WO2020023008A1

WO2020023008A1 - Method to enhance geometric resolution in arc and high deposition additive manufacturing

Info

Publication number: WO2020023008A1
Application number: PCT/US2018/043301
Authority: WO
Inventors: Gerald J. Bruck
Original assignee: Siemens Energy, Inc.
Priority date: 2018-07-23
Filing date: 2018-07-23
Publication date: 2020-01-30

Abstract

A method of additively manufacturing a component is provided. The method includes providing a substrate on which the component is fabricated, positioning a magnetic edge dam adjacent to the substrate sufficiently near a desired deposit location effective to contain molten material within the magnetic edge dam, depositing a layer of molten material at the desired deposit location for fabrication of the component, generating an electromagnetic force by the magnetic edge dam so that a containment force contains the layer of molten material within the magnetic edge dam, and controlling a shape of an edge of the molten material layer by the generated electromagnetic force.

Description

METHOD TO ENHANCE GEOMETRIC RESOLUTION IN ARC AND HIGH DEPOSITION ADDITIVE MANUFACTURING

BACKGROUND

1. Field

[0001] The present application relates generally to additive manufacturing, and more particularly to a method to enhance geometric resolution in arc and high deposition additive manufacturing.

2. Description of the Related Art

[0002] Additive Manufacturing, or 3-D printing, has recently been successfully used to ‘print’ or manufacture components directly layer by layer. This manufacturing technology enables the optimization of component design. Additive manufacturing of components includes a wide range of materials and process techniques and may be used to build complex shapes or structures that would be difficult to make using traditional forming and removal processes, (e.g., casting and machining). Producing components that are relatively expensive to manufacture, such as superalloy gas turbine components, using additive manufacturing may decrease the manufacturing costs by reducing waste of expensive materials and the time taken to produce the components.

[0003] Wire arc-based additive manufacturing (WAAM) is one such additive manufacturing process technique that involves utilizing an electric arc as a heat source in combination with a metallic wire as the feed source. A power source is used to create the electric arc which extends from an electrode to the base material. The arc quickly heats and melts the metallic wire at the base material. The wire itself may be used as a consumable electrode as in the case of Gas Metal Arc Welding (GMAW). Or, in contrast, a non-consumable electrode such as a tungsten electrode may be used such as in Gas Tungsten Arc Welding (GTAW). With GTAW, the metallic wire is fed into a pool of molten metal created when the electrical arc extends from the tip of the tungsten electrode to the base material forming the molten pool of metal. The melted wire is then used to add material in the form of layers to the base material. In both of these processes, GMAW and GTAW, an inert gas may be needed to shield the molten pool area protecting it from oxidation and contamination with foreign particles.

[0004] Wire arc-based manufacturing represents some advantages and some disadvantages over conventional powder-based additive manufacturing techniques such as selective laser melting (SLM). A comparison of selective laser melting (SLM) and wire arc additive manufacturing (WAAM) follows in Table 1 :

Table 1 - Comparison of SLM and WAAM

[0005] From Table 1, it is evident that for components requiring control of detail,

SLM is a preferred choice. Low deposition rate, however, is a major limitation of SLM. For parts requiring less refined detail (e.g. components that would be post- processed machined), WAAM would be of major advantage in terms of deposition rate. Additionally, other considerations may be seen in Table 2:

Table 2 - Additional Considerations when Comparing SLM and WAAM

[0006] Traditionally, WAAM has not been considered for the manufacture of 3D metal printing of more complex components, such as gas turbine components, because of the disadvantages listed above. However, if the geometry, (e.g. dimensional accuracy, surface roughness, etc.) can be improved, WAAM can be utilized for the 3D metal printing of components in a highly productive and flexible way.

[0007] Consequently, a need exists for an improved method to control geometric resolution of fabricated components with wire arc-based additive manufacturing.

SUMMARY [0008] Briefly described, aspects of the present disclosure relate to methods to additively manufacture components and specifically to enhance the geometric resolution in arc and high deposition rate additive manufacturing.

[0009] A first aspect provides a method of additively manufacturing a component. The method includes providing a substrate on which the component is fabricated, positioning a magnetic edge dam adjacent to the substrate sufficiently near a desired deposit location effective to contain molten material within the magnetic edge dam, depositing a layer of molten material at the desired deposit location for fabrication of the component, generating an electromagnetic force by the magnetic edge dam so that a containment force contains the layer of molten material within the magnetic edge dam, and controlling a shape of an edge of the molten material layer by the generated electromagnetic force.

[0010] A second aspect provides a method to enhance geometric resolution in wire arc based additive manufacturing. The method includes providing a substrate on which the component is fabricated and straddling a deposition region with a plurality of magnetic edge dams (MEDs) in order to contain a molten material within the MEDs, The MEDs comprise an induction coil wound around at least a portion of a magnetic material. A layer of molten material is additively deposited in the deposition region for fabrication of the component utilizing an arc weld system and a metallic wire. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Fig. 1 illustrates a perspective view of a GTAW process,

[0012] Fig. 2 illustrates an end view of a deposit with magnetic dam control using the GTAW process of Fig. 1, [0013] Fig. 3 illustrates and end view of a deposit straddled by magnetic edge dams producing an electromagnetic force to contain and shape the edges of the deposit

[0014] Fig. 4, illustrates a perspective view of a GMAW process to deposit a layer of material, and [0015] Fig. 5 illustrates an end view of a deposit without using magnetic edge dam control.

DETAILED DESCRIPTION

[0016] To facilitate an understanding of embodiments, principles, and features of the present disclosure, they are explained hereinafter with reference to implementation in illustrative embodiments. Embodiments of the present disclosure, however, are not limited to use in the described systems or methods.

[0017] The components and materials described hereinafter as making up the various embodiments are intended to be illustrative and not restrictive. Many suitable components and materials that would perform the same or a similar function as the materials described herein are intended to be embraced within the scope of embodiments of the present disclosure.

[0018] Electromagnetic edge dams, referred to as magnetic edge dams (MEDs) throughout this disclosure, have been previously employed to contain molten metal during various casting processes to produce thin sheets. Examples of processes that use MEDs in the prior art include Lari US 4,974,661 and Bhamidipati US 2004/0050530. In order to contain the molten metal, an electromagnetic field is used to induce a current to flow through the molten metal to create the desired containment forces. The magnetic edge dam may comprise a magnetic core material wrapped with induction coils which may be placed on one or both sides of the molten pool to contain or shape the edges of the molten material.

[0019] For example, Bhamidipati, US 2004/0050530, utilized an electromagnetic edge dam to contain molten material during strip casting. The molten metal is delivered between curved surfaces of two belts to form a metallic strip and contained by a pair of edge containment devices positioned adjacent to the belts so that an electromagnetic field passes through the molten material.

[0020] This disclosure teaches an improved method to refine the deposit geometry during arc-based additive manufacturing. In particular, electromagnetic edge shaping is proposed to control the geometry of the edges/surfaces of the deposit during processing, i.e., during deposition, melting, and solidification. For the purposes of this disclosure, an edge of a deposit is defined as a surface of the deposit.

[0021] Referring now to the figures, Fig. 1 illustrates the tools required for Gas Tungsten Arc Welding (GTAW), which is also commonly known as Tungsten Inert Gas (TIG) welding. A TIG arc weld system 100 includes a torch 110 with a gas cup 115 or nozzle and a tungsten electrode 120 positioned partially within the cup 115. A solid, metal cored or flux cored weld wire 125 is used to add material during the welding process. When TIG welding, a welder forms an electrical arc 145 that extends from the tip of the tungsten electrode 120 to a substrate 130 in the location where the weld is being made. The arc 145 quickly heats and melts the substrate 130 to form a melt pool 135 of molten metal. The welder manually feeds the weld wire 125 into the melt pool 135 where the wire 125 melts and forms part of the weld bead after the molten metal cools. Alternately, a wire feed device may be used to automatically feed the weld wire 125 into the melt pool 135. An inert gas 140 (e.g., argon) is discharged into the cup 115 and maintained around the arc 145 and the weld pool 135 to protect both the electrode 120 and the weld pool 135 from oxidation which can otherwise cause electrode deterioration and flaws in the weld. TIG welding is well-known for the quality of welds that can be formed using the process and is well-suited to delicate work or welding of materials that have lower weldability. An alternate arc weld process, as discussed above, Gas Metal Arc Welding (GMAW) is a similar process to GTAW that utilizes the metal wire 125 as both the electrode and additive material.

[0022] Arc-based process techniques, such as GTAW and GMAW as described above, may be adapted to additive manufacturing (AM) such that layers of additive material, in the form of the molten material produced by the process, may be used to form, layer by layer, a desired component. Adaptations for AM may include modification of the turntable for endless rotation, modified control software, programmed robotic manipulation of welding torch and filler addition, increased thermal management and robust wear parts in the power source to cope with long arc- on durations. However, at this time, arc-based AM is only a near net-shape process and not a final desired net-shape process. The surface finish of the component may include a waviness. To remedy the wavy finish, typically the component must be finish-machined. Thus, an arc-based AM process that enhances the geometric resolution of the deposited layer and includes higher deposition rates for larger components is desired.

[0023] Broadly, a method of additively manufacturing a component is proposed. The method includes providing a substrate on which the component is fabricated, positioning a magnetic edge dam adjacent to the substrate sufficiently near a desired deposit location effective to contain molten material within the magnetic edge dam, depositing a layer of molten material at the desired deposit location for fabrication of the component, generating an electromagnetic force by the magnetic edge dam so that a containment force contains the layer of molten material within the magnetic edge dam, and controlling a shape of an edge of the molten material layer by the generated electromagnetic force.

[0024] Referring now to Fig. 2, a deposit 210 is shown additively deposited using a GTAW process with electromagnetic dam control. Fig. 2 illustrates the proposed process utilizing the GTAW torch 110 and tungsten electrode 120 as shown and described in Fig. 1. A substrate 130 is provided upon which the desired component is fabricated. In the shown embodiment, magnetic edge dams 200 are positioned adjacent to the substrate 130 on either side of the deposit 210 in order to contain the molten material 135 within the magnetic edge dam 200. A layer of material is deposited by the GTAW process as described above. A metallic weld wire 125 is used to supply material to the deposit 210. The electrical arc 145 quickly heats and melts the substrate 130, and/or a top layer of the deposit 210, and the end of the weld wire 125 to form a melt pool 135 of molten metal. In the shown embodiment, the molten material 135 is deposited on top of previously formed solidified deposited layers of material 210 in order to form a desired component. The two magnetic edge dams 200 straddling the deposited layer 210 generate an electromagnetic force to contain the layer of molten material 135 within the magnetic edge dams 200.

[0025] The position and spacing of the MED relative to the molten metal 135 depends on a number of factors including, alloy type, size of the molten pool, surface tension of the molten pool, orientation of deposition, arc force on molten pool, and the coil current in the MED. The coil current in the MED will affect the resulting magnetic field strength, the resulting induced eddy current strength in the molten metal skin, and the resulting reaction force on the molten pool. That is, the magnetic field must be close enough and strong enough to induce currents and reaction forces to control and balance the molten metal head and arc pressure. A trade-off is necessary between having close proximity to achieve adequately strong magnetic fields and having enough space to avoid contact between molten metal and the magnet to avoid overheating of an insulated and water-cooled magnet, for example. With currently available MED equipment, such distance from dam to sides of molten deposit will likely fall in the range of about 1 to 5 mm.

[0026] In an embodiment, the magnetic edge dams 200 may be held by brackets 150 to the GTAW torch body 110 as shown in Fig. 2 so that the dams 200 extend vertically towards the substrate 130. The positioning of the magnetic edge dams 200 with respect to the desired deposit location of the molten material should be a sufficient distance as described above so that the magnetic lines of force pass through the molten material and sufficiently contain and shape the molten material. The containment force is such that the dams 200 do not come in contact with the molten pool 135; the pool is shaped electromagnetically. [0027] In the embodiment shown in Fig. 2, the under-support for the melt pool 135 is provided by the underlying solid deposit 210. The lateral edges 215 of the melt pool 135 are contained and shaped by the MEDs 200 of relatively equal and balanced strength. Alternately, for example, with out of position processing, such as when depositing in a horizontal orientation, i.e., melt pool 135 deposited against a vertical wall, the MED 200 under the melt pool 135 may need to be of greater strength to achieve sufficient force to support the melt pool 135 subject to gravity.

[0028] In an embodiment as shown in Fig. 3, each MED 200 may comprise a magnetic material 220 such as iron doped plastic, wound by a plurality of induction coils 230 such as copper. An alternating electrical current may be imposed in the plurality of induction coils 230 by an electrical means 250 such as produced from an electrical alternating current power supply. Alternately, direct current may also be supplied to generate an electromagnetic field. In the shown embodiment of Fig. 3, the supplied current generates a vertical electromagnetic field (B), which induces eddy currents 240 to form within the skin of the molten material and produces the necessary containment forces to contain the molten metal within the MED 200 and shape the lateral edges 215 of the molten metal opposite the MEDs 200. The horizontal closed eddy current loops 240 interact with the electromagnetic field (B) producing a reaction force (F) to flatten the sides of the molten metal and achieve flat sides in the solidified deposit 210.

[0029] In the embodiment of Fig. 4, a perspective view of a GMAW arrangement to additively deposit material may be seen. A metallic wire 125 feeds to the point of the arc (not shown) where the melting and deposition occurs. The front edge of molten deposit advances in the direction of travel (shown by the arrows). The shape of the front of the melt pool 135 is controlled by surface tension, gravity, and arc force while the back of the melt pool continuously solidifies against solid deposit. In the shown embodiment, the shape of the lateral edges 215 of the melt pool opposite the magnetic edge dams 200 are controlled by the generated electromagnetic force (F). A narrowing of the deposit may be achieved by increasing the coil current. A widening of the deposit may be achieved by decreasing the coil current. A flattened and planar deposit lateral edge consistent with underlying solid material may be accomplished by an optimized coil current of consistent magnitude. [0030] The arc weld processes, GTAW, as shown in Fig. 2 and GMAW, as shown in Fig. 4 are non-limiting examples of processes using MEDs to control a melt pool when depositing material. Similar control with MEDs would apply to other potential wire additive processes such as submerged arc welding (SAW), plasma arc welding (PAW), and laser beam welding (LBW).

[0031] The arc weld system 100 and the substrate 130 are programmed to move relative to one another in order to deposit the additive material as desired. In an embodiment, the arc weld system 100 is driven by, for example, carriages or robotics and traverses the surface of the substrate 130 in order to deposit a layer 210 as desired. In an alternate embodiment, the substrate 130 may be driven by, for example, a multi- directional positioner to traverse relative to a stationary arc weld system 100 in order to deposit the desired layer.

[0032] When utilizing an MED in conjunction with an arc weld system, coolant such as water and a heat shield may be needed to protect the MED from over-heating due to the nearby arc. Such a heat shield and heat sink to protect and cool the magnet may be found in Lari, ETS 4,974,661, for example.

[0033] The MED structure as seen in Figs. 2-4 may be utilized to control the geometric shape of the lateral edges 215 of the deposited layer of molten material. For example, with the arrangement shown in Fig. 3 the lateral edges 215 may be straightened and parallel to one another while also being perpendicular to the substrate 130. An example of a deposit using a WAAM process without the MED control may be seen in Fig. 5. Fig. 5 illustrates a three-layered deposit where the lateral edges 215 of each layer are lumpy and rounded resulting from surface tension and gravitational effects. This rolling of the lateral edges 215 may be especially prevalent with larger components where the large molten pool is more prone to rolling due to gravitational effects. In contrast to the rounded lumpy lateral edges 215 of the deposit shown in Fig. 5, the lateral edges 215 of a deposit as shown in Fig.2 utilizing MED control are flat and smooth.

[0034] In another embodiment, the geometry of a deposit edge may be precisely controlled so that, for example, specific edge geometries may be formed. Thus, the magnetic field may be tailored to achieve the desired geometry. For example, this may be accomplished utilizing an MED comprising a series of induction coils and separately controlling the intensity of the magnetic force of each coil to achieve different forces on the molten material. Thus, the edge of the molten material may be defined into a desired geometry such as a concave form.

[0035] In order to complete the buildup of the component, successive layers of molten material may be deposited layer upon layer. Thus, the method steps are repeated for each successive layer until the buildup of the component is complete. In an embodiment, the deposition is programmed so that the arc weld system 100 and the substrate 130 move relative to one another to achieve the desired pattern of deposit 210.

[0036] In an embodiment, the substrate 130 may be positioned in an orientation other than a flat position having the layer disposed on top of the substrate 130. For example, the substrate 130 may be disposed in a vertical position or an overhead position relative to the ground. Having magnetic forces that are stronger than the gravitational force enables the MED 200 to completely control the deposit geometry. For example, the substrate 130 may be positioned on a vertical wall. Utilizing a single MED positioned adjacent to the substrate 130, an edge of the layer of the molten material (disposed opposite to the MED) may be defined into a desired geometry. This versatility enables out of position processing that is not possible with current SLM technologies. For example, repair build-up of the blade tip, blade airfoil, and top, side, and underside of a turbine blade platform is possible with such processing without repositioning of the part.

[0037] As discussed previously, the deposition rates of traditional additive manufacturing processes such as selective laser melting is only 0.1 to l.Okg/hr. However, by using a WAAM process combined with the use of an MED to contain and shape the molten material as exemplified in the proposed method, the deposition rates may extend to at least as high as 6 kg/hr and with comparable dimensional control.

[0038] In an embodiment, the component may be a gas turbine component. As many gas turbine components comprise superalloy materials, the metallic wire 125 may be a superalloy material. Superalloy materials are suitable for gas turbine components, for example, as these materials have superior high heat related properties as well as low oxidation and corrosion rates. As an example, an exit mouth portion of the transition component in the combustion section of the gas turbine may be fabricated utilizing the proposed method. Because gas turbine components are generally larger components, an additive manufacturing method such as that proposed with its higher deposition rates than traditional SLM processes would be beneficial for their manufacture.

[0039] In an embodiment, a post-processing step may be performed after the buildup of the component is complete. Post processing steps may include, but are not limited to, an inspection to determine residual stress in the material, and then if residual stress is determined to exist in the deposited layer 210, a heat treatment may be performed to remove the residual stress. Post-deposition heat treatment is also required to age harden and strengthen certain alloys such as nickel-based superalloys. The determination of whether to perform post-processing steps depends on the specific alloy used for fabrication of the component. Further, the post processing may include machining or otherwise finishing the component, however, by utilizing the proposed method, post-processing machining may be eliminated or reduced as the geometry of the layers may be more precise.

[0040] It should be appreciated that aspects of the method of manufacturing disclosed herein, particularly the deposition process, may be implemented by any appropriate processor system using any appropriate programming language or programming technique. The system can take the form of any appropriate circuitry, such as may involve a hardware embodiment, a software embodiment or an embodiment comprising both hardware and software elements. In one embodiment, the system may be implemented by way of software and hardware (e.g., processor and sensors, etc.) which may include but is not limited to firmware, resident software, microcode, etc.

[0041] Thus, the disclosure provides an arc additive manufacturing process that can more precisely control the deposit geometry than traditional WAAM processes. While arc base embodiments have been described, the proposed method could extend to depositions from non-arc energy sources such as laser and electron beam. Further, an advantage of the proposed method is that the molten metal in the disclosed embodiments does not contact the MED. That is, no physical shoes (e.ge. ceramic, copper, etc.) are required to contain the molten metal. Thus, the containment is robust in terms of process equipment wear. Additionally, the described processes may be done from any position, i.e., the substrate does not need to lay flat as is needed for selective laser melting and selective layer sintering processes.

[0042] While embodiments of the present disclosure have been disclosed in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the invention and its equivalents, as set forth in the following claims.

Claims

What is claimed is:

1. A method of additively manufacturing a component, comprising: providing a substrate 130 on which surface the component is fabricated;

positioning a magnetic edge dam 200 adjacent to the substrate 130 sufficiently near a desired deposit location on the substrate 130 effective to contain molten material within the magnetic edge dam 200;

depositing a layer of molten material at the desired deposit location for fabrication of the component;

generating an electromagnetic force by the magnetic dam 200 so that a containment force contains the layer of molten material within the magnetic dam 200; and

controlling a shape of an edge of the molten material layer by the generated electromagnetic force.

2. The method as claimed in claim 1, wherein a pair of magnetic edge dams 200 straddle the desired deposit location in order to contain molten material within the magnetic edge dams 200.

3. The method as claimed in claim 2, wherein the controlling includes straightening lateral edges 215 of the solidifying weld pool 135 of the solidified deposited layer 210 so that the lateral edges 215 are parallel to one another and/or perpendicular to the substrate 130.

4. The method as claimed in claim 3, wherein the controlling includes preventing rolling of the lateral edges 215 of the deposited layer 210.

5. The method as claimed in claim 1, wherein the controlling includes controlling the geometry of the edge of the deposited layer 210 into a desired geometry, and

wherein the magnetic edge dam 200 comprises a series of induction coils 230 so that the controlling includes separately controlling an intensity of each coil 230 with the result that different forces are applied on the molten metal and the desired geometry is formed.

6. The method as claimed in claim 1, wherein the substrate 130 is positioned in various positions relative to ground, and

wherein a single MED 200 contains the molten material layer against the substrate 130 and controls the shape of the edge of the molten material opposite the MED.

7. The method as claimed in claim 1, wherein the depositing is accomplished utilizing a wire arc-based additive manufacturing (WAAM) process, and

wherein the WAAM process involves utilizing an arc weld system 100 and a metallic wire 125.

8. The method as claimed in claim 7, wherein the magnetic edge dam 200 is attached to a torch 110 of the arc weld system 100 by a bracket 150 so that the MED 200 extends adjacent to the desired deposit location effective to contain the molten material within the MED 200.

9. The method as claimed in claim 1, wherein the deposition rate of the depositing is up to 6kg/hr.

10. The method as claimed in claim 7, further comprising traversing the substrate surface 130 by the arc weld system 100 so that the layer 210 of molten material is deposited as desired.

11. The method as claimed in claim 7, further comprising moving the substrate surface 130 relative to the stationary arc weld system 100 so that the layer 210 of molten material is deposited as desired.

12. The method as claimed in claim 1, wherein successive layers of molten material are deposited upon the layer until a buildup of the component is complete.

13. The method as claimed in claim 1, further comprising upon completing the component, heat treating the component in order to remove the residual stress and optimize micro structure and properties within the component.

14. The method as claimed in claim 1, further comprising upon completing the desired component, machining the component to finish the component.

15. The method as claimed in claim 1, wherein the component is a gas turbine component.

16. The method as claimed in claim 1, wherein the metallic wire is a nickel-based superalloy material.

17. The method as claimed in claim 1, wherein the depositing is accomplished utilizing a wire energy beam based additive manufacturing process such as wire laser welding or hybrid laser plus arc welding, and

wherein the process involves utilizing an energy beam weld system and a metallic wire 125.

18. A method to enhance geometric resolution in wire arc-based additive manufacturing, comprising:

providing a substrate 130 on which the component is fabricated;

straddling a deposition region with a plurality of magnetic edge dams 200 in order to contain a molten material within the MEDs, the MEDs comprising an induction coil wound 230 around at least a portion of a magnetic material 220;

additively depositing a layer 210 of molten material in the deposition region for fabrication of the component utilizing an arc weld system 100 and a metallic wire 125;

providing a current to the induction coil 230 to create a magnetic force sufficient to contain the molten material within the MED 200;

moving the substrate 130 and the arc weld system 100 relative to one another to achieve a desired pattern of the layer 210 of molten material; and

controlling a geometry of the lateral edges 215 of the molten material by the generated electromagnetic force.

19. The method as claimed in claim 18, the controlling including adjusting the intensity of the generated electromagnetic force to control the geometry of the lateral edges 215 of the molten material.

20. The method as claimed in claim 19, wherein the deposition rate of the depositing is up to 6kg/hr.