JP2011167994A - Heat-resistant member having thermal barrier coating and gas turbine component using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a TBC having sufficient durability and reliability in an operation for a long period of time at a melted-salt corrosive environment using a low-grade fuel. <P>SOLUTION: A heat-resistant member has a thermal barrier coating having a heat shield layer 12 formed of a ceramic provided thereon, via a bonding layer 11 formed of an alloy on the surface of a heat-resistant alloy base material 10 containing Ni, Co or Fe as principal components. The thermal barrier coating layer comprises the heat shield layer 12 formed of a porous ceramic, and a dense environmental shielding layer 13 comprising silica containing a ceramic fiber 17 provided thereon as a principal component. Furthermore, there is an impregnated layer 14 impregnated with a part of a substance containing the silica of the environmental shielding layer 13 as a principal component in pores 15 of the porous ceramic heat shield layer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat-resistant member having a thermal barrier coating made of ceramics used in gas turbine high-temperature components such as turbine rotor blades and combustors, and particularly for gas turbine components operated under severe conditions of high-temperature corrosion environments. The present invention relates to a heat resistant member having a thermal barrier coating.

  The operation temperature of gas turbines is increasing year by year for the purpose of improving efficiency. In order to cope with such high temperatures, some of the high-temperature parts of the gas turbine are provided with a thermal barrier coating (hereinafter referred to as TBC) made of ceramics on the surface for the purpose of reducing the temperature of the parts. Things have been done.

  In a gas turbine high-temperature part subjected to TBC, the temperature of the part can be suppressed lower than in the case where TBC is not applied due to the heat shielding effect of TBC. It is often used for moving blades and combustors. Although it depends on the use conditions, it is generally said that the substrate temperature can be reduced by 50 to 100 ° C. by applying TBC, and it is very effective to apply TBC to the gas turbine high-temperature parts.

  In general, TBC forms partially stabilized zirconia having low thermal conductivity and excellent heat resistance as a heat shielding layer through a MCrAlY alloy layer having excellent oxidation resistance on a base material (for example, , See Patent Document 1). Here, M represents at least one selected from the group consisting of iron (Fe), Ni, and Co, Cr represents chromium, Al represents aluminum, and Y represents yttrium.

  Conventionally, in gas turbines, relatively high-grade fuels such as liquefied natural gas (LNG), kerosene, and light oil have been used as fuels from the viewpoint of combustibility and corrosion prevention. These fuels have very low contents of corrosion factors such as sulfur (S) and ash. Generally, S is not more than 0.01% by mass, almost no ash is contained, and high-temperature parts are rarely damaged by corrosion. . For this reason, in the TBC of the prior art, there are problems in improving the heat resistance to cope with the high temperature of the combustion gas, and dealing with particle wear (erosion) mainly caused by oxide solid particles contained in the combustion gas. It was said. For example, Patent Document 2 discloses a method in which a dense protective layer is provided on the surface of a porous TBC excellent in heat resistance for the purpose of improving erosion resistance.

JP-A-62-211387 JP-A-9-78258

  However, in recent years, the use of low-grade fuels such as heavy oil has been increasing in gas turbines from the viewpoint of soaring fuel prices and resource conservation, and low sulfur A heavy oil (LSA heavy oil), which has relatively low sulfur and ash content, is the medium. It is mainly used for small gas turbines. Further, there is a high demand for using lower grade high sulfur A heavy oil and B, C heavy oil as fuel. However, these fuels contain corrosion factors such as alkali metals (Na, K) and vanadium (V) in sulfur and ash.

  For example, according to Japanese Industrial Standard (JIS) K2205 “heavy oil”, low sulfur A heavy oil (Type 1 No. 1 heavy oil) has S of 0.5% or less, ash content of 0.05% or less, high sulfur A heavy oil (1 In Type 2 heavy oil), S is 2.0% or less, ash content is 0.05% or less, in B heavy oil (Type 2 heavy oil), S is 3.0% or less, ash content is 0.05% or less, C heavy oil (3 In Type 1 heavy oil), S is specified to be 3.5% or less and ash content is 0.1% or less, and in some low-quality heavy oils, there is no provision for S and ash content. . These corrosion factors react in a complex manner with each other or with oxygen (O), sea salt particles (NaCl, etc.) in the combustion air in the combustion gas, and generate various compounds that cause high temperature corrosion.

  In particular, a compound having a relatively low melting point among these is known to cause severe high-temperature corrosion by condensing and adhering to the surface of a high-temperature part, and is called so-called molten salt corrosion.

It is known that heat-resistant alloys used for gas turbine high-temperature parts are also severely corroded by molten salt corrosion, which is a major problem when using low-grade fuel. This is because a protective oxide film such as chromia (Cr ₂ O ₃ ) or alumina (Al ₂ O ₃ ) formed on the surface of the heat-resistant alloy and contributing to oxidation resistance and corrosion resistance is dissolved in the molten salt.

  A similar mechanism also results in molten salt corrosion damage to TBC partially stabilized zirconia. In particular, in an environment where S is contained in the fuel in an amount exceeding 0.5% and V exceeds 0.01%, the partially stabilized zirconia used as a heat shield layer is damaged by molten salt corrosion in the TBC of the prior art. It is easy to peel off in a short time.

  The object of the present invention is to overcome the problem that the TBC of the prior art is easily damaged by molten salt corrosion, and has sufficient durability even in long-term operation in a molten salt corrosion environment using low grade fuel. It is to provide a TBC having reliability.

That is, the heat-resistant member of the present invention includes a base material made of a heat-resistant alloy containing Ni, Co, or Fe, a bonding layer made of the alloy, and made of an alloy, and provided on the bonding layer. A heat-resistant member having
The thermal barrier coating includes a thermal barrier layer made of porous ceramics, and a dense environmental shield layer that is provided on the thermal barrier layer and includes silica containing ceramic fibers, and the porous ceramics It is characterized by having an impregnation layer impregnated with a part of the substance containing silica of the environmental shielding layer in the pores of the heat shielding layer.

  The high corrosion resistance TBC according to the present invention is superior in corrosion resistance and heat resistance in harsh molten salt corrosive environments as compared to the TBC of the prior art. Therefore, when operating a gas turbine using low grade fuel, durability and reliability of high temperature parts There is an advantage that the performance is improved. In addition, since the gas turbine can be operated using inexpensive low-grade fuel, the fuel cost of the gas turbine can be kept low. Furthermore, the durability and reliability of the high-temperature parts are improved, so that it is possible to set a longer period for replacement and inspection of high parts, and it is possible to keep the operating cost of the gas turbine low.

It is a cross-sectional schematic diagram of the heat-resistant member by the Example of this invention. It is a perspective view of the turbine rotor blade provided with TBC by this invention.

  The heat-resistant member of the present invention has a thermal barrier coating in which a thermal barrier layer made of ceramics is provided on the surface of a heat-resistant alloy substrate mainly composed of Ni, Co, or Fe via a bonding layer made of an alloy. The thermal barrier coating layer is composed of a thermal barrier layer made of porous ceramics and a dense environmental shielding layer mainly composed of silica containing ceramic fibers provided thereon, and further porous In the pores of the ceramic heat shield layer, there is an impregnated layer impregnated with a part of the substance mainly composed of silica of the environmental shield layer.

  Thereby, the environmental shielding layer mainly composed of silica, which is reinforced by containing ceramic fibers, prevents contact between the molten salt and the ceramic thermal insulation layer, and prevents corrosion of the ceramic thermal insulation layer. it can.

  At the same time, part of the environmental shielding layer composed mainly of silica containing ceramic fibers is impregnated in the pores of the porous stabilized zirconia layer, so that high adhesion between them can be obtained. The porous thermal barrier layer existing under the layer exhibits a thermal stress relaxation function, thereby enabling a thermal barrier coating with high corrosion resistance and excellent heat resistance.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram schematically showing a cross section of a heat-resistant member according to an embodiment of the present invention.

  As shown in FIG. 1, the heat-resistant member of the present invention is made of porous stabilized zirconia on the surface of a heat-resistant alloy substrate 10 mainly composed of Ni, Co, or Fe via a bonding layer 11 made of an alloy. An environmental shielding layer 13 containing high-temperature corrosion composed mainly of silica, which contains ceramic fibers 17, is provided on the surface of the thermal shielding layer 12. The impregnated layer 14 is provided in which the part is impregnated in the pores 15 of the heat shield layer 12 made of porous stabilized zirconia.

  As the heat-resistant alloy base material 10 mainly composed of Ni, Co, or Fe, various heat-resistant alloys used in gas turbine rotor blades, stationary blades, combustors, and the like can be used.

  The bonding layer 11 made of an alloy has a thermal expansion coefficient intermediate between the heat-resistant alloy base material 10 and the heat-shielding layer 12 made of porous stabilized zirconia, and more than the base material. It is preferable to use an alloy having excellent corrosion resistance and oxidation resistance. For example, an alloy composed essentially of Ni and Co and consisting of Cr and Al is desirable. Furthermore, Y, Hf, Ta, Si, Ce, etc. can be included in the range of 0 to 10% by weight (wt)% as additive elements. In particular, MCrAlY alloy, which is generally used as a TBC bonding layer, is also preferably used as the bonding layer of the present invention.

  The bonding layer 11 is most preferably formed by a low pressure plasma spraying method, but a high-speed gas spraying method such as an HVOF spraying method or an HVAF spraying method can also be used. The thickness of the bonding layer 11 is preferably in the range of 0.05 to 0.3 mm.

The thermal barrier layer 12 made of porous stabilized zirconia is preferably made of ZrO ₂ ceramics, particularly Y ₂ O ₃ , MgO, CaO, CeO ₂ , Sc ₂ O ₃ , Er ₂ O ₃ , Gd. A partially stabilized zirconia containing at least one selected from ₂ O ₃ , Yb ₂ O ₃ , Al ₂ O ₃ , SiO ₂ , and La ₂ O ₃ is desirable. Yttria (Y ₂ O ₃ ) partially stabilized zirconia is very suitable. The thermal barrier layer 12 made of porous stabilized zirconia is most preferably formed by an atmospheric plasma spraying method.

  The thickness of the thermal barrier layer 12 made of porous stabilized zirconia is preferably in the range of 0.1 to 1 mm. If the thickness is less than 0.1 mm, sufficient heat shielding property as TBC cannot be obtained. On the other hand, if it is 1 mm or more, the heat resistance is lowered and peeling tends to occur.

  The porosity of the thermal barrier layer 12 made of porous stabilized zirconia is preferably in the range of 10 to 30% in the area ratio occupied by the pores 15 in the cross-sectional structure. If the porosity is less than 10%, the thermal stress relaxation mechanism due to the pores does not sufficiently act and the heat resistance is lowered. On the other hand, when the porosity is 30% or more, the mechanical strength of the film is lowered and peeling tends to occur.

  The environmental shielding layer 13 maintains a film without reacting or dissolving even when it comes into contact with the molten salt, and the molten salt passes through the environmental shielding layer 13 and is formed of porous stabilized zirconia underneath. The layer 12, the bonding layer 11 made of an alloy, and the heat-resistant alloy base material 10 are brought into contact with each other and function to prevent them from being corroded.

For this reason, it is preferable that the environmental shielding layer 13 is made of silica (SiO ₂ ) having excellent corrosion resistance, containing ceramic fibers 17 and having enhanced crack resistance. In molten salt corrosion with a fuel containing sulfur, alkali metal sulfates (for example, Na ₂ SO ₄ , K ₂ SO _4, etc.) tend to condense and adhere to the surface of the high-temperature component as a molten salt. At the same time, it is affected by other compounds present and the environment of the atmosphere, but these have properties as acidic salts, so they react and dissolve with amphoteric oxides such as alumina and chromia, and basic oxides such as zirconia and yttria. Causes molten salt corrosion. However, since silica with high purity is an acidic oxide, it does not easily react with molten salt and exhibits excellent durability against molten salt corrosion. Therefore, a quartz glassy material having a silica purity of 90% or more is most suitable for the environmental shielding layer 13. If the purity of silica is less than 90%, the corrosion resistance against molten salt corrosion decreases due to the influence of impurities and the like.

The ceramic fiber 17 contained in the environmental shielding layer 13 is preferably a silica-based, alumina-based, or silicon carbide-based fiber from the viewpoint of heat resistance, and any one or a mixture of these can be used. In particular, silica-based and silicon carbide-based fibers are preferred because they have the same Si as the matrix (matrix phase) silica (SiO ₂ ) as the main component, and thus have excellent fiber-matrix consistency.

  The diameter of the ceramic fiber 17 is preferably 20 μm or less and the length is preferably 2 mm or less, more preferably in the range of 1 to 10 μm in diameter and 0.01 to 1 mm in length. If the diameter of the fiber is large, it becomes difficult to disperse it uniformly in a thin film, and the function of enhancing crack resistance cannot be obtained sufficiently. On the other hand, if the diameter of the fiber is too thin, the fiber strength is reduced and the fiber is easily aggregated and uniform dispersion becomes difficult, so that the crack resistance strengthening function cannot be sufficiently obtained.

  The content of the ceramic fiber 17 in the environmental shielding layer 13 is preferably 5 to 40%, more preferably 10 to 30% in terms of volume fraction. When the content is too low, the crack resistance strengthening function cannot be sufficiently obtained. On the other hand, if the content is too high, uniform dispersion becomes difficult, and gaps are likely to be formed between the fibers, and not only a sufficient crack resistance strengthening function cannot be obtained, but also the gaps between the fibers are made of molten salt. It becomes a passage and the environmental shielding is reduced.

  The porosity of the environmental shielding layer 13 composed mainly of silica is preferably 5% or less. When the porosity exceeds 5%, the open pores increase, and the molten salt easily penetrates and passes through the environmental shielding layer 13 through the pores.

  The thickness of the environmental shielding layer 13 on the surface of the heat shielding layer 12 made of porous stabilized zirconia is preferably in the range of 0.05 to 0.2 mm. If the thickness is less than 0.05 mm, sufficient shielding property as an environmental shielding layer cannot be obtained. On the other hand, when the thickness is 0.2 mm or more, cracks are likely to occur due to residual stress or thermal stress at the time of film formation, and the shielding property through the cracks and the environmental shielding layer are likely to be peeled off.

  Examples of the method for forming the environmental shielding layer 13 containing the ceramic fiber 17 as a main component made of silica include silica such as a sol-gel method using an alcohol solution of a metal alkoxide, a colloidal silica solution, and an alkali metal silicate solution. Using a solution containing the precursor, an appropriate amount of ceramic fiber 17 is mixed therein, and this is sufficiently stirred to uniformly disperse the ceramic fiber 17 in the solution, followed by coating, drying and firing to form a film. A process can be used. A commercially available silica-based coating agent can be used as long as the finally formed silica has corrosion resistance to the molten salt as long as the influence of additives and impurities is acceptable.

  Further, when a solution containing these silica precursors is used and applied, when the solution is applied to the thermal barrier layer 12 made of porous stabilized zirconia by appropriately adjusting the viscosity of the solution in advance. In addition, it is possible to penetrate into the pores 15 in the heat shield layer, a part of which is made of porous stabilized zirconia, by capillary action. The infiltrated solution is dried and fired, and solidifies in the pores 15 in the heat shielding layer made of porous stabilized zirconia to form silica. As a result, an impregnated layer 14 is formed in which a part of the environmental shielding layer 13 made of silica is impregnated in the pores 15 of the heat shielding layer 12 made of porous stabilized zirconia. By providing the impregnation layer 14, the adhesion between the environmental shielding layer 13 and the heat shielding layer 12 made of porous stabilized zirconia can be improved, and peeling of the environmental shielding layer 13 can be prevented.

The thickness of the impregnation layer 14 is preferably in the range of 0.01 to 0.1 mm, and is preferably about 10 to 20% with respect to the thickness of the thermal barrier layer 12 made of porous stabilized zirconia. When the impregnated layer 14 is thin, the adhesion between the environmental shielding layer 13 and the heat shielding layer 12 made of porous stabilized zirconia becomes insufficient. Further, when the impregnated layer 14 is thick, the porosity of the heat shield layer 12 made of porous stabilized zirconia is substantially reduced, and the heat shielding property of the heat shield layer 12 is lowered or the thermal stress relaxation function is lowered by the pores. It becomes easy to cause peeling.
〔Example〕
A gas turbine rotor blade provided with the TBC of the present invention was produced. A perspective view showing the overall configuration of the gas turbine rotor blade is shown in FIG.

  In FIG. 2, this gas turbine blade is made of a Ni-based heat-resistant alloy (Rene 80), and is used, for example, as a first-stage blade of a rotating portion of a gas turbine having three stages of blades. It has a shank 63, a seal fin 64, and a chip pocket 65, and is attached to the disk via a dovetail 66. The blade has a blade length of 100 mm and a length of 120 mm after the platform portion 42. The blade is cooled by a cooling hole (not shown) through which a cooling medium, in particular, air or water vapor passes so that the blade can be cooled from the inside. ) From the dovetail 66 through the wing 61. Although this TBC blade is most excellent in the first stage, it can also be provided in the latter stage blade after the second stage. And TBC of this invention was formed in the blade | wing part 61 and the platform part 62 which are exposed to combustion gas among this gas turbine moving blade.

The formation method uses a CoNiCrAlY alloy (Co-32 wt% Ni-21 wt% Cr-8 wt% Al-0.5% Y) powder, forms a base layer by plasma spraying in a reduced pressure atmosphere, and performs diffusion heat treatment. A heat treatment of 1121 ° C. × 2 h + 843 ° C. × 24 h was performed in vacuum. The thickness of the tie layer is about 200 μm. Thereafter, using a yttria partially stabilized zirconia (ZrO ₂ -8 wt% Y ₂ O ₃ ) powder on a base material provided with a bonding layer, the thickness is about 0.5 mm by air plasma spraying, and the porosity is about A 20% porous ceramic coating layer was provided.

  Furthermore, as a solution containing a silica precursor on the surface, a product name “Aron Ceramic C” manufactured by Toa Gosei Co., Ltd., which is commercially available as a ceramic adhesive and filler, has a diameter of about 10 μm and a length of about 0.5 mm. While adding 15% by weight of silica-based fiber and mixing with a stirrer, an appropriate amount of water was further added, and the viscosity was adjusted to about 3 Pa · sec at room temperature. After coating, it was naturally dried at room temperature for 24 hours.

  Thereafter, the test blade is further heated to about 90 ° C. × 1 h and 150 ° C. × 1 h in an electric furnace, so that the surface of the porous ceramic coating layer is an environmental shielding layer mainly composed of silica containing alumina fibers. Formed. As a result of cross-sectional observation of a small test piece prepared in the same procedure in advance, the thickness of the environmental shielding layer was about 0.15 mm, and the thickness of the impregnation layer was about 0.05 mm. Further, the environmental shielding layer contained silica fibers uniformly dispersed in a volume fraction of about 20%.

  In order to verify the durability of the gas turbine rotor blade provided with the high corrosion resistance TBC of the present invention produced in this way, an actual machine test was carried out in a gas turbine operated using special A heavy oil as fuel. . In the gas turbine that has been subjected to the operation test, damage due to molten salt corrosion has already been recognized in the TBC blade of the prior art.

  For comparison, a moving blade provided with a TBC according to the prior art, in which only the bonding layer and the heat-shielding layer are constructed, and the environment-shielding layer is not provided, in the same manner as the above-described high corrosion-resistant TBC of the present invention is produced. Was also prepared and used for testing at the same time.

  When the test blades were observed after two years of operation, the gas turbine rotor blade provided with the high corrosion resistance TBC of the present invention was sound without any TBC damage. On the other hand, in the moving blade provided with the comparative prior art TBC, it was recognized that the TBC heat shield layer was locally peeled off. The thermal barrier layer was mechanically peeled off from the peeled portion and collected, and the cross section of the thermal barrier layer was analyzed. As a result, S and V were detected, and the peeling was considered to be due to molten salt corrosion.

  From the above results, it was confirmed that the gas turbine rotor blade provided with the high corrosion resistance TBC of the present invention was superior in durability as compared with the gas turbine rotor blade provided with the conventional TBC.

  The heat-resistant member having the high corrosion-resistant TBC of the present invention has very excellent durability in a corrosive environment. For this reason, it is suitable as a TBC for moving blades, stationary blades, and combustors of gas turbines. Moreover, it can be applied not only to a gas turbine but also to an aircraft engine.

DESCRIPTION OF SYMBOLS 10 Heat-resistant alloy base material 11 Bonding layer 12 Heat shielding layer 13 Environmental shielding layer 14 Impregnation layer 15 Pore 16 Thermal spray particle 17 Ceramic fiber 21 Wing part 22 Platform part 23 Shank part 24 Seal fin 25 Chip pocket 26 Dovetail

Claims (10)

A base material made of a heat-resistant alloy containing Ni, Co or Fe;
A bonding layer disposed on the substrate and made of an alloy;
A thermal barrier coating disposed on the bonding layer;
A heat-resistant member having
The thermal barrier coating includes a thermal barrier layer made of porous ceramics, and a dense environmental shield layer that is disposed on the thermal barrier layer and includes silica containing ceramic fibers, and the porous ceramics A heat-resistant member having an impregnated layer impregnated with a substance containing silica of the environmental shielding layer in pores of the heat shielding layer. The heat-resistant member according to claim 1,
The heat-resistant member, wherein the heat shielding layer is made of zirconia. The heat-resistant member according to claim 1,
The heat-resistant member, wherein the ceramic fiber in the environmental shielding layer is at least one selected from alumina, silica and silicon carbide. The heat-resistant member according to claim 1,
The heat-resistant member, wherein the environmental shielding layer has a thickness of 0.05 to 0.2 mm. The heat-resistant member according to claim 1,
A heat-resistant member, wherein the porosity of the environmental shielding layer is 5% or less. The heat-resistant member according to claim 1,
The heat-resistant member, wherein the heat shielding layer has a thickness of 0.1 to 1 mm. The heat-resistant member according to claim 1,
The heat-resistant member, wherein the heat shielding layer has a porosity of 10 to 30%. The heat-resistant member according to claim 1,
The heat-resistant member, wherein the impregnated layer has a thickness of 0.01 to 0.1 mm. The heat-resistant member according to claim 1,
The environmental shielding layer is formed using a solution containing a silica precursor mixed with ceramic fibers.   A gas turbine component using the heat-resistant member according to any one of claims 1 to 9.

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