JP2016222992A - Thermal barrier coating, thermal barrier member, and steam device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal barrier coating having high heat insulating properties and high corrosion resistance, being free from the occurrence of cracking, peeling, or the like, and being excellent in economical efficiency.SOLUTION: In a thermal barrier coating 1, a plurality of ceramic layers 2 and a plurality of metal layers 3 are alternately laminated, total thermal resistance is 1×10mK/W or more, the surface roughness Ra of a boundary surface between the metal layer and the adjacent ceramic layer is 5 to 100 μm, the ceramic layer 2 contains ceramics selected from zirconium oxide, hafnium oxide, aluminum oxide, titanium oxide, tungsten oxide, chromium oxide, gallium oxide, nickel oxide, magnesium oxide, or mullite, and the metal layer 3 contains a metal selected from nickel, cobalt, iron, chromium, aluminum, zinc, titanium, copper, yttrium or alloys thereof.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a thermal barrier coating, a thermal barrier member, and a steam device.

  In steam equipment in which high-temperature steam is circulated, for example, steam turbines in thermal power generation facilities, the base material of main parts such as turbine rotors and rotor blades has conventionally been ferritic in consideration of economy and manufacturability. Heat resistant steel was used. In recent years, steam turbines using high-temperature steam at about 600 ° C. have been used for the purpose of improving efficiency. When such high-temperature steam is used, the heat resistance of ferritic heat-resistant steel is sufficient. It wasn't. Therefore, in place of the ferritic heat resistant steel, a heat resistant alloy mainly composed of nickel, an austenitic heat resistant steel, or the like has been used.

  In recent years, steam turbines using high-temperature steam at 650 ° C. or higher have been studied for the purpose of further increasing efficiency. When such high-temperature steam is used, there is a limit only by changing the material of the base material, and cooling steam is used to lower the temperature of the base material (Patent Document 1).

By the way, in the field related to gas turbines in which combustion gas circulates, in order to protect a metal substrate such as Ni superalloy from combustion gas exceeding 1000 ° C., yttria (Y _It was coated with a ceramic coating made of zirconium oxide stabilized with ₂ O ₃ ) to enhance the heat shielding property, suppress the temperature rise of the metal base material and improve the corrosion resistance. Further, the ceramic coating is usually produced by a thermal spraying method or the like, but JP-A-2001-226759 discloses a slurry / gel coating using a ceramic precursor for the purpose of smoothing the surface ( Patent Document 2).

JP 2004-353603 A JP 2001-226759 A

  However, the use of cooling steam is not preferable from the viewpoints of economy and ease of design change of a gas turbine or the like. In addition, the ceramic coating has a problem that cracking and peeling from the metal substrate are likely to occur. If the ceramic coating is cracked or peeled off, there is a risk of causing a rapid rise in the metal substrate temperature.

  The present invention has been made to solve the conventional problems as described above, has high heat shielding properties and corrosion resistance, does not cause cracking or peeling, and has excellent economical efficiency. An object is to provide a thermal coating.

  The thermal barrier coating according to the embodiment has a structure in which a plurality of ceramic layers and a plurality of metal layers are alternately stacked.

  According to the present embodiment, it is possible to realize a thermal barrier coating that has high thermal barrier properties and corrosion resistance, is free from cracks and peeling, and is excellent in economic efficiency.

It is a schematic cross section which shows the thermal barrier coating by embodiment. It is a schematic cross section which shows the thermal insulation member by embodiment.

[Thermal barrier coating]
The thermal barrier coating 1 according to the first embodiment has a structure in which a plurality of ceramic layers 2 and a plurality of metal layers 3 are alternately stacked. As will be described later, this thermal barrier coating is provided on the surface of a base material or the like, and has a function of protecting the base material from heat such as water vapor (see FIG. 1). By alternately laminating the ceramic layers 2 and the metal layers 3, a thermal resistance that lowers the heat transfer coefficient is generated at these interfaces, and heat shielding properties can be imparted to the thermal barrier coating. Moreover, since the thermal stress resulting from the difference of the thermal expansion between layers can be reduced, it can be set as the thermal barrier coating which has the outstanding peeling resistance. Furthermore, since the thickness of the thermal barrier coating can be reduced, the economy can be improved.

The thermal barrier coating according to the embodiment has a plurality of interfaces between the ceramic layer and the metal layer. The total thermal resistance at these interfaces is preferably 1 × 10 ⁻⁵ m ² K / w or more, and more preferably 1 × 10 ⁻³ m ² K / W or more. Furthermore, the thermal resistance is preferably less ^{1 m} 2 K / w, more preferably not more than ^{1 × 10 -1 m 2 K /} W. If the total thermal resistance is 1 × 10 ⁻⁵ m ² K / w or more, the ceramic layer has the same thermal resistance as that of the ceramic layer. Therefore, the ceramic layer can be made thin to suppress peeling of the coating. The upper limit of the total thermal resistance is not particularly specified, but if the thermal resistance exceeds 1 m ² K / w, it is considered that the interface contact state is not good, and problems such as easy peeling occur. ^It is preferable to make it ² K / w or less. The thermal resistance is represented by “interface thickness / thermal conductivity”, and the thermal conductivity can be measured by a steady heat flow method, a flat plate heat flow method, a laser flash method, or the like.

  In the embodiment, the surface layer (hereinafter referred to as “the innermost surface layer” in some cases) in contact with the metal substrate or the like of the thermal barrier coating is preferably a metal layer from the viewpoint of reducing thermal stress. Further, the surface layer (hereinafter, sometimes referred to as “outermost surface layer”) in contact with high-temperature water vapor is preferably a ceramic layer from the viewpoint of thermal stability.

In the embodiment, the difference between the thermal expansion coefficient of the metal layer and the thermal expansion coefficient of the ceramic layer adjacent to the metal layer, that is, directly laminated, is 1 × 10 ⁻⁸ to 1 × 10 ⁻⁴ . It is preferably 1 × 10 ⁻⁸ to 1 × 10 ⁻⁶ . The thermal expansion coefficient can be measured by a contact type or non-contact thermal dilatometer.

  Although the thickness of the whole thermal barrier coating can be appropriately changed according to its use, it can be set to, for example, 10 μm to 10,000 μm.

  The thermal barrier coating according to the embodiment has a structure in which a plurality of metal layers to be described later and a plurality of ceramic layers to be described later are laminated. The number of metal layers and ceramic layers to be laminated is generally 2 or more, and preferably 3 or more. As the number of layers stacked increases, the interface increases and the heat shielding effect tends to increase. On the other hand, in order not to make the overall thickness of the thermal barrier coating excessively, the number of metal layers and ceramic layers to be laminated is generally 50 layers or less, preferably 10 layers. That's it.

  In the embodiment, the method for producing the ceramic layer and the metal layer constituting the thermal barrier coating is not particularly limited. However, it can be produced, for example, by spraying a material described later using a plasma spraying method or the like. In another embodiment, the ceramic layer and the metal layer can also be produced using a vapor deposition method such as an EB-PVD method. The thermal barrier coating can be produced by sequentially laminating a metal layer and a ceramic layer produced by these methods.

  The thermal barrier coating according to the present embodiment includes a plurality of ceramic layers. The ceramic layer can comprise a ceramic selected from the group consisting of zirconium oxide, hafnium oxide, aluminum oxide, titanium oxide, tungsten oxide, chromium oxide, gallium oxide, nickel oxide, magnesium oxide, and mullite. Of these, zirconium oxide and hafnium oxide are more preferred, and zirconium oxide is particularly preferred because of its low thermal conductivity and excellent heat resistance. The ceramic layer may contain one or more of the ceramics. The thermal barrier coating can also have a combination of different ceramic layers, including different materials. In the present invention, the ceramic means a metal oxide, nitride or carbide, or a composite thereof. In the present embodiment, the ceramic layer may contain a part of metal.

In addition, the ceramic layer has a yttria (Y ₂ O ₃ ), a ceria (Ce ₂ O ₃ ), a calcia (CaO), a magnesia (MgO), and a ytterbia (Tb ₂ O ₃ ) from the viewpoint of thermal expansion and accompanying peeling prevention. ), Scandia (Sc ₂ O ₃ ), lanthanum (La ₂ O ₃ ), and other lanthanoid oxides or actinide oxides, and the like. Therefore, it is more preferable to include yttria. In the embodiment, the content of the stabilizing material in the ceramic layer is preferably 0.1 to 10% by weight, and more preferably 0.3 to 1% by weight.

  The porosity of the ceramic layer is preferably 1 to 35%, and more preferably 10 to 30%. If the porosity of the ceramic layer is within the above numerical range, the thermal resistance and mechanical strength of the ceramic layer can be improved. The porosity of the ceramic layer is determined by the ratio of the void volume to the total volume of the ceramic layer.

  The thickness of the ceramic layer is preferably 10 μm to 5000 μm, and more preferably 100 μm to 3000 μm. The thickness of the plurality of ceramic layers may or may not be the same. Here, the thickness of the ceramic layer refers to the average thickness of the ceramic layers formed on the flat portion.

  In the embodiment, a composite ceramic layer including a plurality of ceramic layers in which different ceramic layers are directly laminated can be used. In such a composite ceramic layer, thermal resistance also occurs at the interface between the ceramic layers. However, the thermal resistance in that case is generally smaller than the thermal resistance at the interface between the metal layer and the ceramic layer. In the embodiment, such a composite ceramic layer is treated as a single ceramic layer for convenience.

  The thermal barrier coating according to the present embodiment includes a plurality of metal layers. The metal layer can comprise a metal selected from the group consisting of nickel, cobalt, iron, chromium, aluminum, zinc, titanium, copper, yttrium, and alloys thereof. Among these, from the viewpoint of heat resistance, it is preferable to contain nickel, cobalt or iron, and from the viewpoint of corrosion resistance, it is preferable to contain chromium or aluminum, and these alloys are more preferable. . The thermal barrier coating can also have a combination of different metal layers, including different metals. In the present invention, the metal means a single metal composed of a single metal element and a plurality of metal elements or an alloy of a metal element and a non-metal element. In the present embodiment, the metal layer may include a part of ceramics in which the metal is oxidized.

  In the embodiment, the metal layer includes an M—Cr—Al—Y alloy (M is at least one element selected from Fe, Ni, and Co). The chromium content is preferably 10 to 35% by weight, the aluminum content is preferably 0.1 to 20% by weight, and the yttrium content is 0.1 to 5% by weight. It is preferred that the balance consists of iron, nickel and / or cobalt.

  In the embodiment, the metal layer can be formed, for example, by spraying the above-described metal particles on the surface of the base material or the surface of the ceramic layer, and the average particle diameter is preferably 5 μm to 500 μm, More preferably, the thickness is 10 μm to 300 μm. The “average particle size” means the volume average particle size and is measured by a known method using a particle size distribution / particle size distribution measuring device (for example, Nanotrack particle size distribution measuring device, manufactured by Nikkiso Co., Ltd.). can do.

  The thickness of the metal layer is preferably 10 μm to 500 μm, and more preferably 100 μm to 300 μm. The thicknesses of the plurality of metal layers may or may not be the same. Here, the thickness of the metal layer means an average thickness of the metal layers formed on the flat portion.

  In the embodiment, it is also possible to use a composite metal layer in which different metals are directly laminated similarly to the composite ceramic layer.

  When the thermal barrier coating according to the present embodiment is practically used, the temperature of the layer on the side in contact with the substrate and the layer on the side in contact with the high-temperature water vapor are different and a temperature gradient is generated. Yes. Therefore, it is preferable that the metal layer on the side in contact with the substrate having a relatively low temperature has high anticorrosion properties in a low temperature range (about 500 ° C. or less). Increasing the corrosion resistance in such a low temperature range can be achieved, for example, by increasing the concentration of metallic chromium constituting the metal layer. Specifically, the chromium concentration of the metal layer is preferably 5 to 40% by mass, and more preferably 10 to 30% by mass. On the other hand, it is preferable that the metal layer on the side in contact with the high-temperature water vapor on the opposite side to the layer on the side in contact with the substrate or the like has high anticorrosion properties in a high temperature range (about 650 ° C. or higher). In order to increase the corrosion resistance in such a high temperature range, for example, it can be achieved by increasing the concentration of metal aluminum constituting the metal layer. Specifically, the aluminum concentration of the metal layer is preferably 2 to 20% by mass, and more preferably 3 to 15% by mass.

  In the thermal barrier coating in the embodiment, the interface between one metal layer and the adjacent ceramic layer is generally not completely smooth. The surface roughness Ra of the metal layer at such an interface is preferably 5 μm to 100 μm, and more preferably 10 μm to 50 μm. The thermal barrier coating according to the embodiment has a plurality of interfaces between a ceramic layer and a metal layer. Of these, the surface roughness of at least one interface may be in the above range, but the surface roughness of all interfaces is preferably in the above range. When the surface roughness Ra of the metal layer is within the above numerical range, an appropriate proportion of pores may be formed between the metal layer and the ceramic layer, and the adhesion between the metal layer and the ceramic layer is sufficient. Thus, the thermal resistance can be further improved. The surface roughness of the metal layer can be adjusted by subjecting the surface to surface treatment such as blasting or changing the particle diameter of the metal particles used for metal layer preparation. The surface roughness Ra can be measured with a contact-type surface roughness meter or the like according to JIS B0601: 2001.

[Heat shield]
The heat shield member 10 according to the second embodiment includes a base material 11 and a heat shield coating 1 formed on the surface thereof (see FIG. 2).

  The substrate is not particularly limited, and zirconium oxide, hafnium oxide, aluminum oxide, titanium oxide, tungsten oxide, chromium oxide, gallium oxide, nickel oxide, magnesium oxide, mullite, or other ceramics, or nickel, cobalt, iron, chromium, It may be made of aluminum, zinc, titanium, copper, yttrium, or an alloy thereof.

  By using steam equipment such as a turbine rotor, nozzles, moving blades, nozzle box, or steam supply pipe used in the steam turbine as a metal material, the above-described thermal barrier coating is formed on the surface thereof. It can be a thermal member.

  The present invention will be described below using specific examples. It goes without saying that the present invention is not limited to these examples.

Example 1
On one surface of a metal substrate (12Cr steel), particles (average particle diameter of 50 μm) of Ni-21Cr-10Al-0.8Y alloy (numbers represent% by weight) were sprayed by plasma spraying to obtain a thickness. A metal layer having a thickness of 150 μm was formed, and then zirconium oxide particles (average particle diameter of 70 μm) stabilized with 8 wt% yttria (Y ₂ O ₃ ) were sprayed on the metal layer by plasma spraying. Thus, a ceramic layer was formed. The same operation was repeated, and three layers of ceramic layers and metal layers were alternately laminated to a thickness of 500 μm to produce a heat shield member. In addition, according to JIS B0601: 2001, surface roughness Ra in the surface which contact | connects the ceramic layer of each metal layer was 10 micrometers as a result of measuring using the contact-type surface roughness meter. The total thermal resistance of the thermal resistance at the interface between the metal layer and the ceramic layer was 1 × 10 ⁻³ m ² K / W.

(Example 2)
Example except that after forming each metal layer and before forming the ceramic layer, the surface of the metal layer was sandblasted using sandblasting having an average particle diameter of 250 μm and the surface roughness Ra was adjusted to 20 μm. In the same manner as in Example 1, a heat shielding member was produced. Further, when the thermal resistance at the interface was measured in the same manner as in Example 1, the total thermal resistance was 1 × 10 ⁻² m ² K / W.

(Comparative Example 1)
One surface of a metal substrate (12Cr steel) was sprayed with particles of Ni-21Cr-10Al-0.8Y alloy (numbers represent weight%) (average particle diameter of 50 μm) by plasma spraying to obtain a thickness. A 150 μm metal layer was formed. Next, zirconium oxide particles (average particle diameter of 100 μm) stabilized with 8 wt% yttria (Y ₂ O ₃ ) were sprayed on the metal layer by plasma spraying to form a ceramic layer having a thickness of 3 mm. The heat shielding member was produced by laminating. About the obtained heat-shielding member, when the thermal resistance in an interface was measured like Example 1, the total thermal resistance was 1.2 * 10 ^<-2 > m ^{< 2} > K / W.

<< Corrosion resistance test >>
The heat shield members obtained in Examples 1 and 2 and Comparative Example 1 were maintained at 750 ° C. in an atmospheric pressure and saturated steam environment. The occurrence of peeling of the thermal barrier coating over time was observed with the naked eye. The evaluation criteria were as follows.
The evaluation criteria were as follows. The evaluation results are as shown in Table 1 below.
A: Even after 5000 hours, the thermal barrier coating did not peel off.
B: Peeling of the thermal barrier coating occurred in 2000 hours or more and less than 5000 hours.
C: Peeling of the thermal barrier coating occurred in less than 500 hours.

<< Heat shielding test >>
The heat shield members obtained in Examples 1 and 2 and Comparative Example 1 were heated and held at 750 ° C. for 30 minutes at atmospheric pressure, and then cooled in water at 20 ° C. This was repeated and the occurrence of peeling of the thermal barrier coating was observed with the naked eye. The evaluation criteria were as follows. The evaluation results are as shown in Table 1 below.
A: Peeling of the thermal barrier coating did not occur even after 200 cycles or more.
B: The thermal barrier coating peeled off at 50 cycles or more and less than 200 cycles.
C: The thermal barrier coating peeled off in less than 50 cycles.

  According to at least one embodiment described above, it is possible to realize a thermal barrier coating that has high thermal barrier properties and corrosion resistance, is free from cracking and peeling, and is excellent in economy.

  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 1 ... Thermal barrier coating 2 ... Ceramics layer 3 ... Metal layer 10 ... Thermal barrier member 11 ... Metal base material

Claims (9)

  A thermal barrier coating characterized by having a structure in which a plurality of ceramic layers and a plurality of metal layers are alternately laminated. The thermal barrier coating according to claim 1, wherein the total thermal resistance is 1 × 10 ⁻⁵ m ² K / W or more.   The thermal barrier coating according to claim 1, wherein the metal layer has a surface roughness Ra of 5 μm to 100 μm at an interface with an adjacent ceramic layer.   The ceramic layer comprises a ceramic selected from the group consisting of zirconium oxide, hafnium oxide, aluminum oxide, titanium oxide, tungsten oxide, chromium oxide, gallium oxide, nickel oxide, magnesium oxide and mullite. The thermal barrier coating according to any one of 3 above.   5. The metal layer according to claim 1, wherein the metal layer comprises a metal selected from the group consisting of nickel, cobalt, iron, chromium, aluminum, zinc, titanium, copper, yttrium, and alloys thereof. The thermal barrier coating according to claim 1.   A thermal barrier member comprising the thermal barrier coating according to any one of claims 1 to 5 and a base material.   The heat shield member according to claim 6, wherein the innermost surface layer of the thermal barrier coating is a metal layer and is directly laminated on the base material.   The heat shield member according to claim 6 or 7, wherein the outermost surface layer of the thermal barrier coating is a ceramic layer.   A steam apparatus comprising the thermal barrier coating according to any one of claims 1 to 5.

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