US-12623373-B2 - Targeted ceramic casting core inhomogeneity

Abstract

A method for molding a ceramic core includes introducing a slurry to a mold and vibrating the mold. The slurry has: silica-containing particles; polymer fiber; and matrix precursor. The mold has an outer tool and a liner held within the outer tool. The vibrating comprises operating a plurality of vibration transducers distributed along the mold.

Inventors

• Anthony J. Del Boccio

Assignees

• RTX CORPORATION

Dates

Publication Date

20260512

Application Date

20230407

Claims (19)

1. 1 . A method for molding a ceramic core, the method comprising: introducing a slurry to a mold; and vibrating the mold, wherein: a portion of the mold defines an airfoil-forming core; the slurry comprises: silica-containing particles; polymer fiber; and matrix precursor; the mold comprises: an outer tool; and a liner held within the outer tool; and the vibrating comprises: operating a plurality of vibration transducers distributed along the mold, the vibration transducers mounted in pockets in the outer tool at a plurality of different spanwise and streamwise locations; and vibrating, via a pneumatic vibrator, a platform supporting the mold.
2. 2 . The method of claim 1 wherein the slurry comprises: the silica-containing particles and silicate(s), if any, are at least 95% of solids in the slurry.
3. 3 . The method of claim 1 wherein by weight: the silica-containing particles are at least 95% of solids in the slurry; the polymer fiber is 0.010% to 0.20% by weight of solids in the slurry.
4. 4 . The method of claim 1 wherein the vibrating comprises: vibrating at one or more frequencies in a range of 1000 Hz to 25 kHz.
5. 5 . The method of claim 1 wherein the vibrating comprises vibrating for at least one of: 10 or more seconds; at least 50% of the time of material introduction; and a time of at least 50% of the volume introduction.
6. 6 . The method of claim 1 wherein the vibrating causes at least one of: an at least 50% fiber concentration reduction in a target area relative to an introduced fiber concentration; and an at least 50% reduction in concentration of particles over 0.178 mm relative to an introduced concentration of said particles.
7. 7 . The method of claim 1 wherein: the vibration transducers are piezoelectric transducers or electromagnetic transducers.
8. 8 . The method of claim 1 wherein: the plurality of vibration transducers are at least partially embedded in the liner.
9. 9 . The method of claim 1 wherein the vibrating: biases the polymeric fiber and larger particles of the ceramic particulate away from a narrow region of the mold cavity relative to smaller particles of the particulate, so as to cause an at least 50% reduction in concentration of polymeric fiber in the narrow region of the mold cavity and an at least 50% reduction in concentration of particles over 0.178 mm relative to an introduced concentration of said particles in the narrow region of the mold cavity; and the narrow region comprises legs of a discharge slot section of the ceramic core.
10. 10 . The method of claim 1 wherein the vibrating: biases the polymeric fiber and larger particles of the ceramic particulate away from a narrow region of the mold cavity relative to smaller particles of the particulate, so as to cause an at least 50% reduction in concentration of polymeric fiber in the narrow region of the mold cavity and an at least 50% reduction in concentration of particles over 0.178 mm relative to an introduced concentration of said particles in the narrow region of the mold cavity.
11. 11 . A casting method comprising: molding, according to claim 1 , a ceramic core; casting alloy over the ceramic core.
12. 12 . The casting method of claim 11 wherein: the casting forms a blade having an attachment root and an airfoil.
13. 13 . The casting method of claim 5 further comprising: firing the ceramic core.
14. 14 . A method for molding a ceramic core, the method comprising: introducing a slurry to a mold; and vibrating the mold, wherein: the slurry comprises: silica-containing particles; polymer fiber; and matrix precursor; the mold comprises: an outer tool; and a liner held within the outer tool; and the vibrating comprises: operating a plurality of vibration transducers distributed along the mold and partially embedded in the liner and partially embedded in the outer tool.
15. 15 . The method of claim 14 wherein: the outer tool is a metallic two-piece shell.
16. 16 . A casting method comprising: molding, according to claim 14 , a ceramic core; casting alloy over the ceramic core.
17. 17 . A method for casting, the method comprising: molding a core, the molding comprising: introducing a slurry to a mold; and vibrating the mold; and casting alloy over the core, wherein: the slurry comprises: silica-containing particles; polymer fiber; and matrix precursor; the mold comprises: an outer tool; and a liner held within the outer tool; and the vibrating comprises: operating a plurality of vibration transducers distributed along the mold and mounted in pockets in the outer tool.
18. 18 . The casting method of claim 17 wherein: at least some of the pockets closed-ended compartments in the outer tool; and the casting forms a blade having an attachment root and an airfoil.
19. 19 . The casting method of claim 17 further comprising: firing the molded core.

Description

BACKGROUND The disclosure relates to gas turbine engines. More particularly, the disclosure relates to forming ceramic casting cores for casting internal passageways in cast metallic component substrates. Gas turbine engines (used in propulsion and power applications and broadly inclusive of turbojets, turboprops, turbofans, turboshafts, industrial gas turbines, and the like) have a number of internally-cooled components cast with internal cooling passageways. These are often cast using shells with partially embedded ceramic casting cores. Historically, such ceramic casting cores have been molded in a metallic die although molding in elastomeric (e.g., silicone) molds is also known. Such an elastomeric mold may be used to manufacture core shapes that would not be removable from a hard die due to backlocking. In one example of a core molding process using an elastomeric mold, the elastomeric mold forms a liner contained in a hard outer shell/tool with a port for introducing a ceramic slurry. The entire mold assembly may be placed in a vacuum chamber and vacuum drawn whereupon a slurry nozzle may mate with the port to introduce the ceramic slurry. However, even with the vacuum draw, the ceramic slurry may not always adequately fill the fine features of a core mold, which produce the desired internal cooling passages in the trailing edge of an airfoil. SUMMARY One aspect of the disclosure involves a method for molding a ceramic core. The method includes introducing a slurry to a mold; and vibrating the mold. The slurry comprises: silica-containing particles; polymer fiber; and matrix precursor (e.g., polymeric). The mold comprises: an outer tool; and a liner held within the outer tool. The vibrating comprises operating a plurality of vibration transducers distributed along the mold. In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the silica particles and silicate(s) if any are at least 95% by weight of solids in the slurry. In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, by weight: the silica particles and silicate(s) if any are at least 95% by weight of solids in the slurry; and the polymer fiber is 0.010% to 2.0% by weight of solids in the slurry. In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the vibrating comprises: vibrating at one or more frequencies in a range of 1000 Hz to 25 kHz. In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the vibrating comprises vibrating for at least one of: or more seconds; at least 50% of the time of material introduction; and a time of at least 50% of the volume introduction. In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the vibrating causes at least one of: an at least 50% fiber concentration reduction in a target area relative to an introduced fiber concentration; and an at least 50% reduction in concentration of particles over 0.178 mm relative to an introduced concentration of said particles. In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the vibrating further comprises: vibrating, via a pneumatic vibrator, a platform supporting the mold. A further aspect of the disclosure involves, a ceramic core molding apparatus comprising: a metallic fixture; and a polymeric liner held by the metallic fixture and forming a mold cavity. A plurality of transducers are mounted to the metallic fixture or the polymeric liner. In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the plurality of transducers are at least partially embedded in the polymeric liner. In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the metallic fixture is a two-piece shell. In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the transducers are piezoelectric transducers or electromagnetic transducers. In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively, the apparatus further comprises a pneumatic rotary vibrator. Optionally, such apparatus may involve a remanufacturing or reengineering from a baseline apparatus or configuration that lacked the transducers but had the pneumatic rotary vibrator. In a further embodiment of any of the foregoing embodiments, additionally and/or alternatively: a portion of the mold defines an airfoil-forming core; and the transducers are at a plurality of different spanwise (airfoil inner end (inner diameter in the engine frame of reference) to outer end) and streamwise (leading edge to trailing edge) locations. Optionally for such airfoil-forming core there may be at least two said transducers to the pressure side of the core and at least two to said transducers to the suction side of the core adjacent the airfoil portion o