Multipiece core assembly

Details Multipiece core assembly Multipiece core assembly

1998-12-01

2001-02-13

Batten, Jr., J. Reed (Department: 1722)

Metal founding

Process

Shaping liquid metal against a forming surface

C164S015000, C164S028000, C164S369000

Reexamination Certificate

active

06186217

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to complex multi-piece ceramic cores for casting superalloy airfoil castings, such as airfoils having multiple cast walls and complex channels for improved air cooling efficiency.
BACKGROUND OF THE INVENTION
Most manufacturers of gas turbine engines are evaluating advanced multi-walled, thin-walled turbine airfoils (i.e. turbine blade or vane) which include intricate air cooling channels to improve efficiency of airfoil internal cooling to permit greater engine thrust and provide satisfactory airfoil service life.
U.S. Pat. Nos. 5, 295, 530 and 5, 545, 003 describe advanced multi-walled, thin-walled turbine blade or vane designs which include intricate air cooling channels to this end.
In U.S. Pat. No. 5, 295, 530, a multi-wall core assembly is made by coating a first thin wall ceramic core with wax or plastic, a second similar ceramic core is positioned on the first coated ceramic core using temporary locating pins, holes are drilled through the ceramic cores, a locating rod is inserted into each drilled hole and then the second core then is coated with wax or plastic. This sequence is repeated as necessary to build up the multi-wall ceramic core assembly.
This core assembly procedure is quite complex, time consuming and costly as a result of use of the multiple connecting and other rods and drilled holes in the cores to receive the rods. In addition, this core assembly procedure can result in a loss of dimensional accuracy and repeatability of the core assemblies and thus airfoil castings produced using such core assemblies.
An object of the present invention is to provide a multi-wall ceramic core assembly and method of making same for use in casting advanced multi-walled, thin-walled turbine airfoils (e.g. turbine blade or vane castings) which can include complex air cooling channels to improve efficiency of airfoil internal cooling.
Another object of the present invention is to provide a multi-wall ceramic core assembly and method of making same for use in casting advanced multi-walled, thin-walled turbine airfoils wherein a multi-piece core assembly is formed in novel manner which overcomes disadvantages of the previous core assembly techniques.
SUMMARY OF THE INVENTION
The present invention provides, in an illustrative embodiment, a multi-wall ceramic core assembly and method of making same wherein a plurality of individual thin wall, arcuate (e.g airfoil shaped) core elements are formed in respective master dies to have integral interlocking locating features and ceramic adhesive entry holes, the individual core elements are prefired in respective ceramic setter supports, the prefired core elements are assembled together using the locator features of adjacent core elements to effect proper core element positioning relative to one another, and the assembled core elements are adhered together using ceramic adhesive introduced through the preformed adhesive entry holes to the internal joints defined between mating interlocked locator features.
The multi-wall ceramic core assembly so produced comprises the plurality of spaced apart thin wall, arcuate (e.g airfoil shaped) core elements located relative to one another by the integral interlocked locator features and joined together by ceramic adhesive at the internal joints defined between the interlocked locator features.
The present invention is advantageous in that the ceramic core elements can be formed with the interlocking locator features by conventional injection or transfer molding using appropriate ceramic slurries, in that prefiring of the core elements improves their dimensional integrity and permits their inspection prior to assembly to improve yield of acceptable ceramic core assemblies and reduces core assembly costs as a result, and in that high dimensional accuracy and repeatability of core assemblies is achievable.


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