Patent Publication Number: US-2016245519-A1

Title: Panel with cooling holes and methods for fabricating same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of and priority to U.S. Provisional Patent Application No. 61/893,107, filed 18 Oct. 2013, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD 
     The present disclosure relates generally to gas turbine engine components, and more particularly, to gas turbine engine components with apertures including effusion cooling holes and methods for fabricating same using additive metal manufacturing techniques. 
     BACKGROUND 
     The temperature in a gas turbine engine can easily exceed the melting temperature of metal components. Cooling holes, often termed film or effusion cooling holes, are employed to provide an air barrier for surfaces exposed to high temperatures. 
     Cooling holes are typically introduced to a component in a separate operation after the component is initially fabricated without them. Such separate operations can lead to added cost and time for manufacture. Typically, cooling holes are introduced subsequently with lasers, electro-discharge machining, or other machining techniques. A drawback of these techniques may be the introduction of laser slags or structural debits in a part due to the laser drilling. 
     In some cases, conventional techniques do not allow for cooling holes to be drilled due to drilling limitations of the techniques utilized, inability to gain access to a drilling location, etc. In addition, conventional drilling techniques may limit the design of parts or components. In other cases, it is not practical to form the cooling holes to provide sufficient cooling with conventional techniques. 
     SUMMARY 
     Disclosed and claimed herein are components and methods for fabricating a component with apertures for fluid passages or effusion cooling holes. According to an embodiment, a method for fabricating a component with apertures includes additive manufacturing initial and additional portions of a component based on data of at least one electronic file representative of the component with the initial and additional portions defining at least a portion of an aperture therethrough, wherein an exit portion of the aperture formed by the additive manufacturing has a wider diameter than that of other portions of the aperture. 
     According to an embodiment, a method for fabricating a component with cooling passages is disclosed. The method includes receiving data including a three-dimensional (3D) representation of a component, and generating a 3D computer-aided design (CAD) file based on the receiving data, wherein the generated 3D CAD file includes fabricating instructions for all features of the component with a plurality of apertures. The method further includes forming an initial portion of the component by an additive metal manufacturing process based on the 3D CAD file containing fabrication instructions for the initial portion of the component, and further forming an additional portion of the component by the additive metal manufacturing process based on the 3D CAD file containing fabrication instructions for the additional portion of the component, wherein the additional portion is formed on the initial portion, and wherein a portion of at least one aperture of the component is formed by the initial portion and the additional portion, and an exit portion of the aperture produced by the additive metal manufacturing process has a wider diameter than that of other portions of the aperture. 
     Another aspect of the disclosure is directed to a gas turbine engine component including a solid metal structure formed by an additive metal manufacturing process, wherein the component includes a plurality of apertures and an exit portion of the apertures produced by the additive metal manufacturing process has a wider diameter than that of other portions of the aperture to efficiently provide an air barrier along surfaces exposed to high temperature. 
     Other aspects, features, and techniques will be apparent to one skilled in the relevant art in view of the following detailed description of the embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features, objects, and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify corresponding features throughout, and wherein: 
         FIG. 1  depicts a method for fabricating a component according to one or more embodiments; 
         FIG. 2  depicts a method for fabricating a component according to one or more embodiments; 
         FIG. 3A  illustrates a graphical representation of a component according to one or more embodiments; and 
         FIGS. 3B-3C  depict cross-sectional views of a component according to one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     In view of the problems with the conventional techniques, it is desirable to manufacture components with cooling passages built from scratch as opposed to subsequently forming cooling passages using a base part. 
     One aspect of the disclosure relates to fabricating a component including one or more cooling passages by an additive metal manufacturing process. As used herein, a component may include, for example, one or more of a combustor panel, a combustor liner, a combustor component, a double walled component, and a gas turbine engine component. 
     According to one aspect of the present disclosure, such component may be fabricated to define one or more cooling passages or apertures using additive manufacturing techniques. Fabrication of the component by an additive process allows for formation of cooling passages during component formation. As such, drilling or machining cooling holes in the component may not be required or needed after a component if formed. 
       FIG. 1  depicts a method for fabricating a component according to one or more embodiments. Process  100  of  FIG. 1  may be initiated by receiving data including a three-dimensional representation of a component at block  105 . The three-dimensional representation may be a computer-aided design (CAD) file of the entire component. Data for the three-dimensional (3D) representation may include the outer dimensional and specifications of the component, as well as the dimensions and shape of one or more cooling passages to be formed within the component. According to one embodiment, the component includes a plurality of cooling passages. 
     At block  110 , an electronic file, e.g., a three-dimensional computer-aided design file (3D CAD file) that contains fabrication instructions may be generated based on the received data for the three-dimensional representation of the component. IN one embodiment, data for the three-dimensional representation of the component may be represented in a particular file format, such as the .stl format. The 3D CAD file includes fabrication instructions for a portion of the component. The step of generating a 3D CAD file includes partitioning the three-dimensional representation into a plurality of layers. By way of example, each layer may correspond to a substantially planar portion (e.g., sliver) of the component. Each data file generated may be associated with a layer. While described as a layer, it should be appreciated that manufacture of the component produces a solid component having a uniform representation of material. 
     The 3D CAD file contains instructions associated with a predetermined thickness for each portion or section of the component. The fabrication instructions may include fabrication commands for forming layers with a thickness in a range of 20 micrometers to 70 micrometers. It should be appreciated that other layer thickness values may be employed. The 3D CAD file may be used to control fabrication of each layer. 
     Process  100  may continue with forming an initial portion of the component based on the 3D CAD file at block  115 . Forming a portion of the component ca be performed by one or more additive metal manufacturing process like “Direct Metal Laser Sintering” (DMLS™), powder-bed manufacturing, or other additive metal fabrication techniques. In one embodiment, the component may be fabricated to include a plurality of cooling passages by using additive metal manufacturing techniques Direct Metal Laser Sintering (DMLS™). DMLS™ may allow for freeform metal fabrication/additive fabrication technology for almost any metal part, including but not limited to nickel and cobalt alloys. According to an embodiment, formation of the component may be based on a print resolution which does not melt, sinter, or weld powered metal in specific area where cooling passages are desired. By way of example, a layer resolution on the order of 20-50 microns may be employed to generate well-defined cooling passages through the component. 
     At block  120 , an additional portion of the component may be formed based on the 3D CAD file containing fabrication instructions for the additional portion of the component. The additional portion is formed on the initial portion. According to an embodiment, a portion of at least one cooling passage of the component is formed by the initial portion and the additional portion. 
     According to one embodiment, the initial portion and the additional portion are formed of the same material, and each cooling passage can be an effusion cooling passage. Cooling passages may be shaped with diameters in the range of 0.5 to 1.5 millimeters. By using the additive manufacturing process, an exit portion of the cooling passage can be formed to have a wider diameter than that of other portions of the cooling passages to enhance the cooling effectiveness. The expanded diameter of the cooling holes at exit portion of the cooling holes can effectively fan or disperse the cooling flow, thereby enhancing the cooling effectiveness, which is not obtainable by conventional manufacturing techniques. Thus, the additive metal manufacturing process allows to add these small local surface features, geometries, and shapes that are not possible with conventional casting tool dies, cores, and machining techniques. 
     Referring to  FIG. 1 , process  100  includes forming additional portions, or layers, of the component to form the component in its entirety at block  120 . Formation of the component may also include formation of complete cooling passages. Process  100  may be employed to form solid components, such as solid metals, composites, alloys, and coated components. Process  100  may additionally include forming a coating layer on the component. The coating layer may be a material different from the material of the additional layer. 
     Referring now to  FIG. 2 , a process  200  is shown for fabricating a component according to one or more embodiments. Process  200  may relate to a process for fabricating a component with cooling passages. 
     Process  200  may include forming an initial portion of a component at block  205  by an additive metal manufacturing technique. The initial portion may be formed based on the 3D CAD file that includes fabricating instructions for the initial portion of the component. Process  200  may continue with forming an additional portion of the component based on the 3D CAD file that includes fabrication instructions for the additional portion of the component. The additional portion is formed onto the initial portion. According to one embodiment, a portion of at least one cooling passage of the component is formed by the initial portion and the additional portion. 
     According to one embodiment, a processing machine or device may determine whether additional layers should be formed at decision block  210 . Additional layers may be formed by an additive metal manufacturing process to form the component with a plurality of cooling passages. Cooling passages may be formed within a plurality of layered metals with a diameter of each cooling holes in the ranges of 0.5 to 1.5 millimeters. In certain embodiments cooling passage diameter at a surface layer may be widened to enhance cooling effectiveness. 
     When additional layers are needed (“YES” path out of decision block  210 ), process  200  can form additional layers at block  205 . When additional layers are not needed (“NO” path out of decision block  210 ), process  200  can finish forming the component at block  215 . Component processing may include heat treatment or other processing step as necessary. 
     Process  200  may employ a DMLS™ machine having a high-powered optic laser to sinter media into a solid. Similarly, process  200  may employ a DMLS™ approach for selective fusing of materials in a granular or powder bed. Fabrication of a component as discussed herein may be inside the build chamber area having a material dispensing platform and a recoater blade to move new powder over the build platform. Fabrication may include fusing metal powder into a solid part by local melting using the focused laser beam. According to one embodiment, components may be built up additively layer by layer, using layers 20 to 50 microns thick. This process allows for highly complex geometries to be created directly from the three-dimensional data of the component within hours and without any tooling. Fabrication as used herein can produce parts with high accuracy and detailed resolution, good surface quality, and excellent mechanical properties without leaving laser slags or other structural debits. 
     Fabrication using DMLS™ in process  200  may allow for the ability to quickly produce a unique part with internal features and passages that could not be cast or otherwise machined. Complex geometries and assemblies with multiple components can be simplified to fewer parts with a more cost effective assembly. 
     According to one embodiment, process  200  may be based on downloading data files for a plurality of layers to an electron beam melting (EBM) machine to form layers in an additive manner. Process  200  may employ EBM for additive manufacturing for metal parts by melting metal powder layer by layer with an electron beam in a vacuum to build up three dimensional parts. 
     Process  200  may employ EMB or other freeform fabrication methods to produce fully dense metal parts directly from metal powder with desired characteristics. 
     According to one embodiment, layers may be melted together by a computer controlled electron beam to build up parts in a vacuum. By way of example, to perform a print, a machine may be configured to read a design from one or more data files and lay down successive layers of powder or sheet material to build the component from a series of cross sections. They layers, which may correspond to the virtual cross sections of a CAD model of the component, are joined or automatically fused to create the final shape according to one or more embodiments. 
     According to one embodiment, process  200  may use EBM technology to obtain the full mechanical properties of components from a pure alloy in powder form. EBM may allow for an improved build rate due to higher energy density and scanning method. 
     According to one embodiment, an EBM process operating at an elevated temperatures, such as between 700 and 1000° C., may be employed to produce components that are virtually free from residual stress and do not require heat treatment after the build. 
       FIG. 3A  depicts a graphical representation of a component according to one or more embodiments. Component  300  may be a component or part of a gas turbine or jet engine, such as an outer casing, inner panel or liner. Cooling passages  302  of component  300  may provide a thin layer of cooling air to insulate the hot side of the component from extreme temperatures. Component  300  may be fabricated by a single-walled or double-wall construction. 
     Component  300  may be part of a double-walled combustor in a gas turbine engine, such as one of a series of segmented panels or liners that form the inner flow path of a combustor. Components may be constructed of high-temperature alloys (e.g., nickel, cobalt) in the form of investment castings or elaborate fabrications using sheet metal. 
       FIGS. 3B-3C  depict cross-sectional views of a component having a cooling passage  302 , before and after a surface layer  304  is formed according to an one or more embodiments. In one embodiment, each cooling passage is an effusion cooling passage of the component, and each cooling passage has a diameter in a range of 0.5 to 1.5 millimeters. Cooling passages  302  may be shaped with an inclination angle and have a wider diameter at a surface layer  304  to enhance cooling effect. 
     According to one embodiment, the cooling passage  302  may be formed by each metal layer and shaped to have a wider diameter at the surface layer  304  to enhance cooling effectiveness. Since the shape and dimensions of the cooling holes are critical to cooling effectiveness, the cooling holes produced by additive manufacturing techniques can have more surface area and shapes so as to further improve cooling effectiveness. As illustrated in  FIG. 3C , a diameter of an exit portion of the cooling holes, disposed to the surface layer  304  and formed by the additive metal manufacturing technique, may be wider than that of the cooling holes in other portions or layers of the component to increase the cooling effectiveness, according to one or more embodiments. 
     While this disclosure has been particularly shown and described with references to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the claimed embodiments.