JP2015036518A - Steam turbine constituent component and steam turbine constituent component manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam turbine constituent component excellent in oxidation resistance and erosion resistance and including a surface modified layer that can facilitate reducing film formation time.SOLUTION: A steam turbine constituent component according to an embodiment relates to at least one type of a constituent component selected from a group consisting of a turbine rotor, a moving blade, and a stator blade. The steam turbine constituent component according to the embodiment includes a surface modified layer on a base material. The surface modified layer includes, sequentially from a base material side, an oxide layer and a hard layer formed out of a nitride or a carbide higher in erosion resistance than this oxide layer.

Description

  Embodiments described herein relate generally to a steam turbine component and a method for manufacturing the same.

  In steam turbines of thermal power plants and nuclear power plants, surface roughness increases due to surface oxidation of components such as turbine rotors, moving blades, and stationary blades, and power generation efficiency decreases. In order to suppress surface oxidation, it has been proposed to provide a surface modification layer of about 1.0 to 2.0 μm on the surface of the constituent member. As a film formation method of the surface modification layer, an oxide layer, a nitride layer, a carbide layer, an alloy layer, etc. are formed by vapor phase growth methods such as physical vapor deposition (PVD) and chemical vapor deposition (CVD). A method for forming a film is known. A method of forming an oxide layer by a wet method such as a sol-gel method is also known.

  On the other hand, since the boiler scale, which is dirt in the boiler, is incident on the surface of the component member, the surface modification layer is peeled off by erosion and the power generation efficiency is lowered. In the case of the vapor phase growth method, the erosion resistance can be improved by using a hard material such as nitride or carbide as the constituent material of the surface modification layer. However, it is necessary to form a high vacuum state before forming the surface modified layer. In general, the film formation time tends to be long. For example, the film formation rate of the titanium nitride film by the RF reactive magnetron sputtering method is about 2 nm / min. Therefore, if the thickness is about 2 μm, a film formation time of about 17 hours is required (for example, Non-Patent Document 1). Although a method of nitriding the component itself is also conceivable, transition metal nitrides are not sufficiently chemically stable. For example, iron nitride decomposes at about 200 ° C. Therefore, nitriding is not always suitable as a method for forming the surface modified layer.

  A wet method such as a sol-gel method can be performed under atmospheric pressure, and the film formation time can be shortened as compared with a vapor phase growth method. However, the erosion resistance is low as compared with the vapor phase growth method, and the surface-modified layer that can be formed is easily limited to the oxide layer. Thermal spraying is also known as a method for forming a hard surface-modified layer in a short time. However, since the porosity is generally increased, it is considered that the oxidation resistance and erosion resistance are decreased.

JP 2001-295075 A JP 2006-124830 A JP 2010-156286 A JP 2011-190478 A

Nakano et al., Vacuum, vol.50, No.4, p291-293 (2007)

  An object of the present invention is to provide a constituent member of a steam turbine having a surface modified layer that has good oxidation resistance and erosion resistance and that can easily shorten the film formation time, and a method for manufacturing the same.

  The constituent member of the steam turbine according to the embodiment relates to at least one constituent member selected from a turbine rotor, a moving blade, and a stationary blade. The constituent member of the steam turbine of the embodiment has a surface modification layer on a base material. The surface modification layer has, in order from the substrate side, an oxide layer and a hard layer made of nitride or carbide having higher erosion resistance than the oxide layer.

  The manufacturing method of the structural member of the steam turbine of embodiment is related with the manufacturing method of the at least 1 sort (s) of structural member chosen from a turbine rotor, a moving blade, and a stationary blade. The manufacturing method of the constituent member of the steam turbine according to the embodiment includes a step of forming an oxide layer on a base material of the constituent member, and a nitride or a erosion resistance higher than that of the oxide layer on the oxide layer. Forming a hard layer made of carbide.

  The constituent members of the steam turbine according to the embodiment have a surface-modified layer that has good oxidation resistance and erosion resistance and that can easily shorten the film formation time. Therefore, it is possible to easily manufacture a steam turbine in which the initial blade shape and the surface roughness are maintained for a long time and the power generation efficiency is maintained at a high initial level for a long time.

It is sectional drawing which shows typically one Embodiment of a steam turbine. It is sectional drawing which shows typically one Embodiment of the structural member of a steam turbine.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a cross-sectional view illustrating an embodiment of a steam turbine.
The steam turbine 1 includes a turbine rotor 4, a moving blade (blade) 5 implanted in the turbine rotor 4, a stationary blade (nozzle) 6 disposed on the upstream side of the moving blade 5, and a turbine including them. A casing 13 is provided. The moving blade 5 and the stationary blade 6 disposed upstream thereof constitute one paragraph 7. In addition, a plurality of paragraphs 7 are arranged in the axial direction of the turbine rotor 4 to form a steam passage 8.

FIG. 2 is a cross-sectional view showing components of the steam turbine 1.
A surface modification layer 15 is provided on the base material 14 of at least one component selected from the turbine rotor 4, the moving blade 5, and the stationary blade 6. The surface modification layer 15 includes, in order from the substrate 14 side, an oxide layer 16 and a hard layer 17 made of nitride or carbide having higher erosion resistance than the oxide layer 16. The surface modification layer 15 may be provided on a part of the surface of the substrate 14 or may be provided on the entire surface of the substrate 14.

  According to such a surface modification layer 15, oxidation resistance and erosion resistance are improved, and the film formation time can be easily shortened. That is, the oxide layer 16 can be formed by a wet method such as a sol-gel method. According to a wet method such as a sol-gel method, a film can be formed under atmospheric pressure and can be formed in a shorter time than a vapor phase growth method. Moreover, according to the oxide layer 16, even if the hard layer 17 is oxidatively decomposed, oxygen diffusion to the base material 14 can be suppressed. On the other hand, since the hard layer 17 is made of nitride or carbide having higher erosion resistance than the oxide layer 16, it has better erosion resistance than a conventional surface modification layer made only of an oxide layer. . Therefore, compared to the conventional surface modification layer consisting only of an oxide layer and the surface modification layer consisting only of a hard layer, oxidation resistance and erosion resistance are improved, and the film formation time can be easily shortened. Become. Thereby, the steam turbine 1 in which the initial blade shape and the surface roughness are maintained for a long time and the power generation efficiency is maintained at a high initial level for a long time can be easily manufactured.

  The oxide layer 16 may be made of at least one selected from silicon oxide, titanium oxide, aluminum oxide, and zirconium oxide from the viewpoints of chemical stability, thermal stability, oxidation resistance, and film formability. preferable. Among these, silicon oxide is particularly preferable.

  The thickness of the oxide layer 16 is preferably 0.5 μm or more. When the thickness of the oxide layer 16 is 0.5 μm or more, the base material 14 is uniformly covered, and the oxidation resistance and erosion resistance of the surface modification layer 15 are improved. The total thickness of the oxide layer 16 and the hard layer 17 is preferably 2.0 μm or less. When the total thickness is 2.0 μm or less, generation of cracks is suppressed and oxidation resistance and the like are improved, and peeling from the substrate 14 is also suppressed. Further, the film formation time is shortened and the productivity is improved. The thickness of the oxide layer 16 is particularly preferably 1.5 μm or less.

  The method for forming the oxide layer 16 is not particularly limited, and examples include a thermal spraying method, a physical vapor deposition method (PVD method), a chemical vapor deposition method (CVD method), an ion implantation method, and a wet method. Among these, a wet method is preferable because the deposition time can be shortened and the deposition apparatus is simple. Examples of the wet method include a sol-gel method and a slurry method, and the sol-gel method is particularly preferable.

  In the sol-gel method, an organic compound such as an alkoxide is hydrolyzed and polycondensed in an alcohol solution to form a viscous sol, which is applied to form a gel film, and heated to form the oxide layer 16. Examples of the sol include sols of oxides of silicon, titanium, aluminum, or zirconium. For example, a silicon oxide sol may be obtained by hydrolyzing an organic silicon compound such as a silane coupling agent, methyl silicate, ethyl silicate, propyl silicate, or butyl silicate. The sol is not limited to those obtained from alkoxides.

  In the slurry method, oxide particles are dispersed in a solvent and applied as a slurry, and the solvent is removed by heating to form the oxide layer 16. Examples of the oxide particles include silicon oxide particles, titanium oxide particles, aluminum oxide particles, and zirconium oxide particles.

  As the wet method, in addition to the above method, for example, a solution containing a precursor that generates an oxide (precursor solution) is applied, the precursor is decomposed by heating or the like to generate an oxide, and the oxide A method of forming the layer 16 can be employed. Examples of the silicon oxide precursor include silicates such as sodium silicate, potassium silicate, magnesium silicate, calcium silicate, and barium silicate. Examples of the titanium oxide precursor include titanium metal salts or titanium complexes such as titanium hydrofluoric acid, titanium lactate, titanium tartrate, titanium acetate, titanium chloride oxide, and peroxotitanic acid. Examples of the precursor of zirconium oxide include zirconium metal salts such as zircon hydrofluoric acid, ammonium zirconium carbonate, potassium zircon fluoride, sodium zircon fluoride, basic zirconium carbonate, zirconium nitrate, zirconium acetate, and zirconium chloride oxide, or zirconium complexes.

  Examples of the application method in the wet method include dipping, spraying, spin coating, roll coating, and bar coating. Examples of the heating method include a method of heating the substrate 14 by holding it in an electric furnace, and a method of heating by irradiation with infrared rays or the like. Note that the heating method is not limited to these heating methods.

  The heating temperature can be determined according to the type of wet method, and it is sufficient that the oxide film 16 can be formed by effectively heating the coating film. The heating temperature is preferably 80 to 600 ° C. When the heating temperature is 80 ° C. or higher, the oxide layer 16 can be formed efficiently. Moreover, when heating temperature is 600 degrees C or less, the structural change of the base material 14 is suppressed and declines, such as fatigue strength and creep strength, are suppressed.

  The hard layer 17 is provided on the oxide layer 16 and is made of nitride or carbide having higher erosion resistance than the oxide layer 16. By having the hard layer 17, the erosion resistance is better than when only the oxide layer 16 is provided.

  Examples of the constituent material of the hard layer 17 include silicon carbide, tungsten carbide, and titanium nitride. Further, as a constituent material of the hard layer 17, there can be mentioned a composite nitride containing titanium nitride as a base material and containing at least one element selected from aluminum and silicon. In the case of these constituent materials, the erosion resistance is particularly good. The hard layer 17 preferably has a Vickers hardness of 1000 or more from the viewpoint of erosion resistance. In addition, Vickers hardness is measured by test force: 0.2-1.0N according to the method of JISZ2244.

  The thickness of the hard layer 17 is preferably 0.5 μm or more from the viewpoint of oxidation resistance and erosion resistance of the surface modification layer 15. When the thickness of the hard layer 17 is 0.5 μm or more, the base material 14 is uniformly covered, and the oxidation resistance and erosion resistance of the surface modification layer 15 are particularly good. The total thickness of the oxide layer 16 and the hard layer 17 is preferably 2.0 μm or less. When the total thickness is 2.0 μm or less, generation of cracks is suppressed and oxidation resistance is improved, and peeling from the base material 14 is also suppressed. In addition, the film forming time is shortened, and the film forming property is improved. The thickness of the hard layer 17 is particularly preferably 1.5 μm or less.

  The film formation method of the hard layer 17 is not necessarily limited, but since the dense hard layer 17 having good erosion resistance can be obtained, a physical vapor deposition method (PVD method), a chemical vapor deposition method (CVD method). Etc. are preferred. Examples of the PVD method include a pulse laser deposition method, a deposition method such as an electron beam deposition method, a sputtering method such as a magnetron sputtering method, and an ion plating method. Examples of the CVD method include a plasma CVD method.

  In the above embodiment, the case where the oxide layer 16 and the hard layer 17 are formed as the surface modification layer 15 on the surface of the base material 14 has been described. However, the surface modification layer 15 is not necessarily limited to this. For example, in order to improve the adhesion between the base material 14 and the oxide layer 16, an MCrAlY alloy layer (M is Fe, Ni, and Co) is used as a metal bond coat between the base material 14 and the oxide layer 16. A metal containing at least one of the above. The oxide layer 16 is not limited to a single layer structure, and may be a multilayer structure including two or more oxide layers having different constituent materials. Similarly, the hard layer is not limited to a single layer structure, and may be a multilayer structure having two or more hard layers having different constituent materials.

  As mentioned above, although embodiment was described, these embodiment was shown as an example and is not intending limiting the range of 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.

  A surface modified layer 15 is formed by forming an oxide layer 16 and a hard layer 17 in this order on the base 14 of the turbine rotor 4, the moving blade 5, and the stationary blade 6 in the steam turbine 1 as shown in FIG. 1. Film. Note that a silicon oxide film having a thickness of 1.0 μm is formed as the oxide layer 16 by a sol-gel method. As the hard layer 17, a titanium nitride film having a thickness of 1.0 μm and a Vickers hardness of 1000 or more is formed by RF reactive magnetron sputtering. The film formation by the RF reactive magnetron sputtering method is performed in a nitrogen gas atmosphere using a titanium target.

  The film formation of the silicon oxide film by the sol-gel method is completed within one hour even when coating and heating are combined. On the other hand, the formation of the titanium nitride film by the RF reactive magnetron sputtering method is completed in about 2 hours for evacuation before film formation, about 8 hours for film formation, and about 10 hours in total. Therefore, the total film formation time is about 11 hours. Since the film formation time of the titanium nitride film having a film thickness of 2.0 μm by the RF reactive magnetron sputtering method is about 17 hours, the film formation time can be shortened by about 6 hours in this embodiment. Further, in this embodiment, even if the titanium nitride film as the hard layer 17 is oxidatively decomposed, the silicon oxide film as the oxide layer 16 suppresses oxygen diffusion to the base material 14.

  Further, when the steam turbine 1 of the present embodiment is operated, since a titanium nitride film having a Vickers hardness of 1000 or more is provided as the hard layer 17 on the surface of the constituent member, even if the boiler scale is incident, it is resistant to erosion. Property is improved. Therefore, the initial blade shape and surface roughness can be maintained for a long time, and the power generation efficiency can be maintained at the initial high level for a long time.

  DESCRIPTION OF SYMBOLS 1 ... Steam turbine, 4 ... Turbine rotor, 5 ... Moving blade (blade), 6 ... Stator blade (nozzle), 7 ... Paragraph, 8 ... Steam passage, 13 ... Turbine casing, 14 ... Base material, 15 ... Surface modification Layer, 16 ... oxide layer, 17 ... hard layer

Claims (10)

At least one component selected from a turbine rotor, a moving blade, and a stationary blade in a steam turbine,
The constituent member has a surface modified layer on a base material, and the surface modified layer is, in order from the base material side, an oxide layer and a nitride having higher erosion resistance than the oxide layer or A component of a steam turbine having a hard layer made of carbide.   The thickness of the oxide layer is 0.5 µm or more, the thickness of the hard layer is 0.5 µm or more, and the total thickness of the oxide layer and the hard layer is 2.0 µm or less. The component of the steam turbine of description.   3. The steam turbine component according to claim 1, wherein the oxide layer is made of at least one selected from silicon oxide, titanium oxide, aluminum oxide, and zirconium oxide.   4. The steam turbine component according to claim 1, wherein the oxide layer is formed by a sol-gel method. 5.   The hard layer is made of silicon carbide, tungsten carbide, titanium nitride, or at least one composite nitride selected from aluminum and silicon based on titanium nitride, and has a Vickers hardness of 1000 or more. The constituent member of the steam turbine according to claim 4.   6. The steam turbine component according to claim 1, wherein the hard layer is formed by physical vapor deposition or chemical vapor deposition.   The steam turbine component according to claim 6, wherein the physical vapor deposition method is one selected from a vapor deposition method, a sputtering method, and an ion plating method.   The component of the steam turbine according to claim 6, wherein the chemical vapor deposition method is plasma CVD.   The steam turbine which has the structural member of the steam turbine of any one of Claims 1 thru | or 8. A method for producing at least one component selected from a turbine rotor, a moving blade, and a stationary blade in a steam turbine,
Forming an oxide layer on the base material of the component;
Forming a hard layer made of nitride or carbide having higher erosion resistance than the oxide layer on the oxide layer.

Images