Patent Publication Number: US-2016243639-A1

Title: Process for fabricating multilayer component

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application relates to and claims the benefit of U.S. patent application Ser. No. 13/754,281, filed Jan. 30, 2013, entitled “Multilayer Component and Fabrication Process,” the disclosures of which are incorporated by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention is directed to components and fabrication processes. More particularly, the present invention relates to multilayer components and fabrication processes. 
     BACKGROUND OF THE INVENTION 
     Gas turbine engines and power generation turbines operate at high temperatures in order to increase their efficiency. Various advancements have been employed to enable the components, such as airfoils, of such engines to operate for longer periods of time at such high temperature. Airfoils employed in modem, high efficiency power generation combustion turbine engines rely on high quality materials such as single crystal alloys and precise control of the part&#39;s internal and external dimensions. In addition to the use of high temperature resistant superalloys, various airfoils have been designed to include internal cooling systems. One such internal cooling system is the use of cooling passages located inside and near the surface of the airfoil. 
     A number of techniques have been employed to provide such turbine airfoils with near surface cooling passages. For example, some techniques have used high efficiency, thin-walled turbine components, such as turbine blade airfoils comprising a superalloy substrate with cooling channels covered by a thin superalloy skin. The thin skin is bonded to the inner spar structure of a turbine blade airfoil. One method of forming cooling passages includes forming an internal channel within an article, such as a cooling channel in an air-cooled blade, vane, shroud, combustor or duct of a gas turbine engine. The method generally entails forming a substrate to have a groove recessed in its surface. A sacrificial material is deposited in the groove to form a filler that can be preferentially removed from the groove. A permanent layer is deposited on the surface of the substrate and over the filler, after which the filler is removed from the groove to yield the desired channel in the substrate beneath the permanent layer. Another method includes forming cooling passages by machining portions of a substrate of a component. 
     Such techniques can have several drawbacks. Use of specialty materials can be expensive, can be limited based upon availability, can require additional research to address other features of the specialty materials, and can otherwise limit flexibility of applications. Similarly, machining of materials can result in undesirable features, such as, an inability to reproduce or repair components that have already been machined. In addition, machining of such cooling holes is especially difficult in near-surface components and/or complex-shaped parts (such as curved parts). 
     A multilayer component and fabrication process that do not suffer from one or more of the above drawbacks would be desirable in the art. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In an exemplary embodiment, a multilayer component includes a ceramic coating layer, a bond coat layer abutting the ceramic coating layer, a foil surface layer abutting the bond coat layer, and a channel-forming material positioned between the foil surface layer and a substrate. The channel-forming material defines at least a portion of a channel. 
     In another exemplary embodiment, a multilayer component having a channel is at least partially defined by a channel-forming material brazed with a foil surface layer to a substrate of the multilayer component. 
     In another exemplary embodiment, a process of fabricating a multilayer component includes applying one or more layers to a foil surface layer and applying a channel-forming material to at least partially define a channel between the foil surface layer and a substrate. 
     Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of an exemplary multilayer component according to an embodiment of the disclosure. 
         FIG. 2  is a schematic view of an exemplary multilayer component according to an embodiment of the disclosure. 
         FIG. 3  is a schematic view of an exemplary multilayer component according to an embodiment of the disclosure. 
         FIG. 4  is a schematic view of an exemplary multilayer component according to an embodiment of the disclosure. 
         FIG. 5  is a flow diagram of an exemplary process of fabricating an exemplary multilayer component according to an embodiment of the disclosure. 
         FIG. 6  is a flow diagram of an exemplary process of fabricating an exemplary multilayer component according to an embodiment of the disclosure. 
         FIG. 7  is a flow diagram of an exemplary process of fabricating an exemplary multilayer component according to an embodiment of the disclosure. 
     
    
    
     Wherever possible, the same reference numbers will be used throughout the drawings to represent the same parts. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Provided is an exemplary multilayer component and fabrication process. Embodiments of the present disclosure, for example, in comparison to cooling arrangements that do not include one or more of the features disclosed herein, permit more time-efficient and/or cost-efficient formation of cooling channels in components, allow a higher level of flexibility in material selection for multilayer components, reduce overall turbine component costs, permit machining to be reduced or eliminated (or used in an augmented manner), permit specialty materials to be reduced or eliminated (or used in an augmented manner), provide increased oxidation resistance, reduce furnace time for brazing of components, or a combination thereof. 
     Referring to  FIGS. 1-4 , a multilayer component  100  includes a channel  112  positioned between a foil surface layer  106  and a substrate  110 . The substrate  110  is any suitable metal or metallic alloy, for example, a nickel-based alloy, a cobalt-based alloy, or a combination thereof. In one embodiment, the substrate  110  has a composition, by weight, of about 22% chromium, about 18% iron, about 9% molybdenum, about 1.5% cobalt, about 0.6% tungsten, about 0.10% carbon, about 1% manganese, about 1% silicon, about 0.008% boron, incidental impurities, and a balance nickel. In one embodiment, the substrate  110  has a composition, by weight, of between about 50% and about 55% Nickel+Cobalt, between about 17% and about 21% chromium, between about 4.75% and about 5.50% columbium+tantalum, about 0.08% carbon, about 0.35% manganese, about 0.35% silicon, about 0.015% phosphorus, about 0.015% sulfur, about 1.0% cobalt, between about 0.35% and about 0.80% aluminum, between about 2.80% and about 3.30% molybdenum, between about 0.65% and about 1.15% titanium, between about 0.001% and about 0.006% boron, about 0.15% copper, incidental impurities, and a balance of iron. 
     In one embodiment, the multilayer component  100  is an airfoil, a vane, a blade, a nozzle, a duct, a complex-shaped component, a component having a curved region, any other suitable turbine component, or a combination thereof. The channel  112  is at least partially defined by a channel-forming material  108 . In one embodiment, the channel-forming material  108  and the foil surface layer  106  are brazed to the substrate  110  simultaneously or separately as is shown and described below with reference to  FIGS. 5-6 . 
     The multilayer component  100  includes any suitable number of layers or types of layers. As shown in  FIGS. 1-4 , in one embodiment, the multi layer component includes the foil surface layer  106 , the substrate  110 , the channel-forming material  108 , a bond coat layer  104 , and a ceramic coating layer  102 . In another embodiment, the multilayer component  100  includes the foil surface layer  106 , the substrate  110 , and the channel-forming material  108  As will be appreciated, any suitable intermediate layers or additional layers are capable of further defining the multilayer component  100 . 
     The foil surface layer  106  is any suitable material capable of being applied to the channel-forming material  108 , for example, by brazing. The foil surface layer  106  is capable of adhering to the substrate  110 , the channel-forming material  108 , the bond coat  104 , or a combination thereof. In one embodiment, the foil surface layer  106  abuts the bond coat layer  104  and/or the channel-forming layer  108 . In one embodiment, the foil surface layer  106  is an interlayer with material selected based upon materials used in the bond coating layer  104  and the channel-forming layer  108 , for example, to provide a predetermined thermal property transition from the ceramic coating layer  102  to the substrate  110  to reduce or mitigate thermal-induced stress built up in the entire coating structure. In one embodiment, the foil surface layer  106  includes oxidation resistance that is equal to or better than that of the substrate  110  and/or a thermal conductivity that is equal to or lower than that of the substrate  110 . 
     The channel-forming material  108  is positioned between the foil surface layer  106  and the substrate  110 . The channel-forming material  108  includes a material corresponding to the composition and/or thermal properties of the substrate  110  and/or has a thermal conductivity that is equal to or less than the thermal conductivity of the substrate  110 . In one embodiment, the channel-forming material  108  includes an electrospark deposition (ESD) coating. The material is the same as the substrate  110  or is any corresponding material to the substrate  110 , for example, having equal or lower thermal conductivity. In another embodiment, the channel-forming material  108  includes a pre-sintered preform (PSP), such as, one or more PSP strips, one or more PSP braze balls, one or more PSP chiclets, one or more PSP foils, one or more other suitable PSP structures, or a combination thereof. 
     In one embodiment, the channel-forming material  108  includes PSP strips containing at least two materials with various mixing percentages. For example, in one embodiment, the first material has a composition, by weight, of between about 8% and about 8.8% chromium, between about 9% and about 11% cobalt, between about 2.8% and about 3.3% tantalum, between about 5.3% and about 5.7% aluminum, up to about 0.02% boron (for example, between about 0.01% and about 0.02% boron), between about 9.5% and about 10.5% tungsten, up to about 0.17% carbon (for example, between about 0.13% and about 0.17% carbon), up to about 1.2% titanium (for example, between about 0.9% and about 1.2% titanium), between about 1.2% and about 1.6% hafnium, and a balance of nickel. In one embodiment, the second material is a braze alloy powder, for example, having a composition, by weight, of between about 13% and about 15% chromium, between about 9% and about 11% cobalt, between about 2.25% and about 2.75% tantalum, between about 3.25% and about 3.74% aluminum, between about 2.5% and about 3% boron, up to about 0.1% yttrium (for example, between about 0.02% and about 0.1% yttrium, and a balance of nickel. Suitable ratios, by weight, for mixing the first material and the second material include, but are not limited to, about 50:50, about 55:45, about 60:40, about 45:55, and about 40:60. 
     In a further embodiment, the channel-forming material  108  has a first channel-forming material  108  and a second channel-forming material  108  in a composition that includes, for example, about 80% a first composition and about 20% a second composition, about 60% a first composition and about 40% a second composition, about 50% a first composition and about 50% a second composition, or any other suitable composition selected for providing desired properties. 
     The channel-forming material  108  is a suitable predetermined geometry or corresponding geometries. Suitable geometries include a substantially planar geometry (for example, a flat plate), a tape-like geometry (for example, a flexible tape capable of being rolled, a flexible tape capable of bending at a right angle without mechanical force, or a flexible tape having a predetermined length), a substantially consistent thickness geometry (for example, about 0.030 inches, about 0.160 inches, or between about 0.020 inches and about 0.080 inches), a rigid tape, a varying thickness geometry (for example, having a thickness of about 0.010 inches in a first region and having a thickness of about 0.020 inches in a second region or having a thickness of about 0.020 inches in a first region and having a thickness of about 0.030 inches in a second region), or combinations thereof. In one embodiment having the first channel-forming material  108  and the second channel-forming material  108 , the first channel-forming material  108  and the second channel-forming material  108  include a substantially identical geometry. In another embodiment, the first channel-forming material  108  and the second channel-forming material  108  have different geometries (for example, the first channel-forming material  108  having thicker regions corresponding to thinner regions in the second channel-forming material  108 ). 
     In one embodiment, a flexible tape is used in addition to or alternative to the channel-forming material  108 , the PSP, and/or the ESD coating. The flexible tape is formed by combining a first composition with a second composition along with a binder and then rolling the mixture to form tape-like or rope-like structures. The flexible tape is capable of being bent to several geometries, includes a predetermined thickness, for example, about 0.020 inches to about 0.125 inches, and is capable of being cut to a predetermined length. 
     The channel-forming material  108  is arranged to form one or more of the channels  112  within the multilayer component  100 . In one embodiment with the PSP, two or more of the PSP structures are arranged such that a region between the PSP structures defines the width of one or more of the channels  112 . Additionally or alternatively, one or more of the PSP structures includes a height defining the height of the one or more channels  112 . In one embodiment, the height of the PSP structure is about 0.015 inches and the width is about 0.015 inches. In one embodiment, the height of the PSP structure is about 0.2 inches and the width is about 0.15 inches. In further embodiments, the height and/or width range between. 
     The channel(s)  112  are positioned in any suitable portion of the multilayer component  100 , for example, within any suitable predetermined distance of an external region, such as those abutting the ceramic coating layer  102 . Suitable predetermined distances include, but are not limited to, about 1 mil, about 5 mils, about 30 mils, between 1 mil and about 5 mils, between about 5 mils and about 30 mils, between about 1 mil and about 30 mils, or any suitable combination, sub-combination, range, or sub-range therein. As shown in  FIG. 1 , in one embodiment, one or more of the channels  112  extend(s) from the foil surface layer  106  to the substrate  110  and, thus, is/are defined by the foil surface layer  106 , the substrate  110 , and the channel-forming material  108 . As shown in  FIG. 2 , in one embodiment, one or more of the channels  112  extend(s) from the foil surface layer  106  into the channel-forming region  108  without extending to the substrate  110  and, thus, is/are defined by the foil surface layer  106  and the channel-forming material  108 . As shown in  FIG. 3 , in one embodiment, one or more of the channels  112  extend(s) from the substrate  110  into the channel-forming region  108  without extending to the foil surface layer  106  and, thus, is/are defined by the substrate  110  and the channel-forming material  108 . As shown in  FIG. 4 , in one embodiment, one or more of the channels  112  is completely defined by the channel-forming region  108  and does not extend to the foil surface layer  106  or the substrate  110 . In some embodiments with the channel at least partially defined by the substrate  110 , dimensions of the channel  112  are at least partially defined by the substrate  110  being machined. In other embodiments, the substrate  110  is not machined. 
     The channel(s)  112  is/are any suitable structure for transporting fluid, such as, air, steam, gaseous fluid, liquid fluid, coolant, other suitable materials capable of transport, or a combination thereof. One suitable structure is a cooling passage. The channel(s)  112  includes a geometry, for example, a cross-sectional profile selected from the group consisting of circular, half-round, triangular, oval-shaped, square-shaped, rectangular, trapezoidal, complex-shaped, crescent-shaped, wave-shaped, and combinations thereof. In one embodiment, the channel(s)  112  is formed between two of the multilayer components  100  positioned adjacently. 
     Referring to  FIG. 5 , a process  500  of fabricating the multilayer component  100  includes applying one or more layers to the foil surface layer  106  (step  501 ) and applying the channel-forming material  108  to at least partially define the channel  112  between the foil surface layer  106  and the substrate  110  (step  503 ) and then brazing them together. In one embodiment, the foil surface layer  106  and the channel-forming material  108  are applied to the substrate  110  by concurrently brazing. 
     Referring to  FIG. 6 , in one embodiment, the applying of the channel-forming material  108  to at least partially define the channel  112  between the foil surface layer  106  and the substrate  110  (step  503 ) includes the channel-forming material  108  being positioned on the substrate  110  (step  602 ). Then, the foil surface layer  106  is positioned on the channel-forming material (step  604 ). Next, the channel-forming material  108  and the foil surface layer  106  are brazed to the substrate (step  606 ). In further embodiments, the bond coat layer  104  is applied to the foil surface layer  106  (step  608 ), then the ceramic coating layer  102  is applied to the bond coat layer  104  (step  610 ). The bond coat layer  104  and/or the ceramic coating layer  102  are applied before or after the brazing of the foil surface layer and the channel-forming material  108  (step  606 ). 
     Referring to  FIG. 7 , in one embodiment, the applying of the channel-forming material  108  to at least partially define the channel  112  between the foil surface layer  106  and the substrate  110  (step  503 ) includes the channel-forming material  108  being positioned on the foil surface layer (step  702 ). Then, the foil surface layer  106  is positioned on the substrate (step  704 ). Next, the channel-forming material  108  and the foil surface layer  106  are brazed to the substrate (step  706 ). In further embodiments, the bond coat layer  104  is applied to the foil surface layer  106  (step  708 ), then the ceramic coating layer  102  is applied to the bond coat layer  104  (step  710 ). The bond coat layer  104  and/or the ceramic coating layer  102  are applied before or after the brazing of the foil surface layer and the channel-forming material  108  (step  706 ). 
     Referring again to  FIGS. 1-4 , in one embodiment, the bond coat layer  104  abuts the foil surface layer  106  and the ceramic coating layer  102 . Additionally or alternatively, the bond coat layer  104  has a thermal conductivity that is less than the foil surface layer  106 . 
     In one embodiment, the ceramic coating layer  102  abuts the bond coat layer  104  and is exposed to the environment of the multilayer component  100 , such as, a hot gas path of a turbine. The ceramic coating layer  102  is any suitable thermally-resistant coating. Suitable coatings include, but are not limited to, thermal barrier coatings (TBCs) and environmental barrier coatings (EBCs). In one embodiment, the TBC includes yttria stabilized zirconia or yttria stabilized borate. Additionally or alternatively, the TBC has a thermal conductivity that is less than the bond coat layer  104 . 
     While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.