JP2015096638A - Heat resistant member, gas turbine member using the same, and manufacturing method of heat resistant member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat resistant member which has a porous structure capable of blowing out cooling medium from the entire surface, and has a TBC film in which strength reliability of the film is secured.SOLUTION: There is provided a heat resistant member having a thermal barrier coating film formed on a metal base via a bonding layer, which has a structure that the metal base and the bonding layer have through-holes penetrating them, the thermal barrier coating film is a porous body having a large number of voids, the large number of voids are connected via cracks, and gas flowing through the through-holes passes from a bottom part of the thermal barrier coating film to a surface part.

Description

  The present invention relates to a heat resistant member, a gas turbine member using the heat resistant member, and a method for manufacturing the heat resistant member.

  In order to prevent global warming, various industries are actively developing carbon dioxide emission control technology. In the power generation business using gas turbines, it is effective to reduce fuel consumption by increasing the temperature of combustion gas to increase power generation efficiency. Currently, the combustion gas temperature is in the 1300 ° C class, but is expected to rise from 1500 ° C to 1700 ° C in the near future. As the combustion gas becomes higher in temperature, the thermal load on the gas turbine member increases. Therefore, a superalloy having high heat resistance is required for the gas turbine member, and research and development by optimizing the alloy composition and the alloy structure is continuously performed.

On the other hand, the gas turbine member cooling technology is becoming more important in parallel with such metal material development. That is, among the gas turbine members, a moving passage or a stationary blade having a large thermal load has a complicated passage through which a cooling medium flows. Further, a thermal barrier coating (TBC) for thermal insulation from high-temperature combustion gas is provided on the surface. The TBC film is generally made of a ceramic film having a high melting point and low thermal conductivity. The well-known TBC film is partially stabilized by the addition of a lanthanoid oxide such as Y ₂ O ₃ (yttria). ZrO ₂ (zirconia) ceramics (abbreviated as YSZ or PSZ). As a coating method, an atmospheric plasma spraying method (APS) for spraying a material powder or an electron beam physical vapor deposition method (EB-PVD) for depositing a material on an atomic order is used.

  As shown in Non-Patent Document 1 below, the properties and structure of the TBC film have a great influence on the cooling performance of the gas turbine member. Appropriate control of APS and EB-PVD film formation conditions introduces appropriate cracks (vertical and horizontal) inside the film, and technology to control the film's denseness and porosity. (Non-Patent Document 2). That is, the microstructure control of the TBC film is the key to the cooling technology.

MRS BULLETIN, vol. 37, (2012), pp. 891-898. Journal of the Japan Institute of Metals, vol. 71 (No. 1), (2007), pp. 47-54.

  The heat shielding effect on the gas turbine member / blade (metal part) by the TBC film is primarily determined by the film material and its structure. The requirements for the membrane are: (1) the cooling medium (air) that has flowed through the inside of the metal part is blown out through the entire TBC membrane (entire surface), and (2) the TBC membrane is peeled off during turbine operation. It is two points of high structural strength reliability without defects. Therefore, in the study of the TBC film structure, the aim is to solve the problem of “structural strength is high while being porous”. Here, “porous” is classified into two types. One is a low-density state in which the bonds between the YSZ particles forming the TBC film are weak and a large amount of pores enter the inside of the film, and the other is intentionally creating voids (spaces) inside the film. The bond between the YSZ particles introduced and the matrix is strong and the strength is ensured. A desirable form for the TBC film is the state (2). Furthermore, it is desirable that the introduced voids are not independently present but connected.

  In order to form the space inside the TBC film, it is almost impossible with the EB-PVD method described above in principle, and an attempt has been made using a thermal spraying method. Specifically, a method of decomposing and volatilizing by mixing the decomposable organic resin powder with the YSZ powder as the base material, spraying this mixed powder, and heat-treating the organic resin remaining in the TBC film is examined. Has been. The porosity of the TBC film is controlled by the mixing ratio of the raw material powder. However, when hard ceramic powder YSZ and soft organic resin are sprayed at the same time, organic resin particles are scraped by YSZ, so that no voids due to organic resin remain in the film after spraying, and the film becomes dense. . Adjusting the spraying conditions such as the spraying speed, plasma temperature conditions, atmosphere, etc., and trying to leave the resin particles, the spraying conditions inevitably become low speed and low temperature side. The robustness of the YSZ matrix is lost and the strength reliability is lacking. In a technique in which a dense TBC film is formed and a through-hole is vertically formed by mechanical processing in a later process, or in a feather-like structure of a TBC film manufactured in EB-PVD, only the periphery of the through-hole is formed. From the viewpoint of structural reliability, such as a cooling effect is high and the film as a whole is in a non-uniform cooling state and an inevitable thermal stress is applied to the film, a desirable TBC film is produced by such a method. It is difficult. Thus, maintaining the robustness and reliability of the TBC film and simultaneously providing the film itself with a cooling air blowing effect is a technical problem in the high-characteristic TBC coating field.

  In view of the above circumstances, an object of the present invention is to provide a heat-resistant member having a TBC film having a porous structure capable of blowing a cooling medium from the entire surface of the film and ensuring the film strength reliability. It is in.

In one aspect of the present invention, in order to achieve the above object, in a heat resistant member having a thermal barrier coating film formed on a metal substrate via a bonding layer,
The metal substrate and the bonding layer have a through-hole penetrating them,
The thermal barrier coating film is a porous body having a large number of spaces, and the numerous spaces are connected through cracks,
There is provided a heat-resistant member having a structure in which a cooling medium flowing through the through hole passes through the space and the crack from the bottom to the surface of the thermal barrier coating film.

  According to the present invention, it is possible to provide a heat-resistant member having a TBC film having a porous structure capable of blowing a cooling medium from the entire surface and ensuring the film strength reliability. Therefore, by using the heat-resistant member of the present invention, it is possible to provide a gas turbine member that has high cooling performance and high reliability during long-term use.

It is a cross-sectional schematic diagram which shows an example of a part of heat resistant member which concerns on this invention.

(Basic idea of the present invention)
The present inventor is studying various TBC film structures exhibiting efficient cooling capacity, and is porous to the extent that the strength (structure) reliability as the film can be maintained, and the cooling medium is the entire surface of the film. In order to realize this, the structure that blows out uniformly from the outside is good, and in order to achieve this, the space part is intentionally provided in the TBC film, and these space parts are interconnected while maintaining the characteristics of the sprayed film structure. I thought it was important. Maintaining the characteristics of the sprayed film structure is sufficiently reliable in strength, and uses a technique unique to the spraying method that allows the formation of microcracks in the film from the thermal history during film formation. It means that.

  Therefore, as a result of various studies on the thermal spray material composition, the space portion formation method, etc., the present inventor is close to the composition of the TBC film, not the conventional method using the organic resin particles when intentionally providing the space portion. It has been found that by using an inorganic compound, a TBC film having a porous structure capable of blowing cooling air from the entire surface and having a high strength reliability of the film can be produced. The present invention is based on this finding.

  Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the embodiments described here, and can be appropriately combined and improved without departing from the technical idea of the present invention.

(Heat resistant material)
FIG. 1 is a schematic cross-sectional view showing an example of a part of a heat-resistant member according to the present invention. Hereinafter, the heat-resistant member according to the present invention will be described with reference to FIG. As shown in FIG. 1, in the heat-resistant member 10 according to the present invention, a bonding layer (bonding layer: BC layer) 2 made of an alloy having excellent corrosion resistance is formed on the surface of a metal substrate (heat-resistant metal) 1. A through hole 6 serving as a passage for a cooling medium (air or the like) is formed in the metal base 1 and the BC layer 2 by machining so as to penetrate the metal base 1 and the BC layer 2. A thermal barrier coating film (TBC film, topcoat layer) 7 is provided on the surface of the bonding layer 2. The TBC film 7 is a porous body 3 having a large number of space portions 4, and the large number of space portions 4 are connected via minute cracks 5. By having such a structure, the cooling medium flowing through the through-hole can pass (blow out) from the bottom portion to the surface portion of the TBC film 7 through the space portion and the crack. The space 4 of the TBC film 7 is intentionally formed and is different from the pores originally possessed by the porous body 3. The formation method will be described in detail later.

  As the metal base 1, a heat-resistant metal that can be used for a gas turbine member (member such as a turbine blade) is used. Specifically, a Ni-base superalloy known in the art is preferable. However, it is possible to use not only the Ni-base superalloy but also a Co-base alloy that can maintain heat resistance.

  The material composition of the BC layer 2 is preferably a well-known Co (cobalt) -Ni (nickel) -Cr (chromium) -Al (aluminum) -Y (yttrium) alloy, but is not limited thereto. . The type is not limited as long as it has corrosion resistance and heat resistance and can secure the bonding strength with the TBC film 7 (material: ceramics).

  The through hole 6 penetrating the metal base 1 and the BC layer 2 is provided by machining. This is a cooling passage for flowing the cooling medium flowing from the inside of the metal substrate 1. There is no particular limitation on the processing method, and a conventional method can be applied.

The porous body 3 of the TBC film 7 formed on the surface of the BC layer 2 is made of ceramics. As this ceramic layer, conventional YSZ is most proven and preferable. However, instead of Y ₂ O ₃ , it is stabilized with an oxide of a so-called lanthanoid series element, Sc (scandium) oxide, or Hf (hafnium) oxide ( ZrO ₂ added) may be used. Al ₂ O ₃ (alumina) may be used instead of ZrO ₂ . In addition, a pyrochlore type oxide that can be expected to have a low melting point and a high melting point can also be used.

  The volume ratio of the space 4 occupying the porous body 3 is preferably 10% or more and 80% or less, and more preferably 30% or more and 60% or less. The ratio of the space portion 4 is preferably as high as possible from the viewpoint of improving the cooling efficiency, but if it is too high, the structural reliability (strength) of the TBC film 7 is lost. Taking the cooling efficiency and structural reliability of the TBC film 7 into consideration, the ratio of the space 4 is preferably in the above range. In the present invention, the “volume ratio” is a value obtained as a result of image analysis of the SEM observation photograph.

  The space 4 is elliptical as shown in FIG. 1, and preferably has a short side of 10 μm or more and 60 μm or less and a long side of 200 μm or less. The short side is more preferably in the range of 20 μm to 50 μm. When the short side of the space part 4 is larger than 60 μm, the connected body due to the cracks 5 between the space parts 4 is localized in the film, and the internal cooling gas (cooling medium) is uniformly distributed from the entire surface of the TBC film 7. The effect of blowing out may be impaired. If the single side of the space 4 is smaller than 10 μm, the cooling medium cannot be passed efficiently.

  Moreover, it is preferable that the long side of the space part 4 is 200 micrometers or less. When it is larger than 200 μm, the connected body due to the cracks in the spaces is localized in the film, and the effect that the internal cooling gas blows out uniformly from the entire surface of the TBC film may be impaired. In addition, the value of the short side and long side of the space part 4 in this invention is the value calculated | required from the image obtained by electron microscope observation, such as SEM.

  The number, thickness, and length of the microcracks 5 that connect the space portions 4 to each other are not particularly limited. Note that “a large number of the space portions 4 are connected via the cracks 5” means that a sufficient amount of the cooling medium for efficiently cooling the member can pass from the bottom portion to the surface portion of the TBC film 7. Since it is only necessary that the space portions 4 are connected, it is not always necessary that all the space portions 4 are connected by the microcracks 5.

  The surface roughness of the metal substrate 1, the thickness of the bonding layer 2, and the thickness of the TBC film 7 are not particularly limited, and can be freely adjusted according to the purpose. However, the thickness of the TBC film 7 is preferably 300 μm or more in consideration of the heat shielding effect, the formation of the space portion 4 and the structural strength reliability.

  The important point of the present invention is that the TBC film is a porous body having a large number of spaces, but has a film structure that is equal to or better than the dense TBC film in adhesion to the base material and structural strength. It is. That is, it is emphasized that the film structure is controlled while satisfying the conditions required for the conventional TBC film, thereby improving the cooling performance of the substrate.

(Method for manufacturing heat-resistant members)
Next, the manufacturing method of the heat-resistant member which concerns on this invention mentioned above is demonstrated. In the method for producing a heat-resistant member according to the present invention, as a step of forming a TBC film on the BC layer 2 formed on the metal base material 1, (i) particles and a space portion forming material as raw materials for the TBC film 7 A TBC film material preparation step of preparing a TBC film material containing the following: (ii) a sprayed film forming step of spraying the TBC film material on the BC layer 2 to form a sprayed film; and (iii) the sprayed film. A heat treatment step of obtaining a TBC film 7 by heat treatment in a reducing atmosphere.

  As a method for producing the BC layer 2 on the metal substrate 1, a known thermal spraying method (low pressure plasma spraying, high-speed oxygen fuel spraying) can be used, and if adhesion and mechanical strength can be ensured, a forming method is used. There is no particular limitation. The steps (i) to (iii) will be described in detail below.

(I) TBC film material preparation process The TBC film material containing the particle | grains used as the raw material of the TBC film | membrane 7 mentioned above and the space part formation material is prepared. As the particles used as the raw material of the TBC film 7, the above-described YSZ or the like is used. As the space forming material, an inorganic compound is preferably used, and particularly selected from the group of CoO (cobalt monoxide), Cu ₂ O (copper oxide (I)), ZnO (zinc oxide), and SnO ₂ (tin oxide). It is preferable to use at least one kind of inorganic oxide. The space portion forming material is thermally decomposed and sublimated by a heat treatment process described later, and the space portion 4 of the TBC film 7 as shown in FIG. 1 is formed.

As the space forming material, an inorganic compound (such as MgCO ₃ ) other than the inorganic oxide may be applied depending on the heat treatment conditions. The important point is that the structural strength reliability of the TBC film 7 can be ensured without affecting the spraying conditions when mixed with the raw material of the TBC film 7 and sprayed, and further, the metal substrate 1 and the TBC film 7 Any material may be selected as long as the material satisfies the vaporization and volatilization depending on the heat treatment conditions that do not affect. Even if several types are used in combination, the effect of the present invention is not changed.

The particles and the space forming material used as the raw material of the TBC film 7 may be commercially available powders for thermal spraying and granulated powders as raw material powders. Impurity components, typical examples of which may include SiO ₂ (silicon dioxide), Fe ₂ O ₃ (iron oxide (III)), TiO ₂ (titanium oxide), and the like.

(Ii) Thermal spray film forming step The thermal spray film material described above is sprayed on the BC layer 2. As a thermal spraying method, a known thermal spraying method (atmospheric plasma spraying method (APS)) can be used, and there is no particular limitation on the thermal spraying conditions, and the same conditions as those for producing a normal dense YSZ TBC film are applied. can do.

(Iii) Heat treatment process The thermal spray film produced at the said thermal spray film process is volatilized by performing the following heat processing.

That is, heat treatment is performed in a reducing atmosphere at a temperature not exceeding the melting point of the metal substrate 1 with respect to the metal substrate 1 after the sprayed film is formed. During this heat treatment, the space portion forming material described above undergoes thermal decomposition and sublimates as a gas, and that portion becomes the space portion 4. The gas generated during the thermal decomposition is discharged out of the system through cracks present in the sprayed film. Unlike the porous film using an organic resin as in the prior art, the same spraying conditions as when the TBC film 7 is formed by using an inorganic material similar to ZrO ₂ or Al ₂ O ₃ of the TBC film. Therefore, the adhesiveness of the TBC film 7 and the structure (strength) reliability of the porous body (matrix) itself are not adversely affected. The volume ratio of the space portion 4 occupying the porous body 3 is adjusted by the amount of the space portion forming material mixed with the thermal spray material, and the two substantially coincide. Therefore, as described above, in order to make the volume ratio occupying the porous body in the space part 10% or more and 80% or less, the mixing amount of the space part forming material is 10% or more and 80% by volume of the thermal barrier coating film material. % Or less is preferable.

  By the above manufacturing method, a heat-resistant member having a cross-sectional structure as shown in FIG. 1 can be manufactured.

  The heat-resistant member according to the present invention is suitable for a turbine member such as a turbine blade because it has a cooling efficiency and strength balanced at a high level.

  Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited to the following examples.

  In this example, a test sample of the heat-resistant member shown in FIG. 1 was produced, and the structure was observed and the strength was evaluated. As a test metal substrate 1, a Ni-base superalloy (Rene-80 (registered trademark), composition: Ni-14% Cr-4% Mo-4% W-3% Al-5% Ti-9.5% Co (Mass%)), sample size: 5 cm long × 3 cm wide × 3 cm high) and a Co—Ni—Cr—Al—Y alloy (composition: Co-32% Ni-21) as the BC layer 2 on the surface thereof. % Cr-8% Al-0.5% Y, (mass%)) powder was sprayed by plasma spraying in a reduced pressure atmosphere. In addition, blasting was performed for the purpose of improving film adhesion before spraying. The BC layer thickness was 100 μm.

Next, ZnO powder (average particle size of 30 μm) as a space portion forming material was mixed with YSZ powder for spraying (4 mol% Y ₂ O ₃ added partially stabilized ZrO ₂ ) having an average particle size of 40 μm, and the mixture was mixed with a V-type mill for 30 minutes. A mixed raw material powder was prepared and used as a sprayed film material (mixed powder for thermal spraying). The mixing amount of the ZnO powder was 40% by volume of the sprayed film material. This was sprayed onto the BC layer 2 by an atmospheric plasma spraying method. The spraying conditions were a plasma current of 900 A, Ar gas (containing 1% He), and a spraying distance of 75 mm. Each time the plasma torch was swept once, the film thickness was measured with a micrometer. Finally, the thickness of the sprayed film was adjusted to 300 μm.

  The sample obtained above was heat-treated with Ar gas flow (flow rate 300 ml / min) at 900 ° C. for 2 hours to obtain a sample of Example 1.

  As a comparative example, a mixed powder having the same metal substrate 1 and a BC layer and mixed with the same amount (40% by volume) of polyethylene powder (average particle size 100 μm) instead of ZnO powder is prepared in the atmosphere. A sprayed sample was prepared. The spraying conditions were adjusted to a plasma current of 650 A, Ar gas (containing 1% He), and a spraying distance of 150 mm. For the purpose of thermally decomposing polyethylene particles, the comparative sample obtained above was heat-treated in the atmosphere at 600 ° C. for 2 hours to obtain a comparative sample.

  The sample prepared above was cut, mirror-polished, and then observed with a scanning electron microscope (SEM). As a result, inside the TBC film according to the present invention of Example 1, ZnO added as an additive was volatilized, and the portion formed a space. The space portion is an elliptical space due to the lack of flat (elliptical) crystal grains peculiar to the sprayed film, the short side is a maximum of 40 μm, the average is about 25 μm, and the long side is a maximum of 70 μm, the average Then, it was 55 μm. As a result of measuring the volume ratio of the space portion by image analysis, it was found that it was 36% and substantially corresponds to the added ZnO amount.

  As a result of elemental analysis of the TBC film by energy dispersive X-ray analysis (EDX) attached to the SEM, the Zn component was not detected, and only the main components Zr, Y, and O (oxygen) were detected. This shows that ZnO was completely volatilized from the TBC film by the reduction heat treatment in Ar. Observation by SEM revealed that minute cracks exist around the intentionally formed space portion, and the space portions are connected to each other.

  Further, the strength of the TBC film was not peeled off to the extent that it was scratched, and was equivalent to that of a conventional dense TBC film.

  On the other hand, in the TBC film produced as a comparative example, some voids due to the decomposition of the polyethylene particles were observed, but most of the voids did not remain, resulting in a dense TBC (YSZ) film. It is presumed that the conditions of atmospheric plasma spraying were severe, and hard ceramic particles were removed by scraping polyethylene particles during thermal spraying. In another comparative example in which the plasma current was weakened and the thermal spraying conditions were relaxed, the space could be formed, but the bonding strength of the TBC film (matrix YSZ) was weak and incomplete enough to peel off from the substrate when scratched. It only became a film.

A sample for testing a heat-resistant member was produced using the same material as in Example 1 except that Al ₂ O ₃ was used as the TBC film and CoO was used as the inorganic oxide. The average particle diameter of CoO was 25 μm. CoO was mixed with 30% by volume Al ₂ O ₃ to obtain a sprayed film material. Thermal spraying was performed under the same thermal spraying conditions as in Example 1 to form a TBC film having a thickness of 200 μm, and this was heat-treated in Ar at 850 ° C. for 2 hours to obtain a sample of Example 2. When the cross section of the obtained sample was observed with an SEM, an elliptical (flat) space similar to that in Example 1 was formed, the short side being 20 to 30 μm and the long side being 40 to 60 μm. It was. Moreover, the volume ratio of the space part was 23%. Further, the strength of the TBC film did not peel off to the extent that it was scratched, and was equivalent to that of a conventional dense TBC film.

  The gas permeability of the porous TBC sample was examined. The BC / metal substrate used in Example 1 was provided with a 1 mmφ through hole by laser processing. On top of this, the TBC film was sprayed by the same method as in Example 1 and made porous by heat treatment in Ar. As a result of checking the flow rate of air blown from the TBC side by flowing 0.1 MPa dry air from the metal substrate side of the sample thus obtained, it was confirmed that there was a flow rate of 0.2 l / min. On the other hand, in the dense TBC film produced as a comparative example, the amount of air blown out to the TBC side could not be confirmed.

Even when Cu ₂ O and SnO ₂ are used as the space portion forming material, it has been separately confirmed that the same effects as those of the first and second embodiments are obtained.

  As described above, according to the heat-resistant member of the present invention, it has been demonstrated that a heat-resistant member having a TBC film having a porous structure capable of blowing a cooling medium and having high film strength reliability can be provided. It was.

  The above-described embodiments and examples have been described for the purpose of facilitating understanding of the present invention, and the present invention is not limited to the specific configurations described. For example, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. That is, according to the present invention, a part of the configurations of the embodiments and examples of the present specification can be deleted, replaced with other configurations, and added with other configurations.

DESCRIPTION OF SYMBOLS 1 ... Metal base material, 2 ... Bonding layer (bond coat layer), 3 ... Porous body, 4 ... Space part, 5 ... Micro crack, 6 ... Through-hole, 7 ... Thermal barrier coating film, 10 ... Heat-resistant member.

Claims (8)

In a heat-resistant member having a thermal barrier coating film formed on a metal substrate via a bonding layer,
The metal substrate and the bonding layer have a through-hole penetrating them,
The thermal barrier coating film is a porous body having a large number of spaces, and the numerous spaces are connected through cracks,
A heat-resistant member having a structure in which the cooling medium flowing through the through hole passes through the space and the crack from the bottom to the surface of the thermal barrier coating film.   The heat-resistant member according to claim 1, wherein a volume ratio of the space portion occupying the porous body is 10% or more and 80% or less.   The heat-resistant member according to claim 1 or 2, wherein the space portion has an elliptical shape, a short side is 10 µm or more and 60 µm or less, and a long side is 200 µm or less.   The heat-resistant member according to claim 1, wherein the porous body is ceramic. In the method for producing a heat-resistant member having a thermal barrier coating film formed on a metal substrate via a bonding layer,
A thermal barrier coating film material preparation step of preparing a thermal barrier coating film material containing particles and a space forming material as raw materials of the thermal barrier coating film;
A sprayed film forming step of spraying the thermal barrier coating film material on the bonding layer to form a sprayed film;
And a heat treatment step for obtaining the thermal barrier coating film by heat-treating the sprayed film in a reducing atmosphere. 6. The method for manufacturing a heat-resistant member according to claim 5, wherein the space portion forming material is at least one selected from CoO, Cu ₂ O, ZnO, and SnO ₂ .   The method for producing a heat-resistant member according to claim 5 or 6, wherein the mixing amount of the space portion forming material is 10% by volume or more and 80% by volume or less of the thermal barrier coating film material.   A gas turbine member using the heat-resistant member according to any one of claims 1 to 4.

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