Heat extraction or retention during directional solidification of cast parts

Abstract

Provides heat extraction or retention during directional solidification of the cast part. A casting system includes a chamber having a heating zone and a cooling zone separated by a baffle plate. The method includes pouring a liquid alloy into a mold shell. The mold shell is positioned on a chill plate within the heating zone. The method further includes moving the mold shell from the heating zone to the cooling zone. During the movement of the mold shell from the heating zone to the cooling zone, the alloy transitions from the liquid state to a solid state within the mold shell. The method further includes contacting the mold shell with a heat transfer member.

Description

[Technical Field]

[0001] The present invention relates generally to materials and processes for producing directionally solidified castings, and more particularly to reducing defects in alloys cast as single-crystal (SX) and directionally solidified (DS) articles suitable for use as components in gas turbines and other high-temperature applications.

[0002] Gas turbine components, such as blades, vanes, and combustor components, are typically made from nickel, cobalt, or iron-base superalloys and are characterized by desirable mechanical properties at the turbine's operating temperatures. Because gas turbine efficiency depends on its operating temperature, components—particularly turbine buckets, nozzles, combustor components, and other hot-gas-path components—must be able to withstand higher temperatures. As the material requirements for gas turbine components increase, various processing methods and alloying elements have been used to improve the mechanical, physical, and environmental properties of components made from superalloys. For example, buckets, nozzles, and other components used in demanding applications are often cast using directional casting techniques to produce columnar polycrystalline or single-crystal articles with DS or SX microstructures characterized by selected directional crystal orientations or growth directions.

[0003] Casting techniques for producing SX and DS castings generally involve pouring a melt of the desired alloy into an investment mold maintained above the alloy's liquidus temperature. Solidification of the molten alloy within the mold occurs by gradually withdrawing the mold from a directional heating zone to a cooling zone, where cooling occurs by convection and / or radiation. Solidification begins at the bottom of the mold, and the solidification front progresses to the top of the mold. A high thermal gradient is required at the solidification front to prevent the nucleation of new grains during directional solidification processes.

[0004] During the directional solidification process of parts with complex geometries, grain defects can occur due to localized hot spots that do not cool at the same rate as the rest of the part.

[0005] To prevent grain defects during DS casting, various methods for increasing the thermal gradient and cooling rate have been reported in the prior art. These methods include higher mold heating temperature, higher superheat during melting, gas cooling, liquid metal cooling, tight baffle control, alloy modification, and graphite embedding at the shell exterior surface for high local thermal conductivity. The embedded graphite is exposed to radiant heat, so its impact on heat extraction is minimal. This graphite is a stationary component fixed to the shell throughout the casting process. It is not possible to timely control heat extraction with respect to the moment of solidification at a specific location on the cast component. As the next generation of large industrial gas turbines (IGTs) continues to grow in size, turbine blades will also become significantly taller and more complex in shape than smaller IGT blades and aircraft jet engine blades. Larger casting sizes make it more difficult to prevent grain defects and maintain high yields due to the lower thermal gradients caused by the large amount of latent heat of fusion.

[0006] Thus, improved systems and methods for cooling cast components during the directional solidification process are desirable and would be appreciated in the art. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-163200 Summary of the Invention

[0008] Aspects and advantages of the casting system and method according to the present disclosure will be set forth in part in the description which follows, or will be obvious from the description, or may be learned by practice of the art.

[0009] According to one embodiment, there is provided a method for forming a directionally solidified cast part using a casting system. The casting system includes a chamber having a heating zone and a cooling zone separated by a baffle plate. The method includes pouring a liquid alloy into a mold shell. The mold shell is positioned on a chill plate within the heating zone. The method further includes moving the mold shell from the heating zone to the cooling zone. During the movement of the mold shell from the heating zone to the cooling zone, the alloy transitions from the liquid state to a solid state within the mold shell. The method further includes contacting the mold shell with a heat transfer member.

[0010] According to another embodiment, a casting system for forming a directionally solidified cast component is provided. The casting system includes a chamber and a baffle plate disposed within the chamber. The chamber and the baffle plate collectively define a heating zone and a cooling zone. The heating zone and the cooling zone are separated by the baffle plate. The casting system further includes a chill plate movable between the heating zone and the cooling zone. The casting system further includes a mold shell disposed on the chill plate. The casting system further includes a heat transfer member extending from a first end to a second end. The heat transfer member is operable between a first position in which the second end is not in contact with the mold shell and a second position in which the second end is in contact with the mold shell.

[0011] These and other features, aspects, and advantages of the method of the present invention will be better understood with reference to the casting system and the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present technology and, together with the description, serve to explain the principles of the present technology. [Brief explanation of the drawings]

[0012] The following specification, with reference to the accompanying drawings, contains a complete and enabling disclosure, to one skilled in the art, of the casting system and method of the present invention, and the best way to make and use the same. [Figure 1] 1 is a schematic diagram of a turbomachine according to an embodiment of the present disclosure; FIG. [Figure 2] 1 illustrates a cross-sectional view of a casting system for forming a directionally solidified cast part according to an embodiment of the present disclosure. [Figure 3] 1 illustrates a cross-sectional view of a casting system for forming a directionally solidified cast part according to an embodiment of the present disclosure. [Figure 4] 1 illustrates a cross-sectional view of a casting system for forming a directionally solidified cast part according to an embodiment of the present disclosure. [Figure 5] 1 illustrates a cross-sectional view of a casting system for forming a directionally solidified cast part according to an embodiment of the present disclosure. [Figure 6] 1 illustrates a cross-sectional view of a casting system for forming a directionally solidified cast part according to an embodiment of the present disclosure. [Figure 7] FIG. 1 is a cross-sectional view of a casting system for forming a directionally solidified cast part according to an embodiment of the present disclosure. [Figure 8] 1 illustrates a cross-sectional view of a casting system for forming a directionally solidified cast part according to an embodiment of the present disclosure. [Figure 9] FIG. 1 is a flow diagram of one embodiment of a method for forming a directionally solidified cast component using a casting system in accordance with an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0013] Reference will now be made in detail to embodiments of the casting system and method of the present invention. One or more examples of these embodiments are illustrated in the drawings. Each example is provided for illustrative purposes, not limiting. Indeed, it will be apparent to those skilled in the art that modifications and variations can be made in the teachings of the present invention without departing from the scope or spirit of the claimed teachings. For example, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Accordingly, the present disclosure is intended to cover such modifications and variations within the scope of the appended claims and their equivalents.

[0014] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. Moreover, unless otherwise specified, all embodiments described herein are to be considered exemplary.

[0015] The detailed description uses numbers and letters to refer to features in the drawings. Like or similar designations in the drawings and description are used to refer to like or similar parts of the invention. In this specification, the terms "first," "second," and "third" may be used interchangeably to distinguish one component from another and are not intended to denote the location or importance of the individual components.

[0016] A "fluid" may be a gas or a liquid. "Fluid communication" means that a fluid can communicate between designated areas.

[0017] As used herein, the terms "upstream" (or "forward") and "downstream" (or "rearward") refer to relative directions with respect to fluid flow in a fluid pathway. For example, "upstream" refers to the direction in which a fluid flows, and "downstream" refers to the direction in which a fluid flows. However, as used herein, the terms "upstream" and "downstream" can also refer to the flow of electricity. The term "radial" refers to a relative direction that is substantially perpendicular to an axial centerline of a particular component, the term "axial" refers to a relative direction that is substantially parallel and / or coaxially aligned with an axial centerline of a particular component, and the term "circumferential" refers to a relative direction that extends around an axial centerline of a particular component.

[0018] Approximate terms such as "about," "approximately," "generally," and "substantially" are not limited to the exact value specified. In at least some instances, approximate terms may correspond to the precision of an instrument that measures a value, or the precision of a method or machine that constructs or manufactures a component and / or system. In at least some instances, approximate terms may correspond to the precision of an instrument that measures a value, or the precision of a method or machine that constructs or manufactures a component and / or system. For example, approximate terms may refer to within a margin of 1, 2, 4, 5, 10, 15, or 20 percent of an individual value, a range of values, and / or any of the endpoints that define a range of values. When used in the context of angles or directions, such terms include angles within 10 degrees of the specified angle or direction. For example, "generally vertical" includes directions within 10 degrees of vertical in any direction, such as clockwise or counterclockwise.

[0019] Terms such as "coupled," "fixed," and "attached" refer to both direct coupling, fixing, or attachment, as well as indirect coupling, fixing, or attachment via one or more intermediate components or features, unless otherwise specified herein. As used herein, the terms "comprise," "includes," "includes," "including," "has," "having," or other variations thereof are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus consisting of a list of features is not necessarily limited to only those features but may include other features not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, unless expressly stated to the contrary, "or" means an inclusive or, not an exclusive or. For example, condition A or condition B is satisfied by any one of the following: A is true (or present) and B is false (or absent), A is false (or absent) and B is true (or present), and both A and B are true (or present).

[0020] Throughout this specification and claims, range limitations are combinable and interchangeable, and such ranges are specified and include all subranges contained therein, unless the context or language dictates otherwise. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other.

[0021] Referring now to the drawings, Figure 1 shows a schematic diagram of one embodiment of a turbomachine, which in the illustrated embodiment is a gas turbine 10. Although industrial or land-based gas turbines are shown and described herein, unless otherwise expressly stated in the claims, the present invention is not limited to land-based and / or industrial gas turbines. For example, the invention described herein may be used with any type of turbomachine, including, but not limited to, a steam turbine, an aircraft gas turbine, or a marine gas turbine.

[0022] As shown, the gas turbine 10 generally includes an inlet section 12, a compressor section 14 disposed downstream from the inlet section 12, multiple combustors (not shown) in a combustor section 16 disposed downstream from the compressor section 14, a turbine section 18 disposed downstream from the combustor section 16, and an exhaust section 20 disposed downstream from the turbine section 18. Additionally, the gas turbine 10 may include one or more shafts 22 coupled between the compressor section 14 and the turbine section 18.

[0023] Compressor section 14 generally includes a plurality of rotor disks 24 (one of which is shown) and a plurality of rotor blades 26 extending radially outward from and connected to each rotor disk 24. Each rotor disk 24 may be coupled to or form part of a shaft 22 that extends through compressor section 14.

[0024] Turbine section 18 may typically include a plurality of rotor disks 28 (one of which is shown) and a plurality of rotor blades 30 extending radially outward from and interconnected to each rotor disk 28. Each rotor disk 28 may be coupled to or form a part of a portion of a shaft 22 that extends through turbine section 18. Turbine section 18 further includes an outer casing 31 circumferentially surrounding the portion of shaft 22 and rotor blades 30, thereby at least partially defining a hot gas path 32 through turbine section 18.

[0025] During operation, a working fluid, such as air, flows through the inlet section 12 and into the compressor section 14, where it is progressively compressed, providing compressed air to the combustors in the combustion section 16. The compressed air is mixed with fuel and combusted in each combustor to generate combustion gases 34. The combustion gases 34 flow from the combustion section 16 through the hot gas path 32 and into the turbine section 18, where energy (kinetic and / or thermal energy) is transferred from the combustion gases 34 to the rotor blades 30, causing the shaft 22 to rotate. This mechanical rotational energy can then be used to power the compressor section 14 or generate electricity. The combustion gases 34 exit the turbine section 18 and leave the gas turbine 10 through the exhaust section 20.

[0026] 2-8, cross-sectional views of a casting system 100 for forming a directionally solidified cast component are shown, according to an embodiment of the present invention. As described in more detail below, the directionally solidified cast component may be formed from a molten alloy solidifying within a mold shell 122. In an exemplary embodiment, the directionally solidified cast component may be a turbomachine component (such as a rotor blade, stator vane, or fuel nozzle). For example, the directionally solidified cast component may be a rotor blade, such that the cast component includes a shank and an airfoil extending from the shank. As such, the mold shell 122 may have a shank portion 102 and an airfoil portion 104 that correspond to the shapes of the shank and airfoil portions of a turbomachine rotor blade. The casting system 100 may define a Cartesian coordinate system having a vertical direction V, a longitudinal direction L, and a transverse direction T (extending into and out of the plane of the page in FIG. 2, though not shown). The vertical direction V, the longitudinal direction L, and the transverse direction T may be orthogonal to one another.

[0027] As shown in the figures, the casting system 100 includes a chamber 108 and a baffle plate 110 disposed within the chamber 108. For example, the chamber 108 may be a solid structure defining an interior volume 112 (i.e., the term "chamber" as used herein refers to solid walls defining an interior volume). The baffle plate 110 may separate the interior volume 112 into a heating zone 114 and a cooling zone 116. For example, the chamber 108 and the baffle plate 110 may collectively define the heating zone 114 and the cooling zone 116. The heating zone 114 and the cooling zone 116 are separated by the baffle plate 110, with a first side of the baffle plate 110 defining the heating zone 114 and a second side of the baffle plate 110 defining the cooling zone 116.

[0028] The casting system 100 may further include a chill plate 118 that is movable (e.g., vertically movable) between the heating zone 114 and the cooling zone 116. For example, the chill plate 118 is coupled to a shaft 120 that may be actuated along a vertical direction V (e.g., via one or more linear actuators 201, indicated by the circled "A"). In various embodiments (not shown), the chill plate 118 may be a water-cooled chill plate 118. For example, the chill plate 118 may be defined with one or more water-cooling circuits that circulate water through the chill plate 118. Furthermore, in many embodiments, the chill plate 118 may be constructed of a highly thermally conductive material, such as copper or a copper alloy.

[0029] The casting system 100 may further include a mold shell 122 disposed on the chill plate 118. For example, the mold shell 122 may extend vertically from a base 125 disposed on the chill plate 118 to a tip 126. The mold shell 122 may define a cavity 128 into which the alloy 162 in a liquid state (i.e., the alloy 164 in a liquid state) can be poured into the heating zone 114 (e.g., from the crucible 124). The mold shell 122 may then be moved (e.g., by actuating the shaft 120 to move the chill plate 118 and the mold shell 122 from the heating zone 114 to the cooling zone 116). Once the mold shell 122 is moved to the cooling zone 116, the alloy solidifies (i.e., directionally solidifies) to a solid state (solid alloy 166) within the mold shell 122 from the base 125 to the tip 126 of the mold shell 122, forming a directionally solidified cast part. For example, alloy 162 transitions from a liquid state to a solid state as mold shell 122 is moved from heating zone 114 and cooling zone 116. As shown in Figures 2-8, horizontal dashed lines within mold shell 122 represent alloy 162 in a liquid state (e.g., alloy 164 in a liquid state) and cross-hatching within mold shell 122 represents alloy 162 in a solid state (e.g., alloy 166 in a solid state).

[0030] As the mold shell 122 moves from the heating zone 114 to the cooling zone 116, a solidification front 130 may form between the liquid alloy 162 (164) and the solid alloy 162 (166) within the mold shell 122. While the solidification front 130 is shown as a line, it should be understood that the solidification front 130 may be a range (e.g., a vertical range) within the mold shell 122. More specifically, the solidification front 130 may be the portion of the alloy 162 that is within a solidification temperature range. The solidification temperature range may be a temperature range in which the alloy 162 may transition from a liquid state to a solid state. Furthermore, the alloy 162 at (and above) the solidification front 130 may be higher than the solidus temperature of the alloy 162. That is, the solidus temperature is the highest temperature at which the alloy 162 becomes completely solid, and the temperature at (and above) the solidification line (in the vertical direction V) may be higher than the solidus temperature.

[0031] In many embodiments, the chamber 108 may be a vacuum chamber that can be evacuated by a vacuum system 132. An electric heating element 134 may be disposed within the heating zone 114 to maintain the alloy 162 within the mold shell 122 above its solidus temperature (e.g., to maintain the alloy 164 in a liquid state) while within the heating zone 114. For example, the electric heating element 134 may surround the mold shell 122 when disposed within the heating zone 114. The baffle plate 110 may define an opening 111 through which the mold shell 122 moves between the heating zone 114 and the cooling zone 116. In various embodiments, the baffle plate 110 is disposed above the chill plate 118. The diameter of the opening 111 may be approximately the same size as the maximum area of ​​the mold shell 122 projected from top to bottom.

[0032] To produce a directionally solidified cast part, shaft 120 is moved vertically upward to insert mold shell 122 into heating zone 114. Liquid alloy 164 is poured from crucible 124 into mold shell 122, and then shaft is moved vertically downward to move mold shell 122 through opening 111 from heating zone 114 to cooling zone 116. As a result, alloy 162 changes from a liquid state to a solid state in vertical direction V. For example, alloy 162 initially solidifies at base 125 of mold shell 122, and the solidification front moves vertically upward to tip 126 of mold shell 122.

[0033] Due to the geometric complexity of directionally solidified cast parts, mold shells 122 may not solidify at the same rate (e.g., some portions may solidify faster or slower than others), which may result in one or more defects in the part. Therefore, the exemplary casting system 100 described herein includes a heat transfer member 140 to increase or decrease the solidification rate of the alloy in various portions, as well as the magnitude and direction of the thermal gradient, to prevent the formation of defects. The heat transfer member 140 may be movable within the chamber 108 via an actuator 201. In some embodiments, the heat transfer member 140 extends through a hole in the baffle plate 110 (e.g., a hole separate from the opening 111).

[0034] 2-8 , the casting system 100 further includes a controller 200, which is depicted as a block diagram to illustrate suitable components included therein. As depicted, the controller 200 may include one or more processors 202 and associated memory devices 204 configured to perform various computer-implemented functions (e.g., execute the methods, steps, calculations, etc. disclosed herein and store associated data). Additionally, the controller 200 may also include a communications module 206 that facilitates communication between the controller 200 and various components of the system 100, such as the crucible 124, the shaft 120, the vacuum system 132, the electric heating element 134, and / or the actuator 201. For example, the communications module 218 may communicate with the actuator 201 to enable the processor 202 to selectively move the heat transfer member 140. It should be understood that the crucible 124, shaft 120, vacuum system 132, electric heating element 134, and actuator 201 may be communicatively coupled to the communications module 206 using any suitable means (e.g., a wired connection or a wireless connection using any suitable wireless communications protocol known in the art).

[0035] As used herein, the term "processor" refers not only to integrated circuits referred to in the art as being included in a computer, but also to controllers, microcontrollers, microcomputers, programmable logic controllers (PLCs), application-specific integrated circuits, and other programmable circuits. Additionally, memory device 204 may generally include memory elements including, but not limited to, computer-readable media (e.g., random access memory (RAM)), computer-readable non-volatile media (e.g., flash memory), floppy disks, compact disk read-only memories (CD-ROMs), magneto-optical disks (MODs), digital versatile disks (DVDs), and / or other suitable one or more memory elements. Such one or more memory devices 204 may generally be configured to store appropriate computer-readable instructions that, when implemented by one or more processors 202, configure the system 100 to perform various functions and / or operations, including, but not limited to, pouring the liquid alloy 162 into the mold shell 122 using the crucible 124, moving the mold shell 122 from the heating zone 114 to the cooling zone 116 using the shaft 120, and contacting the mold shell 122 using the heat transfer member 140.

[0036] The heat transfer member 140 may extend from a first end 142 to a second end 144. The heat transfer member 140 may be movable in any of the vertical direction V, the longitudinal direction L, and / or the lateral direction T. For example, the heat transfer member 140 is coupled to an actuator 201, which is operably coupled to a controller 200, and the controller 200 can adjust the position of the heat transfer member 140 by operating the actuator 201. Furthermore, the heat transfer member 140 is extendable and contractible, and the length of the heat transfer member 140 can be increased or decreased. For example, the heat transfer member 140 may have a telescopic structure that can be extended or contracted by the actuator 201. The actuator 201 may include a linear actuator and / or a rotary actuator, and the heat transfer member 140 may be movable / rotatable in any of the vertical direction V, the longitudinal direction L, and the lateral direction T.

[0037] 2 and 3 , the heat transfer member 140 is actuatable between a first position ( FIG. 2 ) in which the second end 144 is not in contact with the mold shell 122, and a second position ( FIG. 3 ) in which the second end is in contact with the mold shell 122. It will be appreciated that while FIG. 3 shows the heat transfer member 140 in contact with a particular portion of the mold shell 122, the heat transfer member 140 is actuatable to contact any portion of the mold shell 122 (e.g., the exterior surface of the mold shell 122).

[0038] In many embodiments, the first end 142 of the heat transfer member 140 may be coupled to the chill plate 118. For example, the first end 142 of the heat transfer member 140 may be pivotally coupled to the chill plate 118 so as to rotate relative to the chill plate 118. Coupling the first end 142 of the heat transfer member 140 to the chill plate 118 may advantageously increase the efficiency of the heat transfer member 140 by increasing the thermal gradient between the heat transfer member 140 and the mold shell 122. For example, the chill plate 118 cools the heat transfer member 140, thereby increasing the temperature difference between the heat transfer member 140 and the mold shell 122, which may cause the heat transfer member to increase the solidification rate of the alloy 162 in the mold shell 122 near the location where the heat transfer member 140 contacts the mold shell 122.

[0039] Alternatively, or additionally, the first end 142 of the heat transfer member 140 may be coupled to the chamber 108. For example, the first end 142 of the heat transfer member 140 may be pivotally coupled to the chamber 108 so as to rotate relative to the chamber 108. In particular, the first end 142 of the heat transfer member 140 may be coupled to the chamber 108 in either the heating zone 114 or the cooling zone 116. Coupling the first end 142 of the heat transfer member 140 to the chamber 108 in the heating zone 114 can advantageously increase the efficiency of the heat transfer member 140 by reducing the thermal gradient between the heat transfer member 140 and the mold shell 122. For example, the heating zone 114 can heat the heat transfer member 140, thereby reducing the temperature difference between the heat transfer member 140 and the mold shell 122. Heat transfer between the heat transfer member 140 and the mold shell 122 allows the heat transfer member to reduce the solidification rate of the alloy 162 in the mold shell 122 near the location where the heat transfer member 140 contacts the mold shell 122. Additionally, in heat retention applications of the heat transfer member 140, the heat transfer member 140 is thermally coupled to the shell mold 122 via radiation, allowing the heat transfer member 140 to reduce the thermal gradient between the heat transfer member 140 and the mold shell 122 without contacting the mold shell 122.

[0040] In contrast, coupling the first end 142 of the heat transfer member 140 to the chamber 108 within the cooling zone 116 may increase the thermal gradient between the heat transfer member 140 and the mold shell 122, advantageously increasing the efficiency of the heat transfer member 140. For example, the cooling zone 116 may cool the heat transfer member 140, thereby increasing the temperature difference between the heat transfer member 140 and the mold shell 122, potentially enabling the heat transfer member to increase the solidification rate of the alloy 162 within the mold shell 122 near the location where the heat transfer member 140 contacts the mold shell 122. Thus, depending at least in part on the location where the first end 142 of the heat transfer member 140 is attached, the function of the heat transfer member 140 may vary from increasing the solidification rate of the alloy 162 by contacting the mold shell 122 to decreasing the solidification rate of the alloy 162.

[0041] FIG. 4 illustrates an enlarged cross-sectional view of a heat transfer member 140 according to an embodiment of the present disclosure. In particular, FIG. 4 illustrates an enlarged cross-sectional view of the detail enclosed by the dashed line in FIG. 3. As shown, the heat transfer member 140 may include a body 154 defining an outer surface 156. Additionally, in many embodiments, the heat transfer member 140 may include an oxidation-resistant coating 158. The oxidation-resistant coating 158 may be any suitable oxidation-resistant coating capable of use at high temperatures. As shown in FIG. 4, the oxidation-resistant coating may be disposed on the outer surface 156 of the body 154. Alternatively, the heat transfer member 140 may be uncoated, with the outer surface 156 being the outer surface of the heat transfer member 140.

[0042] In many embodiments, the mold shell can define a shell thickness 160 of about 2 mm to about 25 mm, or such as about 3 mm to about 23 mm, or such as about 4 mm to about 22 mm, or such as about 5 mm to about 21 mm, or such as about 6 mm to about 20 mm. This shell thickness can be thinner than previous designs, which advantageously facilitates heat transfer between the alloy 162 and the heat transfer element 140 when the heat transfer element 140 is in contact with the mold shell 122. For example, the thinner shell thickness 160 advantageously increases the thermal conductivity between the alloy 162 and the heat transfer element 140, resulting in more heat being removed from the alloy 162 by the heat transfer element 140 when in contact with the mold shell 122.

[0043] 5-8 each illustrate a cross-sectional view of an exemplary casting system 100 in accordance with an embodiment of the present disclosure. In particular, each of FIGS. 5-8 illustrates the casting system 100 in a different position. As illustrated, the system 100 may include multiple heat transfer members 140 extending from respective first ends 142 coupled to the system 100 to respective second ends 144. Each heat transfer member 140 is operably coupled to a controller 200 and is operable independently of one another. In such an embodiment, multiple heat transfer members 140 extend from the chill plate 118, one or more heat transfer members 140 extend from the casing (e.g., either the heating zone 114 or the cooling zone 116), and one or more heat transfer members 140 extend from the baffle plate 110 (not shown).

[0044] As shown, FIG. 5 depicts the casing system immediately following the pouring stage, i.e., when the alloy 162 in a liquid state is being poured from the crucible 124 into the mold shell 122. As shown in FIG. 5, after (and / or during) pouring the alloy 162 into the mold shell 122, each heat transfer element 140 may not be in contact with the mold shell 122 (i.e., in a retracted position). Alternatively, as shown in FIG. 6, after (and / or during) pouring the alloy 162 into the mold shell 122, one or more heat transfer elements 140 may be in contact with the mold shell 122. That is, when the mold shell 122 is completely within the cooling zone 116, one or more heat transfer elements 140 may be in contact with the mold shell 122 (at separate locations). 7 illustrates the casing system 100 in a withdrawal stage, in which the shaft 120 is moved vertically to reposition (or move) the mold shells 122 from the heating zone 114 to the cooling zone 116 to solidify the alloy 162. As illustrated, while the mold shells 122 are moving from the heating zone 114 to the cooling zone 116, multiple heat transfer members 140 may each contact different locations of the mold shells 122. In particular, one or more heat transfer members 140 may contact the mold shells 122 in the heating zone 114 (e.g., the upper portions of the mold shells 122), and simultaneously, one or more heat transfer members 140 may contact the mold shells 122 in the cooling zone 116 (e.g., the lower portions of the mold shells 122). 8 illustrates the casing system 100 in a fully withdrawn stage, in which the shaft 120 has moved the mold shell 122 completely from the heating zone 114 to the cooling zone 116 (e.g., by vertically moving the shaft 120, the mold shell is moved from the heating zone 114 to the cooling zone 116 through the opening 111 in the baffle plate 110). As shown in FIG. 8, when the mold shell 122 is completely within the cooling zone 116, one or more heat transfer members 140 may contact the mold shell 122 (at different locations).

[0045] In particular, system 100 may include a first heat transfer member 149, a second heat transfer member 150, a third heat transfer member 151, and a fourth heat transfer member 152. Each of heat transfer members 149, 150, 151, 152 may be actuable independently of one another, thereby enabling heat transfer members 149, 150, 151, 152 to extend, retract, and / or rotate, respectively, to contact mold shell 122 within chamber 108. Each of heat transfer members 149, 150, 151, 152 may extend from a different location within chamber 108. For example, first heat transfer member 149 and fourth heat transfer member 152 may extend from chill plate 118 (e.g., from opposite sides of chill plate 118). The second heat transfer member 150 and the third heat transfer member 151 may extend from the chamber 108 (e.g., the chamber 108 in the heating zone 114 or the cooling zone 116). Alternatively, one or more heat transfer members 140 may extend from the baffle plate 110 (not shown).

[0046] Although Figures 5-8 show a casing system 100 having four heat transfer members 140, it should be understood that the casing system 100 may include any number of heat transfer members 140, and the present disclosure is not limited to a particular number of heat transfer members 140 unless otherwise stated in the claims.

[0047] The material forming the heat transfer member 140 can affect the heat transfer characteristics of the heat transfer member 140. For example, in some embodiments, the heat transfer member 140 can be formed from a material with a high thermal conductivity such that contact between the heat transfer member 140 and the mold shell 122 increases the solidification rate (or thermal gradient) of the alloy 162 (e.g., near the contact location). For example, the heat transfer member 140 can have a higher thermal conductivity than the alloy 162. In particular, the heat transfer member 140 can be formed from (or composed of) one or more of molybdenum alloy, graphite, silicon carbide, and / or a ceramic matrix composite silicon carbide, high-melting point refractory alloy.

[0048] Alternatively, or additionally, the heat transfer member 140 may be formed from a material with low thermal conductivity such that contact between the heat transfer member 140 and the mold shell reduces the solidification rate (or thermal gradient) of the alloy 162 (e.g., near the contact location). For example, the heat transfer member 140 may have a lower thermal conductivity than the alloy 162. In particular, the heat transfer member 140 may be formed from (or consist of) one or more of silica, alumina, zircon, zirconia, or yttria. Furthermore, contact between the heat transfer member 140 and the mold shell 122 may not be necessary for heat retention. For example, in some embodiments, the heat transfer member 140 is thermally coupled to the shell mold 122 via radiation, and the heat transfer member 140 transfers heat to the shell mold 122 via radiation. In such an embodiment, the magnitude of the radiation can be controlled by varying the distance between the heat transfer member 140 and the shell mold 122 (e.g., moving the heat transfer rod 140 closer to the shell mold 122 increases the radiation, and moving the heat transfer member 140 further from the shell mold decreases the radiation).

[0049] In many embodiments, the first heat transfer member 149 may be composed of a first material, the second heat transfer member 150 may be formed from a second material, the third heat transfer member 151 may be formed from a third material, and the fourth heat transfer member 152 may be formed from a fourth material. The first, second, third, and fourth materials may be the same, different, or any combination. For example, the first material may be formed from a material having a high thermal conductivity (such as molybdenum alloy, graphite, silicon carbide, and / or a ceramic matrix composite silicon carbide), and the second material may be formed from a material having a low thermal conductivity (such as silica, alumina, zircon, zirconia, yttria, or chromia).

[0050] Referring now to FIG. 9 , a flow diagram of one embodiment of a method 900 for forming a directionally solidified cast component using a casting system 100 is shown, in accordance with aspects of the present subject matter. Generally, the method 900 is described herein with reference to the casting system 100 and gas turbine 10 described above with reference to FIGS. 1 through 8 . However, those skilled in the art will understand that the disclosed method 900 may generally be utilized in connection with any casting system having any other suitable system configuration. Furthermore, while FIG. 9 depicts steps performed in a particular order for purposes of illustration and description, the methods described herein are not limited to any particular order or arrangement unless otherwise specified in the claims. Those skilled in the art, using the disclosure provided herein, will understand that various steps of the methods disclosed herein can be omitted, rearranged, combined, and / or adapted in various ways without departing from the scope of the present disclosure.

[0051] 9 , the method 900 may include pouring (step 902) the alloy 162 in a liquid state into the mold shell 122. The mold shell 122 may be positioned on the chill plate 118 in the heating zone 114. Prior to pouring (step 902), the alloy 162 is heated to a molten or liquid state in the crucible 124, and once the alloy 162 is in a liquid state, it is poured from the crucible 124 into the mold shell 122. For example, the alloy 162 may be poured through an opening in the tip 126 of the mold shell 122 into the cavity 128 defined by the mold shell 122, such that the alloy 162 fills the cavity 128 defined by the mold shell 122. Alternatively, in some embodiments (not shown), the cavity 128 of the mold shell 122 is filled through a down sprue, and the alloy 162 is injected through the mold shell 122 at a location between the base 125 and the tip 126. The cavity 128 corresponds to the shape of the directionally solidified cast part, and the cavity 128 may have a rotor blade shape having a shank portion 102 and an airfoil portion 104.

[0052] In many embodiments, prior to the infusion step, the method 900 can further include evacuating the chamber 108 with a vacuum system 132. The vacuum system 132 can remove all air from the chamber 108, thereby creating a vacuum. Additionally, in some embodiments, when the mold shell 122 is within the heating zone 114 (e.g., during and / or after the infusion step), an electric heating element 134 can heat the alloy 162 within the mold shell 122 to maintain or maintain the alloy 162 in a liquid state.

[0053] In an exemplary embodiment, method 900 may further include (step 904) moving mold shell 122 from heating zone 114 to cooling zone 116. As a result, alloy 162 transitions from a liquid state to a solid state within mold shell 122 as mold shell 122 moves from heating zone 114 to cooling zone 116. Moving (step 904) may include actuating shaft 120 (e.g., by sending a signal via controller 200) to translate shaft 120 in vertical direction V, thereby moving mold shell 122 from heating zone 114 to cooling zone 116 through opening 111 in baffle plate 110.

[0054] In many embodiments, the method 900 may further include (step 906) thermally coupling the mold shell 122 to the heat transfer member 140. For example, the heat transfer member 140 may extend from a first end 142 coupled to the casting system 100 to a second end 144 (or free end), and the heat transfer member 140 may be movable in any direction within the chamber 108. In this manner, the heat transfer member 140 may be in or out of physical contact (i.e., selectively contacting) with the mold shell 122 at various locations while the alloy 162 is solidifying (e.g., while the alloy is above the solidus temperature), thereby altering (i.e., increasing or decreasing) the local solidification rate of the alloy 162 near the contact locations. This advantageously minimizes particle defects caused by improper solidification (e.g., solidifying too quickly or too slowly) of the alloy 162. Additionally, the heat transfer element 140 allows the casting system 100 to produce parts with more complex shapes without defects.

[0055] 9, thermal coupling at (step 906) further includes the optional step (depicted by the dashed box) at (step 908) of actuating the heat transfer member 140 from a first position out of contact with the mold shell 122 to a second position in contact with the mold shell 122. For example, the heat transfer member 140 can be extended and / or contracted, rotated and / or translated by one or more actuators 201 to move the heat transfer member 140 into and out of contact with the mold shell 122.

[0056] Additionally, in many implementations of the method 900, a solidification front 130 may form between the liquid alloy 164 and the solid alloy 166 within the mold shell 122 while the mold shell 122 is being moved from the heating zone 114 to the cooling zone 116. In such embodiments, the method 900 may (step 910) contact the mold shell 122 with the heat transfer member 140 at or above the solidification front 130 relative to the vertical direction V. In many embodiments, the vertical direction V may be opposite to the direction of gravity. The contact between the heat transfer member 140 and the mold shell 122 may occur in a vertical position where the alloy 162 has not yet completely solidified (e.g., the alloy 162 may be above its solidus temperature). Thus, contacting the heat transfer member 140 with the mold shell 122 in a vertical position where the alloy 162 is above its solidus temperature alters the rate at which the temperature of the alloy 162 is reduced (either decreasing or increasing the rate), thereby favorably affecting the resulting grain structure of the directionally solidified cast part.

[0057] 9 , thermally coupling (step 906) may further include (step 912) contacting the mold shell 122 with the heat transfer member 140 at a first instance and at a first location on the mold shell 122. Additionally, the method 900 may include (step 914) actuating the heat transfer member 140 to move the heat transfer member 140 away from the first location on the mold shell 122. Additionally, the method 900 may include (step 916) contacting the mold shell 122 with the heat transfer member 140 at a second instance and at a second location on the mold shell 122. The second location may be different from the first location. The mold shell 122 may be moved vertically by actuating the shaft 120 from first contacting the mold shell 122 at the first location to second contacting the mold shell 122 at the second location. Additionally, in many implementations, the mold shell 122 may be moved vertically while being contacted by the heat transfer member 140 in a particular location, such that the heat transfer member 140 may move along with the mold shell 122 to maintain contact.

[0058] In many embodiments, thermally coupling (step 906) may further include (step 918) contacting the mold shell 122 with the heat transfer member 140 when the mold shell 122 is within the heating zone 114 (e.g., when completely within the heating zone 114). Additionally, contacting (step 906) may further include (step 920) contacting the mold shell 122 with the heat transfer member 140 when the mold shell 122 is within the cooling zone 116 (e.g., when completely within the cooling zone 116). Additionally, contacting (step 906) may further include (step 922) contacting the mold shell 122 with the heat transfer member 140 while moving the mold shell 122 from the heating zone 114 to the cooling zone 116 (such that the mold shell 122 is partially disposed in both the heating zone 114 and the cooling zone 116).

[0059] In various embodiments, the heat transfer member 140 may be a first heat transfer member 149, and the method 900 may further include contacting a first portion of the mold shell with a first heat transfer member 149 rod to increase a first localized solidification rate of the alloy 162 proximate the first portion. In such embodiments, the method 900 may further include contacting a second portion of the mold shell 122 with a second heat transfer member 150 to decrease a second localized solidification rate of the alloy 162 proximate the second portion. The second portion may be different from the first portion.

[0060] In embodiments where thermal insulation of the alloy 162 is desired, contact between the heat transfer member 140 and the shell mold 122 may not be necessary. For example, in such embodiments, thermal coupling (step 906) may include moving the heat transfer member 140 a radial distance away from the shell mold 122 to thermally couple the heat transfer member 140 to the shell mold 122 without contact via radiation. In such embodiments, the magnitude of radiation may be controlled by varying the radial distance between the heat transfer member 140 and the shell mold 122. For example, moving the heat transfer rod 140 closer to the shell mold 122 may increase radiation, while moving the heat transfer rod 140 farther from the shell mold may decrease radiation. In various embodiments, the radial distance may be up to about 0.5 inches, or between about 0.1 inches and about 0.5 inches, or between about 0.1 inches and about 0.4 inches, or between about 0.2 inches and about 0.3 inches, etc.

[0061] The casting system 100 described herein advantageously provides a conductive and / or radiative heat transfer means during the directional solidification casting process by utilizing a heat transfer member 140. The heat transfer member 140 may or may not be in contact (i.e., selective contact) to provide localized conductive or radiative heat transfer between the heat transfer member 140 and the alloy 162, thereby favorably influencing (increasing or decreasing) the solidification rate of the alloy 162 and minimizing particle defects.

[0062] Examples are used herein to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems, and performing any methods incorporated therein. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are deemed to be within the scope of the claims if they contain structural elements that do not differ from the claim language, or if they contain equivalent structural elements that do not differ insubstantial from the claim language.

[0063] Further aspects of the invention are provided by the subject matter of the following clauses. [Embodiment 1] 1. A method of forming a directionally solidified casting component using a casting system, the casting system comprising a chamber having a heating zone and a cooling zone separated by a baffle plate, the method comprising the steps of pouring an alloy in a liquid state into a mold shell, the mold shell positioned on a chill plate within the heating zone, and moving the mold shell from the heating zone to the cooling zone, whereby the alloy transfers from the liquid state to a solid state within the mold shell while moving the mold shell from the heating zone to the cooling zone. and thermally coupling the mold shell with a heat transfer member. [Embodiment 2] 10. The method of claim 1, wherein thermally coupling the mold shell and the heat transfer member further comprises: contacting the mold shell with the heat transfer member a first instance in at a first location on the mold shell; actuating the heat transfer member out of contact with the mold shell at the first location; and contacting the mold shell with the heat transfer member a second instance at a second location on the mold shell, the second location being different than the first location. [Embodiment 3] 10. The method of any preceding embodiment, wherein thermally coupling the mold shell and the heat transfer member further comprises actuating the heat transfer member from a first position not in contact with the mold shell to a second position in contact with the mold shell. [Embodiment 4] 10. The method of any preceding embodiment, wherein the heat transfer member is formed from a material having a high thermal conductivity such that the contact between the heat transfer member and the mold shell increases a solidification rate of the alloy. [Embodiment 5] 10. The method of any preceding embodiment, wherein the heat transfer member is formed from a material having a low thermal conductivity such that the contact between the heat transfer member and the mold shell decreases a solidification rate of the alloy. [Embodiment 6] 10. The method of any preceding embodiment, wherein thermally coupling the mold shell and the heat transfer member comprises contacting the mold shell with the heat transfer member when the mold shell is in the heating zone. [Embodiment 7] 10. The method of any preceding embodiment, wherein thermally coupling the mold shell and the heat transfer member further comprises contacting the mold shell with the heat transfer member when the mold shell is in the cooling zone. [Embodiment 8] 10. The method of any preceding embodiment, wherein thermally coupling the mold shell and the heat transfer member further comprises contacting the mold shell with the heat transfer member while moving the mold shell from the heating zone into the cooling zone. [Embodiment 9] 10. The method of any preceding embodiment, wherein a solidification front forms within the mold shell between the alloy in the liquid state and the alloy in the solid state while the mold shell is moved from the heating zone to the cooling zone. [Embodiment 10] 10. The method of any preceding embodiment, wherein thermally coupling further comprises contacting the mold shell with the heat transfer member at or above the solidification front. [Embodiment 11] 10. The method of claim 1, wherein the heat transfer member is a first heat transfer member, and wherein the step of thermally coupling further comprises the steps of contacting a first portion of the mold shell with the first heat transfer member to increase a first local solidification rate of the alloy proximate the first portion, and contacting a second portion of the mold shell with a second heat transfer member to decrease a second local solidification rate of the alloy proximate the second portion. [Embodiment 12] 10. The method of any preceding embodiment, wherein the step of thermally coupling further comprises thermally coupling the heat transfer member and the shell mold without contact via radiation by moving the heat transfer member into a radiation distance away from the shell mold. [Embodiment 13] A casting system for forming a directionally solidified casting component, the casting system comprising: a chamber; a baffle plate disposed within the chamber, the chamber and the baffle plate collectively defining a heating zone and a cooling zone, the heating zone and the cooling zone separated by the baffle plate; a chill plate movable between the heating zone and the cooling zone; a mold shell disposed on the chill plate; and a heat transfer member extending from a first end to a second end, the heat transfer member operable between a first position in which the second end is not in contact with the mold shell and a second position in which the second end is in contact with the mold shell. transfer member extending from a first end to a second end,a heat transfer member actuatable between a first position in which the second end is not in contact with the mold shell and a second position in which the second end is in contact with the mold shell; [Embodiment 14] 10. The casting system of any preceding embodiment, wherein the first end is coupled to the chill plate. [Embodiment 15] 10. The casting system of any preceding embodiment, wherein the first end is coupled to the chamber. [Embodiment 16] 10. The casting system of any preceding embodiment, wherein the heat transfer member is composed of one or more of molybdenum alloy, high-melting point refractory alloy, graphite, silicon carbide, or a ceramic matrix composite silicon carbide. [Embodiment 17] 10. The casting system of any of the preceding embodiments, wherein the heat transfer member is composed of one or more of silica, alumina, zircon, zirconia, chromia, or yttria. [Embodiment 18] 10. The casting system of any preceding embodiment, wherein the heat transfer member includes an oxidation resistant coating. [Embodiment 19] 10. The casting system of any preceding embodiment, wherein the mold shell defines a shell thickness of between about 2 mm and about 25 mm. [Embodiment 20] 10. The casting system of any preceding embodiment, wherein the heat transfer member is a first heat transfer member and the system further comprises a second heat transfer member. [Explanation of symbols]

[0064] 10: Gas turbine 12: Inlet section 14: Compressor section 16: Combustor section 18: Turbine section 20: Exhaust section 22: Shaft 24: Rotor disk 26: Rotor blades 28: Rotor disk 30: Rotor blades 31: Outer casing 32: Hot gas path 34: Combustion gases 100: Casting system 102: Shank portion 104: Airfoil portion 108: Chamber 110: Baffle plate 111: Opening 112: Internal volume 114: Heating zone 116: Cooling zone 118: Chill plate 120: Shaft 122: Mold shell / shell mold 124: Crucible 125: Base 126: Tip 128: Cavity 130: Solidification front 132: Vacuum system 134: Electric heating element 140: Heat transfer member 142: First end 144: Second end 149: First heat transfer member 150: Second heat transfer member 151: Third heat transfer member 152: Fourth heat transfer member 154: Main body 156: Outer surface 158: Oxidation-resistant coating 160: Shell thickness 162: Alloy 164: Alloy in liquid state 166: Alloy in solid state 200: Controller 201: Linear actuator 202: Processor 204: Memory device 206, 218: Communication module V: Vertical direction L: Longitudinal direction T: Lateral direction

Claims

1. 1. A method of forming a directionally solidified cast component using a casting system, the casting system including a chamber having a heating zone and a cooling zone separated by a baffle plate, the method comprising: pouring the alloy in a liquid state into a mold shell, the mold shell being positioned on a chill plate within a heating zone; moving the mold shell from the heating zone to the cooling zone, whereby the alloy transitions from a liquid state to a solid state within the mold shell while moving the mold shell from the heating zone to the cooling zone; and thermally coupling the mold shell with a heat transfer member.

2. The step of thermally coupling the mold shell and the heat transfer member further includes: contacting the mold shell with a heat transfer member at a first instance at a first location on the mold shell; activating the heat transfer member in a first position so that the heat transfer member is not in contact with the mold shell; and contacting the mold shell with the heat transfer member at a second instance at a second location on the mold shell, the second location being different from the first location.

3. The step of thermally coupling the mold shell and the heat transfer member further includes:

10. The method of claim 1, including actuating the heat transfer member from a first position out of contact with the mold shell to a second position in contact with the mold shell.

4. 10. The method of claim 1, wherein the heat transfer member is formed from a material with high thermal conductivity such that contact between the heat transfer member and the mold shell increases the solidification rate of the alloy.

5. 10. The method of claim 1, wherein the heat transfer member is formed from a material with low thermal conductivity such that contact between the heat transfer member and the mold shell reduces the solidification rate of the alloy.

6. The method of claim 1 , wherein the step of thermally coupling the mold shell and the heat transfer member further comprises contacting the mold shell and the heat transfer member while the mold shell is in the heating zone.

7. The step of thermally coupling the mold shell and the heat transfer member further includes: The method of claim 1 including contacting the mold shell with a heat transfer member while the mold shell is in the cooling zone.

8. The step of thermally coupling the mold shell and the heat transfer member further includes: The method of claim 1 including contacting the mold shell with a heat transfer member while moving the mold shell from the heating zone to the cooling zone.

9. The method of claim 1 , wherein a solidification front forms within the mold shell between the alloy in a liquid state and the alloy in a solid state while the mold shell moves from the heating zone to the cooling zone.

10. The step of thermally bonding further comprises:

10. The method of claim 9, including contacting the mold shell with a heat transfer member at or above the solidification front.

11. The heat transfer member may be a first heat transfer member, and the step of thermally coupling may further include: contacting a first portion of the mold shell with a first heat transfer member to increase a first localized solidification rate of the alloy proximate the first portion; and contacting a second portion of the mold shell with a second heat transfer member to reduce a second localized solidification rate of the alloy adjacent the second portion.

12. The step of thermally bonding further comprises:

10. The method of claim 1, further comprising the step of thermally coupling the heat transfer member and the shell mold without contact via radiation by moving the heat transfer member a radial distance away from the shell mold.

13. 1. A casting system for forming a directionally solidified cast component, comprising: a chamber; a baffle plate disposed within the chamber, the chamber and the baffle plate together defining a heating zone and a cooling zone, the heating zone and the cooling zone being separated by the baffle plate; a chill plate movable between a heating zone and a cooling zone; a mold shell disposed on a chill plate; a heat transfer member extending from a first end to a second end; wherein the heat transfer member is operable between a first position in which the second end is not in contact with the mold shell and a second position in which the second end is in contact with the mold shell.

14. The casting system of claim 13 , wherein the first end is coupled to a chill plate.

15. The casting system of claim 13 , wherein the first end is coupled to the chamber.

16. The casting system of claim 13 , wherein the heat transfer member is comprised of one or more of a molybdenum alloy, a refractory alloy, graphite, silicon carbide, or a ceramic matrix composite silicon carbide.

17. The casting system of claim 13 , wherein the heat transfer member is comprised of one or more of silica, alumina, zircon, zirconia, chromia, or yttria.

18. The casting system of claim 13 , wherein the heat transfer member includes an oxidation resistant coating.

19. 14. The casting system of claim 13, wherein the mold shell has a shell thickness ranging from about 2 mm to about 25 mm.

20. The casting system of claim 13 , wherein the heat transfer member is a first heat transfer member, and the system further includes a second heat transfer member.

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