JP2014155918A - Anticorrosion and antiwear coating method and power generation equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anticorrosion and antiwear coating method capable of curbing corrosion and wear of a steam turbine, a heat exchanger and piping which make up a power generation equipment and the power generation equipment.SOLUTION: A surface of power generation equipment subject to corrosion and wear due to steam is coated with an inorganic base layer coating 2 having a sacrificial anode function with respect to a material which makes up the surface. A resin coating having a self-repairing function with respect to heat conductivity, corrosion resistance and cracking is applied to the base layer coating 2 as an intermediary layer coating 3. An organic coating having anticorrosion and antiwear property is applied to the intermediary layer coating 3 as a top layer coating 4.

Description

The present invention relates to a corrosion-resistant / abrasion-resistant coating method and a power generator using the corrosion-resistant / abrasion-resistant coating method.

In the power generation equipment of power plants, especially steam turbines, heat exchangers, pipes, etc., when the steam temperature is 300 ° C or less room temperature or higher, the steam changes from dry steam to wet steam, and because of high-speed flow, Equipment is subject to corrosion and wear, increasing the likelihood of damage. The materials constituting the power generation equipment such as the steam turbine, heat exchanger, and piping are mainly composed of carbon steel, low alloy steel, and 9 to 17 wt% chromium (Cr) steel.

In order to improve the corrosion resistance and wear resistance of the power generation equipment, it is necessary to select a better material, that is, a so-called high-cost material that constitutes the target equipment.

Examples of the target device as described above include a heat exchanger for geothermal power generation. A heat exchanger is mainly composed of a tube, a tube tube plate, and a body and is generally manufactured using carbon steel or low alloy steel (containing 1-2 wt% chromium (Cr)). However, when used in a severe corrosive environment containing hydrogen sulfide (H ₂ S) or chlorine (Cl) such as geothermal heat, the materials constituting the tubes, tube tube plates, and body of the heat exchanger described above are Stainless steel, titanium (Ti), or a titanium alloy is often used.

However, while stainless steel, titanium (Ti) or titanium alloys have better corrosion resistance and wear resistance than carbon steel and low alloys, their thermal conductivity is lower than that of carbon steel and iron. Thermal efficiency is poor compared to exchangers. For example, in the case of SUS304 having a low thermal conductivity, the value is 0.16 w × 10 ⁻² / m ° C., and in the case of titanium, the value is 0.17 w × 10 ⁻² / m ° C., and carbon steel (0.58 w It can be seen whether it is much lower than × 10 ^-2 / m ° C or iron (0.58 w × 10 ^-2 / m ° C).

In addition, the coefficient of linear expansion is 17.3 × 10 ⁻⁶ in the case of SUS304, which is larger than 11 × 10 ^{−6 of} carbon steel, and easily expands and contracts due to repeated fluctuations in heat, resulting in internal stress of the device. Therefore, stress corrosion cracking due to stress concentration is likely to occur in a corrosive environment. In addition, the price of stainless steel and titanium materials is higher than that of carbon steel and low alloys.

Therefore, there is a need for a material that has a relatively good balance of thermal conductivity, linear expansion coefficient, and economy, and a method that suppresses corrosion and wear of the material for the heat exchanger of the power plant.

As a method for suppressing the corrosion and wear of the material, for example, at least one resin film layer is provided on the surface of the metal, and a metallic fin member is attached to the outer periphery of the resin film layer at a contact portion with the resin film layer. To do. A method is disclosed in which a metal pipe is provided with a corrosion-resistant plating layer and a resin coating layer, and the resin coating layer further contains particles or fibers having high corrosion resistance, wear resistance, and thermal conductivity (Patent Document 1). In addition, for gas use facilities, a method is also disclosed in which fluororesin is provided in multiple layers on a base and the content of inorganic filler is changed in each layer to improve corrosion resistance, heat resistance, etc. (Patent Document) 2).

Japanese Patent No. 4393854 JP 2004-283699 A

However, none of the above methods clarifies a countermeasure when a resin film layer deteriorates and a crack occurs or a method that does not cause a crack. When a crack occurs in the resin in a corrosive environment, even if there is a base anticorrosion plating layer provided on the surface of the target device, there is a possibility that it will disappear in a short period of time. For this reason, the local damage of the resin coating layer may greatly affect the service life of the target device.

The present invention has been made in view of such circumstances, and is a corrosion-resistant and wear-resistant coating capable of suppressing corrosion and wear of steam turbines, heat exchangers, piping, and the like that constitute power generation equipment of a power plant. It is an object to provide a method and power generation equipment.

In the corrosion-resistant and wear-resistant coating method according to the present invention, an inorganic base layer coating having a sacrificial anode function with respect to the material constituting the surface is formed on the surface of a power generation device where corrosion and wear due to steam occur. A resin-based coating with heat transfer, corrosion resistance and crack self-healing function is formed as an intermediate layer coating on the base layer coating, and an organic layer having corrosion resistance and abrasion resistance is formed on the intermediate layer coating. It is characterized in that the system coating is formed as a top layer coating.

In addition, the power generation device according to the present invention is characterized in that a corrosion / abrasion resistant coating using this corrosion / abrasion resistant coating method is formed on the surface of the device.

According to the present invention, a coating layer having high corrosion resistance and wear resistance and a long service life can be formed at a low cost with good workability. It is possible to improve the performance.

(A) to (d) is a cross-sectional view showing a production form of a corrosion-resistant and wear-resistant coating in each embodiment. Sectional drawing which expands and shows the base layer coating shown in FIG.1 (b). (A) is sectional drawing which expands and shows intermediate | middle layer coating containing the base layer coating shown in FIG.1 (c), (b) is a schematic diagram which expands and shows the A section of the intermediate | middle layer coating shown to (a). (A) to (c) is a schematic diagram showing a self-repair mechanism for a crack in each intermediate layer coating. (A) is a cross-sectional view showing an enlarged top layer coating including the base layer coating and intermediate layer coating shown in FIG. 1 (d), and (b) is an enlarged view of part B of the top layer coating shown in (a). FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows schematic structure of the steam turbine which is one Embodiment of the electric power generating apparatus which concerns on this invention, (a) is sectional drawing which shows the whole structure, (b) is a cross section which expands and shows the C section of (a). Figure. It is sectional drawing which shows schematic structure of the heat exchanger which is one Embodiment of the electric power generating apparatus which concerns on this invention, (a) is sectional drawing which shows a heat exchanger, (b) is the heat exchanger shown to (a). Sectional drawing which expands and shows D section, (c) is sectional drawing which shows the state which formed the corrosion-resistant coating layer in the tube sheet shown to (b).

FIG. 1 is a cross-sectional view showing a production form of a corrosion / abrasion resistant coating in the embodiment. FIG. 1A is a cross-sectional view of the target power generation device 1, and as shown in FIG. 1B, the surface of the target power generation device 1 is provided with a base layer coating 2 that is an inorganic coating having a sacrificial anode function. The

Thereafter, an intermediate layer coating 3 is further applied to the surface of the base layer coating 2 as shown in FIG.

Then, a top layer coating 4 is further applied to the surface of the intermediate layer coating 3 as shown in FIG.

As shown in FIG. 1, the anti-corrosion / abrasion-resistant coating in the embodiment is configured by sequentially laminating a base layer coating 2, an intermediate layer coating 3, and a top layer coating 4 on the surface of the power generation device 1.

Further, the operating environment of the power generation apparatus 1 shown in FIG. 1 is an environment having a constant flow rate, which is a steam or water environment containing 300 ° C. or less and 1 ° C. or more, steam or a corrosive component (for example, chlorine or hydrogen sulfide). Moreover, carbon steel, low alloy steel, and 9 to 17 wt% chromium (Cr) steel are generally used as the constituent material of the power generation device 1.

FIG. 2 is an enlarged cross-sectional view of the base layer coating 2 shown in FIG.

The base coating 2 is made of a metal made of zinc (Zn), magnesium (Mg), aluminum (Al) or zinc (Zn), magnesium on the surface of the target power generation device 1 by electrolytic plating, electroless plating or thermal spraying. It is formed by coating an alloy of (Mg) and aluminum (Al) and controlling the thickness to 1 μm to 1 mm.

Preferably, the composition of the base layer coating 2 is composed of an Al-based alloy of Mg: 1 to 5%, Zn: 3 to 15%, and Al: 80 to 96% by mass. This Al-based alloy is also composed of the Al-based alloy because the natural potential is lower than the carbon steel, low-alloy steel, and 9 to 17 wt% chromium (Cr) steel constituting the surface of the power generating device 1 described above. The base layer coating 2 can exhibit a sufficiently high sacrificial anodic action for the target power generation device 1 made of the above carbon steel, low alloy steel, and 9 to 17 wt% chromium (Cr) steel.

In the composition of the base layer coating 2, if the amount of Mg exceeds 5% and the amount of Zn exceeds 15%, an anticorrosive current more than necessary flows, so that the corrosion rate of the base layer coating 2 is increased and the lifetime is increased. Becomes shorter. On the other hand, when the addition amount of Mg is less than 1% and the addition amount of Zn is less than 3%, a sufficient anti-corrosion current does not flow, and the carbon steel, the low alloy steel, and the 9-17 wt% chromium (Cr) steel are used. A sufficient sacrificial anodic action cannot be exhibited for the target power generation device 1. For this reason, the addition amount of Mg is set to 1 to 5%, and the addition amount of Zn is set to 3 to 15%.

In addition, since it has been found from experimental data that the thickness of the base coating 2 with respect to the power generation equipment 1 due to the anticorrosion is 0.05 to 0.2 mm / year, the base coating 2 in the actual machine operating environment for 5 years. As a result, the maximum amount of thinning is 0.2 mm × 5 years = 1 mm. Therefore, if the base layer coating 2 having a thickness of 1 mm is applied to the power generation device 1, even if the intermediate layer coating 3 and the top layer coating 4 are peeled off and their functions are lost, the base layer coating 2 can be used for the power generation device 1 in a maximum of five years. An anticorrosive function can be exhibited on the surface of

3A is an enlarged cross-sectional view showing the intermediate layer coating 3 including the base layer coating 2 shown in FIG. 1C, and FIG. 3B is an enlarged view of part A of the intermediate layer coating shown in FIG. It is a schematic diagram shown.

As shown in FIG. 3, the intermediate layer coating 3 is composed of inorganic fibers 6 and superabsorbent resin particles 7 based on a fluororesin 5 as a basic composition.

Fluororesin 5 typically includes polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), perfluoroethylene-propene copolymer (FEP), polyvinylidene fluoride (PVDF) ), Ethylene-chlorotrifluoroethylene copolymer (ECTFE) or the like or a composite thereof.

In the construction of the intermediate layer coating 3, the surface of the object is generally degreased, surface-treated, painted, dried and fired in this order, and the thickness of the intermediate layer coating 3 is controlled to 50 μm to 2 mm. In such a case, the service life is shortened, and if it is too thick, the heat conductivity is deteriorated.

In the present invention, the intermediate layer coating 3 for keeping the heat conductivity to the maximum while considering the balance between the shape and content of the inorganic fibers 6 and the superabsorbent resin particles 7 and the fluororesin 5 as the base material. The thickness is desirably 1.5 mm.

The inorganic fiber 6 uses carbon fiber or glass fiber, and those having a diameter of 1 to 100 nm and a length of 1 nm to 2 mm, and an intermediate layer coating with a content of 1 to 5 wt% 3 is contained. In order to maximize the tensile strength of the intermediate layer coating 3, use carbon fiber or glass fiber having a diameter of 50 nm and a length of 1.5 mm, and a content of 3.5 wt%. Is desirable.

The superabsorbent resin particles 7 are hydrophilic cross-linked polymer resins obtained by cross-linking a water-soluble resin. As shown in FIG. 4B, when a crack occurs in the intermediate layer coating 3, The superabsorbent resin particles 7 exposed on the fracture surface come into contact with water in the environment and absorb to expand the volume of the resin particles 100 times or more as shown in FIG. Crush while filling the above-mentioned crack. Therefore, a self-repairing effect can be obtained for the crack.

The superabsorbent resin 7 is a synthetic polymer resin (for example, polyacrylate, polysulfonate, anhydride maleate, polyacrylamide, polyvinyl alcohol, polyethylene oxide), or a natural product-derived resin ( For example, polyaspartate type, polyglutamate type, polyalginate type, starch type, cellulose type) are used.

The particle size of the superabsorbent resin 7 contained in the intermediate layer coating 3 is 1 to 30 μm, and the content is 0.5 vol% to 3 vol%. Therefore, in order to maximize the self-repairing effect on the crack of the intermediate layer coating 3, it is desirable that the particle size is 10 μm and the content is 2.5 vol%.

5A is an enlarged cross-sectional view showing the top layer coating 4 including the base layer coating 2 and the intermediate layer coating 3 shown in FIG. 1D, and FIG. 5B is a cross-sectional view of the top layer coating 4 shown in FIG. It is a schematic diagram which expands and shows the B section.

Top layer coating 4 contains inorganic particles 8 having a hardness of 1000 Hv or more in order to improve the heat transfer and wear resistance of the coating, based on the same fluororesin 5 as in intermediate layer coating 3 as a basic composition. Let

The inorganic particles 8 are mainly TiN, TiC, TiCN, TiAlN, TiCrAlN, CrN, CrC, WC, WN, NiN, NiC, Co, Zr ₂ O ₃ , Y ₂ O ₃ , Al ₂ O ₃ , SiC, SiN, A powder such as SiO ₂ is used. The inorganic particles have a diameter of 0.1 to 30 μm and are contained in the top layer coating 4 at a content of 1 wt% to 30 wt%. Therefore, in order to maximize the wear resistance effect of the top layer coating 4, it is desirable that the particle size is 15 μm and the content is 20 wt% in the top layer coating 4.

Moreover, although the thickness of the top layer coating 4 is controlled to 50 μm to 2 mm, it is desirable to control the thickness of the top layer coating 4 to 1.5 mm in order to maximize heat transfer and wear resistance life.

The thicknesses of the anti-corrosion and anti-abrasion coating are controlled in the range of 101 μm to 5 mm by combining the thicknesses of the base layer coating 2, the intermediate layer coating 3 and the top layer coating 4 applied to the target power generation device 1. The appropriate thickness of the coating 2 is 1 mm, the appropriate thickness of the intermediate layer coating 3 is 1.5 mm, and the appropriate thickness of the top layer coating 4 is 1.5 mm. The thickness of the coating is desirably 4 mm.

FIG. 6 is a diagram illustrating a schematic configuration of a main part of a steam turbine that is an embodiment of the power generation device according to the present invention. FIG. 6A is a cross-sectional view showing the overall configuration.

As shown in FIG. 6 (a), the steam turbine 20 includes a high-pressure part 21, a medium-pressure part 22 and a low-pressure part 23 for a thermal power plant. On the other hand, although not shown, the steam turbine 20 has a high-pressure unit for a nuclear power plant. Part 21 and a low-pressure part 23, and a low-pressure part 23 for a geothermal power plant.

As shown in FIG. 6B, which is an enlarged view of a portion C in FIG. 6A, the low pressure portion 23 of the steam turbine 20 includes a moving blade 24, a stationary blade 25, a casing 26, a turbine rotor 27, and a seal portion 28. It is configured. In addition, as shown by the arrows in the figure, the steam flows from the left side to the right side in the figure.

On the inner surface side (the side exposed to the steam) of the rotor blade 24, the stationary blade 25, the casing 26 of the low-pressure part 23, the fuselage of the turbine rotor 27, especially in the region where the environmental temperature is 300 ° C or lower and 10 ° C or higher. Corrosion and wear resistant coatings related to the invention can be applied.

FIG. 7 is a diagram showing a schematic configuration of a main part of a heat exchanger for geothermal power generation according to another embodiment of the present invention.

Fig.7 (a) is sectional drawing which shows schematic structure of the heat exchanger 30 for geothermal power generation. Reference numerals 31 and 32 denote an inlet water chamber and an outlet water chamber of the refrigerant. As indicated by arrows in the figure, the refrigerant passes from the inlet water chamber 31 on the left side of the figure via the cooling pipe 33 to the right side in the figure. It flows in the direction of the water and exits from the outlet water chamber 32. The geothermal steam of 300 ° C. or less enters from the inlet pipe 34, and the cooled geothermal steam is condensed and drained, and is discharged from the outlet pipe 35.

FIG. 7B is an enlarged cross-sectional view showing a D portion of the heat exchanger 30. FIG. 7C is a diagram showing that the anti-corrosion / abrasion-resistant coating is applied to the cooling pipe 33 of the heat exchanger 30 in FIG. 7B.

As shown in FIG. 7 (c), the corrosion / abrasion resistant coating according to the present invention is applied to the surface (outer surface in the figure) exposed to the geothermal steam side of the cooling pipe 33 of the heat exchanger 30. Thus, corrosion and wear of the cooling pipe 33 are suppressed.

Therefore, since the anti-corrosion and wear-resistant coating is formed on the surface exposed to the geothermal steam side of the cooling pipe 33, high-carbon steel or low alloy steel having low cost and high thermal conductivity is used as the material of the cooling pipe 33. Can be selected.

As mentioned above, although several embodiment of this invention was described, these embodiment was posted 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. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Power generation equipment, 2 ... Base layer coating, 3 ... Intermediate layer coating, 4 ... Top layer coating, 5 ... Fluororesin, 6 ... Inorganic fiber, 7 ... Super absorbent resin particle, 8 ... Inorganic particle, 20 ... Steam Turbine, 21 ... high pressure part, 22 ... medium pressure part, 23 ... low pressure part, 24 ... moving blade, 25 ... stationary blade, 26 ... casing, 27 ... turbine rotor, 28 ... seal part, 30 ... heat exchanger, 31 ... Inlet water chamber, 32 ... outlet water chamber, 33 ... cooling pipe, 34 ... inlet pipe, 35 ... outlet pipe.

Claims (13)

An inorganic base coating having a sacrificial anode function is formed on the surface of the power generation equipment where corrosion and wear due to steam occur,
On this base layer coating, heat transfer, corrosion resistance, resin-based coating with self-healing function against cracks is formed as an intermediate layer coating,
Further, an organic coating having corrosion resistance and abrasion resistance is formed on the intermediate layer coating as a top layer coating.   2. The corrosion / abrasion resistant coating method according to claim 1, wherein the base layer coating is made of a metal made of Zn, Mg, Al or an alloy of the Zn, Mg, Al.   The material constituting the surface of the power generating device is carbon steel or low alloy steel, and the base layer coating is in mass%, Mg: 1 to 5%, Zn: 3 to 15%, Al: 80 to 96%. The corrosion-resistant and wear-resistant coating method according to claim 1, wherein the alloy is an Al-based alloy.   4. The corrosion / abrasion resistant coating method according to claim 1, wherein the intermediate layer coating contains an inorganic fiber and a superabsorbent resin based on a fluororesin as a composition. .   The said inorganic fiber uses a thing with a diameter of 1-100 nm and a length of 1 nm-2 mm, and makes it contain in the said intermediate | middle layer coating by 1-5 wt% as content. Corrosion and wear resistant coating method.   6. The superabsorbent resin is a resin of a hydrophilic cross-linked polymer obtained by cross-linking a water-soluble resin, and particles of the superabsorbent resin are contained in an intermediate layer coating. Corrosion and wear resistant coating method.   7. The corrosion / abrasion resistant coating method according to claim 6, wherein the superabsorbent resin has a particle size of 1 to 30 [mu] m and a content of 0.5 vol% to 3 vol%.   8. The corrosion / abrasion resistant coating method according to claim 1, wherein the top layer coating contains inorganic particles having a hardness of 1000 Hv or more based on a fluororesin composition. . The inorganic particles are TiN, TiC, TiCN, TiAlN, TiCrAlN, CrN, CrC, WC, WN, NiN, NiC, Co, Zr 2 O 3, Y 2 O 3, Al 2 O 3, SiC, SiN, SiO 2 9. The corrosion / abrasion resistant coating method according to claim 8, wherein the powder comprises at least one member.   10. The corrosion / abrasion resistant coating according to claim 8 or 9, wherein the inorganic particles have a diameter of 0.1 to 30 [mu] m and are contained in the top layer coating at a content of 1 wt% to 30 wt%. Method.   11. The thickness of the anti-corrosion / anti-abrasion coating obtained by combining the thicknesses of the base layer coating, the intermediate layer coating, and the top layer coating is set to 101 μm to 5 mm. 11. Corrosion-resistant and wear-resistant coating method as described in the section.   12. A power generation device, wherein a corrosion-resistant and wear-resistant coating using the corrosion-resistant and wear-resistant coating method according to any one of claims 1 to 11 is formed on a surface of the device.   The said apparatus is a steam turbine, a heat exchanger, and piping, The said corrosion-resistant and abrasion-resistant coating was formed in the part which contact | connects the fluid, The electric power generating apparatus of Claim 12 characterized by the above-mentioned.

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