Repair spraying method for thermal barrier coating

Abstract

The repairing and spraying method comprises the steps that the surface area of the thermal barrier coating is divided into a repairing area, an outer ring area and an outer area, the repairing area is the area where the damaged part of the thermal barrier coating is located, the outer ring area is arranged around the repairing area, and the outer area is arranged around the outer ring area; shielding the external area by using a shielding material; the metal substrate in the repairing area is completely exposed through sand blasting treatment, and a slope of 30-60 degrees is formed in the outer ring area through sand blasting treatment; the shielding material is removed, and dry ice is used for cleaning the repairing area and the outer ring area; and spraying bonding raw material powder on a slope position, which is 4-6mm away from the edge of the repairing area, as an initial position, covering the repairing area and the outer ring area, stopping spraying the bonding raw material powder, switching to ceramic powder, and spraying the thickness of the repairing area and the outer ring area until the thickness of the repairing area and the thickness of the outer ring area are flush with the thickness of the periphery of the outer area.

Description

Technical Field

[0001] The invention relates to the field of thermal barrier coating repair of high-temperature metals, and in particular to a repair spraying method for thermal barrier coatings. Background Art

[0002] Heavy-duty gas turbines are core power equipment that uses high-temperature fuel gas as a working fluid. They are national strategic high-tech and a symbol of the level of major equipment manufacturing. They are related to national energy security, national defense security, and industrial competitiveness. Turbine blades are the key hot-end components that determine the output power of gas turbines and are crucial to the performance of the entire gas turbine. The combustion chamber and turbine components of heavy-duty gas turbines are larger than those of aircraft engines, and the coating area of ​​thermal barrier coatings is much larger than that of similar components of aircraft engines.

[0003] As the efficiency of gas turbines increases, the service temperature of turbine blades continues to increase. During the operation of gas turbines, they are subjected to the impact of high-temperature and high-pressure combustion gases exceeding 1400°C. This temperature far exceeds the temperature limit of the high-temperature alloy material used in the matrix (about 1000°C). Therefore, the turbine blades must be cooled, that is, a hollow belt cooling structure is used, and a thermal barrier coating is applied to the gas erosion surface. The combustion chamber must also use a high-temperature alloy as the outer shell and a thicker thermal barrier coating is applied inside to ensure that the transition section can operate safely and reliably at high temperatures.

[0004] The larger coating area leads to an extension of the spraying time from the normal spraying efficiency, the spraying equipment occasionally becomes unstable during long-term operation, and the coating may have poor local spraying quality during the preparation process.

[0005] When transporting, installing or transferring to other processes or factories, although coated products are required to be handled with care, the thermal barrier coating may still fall off due to bumps or squeezing. When the falling area is large, the product cannot be accepted. During operation, due to local short-term overheating, foreign objects (FOD) hitting the thermal barrier coating may also cause local peeling, which requires repair.

[0006] In general, the standard repair process requires the disassembly of the thermal barrier coating product, and then the use of mechanical methods such as sandblasting and water jet to completely remove the ceramic layer of the thermal barrier coating, the use of strong acid corrosion methods such as hydrochloric acid to completely remove the metal bonding layer, and the parts are restored to a coating-free state for re-spraying. This method is relatively safe, but the process route is long and the cost is high. The more mature approach to in-situ repair of a limited area is to repair a small area of ​​ceramic layer defects. It is necessary to use sandblasting to create a fresh section with appropriate roughness on the section of the ceramic coating, fully preheat it, and spray the ceramic surface layer according to the original process to restore the detached part. This method has certain limitations, including the inability to expose the bonding layer, because the sandblasting of the bonding layer will cause the metal dust that cannot be removed to be contaminated on the interface of the ceramic layer to be repaired, and the sandblasting surface made by sandblasting cannot guarantee the full removal of dust, organic matter, and oxides of the ceramic coating components, which will cause certain degradation of the performance of the coating after repair.

[0007] Patent document CN115961248A discloses a method for repairing thermal barrier coatings on single crystal blades, which uses automated sand blowing to remove the aluminized layer to obtain a single crystal blade with a clean surface; the surface of the single crystal blade with a clean surface is sequentially aluminized and diffused, and wet sand blowing is performed. After cleaning, the YSZ ceramic surface layer is coated using electron beam vapor deposition to complete the repair, but the contamination problem of the bonding layer or the ceramic layer during repair of a larger area is not solved.

[0008] Patent document CN106637031A discloses a thermal barrier coating application method, a thermal barrier coating repair method, a gas turbine component manufacturing method, and a shielding pin. The thermal barrier coating forming process includes forming a thermal barrier coating on the surface of the component body after the shielding pin insertion process; and a shielding pin removal process, after the thermal barrier coating forming process, removing the shielding pin by heat treatment, which does not solve the contamination problem of the bonding layer or ceramic layer when repairing a large area. The outer coating sandblasting stripping process, stripping the outer coating by sandblasting; the inner coating stripping process, after the outer coating sandblasting stripping process, stripping the inner coating by mechanical processing, which does not solve the contamination problem of the bonding layer or ceramic layer when repairing a large area. Summary of the invention

[0009] Based on the above technical problems, the present invention proposes a repair spraying method for thermal barrier coating to solve the pollution problem of bonding layer or ceramic layer when repairing a larger area.

[0010] To achieve the above object, the present invention provides a repair spraying method for thermal barrier coating.

[0011] A repair spraying method for a thermal barrier coating, comprising:

[0012] S1: dividing the surface area of ​​the thermal barrier coating into a repair area, an outer ring area and an external area, wherein the repair area is the area where the damaged part of the thermal barrier coating is located, the outer ring area is arranged around the repair area, and the external area is arranged around the outer ring area, and the external area is shielded by a shielding material;

[0013] S2: The metal substrate of the repaired area is completely exposed by sandblasting, and the outer ring area is formed into a slope of 30°-60° by sandblasting;

[0014] S3: removing the masking material and cleaning the repair area and the outer ring area using dry ice;

[0015] S4: Use bonding raw material powder to spray the slope position 4mm-6mm away from the edge of the repair area as the starting position, covering the repair area and the outer ring area, stop spraying the bonding raw material powder, switch to ceramic powder, and spray the thickness of the repair area and the outer ring area to be flush with the thickness of the surrounding area of ​​the outer area.

[0016] Furthermore, the step S1 includes:

[0017] The masking material includes Teflon tape, industrial masking tape, zirconium oxide coating or cubic boron nitride coating.

[0018] Furthermore, the step S1 includes:

[0019] The outer ring area is an area extending 5 mm to 20 mm outward from the edge of the repair area, and the external area is an area outside the repair area and the outer ring area.

[0020] Furthermore, the step S2 includes:

[0021] The sandblasting medium in the sandblasting process includes zirconium corundum, white corundum or zirconium oxide.

[0022] Furthermore, the step S2 includes:

[0023] The sandblasting pressure during the sandblasting process is 2 bar to 5 bar.

[0024] Furthermore, the step S2 includes:

[0025] The angle formed by the sandblasting equipment during the sandblasting process and the surface of the repair area is 70°-90°.

[0026] Furthermore, the step S2 includes:

[0027] The shape of the repair area includes a rectangle or a square.

[0028] Furthermore, the step S3 includes:

[0029] The particle size of dry ice used in the cleaning process is 5mm-10mm.

[0030] Furthermore, the step S3 further includes:

[0031] The repair area, the outer ring area and at least part of the external area are cleaned until all ceramic interfaces are observed to present a uniform original color, and the area of ​​the cleaned external area is 1 to 2 times the area of ​​the repair area.

[0032] Furthermore, before step S4, the following steps are included:

[0033] The repair area and the outer ring area are preheated using a plasma flame.

[0034] Furthermore, before step S4, the method further includes:

[0035] The repair area and the outer ring area are preheated to above 200° C. within 1 h to 2 h.

[0036] Furthermore, before step S4, the method further includes:

[0037] During the preheating process, the temperature measurement point is located at the slope position of the outer ring area.

[0038] Furthermore, the step S4 includes:

[0039] The bonding raw material powder comprises Co, Ni, Cr, Al and Y, and contains 31%-33% Ni, 20%-22% Cr, 7%-9% Al and 0.5%-1% Y by mass percentage, and the balance is Co and unavoidable impurities.

[0040] Furthermore, the step S4 includes:

[0041] During the spraying process using the bonding raw material powder, the number of spraying passes is 2 to 4 times.

[0042] Furthermore, the step S4 includes:

[0043] The ceramic powder comprises ZrO2 and Y2O3, wherein the mass percentage of Y2O3 is 7%-9%.

[0044] Furthermore, the step S4 includes:

[0045] The surfaces of the repaired area and the outer ring area after spraying are shaped by using a grinding and polishing tool.

[0046] Furthermore, the step S4 further includes:

[0047] The repaired area and the outer ring area after spraying are subjected to heat treatment at 600° C.-800° C.

[0048] Furthermore, the step S4 further includes:

[0049] The duration of the heat treatment is 30 min-120 min.

[0050] Based on the above technical solution, the present invention has at least the following beneficial effects:

[0051] 1. The present invention proposes a repair spraying method for thermal barrier coatings, which reduces the maintenance cost and pollution risk by spraying special bonding layer materials and sandblasting technology, while improving the safety of the maintenance process. This method can treat a large area of ​​damage at one time by reducing the need for rework of the entire part coating, thereby improving maintenance efficiency and reducing overall maintenance costs. By adopting special masking and cleaning techniques, the risk of pollution during the maintenance process is effectively reduced, ensuring the cleanliness of the maintenance area, thereby improving the safety of maintenance.

[0052] 2. The present invention proposes a repair spraying method for thermal barrier coating, which maintains the isothermal thermal cycle life of the original coating and improves the overall performance of the coating through process optimization. The use of Teflon tape, industrial masking tape, zirconium oxide coating or cubic boron nitride coating for masking, as well as large-particle dry ice cleaning, effectively prevents contamination of the repair area, reduces the problem of coating edge and shedding, thereby maintaining the durability and reliability of the coating. In addition, the coating after repair is visually uniform in color, further improving the aesthetics and consistency of the coating.

[0053] 3. The present invention proposes a thermal barrier coating repair spraying method, which achieves more efficient repair through a specific repair process, and is applicable to a variety of nickel-based high-temperature alloy materials and ceramic surface layers with different shedding conditions. The repaired workpiece can be further stress-released and contaminants removed through heat treatment, so that the coating performance is further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0055] Figure 1 A flow chart showing a method for spraying a thermal barrier coating according to an embodiment of the present invention is provided;

[0056] Figure 2A schematic diagram showing the division of regions of a thermal barrier coating according to an embodiment;

[0057] Figure 3 A schematic diagram showing a cross section of a thermal barrier coating after repair according to an embodiment;

[0058] Figure 4 A schematic diagram of a surface after repair by a thermal barrier coating according to an embodiment is shown. DETAILED DESCRIPTION

[0059] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0060] The present invention is further described in detail below in conjunction with specific embodiments, and these embodiments cannot be understood as limiting the scope of protection claimed by the present invention. The term "including" when used indicates the existence of a feature, but does not exclude the existence or addition of one or more other features; the orientation or position relationship indicated by the terms "lateral", "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention; in addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance.

[0061] In the description, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0062] Example

[0063] In order to solve the pollution problem of the bonding layer or the ceramic layer when repairing a larger area, the present invention provides a repair spraying method for a thermal barrier coating.

[0064] To achieve the above object, the present invention provides a repair spraying method for thermal barrier coating.

[0065] like Figure 1 A flow chart of a repair spraying method for a thermal barrier coating according to an embodiment of the present invention is shown in FIG. Figure 1 As shown, the process mainly includes the following steps:

[0066] S1, dividing the surface area of ​​the thermal barrier coating into a repair area, an outer ring area and an external area, wherein the repair area is the area where the damaged part of the thermal barrier coating is located, the outer ring area is arranged around the repair area, and the external area is arranged around the outer ring area, and the external area is shielded by a shielding material.

[0067] Furthermore, Figure 2 As shown, the damaged thermal barrier coating can be divided into areas using rectangles or squares, with the damaged exposed area divided inside as the repair area, and the area extending 10 mm outside the thermal barrier coating as the outer ring area. Preferably, zirconium oxide coating is used as a masking material to mask the outer ring area so that the repair area and the outer ring area are fully exposed.

[0068] In other embodiments, the area extending 5 mm outside the thermal barrier coating may be used as the outer ring area, or the area extending 20 mm outside the thermal barrier coating may be used as the outer ring area.

[0069] S2, completely exposing the metal substrate of the repaired area by sandblasting, and forming a slope of 30°-60° in the outer ring area by sandblasting.

[0070] Furthermore, during the sandblasting process, zirconium corundum, white corundum or zirconium oxide can be used as sandblasting media to sandblast the repair area and the outer ring area to remove the remaining thermal barrier coating and other contaminants in the rectangular or square area of ​​the repair area, exposing only the metal substrate of the high-temperature alloy. While sandblasting, the angle formed by the sandblasting equipment and the surface of the repair area is controlled so that the outer ring area forms a slope of 30°-60°. The highest point of the slope can be within the outer ring area or at the edge where the outer ring area borders the external area.

[0071] Preferably, the pressure of the sandblasting equipment is controlled to 3 bar, and the angle between the sandblasting equipment and the surface of the repair area is adjusted to 80°, forming a 45° slope starting from the edge of the repair area and gradually rising toward the outer area. The length of the slope mapped by the sandblasting equipment on the surface of the repair area is 10 mm, so that the highest point of the slope is inside the outer circle area.

[0072] In other embodiments, the sandblasting pressure can be controlled to 2 bar, the angle between the sandblasting equipment and the surface of the repair area is set to 70° and a slope of 60° is formed, or the sandblasting pressure can be controlled to 5 bar, the angle between the sandblasting equipment and the surface of the repair area is set to 90° and a slope of 30° is formed.

[0073] S3: removing the masking material, and cleaning the repair area and the outer ring area with dry ice.

[0074] Furthermore, dry ice particles with a particle size of 5 mm are used as a cleaning material to clean the repair area, the outer ring area, and the area within the external area that borders the outer ring area and is 1 times the area of ​​the repair area to remove impurities and pollution, so as to create a uniform original color on the cleaned ceramic interface within the outer ring area and the external area.

[0075] S4: Use bonding raw material powder to spray the slope position 4mm-6mm away from the edge of the repair area as the starting position, covering the repair area and the outer ring area, stop spraying the bonding raw material powder, switch to ceramic powder, and spray the thickness of the repair area and the outer ring area to be flush with the thickness of the surrounding area of ​​the outer area.

[0076] Furthermore, the repair area and the outer ring area after cleaning were preheated with a plasma flame. The surface of the metal substrate of the high-temperature alloy in the repair area was heated to 200°C within 1 hour. The bonding raw material powder was used to start spraying from the slope position of the outer ring area. After spraying twice, the powder feeding was stopped and the ceramic powder was used to continue spraying until the thickness of the repair area and the outer ring area was flush with the thickness of the outer area. At this time, the cross-sectional structure of the thermal barrier coating is as follows: Figure 3 As shown, the polishing tool is used to trim and smooth the sprayed surface. Figure 4 As shown, heat treatment is finally performed.

[0077] Preferably, the bonding raw material powder is composed of 32% Ni, 21% Cr, 8% Al, 0.5% Y, the remainder is Co and avoid impurities, and the ceramic powder is composed of ZrO2 and Y2O3, wherein the mass percentage of Y2O3 is 8%. After the thermal barrier coating repair spraying is completed, a heat treatment is carried out at 700 degrees Celsius for 80 minutes.

[0078] In other embodiments, the bonding raw material powder comprises 31% Ni, 20% Cr, 7% Al, 0.5% Y, and the remainder is Co and unavoidable impurities, and the ceramic powder comprises ZrO2 and Y2O3, wherein the mass percentage of Y2O3 is 7%, and after the thermal barrier coating repair spraying is completed, a heat treatment is performed at 600 degrees Celsius for 30 minutes. Alternatively, the bonding raw material powder comprises 33% Ni, 22% Cr, 9% Al, 1% Y, and the remainder is Co and unavoidable impurities, and the ceramic powder comprises ZrO2 and Y2O3, wherein the mass percentage of Y2O3 is 9%, and after the thermal barrier coating repair spraying is completed, a heat treatment is performed at 800 degrees Celsius for 120 minutes.

[0079] In summary, it can be seen from the above description that the above embodiments of the present invention achieve the following technical effects:

[0080] 1. The present invention proposes a repair spraying method for thermal barrier coatings, which reduces the maintenance cost and pollution risk by spraying special bonding layer materials and sandblasting technology, while improving the safety of the maintenance process. This method can treat a large area of ​​damage at one time by reducing the need for rework of the entire part coating, thereby improving maintenance efficiency and reducing overall maintenance costs. By adopting special masking and cleaning techniques, the risk of pollution during the maintenance process is effectively reduced, ensuring the cleanliness of the maintenance area, thereby improving the safety of maintenance.

[0081] 2. The present invention proposes a repair spraying method for thermal barrier coating, which maintains the isothermal thermal cycle life of the original coating and improves the overall performance of the coating through process optimization. The use of Teflon tape, industrial masking tape, zirconium oxide coating or cubic boron nitride coating for masking, as well as large-particle dry ice cleaning, effectively prevents contamination of the repair area, reduces the problem of coating edge and shedding, thereby maintaining the durability and reliability of the coating. In addition, the coating after repair is visually uniform in color, further improving the aesthetics and consistency of the coating.

[0082] 3. The present invention proposes a thermal barrier coating repair spraying method, which achieves more efficient repair through a specific repair process, and is applicable to a variety of nickel-based high-temperature alloy materials and ceramic surface layers with different shedding conditions. The repaired workpiece can be further stress-released and contaminants removed through heat treatment, so that the coating performance is further improved.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0084] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0085] It should be noted that, in the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

Claims

1. A method for repairing a thermal barrier coating by spraying, characterized in that: include: S1: dividing the surface area of ​​the thermal barrier coating into a repair area, an outer ring area and an external area, wherein the repair area is the area where the damaged part of the thermal barrier coating is located, the outer ring area is arranged around the repair area, and the external area is arranged around the outer ring area, and the external area is shielded by a shielding material; S2: The metal substrate of the repaired area is completely exposed by sandblasting, and the outer ring area is formed into a slope of 30°-60° by sandblasting; S3: removing the masking material and cleaning the repair area and the outer ring area using dry ice; S4: Use bonding raw material powder to spray the slope position of 4mm-6mm at the edge of the repair area as the starting position, covering the repair area and the outer ring area, stop spraying the bonding raw material powder, switch to ceramic powder, and spray the thickness of the repair area and the outer ring area to be flush with the thickness of the surrounding area of ​​the outer area.

2. The method according to claim 1, characterized in that: The step S1 includes: The masking material includes Teflon tape, industrial masking tape, zirconium oxide coating or cubic boron nitride coating.

3. The method according to claim 1, characterized in that: The step S1 includes: The outer ring area is an area extending 5 mm to 20 mm outward from the edge of the repair area, and the external area is an area outside the repair area and the outer ring area.

4. The method according to claim 1, characterized in that: The step S2 includes: The sandblasting medium in the sandblasting process includes zirconium corundum, white corundum or zirconium oxide.

5. The method according to claim 1, characterized in that: The step S2 includes: The blasting pressure during the blasting process is 2 bar to 5 bar.

6. The method according to claim 1, characterized in that: The step S2 includes: The angle formed by the sandblasting equipment during the sandblasting process and the surface of the repair area is 70°-90°.

7. The method according to claim 1, characterized in that: The step S2 includes: The shape of the repair area is rectangular or square.

8. The method according to claim 1, characterized in that: The step S3 includes: The particle size of dry ice used in the cleaning process is 5mm-10mm.

9. The method according to claim 1, characterized in that: The step S3 further includes: The repair area, the outer ring area and at least part of the external area are cleaned until all ceramic interfaces are observed to present a uniform original color, and the area of ​​the cleaned external area is 1 to 2 times the area of ​​the repair area.

10. The method according to claim 1, characterized in that: Before step S4, the method includes: The repair area and the outer ring area are preheated using a plasma flame.

11. The method according to claim 10, characterized in that: Before step S4, the method further includes: The repair area and the outer ring area are preheated to above 200° C. within 1 h to 2 h.

12. The method according to claim 10, characterized in that: Before step S4, the method further includes: During the preheating process, the temperature measurement point is located at the slope position of the outer ring area.

13. The method according to claim 1, characterized in that: The step S4 includes: The bonding raw material powder comprises Co, Ni, Cr, Al and Y, and contains 31%-33% Ni, 20%-22% Cr, 7%-9% Al and 0.5%-1% Y by mass percentage, and the balance is Co and unavoidable impurities.

14. The method according to claim 1, characterized in that: The step S4 includes: During the spraying process using the bonding raw material powder, the number of spraying passes is 2 to 4 times.

15. The method according to claim 1, characterized in that: The step S4 includes: The ceramic powder comprises ZrO2 and Y2O3, wherein the mass percentage of Y2O3 is 7%-9%.

16. The method according to claim 1, characterized in that: The step S4 includes: The surfaces of the repaired area and the outer ring area after spraying are shaped by using a grinding and polishing tool.

17. The method according to claim 1, characterized in that: The step S4 further includes: The repaired area and the outer ring area after spraying are subjected to heat treatment at 600° C.-800° C.

18. The method according to claim 17, characterized in that: The step S4 further includes: The duration of the heat treatment is 30 min-120 min.

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