BACKGROUND OF THE INVENTION

[0001] The present invention relates to hole formation in turbine components and more specifically to the formation of a porous exit region at the discharge end of a film cooling hole using an additive manufacturing process.

[0002] Airfoils in a turbine engine often include cooling holes for discharging a film of cooling air along the outer surface of the airfoil to affect film cooling. These may be referred to as "film cooling holes" or "film holes."

[0003] Generally, cooling holes extend through a wall in an aircraft component from an entry end to an exit end. In some cooling holes, the exit end is configured as a generally conical diffuser and is positioned in a surface of an aircraft component that has a leading edge and a trailing edge. It is sometimes desirable that instead of being conical, the diffuser section of a cooling hole be configured such that flow through the cooling hole is distributed into many small flow paths by a porous exit region.

[0004] Conventional methods for forming film cooling holes include casting and machining. One problem with film holes produced by conventional methods is that it is difficult to create porous exits with such methods.

BRIEF DESCRIPTION OF THE INVENTION

[0005] This need is addressed by a method of forming a porous exit region near the discharge end of a film hole using an additive manufacturing process.

[0006] According to one aspect of the present invention, there is provided a method of forming a cooling hole structure on a turbine component having a component wall with inner and outer surfaces, wherein a cooling hole passes through the component wall and fluidly connects the inner surface and the outer surface. The method includes forming a recess communicating with the hole and the outer surface; and using an additive manufacturing process to form a porous structure in the recess.

[0007] According to another aspect of the present invention, there is provided a method of forming a porous exit region at the discharge end of a cooling hole on a turbine component having a component wall with inner and outer surfaces, wherein the cooling hole passes through the component wall and fluidly connects the inner surface and the outer surface. The method includes the steps of: removing a portion of a discharge end of the cooling hole so as to form a recess positioned between the outer surface and the cooling hole; and using an additive manufacturing process to build an exit region that extends away from a surface of the recess toward the outer surface.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The invention may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which:

[0009] FIG. 1 is a perspective view of a turbine blade for inclusion in an aircraft engine wherein a wall of the turbine blade includes multiple film holes for cooling the wall;

[0010] FIG. 2 is a cross-sectional view of a portion of the turbine blades shown in FIG. 1 taken at line 2-2 showing a porous exit region formed in accordance with a method for manufacturing the film hole by additive manufacturing;

[0011] FIG. 3 is a plan view of a portion of the turbine blade shown in FIG. 1 showing a film hole having a porous exit region;

[0012] FIG. 4 is a cross-sectional view of a portion of a wall section blank generated during one step of the manufacturing process of the turbine blade of FIG. 1 taken along line 2 - 2 in FIG. 1;

[0013] FIG. 5 is a cross-sectional view of the wall section of FIG. 4, showing a bore formed therethrough;

[0014] FIG. 6 is a cross-sectional view of a portion of the turbine component of FIG. 5, showing that material has been removed from the turbine component near the one side of one end of the hole of the wall section such that a recess is defined;

[0015] FIG. 7 is a cross-sectional view of a portion of the wall section shown in FIG. 6 wherein a section of the hole near the recess has been blocked;

[0016] FIG. 8 is a cross-sectional view of a portion of the wall section of FIG. 7, showing powder being applied to the wall section;

[0017] FIG. 9 is a cross-sectional view of a portion of the wall section of FIG. 8, showing powder being fused;

[0018] FIG. 10 is a cross-sectional view of a portion of the wall section of FIG. 9, showing new material that has been added to the recess so as to define a porous exit region;

[0019] FIG. 11 is a cross-sectional view of the wall section FIG. 11 where in the unfused powder has been removed;

[0020] FIG. 12 is a cross-sectional view of the wall section shown in FIG. 12 wherein the blocking material has been removed and porous exit region manufactured in accordance with the method described below is shown;

[0021] FIG. 13 is a cross-sectional view of a portion of the turbine blades shown in FIG. 1 taken at line 2-2 showing another porous exit region formed in accordance with a method for manufacturing the film hole by additive manufacturing; and

[0022] FIG. 14 is a cross-sectional view of a portion of the turbine blades shown in FIG. 1 taken at line 2-2 showing yet another porous exit region formed in accordance with a method for manufacturing the film hole by additive manufacturing.

DETAILED DESCRIPTION OF THE INVENTION

[0023] Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views, FIG. 1 illustrates an exemplary turbine blade 10. The turbine blade 10 includes a conventional dovetail 12, which may have any suitable form including tangs that engage complementary tangs of a dovetail slot in a rotor disk (not shown) for radially retaining the blade 10 to the disk as it rotates during operation. A blade shank 14 extends radially upwardly from the dovetail 12 and terminates in a platform 16 that projects laterally outwardly from and surrounds the shank 14. A hollow airfoil 18 extends radially outwardly from the platform 16 and into the hot gas stream. The airfoil has a root 19 at the junction of the platform 16 and the airfoil 18, and a tip 22 at its radially outer end. The airfoil 18 has a concave pressure side wall 24 and a convex suction side wall 26 joined together at a leading edge 28 and at a trailing edge 31. [0024] The airfoil 18 may take any configuration suitable for extracting energy from the hot gas stream and causing rotation of the rotor disk. The airfoil 18 may incorporate a plurality of trailing edge bleed slots 32 on the pressure side wall 24 of the airfoil 18, or it may incorporate a plurality of trailing edge cooling holes (not shown). The tip 22 of the airfoil 18 is closed off by a tip cap 34 which may be integral to the airfoil 18 or separately formed and attached to the airfoil 18. An upstanding squealer tip 36 extends radially outwardly from the tip cap 34 and is disposed in close proximity to a stationary shroud (not shown) in the assembled engine, in order to minimize airflow losses past the tip 22. The squealer tip 36 comprises a suction side tip wall 38 disposed in a spaced-apart relationship to a pressure side tip wall 39. The tip walls 39 and 38 are integral to the airfoil 18 and form extensions of the pressure and suction side walls 24 and 26, respectively. The outer surfaces of the pressure and suction side tip walls 38 and 39 respectively form continuous surfaces with the outer surfaces of the pressure and suction side walls 24 and 26. A plurality of film cooling holes 100 pass through the exterior walls of the airfoil 18. The film cooling holes 100 communicate with an interior (not shown) of the airfoil 18, which may include a complex arrangement of cooling passageways defined by internal walls. By way of example and not limitation, the cooling passageways can include one of the following characteristics serpentine, intertwined, intersecting, non-intersecting, and a combination thereof. It should be appreciated that airfoil 18 may be made from a material such as a nickel- or cobalt- based alloy having good high-temperature creep resistance, known conventionally as

"superalloys."

[0025] FIG. 2 illustrates one of the film cooling holes 100 in more detail. The film hole 100 extends from an interior surface 54 of the pressure side wall 24 to an outer surface 56 of the pressure side wall 24. The film hole 100 includes an entry section 104 and an exit section 108. The exit section 108 includes a porous exit region 160. Porous exit region 160 is an example of a porous structure. The entry section 104 is often referred to as a "metering section" and is generally round. The entry section 104 and the exit section 108 meet at a transition area 112. In this regard, the entry section 104 extends from interior surface 54 to the transition area 112.

[0026] The exit region 160 has an entry side 162 and an exit side 164. The entry side 162 is positioned such that it is fluidly connected through the entry section 104 of the film hole 100 to the interior surface 54. The exit side of exit region 160 is fluidly connected to the outer surface 56 of the sidewall 24. The porosity of exit region 160 is such that film hole 100 is fluidly connected to outer surface 56 of sidewall 24. In this regard, exit region 160 defines many pathways for a cooling fluid to pass through exit region 160 and exit region 160 is configured such that it is analogous to an open cell foam with regards to pathways formed therethrough. It should be appreciated that such "open cell foam" structures could also include areas with one or more closed cells. Such "open cell foam" structures could also include solid areas. Such structural variations in the composition of exit region 160 are not necessarily uniformly distributed throughout exit region 160.

[0027] The exit section 108 may include an increasing flow area from the transition area 112 to the outer surface 56. As seen in FIGS. 3, the dimensions of the exit section 108 increase in the lateral direction along the direction of flow. This type of structure is often referred to as a "diffuser section" and may take on various shapes such as conical, quadrilateral, or multifaceted. As shown in figures 2 and three, exit region 160 extends from transition area 112 to the outer surface 56, i.e., exit region 160 fills the "diffuser section." It should be appreciated that in some embodiments, exit region 160 occupies only a portion of the "diffuser section."

[0028] A method of manufacturing a complex film hole such as film hole 100 will now be described. First, a wall section 120 as shown in FIG. 4 is provided. The wall section 120 is generally representative of the wall section of any turbine component, of any shape such as flat, convex, concave, and/or complexly curved. Such as the suction side wall 26 described above, and includes opposed inner and outer surfaces 154 and 156 respectively. It should be understood that the providing step of the wall section 120 includes but is not limited to manufacturing of the wall section 120 or obtaining a pre-manufactured wall section 120. Methods of manufacturing the wall section 120 include but are not limited to those conventionally known such as casting, machining, and a combination thereof. Secondly according to the illustrated embodiment, a bore 122 as shown in FIG. 5 is formed through the wall section 120. It should be appreciated that the bore 122 is formed according to conventional means such as machining, drilling. Additionally, the bore 122 can be formed during the formation of the wall section 120 by a method such as casting.

[0029] Bore 122 extends from a first end 124 to a second end 126. Referring to FIG. 6, the next step is removing a portion of the wall section 120 that defines the second end 126 of the bore

122. In this manner, recess 132 is formed at second end 126 of the tube and prepared to receive additional material. Recess 132 is in fluid communication with surface 156 and bore 122. Recess

132 is defined by a surface 131. By way of example and not limitation, recess 132 can be formed by one of the following processes; milling, casting, drilling, machining, and a combination thereof. . It should be appreciated that recess 132 can be in the form of a channel that intersects multiple bores 122. In this regard, in an additive manufacturing process can form multiple exit regions at multiple film holes during a single process implementation.

[0030] Following the steps of preparing bore 122 for receiving additional material near the second end 126, steps related to reconfiguring second end 126 of bore 122 using an additive manufacturing process are implemented.

[0031] The additive manufacturing process can optionally begin with a step of blocking bore 122 with a plug 134 as shown in FIG. 7. It should be appreciated that blocking of bore 122 is optional and that the additive manufacturing process can begin with a step of positioning wall section 120 or it can begin with the steps of applying an adhesive and/or applying powder. In the illustrated embodiment, plug 134 is positioned where bore 122 engages recess 132 and is configured such that the powder from subsequent additive manufacturing steps is prevented from entering bore 122. It should be appreciated that by way of example and not limitation, bore 122 can be blocked utilizing at least one of the following materials: a polymer, unfused powder, a wax or other material, and a combination thereof. It should be appreciated that these materials are chosen such that they can be removed from the finished part by solvation, mechanical means, heat, or a combination thereof.

[0032] As shown in FIG. 8, a layer of powder P for example, metallic, ceramic, and/or organic powder is deposited into the recess 132. As a non-limiting example, the thickness of the powder layer may be about 10 micrometers (0.0004 in.).

[0033] The powder P may be applied by dropping or spraying the powder over the recess 132, or by dipping the wall section 120 in powder. Powder application may optionally be followed by brushing, scraping, blowing, or shaking as required to remove excess powder, for example to obtain a uniform layer. It is noted that the powder application process does not require a conventional powder bed or planar work surface, and the part may be supported by any desired means, such as a simple worktable, clamp, or fixture.

[0034] As can be seen in figure 9, once the powder P is deposited to the predetermined level in recess 132 of the wall section 120, a directed energy source B (such as a laser or electron beam) is used to melt a layer of the structure being built. The directed energy source emits a beam and a beam steering apparatus is used to steer the beam over the exposed powder surface in an appropriate pattern. The exposed layer of the powder is heated by the beam to a temperature allowing it to melt, flow, and consolidate and fuse to or adhere to substrate with which it is in contact. In this manner, the metallic particles that made up powder P now exist as part of the wall section 120. Directed energy source B can be used to fuse powder P at any depth with in recess 132 or bore 122 as long as powder P is positioned within the line of sight of energy source B. This step may be referred to as fusing the powder. Unfused powder can be removed at this stage prior to the next cycle of applying an adhesive, applying powder, and fusing the powder. However, in the illustrated embodiment, unfused powder that is not removed in each step remains in place. In this regard the unfused powder can operate to support powder of the next layer.

[0035] This cycle of depositing powder and then directed energy melting the powder is repeated until the entire component is complete. As shown in figure 10, new material 152 is built up gradually as portions of layer after layer are fused. In this manner, and exit region 160 is formed as recess 132 is gradually filled with powder P. When the component is complete, as shown in FIGS. 11, 12, and 13, new material 152 is positioned in recess 132 and defines film hole 200. Film hole 200 includes an entry section 204, and exit section 208, the transition section 212. Film hole 200 is at least partially filled with filler F. By way of example and not limitation, filler F includes one of the following: unfused powder P, adhesive, blocking material 134, and a combination thereof. In a finishing step filler F and any other unfused and unbonded powder or adhesive from previous steps can be removed in one cleaning step. Alternatively, two cleaning steps could be used. One to remove loose filler F material by air pressure or air jet resulting in structure shown in FIG. 12. And a second for removing plug 134 by a method such as dissolving with solvents, using heat to disperse, or the like which results in the structure shown in FIG. 13. It should be noted that the structure shown in FIG. 13 is substantially the same as that shown in FIG. 2 except new material added via the present method is highlighted.

[0036] Figures 13 and 14 show alternative embodiments that provide film hole 300 and film hole 400 respectively. Exit region 360 of film hole 300 includes a fanned array of tubes 364. Thus, one acceptable shape of the passage is as tubular. In contrast, the many pathways could be irregular tubular shapes that define intertwining serpentine paths as included in exit region 460 of film hole 400. Porous exit regions 360 and 460 are examples of a porous structure.

[0037] The process described is merely one example of an additive manufacturing process.

"Additive manufacturing" is a term used herein to describe a process which involves layer-by- layer construction or additive fabrication (as opposed to material removal as with conventional machining processes). Such processes may also be referred to as "rapid manufacturing processes". Additive manufacturing processes include, but are not limited to: Direct Metal Laser Melting (DMLM), Laser Net Shape Manufacturing (LNSM), electron beam sintering, Selective Laser Sintering (SLS), 3D printing, such as by inkjets and laserjets, Stereolithography (SLA), Electron Beam Melting (EBM), Laser Engineered Net Shaping (LENS), and Direct Metal Deposition (DMD).

[0038] The process described herein has several advantages over the prior art. The additive manufacturing process is far more flexible as to shape, general configuration, and complexity of film holes that can be manufactured. In addition, it is believed that the additive manufacturing process allows lower heat generation during formation of film holes and thus less deformation of crystalline structure and exit region shape and configuration.

[0039] The method described above provides a means for creating porous exit regions in film holes or other similar orifices of complex exit shaping, without the need for conventional machining processes such as drilling, EDM forming, or laser trepanning. It avoids the complexities of such conventional methods by permitting a complex porous exit region to be formed in a single process. This will permit both flexibility and cost reductions in making complex cooled components. This in turn has the potential of increasing cooling efficiency of turbine components and lowering engine specific fuel consumption ("SFC").

[0040] The foregoing has described an apparatus and method for additive manufacturing of shaped exit holes of film holes in turbine blades and more specifically, porous exit regions in film hole exits. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

[0041] Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0042] The invention is not restricted to the details of the foregoing embodiment s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying potential points of novelty, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.