CN110062815B

CN110062815B - Boiler water pipe of waste incinerator and manufacturing method thereof

Info

Publication number: CN110062815B
Application number: CN201780069554.9A
Authority: CN
Inventors: 北井豪太; 野口学; 冈部由知; 永田秀树; 石井章文; 上野有史
Original assignee: Tocalo Co Ltd; Ebara Environmental Plant Co Ltd
Current assignee: Tocalo Co Ltd; Ebara Environmental Plant Co Ltd
Priority date: 2016-11-10
Filing date: 2017-10-27
Publication date: 2022-06-28
Anticipated expiration: 2037-10-27
Also published as: WO2018088251A1; JP6802042B2; CN110062815A; TW201829807A; TWI749097B; JP2018076564A

Abstract

The present invention relates to a long life of boiler water tubes (heat transfer tubes) of general waste incinerator boilers and the like. The surface of a base material of a boiler water pipe of a waste incinerator is coated with a spray coating film. The sprayed coating is formed by stacking flat metal particles and has a structure in which Ni (nickel) is concentrated so as to fill the gaps between the metal particles.

Description

Boiler water pipe of waste incinerator and manufacturing method thereof

Technical Field

The present invention relates to a long life of boiler water tubes (heat transfer tubes) of general waste incinerator boilers and the like. The improved powder for thermal spraying is used to coat the surface of a base material with a thermal spray coating having high-temperature corrosion resistance, and particularly to form a thermal spray coating having excellent corrosion resistance on the surfaces of a heat transfer tube and a water wall tube of a waste incinerator boiler by high-velocity flame spraying (HVOF spraying).

Background

In order to reduce the amount of corrosion reduction and to extend the life of boiler water tubes (heat transfer tubes), corrosion-resistant materials have been applied to water tube base materials, surface modification (formation of corrosion-resistant thermal spray coatings) of water tube base materials, sealing treatments, and build-up welding. Although any of these measures has its merits and shortcomings, it is effective to provide a spray coating of a corrosion-resistant material to a water tube base material as a measure for boiler operation because it is a method that can be carried out on site. However, since pores are present and continuous in the formed sprayed coating, corrosive substances may enter the interface of the base material to corrode the base material, and the coating may be peeled off, thereby exposing the base material to corrosive exhaust gas.

Parent material of water pipe

Conventionally, in a water pipe base material used in a flow path through which combustion gas from a furnace flows in a furnace of a waste incinerator boiler, an austenite material excellent in corrosion resistance and wear resistance has been used because of wear and thickening due to high-temperature corrosion and combustion ash (fly ash) contained in the combustion gas. However, CaSO as an adhering ash due to exposure in high-temperature reducing flames resulting from low air ratio operation₄Metal chlorides and sulfate compounds of Na, K, Pb, etc. in NaCl, KCl, scale (scale), and thus molten salt corrosion, etc. are involved. Therefore, the following countermeasures are implemented: a water pipe (evaporation pipe) base material is made of a material with high corrosion resistance and high abrasion resistance; or the position of the evaporation pipe (water pipe) after replacement is constructed by refractory materials; or spraying on the surface of the evaporation tube (water pipe); and so on. For the superheater tubes, the following countermeasures were taken: mounting a protector for protecting a portion belonging to wear reduction on a watchKneading; or a thick-walled tube or a material having high corrosion resistance is used; and so on. However, the initial cost tends to increase when a base material such as a water pipe material is selected, and the initial cost may increase when a refractory is coated, or when a heat transfer area is secured, the capacity of the entire boiler may increase, and it is desirable to select and design the base material as easily as possible.

Spray coating material

Conventionally, as a powder for thermal spraying onto the surface of an evaporation tube (water tube), a granulated sintered powder of a cermet system such as a Ni-based self-fluxing alloy, a Fe-based ferrosilicon alloy system material, and chromium carbide or tungsten carbide, which is excellent in corrosion resistance and wear resistance, has been used.

In the formation of a thermal spray coating, the present applicant has been searching for a method of suppressing porosity and achieving densification. In order to achieve densification of a sprayed coating, there are no other methods such as a spraying method and a sealing treatment, and a spraying material having superiority and specificity in a boiler water pipe in a severe case such as corrosive exhaust gas of a waste treatment facility in, for example, a boiler is actually under development and research.

Spraying method

There are various methods of thermal spraying, and thermal spraying is classified according to the material used, the type of heat source, and the like. Examples of thermal spraying using a combustion gas as a heat source include gas wire spraying (gas wire spraying), high-speed flame spraying, and explosive spraying. Examples of the thermal spraying using electricity as a heat source include arc spraying, plasma spraying, RF plasma spraying, electromagnetic acceleration plasma spraying, wire explosion spraying, and electrothermal explosion powder spraying. In addition, there are laser spraying and the like using laser as a heat source. Among these thermal spraying methods, the optimal thermal spraying method is selected based on the thermal spraying material, the working conditions, and the like.

In a waste incinerator boiler, gas wire spraying, high-speed flame spraying, or arc spraying is generally selected, but in the construction practice using conventional spraying materials, the life of a sprayed film by gas wire spraying or arc spraying is about 2 to 3 years, depending on the environment of use. Further, in the conventional high-speed flame spraying, the particle velocity is increased to achieve densification of the coating, but the service life of the sprayed coating in practical use is about 3 to 5 years, and the corrosion resistance of the coating is insufficient in consideration of the service life of facilities.

Melting treatment (melting treatment)

As a sealing treatment by a self-fluxing alloy, there is a method of improving the corrosion resistance of a coating by temporarily melting the coating after the application of a thermal spray coating and eliminating pores. However, since an electric furnace (see patent document 1), a high-frequency induction heating (see patent document 2), or the like is used for performing the melting process, it is necessary to perform the melting process in a factory, and the repair work cannot be performed on site, and therefore, the melting process cannot be selected for the long life of the facility during operation.

As a sealing treatment by Al thermal spraying, there is a method of blocking pores by thermal spraying molten Al on a coating film formed by ordinary flame spraying or the like. However, it was confirmed that the Al layer having poor corrosion resistance disappeared over about 2 years, and the pore-sealing function was lost. In addition, it is necessary to spray the Ni-based alloy of the base and the plugging material 2 times, which is labor-consuming. In the countermeasure for prolonging the service life of a facility during operation, it is difficult to avoid high cost because it takes a long time of work due to labor and the number of man-hours is increased compared to material cost and the like, and it is difficult to select such spray plating for repair work during a limited period of facility stop (see non-patent document 1).

As another sealing and spraying technique, a technique of compounding a sealing agent with a vitreous material for sealing pores is known. However, in the actual boiler, in addition to the start and stop, thermal stress is generated in the sprayed film due to various factors such as the influence of soot blowing for removing the deposited ash, and the temperature fluctuation of the operation. Therefore, when materials having different thermal expansion coefficients are combined, there is a high possibility that cracking or peeling occurs during operation, and sufficient durability cannot be expected, and it is difficult to select such thermal spraying (see patent document 3).

Build-up welding

Since the build-up welding has no through-hole, it is excellent in corrosion resistance and can be made thick, and therefore, a method for increasing the life of the weld is expected. However, since excessive heat input is required during the welding operation, the base material may be thermally affected, or the base material may be deformed. Further, although field repair is possible, it is limited to local repair, and extensive construction takes a long time, so that the number of workers increases, and it is inevitable to increase the cost, and it is difficult to select such welding for repair construction during a limited facility stop period, and the like.

Documents of the prior art

Patent literature

Patent document 1: japanese patent laid-open publication No. 8-13119

Patent document 2: japanese laid-open patent publication No. 10-46315

Patent document 3: japanese patent laid-open publication No. 2001-192802

Non-patent document

Non-patent document 1: "the current situation of application of high-temperature corrosion coating and durability evaluation of the boiler for generating waste power" (the " product ボイラにおける high-temperature corrosion food コ - テイング coating and the like" on the durability value of と), thermal spraying, No. 2, No. 38, page 73 (2001), etc.)

Disclosure of Invention

Problems to be solved by the invention

When a corrosion-resistant material is used for the water pipe base material, a significant cost increase is caused, and this countermeasure is difficult to deal with in facilities after operation (it is not practical to perform the pipe drawing repair on the whole portion). On the other hand, it is difficult to increase the life of the evaporator at a low cost even if measures such as pouring materials are applied to the portion of the evaporator (water pipe) after replacement and conventionally used thermal spraying is applied to the surface of the evaporator (water pipe).

In a general thermal spraying process, it is difficult to completely remove pores only by increasing the particle velocity. In addition, when the Ni — Cr-based powder material is used, the grain boundary of the film structure after film formation is corroded by the grain boundary due to an increase in the composition ratio of Cr caused by the thermal influence at the time of thermal spraying and low corrosion resistance of the film in the boiler environment in the waste incinerator, which adversely affects the life of the film.

Self-fluxing alloying is a promising method for eliminating pores, but cannot be used for repair or the like because it cannot be applied on site.

In the case of composite thermal spraying such as Al sealing treatment, the process becomes complicated, which leads to an increase in cost. The composite coating with glass or the like is not suitable for use in a portion having high thermal stress because of poor reliability of the coating itself. Overlay welding has many advantages over spray welding, but has problems in workability and high repair costs.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a spray coating which can achieve a long service life of a boiler water pipe by minimizing cost increase and process complication, and which can achieve field construction and field repair, thereby achieving excellent LCC (life cycle cost) and field repair.

That is, an object of the present invention is to provide a boiler water pipe of a waste incinerator coated with a sprayed film, which can reduce the amount of corrosion and decrease the thickness thereof, and can achieve a longer service life, and a method for manufacturing the same.

Means for solving the problems

In order to achieve the above object, one aspect of the present invention is a boiler water pipe for a waste incinerator, in which the surface of a base material is coated with a thermal spray coating, wherein the thermal spray coating is formed by stacking flat metal particles and has a structure in which Ni (nickel) is concentrated so as to fill the gaps between the metal particles.

In a preferred embodiment of the present invention, the metal particles are a Ni (nickel) -based alloy containing Ni (nickel) as a main component and Cr (chromium), B (boron), Si (silicon), Mo (molybdenum), and Cu (copper). In a preferred aspect of the present invention, the sprayed coating has a porosity of less than 1%.

In a preferred embodiment of the present invention, the thickness of the sprayed coating is 100 μm or more and 1000 μm or less.

Another aspect of the present invention is a method for producing a boiler water tube for a waste incinerator, wherein a coating step by thermal spraying is performed on a surface of a base material, wherein the thermal spraying is performed using a thermal spraying powder obtained by subjecting surfaces of metal particles to an Ni (nickel) coating treatment, and a melting point of the metal particles subjected to the Ni (nickel) coating treatment is higher than a melting point of an Ni (nickel) coating film covering the metal particles.

In a preferred embodiment of the present invention, the Ni (nickel) coating process is an electroless Ni (nickel) -P (phosphorus) plating process.

In a preferred embodiment of the present invention, the Ni (nickel) coating film formed by the Ni (nickel) coating treatment contains 5 to 10 mass% of P (phosphorus).

In a preferred embodiment of the present invention, the metal particles are a Ni (nickel) -based alloy containing Ni (nickel) as a main component and Cr (chromium), B (boron), Si (silicon), Mo (molybdenum), and Cu (copper).

In a preferred aspect of the present invention, the thermal spraying is a high-speed flame spraying method.

In a preferred aspect of the present invention, the thermal spraying is not followed by a melting process.

The boiler water pipe for a waste incinerator, which is formed by coating the surface with a spray coating film having a high corrosion resistance material concentrated between particles and improved compactness, is produced from a spray coating powder material which is coated with a metal having high corrosion resistance and a lower melting point than the base spray coating powder material. In the case of a general thermal spray coating, corrosive substances penetrate into the coating from the outside through grain boundaries between particles having many pores, and the corrosion of the coating progresses. In the present invention, since the highly corrosion-resistant material is concentrated between the particles, progress of corrosion is inhibited, and corrosion resistance is improved. When a sprayed coating is formed by high-speed flame spraying using a normal powder material, the porosity of the sprayed coating is about 6%. In the present invention, the porosity between particles is reduced by melting of the surface Ni coating layer having a low melting point. The porosity was measured to be less than 1%. By virtue of the above effects, the corrosion resistance of the entire sprayed coating is improved, and the sprayed coating is excellent in preventing erosion along grain boundaries between particles in particular, and a long life of about 2 times or more of a conventional sprayed coating and a boiler water pipe can be achieved.

In order to realize field construction and repair, a thermal spraying method which has been practiced in field construction has been conventionally adopted, and the corrosion resistance of a thermal sprayed film has been improved by improving the thermal spraying material to increase the porosity. According to the present invention, in order to prevent erosion of the inside of the coating along the grain boundaries of Ni — Cr-based powder particles which is a conventional thermal spray material, densification of the thermal spray coating is achieved by applying a metal plating treatment having high corrosion resistance to the thermal spray material powder, and in particular, the corrosion resistance of the grain boundaries is improved, thereby enabling a conventional long life of 2 times or more.

Effects of the invention

According to the present invention, the thermal spray coating is formed on the water tube of the boiler, so that the corrosion resistance of the water tube base material of the boiler can be improved, and economic effects such as repair and renewal due to the increase in the life span can be achieved. Further, by applying the Ni coating treatment to the thermal spray powder material, the coating performance of the grain boundary portion between the particles is higher than that of the coating process performed after the thermal spray coating operation, and the erosion resistance of the grain boundary portion is remarkably improved up to the inside of the thermal spray coating.

Further, by applying a metal plating treatment having a melting point lower than that of the conventional thermal spraying powder material, the powder surface is easily melted. By blowing and spraying the molten particles at a high speed onto the surface of the water pipe to laminate them, the structure is further densified as compared with the conventional film structure, and the porosity is reduced. Further, the grain boundary of the film structure after film formation is improved in the composition ratio of Ni excellent in corrosion resistance in the boiler environment in the waste incinerator by plating treatment, and therefore, the film structure has an effect of preventing erosion of the inside of the film along the grain boundary as compared with the conventional film structure. By the above improvement, a highly dense thermal spray coating having a reduced porosity (which is an important problem as a thermal spray powder material for enhancing the grain boundary erosion suppression effect) can be formed.

By combining the thermal spraying powder material with the high-speed flame spraying method, a thermal spraying coating film further densified by the thermal spraying powder material can be formed. The porosity of the conventional sprayed coating was about 6%, and the porosity of the sprayed coating according to the present invention was successfully improved to less than 1%. The decrease in porosity indicates that the spray coating film having improved compactness is realized. Further, the high-speed flame sprayed coating is excellent in the fusion property with the water pipe base material, and becomes a sprayed coating in which grain boundaries and grain boundary surfaces are infinitely reduced, and as a sprayed coating excellent in corrosion resistance by increasing the density, it is a sprayed coating having an advantage of increasing the life of the sprayed coating by 2 times or more compared with a conventional sprayed coating.

A specific thermal spraying powder material is combined with high-speed flame spraying, and a thermal spraying coating with corrosion resistance and improved compactness can be formed while simplifying the construction process as much as possible without depending on the conventional melting treatment method. It is needless to say that the present process can be used for factory construction, and can be actually used in facilities in operation regardless of the conventional construction period and cost.

Drawings

FIG. 1 is a schematic view showing a thermal spraying apparatus for performing high-speed flame spraying.

FIG. 2A is a graph showing the results of measuring the porosity of a conventional material and a novel material.

Fig. 2B is a schematic view of fig. 2A.

FIG. 3 is a view showing a spray water pipe panel (panel) constructed in an actual gas exposure test.

FIG. 4 is a graph showing the results of measurement of a sprayed coating in an actual gas exposure test.

FIG. 5 is a view showing a test apparatus for carrying out a high-temperature corrosion test.

FIG. 6 is a graph showing the results of the thickness reduction of the sprayed coating in the high-temperature corrosion test.

FIG. 7A is a view showing the results of cross-sectional observation of a high-temperature corrosion test of a test piece A.

Fig. 7B is a schematic view of fig. 7A.

FIG. 8A is a view showing the results of cross-sectional observation of a high-temperature corrosion test on a test piece B.

Fig. 8B is a schematic view of fig. 8A.

FIG. 9A is a view showing the results of cross-sectional observation of a high-temperature corrosion test of a test piece C.

Fig. 9B is a schematic view of fig. 9A.

FIG. 10A is a graph showing the results of measuring the Ni concentration of a conventional material.

Fig. 10B is an enlarged schematic view of a main portion of fig. 10A.

FIG. 11A is a graph showing the results of measuring the Ni concentration of the novel material.

Fig. 11B is an enlarged schematic view of a main portion of fig. 11A.

FIG. 12A is a graph showing the results of EPMA analysis of a conventional material.

FIG. 12B is a schematic view showing an image (K, Na, Pb, Cl) of the other components in FIG. 12A.

FIG. 13A is a view showing the results of EPMA analysis of the novel material.

FIG. 13B is a schematic view showing an image (K, Na, Pb, Cl) of the other components in FIG. 13A.

Detailed Description

As the best mode for carrying out the present invention, it is preferable to apply a plating treatment to a conventional thermal spraying powder material by electroless Ni-P plating, and it is further preferable to form a uniform coating of 200 μm or more by applying thermal spraying with a high-speed flame.

The invention according to the present embodiment is a boiler water pipe for a waste incinerator in which the surface of a base material (base material) is coated with a spray coating. The sprayed coating is formed by stacking flat metal particles and has a structure in which Ni (nickel) is concentrated so as to fill the gaps between the metal particles. The structure in which Ni is concentrated means a structure in which Ni is higher in concentration than the metal particles constituting the periphery of the sprayed coating, and preferably a structure in which Ni is higher in concentration by 10 mass% or more than the metal particles. Further, a structure containing 80 mass% or more of Ni is preferable.

The invention according to the present embodiment is a method for manufacturing a boiler water pipe of a waste incinerator, in which a coating process by thermal spraying is performed on the surface of a base material (substrate). In thermal spraying, a thermal spraying powder obtained by applying Ni coating treatment to the surface of each of the metal particles is used as a material. The melting point of the metal particles subjected to the Ni (nickel) coating treatment is higher than the melting point of the Ni (nickel) coating film covering the metal particles.

According to the present embodiment, the thermal spray coating is formed on the water tube of the boiler, so that the corrosion resistance of the base material of the water tube of the boiler can be improved, and economic effects such as repair and renewal due to a longer service life can be achieved. Further, by applying an Ni coating treatment (more specifically, an electroless Ni — P plating treatment) to the thermal spray powder material, the coating performance of the grain boundary portions between the particles is high and the erosion resistance of the grain boundary portions is remarkably improved up to the inside of the thermal spray coating, as compared with the coating treatment after the thermal spray coating construction.

The Ni coating film formed by the Ni coating treatment contains 5 to 10 mass% of P (phosphorus), and the melting point of the metal particles subjected to the Ni coating treatment is higher than the melting point of the Ni coating film covering the metal particles. For example, the metal particles are Ni-based alloys containing Ni (nickel) as a main component and Cr (chromium), and more preferably Ni-based alloys further containing B (boron), Si (silicon), Mo (molybdenum), and Cu (copper). Preferably, the Ni-based alloy contains 5 mass% to 15 mass% of Cr and 30 mass% to 75 mass% of Ni.

By applying a plating treatment to a conventional thermal spraying powder material with a metal having a lower melting point than the material, the powder surface is easily melted. By blowing the molten particles at a high speed onto the surface of the water pipe to laminate them, the film is further densified and the porosity is reduced as compared with the conventional film structure. Further, the grain boundary of the film structure after film formation is improved in the composition ratio of Ni excellent in corrosion resistance in the boiler environment in the waste incinerator by plating treatment, and therefore, the film structure has an effect of preventing erosion of the inside of the film along the grain boundary as compared with the conventional film structure. By the above improvement, a highly dense thermal spray coating having a reduced porosity (which is an important problem as a thermal spray powder material for enhancing the grain boundary erosion suppression effect) can be formed.

In order to form a sprayed coating by blowing a sprayed powder material at a high speed onto the surface of the base material, in the present embodiment, a sprayed coating formed of a sprayed powder material subjected to Ni coating treatment is formed by high-speed flame (HVOF) spraying. The upper limit is 1000 μm, because the longer the sprayed coating is, the longer the life of the coating itself is for the corrosion to decrease in thickness, but the upper limit increases the risk of cracking if it is too thick. On the other hand, if it is too thin, the environmental barrier function is lowered, and the lifetime against corrosion thickening becomes short, so it is preferably 100 μm or more, more preferably 200 μm or more and 1000 μm or less. The high velocity flame spraying is the following method: a thermal spraying method in which a high-speed flame comparable to an explosion flame is generated by increasing the pressure in a combustion chamber in a thermal spraying apparatus, a powder material is supplied to the center of the combustion flame jet and brought into a molten or semi-molten state, and the powder material is continuously sprayed at a high speed.

FIG. 1 is a schematic view showing a thermal spraying apparatus for carrying out high-speed flame spraying. As shown in fig. 1, fuel (e.g., kerosene) and oxygen are supplied to a combustion chamber 10 in a main body 15 of the thermal spraying apparatus through a fuel inlet 11 and an oxygen inlet 12, respectively. The mixture of fuel and oxygen is ignited by the ignition plug 13, and the resulting combustion gas becomes a high-speed gas inside the body 15. The powder material subjected to the Ni coating treatment is supplied from the material inlet 14 into the main body 15, and is heated and accelerated. In this way, the powder material which becomes the high-speed flight particles is blown to the surface of the base material, and the sprayed coating is formed on the base material. The cooling water is injected from the cooling water injection port 16 and discharged from the cooling water discharge port 17, and thus the inside of the main body 15 is cooled.

In the present embodiment, after thermal spraying, melting treatment is not performed. Therefore, it is not necessary to use an electric furnace or high-frequency induction heating, and repair work can be easily performed on site.

By combining the thermal spray powder material according to the present embodiment with the high-speed flame thermal spray method, a thermal spray coating that is more dense can be formed from the thermal spray powder material. Fig. 2 shows the results of measuring the porosity of the existing material and the new material. Fig. 2A is a graph showing the results of measuring the porosity of the conventional material and the novel material, and fig. 2B is a schematic diagram of fig. 2A. The black dots shown in the upper diagram of fig. 2B indicate pores formed in the sprayed coating. The porosity of the conventional sprayed coating was about 6%, and the porosity of the sprayed coating according to the present embodiment was successfully improved to less than 1%. The porosity can be calculated by binarizing an image observed with an optical microscope and measuring the area of the black region in proportion to the entire area. The decrease in porosity indicates that the spray coating film having improved denseness was realized. The high-speed flame sprayed coating is also excellent in fusibility to the water pipe base metal and is a sprayed coating in which grain boundaries and grain boundary surfaces are infinitely reduced, and as a sprayed coating excellent in corrosion resistance by increasing the density, a sprayed coating having an advantage of increasing the lifetime by 2 times or more as compared with a conventional sprayed coating.

According to the present embodiment, a specific thermal spray powder material is combined with high-speed flame thermal spraying, and a thermal spray coating having corrosion resistance and improved denseness can be formed while simplifying the working process as much as possible without depending on the conventional melting method. It is needless to say that the present process can be applied to factory construction, and can be actually used in facilities during operation regardless of the conventional construction period and cost.

EXAMPLE 1 in-situ Exposure test

FIG. 3 is a view showing a sprayed water pipe panel constructed in an actual gas exposure test. Fig. 4 is a graph showing the measurement results of the sprayed coating in the actual gas exposure test. A thermal spray coating made of a conventional material as a comparative example was formed at the positions shown in fig. 3 (1) and (2), and a thermal spray coating made of a novel material according to the present embodiment was formed at the positions shown in fig. 3 (3) and (4). As a conventional material, Ni-based alloy (Ni-15Cr-4B-4Si-3Mo-3Cu) powder was used. As a novel material, a powder obtained by electroless Ni-P plating of a Ni-based alloy (Ni-15Cr-4B-4Si-3Mo-3Cu) was used. As the thermal spraying method, a high-speed flame spraying method is used.

The sprayed water tube panel shown in fig. 3 was installed in a water tube in an actual boiler furnace, and an actual gas exposure test based on the sprayed coatings of (1) to (4) was performed for 5 years. As shown in fig. 4, based on the results of the sprayed coating measurement in the actual gas exposure test, it was confirmed that the sprayed coating of the novel material secured a residual coating 2 times or more as high as that of the conventional material, and was excellent in corrosion resistance and durability.

That is, the thickness of the thermal spray coating of the novel material at the start of the test was about 400 μm, and the thickness of the thermal spray coating of the novel material at the time point 5 years after the start of the test was about 310 to 340 μm. In contrast, the thickness of the sprayed coating of the conventional material at the start of the test was about 420 μm, and the thickness of the sprayed coating of the conventional material at the time point 5 years after the start of the test was about 150 μm. As can be seen from fig. 4, the thermal spray coating of the novel material has excellent corrosion resistance and durability as compared with the thermal spray coating of the conventional material.

EXAMPLE 2 high-temperature Corrosion test

The high-temperature corrosion test was carried out in a tube furnace in accordance with the salt immersion and salt burial high-temperature corrosion test method for metal materials in JIS standard "JISZ 2293". Table 1 shows the test conditions of the high-temperature corrosion test.

[ Table 1]

Based on the high-temperature corrosion test conditions shown in table 1, a test was performed by a high-temperature corrosion test method using a test apparatus shown in fig. 5. Details of the test apparatus of fig. 5 are described later. A test specimen was prepared by spraying a conventional material and a novel material onto a test specimen (20 mm. times.20 mm. times.10 mm (thickness)) of S25C (carbon steel) as a base material. As a comparative object, the same test was performed on the base material of S25C. The test temperatures were 300 deg.C, 345 deg.C, and 400 deg.C, respectively. At the above test temperatures, high-temperature corrosion tests were carried out for 300 hours. The test ash was prepared by using synthetic ash, melting the synthetic ash at a high temperature, pulverizing the resultant, and mixing the resultant powders. The melting point of the ash is around 350 ℃.

Fig. 5 is a diagram showing a test apparatus for performing a high-temperature corrosion test. As shown in fig. 5, a ceramic boat 2 is disposed in an electric furnace 1, and a crucible 3 is disposed above the ceramic boat 2. The crucible 3 is filled with molten salt 4, and the test piece 5 is buried in the molten salt 4. The atmosphere flows in the direction of the arrow in fig. 5. In fig. 5, symbol T denotes a thermocouple for measuring the temperature of the atmosphere in the furnace, and the temperature in the electric furnace 1 is measured by this thermocouple T. Symbol T_TPShowing a thermocouple for measuring the temperature of the test piece, and the temperature of the test piece 5 is measured by the thermocouple T_TPAnd (4) measuring. An electric furnace control thermocouple TC is provided in the central portion of the electric furnace 1. The temperature of the electric furnace 1 is controlled so that the temperature difference of the electric furnace 1 is within ± 3 ℃ within 100mm from the center of the electric furnace 1. The crucible 3 in which the test piece 5 was buried was disposed within a range of 100mm from the center of the electric furnace 1.

The test results of the high temperature corrosion test are shown in table 2. As shown in Table 2, no significant change was observed in any of the materials at 300 ℃ and 345 ℃. Under 400 c, a significant difference was observed in visual confirmation, with the least corrosion of the new material. Therefore, it was confirmed that the corrosion resistance of the novel material is much higher than that of the conventional material.

[ Table 2]

As shown in table 2, the test piece a was significantly corroded, and the base material was exposed by the corrosion. Likewise, test piece C also corroded significantly. On the other hand, the test piece B was slightly corroded, and only the outermost surface layer of the sprayed coating corroded.

FIG. 6 is a graph showing the results of the thickness reduction of the sprayed coating in the high-temperature corrosion test. Fig. 7A and 8A are views showing the results of cross-sectional observation of the high-temperature corrosion test of each of test pieces a and B. Fig. 7B is a schematic view of fig. 7A, and fig. 8B is a schematic view of fig. 8A. As shown in fig. 7 (fig. 7A and 7B) and fig. 8 (fig. 8A and 8B), it is understood that in the test piece a (conventional material) under the condition that the water pipe surface temperature is 400 ℃, the corrosion reaching the base material is remarkable, and the test piece B (novel material) is only the corrosion of the outermost surface layer of the sprayed coating. Fig. 9A is a view showing a cross-sectional observation result of a high-temperature corrosion test of the test piece C, and fig. 9B is a schematic view of fig. 9A. As shown in fig. 9 (fig. 9A and 9B), it is understood that corrosion of the test piece C (base material) is remarkable under the condition that the water pipe surface temperature is 400 ℃.

Table 3 shows the melting points of the thermal spraying powder materials. As shown in table 3, the concentration of P (phosphorus) in the sprayed powder material obtained by subjecting the conventional material to electroless Ni — P plating treatment is preferably 5 to 10%, and more preferably 8%. The melting point of the conventional material not subjected to electroless Ni-P plating treatment was 980 ℃ or higher, the melting point of the thermal spray powder material at a P concentration of 8% was 890 ℃, the melting point of the thermal spray powder material at a P concentration of 10% was 850 ℃, and the melting point of the thermal spray powder material at a P concentration of 5% was 950 ℃. If the concentration of P (phosphorus) is too low, the melting point increases, and therefore the surface of the sprayed powder material becomes less likely to melt, which adversely affects the densification of the coating film. On the other hand, if the concentration of P (phosphorus) is too high, the melting point decreases, so that the surface of the thermal spraying powder material is excessively melted to cause a sputtering phenomenon (sputtering phenomenon), and defects are likely to be generated in the coating film. Here, the splash phenomenon is a phenomenon in which an excessively molten thermal spray powder material is deposited on the inner wall of the thermal spray device (see fig. 1), and the deposit falls off from the nozzle and is mixed into the coating film.

[ Table 3]

Fig. 10 shows the Ni concentration measurement result of the conventional material, and fig. 11 shows the Ni concentration measurement result of the novel material. Fig. 10A is a graph showing the measurement result of the Ni concentration of the conventional material, and fig. 10B is an enlarged schematic view of a main portion of fig. 10A. Fig. 11A is a graph showing the result of measuring the Ni concentration of the novel material, and fig. 11B is an enlarged schematic view of a main portion of fig. 11A. In fig. 10B and 11B, the metal particles (thermal spray particles) are shown as white areas plotted by a curve, and grain boundaries exist between the metal particles (thermal spray particles). According to fig. 10A, the Ni concentrations in the grains and in the grain boundaries are both about 60 mass%. As shown in fig. 10B, Ni (nickel) is not concentrated in the grain boundaries, and the structure of Ni in the grain boundaries is not formed so as to fill the voids of the metal particles. On the other hand, as is clear from fig. 11 (fig. 11A and 11B), in the novel material, the Ni concentration in the grains is about 60 mass%, the Ni concentration in the grain boundaries is 80 mass% or more, and the structure in which Ni (nickel) is concentrated is formed so as to fill the voids of the flat metal particles. The structure in which Ni is concentrated means a structure in which Ni is higher in concentration than the metal particles constituting the periphery of the thermal spray coating, and preferably a structure in which Ni is higher in concentration by 10 mass% or more than the metal particles. Further, it is also found that a structure containing 80 mass% or more of Ni is preferable. Thus, according to the novel material, a dense film having a structure in which Ni is concentrated along grain boundaries between particles constituting the film can be obtained.

Fig. 12 and 13 are graphs showing EPMA analysis results of the film structure after the high-temperature corrosion test at a measurement temperature of 400 ℃. More specifically, fig. 12A is a graph showing the results of EPMA analysis of a conventional material, and fig. 12B is a schematic diagram showing images (K, Na, Pb, Cl) of other components in fig. 12A. Fig. 13A is a graph showing the EPMA analysis result of the novel material, and fig. 13B is a schematic view showing images (K, Na, Pb, Cl) of other components in fig. 13A. EPMA (Electron Probe microanalyzer) is an apparatus that irradiates an Electron beam onto a surface of a substance, measures a characteristic X-ray generated from the substance, and analyzes constituent elements of the substance. By using EPMA, the constituent elements of the sprayed coating formed on the surface of the base material can be identified, and the ratio (concentration) of the constituent elements of the sprayed coating can be analyzed.

In fig. 12B and 13B, the constituent elements of the respective sprayed coatings of the images (K, Na, Pb, Cl) of the other components are shown as black areas, and the lower area adjacent to the black areas shows the inside of the coatings. As can be seen from comparison of the images (K, Na, Pb, and Cl) of the other components with each other based on fig. 12 (fig. 12A and 12B) and fig. 13 (fig. 13A and 13B), the corrosion component penetrates into the coating in the thermal spray coating using the conventional material, while the corrosion component does not penetrate into the coating in the thermal spray coating using the novel material. As described above, the thermal spray coating film using the novel material is excellent in corrosion resistance under a high-temperature corrosion environment in a simulated waste incinerator, compared with the thermal spray coating film using the conventional material.

While the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that the present invention can be implemented in various different ways within the scope of the technical idea thereof.

Industrial applicability

The present invention relates to a long life of boiler water tubes (heat transfer tubes) of general waste incinerator boilers and the like.

Description of the reference numerals

1, an electric furnace is used for heating,

2, a ceramic boat is arranged in the middle of the boat,

3, a crucible is arranged in the crucible,

4 a molten salt of,

5 a test piece to be tested was placed,

10 of a combustion chamber, and a combustion chamber,

11 a fuel inlet for the fuel to be injected,

12 an oxygen inlet, wherein the oxygen inlet is provided with a plurality of oxygen inlets,

13 of the spark plug, and 13 of the spark plug,

14 a material inlet for feeding the material,

15 a main body of the medical device, wherein,

16 a cooling water inlet is arranged at the bottom of the cooling water tank,

17 cooling water discharge port.

Claims

1. A boiler water pipe for a waste incinerator, which is a boiler water pipe for a waste incinerator in which the surface of a base material is coated with a thermal spray coating film,

the thermal spray coating is formed by stacking flat metal particles and has a structure in which Ni (nickel) is concentrated so as to fill the gaps of the metal particles,

the metal particles are Ni (nickel) -based alloys containing Ni (nickel) as a main component and Cr (chromium), B (boron), Si (silicon), Mo (molybdenum) and Cu (copper),

the thermal spray coating is formed using, as a material, a thermal spray powder obtained by subjecting the surfaces of the respective metal particles to an Ni (nickel) coating treatment.

2. The boiler water pipe of a waste incinerator according to claim 1, wherein said sprayed coating has a porosity of less than 1%.

3. The boiler water pipe for a waste incinerator according to claim 1 or 2, wherein said sprayed coating has a thickness of 100 μm or more and 1000 μm or less.

4. A method for producing a boiler water tube for a waste incinerator, according to any one of claims 1 to 3,

the thermal spraying is made of a thermal spraying powder obtained by performing Ni (nickel) coating treatment on the surfaces of metal particles, wherein the melting point of the metal particles subjected to the Ni (nickel) coating treatment is higher than the melting point of an Ni (nickel) coating film covering the metal particles,

the metal particles are a Ni (nickel) -based alloy containing Ni (nickel) as a main component and Cr (chromium), B (boron), Si (silicon), Mo (molybdenum), and Cu (copper).

5. The method of manufacturing a boiler water tube of a waste incinerator according to claim 4, wherein said Ni (nickel) coating treatment is an electroless Ni (nickel) -P (phosphorus) plating treatment.

6. The method for manufacturing a boiler water pipe for a waste incinerator according to claim 5, wherein said Ni (nickel) coating film formed by said Ni (nickel) coating treatment contains 5 to 10 mass% of P (phosphorus).

7. The method for manufacturing a boiler water pipe for a waste incinerator according to claim 5 or 6, wherein said thermal spraying is a high speed flame spraying method.

8. The method for manufacturing a boiler water tube for a waste incinerator according to claim 5 or 6, characterized in that after said thermal spraying, no melting treatment is performed.

9. The method for manufacturing a boiler water tube for a waste incinerator according to claim 7, wherein said thermal spraying is not followed by melting treatment.