Methods and materials for repairing thermal barrier coatings of gas turbine engine components

Abstract

A sprayable thermal barrier coating powder mixture for a gas turbine engine comprising: a dry composition comprising a low surface area ceramic powder having a median particle size distribution greater than 5 microns and less than 50 microns and a high surface area ceramic powder having a median particle size distribution less than 5 microns, the low surface area ceramic powder comprises at least 50 wt% of the dry composition of the sprayable thermal barrier coating powder mixture.

Description

This application is a divisional application of an invention patent application with an application date of June 18, 2021, application number 202110680836.0, and name being Methods and Materials for Repairing Thermal Barrier Coatings of Gas Turbine Engine Components. Priority information

[0001] This application claims priority to Indian application No. 202011025995 filed on June 19, 2020. Technical Field

[0002] The present invention relates generally to methods and materials for repairing thermal barrier coatings on engine components, and more particularly to powder mixtures and methods of applying such powder mixtures in situ. Background Art

[0003] The use of thermal barrier coatings (TBCs) on components such as combustors, high pressure turbine (HPT) blades, vanes, and shrouds helps these components withstand higher operating temperatures, increases component durability, and improves engine reliability. TBCs are typically formed from ceramic materials and deposited on an environmentally friendly bond coat to form a so-called TBC system.

[0004] Under operating conditions, hot section engine components protected by the TBC system can be susceptible to various forms of damage, including corrosion, oxidation and erosion from exposure to combustion gas products, foreign object damage (FOD), and attack from environmental contaminants. The source of environmental contaminants is the ambient air, which is ingested by the engine for cooling and combustion. The types of environmental contaminants in the ambient air vary from location to location, but can be a concern for aircraft because of their purpose of moving from one location to another. These environmental contaminants are in addition to the corrosive and oxidizing contaminants generated by the combustion of the fuel. However, all of these contaminants can adhere to the surfaces of hot section components, including those components protected by the TBC system.

[0005] Some of these contaminants may cause the TBC to be lost during the life of the component, leaving a portion of the TBC thin, or completely removing a portion of the TBC, exposing the underlying component to operating conditions and potentially damaging the component. If such damage occurs, it is typically necessary to repair it. Systems and / or methods for repairing such TBCs would be useful. Summary of the invention

[0006] Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

[0007] One aspect of the present disclosure relates to a sprayable thermal barrier coating powder mixture for a gas turbine engine. The sprayable thermal barrier coating powder mixture includes: a dry composition having a low surface area ceramic powder having a median particle size distribution greater than 5 microns and less than 50 microns and a high surface area ceramic powder having a median particle size distribution less than 5 microns, wherein the low surface area ceramic powder accounts for at least 50 wt% of the dry composition of the sprayable thermal barrier coating powder mixture.

[0008] These and other features, aspects and advantages of the present invention will be better understood with reference to the following description and appended claims.The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] A full and enabling disclosure of the present invention, including the best mode thereof, to one of ordinary skill in the art is set forth in the specification with reference to the accompanying drawings, in which:

[0010] Figure 1 is a schematic cross-sectional view of an exemplary gas turbine engine according to various embodiments of the present invention;

[0011] Figure 2 is a perspective cross-sectional view of a combustor assembly with a damaged TBC according to an exemplary embodiment of the present disclosure;

[0012] Figure 3 is a schematic diagram of a system for in-situ repair of a portion of a thermal barrier coating of a component according to an exemplary embodiment of the present disclosure;

[0013] Figure 4 can be used according to an exemplary embodiment of the present disclosure Figure 3 A close-up schematic diagram of a sprayable thermal barrier coating powder mixture of an exemplary system;

[0014] Figure 5 showing a close-up cross-sectional view of a repaired coating applied to an underlying component surface;

[0015] Figure 6 Shows Figure 5 A close-up view of a portion of the repaired coating;

[0016] Figure 7 is a flow chart of a method for in-situ repair of a thermal barrier coating of a gas turbine engine component according to an exemplary aspect of the present disclosure.

[0017] Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention. DETAILED DESCRIPTION

[0018] Reference will now be made in detail to embodiments of the present invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar reference numerals in the drawings and description have been used to refer to like or similar parts of the present invention.

[0019] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as advantageous over other implementations.

[0020] As used herein, the terms “first,” “second,” and “third” are used interchangeably to distinguish one component from another, and are not intended to indicate the position or importance of each component.

[0021] The terms "front" and "rear" refer to relative positions within a gas turbine engine or vehicle and refer to the normal operating attitude of the gas turbine engine or vehicle. For example, for a gas turbine engine, front refers to a position near the engine inlet, while rear refers to a position near the engine nozzle or exhaust.

[0022] The terms "upstream" and "downstream" refer to relative directions relative to the flow of fluid in a fluid passage. For example, "upstream" refers to the direction from which the fluid is flowing, and "downstream" refers to the direction to which the fluid is flowing.

[0023] Unless otherwise stated, the terms "coupled," "fixed," "connected," and the like refer to both direct coupling, fixing, or connection as well as indirect coupling, fixing, or connection through one or more intermediate components or features.

[0024] Unless the context clearly indicates otherwise, each term in the singular includes the plural.

[0025] Approximate descriptions used herein throughout the specification and claims are applicable to modify any quantitative description that allows for variations that do not result in a change in the basic function to which it is related. Therefore, values ​​modified by one or more terms such as "about," "approximately," and "substantially" are not limited to the precise values ​​specified. In at least some cases, an approximate description may correspond to the precision of an instrument used to measure the value, or the precision of a method or machine used to construct or manufacture a component and / or system. For example, an approximate description may mean within a range of 10%.

[0026] Here and throughout the specification and claims, range definitions are combined and interchanged, and unless the context dictates otherwise, such ranges are deemed to include all sub-ranges contained therein. For example, all ranges disclosed herein include the endpoints, and the endpoints are independently combinable with each other.

[0027] As will be appreciated, thermal barrier coatings ("TBCs") may become damaged or degraded throughout their life due to, for example, contaminants, leaving thin portions of the TBC, or completely removing a portion of the TBC exposing underlying components to operating conditions and potentially damaging such components. To repair these areas of the TBC, it is typically necessary to take the engine "off wing" (i.e., remove the engine from the aircraft), remove the components (or disassemble the engine to the extent that the components are exposed), clean the area to be repaired, apply the TBC patch, cure the TBC patch, and then reassemble and reinstall the engine. This is a fairly time-consuming and expensive process.

[0028] Therefore, it should be appreciated that it would be desirable if systems and methods could be used to repair TBCs without requiring the engine to be taken off-board and at least partially disassembled. In one aspect of the present disclosure, a sprayable thermal barrier coating powder mixture for a gas turbine engine is provided that can be applied in situ without the need to separately cure the component and the newly applied thermal barrier coating powder mixture outside the engine. In certain aspects, the sprayable thermal barrier coating powder mixture may include: a dry composition having a low surface area ceramic powder having a median particle size distribution greater than 5 microns and less than 50 microns and a high surface area ceramic powder having a median particle size distribution less than 5 microns, wherein the low surface area ceramic powder accounts for at least 50% of the dry composition weight of the sprayable thermal barrier coating powder mixture.

[0029] For example, in certain exemplary aspects, such a configuration can allow the activation temperature of the mixture to be limited to a range of about 300° C. to about 1200° C., so that the thermal barrier coating mixture can be cured by running the gas turbine engine. This can allow for a faster and cheaper repair process because the thermal barrier coating powder mixture can be applied and cured without having to take the engine off-line.

[0030] Now referring to the accompanying drawings, Figure 1 is a schematic cross-sectional view of a gas turbine engine according to an exemplary embodiment of the present disclosure. More specifically, Figure 1 In an embodiment of the present invention, the gas turbine engine is a high bypass turbofan jet engine 10, referred to herein as a "turbofan engine 10". Figure 1 As shown, the turbofan engine 10 defines an axial direction A (parallel to and extending from a longitudinal centerline 12 provided for reference) and a radial direction R. Generally, the turbofan 10 includes a fan section 14 and a core turbine engine 16 disposed downstream of the fan section 14 .

[0031] The illustrated exemplary core turbine engine 16 generally includes a substantially tubular casing 18 defining an annular inlet 20. The casing 18 encloses in series flow relationship a compressor section including a supercharger or low pressure (LP) compressor 22 and a high pressure (HP) compressor 24, a combustion section 26, a turbine section including a high pressure (HP) turbine 28 and a low pressure (LP) turbine 30, and an ejection exhaust nozzle section 32. A high pressure (HP) shaft or spool 34 drivingly connects the HP turbine 28 to the HP compressor 24. A low pressure (LP) shaft or spool 36 drivingly connects the LP turbine 30 to the LP compressor 22.

[0032] For the illustrated embodiment, the fan section 14 includes a variable pitch fan 38 having a plurality of fan blades 40 connected to a disk 42 in a spaced-apart manner. As shown, the fan blades 40 extend outwardly from the disk 42 generally in a radial direction R. Since the fan blades 40 are operably connected to a suitable actuating member 44, each fan blade 40 can rotate relative to the disk 42 about a pitch axis P, and the actuating member 44 is configured to uniformly change the pitch of all fan blades 40. The fan blades 40, the disk 42, and the actuating member 44 rotate together about the longitudinal axis 12 through the LP shaft 36, passing through an optional power gearbox 46. The power gearbox 46 includes a plurality of gears for gradually reducing the rotation speed of the LP shaft 36 to make the fan speed more efficient.

[0033] Still reference Figure 1 An exemplary embodiment of Figure 1 , the disk 42 is covered by a rotatable forward nacelle 48, the aerodynamic profile of the forward nacelle 48 facilitating airflow through the plurality of fan blades 40. In addition, the exemplary fan section 14 includes an annular fan cover or outer nacelle 50 that circumferentially surrounds the fan 38 and / or at least a portion of the core turbine engine 16. It should be appreciated that the outer nacelle 50 can be configured to be supported relative to the core turbine engine 16 by a plurality of circumferentially spaced outlet guide vanes 52. In addition, a downstream portion 54 of the outer nacelle 50 extends above the exterior of the core turbine engine 16, thereby defining a bypass airflow passage 56 therebetween.

[0034] During operation of the turbofan engine 10, a volume of air 58 enters the turbofan 10 through the outer nacelle 50 and / or the associated inlet 60 of the fan section 14. As the volume of air 58 passes through the fan blades 40, a first portion of the air 58, indicated by arrow 62, is directed or directed to the bypass airflow passage 56, and a second portion of the air 58, as indicated by arrow 64, is directed or directed to the LP compressor 22. The ratio between the first portion of air 62 and the second portion of air 64 is generally referred to as the bypass ratio. As the second portion of air 64 is directed through the high pressure (HP) compressor 24 and into the combustion section 26, the pressure of the second portion of air 64 increases, where the second portion of air 64 is mixed with fuel and combusted to provide combustion gases 66.

[0035] The combustion gases 66 are directed through the HP turbine 28 where a portion of the thermal and / or kinetic energy from the combustion gases 66 is extracted by sequentially segmented HP turbine stator blades 68 connected to the casing 18 and HP turbine rotor blades 70 connected to the HP shaft or spool 34, thereby causing the HP shaft or spool 34 to rotate, thereby supporting operation of the HP compressor 24. The combustion gases 66 are then directed through the LP turbine 30 where a second portion of the thermal and kinetic energy is extracted from the combustion gases 66 by sequentially segmented LP turbine stator blades 72 connected to the casing 18 and LP turbine rotor blades 74 connected to the LP shaft or spool 36, thereby causing the LP shaft or spool 36 to rotate, thereby supporting operation of the LP compressor 22 and / or rotation of the fan 38.

[0036] The combustion gases 66 are then directed through the jet exhaust nozzle section 32 of the core turbine engine 16 to provide propulsive thrust. At the same time, the pressure of the first portion of air 62 is significantly increased as the first portion of air 62 is directed through the bypass airflow passage 56 before it is discharged from the fan nozzle exhaust section 76 of the turbofan 10, also providing propulsive thrust. The HP turbine 28, the LP turbine 30, and the jet exhaust nozzle section 32 at least partially define a hot gas path 78 for directing the combustion gases 66 through the core turbine engine 16.

[0037] Reference now Figure 2 , provides Figure 1 More specifically, according to an exemplary embodiment of the present disclosure, Figure 2 A perspective cross-sectional view of a burner assembly 100 is provided, which may be located in a Figure 1 The combustion section 26 of the exemplary turbofan engine 10 is shown in FIG.

[0038] As shown, the combustor assembly 100 generally includes an inner liner 102 extending generally in an axial direction A between an aft end 104 and a forward end 106, and an outer liner 108 also extending generally in an axial direction A between an aft end 110 and a forward end 112. The inner liner 102 and the outer liner 108 together at least partially define a combustion chamber 114 therebetween. The inner liner 102 and the outer liner 108 are each connected to an annular dome. More specifically, the combustor assembly 100 includes an inner annular dome 116 connected to the forward end 106 of the inner liner 102 and an outer annular dome 118 connected to the forward end 112 of the outer liner 108. Although the inner annular dome 116 and the outer annular dome 118 are shown to each include a closed surface that defines a slot 122 for receiving the respective forward ends 106, 112 of the inner liner 102 and the outer liner 108, any suitable connection scheme may be used to connect the liners to the respective domes. Furthermore, while the exemplary combustor assembly 100 is shown as including an inner annular dome and an outer annular dome, it should be appreciated that in other embodiments the domes may be formed as a single dome configuration or any other suitable multi-dome configuration (eg, 3 domes, etc.).

[0039] The combustor assembly 100 also includes a plurality of fuel-air mixers 124 spaced circumferentially within the outer dome 118. More specifically, the plurality of fuel-air mixers 124 are disposed radially R between the outer dome 118 and the inner dome 116. Compressed air from the compressor section of the turbofan engine 10 flows into or through the fuel-air mixers 124, where the compressed air is mixed with fuel and ignited to produce combustion gases 66 within the combustion chamber 114. The inner dome 116 and the outer dome 118 are configured to assist in providing such compressed air flow from the compressor section into or through the fuel-air mixers 126. For example, the outer dome 118 includes an outer shroud 126 at a forward end 128, and the inner dome 116 similarly includes an inner shroud 130 at a forward end 132. The outer shroud 126 and the inner shroud 130 may assist in directing the compressed air flow 26 from the compressor section into or through one or more fuel-air mixers.

[0040] In addition, both the inner dome 116 and the outer dome 118 include a connection portion configured to assist in mounting the combustor assembly 100 within the turbofan engine 10. For example, the outer dome 118 includes a connection extension 134 configured to be mounted to an outer combustor casing (not shown), and the inner dome 116 includes a similar connection extension 138 configured to be connected to an annular support member (not shown) inside the turbofan engine 10. In certain exemplary embodiments, the inner dome 116 can be integrally formed as a single annular component, and similarly, the outer dome 118 can also be integrally formed as a single annular component. However, it should be understood that in other exemplary embodiments, the inner dome 116 and / or the outer dome 118 can alternatively be formed by more than one component joined in any suitable manner. For example, with reference to the outer dome 118, in certain exemplary embodiments, the outer cover 126 can be formed separately from the outer dome 118 and connected to the front end 128 of the outer dome 118 using, for example, a welding process. Similarly, the connecting extension 134 may also be formed separately from the outer dome 118 and connected to the front end 128 of the outer dome 118 using, for example, a welding process. Additionally or alternatively, the inner dome 116 may also have a similar configuration.

[0041] Still reference Figure 2 The exemplary combustor assembly 100 also includes a plurality of heat shields 142 positioned and arranged circumferentially around each fuel-air mixer 124. For the depicted embodiment, the heat shields 142 are connected to and extend between the outer dome 118 and the inner dome 116. The heat shields 142 are configured to protect certain components of the turbofan engine 10 from the relatively extreme temperatures of the combustion chamber 114.

[0042] It should be understood that during operation of the gas turbine engine, both the inner liner 102 and the outer liner 104 of the heat shield 142 are exposed to relatively harsh conditions of relatively high temperatures. Therefore, a thermal barrier coating 146 is present on at least one or more exposed surfaces of these components.

[0043] Especially for Figure 2 In an embodiment of the present invention, the heat shield 142 includes a thermal barrier coating 146 for protecting the underlying structure of the heat shield 142. The thermal barrier coating 146 may be a ceramic coating or any other suitable coating.

[0044] In one or more embodiments, the thermal barrier coating 146 may generally include a ceramic thermal barrier material. For example, suitable ceramic thermal barrier coating materials may include various types of oxides, such as aluminum oxide ("alumina"), hafnium oxide ("hafnia"), or zirconium oxide ("zirconia"), particularly stabilized hafnia or stabilized zirconia, and mixtures including one or both thereof. Examples of stabilized zirconia include, but are not limited to, yttria-stabilized zirconia, cerium-stabilized zirconia, calcium-stabilized zirconia, scandium-stabilized zirconia, magnesium-stabilized zirconia, indium-stabilized zirconia, ytterbium-stabilized zirconia, lanthanum-stabilized zirconia, gadolinium-stabilized zirconia, and mixtures of such stabilized zirconias. Similar stabilized hafnia compositions are known in the art and are suitable for use in the embodiments described herein.

[0045] In certain embodiments, the thermal barrier coating 146 may include yttria-stabilized zirconia. Suitable yttria-stabilized zirconia may include about 1 wt% to about 20 wt% yttria (based on the combined weight of yttria and zirconia), and more typically include about 3 wt% to about 10 wt% yttria. Examples of yttria-stabilized zirconia thermal barrier coatings include about 7% yttria and about 93% zirconia. These types of zirconia may also include one or more second metal (e.g., lanthanides, actinides, etc.) oxides, such as dysprosium oxide, erbium oxide, europium oxide, gadolinium oxide, neodymium oxide, praseodymium oxide, uranium oxide, and hafnium oxide, to further reduce the thermal conductivity of the thermal barrier coating material. In more than one embodiment, the thermal barrier coating material may also include additional metal oxides, such as titanium oxide and / or aluminum oxide. For example, the thermal barrier coating 146 may be composed of 8YSZ, but higher yttria concentrations may also be used.

[0046] Suitable ceramic thermal barrier coating materials may also include pyrochlores of the general formula A2B2O7, where A is a metal with a valence state of 3+ or 2+ (e.g., gadolinium, aluminum, cerium, lanthanum, or yttrium), and B is a metal with a valence state of 4+ or 5+ (e.g., hafnium, titanium, cerium, or zirconium), where the sum of the valences of A and B is 7. Representative materials of this type include gadolinium zirconate, lanthanum titanate, lanthanum zirconate, yttrium zirconate, lanthanum hafnate, cerium hafnate, and lanthanum cerate.

[0047] The thickness of the thermal barrier coating 146 may depend on the substrate or component on which it is deposited. In some embodiments, the thickness of the coating 146 is in the range of about 25 micrometers (μm) to about 2000 μm. In some embodiments, the thickness of the coating 146 is in the range of about 25 μm to about 1500 μm. In some embodiments, the thickness is in the range of about 25 μm to about 1000 μm.

[0048] Furthermore, it will be appreciated that, through operation of the gas turbine engine 10, one or more portions of the thermal barrier coating 146 may wear or degrade faster than other portions of the thermal barrier coating 146. Figure 2 As schematically shown, the thermal barrier coating 146 includes a worn portion 148 between adjacent fuel air mixers 124 .

[0049] Reference now Figure 3 , schematically illustrates a system 200 for repairing a worn portion 148 of a thermal barrier coating 146. The illustrated exemplary system 200 generally includes a nozzle 202, a mixture line 204, and a pressurized gas line 206. The mixture line 204 can provide a sprayable thermal barrier coating powder mixture 208 to the nozzle 202, and the pressurized gas line 206 can provide a pressurized gas (e.g., a pressurized air flow). The nozzle 202 can mix the flow of the sprayable thermal barrier coating powder mixture 208 with the flow of the pressurized gas to atomize the flow of the sprayable thermal barrier coating powder mixture 208 and apply this thermal barrier coating powder mixture 208 to the worn portion 148 of the thermal barrier coating 146.

[0050] For the illustrated embodiment, the sprayable thermal barrier coating powder mixture 208 is configured to be applied directly to the worn portion 148 of the thermal barrier coating 146, the exposed portion of the underlying component, or both. More specifically, for the illustrated embodiment, the sprayable thermal barrier coating powder mixture 208 is configured to be applied directly to the worn portion 148 of the thermal barrier coating 146, the exposed portion of the underlying component, or both without any intervening cleaning steps. In this manner, the sprayable thermal barrier coating powder mixture 208 can be used to form the patch 150 to cover or fill the worn portion 148 of the thermal barrier coating 146.

[0051] Thus, it should be appreciated that the process may require minimal disassembly of the gas turbine engine component in order to perform the coating repair process, and the coating may be applied to the surface without requiring any special degreasing, cleaning, or oxide removal that is typically required for "in-shop" type repairs. Furthermore, it will be appreciated from the following description that the coating chemistry and spraying process may be designed to restore the coating with an oxidized surface. This may eliminate the need for any kind of fast bond coating process that may be performed for "in-shop" type repair applications.

[0052] In addition, for the illustrated environment, the thermal barrier coating powder mixture 208 and the system 200 for applying the same are configured to form a coating having a thickness 210 greater than 2 mils (i.e., one thousandth of an inch), such as greater than 4 mils, such as greater than 6 mils, such as greater than 10 mils, such as greater than 15 mils, such as up to about 45 mils, such as up to about 35 mils, such as up to about 25 mils. In this manner, the thermal barrier coating powder mixture 208 can form a repaired portion of the thermal barrier coating 146. As used herein, with reference to a repaired portion of the thermal barrier coating 146, the thickness 210 refers to the maximum thickness of the repaired portion, or more specifically, the maximum thickness of the patch 150.

[0053] Now refer to Figure 4 , provides a close-up view of a sprayable thermal barrier coating powder mixture 208, which may be used in conjunction with the above reference Figure 3 However, it should be understood that in other embodiments, the sprayable thermal barrier coating powder mixture 208 may alternatively be used with any other suitable system 200 capable of spraying the powder mixture 208 in situ onto a component of a gas turbine engine (e.g., a turbofan engine 10) (or onto any other suitable gas turbine engine). For example, although the above reference Figure 3 The exemplary system 200 is shown applying a sprayable thermal barrier coating powder mixture 208 to a thermal barrier coating 146 of a heat shield 142 within a combustion section 26 of a gas turbine engine 10. In other exemplary embodiments, Figure 4 The sprayable thermal barrier coating powder mixture 208 shown in and described below may be applied to or otherwise used to repair the thermal barrier coating 146 on one or more combustion chamber liners, one or more turbine rotor blades, one or more turbine stator blades, etc. Moreover, in other exemplary embodiments, the system 200 for applying such a sprayable thermal barrier coating powder mixture 208 may include any other suitable technique for providing the sprayable thermal barrier coating powder mixture 208 to the worn portion 148 of the thermal barrier coating 146.

[0054] like Figure 4 As shown, the sprayable thermal barrier coating powder mixture 208 generally includes a dry composition having a low surface area ceramic powder 214 and a high surface area ceramic powder 216. As used herein, the term low surface area ceramic powder 214 refers to a ceramic powder having a surface area of ​​10 square meters / gram or less, such as a surface area of ​​8 square meters / gram or less, such as a surface area of ​​5 square meters / gram or less. In addition, as used herein, the term high surface area ceramic powder 216 refers to a ceramic powder having a surface area greater than 10 square meters / gram, such as a surface area of ​​15 square meters / gram or more, and a surface area of ​​up to 400 square meters / gram, such as a surface area of ​​up to 4000 square meters / gram.

[0055] It should also be understood that, as used herein, the term "ceramic powder" refers to a powder comprising one or more refractory oxides, such as one or more of aluminum oxide, zirconium oxide, hafnium oxide, magnesium oxide, silicon oxide, yttrium oxide, and combinations thereof.

[0056] In certain exemplary embodiments, the low surface area ceramic powder 214 and the high surface area ceramic powder 216 may be formed from materials having substantially the same chemistry as the chemistry of the thermal barrier coating 146 to be applied. Figure 3 When used with the exemplary system 200 of FIG. 1 , the low surface area ceramic powder 214 and the high surface area ceramic powder 216 of the sprayable thermal barrier coating powder mixture 208 used may have substantially the same chemistry as the thermal barrier coating 146 being repaired. For example, the powders 214, 216 and the thermal barrier coating 216 may each include at least 50 wt% of a common material or component.

[0057] Alternatively, however, in other embodiments, the low surface area ceramic powder 214, the high surface area ceramic powder 216, or both may have different suitable chemistries.

[0058] In certain exemplary embodiments, the low surface area ceramic powder 214 may have a median particle size distribution greater than 5 microns and less than 50 microns, and the high surface area ceramic powder 216 may have a median particle size distribution less than 5 microns. For example, the low surface area ceramic powder 214 may have a median particle size distribution greater than 8 microns and less than 40 microns, and the high surface area ceramic powder 216 may have a median particle size distribution less than 4 microns, such as less than 3 microns, such as at least 0.1 microns.

[0059] It should be appreciated that the high surface area ceramic powder 216 can act as a binder to hold the powder mixture 208 together. Additionally, the low surface area ceramic powder 214 can act as a filler. When a thicker thermal barrier coating 146 is to be applied, more low surface area ceramic powder 214 can generally be used, whereas when a thinner thermal barrier coating 146 is to be applied, less low surface area ceramic powder 214 can generally be used.

[0060] As will be further appreciated, in certain exemplary aspects, the sprayable thermal barrier coating powder mixture 208 may be configured to be sprayed onto the portion of the thermal barrier coating 146 and / or component to be repaired in situ and cured by exposure to operating temperatures within the gas turbine engine 10. In this manner, the engine 10 may not need to be "off-machine" and at least partially disassembled to allow the repaired component to be placed into a separate machine to cure the thermal barrier coating patch 150 applied thereto. To facilitate this configuration, the sprayable thermal barrier coating powder mixture 208 may include more than one portion that acts as a binder to hold the powder mixture 208 together over a relatively wide temperature range (referred to herein as the "activation temperature range" of the sprayable thermal barrier coating powder mixture 208, which will be described in detail below).

[0061] For example, in certain exemplary embodiments, the sprayable thermal barrier coating powder mixture 208 may also include at least one binder additive 218 (in Figure 4 214). At least one binder additive 218 may be an organic binder additive. For example, the organic binder additive may be one or more of the following: a film-forming polymer binder such as polyvinyl alcohol, polyethylene oxide, polyethylene glycol, polyvinyl pyrrolidone (PVP), acrylates, acrylamides, and copolymers.

[0062] The organic binder additive that may be used as a binder for the sprayable thermal barrier coating powder mixture 208 may be added at a temperature below 500°C, such as between 100°C and 500°C.

[0063] In further exemplary embodiments, at least one binder additive 218 may also or alternatively be an inorganic binder additive. For example, the inorganic binder additive may be one or more high surface area (>10 m 2 / g) of high temperature resistant oxide, such as one or more of aluminum oxide, zirconium oxide, hafnium oxide, silicon oxide and yttrium oxide.

[0064] Inorganic binder additives useful as binders for the sprayable thermal barrier coating powder mixture 208 may be added at temperatures above 500°C, such as between 500°C and 1000°C, such as up to 1200°C, such as up to 1500°C.

[0065] In this manner, it should be appreciated that the sprayable thermal barrier coating powder mixture 208, such as a dry composition of the sprayable thermal barrier coating powder mixture 208 consisting of the low surface area ceramic powder 214, the high surface area ceramic powder 214, and the binder additive 218 (if added), can together define an activation temperature of at least 300° C. to 1000° C., such as 300° C. to 1200° C., such as 300° C. to 1500° C.

[0066] In this manner, it should be understood that, as used herein, the term "activation temperature" for a particular component of the sprayable thermal barrier coating powder mixture 208 may refer to a temperature at which at least a portion of the particular component may serve as a binder for other components of the sprayable thermal barrier coating powder mixture 208 and / or as a binder to a substrate to which the sprayable thermal barrier coating powder mixture 208 is applied. Specifically, the term activation temperature refers to the temperature at which a component enters the beginning of the first stage of sintering. At this temperature (activation temperature), inter-material diffusion may result in "sintering neck formation" or chemical adhesion between particles (e.g., ceramic particles). In at least certain exemplary embodiments, due to the high surface area nature of the inorganic binder used, the temperature at which chemical adhesion occurs is significantly lower than the temperature when the engine is at takeoff speed / power level.

[0067] Therefore, it should be understood that as used herein, the term “activation temperature range” refers to a temperature range in which at least a portion of at least one component of the sprayable thermal barrier coating powder mixture 208 acts as a binder for the sprayable thermal barrier coating powder mixture 208 .

[0068] Furthermore, it should be understood that the curing temperature of the sprayable thermal barrier coating powder mixture 208 is defined within or overlaps with the activation temperature range of the sprayable thermal barrier coating powder mixture 208. For example, the high surface area ceramic powder 216 of the sprayable thermal barrier coating powder mixture 208 defines a curing temperature that is at least partially greater than 1000° C. and less than the upper limit of the activation temperature range of the sprayable thermal barrier coating powder mixture 208, such as less than 1500° C.

[0069] It should be understood that as used herein, the term “curing temperature” refers to a temperature above which the sprayable thermal barrier coating powder mixture 208 begins to undergo a process where the sprayable thermal barrier coating powder mixture 208 begins material diffusion and / or chemical diffusion.

[0070] In this manner, the sprayable thermal barrier coating powder mixture 208 may be applied to a portion of the thermal barrier coating 146 of a component of an engine in need of repair at a relatively low temperature, such as between 0° C. and 50° C. The sprayable thermal barrier coating powder mixture 208 may be held together in position on the worn portion 148 of the thermal barrier coating 146 by the temperature of the engine 10 when the engine 10 is started. In addition, the sprayable thermal barrier coating powder mixture 208 may be held together in position on the worn portion 148 of the thermal barrier coating 146 until the operating temperature of the engine 10 is sufficient to cure the sprayable thermal barrier coating powder mixture 208 in position on the worn portion 148 of the thermal barrier coating 146 as a permanent patch 150 of the thermal barrier coating 146. In this manner, the sprayable thermal barrier coating powder mixture 208 may be engine curable.

[0071] Still refer to Figure 4 In the sprayable thermal barrier coating powder mixture 208, it should be understood that the binder additive 218 may not constitute a majority of the dry composition of the sprayable thermal barrier coating powder mixture 208 ("dry composition" refers to the portion of all solid phases of the sprayable thermal barrier coating powder 208). For example, in the exemplary embodiment shown, the low surface area ceramic powder 214 and the high surface area ceramic powder 216 together account for at least 80 wt% of the dry composition of the sprayable thermal barrier coating powder mixture 208. However, it is worth noting that in other embodiments, the low surface area ceramic powder 214 and the high surface area ceramic powder 216 may together account for at least 90 wt% of the dry composition of the sprayable thermal barrier coating powder mixture 208, such as at least 95 wt% of the dry composition of the sprayable thermal barrier coating powder mixture 208. In this way, the resulting thermal barrier coating patch 150 can still be substantially formed of a high temperature resistant ceramic material.

[0072] In addition, it should be understood that for at least some exemplary embodiments, the low surface area ceramic powder 214 can comprise at least 50 wt % of the dry composition of the sprayable thermal barrier coating powder mixture. For example, the low surface area ceramic powder 214 can comprise at least 60 wt % of the dry composition, such as at least 70 wt % of the dry composition, such as up to 90 wt % of the dry composition.

[0073] It is worth noting that again briefly refer to Figure 3 And still refer to Figure 4 It should be understood that, as described throughout this application, the sprayable thermal barrier coating powder mixture 208 is "sprayable". In this way, it should be understood that the sprayable thermal barrier coating powder mixture 208 has fluidity, which is convenient for spraying with, for example, a carrier gas, a high-pressure gas source, etc. Figure 3In an embodiment, the sprayable thermal barrier coating powder mixture 208 can be sprayed onto a substrate, such as applied to the wear portion 148 of the thermal barrier coating 146, by atomizing the mixture with a high-pressure gas. To facilitate this application method and other methods, the sprayable thermal barrier coating powder mixture 208 also includes a liquid 220 added to the dry composition to form a slurry for spraying the mixture. The liquid can be configured to dry quickly during the application process. For example, the liquid may include a low boiling point liquid, such as liquid alcohol, liquid ethanol, liquid carbon dioxide, etc. For example, the boiling point of the low boiling point liquid can be defined as less than 100°C, such as less than 50°C, such as less than 0°C, such as greater than absolute zero.

[0074] The liquid 220 added to the dry composition to form the sprayable thermal barrier coating powder mixture 208 (also referred to as a slurry) can additionally or alternatively be a high vapor pressure fluid. For example, the vapor pressure of the liquid 220 can be defined as being above 2.3 kilopascals (kPa) at 20° C., such as above 4 kPa at 20° C., such as above 5.5 kPa at 20° C., such as up to 1,000 kPa at 20° C.

[0075] The addition of this low boiling point liquid / high vapor pressure fluid allows the sprayable thermal barrier coating powder mixture 208 to flow to the nozzle 202 to be applied to the thermal barrier coating 146 or other components, so that the thermal barrier coating 146 or other components can be repaired in situ, and can also evaporate relatively quickly to promote the engine to cure the sprayable thermal barrier coating powder mixture 208.

[0076] In certain exemplary embodiments, the sprayable thermal barrier coating powder mixture 208 may define a solids loading (i.e., the weight percentage of the dry composition portion of the sprayable thermal barrier coating powder mixture 208 relative to the wet composition portion of the sprayable thermal barrier coating powder mixture 208 - which is the desiccant for the embodiments in question) of 30% to 80%.

[0077] Additionally, in certain exemplary embodiments, the specific gravity of the sprayable thermal barrier coating powder mixture 208 may be defined as between approximately 0.8 g / cm3 and 3 g / cm3, such as between approximately 1 g / cm3 and 2.7 g / cm3.

[0078] The addition of a slurry having such a solid loading and specific gravity can reduce particle settling during the spraying process (including the pumping process), and can also reduce separation, agglomeration, reaction, polymerization, etc. In addition, such a configuration can ensure that the slurry / mixture 208 can be pumped through a relatively small tube, such as through a tube (e.g., tube 204) having a diameter of less than 0.1 inches, such as less than 0.075 inches, such as less than 0.06 inches.

[0079] By way of example only, in one exemplary embodiment, the sprayable thermal barrier coating powder mixture 208 may generally be formed according to one or more of the following embodiments:

[0080] Example 1

[0081] A sprayable thermal barrier coating powder mixture 208 comprising:

[0082] Powder 1, 21.6 g of 8YSZ ceramic oxide powder with a specific surface area of ​​<10 m 2 / g, as a low surface area ceramic powder with a median particle size of about 8 microns;

[0083] Powder 2, 5.4 g of 8YSZ ceramic oxide powder with a specific surface area > 10 m 2 / g, as a high surface area ceramic powder with a median particle size of about 1 micron. This powder can also be used as an inorganic binder;

[0084] 0.54 g of polyvinyl pyrrolidone organic binder;

[0085] 13.5 grams of denatured ethanol, as a solvent, and;

[0086] 13.5 g of acetone as the low boiling point liquid.

[0087] This formulation produces a good coating. The acetone acts as a drying agent, making it possible to dry the coating while the slurry is "in flight", thus producing a good quality coating.

[0088] Example 2

[0089] A sprayable thermal barrier coating powder mixture 208 comprising:

[0090] Powder 1, 21.6 g of 8YSZ ceramic oxide powder with a specific surface area of ​​<10 m 2 / g, as a low surface area ceramic powder with a median particle size of about 8 microns;

[0091] Powder 2, 5.4 g of 8YSZ ceramic oxide powder with a specific surface area > 10 m 2 / g, as a high surface area ceramic powder with a median particle size of about 1 micron. This powder can also be used as an inorganic binder;

[0092] 0.54 g of polyvinyl pyrrolidone organic binder;

[0093] 13.5 grams of denatured ethanol, as a solvent, and;

[0094] 13.5 g of petroleum ether as a low boiling point liquid.

[0095] In each of these examples, the prepared slurry was used to repair laboratory specimens with simulated engine failures in order to evaluate the repair process and spray application process. The slurry was piped to a gas atomizing nozzle and sprayed using a process configured on a simulator. The repaired specimens were cured and tested under simulated engine operation to determine the durability of the coating.

[0096] For each of these embodiments, in order to evaluate the repair efficiency, the specimens were tested in two different ways to simulate the engine environment. The first method is the jet engine thermal shock (JETS) test. In this test, the repaired samples were tested to evaluate their ability to withstand multiple thermal shocks at engine idle and take-off temperatures. The thermal shock test simulates the thermal cycle that the turbine section of the aircraft turbomachinery of the component undergoes in general operation. The second method is the furnace cycle test (FCT). For this test, the specimen is subjected to a thermal exposure cycle in the furnace. In a one-hour cycle, the specimen is quickly inserted into the bottom load furnace and kept at 1135°C for 45 minutes. The sample is then removed from the furnace and forced air cooled for 15 minutes before starting the next cycle. After 20 cycles, the sample is removed from the FCT and inspected. The sample remains in the test until 20% of the coating area is peeled off to determine the FCT life.

[0097] It should be understood that the above-described exemplary sprayable thermal barrier coating powder mixture 208 is provided as an example only. In other exemplary embodiments, the sprayable thermal barrier coating powder mixture 208 may have any other suitable configuration. For example, in other exemplary embodiments, the low surface area ceramic powder 214 may additionally or alternatively be a low surface area ceramic powder precursor. For example, the low surface area ceramic powder precursor may be an organosilicon, a titanium-based composition, or a phosphate-based composition that thermally decomposes to form a high temperature resistant oxide for use as the low surface area ceramic powder 214. This may occur after the sprayable thermal barrier coating powder mixture 208 is applied to the substrate.

[0098] Coatings formed using the sprayable thermal barrier coating powder mixture 208 according to one or more of these configurations can produce a coating having a relatively high thermal resistance / low thermal conductivity that can be directly attached to the surface of the component 252 without requiring any special degreasing, gleaning, or oxide removal. Figure 5 and 6 , which provides a close-up cross-sectional view of a repair coating 250 applied to a surface of an underlying component 252 . Figure 5 A close-up cross-sectional view showing a repair coating 250 applied to a surface of an underlying component 252, Figure 6 Shows Figure 5 A close up view of a portion of the repair coating 250.

[0099] As shown, according to one or more exemplary aspects of the present disclosure, such as one or more of the above-described exemplary aspects, a repair coating 250 is formed from a sprayable thermal barrier coating powder mixture 208. For example, the repair coating 250 includes a low surface area ceramic powder 214 and a high surface area ceramic powder 216. It should also be understood that the repair coating 250 defines a plurality of pores 254, thereby defining a porosity for improving thermal protection / reducing thermal conductivity. For example, an exemplary coating 250 formed using a sprayable thermal barrier coating powder mixture 208 according to one or more of the above-described constructions can produce a repair coating 250 having a designed porosity that provides a desired amount of thermal protection with a relatively thin repair coating 250. For example, in at least some exemplary embodiments, as Figure 5 and Figure 6 The thermal conductivity of the repair coating 250 shown can be adjusted to between 0.4 W / m-Kelvin and 2 W / m-Kelvin at 1000°C.

[0100] For example, Figure 5 and Figure 6 The thermal conductivity of the repair coating 250 shown can be tailored by varying the porosity and maximum pore size within the coating 250. As used herein, the term "maximum pore size" refers to the largest lateral measurement of a particular pore 254. In certain exemplary embodiments, the maximum pore size produced by the low surface area ceramic powder 214 can be 15 microns or less, while the maximum pore size produced by the high surface area ceramic powder 216 can be 1 micron or less.

[0101] Due to its inherently lower thermal conductivity, the requirement for coating 250 to completely insulate the underlying material may be lower than for the original coating 250. A thinner coating 250 may result in lower in-plane stresses and allow the coating 250 to cure in the engine.

[0102] Now refer to Figure 7 , a method 300 for in-situ repair of a thermal barrier coating of a component of a gas turbine engine is provided. The method 300 may utilize one or more of the exemplary aspects of the sprayable thermal barrier coating powder mixture described above. Furthermore, the method 300 may be used in one or more of the exemplary components or engines described above, or may alternatively be used in any other suitable component, engine, or otherwise.

[0103] Figure 7The method 300 includes: (302) spraying a thermal barrier coating powder mixture in situ onto a component of a gas turbine engine, the thermal barrier coating powder mixture including a low surface area ceramic powder, a low surface area ceramic powder precursor, or both, the thermal barrier coating powder mixture also including a high surface area ceramic powder, and the activation temperature of the thermal barrier coating powder mixture is defined as a range of 300° C. to 1200° C. In this manner, it should be understood that (302) spraying the thermal barrier coating powder mixture in situ onto the component of the gas turbine engine may include: spraying the thermal barrier coating powder mixture onto the component of the gas turbine engine while the component is installed in the gas turbine engine, when the gas turbine engine is substantially assembled (e.g., at least 80% assembled), while the gas turbine engine is installed on a vehicle (e.g., a wing or fuselage of an aircraft), or a combination thereof.

[0104] In addition, for the exemplary aspects shown, (302) in-situ spraying of the thermal barrier coating powder mixture onto a component of a gas turbine engine includes: (304) in-situ spraying of the thermal barrier coating powder mixture onto a component of a gas turbine engine at a thickness greater than 2 mils (i.e., one thousandth of an inch) and less than 25 mils.

[0105] Additionally, for the exemplary aspects shown, (302) spraying the thermal barrier coating powder mixture in situ onto the component of the gas turbine engine includes: (306) spraying the thermal barrier coating powder mixture in situ onto the component of the gas turbine engine using a pressurized gas source. In this manner, (302) spraying the thermal barrier coating powder mixture in situ onto the component of the gas turbine engine may include: atomizing the thermal barrier coating powder mixture. In at least some exemplary aspects, the pressurized gas may be any suitable carrier gas, such as argon or air.

[0106] Further for Figure 7 In an exemplary aspect of the invention, method 300 further includes: (308) operating the gas turbine engine to cure the thermal barrier coating powder mixture on the component. In this manner, it should be understood that (302) spraying the thermal barrier coating powder mixture in situ onto the component of the gas turbine engine may include: spraying the thermal barrier coating powder mixture in situ onto the component of the gas turbine engine when the engine is not operating and the temperature is below, for example, 100° C. (e.g., below 50° C.). In addition, (308) operating the gas turbine engine to cure the thermal barrier coating powder mixture on the component may include: after (302) spraying the thermal barrier coating powder mixture in situ onto the component of the gas turbine engine, operating the gas turbine engine to cure the thermal barrier coating powder mixture on the component.

[0107] Still reference Figure 7For the exemplary method 300 shown, (308) operating the gas turbine engine to cure the thermal barrier coating powder mixture on the component includes: (310) exposing the thermal barrier coating powder mixture on the component to an operating temperature between 1000°C and 1500°C.

[0108] This written description uses embodiments to disclose the invention, including the best mode, and also enables any person skilled in the art to practice the invention, including making and using any device or system and performing any integrated method. The patentable scope of the invention is defined by the claims, and may include other embodiments that occur to a person skilled in the art. If these other embodiments include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements that do not differ substantially from the literal language of the claims, then these other embodiments are within the scope of the claims.

[0109] Further aspects of the present invention are provided by the following items:

[0110] A sprayable thermal barrier coating powder mixture for a gas turbine engine comprising: A dry composition comprising a low surface area ceramic powder having a median particle size greater than 5 microns and less than 40 microns and a high surface area ceramic powder having a median particle size less than 5 microns, the low surface area ceramic powder comprising at least 50 wt% of the dry composition of a sprayable thermal barrier coating powder mixture; and at least one organic binder additive configured to function as a binder at temperatures below 500°C; The at least one organic binder additive comprises less than 5 wt % of the dry composition.

[0111] A mixture of more than one of these items, wherein the surface area of ​​the low surface area ceramic powder is less than 10 m2 / g and the surface area of ​​the high surface area ceramic powder is greater than 10 m2 / g and less than 4000 m2 / g.

[0112] Mixtures of more than one of these items, wherein the at least one organic binder additive is selected from one or more of the following: polyvinyl alcohol, polyethylene oxide, polyethylene glycol, polyvinyl pyrrolidone, acrylates, acrylamides and copolymers.

[0113] A mixture of more than one of these items, wherein the mixture further comprises: a liquid added to the dry composition to form a slurry for spraying the mixture.

[0114] A mixture of more than one of these items wherein the liquid comprises a low boiling point liquid.

[0115] A mixture of more than one of these items, wherein the solids loading of the mixture is between 30% and 80% by mass.

[0116] A mixture of more than one of these items, wherein the mixture has a density between about 0.8 g / cm3 and 3 g / cm3.

[0117] A mixture of one or more of these items, wherein the thermal conductivity of the mixture after curing is between 0.4 W / m-Kelvin and 2 W / m-Kelvin at 1000°C.

[0118] A mixture of one or more of these items, wherein the activation temperature of the dry composition is in the range of 300°C to 1200°C such that the thermal barrier coating powder mixture is configured to be sprayed in situ and cured by exposure to operating temperatures within a gas turbine engine.

[0119] A mixture of more than one of these items, wherein the dry composition further comprises at least one additional binder additive, and the activation temperature of the low surface area ceramic powder, the high surface area ceramic powder, the at least one organic binder additive and the at least one additional binder additive as a whole is in the range of at least 300°C to 1200°C.

[0120] A mixture of one or more of these items wherein the high surface area ceramic powder has a curing temperature greater than 1000°C.

[0121] A mixture of more than one of these items wherein the low surface area ceramic powder and the high surface area ceramic powder together comprise at least 95 wt % of the dry composition of the sprayable thermal barrier coating powder mixture.

[0122] A mixture of more than one of these items, wherein the low surface area ceramic powder and the high surface area ceramic powder each comprise zirconium oxide.

[0123] A method for in-situ repair of a thermal barrier coating of a component of a gas turbine engine, comprising: spraying a thermal barrier coating powder mixture in situ onto a component of a gas turbine engine, the thermal barrier coating powder mixture comprising a dry composition comprising a low surface area ceramic powder, a low surface area ceramic powder precursor, or both, the dry composition of the thermal barrier coating powder mixture further comprising a high surface area ceramic powder and at least one organic binder additive configured to function as a binder below 500° C., the at least one organic binder additive comprising less than 5 wt % of the dry composition of the thermal barrier coating powder mixture; the thermal barrier coating powder mixture defining an activation temperature in the range of 300° C. to 1200° C.; and A gas turbine engine is run to cure a thermal barrier coating powder mixture on a component.

[0124] The method of one or more of these items, wherein the surface area of ​​the low surface area ceramic powder is less than 10 m2 / g and the surface area of ​​the high surface area ceramic powder is greater than 10 m2 / g and less than 4000 m2 / g

[0125] The method of one or more of these items, wherein the at least one organic binder additive is selected from one or more of the following: polyvinyl alcohol, polyethylene oxide, polyethylene glycol, polyvinyl pyrrolidone, acrylates, acrylamides and copolymers.

[0126] The method of more than one of these items, wherein the low surface area ceramic powder has a median particle size greater than 5 microns and less than 40 microns.

[0127] The method of one or more of these items, wherein operating the gas turbine engine to cure the thermal barrier coating powder mixture on the component includes exposing the thermal barrier coating powder mixture on the component to an operating temperature between 1000°C and 1500°C.

[0128] The method of one or more of these items, wherein in-situ spraying the thermal barrier coating powder mixture onto the gas turbine engine component comprises: in-situ spraying the thermal barrier coating powder mixture onto the gas turbine engine component at a thickness greater than 2 mils and less than 25 mils.

[0129] The method of one or more of these items, wherein in-situ spraying the thermal barrier coating powder mixture onto the gas turbine engine component comprises: spraying the thermal barrier coating powder mixture onto the gas turbine engine component in-situ using a pressurized gas source.

[0130] The method of one or more of these items, wherein in-situ spraying the thermal barrier coating powder mixture onto the gas turbine engine component includes: in-situ spraying the thermal barrier coating powder mixture onto the gas turbine engine component through one or more tubes having a diameter of 0.06 inches or less.

[0131] The method of one or more of these items, wherein the thermal barrier coating powder mixture further comprises a desiccant to form a slurry, the desiccant comprising ethanol and a low boiling point liquid.

[0132] The method of one or more of these items, wherein the thermal barrier coating powder mixture comprises a low surface area ceramic powder, said low surface area ceramic powder and said high surface area ceramic powder together comprising at least 95 wt % of the dry composition of the thermal barrier coating powder mixture.

[0133] A sprayable thermal barrier coating powder mixture for a gas turbine engine comprising: a dry composition comprising a low surface area ceramic powder, a low surface area ceramic powder precursor, or both, and a high surface area ceramic powder, the dry composition defining an activation temperature in the range of at least 300° C. to 1200° C. such that the thermal barrier coating powder mixture is configured to be sprayed in situ and cured by exposure to operating temperatures within the gas turbine engine; and at least one organic binder additive configured to function as a binder at temperatures below 500°C; The at least one organic binder additive comprises less than 5 wt % of the dry composition.

[0134] Mixtures of more than one of these items, wherein the organic binder additive is selected from one or more of the following: polyvinyl alcohol, polyethylene oxide, polyethylene glycol, polyvinyl pyrrolidone, acrylates, acrylamides and copolymers.

[0135] A mixture of more than one of these items, wherein the mixture comprises the low surface area ceramic powder, the surface area of ​​the low surface area ceramic powder is less than 10 m2 / g, and the surface area of ​​the high surface area ceramic powder is greater than 10 m2 / g and less than 4000 m2 / g.

[0136] A mixture of more than one of these items, wherein if the mixture contains the low surface area ceramic powder, the surface area of ​​the low surface area ceramic powder is less than 5 m2 / g, if the mixture contains the low surface area ceramic powder precursor, the low surface area ceramic powder precursor is configured to form a powder with a surface area of ​​less than 5 m2 / g, and the surface area of ​​the high surface area ceramic powder is greater than 10 m2 / g and less than 4000 m2 / g.

[0137] A mixture of more than one of these items, wherein the mixture comprises a low surface area ceramic powder having a median particle size greater than 5 microns and less than 40 microns.

Claims

1. A sprayable thermal barrier coating powder mixture for a gas turbine engine comprising: A dry composition comprising a low surface area ceramic powder having a median particle size greater than 5 microns and less than 40 microns and a high surface area ceramic powder having a median particle size less than 5 microns, the low surface area ceramic powder comprising at least 50 wt% of the dry composition of a sprayable thermal barrier coating powder mixture; and at least one organic binder additive configured to function as a binder at temperatures below 500°C; The at least one organic binder additive comprises less than 5 wt % of the dry composition.

2. The mixture according to claim 1, wherein The surface area of ​​the low surface area ceramic powder is less than 10 m2 / g, and the surface area of ​​the high surface area ceramic powder is greater than 10 m2 / g and less than 4000 m2 / g.

3. The mixture according to claim 1, wherein The at least one organic binder additive is selected from one or more of the following: polyvinyl alcohol, polyethylene oxide, polyethylene glycol, polyvinyl pyrrolidone, acrylates, acrylamides, and copolymers.

4. The mixture according to claim 1, wherein The mixture also comprises: A liquid that is added to the dry composition to form a slurry for spraying the mixture.

5. The mixture according to claim 4, wherein The liquid comprises a low boiling point liquid.

6. The mixture according to claim 5, wherein The solids loading of the mixture is between 30% and 80% by mass.

7. The mixture according to claim 5, wherein The density of the mixture is between about 0.8 g / cm3 and 3 g / cm3.

8. The mixture according to claim 5, wherein The thermal conductivity of the mixture after curing is between 0.4 W / m-Kelvin and 2 W / m-Kelvin at 1000°C.

9. A method for in-situ repair of a thermal barrier coating of a component of a gas turbine engine, comprising: spraying a thermal barrier coating powder mixture in situ onto a component of a gas turbine engine, the thermal barrier coating powder mixture comprising a dry composition comprising a low surface area ceramic powder, a low surface area ceramic powder precursor, or both, the dry composition of the thermal barrier coating powder mixture further comprising a high surface area ceramic powder and at least one organic binder additive configured to function as a binder below 500° C., the at least one organic binder additive comprising less than 5 wt % of the dry composition of the thermal barrier coating powder mixture; The thermal barrier coating powder mixture defines an activation temperature in the range of 300°C to 1200°C; and A gas turbine engine is run to cure a thermal barrier coating powder mixture on a component.

10. A sprayable thermal barrier coating powder mixture for a gas turbine engine comprising: a dry composition comprising a low surface area ceramic powder, a low surface area ceramic powder precursor, or both, and a high surface area ceramic powder, the dry composition defining an activation temperature in the range of at least 300° C. to 1200° C. such that the thermal barrier coating powder mixture is configured to be sprayed in situ and cured by exposure to operating temperatures within the gas turbine engine; and at least one organic binder additive configured to function as a binder at temperatures below 500°C; The at least one organic binder additive comprises less than 5 wt % of the dry composition.

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