Method and apparatus for repairing an object protruding above a powder bed using a split wiper

Abstract

A method for repairing a component using an additive manufacturing process is proposed. The method includes: immersing the component into a powder bed such that a portion of the component to be repaired is flush with the surface of the powder bed and a protruding portion of the component protrudes above the surface of the powder bed; positioning a split wiper including a first wiper section and a second wiper section at the surface in the powder bed; advancing a quantity of powder by translating the first wiper section and the second wiper section across the surface of the powder bed; and directing a laser beam across the surface to fuse powder particles of the powder bed to the underlying substrate to form a layer of the component. Each of the first wiper section and the second wiper section follows a different contour of the protruding portion at the surface.

Description

[0001] Background

[0002] Aspects of the present disclosure generally relate to additive manufacturing (AM), and more particularly to powder bed fusion processes such as selective laser melting (SLM) and selective laser sintering (SLS). In particular, the present disclosure relates to the manufacture and repair of components having portions that protrude above a powder bed.

[0003] Powder bed fusion processes such as selective laser melting (SLM) and selective laser sintering (SLS) include starting a layer-by-layer deposition of powder at a build plate and then laser melting / laser sintering each layer. The wiper used in SLM and SLS is an element that extends across the powder bed and moves in a linear (X-Y axis) manner to distribute and level a new powder layer prior to the scanning process of an energy beam such as a laser beam or an electron beam. Such a wiper typically has a structure similar to that of an automotive windshield wiper. Selective laser manufacturing is limited to builds starting from a flat build plate. Selective laser repair is limited to builds starting on a component submerged below the top of the powder bed. Any solid protrusions above the powder bed are not allowed because these obstacles would impede the sweeping action of the wiper extending across the bed. Summary of the Invention

[0004] In one embodiment, a method of repairing a component using an additive manufacturing process includes: immersing the component in a powder bed such that a portion of the component to be repaired is flush with the surface of the powder bed and a protruding portion of the component protrudes above the surface of the powder bed; positioning a split wiper including a first wiper segment and a second wiper segment at the surface in the powder bed; advancing a quantity of powder by translating the first wiper segment and the second wiper segment across the surface of the powder bed and directing a laser beam across the surface of the powder bed to fuse powder particles of the powder bed to a substrate therebelow to form a layer of the component. Each of the first wiper segment and the second wiper segment follows a different contour of the protruding portion at the surface of the powder bed.

[0005] In another embodiment, a system for repairing a component using a powder bed fusion additive manufacturing process, the system comprising: a container containing a powder bed having a component, wherein a portion of the component to be repaired is immersed at a location defined by a recess in the component at the surface of the powder bed, and a protruding portion of the component protrudes above the powder bed; a split wiper including a first wiper segment and a second wiper segment; and an energy beam source operably configured to direct laser energy toward the powder bed to fuse an amount of powder into an additional material layer on the component. The first wiper segment and the second wiper segment are each configured to follow a different contour of the protruding portion at the surface of the powder bed. The first wiper segment advances an amount of powder into the additional material layer on the component.

[0006] In another embodiment, a method of additive manufacturing a component, the method comprising positioning a first wiper segment at a first surface of the component and positioning a second wiper segment at a second surface of the component, wherein the first surface and the second surface are at different heights. The method further comprises operating augers in front of each of the first wiper segment and the second wiper segment in a translation direction, each auger including a powder feeder. Each auger is advanced with the first wiper segment and the second wiper segment by translating across the first surface and the second surface, respectively. Each auger transports powder along the length of the auger such that an amount of powder is distributed on the respective surface. An energy beam is directed across the first surface and the second surface to fuse the powder particles to the component to form a layer of the component. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] To facilitate the discussion of readily identifying any particular element or action, one or more of the most significant digits in the reference numerals refer to the figure number in which the element is first introduced.

[0008] Figure 1 is a top view of a turbine blade.

[0009] Figure 2 is a side view of the turbine blade.

[0010] Figure 3 is Figure 1 a top view of the turbine blade having a damaged portion.

[0011] Figure 4 is Figure 1 a side view of the turbine blade having a damaged portion.

[0012] Figure 5 is Figure 1 and Figure 2Top view of a turbine blade that utilizes a split wiper.

[0013] Figure 6 Is Figure 1 And Figure 2 Side view of a turbine blade that utilizes a split wiper.

[0014] Figure 7 Is a side view and a cross-sectional view of a wiper segment with a support.

[0015] Figure 8 Is a top view of a turbine blade during a split wiper translation step.

[0016] Figure 9 Is a top view of a turbine blade during another split wiper translation step.

[0017] Figure 10 Is a top view of a turbine blade during another split wiper translation step.

[0018] Figure 11 Is a top view of a turbine blade that utilizes an auger wiper to provide lateral powder conveyance.

[0019] Figure 12 Is a top view of a turbine blade that utilizes an auger ahead of the wiper blade to provide lateral powder conveyance.

[0020] Figure 13 Is a side view of an auger that conveys powder, which is located ahead of a wiper blade that levels the powder.

[0021] Figure 14 Is a side view of a turbine blade that utilizes a split wiper at different heights.

[0022] Figure 15 Is a side view of an auger that utilizes a powder hopper. Detailed Description

[0023] Figure 1 And Figure 2 Illustrate a top view and a side view of a conventional turbine blade. The turbine blade 100 includes an airfoil 102, a platform 104, and a root 106. The root 106 can be configured to be slidably received into a corresponding axial groove in a rotor disk. The root 106 and the axial groove can be configured for an interlocking engagement. The plane of the platform 104 can be generally perpendicular to the extension of the blade airfoil 102.

[0024] Many of the components to be repaired have complex shapes and areas to be repaired that are inaccessible when the rest of the component is fully immersed. An example of such a challenge is repairing the platform of a gas turbine blade. Figure 3 and Figure 4 illustrate Figure 1 and Figure 2 top and side views of a turbine blade 100 having a portion with a damaged portion 206 located on a blade platform 104. Repairing components using SLM and SLS involves immersing the component in a powder bed. However, in order to repair the damaged portion 206 of the platform 104 using SLM or SLS, the blade airfoil 102 cannot be fully immersed in the powder bed 204. As can be seen in Figure 3 and Figure 4 , the wiper 202 arm will not be able to translate across the plane of the platform 104 because the protruding airfoil 102 is an obstacle 208 to such movement.

[0025] The present disclosure teaches a solution for powder bed processing when a component protrudes above the powder bed. Figure 5 illustrate Figures 1 to 4 a turbine blade 100 that utilizes a split wiper 302 for an additive manufacturing process such as SLM or SLS. The turbine blade 100 is immersed in the powder bed 204 such that a portion 306 of the component that includes the damaged portion 206 - in this example, portion 306 is the platform 104 of the turbine blade - is at the surface of the powder bed 204 and a protruding portion 308 of the component, such as the illustrated airfoil 102, protrudes above the powder bed 204. A container that includes the powder bed 204 can be provided. The damaged portion 206 can include a cavity 304 located in portion 306 of the turbine blade 100 that needs to be repaired, such as by adding a new layer of material to the turbine blade 100 via a laser powder bed fusion process. The cavity 304 can have been previously formed by machining, for example, to remove a damaged portion 206 such as a crack.

[0026] In an embodiment, a split wiper 302 can be provided. The split wiper 302 can include a first wiper segment 312 and a second wiper segment 310. The first wiper segment 312 and the second wiper segment 310 can be positioned in the powder bed 204 in a manner that they project from opposite sides of the edge of the powder bed 204 and are in adjacent contact. In one configuration, each of the first wiper segment 312 and the second wiper segment 310 includes a wiper blade having an end surface 314 and a side surface 316, such that the end surface 314 and the side surface 316 cooperate to define an acute angle (θ) therebetween. The acute angle (θ) can vary to best suit the geometries of different components. For example, the angle (θ) of the wiper blade can be configured to accommodate the angle of the final edge 702 of the recess 304 to be repaired (see Figure 10 ). The wiper blade is configured to push and level a certain amount of powder in the powder bed 204.

[0027] The wiper blades of the first wiper segment 312 and the second wiper segment 310 for powder bed leveling may need to be supported to maintain proper contact with the intended surface. Thus, in one configuration, the first wiper segment 312 and / or the second wiper segment 310 includes a rigid cantilever support structure 402 and a wiper blade 404 that extends along the axis of the wiper segment 312 to keep the wiper blade 404 level with the intended processing plane in the powder bed 204. In an embodiment, as shown in the cross-sectional view on the left side of Figure 7 , that is, the cross-section taken along the line 7-7 of Figure 5 , the support structure 402 includes a C-channel shape that provides sufficient reinforcement in the X-Y plane (powder plane). In the side view in Figure 7 , as shown on the right side of Figure 7 , the C-channel support structure 402 includes a bracket between the top and the bottom of the inner edge of the C-channel support structure 402 to assist in keeping the wiper blade 404 level over the cantilever length.

[0028] Figure 8Illustrates the split wiper translation steps in an exemplary AM powder bed fusion process. Each of the first wiper segment 312 and the second wiper segment 310 advances powder by translating across the powder bed 204. In the illustrated example, as indicated by the arrow, the movement is from left to right. The second wiper segment 310 and the first wiper segment 312 each follow a different contour of the component. In this case, the second wiper segment 310 is laterally positioned to follow the convex contour of the blade airfoil 102. The first wiper segment 312 is positioned to follow the concave contour of the blade airfoil 102. The illustrated example shows the first wiper segment 312 approaching the portion of the platform 104 to be repaired defined by the recess 304.

[0029] In some embodiments, advancing the powder by the wiper segment may include an oscillatory movement of the wiper segment, i.e., an axial back-and-forth movement as indicated by the double arrow, to help enhance powder filling and distribution. Additionally, in an embodiment, each wiper segment may vibrate along its axis, parallel and / or perpendicular to the translation direction of the wiper segment across the powder bed 204, to enhance powder distribution.

[0030] Figure 9 Illustrates another split wiper translation step in an exemplary AM powder bed fusion process. The second wiper segment 310 continues to follow the convex blade profile. The first wiper segment 312 may push a certain amount of powder into the recess 304 in order to level the powder in the recess 304. However, in order to level the powder in the recess 304, the first wiper segment 312 needs to be lowered by a predetermined depth. Thus, in an embodiment, the first wiper segment 312 is lowered by a predetermined depth at the edge of the recess 304. The predetermined depth may depend on the depth of the recess 304 and the desired layer thickness of the layer to be added to the component. Typically, the added material layer of a component produced by the powder bed fusion process is about 20 microns. In Figure 9 the illustrated embodiment, the lowering of the first wiper segment 312 occurs at the position where the left edge 602 of the recess 304 is encountered. Once lowered, the first wiper segment 312 advances the powder across the width of the recess 304.

[0031] Figure 10 Illustrates another translation step of a split wiper in an exemplary AM powder bed fusion process. In this step, the second wiper segment 310 begins to bypass the leading edge of the airfoil 102. The first wiper segment 312 is positioned away from the recess 304. As shown, the angled contour of the wiper blade helps to push the powder towards the final edge 702 of the recess 304 in the wiper translation direction.

[0032] In a final step, once the split wiper has completed its translation across the powder bed 204, an energy beam can be directed across the surface of the powder bed 204 to fuse the powder particles of the powder bed 204 together and to the underlying substrate to form a layer of the platform 104. In Figures 1 to 10 the example process shown, the energy beam can be directed across the width of the recess 304 to form a layer of the platform 104 within the recess 304. These steps can be repeated a number of times until the part is repaired. In Figures 1 to 10 the example process shown, when the last layer reaches the plane of the platform 104, the AM process can be completed.

[0033] In an embodiment, the translation of each of the first wiper segment 312 and the second wiper segment 310 can be controlled separately by a position controller. The position controller can be pre-programmed such that each wiper segment follows a different profile of the geometry of the protrusion at the surface of the powder bed 204. Pre-programming the geometry of the part may not be feasible for every part, especially for the repair of parts with uncertain geometry.

[0034] In some embodiments, the position controller can employ a tracking or sensing method. For example, in one embodiment, a mechanical contact probe, such as an extensometer, can be positioned ahead of the first wiper segment 312 to provide the direction of protrusion of the first wiper segment 312 when the first wiper segment 312 reaches the probe position. In another embodiment, electrical contact can be utilized to guide the protrusion of the first wiper segment. The conductivity of the part and the first wiper segment 312 provides a circuit for regulating the wiper protrusion. Electrical contact at the end of the first wiper segment 312 can provide information to guide the protrusion of the first wiper segment to follow the profile of the protrusion of the part. One method involves incremental protrusion of the first wiper segment 312 until such incremental protrusion results in the closing of the circuit through the first wiper segment 312 and the part, and then retracting the first wiper segment 312 until an open circuit is achieved. The protrusion information collected provides the adjustment direction of the first wiper segment 312. A similar method involves applying a voltage between the part and the first wiper segment 312. When a short circuit is detected, position information is provided for wiper tracking of the profile of the part. In another embodiment, the tracking and sensing method utilizes optical sensing, which can include pre-process vision tracking or in-process vision tracking, such as laser vision tracking. Optical triangulation can provide very accurate part position to guide the protrusion of the first wiper segment. Similar positioning methods can also be applied to guide the protrusion of the second wiper segment.

[0035] In as Figure 11In the structure shown, the first wiper segment 312 includes an auger 812. The auger 812 can be generally cylindrical (e.g., a screw) having a helical convolution on its surface. The challenge of simply using a wiper blade to push powder into the cavity 304 is to deliver the powder to remote areas of the cavity and to deliver the powder evenly across the cavity 304. Thus, the mechanism to achieve such delivery can be an auger. Compared to a wiper blade, the auger can deliver powder along its length into the cavity 304 such that the powder is distributed generally evenly throughout the cavity 304. Rotation of the auger partially immersed in the powder bed 204 can convey the powder towards the end of the auger and into inaccessible portions of the cavity 304. Alternatively, the wiper blade can include serrations along its length to enhance powder conveyance perpendicular to the translation direction. The circular sweep of the wiper blade will further enhance this effect.

[0036] However, by using only an auger without a wiper blade, the powder being pushed may not be leveled accurately. Thus, in Figure 12 In another structure shown, when the first wiper segment 312 includes a wiper blade, the auger 902 precedes the movement of the first wiper segment 312. The auger 902 can be partially immersed in the powder bed and is located in front of the wiper blade in the cavity 304 in the translation direction, causing the auger 902 to operate to convey powder along its length such that the powder is distributed throughout the cavity 304.

[0037] Figure 13 A side view of the auger 902 preceding the first wiper segment 312 is shown, with the first wiper segment 312 implemented as a wiper blade in the cavity 304. The auger 902 conveys and distributes the powder throughout the cavity 304 along its length, while the wiper blade follows closely to level the distributed powder.

[0038] Figure 14Illustrated is an embodiment having a split wiper with a first wiper section 312 and a second wiper section 310 that advance and level powder at different heights of an exemplary turbine blade 100. Thus, the first wiper section 312 and the second wiper section 310 are located at surfaces at different heights. In the translation direction indicated by the arrows in the figure, a auger 902 is in front of each of the first wiper section 312 and the second wiper section 310, and the auger 902 is configured to convey powder along its axis. The first wiper section 312 and the second wiper section 310 each follow the corresponding auger 902 in the translation direction to convey the powder to the corresponding surface. One energy beam 1100 or multiple energy beams can be optically directed at the corresponding surface to fuse the powder to the underlying surface, thereby forming a layer of the turbine blade on each surface. For this embodiment, powders with different compositions can be utilized on different surfaces to meet local properties, such as, for example, corrosion resistance, strength, ductility, or erosion resistance.

[0039] Figure 15 A side view of the auger 902 is illustrated, and the auger 902 includes an attached powder feeder for distributing powder to a surface such as Figure 14 the surface shown in. The powder feeder can be in the form of an attached powder hopper 1200 that distributes powder from perforations 1204 in a sleeve 1202 of the auger 902 to the corresponding surface.

[0040] Although Figures 1 to 15 the example shown in illustrates a component being repaired, the AM process using a split wiper described can also be beneficial for components built from scratch, especially in embodiments where the component may include different process parameters (such as different powder layer thicknesses). For example, various vertical extensions of the component can be processed in different steps without the existing extensions interfering with previously built extensions. In another example, a split wiper can be used in an AM process where the component has portions that require different powder alloys or utilize different build directions. For this example, to change the powder alloy or change the orientation of the component, the component can be removed from the powder bed. Similarly, the existing extensions will not interfere with additional processing.

[0041] A split wiper having at least two wiper sections allows components with complex shapes that need repair to utilize a powder bed fusion additive manufacturing process. The powder bed fusion process has the advantage of very low heat input and is a very precise process for producing components with complex details. Each split wiper section can follow different contours of the following component: the component has portions that protrude at different heights above the powder bed or within different powder beds.

[0042] Although the exemplary embodiments of the present disclosure have been described in detail, those skilled in the art will understand that various changes, alternatives, variations, and improvements disclosed herein can be made without departing from the spirit and scope of the broadest form of the present disclosure.

[0043] No description in this application should be construed as implying that any particular element, step, act, or function is an essential element that must be included within the scope of the claims: the scope of the patent subject matter is defined only by the allowed claims. Additionally, these claims are not intended to invoke the apparatus-plus-function claim construction unless the exact phrase "means for" is followed by a participle.

Claims

1. A method of using an additive manufacturing process to repair a component, the method comprising: immersing the component into a powder bed such that a portion of the component to be repaired is flush with a surface of the powder bed and a protruding portion of the component protrudes above the surface of the powder bed; positioning a split wiper including a first wiper section and a second wiper section at the surface in the powder bed; advancing an amount of powder by translating the first wiper section and the second wiper section across the surface of the powder bed, wherein each of the first wiper section and the second wiper section follows a different contour of the protruding portion at the surface of the powder bed; and directing an energy beam across the surface of the powder bed to fuse powder particles of the powder bed to a substrate therebelow to form a layer of the component.

2. The method according to claim 1, wherein The first wiper section includes a wiper blade, the wiper blade including an end surface and a side surface, the end surface forming an acute angle with the side surface.

3. The method according to claim 2, wherein Pushing the amount of powder into a recess defined in the component for the portion to be repaired by the first wiper section.

4. The method according to claim 3, wherein, The advancing further includes lowering the wiper blade into the recess at a predetermined depth at an edge of the recess to advance the powder across a width of the recess.

5. The method according to claim 3, further comprising advancing an auger partially immersed in the powder bed and operating the auger to convey powder along a length of the auger before translating the wiper blade in the recess such that the powder is distributed throughout the recess.

6. The method according to claim 1, wherein The advancing further includes conveying powder into a recess defined in the component for the portion to be repaired by the first wiper section, wherein the first wiper section includes an auger partially immersed in the powder bed, and wherein the auger conveys powder along a length of the auger into the recess such that the powder is distributed throughout the recess.

7. The method according to claim 1, wherein The advancing further includes oscillating the first wiper section in a direction along an axis of the first wiper section.

8. The method according to claim 1, further comprising controlling translations of the first wiper section and the second wiper section by a controller such that each wiper section follows a different contour of the protruding portion at the surface of the powder bed.

9. The method according to claim 8, wherein, The controlling includes pre-programming the controller to include a contour geometry of the protruding portion at the surface such that each of the first wiper section and the second wiper section follows a different contour of the protruding portion.

10. The method according to claim 8, wherein, The controlling includes using tracking and sensing methods to control translations of the first wiper section and the second wiper section such that each wiper section follows a different contour of the protruding portion of the component.

11. The method according to claim 1 further comprises vibrating the first wiper segment along its axis and parallel or perpendicular to the direction of translation across the powder bed for powder distribution.

12. The method according to claim 1, wherein, The additive manufacturing process is a laser powder bed fusion process.

13. The method according to claim 1, wherein, The component is a turbine blade.

14. A system for repairing a component using a powder bed fusion additive manufacturing process, comprising: A container containing a powder bed with the component, wherein: the portion of the component to be repaired is immersed at a position defined by a recess in the component at the surface of the powder bed, and the protruding portion of the component protrudes above the powder bed; A split wiper including a first wiper segment and a second wiper segment, each of the first wiper segment and the second wiper segment being configured to follow a different contour of the protruding portion at the surface of the powder bed, wherein the first wiper segment advances a quantity of powder into the recess of the component; An energy beam source operably configured to direct an energy beam towards the powder bed to fuse the quantity of powder into an additional material layer on the component; and A controller configured to control the translation of the first wiper segment and the second wiper segment such that each of the wiper segments follows a different contour of the protruding portion respectively.

15. The system according to claim 14, wherein The first wiper segment includes a wiper blade having an end surface that mates with a side surface to define an acute angle between the end surface and the side surface, and the first wiper segment advances and levels the powder of the powder bed.

16. The system according to claim 14, wherein, The first wiper segment includes a cantilever support structure that supports the wiper blade to keep the wiper blade in position at the surface during advancing and leveling the quantity of powder into the recess.

17. The system according to claim 14, wherein The first wiper segment includes an auger that operates to convey powder along the length of the auger to the recess such that the powder of the powder bed is distributed into the recess.

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