JP2017025781A - Geothermal steam turbine nozzle and manufacturing method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a geothermal steam turbine which: can be used for a long period by improving corrosion resistance of a geothermal turbine nozzle, reducing scale attaching to and accumulating on the nozzle and enhancing scale removal performance to peel attached scale; and can have a long service life.SOLUTION: A geothermal steam turbine nozzle comprises a covering layer containing a resin material with ceramic particles dispersed therein at least at a portion of a contact site between a geothermal steam turbine nozzle and geothermal fluid. The covering layer has a gradient composition of the ceramic particles with a content rate thereof gradually decreased with increasing depth from a surface section to a deep section.SELECTED DRAWING: Figure 3

Description

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

  A geothermal steam turbine is a system in which steam (geothermal steam) heated by underground magma is led to the ground by drilling a well, and this steam is directly introduced into the turbine to become a working fluid to obtain rotational force. is there.

FIG. 1 shows an outline of a typical geothermal steam turbine.
In the geothermal steam turbine 1 of FIG. 1, the geothermal energy introduced into the geothermal steam turbine 1 as geothermal steam from the steam inlet 2 is a turbine stage in which the geothermal steam is composed of the turbine stationary blade 3 (turbine nozzle 30) and the turbine rotor blade 4. Is expanded into velocity energy, and the geothermal steam having this velocity acts on the turbine blade 4 to generate a force for rotating the turbine rotor shaft 5 in which the turbine blade 4 is implanted. generate. Thereafter, the steam is discharged from the steam outlet 6.

  In general, geothermal steam is generated when groundwater is heated by geothermal heat such as magma, so it contains corrosive components such as hydrogen sulfide and salt, scale components such as silica and calcium, and sand and mud. Contains solid particles such as iron oxide.

  Further, since the geothermal steam is in a saturated state or a state close to the saturated state, the wetness of the steam is high inside the turbine, and the geothermal steam turbine is forced to be operated severely.

  Furthermore, the type and concentration of chemical components contained in the geothermal steam, the size and amount of solid particles brought into the geothermal steam turbine, and the steam state of the geothermal steam depend on the geothermal zone and well where the geothermal steam turbine is installed. In addition, the same well will change greatly over time, and in the newly established well, the type and concentration of chemical components contained in the geothermal steam, and the size and amount of solid particles brought into the geothermal steam turbine It is very different from wells used over time, and it has been confirmed that the wells were most prominent at the beginning of the well, making the design of geothermal steam turbines more complicated.

  The fact that corrosive gas such as hydrogen sulfide is contained in the geothermal steam is a factor that facilitates the preparation of an environment in which scale components such as silica and calcium are easily deposited and deposited due to rough skin caused by the overall corrosion of the material. In particular, the paragraph at the inlet of the geothermal steam turbine shows an example where the corrosive environment is active and the skin is prone to corrosion and pitting corrosion, resulting in severe rough skin.

JP 2004-270484 A

  There are various methods for preventing scale adhesion of geothermal steam turbine nozzles, but it is necessary to significantly modify the structure of the geothermal turbine nozzle, and the cost of remodeling is high and the expected effect is not necessarily obtained. It was hard to say.

  An embodiment of the present invention is a geothermal steam turbine nozzle that has a structure similar to the conventional one without greatly changing the structure of the geothermal steam turbine nozzle, and that can easily remove scale accumulated on the surface of the geothermal steam turbine nozzle during periodic inspection. It is to provide.

  In general, in order to operate a geothermal steam turbine for a long period of time with high efficiency, it is possible to carry out relatively easy inspection and maintenance work that can be performed at the place where the turbine is installed, and to disassemble the turbine internal mechanism. Both relatively large-scale inspection / maintenance work involving replacement, renewal, etc. is required. For example, confirmation of turbine nozzle scale adhesion and simple scale removal work can be performed by the turbine operator (for example, a power generation company, etc.) at the location where the turbine is installed. Often done. On the other hand, the latter large-scale inspection / maintenance work is difficult for the turbine operator to carry out on their own due to the required technical level and facilities, so the factory, for example, under the control of the turbine manufacturer, etc. Etc. are often performed.

  Even if the turbine operator carefully removes the scale, the scale can be completely removed, or the turbine nozzle itself can be completely repaired by degrading or damaging it to restore the initial performance of the turbine nozzle. Is not easy. Therefore, these operations are generally performed during a large-scale inspection / maintenance operation. Here, when a coating layer is provided on the surface of the turbine nozzle, the renewal operation of the coating layer (that is, the operation of removing the deteriorated coating layer and the operation of forming a new coating layer) is usually performed on a large scale.・ It will be done during maintenance work.

  However, as far as the present inventors know, the conventional coating layer has been developed mainly for the purpose of improving durability and coating strength, or the deteriorated coating layer has a complicated and precise surface shape. Removal from existing turbine nozzles has not always been easy.

  Normally, geothermal steam turbine nozzles are used for a long time in a high-temperature, high-pressure, humid atmosphere and in the presence of chemical substances such as silicon that also cause scale. Is inevitable. Therefore, it is not easy to achieve the durability in such severe operating conditions as well as the peelability of the coating layer after use.

  The embodiment of the present invention has been made in consideration of the above-described circumstances, and has been used over a long period of time by improving the corrosion resistance of the geothermal steam turbine nozzle, reducing the amount of scale that adheres and deposits, and improving the delamination removal property after adhesion. It is an object of the present invention to provide a geothermal steam turbine that has been made possible and to provide a geothermal steam turbine that has a long life.

  In the embodiment of the present invention, the coating film deteriorated by the operation of the turbine can be easily removed, and even when the coating film is used again for the operation of the turbine, good scale adhesion prevention, scale removability and durability are achieved. It is an object of the present invention to provide a geothermal steam turbine nozzle having a property and the like and a manufacturing method thereof.

Therefore, in the geothermal steam turbine nozzle according to the embodiment of the present invention, the geothermal heat is formed by forming a coating layer containing a resin material in which ceramic particles are dispersed in at least a part of a contact portion of the geothermal steam turbine nozzle with the geothermal fluid. A steam turbine nozzle,
The coating layer has a gradient composition in which the content of the ceramic particles decreases from the surface portion toward the deep layer portion.

And the manufacturing method of the geothermal steam turbine nozzle by embodiment of this invention is the base material of a geothermal steam turbine nozzle,
It is characterized in that at least one coating layer having a gradient composition, which is made of a resin material in which ceramic particles are dispersed and whose content of the ceramic particles decreases from the surface portion toward the deep layer portion, is formed.

  A geothermal steam turbine nozzle according to an embodiment of the present invention has a coating film that facilitates exfoliation and removal after scale adhesion and withstands impact wear caused by solid particles flying together with a geothermal medium. It can be said that the value of is extremely high.

  In such an embodiment of the present invention, it is possible to easily remove the scale from the conventional hammering and grinder removal method, for example, by hammering alone, and the geothermal heat that has no influence on the nozzle base material such as damage. A steam turbine nozzle is provided.

  The geothermal steam turbine nozzle according to the embodiment of the present invention is formed with a coating layer having a gradient composition in which the content of the ceramic particles decreases from the surface portion toward the deep layer portion. A resin layer substantially free of ceramic particles is formed on the contact surface with the turbine nozzle substrate. From this, it is easy to peel the coating layer from the geothermal steam turbine nozzle base material, and it is suppressed that the coating layer remains on the base material surface of the geothermal steam turbine nozzle. Therefore, it is easy to peel the deteriorated coating layer from the base material of the geothermal steam turbine nozzle, and it is easy to form a new coating layer again after peeling and removing the coating layer.

  And the geothermal steam turbine nozzle by embodiment of this invention is formed with the coating layer which has the gradient composition in which the content rate of the said ceramic particle is decreasing toward the deep layer part from the surface part. As a result, the occurrence of stress based on the difference in thermal expansion coefficient, etc. is suppressed, and stress relaxation within the coating and impact from the outside can be mitigated. Occurrence is suppressed. In particular, since a resin layer substantially free of ceramic particles is formed on the contact surface with the geothermal steam turbine nozzle base material, this resin layer functions effectively as a shock absorbing or stress relaxation layer and is coated. The durability and erosion resistance of the entire layer are remarkably improved.

  Moreover, according to the manufacturing method of the geothermal steam turbine nozzle by embodiment of this invention, the coating layer which has a predetermined gradient composition can be formed easily and efficiently. For example, in brush painting and spray coating by hand, it was not easy to form a coating layer having a predetermined gradient composition at the necessary location of the geothermal steam turbine nozzle, but the spraying process is easier than before. And a predetermined coating layer can be formed efficiently. According to such a manufacturing method, it is easy to form a coating film that is homogeneous and tough, and has excellent erosion resistance, scale adhesion prevention and scale removal properties, which could not be obtained by brush coating or spray coating. Can get to.

The figure which shows the outline | summary of a geothermal steam turbine. The schematic diagram of the passage part of the geothermal fluid of a geothermal steam turbine. The schematic diagram which shows the cross-section of the geothermal steam turbine nozzle by preferable embodiment of this invention. The figure which shows the erosion weight loss of a coating layer. The figure which shows the steam turbine nozzle used for evaluation of peeling removal property. The figure which shows the steam turbine nozzle used for evaluation of solid particle erosion resistance.

<Geothermal steam turbine nozzle>
A geothermal steam turbine nozzle according to an embodiment of the present invention is a geothermal steam turbine in which a coating layer containing a resin material in which ceramic particles are dispersed is formed at least at a part of the geothermal steam turbine nozzle in contact with a geothermal fluid. A nozzle,
The coating layer has a gradient composition in which the content of the ceramic particles decreases from the surface portion toward the deep layer portion.
Here, the “turbine nozzle” means “a steam outlet for converting steam energy into velocity energy”.

  A geothermal steam turbine nozzle according to an embodiment of the present invention holds a plurality of turbine stationary blades 3 as shown in FIGS. 1 and 2, for example. The space between the turbine stationary blades 3 is used as a geothermal fluid passage or jet outlet. A typical geothermal steam turbine nozzle has a structure in which a large number of turbine vanes 3 arranged along the diameter direction of the diaphragm are sandwiched between an outer ring and an inner ring of the diaphragm.

  In the geothermal steam turbine 1, a plurality of turbine nozzles (30 to 36) are disposed inside the turbine casing 7 and fixed thereto.

  Since the plurality of stationary blades 3 provided in one turbine nozzle 30 shown in FIG. 2 form a partition wall of the geothermal fluid flow path, the surface of each stationary blade 3 is in contact with the geothermal fluid, respectively. It is a part.

  The “contact portion with the geothermal fluid” in the geothermal steam turbine nozzle according to the embodiment of the present invention includes a geothermal fluid flow path, typically the surface portion of the stationary blade 3 as described above, and the outer ring and diaphragm of the diaphragm. The “contact portion with the geothermal fluid” in the inner ring is included.

  In the stationary blade 3 shown in FIG. 2, the region X on the inflow side (upstream side) of the geothermal fluid is a geothermal fluid or particles mixed in the geothermal fluid (for example, solid particles such as water droplets, mud and rock powder). Is a region where erosion tends to proceed in general. On the other hand, the region Y on the outflow side (downstream side) of the geothermal fluid of the turbine nozzle is a region where the deposition of the scale 8 easily proceeds. In addition, the arrow 9 in FIG. 2 has shown the rotation direction of the turbine rotor.

  For this reason, the coating layer of the turbine nozzle is required to have wear resistance against erosion, prevention of adhesion to the scale, and ease of removal of the scale.

  The geothermal steam turbine nozzle according to the embodiment of the present invention can take functions, purposes, and forms as a turbine nozzle similar to the turbine nozzles 30 to 36 of FIGS. 1 and 2, for example, as described above. Erosion resistance against erosion, adhesion prevention to scale and ease of removal of scale are compatible.

  The geothermal steam turbine nozzle according to the embodiment of the present invention can easily remove the deteriorated coating film, and has a good scale even when the turbine is operated again after forming the coating film again. The anti-adhesion property, the removal property, the durability and the like are achieved.

<Resin material>
The resin material that forms the coating layer contains an epoxy resin or a polyester resin. The resin material preferably has high heat resistance. For example, since the geothermal steam temperature is 280 ° C., it is preferable to use a resin material having a heat resistance of 250 ° C. or higher.

<Ceramic particles>
Ceramic particles are dispersed in the resin material forming the coating layer. As the ceramic particles, for example, those selected from the group consisting of carbides and oxides of Cr, W, Ti, Nb, and Al can be used. Preferably, carbides such as Cr ₃ C ₂ , WC, TiC, and NbC are used. One or more kinds of ceramic particles selected from oxides such as Cr ₂ O ₃ and A ₂ O ₃ can be used. Among these, WC, Cr ₃ C ₂ and TiC are particularly preferable.

The ceramic particles preferably have a maximum diameter of 25 μm or less, particularly preferably a maximum diameter of 20 μm or less. If the particle diameter is 25 μm or less, it is spherical, but if the particle diameter exceeds this, it often becomes polygonal and tends to cause cracks in the coating layer. Therefore, it is preferable that among the ceramic particles, the number of particles having a particle size exceeding 25 μm is smaller. Accordingly, the proportion of particles having a particle size exceeding 25 μm is preferably 10% by weight or less, and particularly preferably 5% by weight or less.
And it is preferable that the particle size of ceramic particles is 5-25 micrometers.

<Coating layer>
FIG. 3 is a diagram schematically showing a cross-sectional structure of a specific example of the geothermal steam turbine nozzle 30 and the coating layer 10 according to a particularly preferred embodiment of the present invention.

The geothermal steam turbine nozzle according to the embodiment of the present invention whose cross section is shown in FIG. 3 has a coating layer 10 made of a resin material in which ceramic particles R are dispersed at least at a part of the geothermal steam turbine nozzle in contact with the geothermal fluid. A geothermal steam turbine nozzle formed,
The coating layer 10 has a gradient composition in which the content of the ceramic particles R decreases from the surface portion A toward the deep layer portion B.

  The coating layer 10 shown in FIG. 3 has a gradient composition whose composition fluctuates in the thickness direction of the coating layer 1 within the range where the abundance of the ceramic particles is 0 to 80% by weight. The thickness of the coating layer 10 is preferably 75 to 100 μm, particularly preferably 120 to 140 μm.

  The coating layer 10 specifically shown in FIG. 3 is composed of six resin layers (layers 11 to 16) having different ceramic particle content rates. In the coating layer 10 of the present invention, the resin layer The number is not limited.

  The coating layer 10 of the present invention only needs to have a gradient composition as a whole of the coating layer 10. Even if the coating layer 10 has a gradient composition in which the blending ratio of ceramic particles continuously changes, the blending of ceramic particles The composition may have a gradient composition in which the ratio changes stepwise (that is, the composition ratio of the ceramic particles changes stepwise at the boundary of each layer).

  Here, although the layers 11 to 16 forming the covering layer 10 are expressed as “layers”, the boundary lines of these layers are not always clearly distinguished. In particular, generally, when each layer is formed by thermal spraying of the same kind of material, it is normal that the boundary between the layers cannot be clearly distinguished. From this, the layers 11 to 16 can be regarded as “regions” in which the content of ceramic particles changes stepwise or continuously and the boundary is clear or unclear.

  The layer 11 formed in the deepest part of the coating layer 10 and in contact with the base material 17 of the geothermal steam turbine nozzle has a ceramic particle content of preferably 0 to 20% by weight, particularly preferably 0% by weight. It is. That is, it is preferable that the resin layer has a small content of ceramic particles or no ceramic particles. When the content of the ceramic particles exceeds 20% by weight, the adhesion between the resin layer 11 and the interface 17 of the geothermal steam turbine nozzle substrate 17 is lowered. Here, as the base material 17 of the geothermal steam turbine nozzle, the stationary blade 3, the outer ring of the diaphragm holding the stationary blade 3, the inner ring of the diaphragm, and the like are targeted.

  The thickness of the resin layer 11 formed in the deepest part of the coating layer 10 is preferably 20 to 50 μm, particularly preferably 20 to 40 μm. If the thickness of the resin layer 11 is less than 20 μm, the film is thin and the adhesiveness with the base material is too high, which may cause a problem in peelability. On the other hand, when it exceeds 50 μm, the resin layer 11 tends to break and the coating layer tends to remain.

  On the other hand, the layer 16 formed on the surface portion of the coating layer 10 is a layer having the highest content of ceramic particles in the entire coating layer 10. The content of ceramic particles in the layer 16 is preferably 40 to 80% by weight, particularly preferably 50 to 80% by weight. When the content of the ceramic particles is less than 40% by weight, the effect of improving the heat resistance and wear resistance by the ceramic particles may not be sufficiently obtained. A higher ceramic particle content is preferable because the heat resistance and wear resistance of the coating layer 10 are improved. However, when the ceramic particle content exceeds 80% by weight, the adhesive function of the resin coating may be lowered. is there.

  The thickness of the layer 16 is arbitrary, and can be appropriately determined in consideration of, for example, the heat resistance, wear resistance, crack resistance, life and the like of the coating film 10. For example, it is preferable to set the thickness so that sufficient functions and effects are maintained until the next large-scale inspection / maintenance work (detailed above). Therefore, the thickness of this layer 16 is preferably 20 to 50 μm, particularly preferably 20 to 40 μm.

  Each of the layers 12 to 15 in the coating layer 10 is a layer having a smaller ceramic particle content than the layer 16 and a higher ceramic particle content than the layer 11. Has a gradient composition in which the content of the ceramic particles decreases from the surface portion A toward the deep layer portion B ”.

  For example, when the content of ceramic particles in the layer 16 is 80% by weight and the content of ceramic particles in the layer 11 is 0% by weight, the layer 15 is about 70% by weight, and the layer 14 is about Is about 60% by weight, the layer 13 is about 50% by weight, and the layer 12 is about 40% by weight. The thickness of each of the layers 12 to 15 can be determined as appropriate.

  Note that none of these layers 12 to 15 is essential in the coating layer 10 according to the embodiment of the present invention. Therefore, it is possible to omit any one or more of these layers 12 to 15 or all of the layers 12 to 15.

  When any or all of these layers 12 to 15 are unnecessary, the thickness of the layer 16 formed on the surface portion of the coating layer 10 can be made larger than the above value as necessary. For example, when the layers 12 to 15 are not present, the thickness of the layer 16 can be preferably 40 to 80 μm, particularly preferably 40 to 100 μm.

  A gradient composition layer having a composition variation within a range of 40 to 80% by weight of the ceramic particles having a thickness of 40 to 100 μm is provided on the surface portion side, and a thickness of 20 to A 40 μm geothermal steam turbine nozzle having a coating layer having a resin layer in which the ceramic particles are not present corresponds to a specific example of a particularly preferred geothermal steam turbine nozzle of the present invention.

  The total thickness of the coating layer 10 and the thickness of each layer in the coating layer 10 do not have to be uniform in the entire region of the geothermal steam turbine nozzle, and can be partially different. For example, when there is a place where erosion occurs or progresses locally, the total thickness of the covering layer 10 or the thickness of one of the layers (particularly preferably the layer 16) is increased accordingly. It is preferable to make it.

<Production method of geothermal steam turbine nozzle>
A method for manufacturing a geothermal steam turbine nozzle according to an embodiment of the present invention includes:
For the base material of the geothermal steam turbine nozzle,
A coating layer comprising a resin material in which ceramic particles are dispersed and having a gradient composition in which the content of the ceramic particles decreases from the surface portion toward the deep layer portion,
At least one layer is formed.

  Here, details of the geothermal steam turbine nozzle, ceramic particles, resin material, coating layer having a gradient composition, and the like are as described above.

  The base material of the geothermal steam turbine nozzle is made of a metal material such as 12CrMoV, for example, similarly to the conventional geothermal steam turbine nozzle. The base material of the geothermal steam turbine nozzle preferably has an average surface roughness Ra of 12.5 μm or less.

  In the manufacturing method of the geothermal steam turbine nozzle according to the embodiment of the present invention, it is preferable that the coating layer is formed by thermal spraying.

  According to such a thermal spraying process, the coating layer having the predetermined gradient composition can be easily and efficiently formed. For example, by brushing or spraying by hand, it has not been easy to form a coating layer having a predetermined gradient composition at the necessary location of the geothermal steam turbine nozzle, but it is easier than before by spraying. And a predetermined coating layer can be efficiently formed. In addition, according to the thermal spraying treatment, it is possible to easily obtain a coating film that is homogeneous and tough and has excellent erosion resistance, scale adhesion prevention and removability, which could not be obtained by brush coating or spray coating. be able to.

  The method for forming the coating layer by thermal spraying is arbitrary. In the method for manufacturing a geothermal steam turbine nozzle according to an embodiment of the present invention, the coating layer is preferably formed of a plurality of sprayed layers, each formed by a plurality of sprayed materials having different amounts of ceramic particles in the resin material, for example. It can be formed by accumulation. Particularly preferably, a plurality of thermal spray materials having different ceramic particle content rates in the resin material are prepared, and the thermal spray materials are formed in order from the thermal spray material having the lower ceramic particle content rate to the higher thermal spray material. A coating layer having a gradient composition can be obtained by performing thermal spraying a plurality of times so as to overlap each thermal spray layer.

<Removal of coating layer>
The coating layer of the geothermal steam turbine nozzle according to the embodiment of the present invention has a gradient composition, and the contact interface between the coating layer and the geothermal steam turbine nozzle base material is a resin layer substantially free of ceramic particles. Since it is formed, it is easy to peel the coating layer from the geothermal steam turbine nozzle base material, and it is suppressed that the coating layer remains on the base material surface of the geothermal steam turbine nozzle.

  Therefore, in the embodiment of the present invention, the covering layer can be peeled and removed easily and in a short time by using, for example, a chisel, a hammer or the like.

<Example 1> (Evaluation of peelability)
After the surface of the substrate was blasted, an epoxy resin was sprayed to create “Sample 1” in which a resin layer was formed on the surface of the substrate. About this, heating aging was performed for a long time in the electric furnace which simulated the geothermal steam temperature of 270 degreeC, and the peeling removal property of the coating layer was confirmed.

  “Sample 2” was prepared in the same manner as described above except that a polyester resin was used instead of the epoxy resin. “Sample 3” and “Sample 4” were prepared in the same manner as described above except that carbide ceramics or oxide ceramics were used instead of the epoxy resin.

For these “Sample 2” to “Sample 4”, the peelability of the coating layer was confirmed in the same manner as described above.
The results are as described in Table 1.

  The ceramic coating layer has high adhesion strength due to mechanical bonding and cannot be easily peeled off from the substrate. However, the resin coating layer does not deteriorate the coating layer even after heating for 10,000 hours, It was easy to peel off from.

<Example 2> (Evaluation of adhesion (part 1))
Since the mechanical bonding force greatly affects the film peelability, the adhesion strength and peel resistance of the coating layers of the above “Sample 1” to “Sample 4” were evaluated by a test using an adhesive.
The results are as described in Table 2.

  When the adhesion strength is 70 MPa or more, the mechanical bonding force is high and cannot be easily peeled off from the substrate. On the other hand, the adhesive strength of the resin coating layer is 40 MPa or less, and it can be easily peeled and removed from the substrate due to the low adhesive strength.

<Example 3> (Evaluation of adhesion (part 2))
After the surface of the base material was blasted, an epoxy resin was sprayed to prepare a sample in which a resin layer having a thickness of 10 μm, 20 μm, 40 μm or 70 μm was formed on the surface of the base material.

Moreover, after blasting the surface of the base material, a polyester resin was sprayed to prepare a sample having a resin layer having a thickness of 10 μm, 20 μm, 40 μm or 70 μm formed on the surface.
The resin layer was formed by setting the film thickness per pass by thermal spraying to 10 μm and repeating thermal spraying until the target thickness was reached.
The adhesion and peel resistance of the coating layer were evaluated by a peel test using an adhesive.
The results are as described in Table 3.

  When the film thickness is 10 μm, there is a problem in peelability because the film is thin and the adhesion to the substrate is good. When the film thickness is 20 to 40 μm, it is not affected by the base material and can be easily peeled off. However, when the film thickness is increased to 70 μm, peeling occurs at the center of the film, and the film remains. It was confirmed that 20 to 40 μm is the best as a strippability.

<Example 4> (Evaluation of solid particle erosion resistance (part 1))
Thermal spraying was performed on the surface of the nozzle plate base material using an epoxy resin having a ceramic content of 40% to prepare a sample in which a resin layer was formed on the surface of the base material. About this, the erosion resistance was evaluated by colliding particle | grains.

  Further, thermal spraying was performed using an epoxy resin having a ceramic content of 60% or 75% to prepare a sample in which a resin layer was formed on the substrate surface, and the erosion resistance was similarly evaluated.

  In addition, by performing thermal spraying using a polyester resin instead of an epoxy resin, a “sample” having a ceramic content of 40%, 60% or 75% on the surface and having a resin layer formed thereon is prepared. Similarly, the solid particle erosion resistance was evaluated.

Table 4 shows the solid particle erosion resistance when ceramics are added to the outer layer. The application of the resin coating as a binder is confirmed.

  The numerical values of the solid particle erosion resistance in the above table are those when the erosion loss of the nozzle plate substrate is represented as 1. As for the solid particle erosion characteristics of the coating layer, erosion resistance was not recognized at all with the resin coating alone, but it was confirmed that the erosion resistance was drastically improved by adding ceramics.

<Example 5> (Evaluation of solid particle erosion resistance (part 2))
Thermal spraying was performed on the surface of the nozzle plate base material using a resin having a ceramic (WC) content of 75% to prepare a sample in which a resin layer was formed on the surface of the base material. The erosion resistance was evaluated by causing Fe ₃ O ₄ particles to collide with this sample.

  A sample was prepared by performing thermal spraying using a resin having a ceramic (WC) content of 80% or 91%, and the erosion resistance was similarly evaluated.

  Further, thermal spraying was performed using a resin having a ceramic (CrC) content of 75%, 80% or 93%, and the erosion resistance was similarly evaluated. The results are as described in FIG.

  As a result of changing the WC and CrC contents and conducting tests under conditions stricter than the geothermal steam turbine operating conditions, WC has almost the same erosion resistance regardless of the contents, and CrC is contained in a large amount of 93%. Since the toughness was inferior in toughness, the erosion resistance was inferior to that of 80% CrC and 75% CrC, but it showed excellent corrosion resistance compared to the 12Cr steel substrate.

<Example 6> (Evaluation of peelability)
In order to confirm that the anti-corrosion and wear-resistant coating can be peeled and removed from the steam turbine nozzle that has been used for a long period of time, the coating site for the steam turbine nozzle is divided into four sections as shown in FIG. Polyester resin + WC
(2) Epoxy resin + WC
(3) WC alone (4) Thermal spraying with CrC alone and actual machine test for 2 years with actual geothermal steam turbine (steam temperature 270 ° C). However, it took a long time to remove the coating layer in combination with the blast treatment in the case of spraying WC and CrC independently.

<Example 7> (Evaluation of corrosion resistance)
As in Example 6, the corrosion resistance of the four types of coating layers formed on the steam turbine nozzle was evaluated. For the evaluation of corrosion resistance, corrosion products invaded through the pores of the coating layer, and the increase / decrease in weight due to corrosion was confirmed together with the interface peeling with the base material.

Regarding the interfacial peeling between the substrate and the coating layer, no interfacial peeling occurred in any of the coating layers.

Almost no increase or decrease in weight was observed in the corrosion test, and the weight due to adhesion of corrosion products slightly increased in the CrC sprayed material.
As a result, it was confirmed that the geothermal steam turbine nozzle formed with the coating layer can be easily removed from the nozzle plate by forming the resin coating layer, and also has corrosion resistance and erosion resistance. It was confirmed that

<Example 8> (Evaluation of solid particle erosion resistance (part 3))
A new test was conducted to confirm the wear resistance of the coatings tested under actual machine conditions. As shown in FIG. 6, the site for coating the geothermal steam turbine nozzle is divided into 6 sections, as shown in FIG. 6. Each section is divided into (1) polyester resin (2) epoxy resin (3) polyester resin + WC
(4) Epoxy resin + WC
(5) WC alone (6) Thermal spraying was carried out with CrC alone, and an actual machine test for 4992 hours was conducted with an actual machine geothermal steam turbine (steam temperature 270 ° C.).

Since the inflow of solid particles such as rocks into the geothermal steam was relatively small, there were no abnormalities such as coating thickness and damage to the coating. It was eroded by solid particle erosion.

  Although several embodiments of the present invention have been described, according to the geothermal steam turbine nozzle according to the embodiments of the present invention, the corrosion resistance is improved, and the amount of scale that adheres and accumulates and the peelability after adhesion is increased. Provided is a geothermal steam turbine that can be used for a long period of time, and a geothermal steam turbine that has a long life.

  According to the embodiment of the present invention, it is easy to remove the coating film deteriorated by the operation of the turbine, and when it is used again for the operation of the turbine, it has good scale adhesion prevention and scale removability. Further, a geothermal steam turbine nozzle having durability and the like and a manufacturing method thereof are provided.

DESCRIPTION OF SYMBOLS 1 Geothermal steam turbine 2 Steam inlet 3 Turbine stationary blade 30-36 Turbine nozzle 4 Turbine rotor blade 5 Turbine rotor shaft 6 Steam outlet 7 Turbine casing 8 Scale 9 Rotation direction of turbine rotor 10 Coating layer having gradient composition A A gradient composition Surface portion of coating layer B Deep layer portion of coating layer having gradient composition R Ceramic particles 12-16 Resin layer in which ceramic particles are dispersed 17 Base material of geothermal steam turbine nozzle

Claims (10)

A geothermal steam turbine nozzle in which a coating layer comprising a resin material in which ceramic particles are dispersed is formed in at least a part of a contact portion of the geothermal steam turbine nozzle with a geothermal fluid,
The geothermal steam turbine nozzle according to claim 1, wherein the coating layer has a gradient composition in which the content of the ceramic particles decreases from the surface portion toward the deep layer portion.   2. The geothermal steam turbine nozzle according to claim 1, wherein the coating layer has a gradient composition in which the content of the ceramic particles is varied in the thickness direction within a range of 0 to 80 wt%.   The geothermal steam turbine nozzle according to claim 1, wherein the resin material includes an epoxy resin or a polyester resin.   The geothermal steam turbine nozzle according to any one of claims 1 to 3, wherein the ceramic particles are selected from the group consisting of carbides and oxides of Cr, W, Ti, Nb, and Al.   The geothermal steam turbine nozzle of any one of Claims 1-4 whose ratio of the particle | grains to which a particle size exceeds 20 micrometers among the said ceramic particles is 10 weight% or less.   The coating layer according to any one of claims 1 to 5, wherein the coating layer has a resin layer having a thickness of 50 to 100 µm and a ceramic particle content of 40 to 80% by weight. The described geothermal steam turbine nozzle.   The geothermal steam turbine nozzle according to any one of claims 1 to 6, wherein the coating layer has a resin layer having a thickness of 20 to 40 µm and not containing the ceramic particles on the deep layer side. For the base material of the geothermal steam turbine nozzle,
It is made of a resin material in which ceramic particles are dispersed, and at least one coating layer having a gradient composition in which the content of the ceramic particles decreases from the surface portion toward the deep layer portion is formed. A method of manufacturing a steam turbine nozzle.   The method for manufacturing a geothermal steam turbine nozzle according to claim 8, wherein the coating layer is formed by a thermal spraying process.   The method for manufacturing a geothermal steam turbine nozzle according to claim 9, wherein the coating layer is formed by accumulating a plurality of sprayed layers each formed by a plurality of sprayed materials having different ceramic particle contents in the resin material.

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