Heat extraction or retention during directional solidification of cast parts

Abstract

A method of forming a directionally solidified cast part using a casting system is provided. The casting system includes a chamber having a heating zone and a cooling zone separated by a baffle. The method includes pouring a liquid alloy into a mold shell. The mold shell is positioned on the cooling plate within the heating zone. The method further includes moving the mold shell from the heating zone into a cooling zone. 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. The method further includes contacting the mold shell with the heat transfer member.

Description

Technical Field

[0001] The present invention relates generally to materials and processes for producing directionally solidified castings, and 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. Background Art

[0002] Components of gas turbines, such as blades, impellers, and combustor components, are typically formed of nickel, cobalt, or iron-based superalloys characterized by having desirable mechanical properties at turbine operating temperatures. Because the efficiency of a gas turbine depends on its operating temperature, components that can withstand higher temperatures are needed, and in particular turbine blades, nozzles, combustor components, and other hot gas path components. As material requirements for gas turbine components increase, various processing methods and alloy compositions have been used to enhance the mechanical, physical, and environmental properties of components formed from superalloys. For example, blades, nozzles, and other components employed in demanding applications are typically cast by directional casting techniques to have a DS or SX microstructure, characterized by crystal orientation or growth direction in a selected direction to produce a columnar polycrystalline or single crystal article.

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

[0004] During the directional solidification process of geometrically complex components, grain defects can occur due to localized hot spots that fail to cool at the same rate as the rest of the component.

[0005] In order to prevent grain defects during DS casting, various methods of increasing thermal gradient and cooling rate are reported in the prior art, including higher mold heating temperature, higher melt superheat, gas cooling, liquid metal cooling, sealing baffle control, alloy modification, embedding graphite on the outer surface of the shell to obtain high local thermal conductivity. The embedded graphite is exposed to radiant heat and therefore has little effect on heat extraction. It is a stationary piece attached to the shell throughout the casting process. Heat extraction cannot be temporarily controlled with respect to the solidification moment at a specific location of the cast part. As the next generation of heavy industrial gas turbines (IGTs) become larger in size, the turbine blades are also becoming significantly taller, with more complex shapes than smaller IGT blades and aerojet engine blades. Larger casting sizes result in lower thermal gradients caused by a large amount of latent heat of fusion, and therefore preventing grain defects and maintaining high yields is more challenging.

[0006] Therefore, improved systems and methods for cooling cast components during a directional solidification process are desirable and would be appreciated in the art. Summary of the invention

[0007] Aspects and advantages of casting systems and methods according to the present disclosure will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the technology.

[0008] According to one embodiment, a method of forming a directionally solidified cast component using a casting system is provided. The casting system includes a chamber having a heating zone and a cooling zone separated by a baffle. The method includes pouring a liquid alloy into a mold shell. The mold shell is positioned on a cooling plate in the heating zone. The method also includes moving the mold shell from the heating zone to the cooling zone. While moving the mold shell from the heating zone to the cooling zone, the alloy changes from a liquid state to a solid state in the mold shell. The method also includes contacting the mold shell with a heat transfer member.

[0009] 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 disposed in the chamber. The chamber and the baffle together define a heating zone and a cooling zone. The heating zone and the cooling zone are separated by the baffle. The casting system also includes a cooling plate capable of moving between the heating zone and the cooling zone. The casting system also includes a mold shell disposed on the cooling plate. The casting system also includes a heat transfer member extending from a first end to a second end. The heat transfer member can be actuated between a first position and a second position, in which the second end is not in contact with the mold shell in the first position and in which the second end is in contact with the mold shell in the second position.

[0010] These and other features, aspects and advantages of the casting system and method of the present invention will become better understood with reference to 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 invention and, together with the description, serve to explain the principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] This specification sets forth a complete and enabling disclosure of the casting system and method of the present invention, including the best mode of making and using the system and method of the present invention, to one of ordinary skill in the art, with reference to the accompanying drawings, wherein:

[0012] Figure 1 is a schematic diagram of a turbine according to an embodiment of the present disclosure;

[0013] Figure 2 shows a cross-sectional view of a casting system for forming a directionally solidified cast component according to an embodiment of the present disclosure;

[0014] Figure 3 shows a cross-sectional view of a casting system for forming a directionally solidified cast component according to an embodiment of the present disclosure;

[0015] Figure 4 shows a cross-sectional view of a casting system for forming a directionally solidified cast component according to an embodiment of the present disclosure;

[0016] Figure 5 shows a cross-sectional view of a casting system for forming a directionally solidified cast component according to an embodiment of the present disclosure;

[0017] Figure 6 shows a cross-sectional view of a casting system for forming a directionally solidified cast component according to an embodiment of the present disclosure;

[0018] Figure 7 shows a cross-sectional view of a casting system for forming a directionally solidified cast component according to an embodiment of the present disclosure;

[0019] Figure 8 shows a cross-sectional view of a casting system for forming a directionally solidified cast component according to an embodiment of the present disclosure; and

[0020] Fig. 9 is a flow chart of one embodiment of a method of forming a directionally solidified cast component using a casting system according to embodiments of the present disclosure. DETAILED DESCRIPTION

[0021] Reference will now be made in detail to embodiments of the casting system and method of the present invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the present invention, rather than limitation of the present invention. In fact, it will be apparent to those skilled in the art that modifications and variations may be made in the present invention without departing from the scope or spirit of the present invention as protected by the claims. For example, a feature illustrated or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, the present disclosure is intended to cover these modifications and variations that fall within the scope of the appended claims and their equivalents.

[0022] 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. In addition, unless otherwise specifically stated, all embodiments described herein should be considered exemplary.

[0023] The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar components of the present invention. As used herein, the terms "first," "second," and "third" are used interchangeably to distinguish one component from another and are not intended to indicate the position or importance of the various components.

[0024] The term "fluid" may be a gas or a liquid. The term "fluid communication" means that a fluid is able to connect between designated areas.

[0025] As used herein, the terms "upstream" (or "upward") and "downstream" (or "downward") refer to relative directions relative to the flow of a fluid in a fluid pathway. For example, "upstream" refers to the direction from which the fluid is flowing, and "downstream" refers to the direction toward which the fluid is flowing. However, the terms "upstream" and "downstream" as used herein may also refer to current flow. The term "radially" refers to a relative direction that is substantially perpendicular to an axial centerline of a particular component, the term "axially" refers to a relative direction that is substantially parallel and / or coaxially aligned with an axial centerline of a particular component, and the term "circumferentially" refers to a relative direction extending around the axial centerline of a particular component.

[0026] Terms with approximate meanings (such as "about", "approximately", "substantially" and "substantially") are not limited to the exact values ​​specified. In at least some cases, approximate language may correspond to the accuracy of an instrument used to measure a value, or the accuracy of a method or machine used to construct or manufacture a component and / or system. In at least some cases, approximate language may correspond to the accuracy of an instrument used to measure a value, or the accuracy of a method or machine used to construct or manufacture a component and / or system. For example, approximate language may refer to a tolerance of 1%, 2%, 4%, 5%, 10%, 15% or 20% in an individual value, a range of values, and / or an end value of a range of defined values. When used in the context of an angle or direction, such terms are included within ten degrees greater than or less than the angle or direction. For example, "substantially vertical" includes directions within ten degrees of vertical in any direction (e.g., clockwise or counterclockwise).

[0027] Unless otherwise stated herein, the terms "coupled," "fixed," "attached to," and the like refer to direct coupling, fixing, or attachment, as well as indirect coupling, fixing, or attachment through one or more intermediate components or features. As used herein, the terms "include," "comprise," "include," "have," or any other variation thereof, are intended to cover non-exclusive inclusions. For example, a process, method, article, or device that includes a list of features is not necessarily limited to those features, but may include other features that are not expressly listed or inherent to such process, method, article, or device. In addition, unless expressly stated to the contrary, "or" refers to an inclusive or and not an exclusive or. For example, condition A or B is satisfied by any one of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); and both A and B are true (or exist).

[0028] Here and throughout the specification and claims, unless context or language indicates otherwise, range limitations are combined and interchanged, such ranges are identified and include all sub-ranges contained therein. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other.

[0029] Now referring to the accompanying drawings, Figure 1 A schematic diagram of one embodiment of a turbine is shown, which in the illustrated embodiment is a gas turbine 10. Although an industrial or land-based gas turbine is shown and described herein, the present disclosure is not limited to land-based and / or industrial gas turbines unless otherwise indicated in the claims. For example, the present invention as described herein can be used for any type of turbine, including but not limited to a steam turbine, an aircraft gas turbine, or a marine gas turbine.

[0030] As shown, the gas turbine 10 generally includes an inlet section 12, a compressor section 14 disposed downstream of the inlet section 12, a plurality of combustors (not shown) within a combustor section 16 disposed downstream of the compressor section 14, a turbine section 18 disposed downstream of the combustor section 16, and an exhaust section 20 disposed downstream of the turbine section 18. In addition, the gas turbine 10 may include one or more shafts 22 coupled between the compressor section 14 and the turbine section 18.

[0031] The compressor section 14 may generally include 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, in turn, may be coupled to or form part of a shaft 22 extending through the compressor section 14.

[0032] The turbine section 18 may generally 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, in turn, may be coupled to or form a portion of a shaft 22 extending through the turbine section 18. The turbine section 18 also includes an outer casing 31 that circumferentially surrounds a portion of the shaft 22 and the rotor blades 30, thereby at least partially defining a hot gas path 32 through the turbine section 18.

[0033] During operation, a working fluid, such as air, flows through the inlet section 12 and into the compressor section 14, where the air is gradually compressed, thereby providing pressurized air to the combustors of the compressor section 16. The pressurized air is mixed with fuel and combusted within each combustor to produce combustion gases 34. The combustion gases 34 flow from the combustor section 16 through a hot gas path 32 into the turbine section 18, where energy (kinetic energy and / or thermal energy) is transferred from the combustion gases 34 to the rotor blades 30, causing the shaft 22 to rotate. The mechanical rotational energy can then be used to power the compressor section 14 and / or generate electricity. The combustion gases 34 leaving the turbine section 18 can then be discharged from the gas turbine 10 via the exhaust section 20.

[0034] Reference now Figures 2 to 8, a cross-sectional view of a casting system 100 for forming a directionally solidified cast component is shown according to an embodiment of the present disclosure. As will be explained in more detail below, the directionally solidified cast component can be formed from a molten alloy solidified in a mold shell 122. In an exemplary embodiment, the directionally solidified cast component can be a turbine component (such as a rotor blade, a stator impeller, a fuel nozzle, etc.). For example, the directionally solidified cast component can be a rotor blade, such that the cast component includes a shank and an airfoil extending from the shank. In this way, the mold shell 122 can have a shank portion 102 and an airfoil portion 104 corresponding to the shape of the shank and the airfoil of a turbine rotor blade. The casting system 100 can define a direction having a vertical direction V, a longitudinal direction L, and a transverse direction T (not shown, but extending to Figure 2 The vertical direction V, the longitudinal direction L and the transverse direction T may be perpendicular to each other.

[0035] As shown, the casting system 100 includes a chamber 108 and a baffle 110 disposed within the chamber 108. For example, the chamber 108 can be a solid structure defining an interior volume 112 (i.e., as used herein, the term "chamber" refers to a solid wall defining an interior volume). The baffle 110 can separate the interior volume 112 into a heating zone 114 and a cooling zone 116. For example, the chamber 108 and the baffle 110 can together define the heating zone 114 and the cooling zone 116. The heating zone 114 and the cooling zone 116 can be separated by the baffle 110 such that a first side of the baffle 110 defines the heating zone 114 and a second side of the baffle 110 defines the cooling zone 116.

[0036] The casting system 100 may also include a cooling plate 118 that is movable (e.g., vertically movable) between the heating zone 114 and the cooling zone 116. For example, the cooling plate 118 may be coupled to the shaft 120, and the shaft 120 may be actuated in the vertical direction V (e.g., via one or more linear actuators 201, which are represented by the circle "A"). In various embodiments (not shown), the cooling plate 118 may be a water-cooled cooling plate 118. For example, the cooling plate 118 may have one or more water cooling circuits defined therein that circulate water through the cooling plate 118. Additionally, in many embodiments, the cooling plate 118 may be composed of a highly thermally conductive material, such as copper or a copper alloy.

[0037] The casting system 100 may also include a mold shell 122 disposed on the cooling plate 118. For example, the mold shell 122 may extend vertically from a base 125 disposed on the cooling plate 118 to a tip 126. The mold shell 122 may define a cavity 128 into which a liquid alloy 162 (i.e., liquid alloy 164) may be poured in the heating zone 114 (e.g., from the crucible 124). Subsequently, the mold shell 122 may be moved (e.g., by actuating the shaft 120 to move the cooling plate 118 and the mold shell 122 from the heating zone 114 to the cooling zone 116). When the mold shell 122 is moved to the cooling zone 116, the alloy may solidify (i.e., directionally solidify) in the mold shell 122 along a vertical direction V from the base 125 to the tip 126 of the mold shell 122 into a solid state (i.e., solid alloy 166), thereby forming a directionally solidified cast component. For example, as the mold shell 122 moves from the heating zone 114 and the cooling zone 116, the alloy 162 can transform from a liquid to a solid state. Figures 2 to 8 As shown, the horizontal dashed lines within the mold shell 122 may represent the alloy 162 in a liquid state (eg, liquid alloy 164 ), and the cross-hatched lines within the mold shell 122 may represent the alloy 162 in a solid state (eg, solid alloy 166 ).

[0038] While the mold 122 is moved from the heating zone 114 to the cooling zone 116, a solidification front 130 may be formed within the mold 122 between the alloy 162 (164) in a liquid state and the alloy 162 (166) in a solid state. Although 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 122. More specifically, the solidification front 130 may be a portion of the alloy 162 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. In addition, 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 is completely solid, and the temperature at the solidification line (and above relative to the vertical direction V) may be greater than the solidus temperature.

[0039] In many embodiments, the chamber 108 can be a vacuum chamber that can be evacuated by the vacuum system 132. The electric heating element 134 can be disposed in the heating zone 114 to maintain the alloy 162 within the mold 122 above the solidus temperature (e.g., to maintain the liquid alloy 164) when in the heating zone 114. For example, when the electric heating element 134 is positioned in the heating zone 114, it can surround the mold 122. The baffle 110 can define an opening 111 through which the mold 122 moves between the heating zone 114 and the cooling zone 116. In various embodiments, the baffle 110 is positioned on top of the cooling plate 118. The opening 111 can have a diameter that is approximately the size of the maximum upper and lower projected area of ​​the mold 122.

[0040] To produce a directionally solidified cast component, the mold shell 122 is inserted into the heating zone 114 by moving the shaft 120 vertically upward. The liquid alloy 164 is poured into the mold shell 122 through the crucible 124, and then the shaft is moved vertically downward so that the mold shell 122 passes through the opening 111 from the heating zone 114 to the cooling zone 116. Therefore, the alloy 162 is transformed from a liquid state to a solid state in the vertical direction V. For example, the alloy 162 first solidifies at the base 125 of the mold shell 122, and the solidification front moves vertically upward to the tip 126 of the mold shell 122.

[0041] Due to the geometric complexity of the directionally solidified cast component, various portions of the alloy 162 within the mold shell 122 may not solidify at the same rate (e.g., some portions may solidify faster / slower than other portions), which may result in one or more component defects. Therefore, the exemplary casting system 100 described herein includes a heat transfer member 140 for increasing or decreasing the magnitude and direction of the thermal gradient and the solidification rate of the alloy at various portions to prevent the formation of defects. The heat transfer member 140 can 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 110 (e.g., a hole separate from the opening 111).

[0042] like Figures 2 to 8 As shown, the casting system 100 may also include a controller 200, which is shown as a block diagram to illustrate suitable components that may be included in the controller 200. As shown, the controller 200 may include: one or more processors 202 and associated memory devices 204, which are configured to perform various computer-implemented functions (e.g., perform methods, steps, calculations, etc. and store related data as disclosed herein). In addition, the controller 200 may also include a communication module 206 to facilitate 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 communication module 218 can communicate with the actuator 201 to allow 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 can be communicatively coupled to the communication module 206 using any suitable means (e.g., a wired connection or a wireless connection using any suitable wireless communication protocol known in the art).

[0043] As used herein, the term "processor" refers not only to what is known in the art as an integrated circuit included in a computer, but also to controllers, microcontrollers, microcomputers, programmable logic controllers (PLCs), application specific integrated circuits, and other programmable circuits. In addition, the 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 memory (CD-ROM), magneto-optical disks (MOD), digital versatile disks (DVD), and / or other suitable memory elements. Such memory devices 204 may generally be configured to store suitable computer-readable instructions that, when implemented by the processor 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 with the crucible 124; moving the mold shell 122 from the heating zone 114 to the cooling zone 116 with the shaft 120; and contacting the mold shell 122 with the heat transfer member 140.

[0044] The heat transfer member 140 may extend from the first end 142 to the second end 144. The heat transfer member 140 may be movable in any one of the vertical direction V, the longitudinal direction L, and / or the transverse direction T. For example, the heat transfer member 140 may be coupled to the actuator 201, and the actuator 201 may be operably coupled to the controller 200, so that the controller 200 may adjust the position of the heat transfer member 140 by operating the actuator 201. In addition, the heat transfer member 140 may be extendable so that the length of the heat transfer member 140 may be increased / decreased. For example, the heat transfer member 140 may have a telescopic structure that can be extended by the actuator 201. The actuator 201 may include a linear actuator and / or a rotary actuator so that the heat transfer member 140 may be movable / rotatable in any one of the vertical direction V, the longitudinal direction L, and the transverse direction T.

[0045] like Figure 2 and Figure 3 As shown together, the heat transfer member 140 can be in the first position ( Figure 2 ) and the second position ( Figure 3 ), in the first position, the second end 144 is not in contact with the mold shell 122, and in the second position, the second end is in contact with the mold shell 122. It should be understood that although Figure 3 The heat transfer member 140 is shown in contact with one particular portion of the form 122 , but the heat transfer member 140 may be actuated to contact any portion of the form 122 (eg, an exterior surface of the form 122 ).

[0046] In many embodiments, the first end 142 of the heat transfer member 140 can be coupled to the cooling plate 118. For example, the first end 142 of the heat transfer member 140 can be pivotally coupled to the cooling plate 118 such that the first end 142 can rotate relative to the cooling plate 118. Coupling the first end 142 of the heat transfer member 140 to the cooling plate 118 can advantageously increase the efficiency of the heat transfer member 140 by increasing the thermal gradient between the heat transfer member 140 and the mold 122. For example, the cooling plate 118 can cool the heat transfer member 140, thereby increasing the temperature difference between the heat transfer member 140 and the mold 122, which can allow the heat transfer member to increase the solidification rate of the alloy 162 within the mold 122 near where the heat transfer member 140 contacts the mold 122.

[0047] Alternatively or additionally, the first end 142 of the heat transfer member 140 can be coupled to the chamber 108. For example, the first end 142 of the heat transfer member 140 can be pivotally coupled to the chamber 108 such that the first end 142 can rotate relative to the chamber 108. In particular, the first end 142 of the heat transfer member 140 can be coupled to the chamber 108 in 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, which can allow the heat transfer member to reduce 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. Additionally, for heat retention purposes of the heat transfer member 140 , the heat transfer member 140 may be coupled to the shell mold 122 via radiant heat, such that the heat transfer member 140 may reduce a thermal gradient between the heat transfer member 140 and the shell mold 122 without contacting the shell mold 122 .

[0048] In contrast, coupling the first end 142 of the heat transfer member 140 to the chamber 108 in the cooling zone 116 can 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 cooling zone 116 can cool the heat transfer member 140, thereby increasing the temperature difference between the heat transfer member 140 and the mold shell 122, which can allow 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. In this way, depending at least in part on the location to which the first end 142 of the heat transfer member 140 is attached, the function of the heat transfer member 140 can 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.

[0049] Figure 4 An enlarged cross-sectional view of a heat transfer member 140 according to an embodiment of the present disclosure is shown. In particular, Figure 4 Shown by Figure 3 1 is an enlarged cross-sectional view of the details depicted by the dashed lines in FIG. As shown, the heat transfer member 140 may include a body 154 defining an outer surface 156. In addition, in many embodiments, the heat transfer member 140 may include an anti-oxidation coating 158. The anti-oxidation coating 158 may be any suitable anti-oxidation coating capable of being used at high temperatures. Figure 4 As shown, the anti-oxidation coating can be disposed on the outer surface 156 of the body 154. Alternatively, the heat transfer member 140 can be uncoated, such that the outer surface 156 is the outer surface of the heat transfer member 140.

[0050] In many embodiments, the formwork can define a shell thickness 160 between about 2 mm and about 25 mm, or such as between about 3 mm and about 23 mm, or such as between about 4 mm and about 22 mm, or such as between about 5 mm and about 21 mm, or such as between about 6 mm and about 20 mm. This shell thickness can be less than previous designs, which advantageously facilitates heat transfer between the alloy 162 and the heat transfer member 140 when the heat transfer member 140 is in contact with the formwork 122. For example, a small shell thickness 160 advantageously increases the thermal conductivity between the alloy 162 and the heat transfer member 140, such that more heat is removed from the alloy 162 by the heat transfer member 140 during contact with the formwork 122.

[0051] Figures 5 to 8 Each shows a cross-sectional view of an exemplary casting system 100 according to an embodiment of the present disclosure. In particular, Figures 5 to 8 Each shows a casting system 100 in a different position. As shown, the system 100 may include a plurality of heat transfer members 140, each extending from a respective first end 142 coupled to the system 100 to a respective second end 144. Each heat transfer member 140 may be operably coupled to the controller 200 and may be independently actuated relative to each other. In such embodiments, the plurality of heat transfer members 140 may extend from the cooling plate 118, one or more heat transfer members 140 may extend from the housing (e.g., in the heating zone 114 or the cooling zone 116), and one or more heat transfer members 140 may extend from the baffle 110 (not shown).

[0052] As shown in the figure, Figure 5 The shell system is shown immediately after the pouring stage. That is, the liquid alloy 162 has been poured from the crucible 124 into the mold shell 122. Figure 5 As shown, after (and / or during) pouring the alloy 162 into the mold shell 122, each heat transfer member 140 may not be in contact with the mold shell 122 (i.e., in a retracted position). Figure 6As shown, after (and / or during) pouring the alloy 162 into the mold 122, one or more of the heat transfer members 140 may contact the mold 122. That is, when the mold 122 is completely within the cooling zone 116, one or more of the heat transfer members 140 may contact the mold 122 (at separate locations). Figure 7 The housing system 100 is shown in a removal stage, wherein the shaft 120 is moved vertically to reposition (or translate) the mold shell 122 from the heating zone 114 to the cooling zone 116 in order to solidify the alloy 162. As shown, while the mold shell 122 is being translated from the heating zone 114 to the cooling zone 116, the plurality of heat transfer members 140 may each contact separate locations of the mold shell 122. In particular, one or more heat transfer members 140 may contact the mold shell 122 (e.g., the top portion of the mold shell 122) in the heating zone 114, and simultaneously, one or more heat transfer members 140 may contact the mold shell 122 (e.g., the bottom portion of the mold shell 122) in the cooling zone 116. Figure 8 The housing system 100 is shown in a fully removed stage, wherein the shaft 120 has completely removed the form 122 from the heating zone 114 into the cooling zone 116 (e.g., by vertically translating the shaft 120 to move the form from the heating zone 114 into the cooling zone 116 through the opening 111 in the baffle 110). Figure 8 As shown, one or more of the heat transfer members 140 may contact the form 122 (at separate locations) when the form 122 is fully within the cooling zone 116 .

[0053] In particular, the 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 the heat transfer members 149, 150, 151, 152 may be independently actuated relative to each other so that the heat transfer members 149, 150, 151, 152 may each be extended, retracted, and / or rotated to contact the mold shell 122 within the chamber 108. Each of the heat transfer members 149, 150, 151, 152 may extend from a different location within the chamber 108. For example, the first heat transfer member 149 and the fourth heat transfer member 152 may extend from the cooling plate 118 (e.g., from opposite sides of the cooling plate 118). The second heat transfer member 150 and the third heat transfer member 151 may extend from the chamber 108 (such as from the chamber 108 in the heating zone 114 or the cooling zone 116). Alternatively, one or more of the heat transfer members 140 may extend from the baffle 110 (not shown).

[0054] Although Figures 5 to 8The housing system 100 is shown with four heat transfer members 140 , but it should be understood that the housing system 100 may include any number of heat transfer members 140 and the present disclosure should not be limited to any particular number of heat transfer members 140 unless expressly recited in the claims.

[0055] The material from which the heat transfer member 140 is formed may affect the heat transfer performance of the heat transfer member 140. For example, in some embodiments, the heat transfer member 140 may be formed of a material having a high thermal conductivity such that the 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 may have a higher thermal conductivity than the alloy 162. In particular, the heat transfer member 140 may be formed of (or consist of) one or more of a molybdenum alloy, graphite, silicon carbide and / or ceramic matrix composite silicon carbide, and a high melting point refractory alloy.

[0056] Alternatively or in addition, the heat transfer member 140 may be formed of a material having a low thermal conductivity such that contact between the heat transfer member 140 and the shell mold 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 of (or consist of) one or more of silica, alumina, zircon, zirconia, or yttria. Additionally, contact between the heat transfer member 140 and the shell mold 122 may not be necessary for heat retention. For example, in some implementations, the heat transfer member 140 may be coupled to the shell mold 122 via radiant heat such that the heat transfer member 140 transfers heat to the shell mold 122 via radiation. In such implementations, the amount of radiation can be controlled by changing 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 can increase radiation, and moving the heat transfer rod 140 farther from the shell mold can reduce radiation).

[0057] In many embodiments, the first heat transfer member 149 may be composed of a first material, and the second heat transfer member 150 may be formed of a second material, the third heat transfer member 151 may be formed of a third material, and the fourth heat transfer member 152 may be formed of a fourth material. The first material, the second material, the third material, and the fourth material may be the same, different, or any combination. For example, the first material may be formed of a material having a high thermal conductivity (such as a molybdenum alloy, graphite, silicon carbide, and / or ceramic matrix composite silicon carbide), and the second material may be formed of a material having a low thermal conductivity (such as silicon dioxide, aluminum oxide, zircon, zirconium oxide, yttrium oxide, or chromium oxide).

[0058] Reference now Fig. 9, a flow chart of one embodiment of a method 900 of forming a directionally solidified cast component using a casting system 100 is shown in accordance with aspects of the present subject matter. In general, reference will be made herein to the above references Figures 1 to 8 The method 900 is described with reference to the casting system 100 and the gas turbine 10 described herein. However, one of ordinary skill in the art will appreciate that the disclosed method 900 may generally be used in conjunction with any casting system having any other suitable system configuration. Fig. 9 The steps performed in a particular order are depicted for purposes of illustration and discussion, but the methods discussed herein are not limited to any particular order or arrangement unless otherwise specified in the claims. Those skilled in the art will understand using the disclosure provided herein that the various steps of the methods disclosed herein may be omitted, rearranged, combined and / or adjusted in various ways without departing from the scope of the present disclosure.

[0059] like Fig. 9 As shown, the method 900 may include pouring a liquid alloy 162 into the mold shell 122 at (902). The mold shell 122 may be positioned on the cooling plate 118 within the heating zone 114. Prior to pouring at (902), the alloy 162 may be heated in the crucible 124 to a molten or liquid state, and once the alloy 162 is in a liquid state, the alloy 162 may be poured into the mold shell 122 through the crucible 124. For example, the alloy 162 may be poured into the cavity 128 defined by the mold shell 122 through an opening at the tip 126 of 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 may be filled via a downward sprue, such that the alloy 162 is poured through the mold shell 122 to a location between the base 125 and the tip 126. The cavity 128 may correspond in shape to the directionally solidified cast component such that the cavity 128 may have a rotor blade shape having a shank portion 102 and an airfoil portion 104 .

[0060] In many implementations, prior to the pouring step, the method 900 can further include evacuating the chamber 108 with the vacuum system 132. The vacuum system 132 can remove all air from the chamber 108, thereby creating a vacuum. Additionally, in some implementations, the electric heating element 134 can heat the alloy 162 within the mold 122 while the mold 122 is within the heating zone 114 (e.g., during the pouring step and / or after the pouring step) to keep or maintain the alloy 162 in a liquid state.

[0061] In an exemplary implementation, the method 900 may further include moving the mold shell 122 from the heating zone 114 to the cooling zone 116 at (904). Thus, while the mold shell 122 is moved from the heating zone 114 to the cooling zone 116, the alloy 162 is transformed from a liquid state to a solid state within the mold shell 122. The movement at (904) may include actuating the shaft 120 (e.g., by sending a signal with the controller 200) to translate the shaft 120 in the vertical direction V, thereby moving the mold shell from the heating zone 114 to the cooling zone 116 through the opening 111 in the baffle 110.

[0062] In many implementations, the method 900 may also include thermally coupling the mold shell 122 to the heat transfer member 140 at (906). 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 a 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 physically contact and not contact (i.e., selectively contact) the mold shell 122 in various positions while the alloy 162 is solidifying (e.g., when the alloy is above the solidus temperature), thereby changing (i.e., increasing or decreasing) the local solidification rate of the alloy 162 near the contact position. This may advantageously minimize grain defects caused by improper solidification of the alloy 162 (i.e., solidification occurring too quickly or too slowly). Additionally, the heat transfer member 140 may allow the casting system 100 to produce parts with more complex geometries without defects.

[0063] In many embodiments, such as Fig. 9 As shown in , the thermal coupling at (906) may also include an optional step (as indicated by the dashed box) at (908) of actuating the heat transfer member 140 from a first position not in contact with the mold shell 122 to a second position in contact with the mold shell 122. For example, the heat transfer member 140 may be extended and / or retracted, 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.

[0064] Additionally, in many implementations of the method 900, when the mold 122 is moved from the heating zone 114 to the cooling zone 116, a solidification front 130 may be formed within the mold 122 between the liquid alloy 164 and the solid alloy 166. In such implementations, the method 900 may contact the mold 122 with the heat transfer member 140 at (910) 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 122 may occur at a vertical position where the alloy 162 has not yet fully solidified (e.g., the alloy 162 may be above the solidus temperature). Therefore, the contact of the heat transfer member 140 with the mold 122 at a vertical position where the alloy 162 is above the solidus temperature will change the rate of temperature drop of the alloy 162 (either reduce the rate or increase the rate), thereby beneficially affecting the resulting grain structure of the directionally solidified cast component.

[0065] In various specific implementations, such as Fig. 9 As shown, the thermal coupling at (906) may also include contacting the mold shell 122 with the heat transfer member 140 for the first time at a first position on the mold shell 122 at (912). In addition, the method 900 may include actuating the heat transfer member 140 to disengage from the contact with the mold shell 122 at the first position at (914). In addition, the method 900 may include contacting the mold shell 122 with the heat transfer member 140 for a second time at a second position on the mold shell 122 at (916). The second position may be different from the first position. Between contacting the mold shell 122 for the first time at the first position and contacting the mold shell 122 for the second time at the second position, the mold shell 122 may be vertically moved by the actuation shaft 120. In addition, in many specific implementations, the mold shell 122 may be vertically moved while contacting the heat transfer member 140 at a specific position, so that the heat transfer member 140 may move together with the mold shell 122 to maintain contact.

[0066] In many implementations, the thermal coupling at (906) may further include, at (918), contacting the mold 122 with the heat transfer member 140 when the mold 122 is in the heating zone 114 (e.g., completely within the heating zone 114). Additionally, the contacting at (906) may further include, at (920), contacting the mold 122 with the heat transfer member 140 when the mold 122 is in the cooling zone 116 (e.g., completely within the cooling zone 116). Additionally, the contacting at (906) may further include, at (922), contacting the mold 122 with the heat transfer member 140 when the mold 122 is moved from the heating zone 114 to the cooling zone 116 (such that the mold 122 may be partially disposed in both the heating zone 114 and the cooling zone 116).

[0067] In various embodiments, the heat transfer member 140 can be a first heat transfer member 149, and the method 900 can further include contacting a first portion of the form with the first heat transfer 149 rod to increase a first local solidification rate of the alloy 162 near the first portion. In such specific implementations, the method 900 can further include contacting a second portion of the form 122 with a second heat transfer member 150 to reduce a second local solidification rate of the alloy 162 near the second portion. The second portion can be different from the first portion.

[0068] In implementations where thermal retention of the alloy 162 is desired, contact between the heat transfer member 140 and the shell mold 122 may not be required. For example, in such implementations, the thermal coupling at (906) may include thermally coupling the heat transfer member 140 and the shell mold 122 via radiation without contact by moving the heat transfer member 140 into a radiation distance away from the shell mold 122. In such implementations, the amount of radiation may be controlled by varying the radiation 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 the radiation, and moving the heat transfer rod 140 further away from the shell mold may reduce the radiation. In various implementations, the radiation distance may be up to about 0.5 inches, or such as between about 0.1 inches and about 0.5 inches, or such as between about 0.1 inches and about 0.4 inches, or such as between about 0.2 inches and about 0.3 inches.

[0069] The casting system 100 described herein advantageously provides a means for conducting and / or radiating heat transfer during directional solidification casting by utilizing a heat transfer member 140. The heat transfer member 140 may be in contact and out of contact (i.e., selectively in contact) to provide localized conductive or radiative heat transfer between the heat transfer member 140 and the alloy 162, thereby advantageously affecting (increasing or decreasing) the solidification rate of the alloy 162 to minimize grain defects.

[0070] This written description uses examples to disclose the invention, including the best mode, and also enables any person skilled in the art to practice the invention, including making and using any device or system and performing any combined method. The patentable scope of the invention is defined by the claims and may include other examples that occur to one skilled in the art. If these other examples include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements that do not differ substantially from the literal language of the claims, these other examples are intended to be within the scope of the claims.

[0071] Further aspects of the invention are provided by the subject matter of the following clauses:

[0072] 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, the method comprising: pouring a liquid alloy into a mold shell, the mold shell being positioned on a cooling plate in the heating zone; moving the mold shell from the heating zone to the cooling zone, whereby the alloy transforms from the liquid state to a solid state in the mold shell while the mold shell is moved from the heating zone to the cooling zone; and thermally coupling the mold shell to a heat transfer member.

[0073] A method according to any of the preceding clauses, wherein thermally coupling the mold shell to the heat transfer member further comprises: bringing the mold shell into contact with the heat transfer member for a first time at a first position on the mold shell; actuating the heat transfer member to disengage from contact with the mold shell at the first position; and bringing the mold shell into contact with the heat transfer member for a second time at a second position on the mold shell, the second position being different from the first position.

[0074] A method according to any of the preceding clauses, wherein thermally coupling the formwork with the heat transfer member further comprises actuating the heat transfer member from a first position not in contact with the formwork to a second position in contact with the formwork.

[0075] A method according to any of the preceding clauses, wherein the heat transfer member is formed of a material having a high thermal conductivity such that the contact between the heat transfer member and the formwork increases the solidification rate of the alloy.

[0076] A method according to any of the preceding clauses, wherein the heat transfer member is formed of a material having a low thermal conductivity such that the contact between the heat transfer member and the formwork reduces the solidification rate of the alloy.

[0077] A method according to any of the preceding clauses, wherein thermally coupling the formwork with a heat transfer member further comprises contacting the formwork with the heat transfer member while the formwork is in the heating zone.

[0078] A method according to any of the preceding clauses, wherein thermally coupling the formwork with the heat transfer member further comprises contacting the formwork with the heat transfer member while the formwork is in the cooling zone.

[0079] A method according to any of the preceding clauses, wherein thermally coupling the formwork with the heat transfer member further comprises contacting the formwork with the heat transfer member when moving the formwork from the heating zone into the cooling zone.

[0080] A method according to any of the preceding clauses, wherein a solidification front is formed within the form between the alloy in the liquid state and the alloy in the solid state as the form moves from the heating zone to the cooling zone.

[0081] A method according to any of the preceding clauses, wherein the step of thermally coupling further comprises contacting the formwork with the heat transfer member at or above the solidification front.

[0082] A method according to any of the preceding clauses, wherein the heat transfer member is a first heat transfer member, and wherein the thermal coupling step further comprises: contacting a first portion of the mold shell with the first heat transfer member to increase a first local solidification rate of the alloy near the first portion; and contacting a second portion of the mold shell with a second heat transfer member to reduce a second local solidification rate of the alloy near the second portion.

[0083] A method according to any of the preceding clauses, wherein the thermal coupling step further comprises thermally coupling the heat transfer member and the shell mould without contact via radiation by moving the heat transfer member into a radiation distance away from the shell mould.

[0084] A casting system for forming a directionally solidified casting component, the casting system comprising: a chamber; a baffle, the baffle being disposed in the chamber, the chamber and the baffle together defining a heating zone and a cooling zone, the heating zone and the cooling zone being separated by the baffle; a cooling plate, the cooling plate being movable between the heating zone and the cooling zone; a mold shell, the mold shell being disposed on the cooling plate; and a heat transfer member, the heat transfer member extending from a first end to a second end, the heat transfer member being actuable between a first position and a second position, in which the second end is not in contact with the mold shell and in which the second end is in contact with the mold shell.

[0085] The casting system of any of the preceding clauses, wherein the first end is coupled to the cooling plate.

[0086] A casting system according to any of the preceding clauses, wherein the first end is coupled to a chamber.

[0087] A casting system according to any of the preceding clauses, wherein the heat transfer member is composed of one or more of the following: a molybdenum alloy, a high melting point refractory alloy, graphite, silicon carbide or a ceramic matrix composite silicon carbide.

[0088] A casting system according to any of the preceding clauses, wherein the heat transfer member is composed of one or more of the following: silica, alumina, zircon, zirconia, chromia or yttria.

[0089] A casting system according to any of the preceding clauses, wherein the heat transfer member comprises an oxidation resistant coating.

[0090] The casting system of any of the preceding clauses, wherein the mold shell defines a shell thickness of between about 2 mm and about 25 mm.

[0091] A casting system according to any of the preceding clauses, wherein the heat transfer member is a first heat transfer member, and wherein the system further comprises a second heat transfer member.

Claims

1. A method of forming a directionally solidified cast component using a casting system, the casting system comprising a chamber having a heating zone and a cooling zone separated by a baffle, the method comprising: pouring the liquid alloy into a mold shell, the mold shell being positioned on a cooling plate in the heating zone; moving the mold from the heating zone to the cooling zone, whereby the alloy changes from the liquid state to the solid state within the mold while the mold is moved from the heating zone to the cooling zone; as well as The formwork is thermally coupled to a heat transfer member.

2. The method according to claim 1, wherein thermally coupling the mold shell with the heat transfer member further comprises: bringing the mold shell into contact with the heat transfer member at a first position on the mold shell; actuating the heat transfer member to break away from contact with the mold shell at the first position; as well as The formwork is brought into contact with the heat transfer member a second time at a second location on the formwork, the second location being different from the first location.

3. The method according to claim 1, wherein thermally coupling the formwork with the heat transfer member further comprises: The heat transfer member is actuated from a first position not in contact with the formwork to a second position in contact with the formwork.

4. The method of claim 1, wherein the heat transfer member is formed of 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.

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

6. The method according to claim 1, wherein thermally coupling the formwork to a heat transfer member further comprises: When the mold is in the heating zone, the mold is brought into contact with the heat transfer member.

7. The method according to claim 1, wherein thermally coupling the formwork with the heat transfer member further comprises: When the formwork is in the cooling zone, the formwork is brought into contact with the heat transfer member.

8. The method according to claim 1, wherein thermally coupling the formwork with the heat transfer member further comprises: When the formwork is moved from the heating zone into the cooling zone, the formwork is brought into contact with the heat transfer member.

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

10. The method of claim 9, wherein the thermal coupling step further comprises: The formwork is brought into contact with the heat transfer member at or above the solidification front.

11. The method of claim 1 , wherein the heat transfer member is a first heat transfer member, and wherein the thermal coupling step further comprises: 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; as well as A second portion of the mold shell is contacted with a second heat transfer member to reduce a second local solidification rate of the alloy proximate the second portion.

12. The method of claim 1, wherein the thermal coupling step further comprises: The heat transfer member and the shell mold are thermally coupled without contact via radiation by moving the heat transfer member into a radiation distance away from the shell mold.

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

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

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

16. The casting system of claim 13, wherein the heat transfer member is composed of one or more of the following: Molybdenum alloy, high melting point refractory alloy, graphite, silicon carbide or 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 comprises an oxidation resistant coating.

19. The casting system of claim 13, wherein the mold shell defines a shell thickness between about 2 mm and about 25 mm.

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

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