Abstract
A method for fabricating a ceramic mold is provided. The method includes the steps of contacting a cured portion of a workpiece with a liquid ceramic photopolymer, irradiating a portion of the liquid ceramic photopolymer adjacent to the cured portion through a window contacting the liquid ceramic photopolymer, removing the workpiece from the uncured liquid ceramic photopolymer, and repeating the steps until a ceramic mold is formed. The ceramic mold includes a first opening for creating a cast article and a second opening for receiving a support member.
Claims
1. A method for fabricating a ceramic mold, comprising: (a) contacting a cured portion of a workpiece with a liquid ceramic photopolymer; (b) irradiating a portion of the liquid ceramic photopolymer adjacent to the cured portion through a window contacting the liquid ceramic photopolymer; (c) removing the workpiece from the uncured liquid ceramic photopolymer; and (d) repeating steps (a)-(c) until a ceramic mold is formed, the ceramic mold comprising a first opening for creating a cast article and a second opening for receiving a support member.
2. The method of claim 1, further comprising pouring a liquid metal into the first opening and solidifying the liquid metal to form the cast article.
3. The method of claim 1, wherein the support member is at least one sphere.
4. The method of claim 1, wherein the support member is at least one metal sheet.
5. The method of claim 1, wherein the support member is made of a ceramic refractory metal and engineered to provide stiffness at various portions of the ceramic mold.
6. The method of claim 1, wherein the support member has a melting temperature that is higher than the melting temperature of a metal used in casting.
7. The method of claim 1, wherein the support member is a plurality of alumina bubbles accommodated in the second opening to provide support to the ceramic mold.
8. The method of claim 1, wherein the ceramic mold is configured with at least one support member at an outer portion of the ceramic mold, the at least one support member at the outer portion being made of a ceramic refractory metal and having a melting temperature that is higher than the melting temperature of a metal used in casting.
9. A method of preparing a cast component comprising: forming a printed ceramic mold, the ceramic mold comprising, a first and second opening, the first opening for creating the cast component and the second opening for receiving a support member.
10. The method of claim 9, further comprising pouring a liquid metal into the first opening and solidifying the liquid metal to form the cast component.
11. The method of claim 9, wherein the support member is at least one sphere.
12. The method of claim 9, wherein the support member is at least one metal sheet.
13. The method of claim 9, wherein the support member is made of a ceramic refractory metal and engineered to provide stiffness at various portions of the ceramic mold.
14. The method of claim 9, wherein the support member has a melting temperature that is higher than the melting temperature of a metal used in casting.
15. The method of claim 9, wherein the support member is a plurality of alumina bubbles accommodated in the second opening to provide support to the ceramic mold.
16. The method of claim 9, wherein the ceramic mold is configured with at least one support member at an outer portion of the ceramic mold, the at least one support member at the outer portion being made of a ceramic refractory metal and having a melting temperature that is higher than the melting temperature of a metal used in casting.
17. An apparatus for preparing a cast component, comprising: a ceramic casting mold, the ceramic casting mold comprising, a first and second opening, the first opening for creating the cast component and the second opening for receiving a support member.
18. The method of claim 17, wherein the support member is made of a ceramic refractory metal and engineered to provide stiffness at various portions of the ceramic mold.
19. The method of claim 17, wherein the support member has a melting temperature that is higher than the melting temperature of a metal used in casting.
20. The method of claim 17, wherein the ceramic mold is configured with at least one support member at an outer portion of the ceramic mold, the at least one support member at the outer portion being made of a ceramic refractory metal and having a melting temperature that is higher than the melting temperature of a metal used in casting.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The accompanying drawings, which are incorporated into and constitute a part of this specification, illustrate one or more example aspects of the present disclosure and, together with the detailed description, serve to explain their principles and implementations.
[0019] FIG. 1 is a block diagram showing the steps for conventional investment casting;
[0020] FIG. 2 is a diagram showing a conventional wax pattern attached to a wax tree structure for investment casting of a turbine blade;
[0021] FIG. 3 is a diagram showing the conventional ceramic mold of FIG. 2 after the wax has been removed;
[0022] FIG. 4 is a diagram showing the conventional ceramic mold of FIG. 2 after molten metal is poured into the mold;
[0023] FIG. 5 is a diagram showing a perspective view of a prior art integrated core-shell mold with ties connecting the core and shell portions;
[0024] FIG. 6 is a block diagram illustrating the casting process according to an embodiment of the present invention;
[0025] FIG. 7 is a diagram illustrating a cross-sectional side view of an integrated core-shell mold according to an embodiment of the present invention;
[0026] FIG. 8 is a diagram illustrating a cross-sectional side view of an integrated core-shell mold according to an example embodiment;
[0027] FIG. 9 is a diagram illustrating a cross-sectional side view of an integrated core-shell mold according to an embodiment of the present invention;
[0028] FIG. 10 is a diagram illustrating a perspective top view of the integrated core-shell mold in FIG. 9 according to an example embodiment;
[0029] FIG. 11 is a diagram illustrating a cross-sectional side view of an integrated core-shell mold according to another embodiment of the present invention;
[0030] FIG. 12 is a diagram illustrating a perspective top view of the integrated core-shell mold in FIG. 11 according to an example embodiment;
[0031] FIGS. 13A and 13B are diagrams illustrating a cross-sectional side view of an integrated core-shell mold according to another embodiment of the present invention;
[0032] FIGS. 14A and 14B are diagrams illustrating a cross-sectional side view of an integrated core-shell mold according to another embodiment of the present invention; and
[0033] FIGS. 15A and 15B are diagrams illustrating a cross-sectional side view of an integrated core-shell mold according to another embodiment of the present invention.
DETAILED DESCRIPTION
[0034] The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. For example, the present invention provides a preferred method for making cast metal parts, and preferably those cast metal parts used in the manufacture of jet aircraft engines. Specifically, the production of single crystal, nickel-based superalloy cast parts such as turbine blades, vanes, and shroud components can be advantageously produced in accordance with this invention. However, other cast metal components may be prepared using the techniques and integrated ceramic molds of the present invention.
[0035] FIG. 6 is a block diagram illustrating the casting process according to an embodiment of the present invention. By employing a Direct Light Printing (DLP) process or any other additive manufacturing method to form a ceramic core-shell mold, the manufacturing of a component requires significantly less steps than typical investment casting. FIG. 6 shows the steps of forming a ceramic mold and core using additive manufacturing 601, prepping the wax assembly 602, dipping the core-shell mold into a ceramic slurry 603, drying the slurry 604, a dewaxing and/or firing process 605, and casting and leaching the ceramic material 606. It may be appreciated that the step of dipping the core-shell mold into the ceramic slurry 603 and drying the slurry 604 may be repeated as shown in FIG. 6. The above-mentioned process of forming a mold may include forming a ceramic mold and core using a DLP process such that the mold is formed as a core-shell structure and is formed of a first photopolymerizable ceramic material. Once a mold is formed, the mold may be joined with several molds and/or may have a wax portion added 602 which will form a flow path for the molten material. The core-shell mold and an additional wax structures added previously may then undergo a dipping or coating process 603 to form a ceramic coating on the outer surface of the shell of the core-shell mold and on the outer surface of any added wax structures. The core-shell mold may then undergo a drying process to the dry the slurry 604. As mentioned above, steps 603 and 604 may be repeated. Then, the core-shell mold and outer ceramic shell may undergo a dewaxing and/or firming process 605 to remove the wax and/or to sinter the ceramic materials which form the mold. It may be appreciated that steps 602, 603, 604, and 605 may be omitted if the ceramic mold and core in step 601 is manufactured to the final mold shape and ready for pouring. The molten super alloy may then be poured into the mold. Once the superalloy has solidified, the core-shell mold and outer shell may be removed through either leaching of the ceramic material and/or through mechanical removal of the mold.
[0036] FIG. 7 is a diagram illustrating a cross-sectional side view of an integrated core-shell mold according to an embodiment of the present invention. As shown in FIG. 7, the core 700 is connected to the shell 701 through several filaments 702. The core-shell mold 700/701 defines a cavity 703 for investment casting a turbine blade.
[0037] FIG. 8 is a diagram illustrating a cross-sectional side view of an integrated core-shell mold according to an example embodiment. As shown in FIG. 8, the cavity 703 in FIG. 7 is filled with a metal 804, such as a nickel based alloy, i.e., Inconel. Upon leaching of the ceramic core-shell, the resulting cast object is a turbine blade having a cooling hole pattern in the surface of the blade. It should be appreciated that although FIGS. 7 and 8 provide a cross sectional view showing cooling holes at the leading and trailing edge of the turbine blade, that additional cooling holes may be provided where desired including on the sides of the turbine blades or any other location desired. In particular, the present invention may be used to form cooling holes within the casting process in any particular design. In other words, one would be able to produce conventional cooling holes in any pattern where drilling was used previously to form the cooling holes. However, the present invention will allow for cooling hole patterns previously unattainable due to the limitations of conventional technologies for creating cooling holes within cast components, i.e., drilling.
[0038] According to an example embodiment, the present invention provides a methodology of using high temperature engineered support mechanisms during the liquid metal pouring phase of the casting process. As such, the amount of additive material and print time of the additive ceramic process is minimized.
[0039] FIG. 9 is a diagram illustrating a cross-sectional side view of an integrated core-shell mold according to an embodiment of the present invention. As shown in FIG. 9, the core 900 is connected to the shell 901 through several filaments 902. The core-shell mold 900/901 defines a cavity 903 for investment casting a turbine blade. According to an example embodiment, the core-shell mold 900/901 may be formed with an opening 905 to allow for a support member with selective stiffness to be inserted into the core-shell mold 900/901. In a preferred embodiment, a support member such as spheres 906 having a selective stiffness may be inserted in the opening 905. The spheres 906 may be alumina. Although FIG. 9 shows the core-shell mold 900/901 configured with the opening 905 at an upper portion of the core-shell mold 900/901, the present invention is not limited thereto and the core-shell mold may be configured with an opening to accommodate spheres at selective areas of the core-shell mold. The spheres may be inserted into the core-shell mold at selective areas where needed during the casting process. It can be appreciated that inserting spheres in selective areas throughout the core-shell mold allows for the shell to remain thin in most places which improves the cooling rate during the casting process. Non-spherical irregular shaped support members may also be used instead of the spheres 906 as shown in FIG. 9. As such, the amount of additive ceramic material needed and the print time for the casting process is minimized.
[0040] FIG. 10 is a diagram illustrating a perspective view of the integrated core-shell mold in FIG. 9 according to an example embodiment. As shown in FIG. 10, the core portion 1001 and shell portion 1002 of the integrated core-shell mold is held together via a series of tie structures 1003 provided at the bottom edge of the mold. According to an example embodiment, FIG. 10 shows a perspective view in which spheres 1005 may be inserted in the core-shell 1002.
[0041] FIG. 11 is a diagram illustrating a cross-sectional side view of an integrated core-shell mold according to another embodiment of the present invention. As shown in FIG. 11, the core 1100 is connected to the shell 1101 through several filaments 1102. The core-shell mold 1100/1101 defines a cavity 1103 for investment casting a turbine blade. According to an example embodiment, the core-shell mold 1100/1101 may be formed with an opening 1105 to allow for a support member with selective stiffness to be inserted into the core-shell mold 1100/1101. In a preferred embodiment, a support member such as metal sheets 1106 having a selective stiffness may be inserted in the opening 1105. The metal sheets 1106 may have a high melting temperature that is higher than the metal used for casting. Although FIG. 11 shows the core-shell mold 1100/1101 configured with the opening 1105 at an upper portion of the core-shell mold 1100/1101, the present invention is not limited thereto and the core-shell mold may be configured with an opening to accommodate metal sheets at selective areas of the core-shell mold. For example, the metal sheets may be inserted into the core-shell mold at selective areas where needed during the casting process. It can be appreciated that inserting metal sheets in selective areas throughout the core-shell mold allows for the shell to remain thin in most places which improves the cooling rate during the casting process. Selective areas with the metal sheets can also increase conductivity and improve the cooling rate. As such, the amount of additive ceramic material needed and the print time for the casting process is minimized.
[0042] FIG. 12 is a diagram illustrating a perspective view of the integrated core-shell mold in FIG. 11 according to an example embodiment. As shown in FIG. 12, the core portion 1201 and shell portion 1202 of the integrated core-shell mold is held together via a series of tie structures 1203 provided at the bottom edge of the mold. According to an example embodiment, FIG. 12 shows a perspective view in which metal sheets 1205 may be inserted in the core-shell 1202.
[0043] As described above, the present invention may provide internal support features such as, for example, high temperature spheres and metal sheets. In other exemplary embodiments, the core-shell mold may include external supports features such as, for example, ceramic containment blocks, metal clips, and metal bands on an outer portion of the core-shell mold having internal support features. It may be appreciated that the internal supports and the external supports may be made of a ceramic refractory metal having a melting temperature higher that is higher than the melting temperature of the metal used in casting the cast component.
[0044] FIGS. 13A and 13B are diagrams illustrating a cross-sectional side view of an integrated core-shell mold according to another embodiment of the present invention. According to an exemplary embodiment as shown in FIG. 13A, a support member such as metal sheets 1306 having a selective stiffness may be inserted in the opening 1305, and an external outer portion of the core-shell mold 1300/1301 may be configured with high temperature metal clips 1310. The metal clips 1310 may also have a selective stiffness to support the core-shell mold 1300/1301 where needed. The metal sheets 1306 and the metal clips 1310 may both have a melting temperature higher than the melting temperature of the metal used for casting. An exemplary embodiment with metal sheets 1306 and metal clips 1310 as shown in FIG. 13A is provided, but the present invention may not be limited thereto, and thus, may provide the metal sheets and metal clips at selective areas about the core-shell mold where needed during the casting process. In another exemplary embodiment as shown in FIG. 13B, spheres 1308 may be inserted in the opening 1305 with the high temperature metal clips 1310 at an external outer portion of the core-shell mold 1300/1301. The spheres 1308 and the metal clips 1310 may both have a melting temperature higher than the melting temperature of the metal used for casting.
[0045] FIGS. 14A and 14B are diagrams illustrating a cross-sectional side view of an integrated core-shell mold according to another embodiment of the present invention. According to an exemplary embodiment as shown in FIG. 14A, a support member such as metal sheets 1406 may be inserted in the opening 1405, and an external outer portion of the core-shell mold 1400/1401 may be configured with high temperature metal bands 1410. The metal bands 1410 may also have a selective stiffness to support the core-shell mold 1400/1401 where needed. The metal sheets 1406 and the metal bands 1410 may both have a melting temperature higher than the melting temperature of the metal used for casting. An exemplary embodiment with metal sheets 1406 and metal bands 1410 as shown in FIG. 14A is provided, but the present invention may not be limited thereto, and thus, may provide the metal sheets and metal bands at selective areas about the core-shell mold where needed during the casting process. In another exemplary embodiment as shown in FIG. 14B, spheres 1408 may be inserted in the opening 1405 with the high temperature metal bands 1410 at an external outer portion of the core-shell mold 1400/1401. The spheres 1408 and the metal bands 1410 may both have a melting temperature higher than the melting temperature of the metal used for casting.
[0046] FIGS. 15A and 15B are diagrams illustrating a cross-sectional side view of an integrated core-shell mold according to another embodiment of the present invention. According to an exemplary embodiment as shown in FIG. 15A, metal sheets 1506 may be inserted in the opening 1505, and an external outer portion of the core-shell mold 1500/1501 may be configured with ceramic containment blocks 1510. The containment blocks 1510 may be engineered with cooling passages 1512 therein to improve casting cooling rates. The containment blocks may also be engineered with stiffening ribs 1511 to support additive ceramic where needed. In another exemplary embodiment as shown in FIG. 15B, spheres 1508 may be inserted in the opening 1505 with the containment blocks 1510 at an external outer portion of the core-shell mold 1500/1501.
[0047] In accordance with the above-described example embodiments, the present invention provides structural supports to accommodate ceramic pieces made via an additive process. An aspect of the present invention provides a methodology of using high temperature supports during the liquid pouring phase of the casting process. As such, the material and print time of the additive ceramic process is minimized and support needed during the casting process is provided. Engineered features such as, for example, high temperature spheres and metal sheets provide stiffness at selective areas while allowing the use of thin ceramic shells and improved casting cooling rates. Additionally, the present invention may utilize external engineered support features such as, for example, ceramic containment blocks, metal clips, and metal bands along with the spheres and metal sheets to further provide structural support during the additive process.
[0048] In an aspect, the present invention relates to the core-shell mold structures of the present invention incorporated or combined with features of other core-shell molds produced in a similar manner. The following patent applications include disclosure of these various aspects and their use:
[0049] U.S. patent application Ser. No. 15/377,728, titled INTEGRATED CASTING CORE-SHELL STRUCTURE with attorney docket number 037216.00036/284976, and filed Dec. 13, 2016;
[0050] U.S. patent application Ser. No. 15/377,711, titled INTEGRATED CASTING CORE-SHELL STRUCTURE WITH FLOATING TIP PLENUM with attorney docket number 037216.00037/284997, and filed Dec. 13, 2016;
[0051] U.S. patent application Ser. No. 15/377,796, titled MULTI-PIECE INTEGRATED CORE-SHELL STRUCTURE FOR MAKING CAST COMPONENT with attorney docket number 037216.00033/284909, and filed Dec. 13, 2016;
[0052] U.S. patent application Ser. No. 15/377,746, titled MULTI-PIECE INTEGRATED CORE-SHELL STRUCTURE WITH STANDOFF AND/OR BUMPER FOR MAKING CAST COMPONENT with attorney docket number 037216.00042/284909A, and filed Dec. 13, 2016;
[0053] U.S. patent application Ser. No. 15/377,673, titled INTEGRATED CASTING CORE SHELL STRUCTURE WITH PRINTED TUBES FOR MAKING CAST COMPONENT with attorney docket number 037216.00032/284917, and filed Dec. 13, 2016;
[0054] U.S. patent application Ser. No. 15/377,787, titled INTEGRATED CASTING CORE SHELL STRUCTURE FOR MAKING CAST COMPONENT WITH NON-LINEAR HOLES with attorney docket number 037216.00041/285064, and filed Dec. 13, 2016;
[0055] U.S. patent application Ser. No. 15/377,783, titled INTEGRATED CASTING CORE SHELL STRUCTURE FOR MAKING CAST COMPONENT WITH COOLING HOLES IN INACCESSIBLE LOCATIONS with attorney docket number 037216.00055/285064A, and filed Dec. 13, 2016;
[0056] U.S. patent application Ser. No. 15/377766, titled INTEGRATED CASTING CORE SHELL STRUCTURE FOR MAKING CAST COMPONENT HAVING THIN ROOT COMPONENTS with attorney docket number 037216.00053/285064B, and filed Dec. 13, 2016.
[0057] The disclosures of each of these applications are incorporated herein in their entirety to the extent they disclose additional aspects of core-shell molds and methods of making that can be used in conjunction with the core-shell molds disclosed herein.
[0058] This written description uses examples to disclose the invention, including the preferred embodiments, 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 incorporated methods. 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 intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. Aspects from the various embodiments described, as well as other known equivalents for each such aspect, can be mixed and matched by one of ordinary skill in the art to construct additional embodiments and techniques in accordance with principles of this application.
