made to the constituent materials in order to ensure sufficient high-temperature strength for the high-temperature components of the steam turbine. However, in the case of a steam turbine having a steam temperature exceeding 700 ° C., sufficient high-temperature strength cannot be ensured only by improving the constituent materials.

  In order to ensure high temperature strength, for example, cooling of high-temperature components with cooling steam has been studied, but it is not always preferable because thermal efficiency is lowered. In addition, the application of the heat shield layer used for high-temperature parts of gas turbines to high-temperature parts of steam turbines is also under consideration, but the heat shield layer used for high-temperature parts of gas turbines is simply applied to high-temperature parts of steam turbines. Then, the heat shielding layer is easily peeled off by contact with high temperature steam.

  The problem to be solved by the present invention is to provide a thermal barrier coating material for a steam turbine that can be used under high-temperature steam and is also economical.

  The thermal barrier coating material for a steam turbine according to the embodiment has a metal intermediate layer, a first layer, and a second layer in this order on a metal substrate. The first layer and the second layer each contain zirconium oxide. The average porosity of the second layer is lower than the average porosity of the first layer. Moreover, the ratio in the mass of the stabilizer contained in a 2nd layer is higher than the ratio in the mass of the stabilizer contained in a 1st layer.

It is sectional drawing which shows the thermal barrier coating material for steam turbines of 1st Embodiment. It is sectional drawing which shows the thermal barrier coating material for steam turbines of 2nd Embodiment. It is meridional sectional drawing which shows the steam turbine of embodiment.

  Hereinafter, the thermal barrier coating material for a steam turbine of the embodiment will be specifically described. In the following description, the thermal barrier coating material for steam turbine is simply referred to as a thermal barrier coating material.

FIG. 1 is a cross-sectional view showing the thermal barrier coating material of the first embodiment.
The thermal barrier coating material 10 has, for example, a metal intermediate layer 12 and a thermal barrier layer 13 in this order on a metal substrate 11.

  The metal substrate 11 is made of a metal material. As a metal material, the metal material conventionally used for the component of a steam turbine can be used without a restriction | limiting in particular. Examples of such metal materials include steel materials such as CrMoV steel and 12Cr steel, and Ni-base and Co-base superalloys used for high-temperature parts such as gas turbines. These metal materials can be appropriately selected according to the operating temperature range, load stress, and the like.

  The metal intermediate layer 12 prevents oxidation of the metal substrate 11 due to high-temperature steam and has an intermediate thermal expansion coefficient between the metal substrate 11 and the heat shield layer 13 and is generated in the heat shield layer 13 due to a temperature change. Relieve thermal stress. As a constituent material of the metal intermediate layer 12, a NiCr alloy, a MCrAlY alloy (M is at least one element selected from Fe, Ni, Co) and the like can be appropriately selected.

  For example, in the case of the thermal barrier coating material 10 used at a temperature of 600 ° C. or lower, since the formation of Cr oxide is effective in suppressing water vapor oxidation corrosion, the constituent material of the metal intermediate layer 12 is Cr concentration. An alloy having a higher Al concentration (Cr concentration> Al concentration) is preferred. Further, in the case of the thermal barrier coating material 10 used at a temperature exceeding 600 ° C., since the formation of Al oxide is effective in suppressing steam oxidation corrosion, the constituent material of the metal intermediate layer 12 is Cr concentration. An alloy having a lower Al concentration (Cr concentration <Al concentration) is preferred.

The heat shielding layer 13 is provided in order to ensure the strength of the metal substrate 11 under high temperature steam. The thermal barrier layer 13 includes at least zirconium oxide, and may include a stabilizer as necessary. As the stabilizer, various rare earths such as Y ₂ O ₃ , Gd ₂ O ₃ , Nd ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O ₃ , Dy ₂ O ₃ , Lu ₂ O ₃ , Eu ₂ O _3, etc. Examples include elemental oxides.

  The heat shield layer 13 includes a first layer 14 and a second layer 15 in this order from the metal substrate side. The first layer 14 is provided mainly to ensure heat shielding properties. The second layer 15 is provided mainly to protect the first layer 14 from high temperature steam. The thermal barrier coating material 10 has a thermal barrier layer 13 composed of at least two layers of the first layer 14 and the second layer 15 having these different functions, so that it can be used under high-temperature steam. And it is also economical.

  Specifically, since the heat shielding property is ensured by the first layer 14, the high temperature strength of the metal substrate 11 is ensured, and the first layer 14 is protected by the second layer 15, so that the heat shielding layer is protected. 13 is prevented from being deteriorated and peeled off, and can be used under high-temperature steam. In addition, the first layer 14 and the second layer 15 can be easily formed by thermal spraying. In particular, the first layer 14 and the second layer 15 can be easily formed by adjusting the components of the thermal spray material and the thermal spraying conditions. Hereinafter, the metal substrate side in the heat shielding layer 13 is simply referred to as a substrate side, and the opposite side is referred to as a surface side.

  The first layer 14 and the second layer 15 are configured such that the average porosity of the second layer 15 is lower than the average porosity of the first layer 14. Since the average porosity of the second layer 15 on the surface side is low, the intrusion of high temperature steam from the surface side to the base material side is suppressed, and the first layer 14 is protected from the high temperature steam. On the other hand, since the average porosity of the first layer 14 on the base material side is high, the thermal conductivity is lowered to ensure heat shielding properties, and the thermal stress generated inside is relaxed to increase the film thickness. It becomes easy.

  The first layer 14 preferably has an average porosity of 20% or more. When it has an average porosity of 20% or more, it is preferable because heat shielding properties are improved. The average porosity is preferably 50% or less, more preferably 40% or less, and even more preferably 30% or less from the viewpoint of ensuring mechanical strength.

  The second layer 15 preferably has an average porosity of 10% or less. In the case of having an average porosity of 10% or less, entry of high temperature steam from the surface side to the base material side is suppressed, and thus the first layer 14 is effectively protected from high temperature steam. The average porosity may be 0%, but if it is close to 0%, the thermal stress generated inside becomes difficult to be relaxed, and the second layer 15 is easily peeled off from the first layer 14, so that the average porosity is 5% or more. Is preferred.

  Note that the average porosity is obtained, for example, by measuring five arbitrary portions in a cross section in the thickness direction of the layer to obtain the porosity, and averaging these. Moreover, the porosity of each part can be measured using an image processing apparatus, for example, is calculated | required as a ratio of the cross-sectional area of a pore in the cross-sectional area (50 micrometers x 50 micrometers) of the thickness direction of a layer.

  The ratio of the first layer 14 and the second layer 15 in the mass of the stabilizer included in the second layer 15 is higher than the ratio in the mass of the stabilizer included in the first layer 14. It is comprised so that it may become. When the proportion of the stabilizer contained in the second layer 15 is higher than the proportion of the stabilizer contained in the first layer 14, the structural stability of the second layer 15 in high-temperature steam is improved. The first layer 14 is protected from hot steam. On the other hand, since the first layer 14 is protected from the high temperature steam by the second layer 15, the systematic stability in the high temperature steam may not necessarily be high, and the proportion of the stabilizer may be low. . Moreover, when the ratio of a stabilizer is low, a general raw material with a low ratio of a stabilizer can be used as a raw material used for forming a layer, and this is preferable because it is excellent in economic efficiency.

  The ratio by mass of the stabilizer contained in the first layer 14 is preferably 5 to 15%. When the ratio by weight of the stabilizer contained in the first layer 14 is 5% or more, it is preferable because the systematic stability of the first layer 14 in high-temperature steam becomes good. Moreover, when the ratio by the mass of the stabilizer contained in the 1st layer 14 is 15% or less, since the phase change etc. of the 1st layer 14 are suppressed, it is preferable.

  The ratio by mass of the stabilizer contained in the second layer 15 is preferably 7 to 20%. When the ratio by mass of the stabilizer contained in the second layer 15 is 7% or more, it is preferable because the structural stability of the second layer 15 in high-temperature steam becomes good. Moreover, when the ratio by the mass of the stabilizer contained in the 2nd layer 15 is 20% or less, since the phase change of the 2nd layer 15, etc. are suppressed, it is preferable. The ratio by mass of the stabilizer contained in the second layer 15 is more preferably 8% or more, and further preferably 9% or more.

  The second layer 15 preferably has a monoclinic zirconium oxide volume ratio of monoclinic zirconium oxide and cubic zirconium oxide of 5% or less. On the other hand, for the first layer 14, the volume ratio of the monoclinic zirconium oxide to the monoclinic zirconium oxide and the cubic zirconium oxide is not particularly limited, and may exceed 5%. Good.

  In general, zirconium oxide has a monoclinic, tetragonal, or cubic crystal structure. Among these, monoclinic zirconium oxide reduces the structural stability in high-temperature steam. Further, the volume ratio of monoclinic zirconium oxide to monoclinic zirconium oxide and cubic zirconium oxide is an index for evaluating the structural stability in high-temperature steam, As the proportion decreases, the structural stability in high temperature steam increases. Hereinafter, the above ratio is referred to as a monoclinic ratio.

  The monoclinic ratio is closely related to the proportion of stabilizer contained in zirconium oxide and the proportion of impurities contained in zirconium oxide. Specifically, the higher the proportion of the stabilizer contained in the zirconium oxide, the lower the monoclinic ratio, and the lower the proportion of the impurities contained in the zirconium oxide, the lower the monoclinic ratio.

  The monoclinic ratio can be calculated by the following formulas (1) and (2) from the peak intensity of each phase of zirconium oxide obtained in the X-ray diffraction measurement.

Here, m monoclinic, t represents a cubic, X _m is the X-ray diffraction peak intensity ratio of the monoclinic, C _m denotes the percentage of monoclinic in the monoclinic and cubic. In the formula (1), P is a constant and is 1.311 (H. Toraya, M. Yoshimura and S. Somiya: J. Am Ceram. Soc., 67 (1984), pp. C119-121. ).

  A monoclinic crystal ratio of the second layer 15 of 5% or less is preferable because the structural stability of the second layer 15 in high-temperature steam becomes good. The lower the monoclinic ratio of the second layer 15, the better the systematic stability of the second layer 15 in high-temperature steam, and it may be 0%. A monoclinic crystal ratio of 5% or less in the second layer 15 is obtained, for example, when the ratio by weight of the stabilizer in the second layer 15 is 7% or more.

  Since the first layer 14 is protected from the high-temperature steam by the second layer 15, the monoclinic crystal ratio is not necessarily limited and may exceed 5%. When the monoclinic crystal ratio exceeds 5%, a raw material used for forming the monoclinic crystal can be a material having a relatively high proportion of a stabilizer, and this is preferable because it is excellent in economic efficiency. The monoclinic ratio in the first layer 14 is preferably 10% or less from the viewpoint of the structural stability of the first layer 14 in high-temperature steam.

The first layer 14 and the second layer 15 may each contain an impurity. Impurities are components excluding zirconium oxide and stabilizers, and include silicon oxide (SiO ₂ ), titanium oxide (TiO ₂ ), aluminum oxide (Al ₂ O ₃ ), and iron oxide (Fe ₂ O ₃ ). Etc.

  The ratios by mass of impurities contained in the first layer 14 and the second layer 15 may each exceed 0.1%. When the proportion of impurities contained in each layer exceeds 0.1%, a general raw material having a relatively high proportion of impurities can be used to form each layer. This is preferable. In addition, for the second layer 15, even if the proportion by mass of impurities exceeds 0.1%, the proportion of the stabilizer is relatively high, so that the systematic stability in high-temperature steam is ensured. Is done. On the other hand, the first layer 14 is protected from high-temperature steam by the second layer 15 even if the proportion by mass of impurities exceeds 0.1%, so the proportion of the stabilizer is small. Also good.

  The ratio by mass of impurities contained in the first layer 14 and the second layer 15 is preferably 0.3% or more, since raw materials having a general impurity amount can be used. More preferably, it is 5% or more. The ratio by mass of impurities contained in the first layer 14 and the second layer 15 is preferably 5% or less, respectively. When the ratio of the impurities contained in the first layer 14 and the second layer 15 is 5% or less, an excessive decrease in the structural stability in high-temperature steam is suppressed. The ratio by mass of impurities contained in the first layer 14 and the second layer 15 is more preferably 3% or less, and further preferably 1% or less.

  Note that the ratio of the impurities contained in the first layer 14 and the second layer 15 in terms of mass can be measured by X-ray photoelectron spectroscopy (XPS) or the like.

The thermal resistance of the first layer 14 is preferably 1 × 10 ⁻³ m ² K / W or more. When the thermal resistance of the first layer 14 is 1 × 10 ⁻³ m ² K / W or more, the heat shielding property of the first layer 14 is good. The higher the thermal resistance of the first layer 14, the better the heat shielding properties, and more preferably 2 × 10 ⁻³ m ² K / W or more, and further preferably 3 × 10 ⁻³ m ² K / W or more. preferable.

Here, the thermal resistance is obtained by the following formula (3) from the thermal conductivity λ [W / (m · K)] of the layer and the thickness d [m]. The thermal conductivity λ of the layer can be measured by a laser flash method or the like.

  The thickness of the first layer 14 is preferably 1 mm or more. When the thickness of the 1st layer 14 is 1 mm or more, favorable heat-shielding property is obtained. The thickness of the first layer 14 is more preferably 1.5 mm or more because better heat shielding properties can be obtained. The thickness of the first layer 14 is usually sufficient if it is 5 mm.

  The thickness of the second layer 15 is preferably 50 μm or more. When the thickness of the 2nd layer 15 is 50 micrometers or more, the penetration | invasion of the high temperature vapor | steam from the surface side to the base material side is suppressed effectively. The thickness of the second layer 15 is more preferably 100 μm or more, and even more preferably 200 μm or more because penetration of high-temperature steam from the surface side to the substrate side is more effectively suppressed. On the other hand, the thickness of the second layer 15 is preferably 500 μm or less and more preferably 400 μm or less because peeling between the first layer 14 and the second layer 15 is suppressed.

Next, the thermal barrier coating material of the second embodiment will be described.
FIG. 2 is a cross-sectional view showing the thermal barrier coating material of the second embodiment.

  The thermal barrier coating material 20 has a metal intermediate layer 22 and a thermal barrier layer 23 in this order on a metal substrate 21. Since the metal base material 21 and the metal intermediate layer 22 are the same as the metal base material 11 and the metal intermediate layer 12 in the thermal barrier coating material 10 of the first embodiment, description thereof is omitted.

The heat shielding layer 23 is provided to ensure the strength of the metal base material 21 under high temperature steam. The thermal barrier layer 23 includes at least zirconium oxide, and may include a stabilizer as necessary. As the stabilizer, various rare earths such as Y ₂ O ₃ , Gd ₂ O ₃ , Nd ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O ₃ , Dy ₂ O ₃ , Lu ₂ O ₃ , Eu ₂ O _3, etc. Examples include elemental oxides.

  The heat shield layer 23 includes a first layer 24 and a second layer 25 in this order from the metal substrate side. The first layer 24 is provided mainly for ensuring heat shielding properties. The second layer 25 is provided mainly to protect the first layer 24 from high temperature steam. The thermal barrier coating material 20 has a thermal barrier layer 23 composed of at least two layers of the first layer 24 and the second layer 25 having these different functions, so that it can be used under high-temperature steam. And it is also economical.

  Specifically, the heat shielding property is ensured by the first layer 24, so that the high temperature strength of the metal substrate 21 is ensured, and the first layer 24 is protected by the second layer 25, so that the heat shielding layer is protected. 23 can be used under high-temperature steam since deterioration and peeling of 23 are suppressed. In addition, the first layer 24 and the second layer 25 can be easily formed by thermal spraying. In particular, the first layer 24 and the second layer 25 are easily formed by adjusting the components of the thermal spray material and the thermal spraying conditions.

  The first layer 24 and the second layer 25 are configured such that the average porosity of the second layer 25 is lower than the average porosity of the first layer 24. The average porosity of the first layer 24 and the second layer 25 is the same as the average porosity of the first layer 14 and the second layer 15 of the first embodiment, and thus the description thereof is omitted. To do.

The first layer 24 and the second layer 25 are configured such that the ratio by mass of impurities contained in the second layer 25 is lower than the ratio by mass of impurities contained in the first layer 24. Is done. Here, impurities are components excluding zirconium oxide and a stabilizer, and silicon oxide (SiO ₂ ), titanium oxide (TiO ₂ ), aluminum oxide (Al ₂ O ₃ ), iron oxide (Fe ₂ ). O ₃ ) and the like.

  When the proportion of impurities contained in the second layer 25 is lower than the proportion of impurities contained in the first layer 24, the structural stability of the second layer 25 in high-temperature vapor is improved, and the first Layer 24 is protected from hot steam. On the other hand, since the first layer 24 is protected from the high temperature steam by the second layer 25, the systematic stability in the high temperature steam is not necessarily high, and the ratio of impurities may be high. In addition, when the ratio of impurities is high, a general raw material with a low ratio of impurities can be used as a raw material used for forming a layer, which is preferable because it is excellent in economic efficiency.

  The ratio by mass of impurities contained in the first layer 24 may exceed 0.1%. When the ratio by mass of impurities contained in the first layer 24 exceeds 0.1%, a general raw material having a relatively high ratio of impurities can be used to form the first layer 24. Therefore, it is preferable because it is economical.

  The ratio by mass of impurities contained in the first layer 24 is preferably 0.3% or more and more preferably 0.5% or more because raw materials having a general impurity amount can be used. preferable. The ratio by mass of impurities contained in the first layer 24 is preferably 5% or less, and is preferably 3% or less because an excessive decrease in the structural stability of the first layer 24 in the high-temperature steam is suppressed. Is more preferable, and 1% or less is more preferable.

  The ratio by mass of impurities contained in the second layer 25 is preferably 0.1% or less. When the ratio by the mass of impurities contained in the second layer 25 is 0.1% or less, the structural stability of the second layer 25 in high-temperature steam becomes good. The ratio by mass of impurities contained in the second layer 25 is more preferably 0.09% or less, and more preferably 0.08% or less, because the structural stability in high-temperature steam becomes better. 0.07% or less is particularly preferable, and may be 0%.

  The magnitude relationship between the proportion of the stabilizer contained in the first layer 24 and the proportion of the stabilizer contained in the second layer 25 is not particularly limited and may be the same, May be different. Here, since the ratio of impurities in the second layer 25 is relatively low and the systematic stability in high-temperature steam is high, the ratio of the stabilizer does not necessarily have to be high. On the other hand, since the first layer 24 is protected from the high temperature steam by the second layer 25 and the systematic stability in the high temperature steam is not necessarily high, the proportion of the stabilizer may be low.

  The proportion of the stabilizers contained in the first layer 24 and the second layer 25 in terms of mass is preferably 5 to 20%, more preferably 7 to 15%. When the ratio by mass of the stabilizer contained in the first layer 24 and the second layer 25 is 5% or more, it is preferable because the structural stability in high-temperature steam becomes good. Moreover, when the ratio by the mass of the stabilizer contained in the 1st layer 24 and the 2nd layer 25 is 20% or less, the phase change of the 1st layer 24 and the 2nd layer 25, etc. are suppressed. Therefore, it is preferable.

  The second layer 25 preferably has a monoclinic zirconium oxide volume ratio (monoclinic crystal ratio) of monoclinic zirconium oxide and cubic zirconium oxide of 5% or less. . On the other hand, for the first layer 24, the volume ratio of monoclinic zirconium oxide to monoclinic zirconium oxide and cubic zirconium oxide (monoclinic ratio) is not particularly limited, It may exceed 5%.

  When the monoclinic ratio of the second layer 25 is 5% or less, it is preferable because the structural stability of the second layer 25 in high-temperature steam becomes good. The lower the monoclinic ratio of the second layer 25, the better the systematic stability of the second layer 25 in the high-temperature steam, and it may be 0%. A monoclinic crystal ratio of 5% or less in the second layer 25 can be obtained, for example, when the ratio of impurities by mass in the second layer 25 is 0.1% or less.

  Since the first layer 24 is protected from high-temperature steam by the second layer 25, the monoclinic crystal ratio is not necessarily limited, and may exceed 5%. When the monoclinic crystal ratio exceeds 5%, a raw material used for forming the monoclinic crystal can be a material having a relatively high proportion of a stabilizer, and this is preferable because it is excellent in economic efficiency. The monoclinic ratio in the first layer 24 is preferably 10% or less from the viewpoint of the structural stability of the first layer 24 in the high-temperature steam.

  Regarding the thermal resistance and thickness of the first layer 24, and the thickness of the second layer 25, the thermal resistance and thickness of the first layer 14 of the first embodiment, and the thickness of the second layer 15, respectively. Therefore, the description thereof is omitted.

  Although the thermal barrier coating material of the embodiment has been described above, the thermal barrier layer is not limited to the two-layer structure including the first layer and the second layer. Examples of such a heat shielding layer include those having a third layer containing at least zirconium oxide between the first layer and the second layer. Further, as another heat shielding layer, for example, a layer having a third layer containing at least zirconium oxide on the substrate side of the first layer can be mentioned. The third layer only needs to contain zirconium oxide, but preferably contains zirconium oxide and a stabilizer.

  Next, the manufacturing method of the thermal barrier coating material of the embodiment will be described by taking the manufacturing method of the thermal barrier coating material 10 of the first embodiment as an example.

  The thermal barrier coating material 10 is formed by forming a metal intermediate layer 12 on a metal substrate 11 and then forming a first layer 14 and a second layer 15 on the metal intermediate layer 12 in this order. 13 can be produced.

  The first layer 14 and the second layer 15 are formed, for example, by thermal spraying of a thermal spray raw material containing zirconium oxide and a stabilizer. At this time, the average porosity of each layer can be adjusted by the particle size of the spraying raw material, the spraying temperature, and the like. Moreover, the ratio of the stabilizer and impurities contained in each layer can be adjusted by the ratio of the stabilizer and impurities contained in the thermal spray material, respectively. The monoclinic ratio of each layer can be adjusted by the ratio of stabilizers or impurities contained in the thermal spray raw material.

  The first layer 14 and the second layer 15 are preferably formed by the following method, for example. That is, the first layer 14 is a thermal spray raw material having a monoclinic zirconium oxide volume ratio (monoclinic crystal ratio) of monoclinic zirconium oxide and cubic zirconium oxide of 20% or less. It is preferable to form it by a thermal spraying method. For the formation of the first layer 14, a thermal spray material having a monoclinic crystal ratio exceeding 10% is preferably used. The second layer 15 is formed by spraying a thermal spray material having a monoclinic zirconium oxide volume ratio (monoclinic crystal ratio) of monoclinic zirconium oxide and cubic zirconium oxide of 10% or less. It is preferable to form by the method to do.

  As described above, by forming the second layer 15 using the thermal spray raw material having a monoclinic crystal ratio of 10% or less, the monoclinic crystal ratio is reduced by thermal spraying, and the monoclinic crystal ratio of 5% or less. A second layer 15 having is obtained. In addition, by forming the first layer 14 using a thermal spray material having a monoclinic crystal ratio of 20% or less, the ratio of the monoclinic crystal is reduced by thermal spraying, and the monoclinic crystal ratio is 10% or less. 1 layer 14 is obtained.

  In addition, the first layer 14 is preferably formed by the following method, for example. That is, it is preferable to form a thermal spray raw material containing zirconium oxide and a resin and then remove the resin by heat treatment. As the resin, those having a decomposition temperature of 400 ° C. or higher are preferable because thermal decomposition during spraying is suppressed, and polyester resins and the like are preferable. According to such a method, since the pores are formed by removing the resin, a high porosity can be obtained.

  The first layer 14 is particularly preferably formed by the following method. That is, a method of spraying a thermal spray material containing hollow zirconium oxide is preferable. According to such a method, since the pores are introduced into the thermal spray raw material in advance, a high porosity can be obtained, and the variation in the porosity depending on the part is also reduced. The hollow zirconium oxide preferably has a spherical shape because air resistance during spraying and a decrease in speed are small.

  The thermal barrier coating materials 10 and 20 of the embodiment are suitably used for power generation steam equipment, and are particularly suitably used as components of steam turbines.

  FIG. 3 is a meridional sectional view showing a steam turbine to which the thermal barrier coating materials 10 and 20 of the embodiment are applied.

  As shown in FIG. 3, the steam turbine 30 includes a casing 40, and a turbine rotor 41 is provided in the casing 40. A rotor disk 42 is formed on the turbine rotor 41, and a plurality of rotor blades 43 are implanted in the rotor disk 42 in the circumferential direction. A moving blade cascade having a plurality of moving blades 43 in the circumferential direction is formed in a plurality of stages in the turbine rotor axial direction. The turbine rotor 41 is rotatably supported by a rotor bearing (not shown).

  A diaphragm outer ring 44 is installed on the inner periphery of the casing 40, and a diaphragm inner ring 45 is installed inside the diaphragm outer ring 44. A plurality of stationary blades 46 are arranged in the circumferential direction between the diaphragm outer ring 44 and the diaphragm inner ring 45 to constitute a stationary blade cascade. The stationary blade cascade is provided in a plurality of stages alternately with the moving blade cascade in the turbine rotor axial direction. The turbine blade cascade and the rotor blade cascade located on the downstream side thereof constitute one turbine stage.

  A ground seal portion 47 is provided between the turbine rotor 41 and the casing 40 to prevent leakage of steam to the outside. Further, a seal portion 48 is provided between the turbine rotor 41 and the diaphragm inner ring 45 in order to prevent the leakage of steam to the downstream side.

  Further, the steam turbine 30 is provided with a steam inlet pipe (not shown) through which the steam from the crossover pipe 49 is introduced into the steam turbine 30 through the casing 40.

  An exhaust chamber (not shown) for exhausting steam that has expanded in the turbine stage is provided downstream of the turbine stage at the final stage, and the steam is exhausted to the outside of the steam turbine 30 through the exhaust chamber. The The exhaust chamber communicates with a condenser (not shown).

  The thermal barrier coating materials 10 and 20 of the embodiment are suitably used as the turbine rotor 41, the moving blade 43, the stationary blade 46, and the like of the steam turbine 30. Note that the thermal barrier coating materials 10 and 20 of the embodiment are not limited to the above components, and are widely used for components in which at least a part of the steam turbine 30 is in contact with high temperature steam.

Example 1
A metal intermediate layer (thickness 0.15 mm) made of a NiCoCrAlY alloy was formed on the surface of a metal substrate made of 12Cr steel. Thereafter, on the surface of the metal intermediate layer, a general amount of impurities (SiO ₂ : 0.5 mass%, TiO ₂ : 0.1 mass%, Al ₂ O ₃ : 0.08 mass%, Fe ₂ O ₃ : 0 The first layer (thickness 2 mm) having an average porosity of 23% was formed using zirconium oxide stabilized by 8 mass% Y ₂ O ₃ . Further, on this first layer, a general impurity amount (SiO ₂ : 0.5 mass%, TiO ₂ : 0.1 mass%, Al ₂ O ₃ : 0.08 mass%, Fe ₂ O ₃ The second layer (thickness: 300 μm) having an average porosity of 9% was formed using zirconium oxide stabilized by 10% by mass of Y ₂ O ₃ . This produced the test body which has the thermal-insulation layer which consists of a 1st layer and a 2nd layer. In addition, this test body satisfy | fills the structure of the thermal-insulation coating material of 1st Embodiment.

(Comparative Example 1)
In the formation of the second layer (thickness 300 μm), the amount of general impurities (SiO ₂ : 0.5 mass%, TiO ₂ : 0.1 mass%, Al ₂ O ₃ : 0.08 mass%, Fe ₂ Example 1 except that an average porosity of 9% was formed using a zirconium oxide stabilized with 8% by mass of Y ₂ O ₃ and having an O _{3 of} 0.1% by mass). A test specimen was prepared in the same manner as described above.

  Next, the specimens of Example 1 and Comparative Example 1 were each exposed to saturated steam at 750 ° C. for 5000 hours, and the presence or absence of peeling of the thermal barrier layer was observed. The results are shown in Table 1 together with the configurations of the first layer and the second layer.

  In the case of a general impurity amount, when the proportion of the stabilizer contained in the second layer is higher than the proportion of the stabilizer contained in the first layer as in the test body of Example 1, Since the deterioration of the layer is suppressed, the heat shielding layer does not peel off and a healthy state is maintained up to 5000 hours. On the other hand, when the proportion of the stabilizer contained in the second layer and the proportion of the stabilizer contained in the first layer are the same as in the test sample of Comparative Example 1, the second layer deteriorated. As a result, the heat shield layer peels off. From these results, in the case of a general impurity amount, when the proportion of the stabilizer contained in the second layer is higher than the proportion of the stabilizer contained in the first layer, systematic stability under high-temperature steam It can be seen that the property is improved, and the peeling of the heat shielding layer is suppressed.

(Example 2)
A specimen was prepared in the same manner as in Example 1 except that the average porosity of the first layer was 15%. In addition, this test body satisfy | fills the structure of the thermal-insulation coating material of 1st Embodiment.

  Next, a thermal shock test (50 cycles) was performed in which the specimen of Example 2 was rapidly cooled in water from a heating state of 750 ° C. Similarly, the thermal shock test was conducted on the test body of Example 1. The results are shown in Table 2 together with the configurations of the first layer and the second layer.

  In the test body of Example 2 in which the average porosity of the first layer was 15%, a crack occurred at the interface between the metal intermediate layer and the heat shield layer, and the heat shield layer was peeled off. On the other hand, in the test body of Example 1 in which the average porosity of the first layer was 23%, the heat shielding layer did not peel even after 50 cycles. From these results, it can be seen that the average porosity of the first layer is preferably 20% or more.

(Example 3)
A metal intermediate layer (thickness 0.15 mm) made of a NiCoCrAlY alloy was formed on the surface of a metal substrate made of 12Cr steel. Thereafter, on the surface of the metal intermediate layer, a general amount of impurities (SiO ₂ : 0.5 mass%, TiO ₂ : 0.1 mass%, Al ₂ O ₃ : 0.08 mass%, Fe ₂ O ₃ : 0 The first layer (thickness) having an average porosity of 23% using zirconium oxide stabilized by 8 mass% Y ₂ O ₃ and 0.1 mass%, total: 0.78 mass%) 2 mm). Furthermore, on this first layer, high-purity _(SiO 2: 0.03 _wt%, TiO 2: 0.02 _{wt%, Al} 2 O 3: 0.004 _{wt%, Fe 2 O 3: 0} . Second layer having a mean porosity of 9% (thickness: 300 μm) using zirconium oxide stabilized with 8% by mass of Y ₂ O _3. Formed. This produced the test body which has the thermal-insulation layer which consists of a 1st layer and a 2nd layer. In addition, this test body satisfy | fills the structure of the thermal-insulation coating material of 2nd Embodiment.

(Comparative Example 2)
In the formation of the second layer (thickness 300 μm), the amount of general impurities (SiO ₂ : 0.5 mass%, TiO ₂ : 0.1 mass%, Al ₂ O ₃ : 0.08 mass%, Fe ₂ Except that an average porosity of 9% was formed using a zirconium oxide having an O ₃ : 0.1% by mass) and stabilized with 8% by mass of Y ₂ O _3. A test specimen was prepared in the same manner as in Example 3.

  Next, with respect to the specimens of Example 3 and Comparative Example 2, the volume of monoclinic zirconium oxide in monoclinic zirconium oxide and cubic zirconium oxide was determined based on the results of XRD analysis. The ratio (monoclinic ratio) was determined. The results are shown in Table 3 together with the configurations of the first layer and the second layer.

  When the ratio of impurities is 0.1% or less as in the second layer of Example 3, the monoclinic crystal ratio is 5% or less. On the other hand, when the impurity ratio exceeds 0.1% as in the first layer of Example 3, the monoclinic crystal ratio exceeds 5%.

  Further, the specimens of Example 3 and Comparative Example 2 were exposed to saturated steam at 750 ° C. for 5000 hours. The results are shown in Table 3 together with the configurations of the first layer and the second layer. Regarding the test body of Example 3 in which the monoclinic ratio of the second layer was 5% or less, the heat shielding layer did not peel and the sound state was maintained until 5000 hours. In the test body of Comparative Example 2 in which the monoclinic crystal ratio of the second layer exceeded 5%, the heat shielding layer deteriorated and peeled off.

  From these test results, it can be seen that the monoclinic crystal ratio is reduced by increasing the purity of the second layer, and the structural stability in high-temperature steam is improved. It can also be seen that the monoclinic ratio of the second layer is preferably 5% or less in order to ensure the structural stability in high-temperature steam.

(Reference Examples 1 and 2)
As shown in Table 4, spraying raw materials having different monoclinic zirconium oxide volume ratios (monoclinic ratio) in monoclinic zirconium oxide and cubic zirconium oxide were obtained by plasma spraying. Thermal spraying was performed to determine the monoclinic crystal ratio after thermal spraying. The results are shown in Table 4.

  As in Reference Example 1, when the monoclinic crystal ratio before spraying is 22%, the monoclinic crystal ratio after thermal spraying is 6.5%, and the structural stability in high-temperature steam can be maintained at 5%. Over. On the other hand, when the monoclinic crystal ratio before thermal spraying is 10% as in Reference Example 2, the monoclinic crystal ratio after thermal spraying is 3%, and the structural stability in high-temperature steam can be maintained at 5%. It becomes as follows. Therefore, in order to make the monoclinic crystal ratio after spraying 5% or less, the monoclinic crystal ratio before spraying is preferably 10% or less.

Example 4
As a mock-up specimen, a nozzle diaphragm, which is one type of high-temperature components of a steam turbine, was produced. First, a metal intermediate layer (thickness 0.15 mm) made of a NiCoCrAlY alloy was formed on the surface of a metal substrate made of 12C steel. Thereafter, on the surface of the metal intermediate layer, a general amount of impurities (SiO ₂ : 0.5 mass%, TiO ₂ : 0.1 mass%, Al ₂ O ₃ : 0.08 mass%, Fe ₂ O ₃ : 0 .1 mass%) and 95 mass% solid and spherical zirconium oxide powder stabilized with 8 mass% Y ₂ O ₃ and 5 mass% acrylic polyoxybenzoyl resin powder After the raw material is plasma sprayed to form a resin-containing layer (2 mm) composed of zirconium oxide and a resin, the resin-containing layer is subjected to heat treatment to remove the resin, and the first layer (thickness 2 mm) Formed. The first layer was formed with the goal of obtaining an average porosity of 20% or more. On this first layer, high purity (SiO ₂ : 0.03 mass%, TiO ₂ : 0.02 mass%, Al ₂ O ₃ : 0.004 mass%, Fe ₂ O ₃ : 0.01 mass%) , Total: 0.06% by mass), and plasma sprayed using a zirconium oxide powder stabilized with 8% by mass of Y ₂ O ₃ as a thermal spray material, the second layer (thickness) having an average porosity of 9% 300 μm) was formed. Thereby, a mock-up specimen of a nozzle diaphragm was produced.

(Example 5)
In the formation of the first layer, a general impurity amount (SiO ₂ : 0.5 mass%, TiO ₂ : 0.1 mass%, Al ₂ O ₃ : 0 is used without using acrylic polyoxybenzoyl resin powder. 0.08 mass%, Fe ₂ O ₃ : 0.1 mass%) and plasma sprayed using only a hollow and spherical zirconium oxide powder stabilized with 8 mass% Y ₂ O ₃ as a thermal spray material. A mock-up specimen was prepared in the same manner as in Example 4 except that the first layer was formed. The first layer was formed with the goal of obtaining an average porosity of 20% or more.

(Example 6)
In the formation of the first layer, a general impurity amount (SiO ₂ : 0.5 mass%, TiO ₂ : 0.1 mass%, Al ₂ O ₃ : 0 is used without using acrylic polyoxybenzoyl resin powder. .08 mass%, Fe ₂ O ₃ : 0.1 mass%) and plasma spraying using only solid and spherical zirconium oxide powder stabilized with 8 mass% Y ₂ O ₃ as a thermal spraying raw material Then, a mock-up specimen was prepared in the same manner as in Example 4 except that the first layer was formed. The first zirconium oxide layer was formed with the goal of obtaining an average porosity of 20% or more.

  Next, the mock-up specimens of Examples 4 to 6 were cut, and the porosity was measured at a plurality of locations in the cross section of the first layer. The results are shown in Table 5 together with the configuration of the powder (spraying raw material) used for forming the first zirconium oxide layer.

  As shown in Table 5, the porosity of the first layer in the mockup specimen of Example 4 is 21 to 35%, and the porosity of the first layer in the mockup specimen of Example 5 is 23 to 32. %, The porosity of the first layer in the mock-up specimen of Example 6 was 14-23%.

  As is clear from the above results, the method of removing the resin by heating after mixing and spraying the zirconium oxide powder and the resin powder and the method using the hollow zirconium oxide powder are high in each part of the actual part shape. It is preferable because porosity can be obtained. In particular, a method using a hollow zirconium oxide powder is preferable because variation in porosity in each part is reduced.

  According to the embodiment described above, a thermal barrier coating material for a steam turbine that can be used under high-temperature steam and is excellent in economy is provided.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 10 ... Thermal barrier coating material, 11 ... Metal base material, 12 ... Metal intermediate layer, 13 ... Thermal barrier layer, 14 ... 1st layer, 15 ... 2nd layer, 20 ... Thermal barrier coating material, 21 ... Metal base Material 22 ... metal intermediate layer 23 ... heat shielding layer 24 ... first layer 25 ... second layer 30 ... steam turbine 40 ... casing 41 ... turbine rotor 42 ... rotor disk 43 ... moving Wings, 44 ... Diaphragm outer ring, 45 ... Diaphragm inner ring, 46 ... Stator blade, 47 ... Gland seal part, 48 ... Seal part, 49 ... Crossover pipe.

Claims (8)

A metal substrate;
A metal intermediate layer disposed on the metal substrate;
A first layer disposed on the metal intermediate layer and comprising zirconium oxide;
A second layer disposed on the first layer and comprising zirconium oxide;
The average porosity of the second layer is lower than the average porosity of the first layer;
A thermal barrier coating material for a steam turbine, wherein a proportion by mass of the stabilizer contained in the second layer is higher than a proportion by mass of the stabilizer contained in the first layer. A metal substrate;
A metal intermediate layer disposed on the metal substrate;
A first layer disposed on the metal intermediate layer and comprising zirconium oxide;
A second layer disposed on the first layer and comprising zirconium oxide;
The average porosity of the second layer is lower than the average porosity of the first layer;
A thermal barrier coating material for a steam turbine, wherein a ratio by mass of impurities contained in the second layer is lower than a ratio by mass of impurities contained in the first layer. The first layer has an average porosity of 20% or more, and a volume ratio of monoclinic zirconium oxide to monoclinic zirconium oxide and cubic zirconium oxide exceeds 5%.
The second layer has an average porosity of 10% or less, and a monoclinic zirconium oxide volume ratio to a monoclinic zirconium oxide volume ratio of 5% or less. Item 3. The thermal barrier coating material for steam turbines according to Item 1 or 2. The thermal resistance of the first layer is 1 × 10 ⁻³ m ² K / W or more,
The thermal barrier coating material for a steam turbine according to any one of claims 1 to 3, wherein the thickness of the second layer is 500 µm or less. A method for producing the thermal barrier coating material for a steam turbine according to any one of claims 1 to 4,
Forming a first layer by spraying a thermal spray material having a monoclinic zirconium oxide volume ratio and a monoclinic zirconium oxide volume ratio of monoclinic zirconium oxide of 20% or less; ,
Forming a second layer by spraying a thermal spray material having a volume ratio of monoclinic zirconium oxide to monoclinic zirconium oxide and cubic zirconium oxide of 10% or less; A method for producing a thermal barrier coating material for a steam turbine. A method for producing the thermal barrier coating material for a steam turbine according to any one of claims 1 to 4,
After spraying a thermal spraying raw material containing zirconium oxide and a resin, the resin is removed by heat treatment to form the first layer;
Spraying a thermal spray raw material containing zirconium oxide to form the second layer. A method for producing a thermal barrier coating material for a steam turbine. A method for producing the thermal barrier coating material for a steam turbine according to any one of claims 1 to 4,
Spraying a thermal spraying raw material containing hollow zirconium oxide to form the first layer;
Spraying a thermal spray raw material containing zirconium oxide to form the second layer. A method for producing a thermal barrier coating material for a steam turbine.   A steam generator for power generation comprising the thermal barrier coating material for a steam turbine according to any one of claims 1 to 4.

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