METHOD OF FORMING A CAST METAL ARTICLE

• US 20120291983A1
• Filed: 05/18/2011
• Published: 11/22/2012
• Est. Priority Date: 05/18/2011
• Status: Active Grant

• Current Assignee: PCC Airfoils LLC (Berkshire Hathaway Incorporated)
• Original Assignee: PCC Airfoils LLC (Berkshire Hathaway Incorporated)
• Inventors: GRAHAM, LAWRENCE D., Barrett, James, Deptowicz, Don
• Granted Patent: US 8,393,381 B2
• Time in Patent Office: Days
• US Class Current: 164/516
• CPC Class Codes: B22C 9/04 Use of lost patterns
• CPC Class Codes: B22C 9/10 Cores; Manufacture or installation of cores breaker cores B22C9/084
• CPC Class Codes: B22D 15/02 of cylinders, pistons, bearing shells or like thin-walled objects
• CPC Class Codes: B22D 29/002 by leaching, washing or dissolving
• CPC Class Codes: B33Y 80/00 Products made by additive manufacturing

Abstract

A cast metal article is formed with an internal cavity. The internal cavity is formed by a ceramic core which is removed from the cast metal article to leave the cavity. The ceramic core is formed with a cavity to facilitate removal of the core from the cast metal article. To remove the core from the cast metal article, the cavity in the core is filled with a leaching liquid.

Claims

1. A method of forming a metal cast article, said method comprising the steps of forming a ceramic core containing a cavity, positioning the core in a mold, at least partially filling a cavity in the mold with molten metal while maintaining the cavity in the core at least substantially free of molten metal, solidifying the molten metal in the mold to form a cast metal article which at least partially contains the core, and removing the core from the cast metal article, said step of removing the core from the cast metal article includes at least partially filling the cavity in the core with a leaching liquid.

2. A method as set forth in claim 1 said step of forming a ceramic core includes providing a body of liquid which is capable of solidification when exposed to a beam of radiation, exposing an upper surface of the body of liquid to a beam of radiation, moving the beam of radiation relative to an upper surface of the body of liquid to effect formation of a first layer of the core, moving the first layer of the core downward in the body of liquid, covering an upper surface of the first layer of the core with liquid of the body of liquid, and moving the beam of radiation relative to the body of liquid to effect formation of a second layer of the core on the first layer of the core.

3. A method as set forth in claim 1 wherein said step of removing the core from the cast metal article includes applying fluid pressure against the leaching liquid to urge the leaching liquid into the cavity in the core and, thereafter, exposing the leaching liquid to a fluid pressure which is below atmospheric pressure.

4. A method as set forth in claim 1 wherein said step of forming a ceramic core containing a cavity includes forming a partition which divides at least a portion of the cavity into first and second sections, said step of filling the cavity in the core with a leaching liquid includes conducting leaching liquid into the first and second sections of the cavity.

5. A method as set forth in claim 1 wherein said step of solidifying the molten metal in the mold to form a cast metal article includes solidifying the molten metal to form a cast metal airfoil having leading and trailing edge portions, said step of forming a ceramic core includes forming a ceramic core having a first portion which is disposed in the leading edge portion of the cast metal airfoil prior to removal of the core from the cast metal article and a second portion which is disposed in the trailing edge portion of the cast metal airfoil prior to removal of the core from the cast metal article, said step of forming a ceramic core containing a cavity includes forming a ceramic core having at least a portion of a cavity formed in the first portion of the core to facilitate movement of leaching liquid into the leading edge portion of the cast metal airfoil and at least a portion of a cavity formed the second portion of the core to facilitate movement of leaching liquid into the trailing edge portion of the cast metal airfoil.

6. A method as set forth in claim 1 wherein said step of solidifying the molten metal to form a cast metal article includes forming a cast metal airfoil having a tip end portion, said step of forming a ceramic core includes forming a ceramic core having an end portion which is disposed in the tip end portion of the cast metal airfoil prior to removal of the core from the cast metal article, said step of forming a ceramic core containing a cavity includes forming a ceramic core having at least a portion of a cavity formed in the end portion of the core to facilitate movement of leaching liquid into the tip end portion of the cast metal airfoil.

7. A method as set forth in claim 6 wherein said step of forming a cast metal airfoil includes forming a cast metal airfoil having an edge portion which is connected with the tip end portion of the cast metal airfoil, said step of forming a ceramic core includes forming a ceramic core having a second portion which is disposed in the edge portion of the cast metal article prior to removal of the core from the cast metal airfoil, said step of forming a ceramic core containing a cavity includes forming a ceramic core having at least a portion of a cavity in the second portion of the core to facilitate movement of leaching liquid into the edge portion of the cast metal airfoil.

8. A method as set forth in claim 1 wherein said step of forming a ceramic core includes forming a ceramic core having a longitudinal central axis by moving a beam of radiation in a direction transverse to the longitudinal central axis of the core and sequentially forming layers of the core as the beam of radiation moves in a direction transverse to the longitudinal central axis of the core.

9. A method as set forth in claim 1 wherein said step of forming a ceramic core includes forming a ceramic core having a longitudinal central axis by moving a beam of radiation along the longitudinal central axis of the core and sequentially forming layers of the core as the beam of radiation moves in a direction along the longitudinal axis of the core.

10. A method as set forth in claim 1 wherein said step of forming a ceramic core containing a cavity includes sequentially forming cross sectional layers of the core with portions of the cavity in the core disposed in at least some of the layers of the core.

11. A method as set forth in claim 1 wherein said step of forming a ceramic core includes forming a ring shaped core which extends around an open central area and forming a ring shaped cavity in the core with the ring shaped cavity extending around the open central area, said step of filling the cavity in the core with leaching liquid includes filling the ring shaped cavity with leaching liquid.

12. A method as set forth in claim 1 wherein said step of forming a ceramic core includes forming a ring shaped core having a toroidal configuration and forming a circular cavity within the core, said step of filling the cavity in the core with leaching liquid includes filling the circular cavity with leaching liquid.

13. A method as set forth in claim 1 wherein said step of forming a ceramic core includes forming a core which has an open central portion and forming a cavity which extends around the open central portion of the core.

14. A method as set forth in claim 1 wherein said step of forming a ceramic core includes forming a core having a plurality of straight portions interconnected by a plurality of curving portions and forming a cavity having straight portions disposed in the straight portions of the core and having curving portions disposed in the curving portions of the core.

15. A method as set forth in claim 1 wherein said step of forming a ceramic core containing a cavity includes forming a honey comb structure which is disposed in the cavity in the core.

16. A method as set forth in claim 15 wherein said step of forming a honey comb structure includes forming an open cell structure to enable liquid to be conducted through the honey comb structure.

17. A method as set forth in claim 15 wherein said step of forming a honey comb structure includes forming a closed cell structure to block a flow of liquid through the honey comb structure.

18. A method as set forth in claim 1 wherein said step of forming a ceramic core containing a cavity includes forming a close ended cavity to block a flow of liquid through the cavity.

19. A method as set forth in claim 1 wherein said step of forming a ceramic core containing a cavity includes forming an open ended cavity to enable liquid to flow through the cavity.

20. A method of forming a cast metal article, said method comprising the steps of forming a ceramic core having a root end portion and a blade portion, the blade portion of the core having first and second edge portions which are connected with a second end portion of the core which is opposite from the root end portion of the core, said step of forming the ceramic core includes forming a cavity in the core with portions of the cavity disposed in the first and second edge portions and in the root and second end portions of the core, positioning the core in a cavity in a mold, said step of positioning the core in the cavity in the mold includes positioning the core in a cavity having a configuration corresponding to the configuration of an airfoil, at least partially filling the cavity in the mold with molten metal while maintaining the cavity in the core at least substantially free of molten metal, solidifying the molten metal in the cavity in the mold to form a cast metal airfoil which at least partially contains the core, and removing the core from the cast metal airfoil, said step of removing the core from the cast metal airfoil includes conducting a flow of a leaching liquid from the root end portion of the core to the portions of the cavity disposed in the first and second edge portions of the core and conducting a flow of the leaching liquid from at least the portion of the cavity disposed in one of the edge portions of the core into the second end portion of the core.