Patent Grant
10646894
The present invention is directed to a squeegee apparatus useful for dispensing and applying a coating repair composition. The present invention is also directed to a method of use of the squeegee apparatus disclosed herein.
Higher operating temperatures of gas turbine engines are continually being sought in order to increase the efficiency of the engines. However, as operating temperatures increase, the high temperature durability of the components of the engine must correspondingly increase. Significant advances in high temperature capabilities have been achieved through the formulation of nickel, cobalt and iron based superalloys. These superalloys can be designed to withstand temperatures in the range of about 1000 to about 1100° C. or higher. Nonetheless, when used to form components of the turbine, such as combustor liners, augmentor hardware, shrouds and high and low-pressure nozzles and blades, the superalloys alone could be susceptible to damage by oxidation and hot corrosion attack. Accordingly, these components are typically protected by an environmental and/or a thermal barrier coating (“TBC”). In general, TBCs can be used in conjunction with the superalloys in order to reduce the cooling air requirements associated with a given turbine. Ceramic materials, such as yttrium-stabilized zirconia (YSZ), are widely used as a TBC or topcoat of TBC systems. These materials are employed because, for example, they can be readily deposited by plasma-spraying and physical vapor deposition (PVD) techniques, and they also generally exhibit desirable thermal characteristics. In general, these TBCs can be utilized in conjunction with the superalloys in order to reduce the cooling air requirements associated with a given turbine.
In order to be effective, TBCs need to possess low thermal conductivity, strongly adhere to the component and remain adhered through many heating and cooling cycles. The latter requirement is particularly demanding due to the different coefficients of thermal expansion between the ceramic materials and the superalloy substrates that they protect. To promote adhesion and extend the service life of a TBC, an oxidation-resistant bond coating typically takes the form of a diffusion aluminide coating or an overlay coating, such as MCrAlX where M is iron, cobalt and/or nickel and X is yttrium or another rare earth element. During the deposition of a ceramic TBC and subsequent exposures to high temperatures, such as during engine operation, these bond coats form a tightly adherent alumina (Al2O3) layer or scale that adheres the TBC to the bond coat.
The service life of a TBC is typically limited by a spallation event brought on by, for example, thermal fatigue. Accordingly, a significant challenge has been to obtain a more adherent ceramic layer that is less susceptible to spalling when subjected to thermal cycling. Though significant advances have been made, there is the inevitable requirement to repair components whose thermal barrier coatings have spalled. Though spallation typically occurs in localized regions or patches, a conventional repair method has been to completely remove the TBC after removing the affected component from the turbine or other area, restore or repair the bond coat as necessary and recoat the engine component. Techniques for removing TBCs include grit blasting or chemically stripping with an alkaline solution at high temperatures and pressures. However, grit blasting is a slow, labor-intensive process and can erode the surface beneath the coating. The use of an alkaline solution to remove a TBC also is less than ideal because the process typically requires the use of an autoclave operating at high temperatures and pressures. Consequently, some conventional repair methods are labor intensive and expensive, and can be difficult to perform on components with complex geometries, such as airfoils and shrouds. As an alternative, U.S. Pat. No. 5,723,078 to Nagaraj et al. teach selectively repairing a spalled region of a TBC by texturing the exposed surface of the bond coat, and then depositing a ceramic material on the textured surface by plasma spraying. While avoiding the necessity to strip the entire TBC from a component, the repair method taught by Nagaraj et al. requires removal of the component in order to deposit the ceramic material.
In the case of large power generation turbines, completely halting power generation for an extended period of time in order to remove components whose TBCs have suffered only localized spallation is not economically desirable.
U.S. Pat. No. 7,476,703 discloses an in-situ method and composition for repairing a thermal barrier coating, which is based on a silicone resin system. U.S. Pat. No. 6,413,578 discloses an in-situ method for repairing thermal barrier coating with a ceramic paste. In situ methods of repairing a damaged component, such as TBC coating, are also disclosed in U.S. Pat. Nos. 7,509,735, 8,563,080, and U.S. Patent Application Publication No. 2015/0174837. A repair composition is disclosed in U.S. Pat. No. 6,875,464. A commercially available repair composition, AIM-MRO SR Resin Patch, may also be used for TBC repair.
However, there remains a need for an apparatus that would allow for effective application of repair composition to damaged regions of TBC. Such effective application includes application of a repair composition not only to flat surfaces but also to non-planar curved surfaces, which also suffer from TBC damage in turbine assemblies. Accordingly, the present invention seeks to provide a novel squeegee apparatus designed for dispensing and effectively applying a repair composition and methods of use thereof.
One object of the present invention is to provide a squeegee apparatus useful for dispensing and applying a coating repair composition. Another object of the present invention is to provide method of use of the squeegee apparatus disclosed herein.
Accordingly, in one embodiment, the invention is directed to a squeegee apparatus which includes a main housing including an inlet end and an outlet end, the outlet end including an extrusion face and a protruding lip member, wherein the lip member is flexible and elongated, the inlet end including an inlet opening, and the extrusion face including at least one outlet opening, wherein the inlet opening and the at least one outlet opening are in fluid communication with each other within the main housing.
In another embodiment, the invention is directed to a method for repairing a thermal barrier coating with a squeegee apparatus, wherein the thermal barrier coating is located on a component and wherein the thermal barrier coating has a damaged region, wherein the squeegee apparatus includes a main housing including an inlet end and an outlet end, the outlet end including an extrusion face and a protruding lip member, wherein the lip member is flexible and elongated, the inlet end including an inlet opening, and the extrusion face including at least one outlet opening, and wherein the inlet opening and the at least one outlet opening are in fluid communication with each other within the main housing. In one embodiment, the method includes supplying a repair composition into the inlet opening, and depositing the repair composition from the at least one outlet opening onto the damaged region and concurrently traversing the squeegee apparatus over the damaged region while contacting a thermal barrier coating adjacent to the damaged region with the lip member, wherein the extrusion face is situated in front of the lip member relative to a direction of the traversing of the squeegee apparatus over the damaged region, whereby the repair composition is deposited onto the damaged region to form a patch.
The squeegee apparatus disclosed herein is advantageous because it can deliver repair composition at a desired flow rate, which may be constant or variable. Additionally, the disclosed squeegee apparatus has a flexible lip member which allows the squeegee apparatus to adopt to various curvatures of the coating being repaired, which ensures that the repair composition is delivered against the surface and covers the damaged region. Furthermore, the squeegee apparatus described herein may be easily 3D printed using additive manufacturing methods. These and additional features provided by the embodiments discussed herein will be more fully understood in view of the following detailed description, in conjunction with the drawings.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
In the following specification and the claims which follow, reference will be made to a number of terms, which shall be defined to have the following meanings.
The singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.
Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about”, is not to be limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value.
As used herein, the term “damaged region” refers to any deposit or damage on a surface of an internal component of a turbine assembly. Such damaged region may be a result of dust accumulation, coating spallation, oxidation, corrosion, erosion, impact, wear, foreign object damage, or cracking.
As used herein, the term “thermal barrier coating” or “TBC” refers to known in the art ceramic materials systems applied to metallic and ceramic substrates, such as on gas turbine or aero-engine parts, operating at elevated temperatures, as a form of heat management. The term “TBC”, as used herein, includes environment barrier coating.
As used herein, the term “repair composition” refers to a composition that may be used to repair the damaged region of a TBC.
In one embodiment, the invention is directed to a squeegee apparatus which includes a main housing including an inlet end and an outlet end, the outlet end including an extrusion face and a protruding lip member, wherein the lip member is flexible and elongated, the inlet end including an inlet opening, and the extrusion face including at least one outlet opening, wherein the inlet opening and the at least one outlet opening are in fluid communication with each other within the main housing.
In one embodiment, at least one outlet opening is a plurality of outlet openings. In another embodiment, the extrusion face is elongated and positioned lengthwise adjacent to the lip member. In one embodiment, the extrusion face is elongated and positioned lengthwise adjacent to the lip member, and wherein the at least one outlet opening is a plurality of outlet openings.
In another embodiment, the main housing further includes an internal chamber, wherein the internal camber is in fluid communication with the inlet opening, and wherein the internal chamber is in fluid communication with the plurality of outlet openings via a plurality of flow channels located within the main housing.
With respect to the lip member, in addition to removing the excess repair composition, the compliance (i.e., flexibility) of the lip member allows for less accurate positioning of the squeegee apparatus from the surface. When considering a straight or a curved surface, if the lip member is rigid, the positioning of the squeegee apparatus has to be extremely accurate to ensure that the repair composition is deposited in the damaged region flush with the original TBC surface (surface profile tracking) and also to ensure that excess repair composition above and around the damaged region is removed. Because the lip member of the present invention is flexible, the positioning of the squeegee apparatus does not have to be extremely accurate to ensure that the repair composition is deposited in the damaged region flush with the original TBC surface. The flexibility of the lip member also allows for removal of excess repair composition from above and around the damaged region. Furthermore, when considering a surface like that of a combustion liner, which is curved in two orthogonal directions, if the curvature is slight, the compliance of the lip member can be used to accommodate such curvature. In one embodiment, the edge of the lip member (i.e, the outer edge of the lip member which comes into contact with the TBC during performance of the methods of the invention, see edge 40 in
Furthermore, the ease of repair is improved if the length of the lip member is greater than the maximal width of the damaged region which is being repaired. Thus, in one embodiment, the length of the lip member is greater than the maximal width of the damaged region. Thus, if the damaged region has a circular shape, the lip member will be in contact with the surface of the TBC on either side of the damaged region. The repair is also possible when the lip member is shorter than the maximal width of the damaged region. Thus, in another embodiment, the length of the lip member is less than the maximal width of the damaged region.
In another embodiment, if the damaged region has a shape that is other than circular, the length of the lip member is long enough to allow for the lip member to be in contact with surface of the TBC on either side of the damaged region as the lip member traverses over the damaged region. For example, if the damaged region has a long and narrow shape, the lip member may be traversed perpendicularly to the damaged area, with sides of the lip member in contact with the surface of the TBC as the lip member traverses over the damaged region.
In one embodiment, the inlet end is mounted to an adaptor, the adaptor further mounted to an outlet end of a conduit, wherein the adaptor includes a sensor operable to detect presence of a repair composition in the adaptor. In another embodiment, the conduit further includes an inlet end and wherein the inlet end of the conduit is mounted to a repair composition storage apparatus, wherein the repair composition storage apparatus is operable to deliver the repair composition to the inlet opening via the conduit and the adaptor.
In another embodiment, the invention is directed to a method for repairing a thermal barrier coating with a squeegee apparatus, wherein the thermal barrier coating is located on a component and wherein the thermal barrier coating has a damaged region, wherein the squeegee apparatus includes a main housing including an inlet end and an outlet end, the outlet end including an extrusion face and a protruding lip member, wherein the lip member is flexible and elongated, the inlet end including an inlet opening, and the extrusion face including at least one outlet opening, and wherein the inlet opening and the at least one outlet opening are in fluid communication with each other within the main housing. In one embodiment, the method includes supplying a repair composition into the inlet opening, and depositing the repair composition from the at least one outlet opening on the extrusion face onto the damaged region and concurrently traversing the squeegee apparatus over the damaged region while contacting a thermal barrier coating adjacent to the damaged region with the lip member, wherein the extrusion face is situated in front of the lip member relative to a direction of the traversing of the squeegee apparatus over the damaged region, whereby the repair composition is deposited onto the damaged region to form a patch.
In one embodiment, the method further includes, subsequent to the depositing of the repair composition, traversing the squeegee apparatus over the patch while contacting the patch with the lip member. In another embodiment, the method further includes heat treating the patch at a temperature of from about 900° C. to about 1400° C. Heat treating cures the patch and such heat treatment could take place while the turbine is run under normal operating conditions.
The squeegee apparatus used in the methods described herein could be any embodiment of the squeegee apparatus described herein.
In one embodiment, the at least one outlet opening 17 is a plurality of outlet openings 17, as shown in
In another embodiment, the main housing 11 further includes an internal chamber 18, wherein the internal chamber 18 is in fluid communication with the inlet opening 16, and wherein the internal chamber 18 is in fluid communication with the plurality of outlet openings 17 via a plurality of flow channels 19 located within the main housing 11, for example, as shown in
In one embodiment, as shown in
Embodiments of methods of the invention are shown in
In one embodiment shown in
The lip member and any other part of the squeegee apparatus, including the entire squeegee apparatus, may be compliant (i.e., flexible) and made from rubber-like low durometer material with shore hardness of approximately 60-62 on the A scale. Alternatively, the main housing of the squeegee apparatus may be not flexible while the lip member is flexible. Thus, the lip member may be made from rubber-like low durometer material with shore hardness of approximately 60-62 on the A scale. The squeegee apparatus may be easily attached and removed from the adaptor for easy replacement. The removed used squeegee apparatus may be discarded or cleaned, for example, with a water-based cleaning solution.
The squeegee apparatus may be secured to an end-effector, wherein the end-effector is operable to control movement of the squeegee apparatus. The squeegee apparatus may be secured to the end-effector directly or indirectly, for example, via the adaptor. Such end-effector may be an articulating and/or telescoping arm. The end-effector may be operated manually or it may be secured to a repair device.
The squeegee apparatus may have a compact design intended to cover the maximal dimension of spallation area (i.e., damaged region) on damaged combustor liners. Typically, the maximal dimension of such damaged region is 50 mm. Minimizing the dimensions of the squeegee apparatus allows for a repair device to access a confined space and avoid collision with obstacles. A flow sensor may be installed inside of the adaptor to detect arrival of the repair composition at the squeegee apparatus. This also gives a feedback for coordination of repair composition flow with the motion of the end-effector during the repair process.
This written description uses examples to disclose embodiments of the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is not limited to the scope of the provided examples, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements or method steps that do not differ from the literal language of the claims, or if they include equivalent structural elements or method steps with insubstantial differences from the literal language of the claims.
A specific embodiment of the squeegee apparatus of the invention is shown in
Other embodiments of the squeegee apparatus will differ from the embodiment of Example 1. For example, other embodiments of the squeegee apparatus may differ in materials used, shape, number and orientation of outlet openings, and dimensions. For example, the length of the lip member may be from 0.5 to 3.0 inches. Ranges for various properties of other embodiments of the squeegee apparatus of the invention are provided in Table 2.
Throughout this application, various references are referred to. The disclosures of these publications in their entireties are hereby incorporated by reference as if written herein.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as falling within the true spirit of the invention.
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