Method for applying heat-shielding coating and method for manufacturing heat-resistant material

Abstract

To suppress the cost of a thermal barrier coating in a heat resistant member.SOLUTION: A method for constructing a thermal barrier coating comprises the step of forming a topcoat layer on a bond coat layer formed on a heat resistant alloy base material of an object. The step of forming the topcoat layer comprises forming the topcoat layer by thermally spraying a suspension containing ceramic powder by high speed flame spray while holding the temperature of the topcoat layer at 300°C or more and 450°C or less so that the ratio of the area of a region having coagulated unmelted ceramic powder to that of the cross-section of the topcoat layer is 0.15% or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a method for applying a heat insulation coating and a heat-resistant member.

Background Art

[0002] It is known to provide a thermal barrier coating (TBC) on heat-resistant members exposed to high-temperature combustion gases, such as combustor panels and turbine blades in aircraft engines, and turbine blades and split rings in industrial gas turbines. Such a thermal barrier coating includes a bond coat layer formed on a heat-resistant alloy substrate and a top coat layer as a heat insulation layer formed on the bond coat layer. The bond coat layer is formed on the heat-resistant alloy substrate by, for example, thermal spraying (see, for example, Patent Document 1). Further, the top coat layer may be formed by electron beam physical vapor deposition (EB-PVD) in order to include cracks called longitudinal cracks extending in the thickness direction of the top coat layer in the layer to ensure thermal cycle durability (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The initial cost of equipment for electron beam physical deposition is more than 10 times higher than that of thermal spraying equipment. Furthermore, the running costs for forming layers by electron beam physical deposition are about 10 times higher than those for forming layers by thermal spraying, etc. Moreover, the layer formation rate by electron beam physical deposition is low, only a fraction of that of thermal spraying, etc. Therefore, there is a need for a method to form a topcoat layer at a lower cost while ensuring performance such as heat shielding and thermal cycle durability as a topcoat layer for heat shielding coatings.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure aims to reduce the cost of heat-shielding coatings on heat-resistant members. [Means for solving the problem]

[0006] (1) A method for applying a heat-shielding coating according to at least one embodiment of the present disclosure is: The process includes a step of forming a top coat layer on a bond coat layer formed on a heat-resistant alloy substrate of the object, In the process of forming the topcoat layer, the temperature of the topcoat layer is maintained at 300°C to 450°C, and a suspension containing ceramic powder is sprayed by high-velocity flame spraying to form a topcoat layer in which the ratio of the area of ​​the region where unmelted ceramic powder has aggregated to the area of ​​the cross-sectional area of ​​the topcoat layer is 0.15% or less.

[0007] (2) A heat-resistant member according to at least one embodiment of the present disclosure is The device has the top coat layer formed by the heat-shielding coating application method described in (1) above. [Effects of the Invention]

[0008] According to at least one embodiment of this disclosure, the cost of heat-shielding coatings on heat-resistant members can be reduced. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of a cross-section of a heat-resistant member equipped with a heat-shielding coating applied by a heat-shielding coating application method according to several embodiments. [Figure 2] This diagram shows the appearance of a combustor panel for an aircraft engine, as an example of a heat-resistant component. [Figure 3] This flowchart shows the procedure for applying a heat-shielding coating according to several embodiments. [Figure 4A] This diagram illustrates the general structure of an apparatus related to a method for applying a heat-shielding coating according to several embodiments. [Figure 4B] This figure shows an example of a cooling method to maintain the temperature of the topcoat layer within the temperature range described above. [Figure 5] This graph schematically shows the temperature change of the topcoat layer from the start of thermal spraying. [Figure 6] This graph shows the relationship between the thermal conductivity of the topcoat layer and the temperature during thermal spraying. [Figure 7] This graph shows the relationship between the peeling limit temperature difference and the thermal spraying temperature. [Figure 8] This graph shows the relationship between the delamination limit temperature difference and the length of the transverse crack. [Figure 9] This graph shows the relationship between the coating thickness per thermal spray pass and the thermal spray temperature. [Figure 10A] This table shows the measurement results of the density of longitudinal cracks dispersed in the planar direction. [Figure 10B] This table shows the measurement results for the maximum length of transverse cracks. [Figure 11] This is a diagram illustrating an example of cooling a heat-resistant component. [Figure 12A] This is a diagram illustrating an example of cooling multiple heat-resistant components. [Figure 12B] This figure illustrates another embodiment relating to the cooling of multiple heat-resistant components. [Figure 13] This is a diagram illustrating an example of cooling a heat-resistant component. [Figure 14]It is a diagram for explaining an embodiment regarding cooling of a heat-resistant member. [Figure 15] It is a schematic diagram for explaining the application angle during spraying on a plurality of holes. [Figure 16] It is a graph showing the experimental results regarding the relationship between the diameter of the hole and the blockage rate of the hole by the sprayed material. [Figure 17] It is a table showing the compositions of suspension X and suspension Y used for examining the influence by the region where unmolten ceramic powder has aggregated. [Figure 18A] It is a graph showing the particle size distribution of the solid component of suspension X. [Figure 18B] It is a graph showing the particle size distribution of the solid component of suspension Y. [Figure 19A] It is a SEM image of the solid component of suspension X. [Figure 19B] It is a SEM image of the solid component of suspension Y. [Figure 20] It is a graph showing the relationship between the temperature during spraying and the difference in peeling limit temperature. [Figure 21] It is a graph showing the relationship between the unmelted particle mixing ratio and the difference in peeling limit temperature. [Figure 22] It is a graph showing the relationship between the pH of the suspension and the zeta potential of the ceramic powder in the suspension. [Figure 23] It is a SEM image of the test piece produced by suspension X. [Figure 24] It is a SEM image of the test piece produced by suspension Y.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure thereto, but are merely illustrative examples. For example, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" should not only strictly describe such arrangements, but also describe states of relative displacement with tolerances or angles or distances that allow for the same function to be achieved. For example, expressions such as "identical," "equal," and "homogeneous" that describe things being in an equal state not only describe a state of being strictly equal, but also describe a state in which there is a tolerance or a difference that is sufficient to achieve the same function. For example, expressions describing shapes such as squares or cylinders shall not only represent geometrically precise shapes such as squares or cylinders, but also shapes that include protrusions, chamfers, etc., to the extent that the same effect can be achieved. On the other hand, expressions such as "to possess," "to be equipped with," "to have," "to include," or "to have" a single component are not exclusive expressions that exclude the existence of other components.

[0011] (Regarding heat-shielding coating 3) Figure 1 is a schematic cross-sectional view of a heat-resistant member 1 equipped with a heat-shielding coating 3 applied by a heat-shielding coating application method according to several embodiments. Figure 2 shows the appearance of a combustor panel 1A for an aircraft engine, which is an example of a heat-resistant component 1. Heat-resistant components 1, such as combustor panels 1A and turbine blades for aircraft engines, and turbine blades and segmented rings for industrial gas turbines, are coated with a thermal barrier coating (TBC) 3 for heat shielding of the heat-resistant components 1. In some embodiments of the heat-resistant member 1, a metal bonding layer (bond coat layer) 7 and a top coat layer 9 as a heat shielding layer are formed sequentially on the heat-resistant alloy substrate (base material) 5. That is, in some embodiments, the heat shielding coating 3 includes the bond coat layer 7 and the top coat layer 9.

[0012] In some embodiments, the bond coat layer 7 is composed of an MCrAlY alloy (where M represents a metallic element such as Ni, Co, Fe, or a combination of two or more of these).

[0013] In some embodiments, the topcoat layer 9 may be composed of a ZrO2-based material, for example, YSZ (yttria-stabilized zirconia), which is ZrO2 partially or fully stabilized with Y2O3. In some embodiments, the topcoat layer 9 may also be composed of DySZ (dyspurosis-stabilized zirconia), ErSZ (ervia-stabilized zirconia), Gd2Zr2O7, or Gd2Hf2O7. This results in a heat-shielding coating 3 with excellent heat-shielding properties.

[0014] In some embodiments of the topcoat layer 9, longitudinal cracks Cv extending in the thickness direction of the topcoat layer 9 are dispersed in the plane direction, i.e., the left-right direction and the depth direction of the paper in Figure 1. In addition, in some embodiments of the topcoat layer 9, transverse cracks Ch extending in the plane direction are dispersed. In some embodiments of the heat-shielding coating 3, the structure having multiple longitudinal cracks Cv in the top coat layer 9 can mitigate the generation of thermal stress due to the difference in linear expansion coefficient with the heat-resistant alloy substrate 5, thus providing excellent thermal cycle durability.

[0015] (flowchart) Figure 3 is a flowchart showing the procedure for applying a heat-shielding coating according to several embodiments. The application method for a heat-shielding coating according to several embodiments includes a step S10 for forming a bond coat layer 7 and a step S20 for forming a top coat layer 9.

[0016] In some embodiments, step S10 for forming the bond coat layer 7 is a step of forming the bond coat layer 7 on the heat-resistant alloy substrate 5 by thermal spraying. In some embodiments, step S10 for forming the bond coat layer 7 may be a step of forming the bond coat layer on the heat-resistant alloy substrate 5 by high-velocity flame spraying (HVOF), for example. In the following description, step S10 for forming the bond coat layer 7 is assumed to be a step of forming the bond coat layer 7 on the heat-resistant alloy substrate 5 by high-velocity flame spraying. In other words, in some embodiments, in step S10 for forming the bond coat layer 7, powder such as MCrAlY alloy as a thermal spray material is sprayed onto the surface of the heat-resistant alloy substrate 5 by high-speed flame spraying.

[0017] In some embodiments, the surface roughness of the bond coat layer 7 is preferably 8 μm or more in terms of arithmetic mean roughness Ra, in order to improve adhesion with the top coat layer 9.

[0018] In some embodiments, step S20 for forming the topcoat layer 9 is a step for forming the topcoat layer 9 on a bond coat layer 7 formed on a heat-resistant alloy substrate 5 of the heat-resistant member 1, which is the object to be sprayed. In some embodiments, in step S20 for forming the topcoat layer 9, the topcoat layer is formed by spraying a suspension containing ceramic powder by high-velocity flame spraying. That is, in some embodiments, the spraying performed in step S20 for forming the topcoat layer 9 is high-velocity flame spraying with a suspension (S-HVOF). In some embodiments, in step S20 for forming the topcoat layer 9, a suspension in which ceramic powder as a spray material is dispersed in a solvent is sprayed onto the surface of the bond coat layer 7 by high-velocity flame spraying. In high-velocity flame spraying with a suspension, the spray material TM supplied as a suspension is blown onto the surface of the object to be sprayed by a combustion flame jet flow CF (see Figure 4B described later). The thermal spraying conditions in step S20, which forms the topcoat layer 9, will be explained in detail later.

[0019] Figure 4A is a diagram illustrating the schematic of an apparatus related to a method for applying a heat-shielding coating according to several embodiments. As shown in Figure 4A, in some embodiments of the heat-shielding coating application method, the heat-shielding coating 3 is applied using a thermal spray gun 30, a mobile device 50 for the thermal spray gun 30, and a dust collection hood 70. In addition to the devices shown in Figure 4A, some embodiments of the heat-shielding coating application method also include, although not shown, a thermal spray control panel, a control device for controlling the drive of the mobile device 50, and a thermal spray material supply device. When applying the heat-shielding coating 3, if it is necessary to fix the heat-resistant member 1, which is the object to be coated with the heat-shielding coating 3, a fixing jig 91 may be used, and if it is necessary to continuously rotate the heat-resistant member 1, a rotary drive device (not shown) may be used.

[0020] In some embodiments, the moving device 50 is, for example, an industrial robot, but it may also be a scanning device having a slide axis that can move in multiple directions, such as an NC device.

[0021] As shown in Figure 4A, in some embodiments of the method for applying a heat-shielding coating, for example, the thermal spray gun 30, the mobile device 50, and the dust collection hood 70 are arranged inside a thermal spray booth 20. The thermal spray booth 20 forms a space partitioned from the surroundings for sound insulation and to prevent dust from scattering into the surroundings. For example, the thermal spray booth 20 may be a box-shaped structure placed in a work room, a section of a work room partitioned by walls, or a dedicated room set up inside a building. The heat-resistant component 1, which is the object to which the heat-shielding coating 3 is applied, has the heat-shielding coating 3 formed inside the thermal spray booth 20.

[0022] In some embodiments of the heat-shielding coating application method, as described above, the step S10 for forming the bond coat layer 7 is performed by high-velocity flame spraying (HVOF), and the step S20 for forming the top coat layer 9 is performed by high-velocity flame spraying (S-HVOF) using a suspension. Therefore, in some embodiments of the heat-shielding coating application method, for example, by changing the spray gun 30 and the spray material supply device between the step S10 for forming the bond coat layer 7 and the step S20 for forming the top coat layer 9, the step S10 for forming the bond coat layer 7 and the step S20 for forming the top coat layer 9 can be performed in the same spray booth 20. In some embodiments of the heat-shielding coating application method, when performing the step of forming the top coat layer 9 in step S20 after the step of forming the bond coat layer 7 in step S10, it is not necessary to move the heat-resistant member 1 to a different thermal spray booth than the one in which the step of forming the bond coat layer 7 in step S10 was performed. This eliminates the effort of moving the heat-resistant member 1 to a different thermal spray booth and the effort of setting up the heat-resistant member 1 after moving it until thermal spraying begins.

[0023] (Regarding the construction conditions in step S20, which involves forming the top coat layer 9) Conventionally, topcoat layers were sometimes formed by electron beam physical vapor deposition (EB-PVD) to ensure thermal cycle durability by incorporating cracks, known as longitudinal cracks, that extend in the thickness direction of the topcoat layer. However, the initial cost of equipment for electron beam physical deposition is more than 10 times higher than that of thermal spraying equipment, etc. Furthermore, the running costs for forming layers by electron beam physical deposition are about 10 times higher than the running costs for forming layers by thermal spraying, etc. Moreover, the layer formation rate by electron beam physical deposition is low, only a fraction of the rate by thermal spraying, etc. Therefore, there is a need for a method to form a topcoat layer at a lower cost while ensuring performance such as heat shielding and thermal cycle durability as a topcoat layer for heat shielding coatings.

[0024] As a result of diligent research by the inventors, it was found that in step S20 for forming the topcoat layer 9, by maintaining the temperature of the topcoat layer 9 between 300°C and 450°C while spraying a suspension containing ceramic powder by high-speed flame spraying, it is possible to ensure performance such as heat shielding and thermal cycle durability equivalent to that obtained when the topcoat layer is formed on the bond coat layer by electron beam physical deposition. Therefore, in the heat-shielding coating application method according to several embodiments, in step S20 for forming the top coat layer 9, the top coat layer 9 is formed by spraying a suspension containing ceramic powder by high-speed flame spraying while maintaining the temperature of the top coat layer 9 at 300°C or higher and 450°C or lower. The inventors' findings will be explained later.

[0025] This allows for the formation of the topcoat layer 9 on the bond coat layer 7 by electron beam physical deposition at a lower running cost and in a shorter time. Furthermore, by forming the topcoat layer 9 by high-speed flame spraying using a suspension, the cost of introducing equipment for forming the topcoat layer 9 can be significantly reduced.

[0026] Furthermore, some heat-resistant members 1 according to certain embodiments have a top coat layer 9 formed by a heat-shielding coating application method according to some embodiments. This makes it possible to reduce the manufacturing cost of the heat-resistant component 1.

[0027] Furthermore, in step S20, where the topcoat layer 9 is formed, it is preferable to form the topcoat layer 9 by thermal spraying a suspension containing ceramic powder using high-velocity flame spraying while maintaining the temperature of the topcoat layer 9 at 300°C to 400°C. This further improves the performance of the heat-shielding coating, such as its heat-shielding properties and thermal cycle durability.

[0028] Whether the temperature of the topcoat layer 9 is maintained within the above-mentioned temperature range can be confirmed by measuring it with a non-contact thermometer, such as a thermal viewer that detects temperature using infrared light.

[0029] Furthermore, cooling may be performed as needed to maintain the temperature of the top coat layer 9 within the aforementioned temperature range. In other words, in the heat-shielding coating application method according to some embodiments, in step S20 where the top coat layer 9 is formed, it is preferable to control the temperature of the top coat layer 9 by cooling with a cooling medium. This makes it easier to control the temperature of the topcoat layer 9 within the aforementioned temperature range, thus stabilizing the performance of the heat-shielding coating 3, such as its heat shielding properties and thermal cycle durability.

[0030] Figure 4B shows an example of a cooling method to maintain the temperature of the topcoat layer 9 within the temperature range described above. In the example shown in Figure 4B, the heat-resistant member 1 is an axial member. In the example shown in Figure 4B, the topcoat layer 9 is formed on the heat-resistant member 1 while it is being rotated by a rotary drive device (not shown) for continuously rotating the heat-resistant member 1. In the example shown in Figure 4B, the heat-resistant member 1 is held by a gripping part 92 of a rotary drive device (not shown) and rotates together with the gripping part 92. In the example shown in Figure 4B, the heat-resistant member 1 is cooled by a cooling medium CM blown out from a cooling nozzle 81, for example. In the example shown in Figure 4B, in order to suppress the effect of the combustion flame jet flow CF on the cooling medium CM blown out from the cooling nozzle 81, it is preferable that the cooling medium CM be blown out not to the surface of the topcoat layer 9, but to the area 1a of the heat-resistant member 1 where the topcoat layer 9 is not formed, or to the gripping portion 92 that grips the heat-resistant member 1. Other examples of cooling the heat-resistant component 1, as well as the type of cooling medium CM, will be explained later.

[0031] Figure 5 is a schematic graph showing the temperature change of the topcoat layer 9 from the start of thermal spraying. The temperature of the topcoat layer 9 increases as time passes from the time thermal spraying for the formation of the topcoat layer 9 begins. As shown in the example in Figure 4B, by cooling with a cooling medium CM, the temperature of the topcoat layer 9 during thermal spraying can be kept stable within the temperature range described above. In other words, in the heat-shielding coating application method according to some embodiments, in step S20 of forming the top coat layer 9, it is preferable to ensure that the average value of the temperature of the top coat layer 9 in a stable state after the temperature rises after the start of thermal spraying is kept within the above-mentioned temperature range. In the following explanation, this average value will also be referred to as the thermal spray temperature Ta. In addition, in some embodiments of the heat-shielding coating application method, it is not necessary to preheat the heat-resistant member 1 on which the bond coat layer 7 is formed before starting thermal spraying for the formation of the top coat layer 9.

[0032] The inventors' findings are described below. Figure 6 is a graph showing the relationship between the thermal conductivity (relative value) of the topcoat layer 9 and the thermal spray temperature Ta for test specimen A, test specimen B, and test specimen C, which have a thermal spray temperature Ta of 413°C, 477°C, and 586°C, respectively. Figure 7 is a graph showing the relationship between the peel limit temperature difference ΔT (relative value) and the thermal spray temperature Ta for test specimens A, B, and C. Figure 8 is a graph showing the relationship between the peel limit temperature difference ΔT (relative value) and the length of the transverse crack Ch (transverse crack length) for test specimens A, B, and C. Figure 9 is a graph showing the relationship between the deposition film thickness per thermal spray pass (relative value) and the thermal spray temperature Ta for test specimens A, B, C, and D, where the thermal spray temperature Ta was 678°C. Figure 10A is a table showing the measurement results of the density of longitudinal cracks Cv dispersed in the planar direction for test specimens A, B, and C. Figure 10B is a table showing the measurement results for the maximum length of transverse cracks Ch for test specimens A, B, and C.

[0033] In Figure 6, the thermal conductivity of the topcoat layer 9 is expressed as a relative value, with the thermal conductivity of the topcoat layer formed by electron beam physical vapor deposition (EB-PVD) set to 1. Similarly, in Figures 7 and 8, the peeling limit temperature difference ΔT of the topcoat layer 9 is expressed as a relative value with the peeling limit temperature difference ΔT of the topcoat layer formed by electron beam physical deposition set to 1. Note that the peeling limit temperature difference ΔT in Figures 7 and 8 is the temperature difference at which peeling is estimated to occur in the heat-shielding coating 3 when this temperature difference ΔT is applied in a test that is repeated 1000 times. In Figure 9, the adhesion thickness of the topcoat layer 9 per pass is expressed as a relative value, with the adhesion thickness per pass at a thermal spraying temperature Ta of 450°C set to 1. In order to obtain the data shown in Figures 10A and 10B, the data was acquired by observing micrographs of the cross-sections obtained by cutting each test specimen along the thickness direction of the topcoat layer 9. In addition, in Figures 10A and 10B, data was acquired at six different observation sites (six fields of view) on the cross-section. In acquiring the data shown in Figures 10A and 10B, the field of view corresponding to the left-right direction in Figure 1 was 1.09 mm in each microscope image. Therefore, the number of longitudinal fissures Cv and the maximum length of transverse fissures Ch observed within this field of view were obtained.

[0034] The thermal spraying conditions for test specimens A, B, C, and D, other than the thermal spraying temperature Ta, are as follows: Test specimens A to D are cylindrical specimens as shown in Figure 4B. A topcoat layer 9 was formed on the bond coat layer 7 formed on the outer circumference of test specimens A to D by high-speed flame spraying of a suspension. The traverse speed of the thermal spray gun 30 is 100 mm / second. The film thickness of the topcoat layer 9 is 0.5 mm. The rotation speed of the cylindrical test specimen is 1200 rpm. During thermal spraying of the test specimen, the thermal spray gun 30 is moved from the starting position for film deposition on one side in the vertical direction shown in Figure 4B to the other side while depositing the film. After the thermal spray gun 30 reaches the end position for film deposition on the other side, the thermal spray gun 30 is moved in the depth direction of the paper in Figure 4B to avoid the combustion flame jet CF from hitting the test specimen, and then moved towards the one side in the vertical direction shown in Figure 4B. Then, the thermal spray gun 30 is moved back to the starting position for film deposition in the depth direction of the paper in Figure 4B, and the above operation is repeated thereafter to form the topcoat layer 9.

[0035] As shown in Figure 6, by setting the thermal spraying temperature Ta to 450°C or lower, the thermal conductivity of the topcoat layer 9 can be made equivalent to or lower than that of the layer formed by electron beam physical deposition. Furthermore, as shown in Figure 6, the thermal conductivity of the topcoat layer 9 can be further reduced by setting the thermal spraying temperature Ta to 400°C or lower. As shown in Figure 7, by setting the thermal spraying temperature Ta to 400°C or lower, the peeling limit temperature difference ΔT of the topcoat layer 9 can be made equivalent to or greater than that when formed by electron beam physical deposition. Furthermore, the peeling limit temperature difference ΔT of the topcoat layer 9 may be around 0.8 as a relative value in Figure 7. Therefore, by setting the thermal spraying temperature Ta to 450°C or lower, the peeling limit temperature difference ΔT of the topcoat layer 9 can be set to be greater than or equal to the required temperature difference. Therefore, the thermal spray temperature Ta should ideally be 450°C or lower, and even better, 400°C or lower.

[0036] As shown in Figures 8 and 10B, it can be seen that the length of transverse cracks Ch tends to increase as the thermal spray temperature Ta increases. Furthermore, it can be seen that the peeling limit temperature difference ΔT of the topcoat layer 9 tends to decrease as the length of transverse cracks Ch increases. Since the growth of transverse cracks Ch causes peeling of the topcoat layer 9 and reduces thermal cycle durability, it is desirable for the length of transverse cracks Ch to be small. Note that each plot shown in Figure 8 is based on the data shown in Figure 10B.

[0037] As shown in Figure 10A, the density of longitudinal cracks Cv dispersed in the plane increases as the thermal spray temperature Ta increases. A higher density of longitudinal cracks Cv dispersed in the plane improves thermal cycle durability, but increasing the density of longitudinal cracks Cv dispersed in the plane tends to increase the length of transverse cracks Ch. Therefore, a density of longitudinal cracks Cv dispersed in the plane of about 4 cracks / mm is sufficient.

[0038] As shown in Figure 9, when the thermal spraying temperature Ta decreases, the thickness of the coating per thermal spray pass decreases. Therefore, when the thermal spraying temperature Ta decreases, the productivity of the topcoat layer 9 decreases. As shown in Figure 9, when the thermal spraying temperature Ta falls below 300°C, the coating thickness per thermal spray pass is less than half of what it is when the thermal spraying temperature Ta is 450°C. Therefore, the thermal spray temperature Ta is preferably 300°C.

[0039] (Regarding the cooling of heat-resistant component 1) Figure 11 is a diagram illustrating an example of cooling the heat-resistant component 1. Figure 12A is a diagram illustrating an example of cooling multiple heat-resistant components 1. Figure 12B is a diagram illustrating another embodiment relating to the cooling of multiple heat-resistant members 1. Figure 13 is a diagram illustrating an example of cooling the heat-resistant component 1. Figure 14 is a diagram illustrating an example of cooling the heat-resistant component 1.

[0040] As shown in Figure 11, for example, when a top coat layer 9 is formed on one surface of a plate-shaped heat-resistant member 1, the heat-resistant member 1 may be cooled by blowing a cooling medium CM toward the other surface opposite to the first surface.

[0041] As shown in Figures 12A and 12B, in step S20 for forming the topcoat layer 9, the topcoat layer 9 may be formed by sequentially spraying heat-resistant members 1 attached to multiple jigs 93 and 94. This allows for the efficient formation of a topcoat layer 9 on multiple heat-resistant components 1.

[0042] In other words, as shown in Figure 12A, multiple heat-resistant members 1 may be arranged in a line, and thermal spraying may be performed on multiple heat-resistant members 1 in a single pass. In this case, for example, multiple heat-resistant members 1 arranged in a linear or planar manner may be held by a jig 93. As shown in Figure 12A, each heat-resistant member 1 may be cooled by blowing the cooling medium CM toward the side of the heat-resistant member 1 that is opposite to the side forming the top coat layer 9, when multiple heat-resistant members 1 are arranged in a row. Furthermore, as shown in Figure 12A, if multiple heat-resistant members 1 are arranged side by side and thermal spraying is performed on multiple heat-resistant members 1 in one pass, the interval between thermal spraying passes becomes longer compared to when thermal spraying is performed on a single heat-resistant member 1, so the temperature of the topcoat layer 9 does not rise easily. For this reason, if the thermal spraying temperature Ta can be maintained within the above-mentioned temperature range without cooling each heat-resistant member 1 by blowing out the cooling medium CM, cooling with the cooling medium CM is not essential.

[0043] As shown in Figure 12B, the heat-resistant members 1 arranged in a ring shape may be rotated relative to the thermal spray gun 30 to perform thermal spraying on the multiple heat-resistant members 1. In this case, for example, the multiple heat-resistant members 1 arranged in a ring shape may be held by a jig 94. That is, it is preferable that the jig 94 is capable of holding the multiple heat-resistant members 1 arranged in a ring shape. Then, in step S20 for forming the top coat layer 9, it is preferable to sequentially spray the multiple heat-resistant members 1 while rotating the multiple heat-resistant members 1 held by the jig 94 and the thermal spray gun 30 relative to each other.

[0044] Alternatively, the multiple heat-resistant members 1 arranged in a ring shape may be fixed in place and the thermal spraying gun 30 may be rotated to perform thermal spraying, or the thermal spraying gun 30 may be fixed in place and the multiple heat-resistant members 1 arranged in a ring shape may be rotated to perform thermal spraying. When multiple heat-resistant components 1 are rotated, a speed difference is created between each heat-resistant component 1 and the surrounding air. This provides a cooling effect similar to that obtained when air is blown onto each heat-resistant component 1, allowing each heat-resistant component 1 to be cooled efficiently.

[0045] For example, as shown in Figures 13 and 14, if the heat-resistant member 1 has a plurality of holes 110 opened on the surface of the heat-resistant alloy substrate 5, such as so-called film cooling holes, the top coat layer 9 may be formed by ejecting gas (cooling medium CM) from the plurality of holes 110. This makes it easier to control the thermal spray temperature Ta within the aforementioned temperature range, thus stabilizing the performance of the heat-shielding coating 3, such as its heat shielding properties and thermal cycle durability.

[0046] Furthermore, if, for example, a combustor panel 1A as shown in Figure 2 has multiple holes communicating between one side and the other side, then, as shown in Figure 13, for example, gas may be injected into the side opposite to the side forming the topcoat layer 9 to cause gas to be ejected from the multiple holes 110.

[0047] Furthermore, if, for example, a plurality of holes 110 in a turbine blade communicate with a cooling passage inside the blade, and the plurality of holes 110 communicate with a passage 120 inside the heat-resistant member 1 (see Figure 14), gas (cooling medium CM) may be supplied to the passage 120 communicating with the plurality of holes 110 to cause the gas to be ejected from the plurality of holes 110.

[0048] (Regarding the cooling medium CM) In some embodiments, the cooling medium CM may be compressed air compressed by a compressor. Using compressed air from a compressor makes it easier to secure the cooling medium (CM), thus suppressing increased cooling costs. The compressed air used as the cooling medium CM may be compressed air produced by a compressor used to generate compressed air for factory power, or it may be compressed air produced by a compressor installed for cooling the heat-resistant component 1.

[0049] In some embodiments, the cooling medium CM may also include dry ice. In other words, the cooling medium CM may be a system in which relatively small particles or powder of dry ice are transported by compressed air, or it may be carbon dioxide, which is vaporized dry ice and has a relatively low temperature. This reduces the risk of the topcoat layer 9 becoming too hot during its formation, and stabilizes the performance of the heat-shielding coating 3, such as its heat-shielding properties and thermal cycle durability.

[0050] (Regarding the suppression of blockage of multiple holes 110 opened on the surface of the heat-resistant alloy substrate 5) As described above, in some embodiments of the heat-resistant member 1, for example, a plurality of holes 110 (hereinafter also referred to as cooling holes 110) may be opened on the surface of the heat-resistant member 1 in order to cool the film. In the case of such a heat-resistant member 1, it is necessary to prevent the material of the heat-shielding coating (thermal spray material) from entering the cooling holes 110 and blocking them during the process of forming the heat-shielding coating. For this reason, for example, if masking pins are inserted into each cooling hole 110 in advance, it is possible to prevent the material of the heat-shielding coating from entering each cooling hole 110 during the process of forming the heat-shielding coating.

[0051] However, when masking pins are used, the masking pins must be removed from each cooling hole 110 after the heat-shielding coating is formed. Therefore, the more cooling holes 110 there are in the heat-resistant member 1, the more effort is required to remove the masking pins. For this reason, it is desirable to be able to prevent the cooling holes 110 from becoming blocked during the heat-shielding coating formation process using a simpler method.

[0052] Therefore, in the heat-shielding coating application method according to some embodiments, for example, in step S10 for forming the bond coat layer 7, the bond coat layer 7 may be formed on the heat-resistant alloy substrate 5 by thermal spraying while gas is ejected from a plurality of holes 110 opened on the surface of the heat-resistant alloy substrate 5. That is, in the heat-shielding coating application method according to some embodiments, for example, step S10 for forming the bond coat layer 7 may be a step in which the bond coat layer 7 is formed on the heat-resistant alloy substrate 5 by thermal spraying while gas is ejected from a plurality of holes 110. In this way, by forming the bond coat layer 7 while ejecting gas from multiple holes 110, the penetration of the bond coat layer material (thermal spray material) into these multiple holes 110 is suppressed. As a result, in step S10 of forming the bond coat layer 7, it is possible to suppress the blockage of these multiple holes 110 by the bond coat layer material.

[0053] As mentioned above, in step S10, for example, in forming the bond coat layer 7, it is preferable to form the bond coat layer 7 on the heat-resistant alloy substrate 5 by high-speed flame spraying while ejecting gas from a plurality of holes 110. This allows the bond coat layer 7 to be formed by high-speed flame spraying while suppressing the blockage of multiple holes 110 by the bond coat layer 7 material.

[0054] Furthermore, in the heat-shielding coating application method according to some embodiments, for example, in step S20 of forming the top coat layer 9, the top coat layer 9 may be formed by thermal spraying onto the bond coat layer 7 formed on the heat-resistant alloy substrate 5 while gas is ejected from a plurality of holes 110 opened on the surface of the heat-resistant alloy substrate 5. That is, in the heat-shielding coating application method according to some embodiments, for example, step S20 of forming the top coat layer 9 may be a step of forming the top coat layer 9 by thermal spraying onto the bond coat layer 7 formed on the heat-resistant alloy substrate 5 while gas is ejected from a plurality of holes 110. In this way, by forming the topcoat layer 9 while ejecting gas from multiple holes 110, the penetration of the topcoat layer material (thermal spray material, i.e., ceramic powder) into these multiple holes 110 is suppressed. This prevents the multiple holes 110 from becoming blocked by the topcoat layer material in step S20 of forming the topcoat layer 9. Furthermore, in step S20, where the topcoat layer 9 is formed, if the temperature of the topcoat layer 9 rises excessively due to thermal spraying, the above-mentioned problems may occur. In such cases, the excessive rise in temperature of the topcoat layer 9 can be suppressed by ejecting gas from multiple holes 110.

[0055] As mentioned above, for example, in step S20 of forming the top coat layer 9, the top coat layer 9 may be formed by spraying a suspension containing ceramic powder by high-speed flame spraying while ejecting gas from a plurality of holes 110. This allows for the formation of the topcoat layer 9 on the bond coat layer 7 by electron beam physical deposition at a lower running cost and in a shorter time. Furthermore, by forming the topcoat layer 9 by high-speed flame spraying using a suspension, the cost of introducing equipment for forming the topcoat layer 9 can be significantly reduced.

[0056] As mentioned above, if, for example, a combustor panel 1A as shown in Figure 2 has multiple holes communicating between one side and the other side, then, as shown in Figure 13, for example, gas can be injected into the side opposite to the side forming the topcoat layer 9 to expel the gas from the multiple holes 110. This makes it easy to expel gas from the multiple holes.

[0057] Furthermore, as shown in Figure 14, if the multiple holes 110 are in communication with the internal passage 120 of the heat-resistant member 1, as described above, gas (cooling medium CM) may be supplied to the passage 120 communicating with the multiple holes 110 to cause the gas to be ejected from the multiple holes 110. By supplying gas to this passage 120, the gas can be easily ejected from the multiple holes 110.

[0058] As described above, suppressing the blockage of the cooling holes 110 by the thermal spray material by ejecting gas from multiple holes during the heat-shielding coating formation process is effective regardless of the thermal spraying method. In other words, it is effective in thermal spraying such as atmospheric pressure plasma spraying (APS), high-velocity flame spraying (HVOF), atmospheric pressure plasma spraying with suspension (S-APS), and high-velocity flame spraying with suspension (S-HVOF).

[0059] Figure 15 is a schematic diagram illustrating the application angle during thermal spraying for multiple holes 110. In some embodiments, the application angle θa during thermal spraying of the hole 110 is the difference in angle between the extending direction of the hole 110 and the spraying direction of the thermal spray material (the extending direction of the nozzle 31 of the thermal spray gun 30). In some embodiments, the inclination angle θb of the hole 110 is the difference in angle between the extending direction of the surface 5a of the heat-resistant alloy substrate 5 and the extending direction of the hole 110.

[0060] When the construction angle θa is around 90 degrees, the holes 110 become blocked by the thermal spray material, and as the construction angle θa gradually decreases from 90 degrees and approaches 0 degrees, the holes 110 tend to become less likely to be blocked. Furthermore, in atmospheric pressure plasma spraying (APS), for example, a high-temperature plasma jet is used to melt the spray material and adhere it to the substrate. In contrast, in high-velocity flaming (HVOF) and supersonic high-velocity flaming with suspension (S-HVOF), the spray material is made to adhere to the substrate by impacting it at supersonic speeds. Therefore, as the application angle θa gradually decreases from 90 degrees, high-velocity flaming (HVOF) and supersonic high-velocity flaming with suspension (S-HVOF) tend to make it more difficult for the holes 110 to be blocked than in atmospheric pressure plasma spraying (APS).

[0061] In addition, in the heat-shielding coating application method according to some embodiments, in step S20 of forming the top coat layer 9, it is preferable to set the difference in angle between the direction of extension of the holes and the spraying direction of the thermal spray material, i.e., the application angle θa, to 0 degrees or more and 80 degrees or less when performing thermal spraying.

[0062] As a result of diligent research by the inventors, it was found that setting the application angle θa to 0 degrees or more and 80 degrees or less when thermal spraying is even more effective in preventing the holes 110 from being blocked by the material of the topcoat layer 9. Therefore, in the heat-shielding coating application methods according to some embodiments, by setting the application angle θa to 0 degrees or more and 80 degrees or less and performing thermal spraying, it is possible to effectively suppress the blockage of the holes 110 by the material of the topcoat layer.

[0063] In some embodiments of the heat-shielding coating application method, the diameter of the hole 110 is preferably greater than 0.5 mm (for example, 0.533 mm or more).

[0064] As a result of diligent research by the inventors, it was found that, as described later, in order to prevent the holes 110 from being blocked by the material of the topcoat layer 9, it is even better if the diameter of the holes 110 is greater than 0.5 mm (for example, 0.533 mm or more). Therefore, in the heat-shielding coating application methods according to some embodiments, by setting the diameter of the holes 110 to be larger than 0.5 mm (for example, 0.533 mm or more) and performing thermal spraying, it is possible to effectively suppress the blockage of the holes 110 by the material of the topcoat layer 9.

[0065] Figure 16 is a graph showing the experimental results regarding the relationship between the hole diameter (diameter) of hole 110 and the rate of blockage of hole 110 by the thermal spray material. The results shown in Figure 16 illustrate the degree of blockage of hole 110 when the inclination angle θb of hole 110 is 30 degrees and the construction angle θa is 60 degrees, depending on the thermal spraying method and whether or not gas (air) is ejected from hole 110. In the experiment shown in Figure 16, a bond coat layer 7 and a top coat layer 9 were sequentially formed on the surface of a heat-resistant alloy test piece corresponding to the heat-resistant alloy substrate 5 described above. In the experiment shown in Figure 16, the top coat layer 9 was formed by high-speed flame spraying using a suspension, with the target thickness set to be equivalent to the thickness in the actual machine.

[0066] The blockage rate on the vertical axis of the graph shown in Figure 16 is the percentage of the value obtained by dividing the pore diameter Da of the pore 110 after the formation of the topcoat layer 9 by the pore diameter Db of the pore 110 after the formation of the bond coat layer 7. Note that the pore diameter Db of the pore 110 after the formation of the bond coat layer 7 tends to be smaller than the pore diameter of the pore 110 before the formation of the bond coat layer 7 because a portion of the pore 110 is blocked by the thermal spray material of the bond coat layer 7. The pore diameter on the horizontal axis of the graph shown in Figure 16 represents the pore diameter of pore 110 before the formation of the bond coat layer 7.

[0067] As shown in Figure 16, when thermal spraying is performed without ejecting air from the hole 110, the blockage rate becomes 100% if the hole diameter of 110 is 0.5 mm or less. However, if the hole diameter of 110 is greater than 0.5 mm (for example, 0.533 mm or more), the blockage rate is less than approximately 50%. Furthermore, as shown in Figure 16, when thermal spraying is performed without ejecting air from the holes 110, the blockage rate is smaller when the topcoat layer 9 is formed by atmospheric pressure plasma spraying with a suspension than when the topcoat layer 9 is formed by atmospheric pressure plasma spraying with a suspension.

[0068] As shown in Figure 16, when the topcoat layer 9 is formed by atmospheric pressure plasma spraying with a suspension, and when the topcoat layer 9 is formed by high-velocity flame spraying with a suspension, the occlusion rate is smaller when spraying is performed while air is ejected from the holes 110 than when spraying is performed without ejecting air from the holes 110.

[0069] (Regarding the effects of regions where unmelted ceramic powder has aggregated) As described above, the inventors conducted thorough research and found that, in the process of forming a topcoat layer on a bond coat layer, by maintaining the temperature of the topcoat layer between 300°C and 450°C and spraying a suspension containing ceramic powder by high-velocity flame spraying, it is possible to ensure performance such as heat shielding and thermal cycle durability equivalent to that achieved when forming a topcoat layer on a bond coat layer by electron beam physical deposition. Furthermore, as a result of diligent research by the inventors, it was found that even when the suspension containing ceramic powder is sprayed by high-velocity flame spraying while maintaining the temperature of the topcoat layer 9 at 300°C to 450°C during step S20 for forming the topcoat layer 9, if there are areas in the topcoat layer 9 where unmelted ceramic powder has aggregated, these areas may become the starting point for delamination cracks and affect the thermal cycle durability. As a result of diligent research by the inventors, it was found that if the ratio of the area of ​​the area where unmelted ceramic powder has aggregated to the cross-sectional area of ​​the topcoat layer 9 is 0.15% or less, performance such as heat shielding and thermal cycle durability equivalent to that when the topcoat layer 9 is formed on the bond coat layer 7 by electron beam physical deposition can be ensured.

[0070] Therefore, in the heat-shielding coating application method according to several embodiments, in step S20 for forming the top coat layer 9, the temperature of the top coat layer 9 is maintained at 300°C to 450°C while a suspension containing ceramic powder is sprayed by high-speed flame spraying to form a top coat layer 9 in which the ratio of the area of ​​the region where unmelted ceramic powder has aggregated to the area of ​​the cross-sectional area of ​​the top coat layer 9 is 0.15% or less. The inventors' findings will be explained later.

[0071] This allows for the formation of the topcoat layer 9 on the bond coat layer 7 by electron beam physical deposition, resulting in lower running costs and a shorter timeframe. Furthermore, according to the heat-shielding coating application method of several embodiments, the cost of introducing equipment for forming the topcoat layer 9 can also be significantly reduced.

[0072] In the following explanation, the ratio of the area of ​​the region where unmelted ceramic powder has aggregated to the area of ​​the cross-section of the topcoat layer 9 is also referred to as the unmelted particle contamination rate. The unmelted particle contamination rate is the value obtained by dividing the area of ​​the region where unmelted ceramic powder has aggregated by the area of ​​the cross-section of the topcoat layer 9 and expressing it as a percentage. Specifically, the unmelted particle contamination rate is determined as follows. For example, a cross-section of the topcoat layer 9 is polished, and an image of the resulting surface is obtained using a scanning electron microscope (SEM). Then, the region where unmelted ceramic powder has aggregated within a predetermined area of ​​the obtained image is identified, and its area is determined. Finally, the unmelted particle content is calculated by dividing the determined area by the area of ​​the predetermined region.

[0073] Furthermore, the ceramic powder may contain one of the following, as described above: yttria-stabilized zirconia, dysprosia-stabilized zirconia, ervia-stabilized zirconia, Gd2Zr2O7, or Gd2Hf2O7. This results in a heat-shielding coating 3 with excellent heat-shielding properties.

[0074] In some embodiments of the method for applying a heat-shielding coating, in step S20 for forming the top coat layer 9, it is preferable to form a top coat layer 9 with an unmelted particle content of 0.02% or less by spraying a suspension containing ceramic powder by high-velocity flame spraying while maintaining the temperature of the top coat layer 9 at 300°C or higher and 450°C or lower. This further improves the performance of the heat-shielding coating 3, including its heat-shielding properties and thermal cycle durability.

[0075] (Regarding the zeta potential of ceramic powder in suspension) As mentioned above, the lower the temperature of the topcoat layer 9 during thermal spraying, the higher the peeling limit temperature difference ΔT of the topcoat layer 9 can be (see Figure 7). However, the lower the temperature of the topcoat layer 9 during thermal spraying, the more easily the aggregation state of the ceramic powder in the suspension is reflected in the structure of the topcoat layer 9, making it easier for unmelted particles to be incorporated into the topcoat layer 9. To facilitate the dispersion of ceramic powder in a suspension, it is desirable to increase the absolute value of the zeta potential of the ceramic powder in the suspension. As described later, after diligent research by the inventors, it was found that if the absolute value of the zeta potential of the ceramic powder in the suspension is 40 mV or higher, the ceramic powder in the suspension becomes less likely to aggregate, and as a result, the incorporation of unmelted particles into the top coat layer 9 can be suppressed.

[0076] Therefore, in the heat-shielding coating application method according to some embodiments, in step S20 for forming the top coat layer 9, it is preferable to spray a suspension in which the absolute value of the zeta potential of the ceramic powder in the suspension is 40 mV or more by high-speed flame spraying. This reduces the area where unmelted ceramic powder aggregates in the top coat layer 9, resulting in improved performance in the heat-shielding coating 3, such as heat shielding and thermal cycle durability.

[0077] (Regarding the pH of the suspension) As a result of diligent research by the inventors, it was found that when using ceramic powder to form the topcoat layer 9, if the pH of the suspension is 2 or less or 9 or more, the absolute value of the zeta potential of the ceramic powder in the suspension becomes 40 mV or more, making it difficult for the ceramic powder in the suspension to aggregate, and as a result, the incorporation of unmelted particles into the topcoat layer 9 can be suppressed. Therefore, in the application method of the heat-shielding coating according to some embodiments, in step S20 of forming the top coat layer 9, water or ethanol is used as the dispersion medium, and a suspension having a pH of 2 or less or 9 or more is sprayed by high-velocity flame spraying. This reduces the area where unmelted ceramic powder aggregates in the top coat layer 9, resulting in improved performance in the heat-shielding coating 3, such as heat shielding and thermal cycle durability.

[0078] As described above, in the heat-shielding coating application methods according to some embodiments, in step S20 for forming the top coat layer 9, it is preferable to form the top coat layer 9 by thermal spraying a suspension containing ceramic powder using high-velocity flame spraying while maintaining the temperature of the top coat layer 9 at 300°C or higher and 400°C or lower. This further improves the performance of the heat-shielding coating 3, including its heat-shielding properties and thermal cycle durability.

[0079] As described above, in the heat-shielding coating application methods according to some embodiments, it is preferable to control the temperature of the top coat layer 9 by cooling with a cooling medium CM in step S20, where the top coat layer 9 is formed. This makes it easier to control the temperature of the topcoat layer 9 within the aforementioned temperature range by cooling with the cooling medium CM, thereby stabilizing the performance of the heat-shielding coating 3, such as its heat shielding properties and thermal cycle durability.

[0080] As mentioned above, the cooling medium CM may be compressed air compressed by a compressor. The cooling medium CM may also contain dry ice.

[0081] The inventors' findings regarding the effects of regions where unmelted ceramic powder aggregates are described below. Figure 17 is a table showing the compositions of suspensions X and Y, which were used to investigate the effects of regions where unmelted ceramic powder aggregated. Figure 18A is a graph showing the particle size distribution of the solid components of suspension X. Figure 18B is a graph showing the particle size distribution of the solid components of suspension Y. Figure 19A is an SEM image of the solid components of suspension X. Figure 19B is an SEM image of the solid components of suspension Y. Figure 20 is a graph showing the relationship between the thermal spray temperature Ta and the peel limit temperature difference ΔT (relative value) for each test specimen. Figure 21 is a graph showing the relationship between the percentage of unmelted particles and the peeling limit temperature difference ΔT (relative value). Figure 22 is a graph showing the relationship between the pH of the suspension and the zeta potential of the ceramic powder in the suspension. Figure 23 is an SEM image of a specimen produced by suspension X. Figure 24 is an SEM image of a specimen produced by suspension Y.

[0082] In Figures 20 and 21, the peeling limit temperature difference ΔT of the topcoat layer 9 is expressed as a relative value with the peeling limit temperature difference ΔT of the topcoat layer formed by electron beam physical deposition set to 1. The peeling limit temperature difference ΔT in Figures 20 and 21 is the temperature difference at which peeling is estimated to occur in the heat-shielding coating 3 when this temperature difference ΔT is applied in a test that is repeated 1000 times.

[0083] As shown in Figure 17, there is no significant difference in the solid content composition between suspension X and suspension Y, but the dispersant components are different. It is presumed that this difference in dispersant components is the cause, as shown in Figures 18A and 18B, in which the particle size distribution of the solid components differs between suspension X and suspension Y. Specifically, the particle size distribution of the solid components in suspension Y has a lower peak and a wider distribution width compared to the particle size distribution of the solid components in suspension X, making it broader. As shown in Figures 19A and 19B, the solid components in suspension Y are more aggregated compared to the solid components in suspension X. The dispersion medium for suspensions X and Y is water. However, the dispersion medium for the suspensions may also be ethanol, or a mixed solution of water and ethanol.

[0084] In Figure 20, specimens A, B, C, F, and G, shown as solid black plots, were sprayed with suspension X, while specimen E, shown as a white plot, was sprayed with suspension Y. Note that specimens A, B, and C are the same specimens shown in Figures 6 through 10B. The thermal spray temperature Ta of test specimen A was 413°C as described above, and the thermal spray temperature Ta of test specimen E was 412°C. The thermal spray temperature Ta of test specimen F was 349°C, and the thermal spray temperature Ta of test specimen G was 268°C. The thermal spraying conditions for specimens E, F, and G, other than the thermal spraying temperature Ta, are the same as those described above for specimens A, B, C, and D (see Figure 9), other than the thermal spraying temperature Ta. The film thickness of test specimen A, i.e., the sum of the thickness of the bond coat layer 7 and the top coat layer 9, is 0.60 mm. The film thickness of test specimen B is 0.51 mm, and the film thickness of test specimen C is 0.54 mm. The film thickness of test specimen E is 0.49 mm, the film thickness of test specimen F is 0.59 mm, and the film thickness of test specimen G is 0.53 mm.

[0085] In some embodiments of the heat-shielding coating application method, it is desirable to form the topcoat layer 9 at a relatively low temperature by cooling with a cooling medium CM, as described above. However, a disadvantage of forming the topcoat layer 9 at a relatively low temperature is that the aggregation state of the suspension is easily reflected in the structure of the topcoat layer 9. Therefore, if the dispersion state of the suspension is not good, areas where unmelted ceramic powder aggregates will appear in the topcoat layer 9, and these areas will become the starting point for delamination cracks, thus adversely affecting the mechanical properties of the topcoat layer 9. As shown in Figure 21, the unmelted particle content in specimen A, which was sprayed with suspension X, was approximately 0%, while the unmelted particle content in specimen E, which was sprayed with suspension Y, was about 0.24%, which is higher than that of specimen A.

[0086] For example, in the SEM image of specimen A shown in Figure 23, no areas of aggregated unmelted ceramic powder are visible. In the SEM image of specimen E shown in Figure 24, areas where unmelted ceramic powder has aggregated are visible. These areas of aggregated unmelted ceramic powder are, for example, the areas enclosed by dashed lines in Figure 24. The SEM images in Figures 23 and 24 are at the same magnification, specifically 5000x magnification.

[0087] As shown in Figures 20 and 21, the peeling limit temperature difference ΔT of specimen E sprayed with suspension Y is significantly lower than that of specimen A sprayed with suspension X, which has approximately the same spraying temperature Ta. Considering this in conjunction with SEM images of the cross-sections of specimens A and E, and the particle size distribution of solid components in the suspension, it can be inferred that the dispersion state of solid components in the suspension has a significant influence on the peeling limit temperature difference ΔT.

[0088] As shown in Figure 21, by keeping the unmelted particle content at 0.02% or less, the peeling limit temperature difference ΔT of the topcoat layer 9 can be made equivalent to or greater than that when formed by electron beam physical deposition. Furthermore, the peeling limit temperature difference ΔT of the topcoat layer 9 may be approximately 0.8 as a relative value in Figure 21. Therefore, by keeping the unmelted particle content below 0.15%, the peeling limit temperature difference ΔT of the topcoat layer 9 can be set to a temperature difference greater than or equal to the required temperature difference. Therefore, the percentage of unmelted particles should ideally be 0.15% or less, and even better, 0.02% or less.

[0089] As shown in Figure 22, the zeta potential of the ceramic powder in suspension X is -40mV or less. Note that the zeta potential of the ceramic powder in suspension X was measured twice, so two plots of the zeta potential of the ceramic powder in suspension X are shown in Figure 22. The zeta potential of the ceramic powder in suspension Y is approximately 35 mV. The dispersion state of the suspension is affected by the absolute value of the zeta potential of the ceramic powder in the suspension. Therefore, the absolute value of the zeta potential of the ceramic powder in the suspension should be 40 mV or higher.

[0090] The zeta potential of ceramic powder in a suspension is affected by the pH of the suspension. Figure 22 shows that if the pH of the suspension is 2 or less, or 9 or more, the absolute value of the zeta potential of the ceramic powder in the suspension will be 40 mV or more. Therefore, the pH of the suspension should be either 2 or less, or 9 or more.

[0091] This disclosure is not limited to the embodiments described above, but also includes modified forms of the embodiments described above, as well as forms that combine these forms as appropriate.

[0092] The contents described in each of the above embodiments can be understood, for example, as follows: (1) A method for applying a heat-shielding coating according to at least one embodiment of the present disclosure comprises a step S20 of forming a top coat layer 9 on a bond coat layer 7 formed on a heat-resistant alloy substrate 5 of a heat-resistant member 1 which is the object to be coated. In the step S20 of forming the top coat layer 9, a suspension containing ceramic powder is sprayed by high-speed flame spraying while maintaining the temperature of the top coat layer 9 at 300°C or more and 450°C or less, thereby forming a top coat layer 9 in which the ratio of the area of ​​the region where unmelted ceramic powder has aggregated to the area of ​​the cross-sectional area of ​​the top coat layer 9 (unmelted particle content) is 0.15% or less.

[0093] According to the method described in (1) above, the topcoat layer 9 can be formed on the bond coat layer 7 by electron beam physical deposition at a lower running cost and in a shorter time. Furthermore, according to the method described in (1) above, the cost of introducing equipment for forming the topcoat layer 9 can be significantly reduced.

[0094] (2) In some embodiments, in the method of (1) above, in step S20 for forming the top coat layer 9, it is preferable to form a top coat layer 9 in which the ratio of the area of ​​the region where unmelted ceramic powder has aggregated to the area of ​​the cross-sectional area of ​​the top coat layer 9 (unmelted particle content) is 0.02% or less, by thermal spraying a suspension containing ceramic powder while maintaining the temperature of the top coat layer 9 at 300°C or more and 450°C or less.

[0095] According to the method described in (2) above, the performance of the heat-shielding coating 3, such as heat shielding properties and thermal cycle durability, is further improved.

[0096] (3) In some embodiments, in the step S20 of forming the top coat layer 9 in the method of (1) or (2) above, a suspension in which the absolute value of the zeta potential of the ceramic powder in the suspension is 40 mV or more is sprayed by high-velocity flame spraying.

[0097] According to the method described in (3) above, the area in the top coat layer 9 where unmelted ceramic powder aggregates can be reduced, resulting in improved performance in the heat-shielding coating 3, such as heat shielding and thermal cycle durability.

[0098] (4) In some embodiments, in step S20 of forming the top coat layer 9 in the method of (1) or (2) above, water or ethanol may be used as the dispersion medium, and a suspension having a pH of 2 or less or 9 or more may be sprayed by high-velocity flame spraying.

[0099] According to the method described in (4) above, the area in the top coat layer 9 where unmelted ceramic powder aggregates can be reduced, resulting in improved performance in the heat-shielding coating 3, such as heat shielding and thermal cycle durability.

[0100] (5) In some embodiments, in the step S20 of forming the top coat layer 9 in any of the methods (1) to (4) above, the top coat layer 9 may be formed by thermal spraying a suspension containing ceramic powder by high-velocity flame spraying while maintaining the temperature at 300°C or higher and 400°C or lower.

[0101] According to the method described in (5) above, the performance of the heat-shielding coating 3, such as heat shielding properties and thermal cycle durability, is further improved.

[0102] (6) In some embodiments, in any of the methods (1) to (5) above, the temperature may be controlled by cooling with a cooling medium CM in step S20 for forming the top coat layer 9.

[0103] According to the method in (6) above, the temperature can be easily controlled to the range described in (1) or (5) above by cooling with the cooling medium CM, thereby stabilizing the performance of the heat shielding coating 3, such as its heat shielding properties and thermal cycle durability.

[0104] (7) In some embodiments, in the method of (6) above, the cooling medium CM may be compressed air compressed by a compressor.

[0105] According to the method described in (7) above, securing the cooling medium CM is easy, and the increase in cooling costs can be suppressed.

[0106] (8) In some embodiments, the cooling medium CM in the method of (6) above may include dry ice.

[0107] According to the method described in (8) above, there is less risk of the temperature of the top coat layer 9 rising too high during its formation, and the performance of the heat-shielding coating 3, such as heat shielding and thermal cycle durability, is stabilized.

[0108] (9) In some embodiments, in any of the methods (1) to (8) above, the ceramic powder may contain any of yttria-stabilized zirconia, dysprosia-stabilized zirconia, ervia-stabilized zirconia, Gd2Zr2O7, or Gd2Hf2O7.

[0109] According to the method described in (9) above, a heat-shielding coating 3 with excellent heat-shielding properties can be obtained.

[0110] (10) A heat-resistant member 1 according to at least one embodiment of the present disclosure has a top coat layer 9 formed by a heat-shielding coating application method according to any of the methods (1) to (9) described above.

[0111] According to the configuration described in (10) above, the manufacturing cost of the heat-resistant component 1 can be reduced. [Explanation of symbols]

[0112] 1 Heat-resistant material 3. Heat-shielding coating 5 Heat-resistant alloy base material (base material) 7. Metallic bonding layer (bond coat layer) 9. Top coat layer

Claims

1. The process includes a step of forming a top coat layer on a bond coat layer formed on a heat-resistant alloy substrate of the object, In the process of forming the topcoat layer, the suspension containing ceramic powder is sprayed by high-velocity flame spraying while maintaining the temperature of the topcoat layer at 300°C to 450°C, thereby forming a topcoat layer in which the ratio of the area of ​​unmelted ceramic powder aggregated to the cross-sectional area of ​​the topcoat layer is 0.15% or less. Application method for heat-shielding coating.

2. In the process of forming the topcoat layer, the suspension containing ceramic powder is sprayed by high-velocity flame spraying while maintaining the temperature of the topcoat layer at 300°C to 450°C, thereby forming a topcoat layer in which the ratio of the area of ​​the region where unmelted ceramic powder has aggregated to the area of ​​the cross-sectional area of ​​the topcoat layer is 0.02% or less. A method for applying the heat-shielding coating described in claim 1.

3. In the step of forming the top coat layer, the suspension in which the absolute value of the zeta potential of the ceramic powder in the suspension is 40 mV or more is sprayed by high-velocity flame spraying. A method for applying a heat-shielding coating according to claim 1 or 2.

4. In the step of forming the top coat layer, water or ethanol is used as the dispersion medium, and the suspension having a pH of 2 or less or 9 or more is sprayed by high-velocity flame spraying. A method for applying a heat-shielding coating according to claim 1 or 2.

5. In the process of forming the topcoat layer, the topcoat layer is formed by thermal spraying a suspension containing ceramic powder using high-velocity flame spraying while maintaining the temperature at 300°C to 400°C. A method for applying a heat-shielding coating according to claim 1 or 2.

6. In the process of forming the top coat layer, the temperature is controlled by cooling with a cooling medium. A method for applying a heat-shielding coating according to claim 1 or 2.

7. The cooling medium is compressed air compressed by a compressor. A method for applying the heat-shielding coating described in claim 6.

8. The cooling medium includes dry ice. A method for applying the heat-shielding coating described in claim 6.

9. The ceramic powders mentioned above include yttria-stabilized zirconia, dyspuronia-stabilized zirconia, ervia-stabilized zirconia, and Gd ２ Zr ２ O ７ , or Gd ２ HF ２ O ７ Includes any of the following A method for applying a heat-shielding coating according to claim 1 or 2.

10. A step of forming a bond coat layer on a heat-resistant alloy substrate, The process of forming a top coat layer on the bond coat layer, A method for manufacturing a heat-resistant member comprising: In the process of forming the topcoat layer, the suspension containing ceramic powder is sprayed by high-velocity flame spraying while maintaining the temperature of the topcoat layer at 300°C to 450°C, thereby forming a topcoat layer in which the ratio of the area of ​​unmelted ceramic powder aggregated to the cross-sectional area of ​​the topcoat layer is 0.15% or less. A method for manufacturing heat-resistant components.

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