JP2007191780A - Thermal spray apparatus and method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal spray apparatus and a method therefor where the propagation of cracking in the surface of the object to be thermal-sprayed is sealed to be shielded from the environment, and the propagation of the cracking is prevented or suppressed. <P>SOLUTION: The thermal spray apparatus comprises: a spray particle feeder 12 of feeding spray particles; a fuel feeder 13 of feeding fuel; an oxygen feeder 14 of feeding oxygen; and a thermal spraying gun 11 where the spray particles are heated and accelerated by using reaction heat between the fed fuel and oxygen and are collided against the surface 41 of the object to be thermal-sprayed, and a sprayed coating 45 in which compressive stress remains is formed on the surface 41 of the object to be thermal-sprayed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thermal spraying apparatus and method for forming a thermal spray coating in which compressive stress remains on the surface of an object to be sprayed.

  In general, in nuclear power plants that have been used for many years, cracks may be seen in welds of reactor internal structures due to the effects of long-term exposure to high-temperature, high-pressure water with a high oxygen concentration. In most cases, the crack generated in the reactor internal structure due to this aging is stress corrosion cracking (hereinafter referred to as SCC). This SCC occurs when three factors such as material degradation, tensile residual stress, and high oxygen environment are combined in the heat-affected zone accompanying welding during plant construction. Therefore, it has been confirmed that one of the above three items should be improved to suppress the occurrence and development of stress corrosion cracking.

  It is known that preventive maintenance measures and repairs have been taken as countermeasures against SCC generated in the above-described reactor internal structures and the like (see, for example, Patent Documents 1 and 2).

As this preventive maintenance measure, a coating is formed on the surface of the object to be sprayed by plasma spraying in water on the reactor internal structure or the like. When thermal spraying is performed using this plasma, arc, or the like as a heat source, the thermal spray particles adhere to the substrate in a heated and melted state when flying in the plasma flame. The adhered particles generate thermal stress in the cooling process. This thermal stress ultimately generates a tensile stress in the coating of the structure.
Japanese Patent Application Laid-Open No. 08-209322 Japanese Patent Application Laid-Open No. 08-225916

  As described above, as a preventive maintenance measure, a coating is formed on the surface of an object to be sprayed by a plasma spraying method in water on a reactor internal structure or the like.

  However, in this underwater plasma spraying method, since the formed film becomes a tensile residual stress, there is a problem that only a film that is easily peeled off can be formed because of low adhesion strength.

  Also, it was very difficult to form a thick film exceeding 0.3 mm. For this reason, when it tried to thicken a membrane | film | coat, there existed a subject that it was limited to the porous structure containing many pores.

  The present invention has been made to solve the above-described problem, and a thermal spraying apparatus and method for preventing or suppressing the progress of the crack by sealing the crack on the surface of the object to be sprayed and isolating the environment. The purpose is to provide.

  In order to achieve the above object, in the thermal spraying apparatus of the present invention, a thermal spray particle supply machine that supplies thermal spray particles, a fuel supply machine that supplies fuel, an oxygen supply machine that supplies oxygen, the supplied fuel, and A thermal spray gun that forms a thermal spray coating in which compressive stress remains on the surface of the object to be sprayed by heating and accelerating the thermal spray particles using the reaction heat of oxygen to collide with the surface of the object to be sprayed. It is characterized by.

  In order to achieve the above object, in the thermal spraying apparatus of the present invention, a high-pressure gas supply machine that supplies high-pressure gas, and a thermal spray particle supply machine that press-injects thermal spray particles with the high-pressure gas supplied from the high-pressure gas supply machine, A heating heater for heating the high-pressure gas supplied from the high-pressure gas supply device, and heating and accelerating the sprayed particles by introducing the heated high-pressure gas to collide with the surface of the object to be sprayed. A thermal spray gun that forms a thermal spray coating on which the compressive stress remains on the surface of the thermal spray object.

  In order to achieve the above object, in the thermal spraying apparatus method of the present invention, a thermal spray particle accelerating step for heating and accelerating the thermal spray particles using a heat source, and the heated and accelerated thermal spray particles on the surface of the object to be sprayed. The thermal spray particle colliding step for colliding and a thermal spray coating forming step for forming a thermal spray coating in which compressive stress remains on the surface of the object to be sprayed by the collided thermal spray particles are characterized.

  According to the thermal spraying apparatus and the method of the present invention, the thermal spray coating is formed on the surface of the object to be sprayed by using the thermal spraying apparatus, and thereby the stress of the thermal spray coating formed on the surface of the object to be sprayed is set as the compressive residual stress. In addition, the crack can be prevented or suppressed by sealing the crack on the surface of the object to be sprayed and isolating the environment.

  Embodiments of a thermal spraying apparatus and method according to the present invention will be described below with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

  FIG. 1 is a longitudinal sectional view showing an example in which the thermal spraying apparatus according to the first embodiment of the present invention is applied to a reactor internal structure.

  As shown in this figure, a reactor internal structure 61 is installed in a reactor pressure vessel (not shown). The reactor internal structure 61 has a shroud 2 that forms a trunk and the like. Inside the shroud 2 is installed an upper grid plate 3 that loads a plurality of fuel assemblies (not shown) and supports the upper portion thereof. The lower part of the fuel assembly is supported by a core support plate (not shown) in the shroud 2. Since the above-described shroud 2 forming the body portion is formed by welding a plurality of plates, a plurality of vertical and horizontal weld lines 4 exist on the surface of the shroud 2.

  In a nuclear plant generally used for years, cracks may be seen in the weld line 4 of the shroud 2 of the reactor internal structure 61 due to exposure to high temperature and high pressure water with high oxygen concentration. . In most cases, this crack is SCC caused by this aging. This SCC occurs when three factors such as material degradation, tensile residual stress, and high oxygen environment are combined in the heat-affected zone accompanying welding during plant construction. Therefore, it is known that one of the above three items should be improved to suppress the occurrence and progress of SCC.

  Here, in order to prevent the progress of the crack by sealing the crack on the surface of the object to be sprayed by thermal spraying and isolating the environment, the preventive maintenance or repair of the reactor internal structure 61 is performed. A thermal spraying device 1 is arranged. As this thermal spraying method, there is a high-speed flame spraying method or a cold spraying method. This method uses a process of suppressing the progress of cracks by making the stress state of the formed sprayed coating a compressive stress.

  In addition, said thermal spraying apparatus 1 is conveyed by the access apparatus which is not shown in figure through the upper grid plate 3 in the shroud 2 and to the vicinity of the welding line 4 which is an object to be sprayed.

  FIG. 2 is a configuration diagram showing a schematic structure of a thermal spraying apparatus using a high-speed flame spraying method.

  As shown in this figure, a high-speed flame spray gun 11 which is a high-speed flame spraying device is configured such that fuel and oxygen gas are introduced into this, and a thermal spray frame 23 is formed by utilizing a combustion reaction.

  Spray particles and spray powder are introduced into the fuel / oxygen mixing chamber 21 of the high-speed flame spray gun 11 from the spray particle supply machine 12 via a pipe. Fuel is supplied from the fuel supply machine 13 into the fuel / oxygen mixing chamber 21 through a pipe. In addition, oxygen is also introduced from the oxygen supply machine 14 via a pipe.

  The fuel used here is a liquid fuel typified by kerosene (kerosene) or a gaseous fuel such as propylene or hydrogen, as long as it can form the thermal spray frame 23 by mixing with oxygen and igniting. This ignition device may be provided inside the high-speed flame spray gun 11 or separately provided outside the high-speed flame spray gun 11. As an ignition method, it is common to use an electrically generated spark, but it may be ignited by direct approaching a fire.

  The formed thermal spray frame 23 is a high-speed frame of Mach unit with a speed of 1400 to 3000 m / s, and the temperature of the frame is 3000 ° C. or less, which is lower than that of plasma spraying of 10,000 ° C. In this thermal spray frame 23, thermal spray particles of a material for which a thermal spray coating 45, which is a surface layer, is to be formed on the surface 41 to be sprayed are supplied from the thermal spray particle feeder 12 together with a powder supply gas. At this time, the particle diameter of the sprayed particles is selected and used in the range of 0.5 to 200 μm according to the material. Further, in this figure, the structure is such that spray particles are supplied from the inside of the high-speed flame spray gun 11, but a system in which the spray particles are supplied from the outside of the high-speed flame spray gun 11 may be used.

  The above-mentioned sprayed particles and sprayed powder are made of stainless steel, which is the same material as the shroud 2, when spraying is performed in the vicinity of the weld line 4 inside the shroud 2 which is the reactor internal structure 61 as shown in FIG. SUS304 or SUS316L powder is used as the material, and the particle size is preferably in the range of 5 to 100 μm.

  Here, the result of the thermal spraying test constructed by the high-speed flame spraying method will be described.

  FIG. 3 is a table showing spraying conditions when the spraying test is performed by the high-speed flame spraying method of FIG. Spraying was performed by the high-speed flame spraying method using the above-mentioned sprayed particles under the conditions shown in FIG. The state of the sprayed particles when colliding with the surface of the object to be sprayed was measured with a monitoring device. The temperature of the spray particles was 1500 to 2000 ° C., and the speed of the spray particles was 500 to 1000 m / s. As a result of performing thermal spraying on the object to be sprayed under these conditions, the stress of the formed film showed a value between -400 to 0 MPa, and the compressive stress remained.

  According to the present embodiment, by applying thermal spraying on the surface of the object to be sprayed using the high-speed flame spraying method, the stress of the sprayed coating formed on the surface of the object to be sprayed can be made the compressive residual stress. . By forming this compressive residual stress, the crack on the surface of the object to be sprayed is sealed to isolate the environment, thereby preventing or suppressing the progress of the crack.

  FIG. 4 is a configuration diagram showing a schematic structure of a thermal spraying apparatus using a cold spray method.

  As shown in this figure, a cold spray gun 15 which is a cold spray device is one in which an inert gas or the like is introduced therein and heated by a heater 18 to form a thermal spray frame 23.

  Inside the cold spray gun 15, high pressure gas is supplied from the high pressure gas supply device 16 through the heater 18 into the cold spray gun 15. Further, the high-pressure gas is also supplied from the high-pressure gas supply unit 16 to the thermal spray particle supply unit 17. With this high-pressure gas, spray particles and spray powder are introduced into the cold spray gun 15 from the spray particle feeder 17 via the pipe.

  In the present embodiment, compressed air, pressurized inert gas such as helium or nitrogen is supplied from the high-pressure gas supplier 16. One of the high-pressure gases is supplied to the cold spray gun 15 while being heated to about 500 ° C. when passing through the heater 18. The other pressurized gas supplies spray particles and spray powder to the inside of the cold spray gun 15 via the spray particle feeder 17. The supplied sprayed particles are heated and accelerated by the high-pressure gas described above. The heated and accelerated sprayed particles collide with the object to be sprayed 41 to form a sprayed coating 45.

  According to the present embodiment, although the thermal spray particles and the thermal spray powder are accelerated, the temperature rise does not rise above the pressurized gas temperature. The compressive stress generated at the time of collision with the object to be sprayed is larger than the thermal stress generated in step. Thus, since the stress of the formed sprayed coating is in a compressed state, a coating that is difficult to peel off is formed. Further, since this thermal spray coating is in a compressed state, it is possible to easily form a thick film exceeding 0.3 mm that would be peeled off by plasma spraying.

  FIG. 5 is an explanatory view of a schematic structure of a thermal spraying apparatus using a high-speed flame spraying method provided with a shield cover 22, (a) is this configuration diagram, and (b) is a bottom view. In this figure, a shield cover 22 is added to the embodiment of FIG. 2, and the same or similar parts as those of the embodiment of FIG. To do.

  As shown in this figure, spray particles and spray powder are introduced into the fuel / oxygen mixing chamber 21 inside the high-speed flame spray gun 11 from the spray particle supply machine 12 via a pipe. Fuel is supplied from the fuel supply unit 13 to the fuel / oxygen mixing chamber 21 via a pipe. In addition, oxygen is also introduced from the oxygen supply machine 14 via a pipe.

  When performing the above-described thermal spraying in water, thermal spraying is possible by simply attaching a cylindrical shield cover 22 around a commercially available high-speed flame spray gun 11 as shown in the figure. The shield cover 22 has a water-cooling structure as necessary, and spraying is possible within a range of 0 to 50 mm with respect to the distance from the tube tip to the object to be sprayed. An ignition device 24 is provided in the vicinity of the high-speed flame spray gun 11 in the shield cover 22. A thermal spray frame 23 is formed by igniting the mixed gas of fuel and oxygen with the spark generated from the ignition device 24.

  Further, a monitoring device 25 for monitoring the spraying state is provided at the tip of the shield cover 22. The monitoring device 25 is a device that can observe the situation in which the sprayed particles and the sprayed powder are flying in the spray frame 23, and can measure the temperature and speed when the sprayed particles pass through the tip of the shield cover 22. it can.

  According to the present embodiment, thermal spraying can be performed while observing with the monitoring device 25. For example, when a change occurs in the thermal spray frame 23 due to equipment failure or poor supply of fuel or oxygen during thermal spraying, a change occurs in the thermal and kinetic energy applied to the thermal spray particles, resulting in an adverse effect on the coating quality. I will give it. Even in such a situation, spraying can be performed while observing with the monitoring device 25, and a stable sprayed coating can always be formed.

  FIG. 6 is a configuration diagram showing a schematic structure of a thermal spraying apparatus provided with a local chamber 31. In this figure, a local chamber 31 is added to the embodiment of FIG. 1, and the same or similar parts as those of the embodiment of FIG. To do.

  When the above-described spraying operation is performed in water, an isolation wall composed of a local chamber 31 is provided around the spraying device 1. With this isolation wall, a sprayed coating in a compressed state can be formed on the surface of the object 41 to be sprayed. Moreover, when spraying in water by this method, shielding properties can be further enhanced by supplying a gas such as compressed air or nitrogen to the inside as necessary.

  According to the present embodiment, the thermal spray coating can be formed in the vicinity of the weld line 4 of the shroud by using the thermal spraying device provided with the local chamber 31. Even if stress corrosion cracking occurs in the vicinity of the part to be sprayed, the environment can be shielded from water with high oxygen concentration in the furnace by forming a sprayed coating on the surface by the above-mentioned spraying method. , Crack growth can be prevented. Further, preventive maintenance measures against the occurrence of stress corrosion cracking can be taken for a portion where no crack has occurred.

  Here, a blast process as a pre-process for thermal spraying will be described.

  In general, blasting is used as a pretreatment for thermal spraying. In this method, particles and powder made of alumina or steel are ejected by compressed air and collide with the object to be sprayed 41, and the surface is cleaned and cut to form an uneven surface.

  In this embodiment, spray particles and spray powder are supplied into the mixed gas of fuel and oxygen before ignition as pretreatment, and only the gas pressure ejected from the tip of the spray gun is used to spray particles and spray. By spraying the powder, the surface of the object to be sprayed can be pretreated with the sprayed particles.

  Even after the gas mixture is ignited to form a thermal spray frame, by increasing the particle size of the thermal spray particles to be used, acceleration is performed while flying in the thermal spray frame, but heating is suppressed. The particles do not adhere to the surface 41 to be sprayed and collide and bounce off. By the effect of this collision, the surface of the object to be sprayed 41 is cleaned, and an uneven surface is formed on the surface 41 to be sprayed.

  The result of the blast treatment test as the thermal spraying pretreatment will be described. When spraying stainless-based particles and powder, generally sprayed particles and sprayed powder of about 15 to 50 μm are used. In this blast treatment test, 100 to 1000 μm spray particles were introduced. As a result of the blast treatment test, the sprayed coating was not formed on the surface of the object to be sprayed, and the surface oxides and impurities were removed. Further, the surface roughness of the target surface of the blast treatment can be controlled from the center line average roughness Ra: 0.2 μm to 70 μm and the ten-point average roughness Rz: 1 μm to 300 μm. It was confirmed that a surface was formed.

  According to the present embodiment, by spraying spray particles and spray powder using only the gas pressure ejected from the tip of the spray gun, and colliding the spray particles with the surface of the object to be sprayed, the surface oxide And impurities are removed. Moreover, the blast process as a thermal spraying pretreatment can be performed by purifying and cutting the surface to form an uneven surface.

  Here, a method for repairing a crack generated on the surface of the object to be sprayed will be described.

  FIG. 7 is a cross-sectional view showing stress corrosion cracks generated on the surface of the object to be sprayed. As shown in the figure, as a repair method when a crack 42 is generated on the surface of the object 41 to be sprayed, a method of forming a surface layer for shielding the crack 42 from the environment, machining the crack 42, There is a method of removing by electric discharge machining.

  FIG. 8 is a cross-sectional view showing a sprayed coating formed on a stress corrosion cracked portion generated on the surface of the object to be sprayed. As shown in FIG. 7, when the thermal spraying method of the present embodiment is adopted as a method for shielding the crack 42 from the environment, it is possible to shield the environment by forming a sprayed coating 45 on the surface of the crack 42. . In the thermal spraying method of this embodiment, compressive stress remains in the formed thermal spray coating. In addition to the structure that does not easily peel off due to this compressive residual stress, the occurrence of cracks 42 in the sprayed layer 45 can be prevented or suppressed.

  FIG. 9 is a cross-sectional view showing a portion 43 where stress corrosion cracks generated on the surface of the object to be sprayed are removed by processing. As shown in this figure, when the crack 42 shown in FIG. 7 is removed by machining or electric discharge machining, a tensile residual stress accompanying the machining is generated in the portion 43 from which the crack has been removed by this machining, and the state remains unchanged. Then, stress corrosion cracking may occur.

  FIG. 10 is a cross-sectional view showing a thermal spray coating 44 formed by thermal spraying on the processed portion of FIG. When the crack 42 in FIG. 9 is removed by machining or electric discharge machining, as shown in this figure, the sprayed coating 44 is formed by spraying the portion 43 from which the crack 42 has been removed by machining. By forming this thermal spray coating 44, the thermal spray target 41 can be surrounded by the thermal spray layer 44 and returned to its original state.

  According to the present embodiment, the thermal spray coating 44 formed as described above has a compressive residual stress and thus has a structure that does not easily peel off, and prevents the thermal spray layer 44 from cracking or Can be suppressed.

  FIG. 11 is a side view showing the thermal spray coating 46 to which compressive stress is applied. As shown in this figure, a thermal spray coating 46 in a state of compressive stress is formed on at least one layer in contact with the object to be sprayed 41. A thermal spray coating 47 in a tensile stress state is formed above the thermal spray coating 46 in a compressive stress state.

  According to the present embodiment, by setting at least one layer in contact with the object to be sprayed 41 to be in a state of compressive stress, not only the adhesion strength can be ensured, but also the effect of improving the stress on the surface of the object to be sprayed 41 is achieved. I can expect. In addition, the second and subsequent layers have the advantage that even if the tensile stress is changed by changing the material and spraying conditions, the adhesion strength between the sprayed layers does not decrease because the sprayed coating is formed by the same spraying process. .

  FIG. 12 is a configuration diagram showing a schematic structure of the powder recovery apparatus.

  This figure is provided by adding a suction device 51 to the embodiment of FIG. 5, and the same or similar parts as those of the embodiment of FIG. To do.

  In general, for example, when the thermal spray coating 45 is formed on the surface of the object 41 to be sprayed by the thermal spraying method of FIG. 5, the thermal spray coating is formed by supplying powder or wire to a heat source. However, the deposition efficiency of sprayed particles or the like is 50% or less regardless of which spraying method is used. That is, the remaining 50% or more of the sprayed particles and the like do not adhere and float in the air or water.

  As shown in this figure, spray particles and spray powder are introduced into the fuel / oxygen mixing chamber 21 inside the high-speed flame spray gun 11 from the spray particle supply machine 12 via a pipe. Fuel is supplied from the fuel supply unit 13 to the fuel / oxygen mixing chamber 21 via a pipe. In addition, oxygen is also introduced from the oxygen supply machine 14 via a pipe.

  As described above, the cylindrical shield cover 22 is attached around the high-speed flame spraying gun 11 in order to perform high-speed flame spraying in water. A leakage prevention cover 53 that is in contact with the object to be sprayed 41 is further provided at the tip of the shield cover 22. A suction device 51 is provided on the high-speed flame spray gun 11 via a suction pipe 52.

  According to the present embodiment, the thermal spray particles and the thermal spray powder that did not adhere as a coating are floating in the shield cover 22, and these are discharged to the outside of the shield cover 22 by the suction device 51 via the suction pipe 52. Is done. The sucked spray particles are collected through a filtering mechanism (not shown). As a result, the spray particles do not leak into the water.

  Furthermore, the present invention is not limited to the above-described embodiments, and may be a combination of the high-speed flame spraying method and the cold spray method depending on the shape of the surface of the object to be sprayed and the thickness of the sprayed layer. Modifications may be made and the embodiments of the present invention may be implemented in combination.

The longitudinal cross-sectional view which shows the example which applied the thermal spraying apparatus of embodiment of this invention to the reactor internal structure. The block diagram which shows schematic structure of the thermal spraying apparatus using the high-speed flame spraying method. The table | surface which shows the thermal spraying condition at the time of performing a thermal spraying test by the high-speed flame spraying method of FIG. The block diagram which shows schematic structure of the thermal spraying apparatus using the cold spray method. It is explanatory drawing of the schematic structure of the thermal spraying apparatus using the high-speed flame spraying method provided with the shield cover, (a) is this block diagram, (b) is this bottom view. The block diagram which shows schematic structure of the apparatus provided with the local chamber in the thermal spraying apparatus of FIG. Sectional drawing which shows the stress corrosion crack which generate | occur | produced on the to-be-sprayed target object surface. Sectional drawing which shows the sprayed coating formed in the stress corrosion crack surface which generate | occur | produced in the to-be-sprayed target object surface. Sectional drawing which shows the site | part which removed the stress corrosion crack which generate | occur | produced on the to-be-sprayed target object by processing. Sectional drawing which shows the sprayed coating formed by the thermal spraying in the process site | part of FIG. The side view which shows the thermal spray coating to which the compressive stress was provided. The block diagram which shows schematic structure of a powder collection | recovery apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Spraying device, 2 ... Shroud, 3 ... Upper lattice board, 4 ... Welding line, 11 ... High-speed flame spray gun, 12 ... Spraying particle supply machine, 13 ... Fuel supply machine, 14 ... Oxygen supply machine, 15 ... Cold spray Gun 16, high pressure gas supply machine 17, sprayed particle supply machine 18, heater, 21 fuel / oxygen mixing chamber 22 shield cover 23 spray frame 24 ignition device 25 monitoring device 31 DESCRIPTION OF SYMBOLS ... Local chamber, 41 ... Object to be sprayed, 42 ... Crack, 43 ... Site where crack is removed by processing, 44 ... Thermal spray coating, 45 ... Thermal spray coating, 46 ... Compression stress coating, 47 ... Tensile stress coating, 51 ... suction device, 52 ... suction pipe, 53 ... leakage prevention cover, 61 ... reactor internal structure.

Claims (15)

A thermal spray particle feeder for supplying thermal spray particles;
A fuel supply machine for supplying fuel;
An oxygen supply machine for supplying oxygen;
The thermal spraying is performed by heating and accelerating the thermal spray particles using the reaction heat of the supplied fuel and oxygen and causing the thermal spray particles to collide with the surface of the thermal spray target, thereby forming a thermal spray coating on which the compressive stress remains on the surface With cancer,
A thermal spraying apparatus characterized by comprising: A high-pressure gas supply machine for supplying high-pressure gas;
A thermal spray particle feeder that press-fits thermal spray particles with the high-pressure gas supplied from the high-pressure gas feeder;
A heater for heating the high-pressure gas supplied from the high-pressure gas supply machine;
A thermal spray gun that forms a thermal spray coating in which compressive stress remains on the surface of the object to be sprayed by introducing the heated high-pressure gas to heat and accelerate the spray particles to collide with the surface of the object to be sprayed;
A thermal spraying apparatus characterized by comprising:   The thermal spraying device according to claim 1, further comprising a shield cover for performing thermal spraying in an environment shielded from water around the thermal spraying gun.   The thermal spraying device according to claim 1, further comprising a local chamber for performing thermal spraying in an environment where the thermal spraying gun is locally shielded from water on an outer peripheral portion of the thermal spraying gun.   The thermal spraying device according to claim 1, further comprising a monitoring device for observing the thermal spraying state at or near a tip of the thermal spraying gun.   3. A recovery device for sucking and collecting spray particles that have not been formed as a spray coating by colliding with an object to be sprayed among spray particles ejected from the spray gun. Spraying equipment. A thermal spray particle acceleration step of heating and accelerating the thermal spray particles using a heat source;
A sprayed particle collision step for causing the heated and accelerated sprayed particles to collide with the surface of the object to be sprayed;
A thermal spray coating forming step for forming a thermal spray coating in which compressive stress remains on the surface of the object to be sprayed by the sprayed particles that have collided;
The thermal spraying method characterized by having.   The thermal spraying method according to claim 7, wherein the heat source is combustion energy formed by reacting fuel and oxygen.   The thermal spraying method according to claim 7, wherein the heat source is high-pressure gas energy formed by pressurizing and heating compressed air or an inert gas.   The thermal spray particle collision step further includes a thermal spraying pretreatment step in which the thermal spray target object surface is cleaned by causing the thermal spray particles to collide with the thermal spray target object surface without causing the thermal spray particle to collide with the thermal spray target object surface. The thermal spraying method according to claim 7.   8. The thermal spraying method according to claim 7, wherein in the thermal spray coating forming step, a thermal spray coating in which at least one layer of compressive stress remains is formed on the surface of the object to be sprayed.   The thermal spraying method according to claim 7, wherein the thermal spray coating is formed on a surface of an object to be sprayed in water.   8. The thermal spraying method according to claim 7, wherein when there is a crack on the surface of the object to be sprayed, repair is performed by forming the thermal spray coating on the upper surface of the crack.   8. The thermal spraying according to claim 7, wherein when there is a crack on the surface of the object to be sprayed, the thermal spray coating is formed on the upper surface of a portion where the crack has been removed by processing, and repair is performed. Method.   The thermal spraying method according to claim 7, 13 or 14, wherein repair is performed by forming a thermal spray coating on the surface of the object to be sprayed of a reactor internal structure.

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