Core compositions and articles with improved performance for use in castings for gas turbine applications

A method for fabricating a fired ceramic article, a green product, and a fired ceramic article, all for use as a core in the investment casting of directionally solidified eutectic and super alloy material. A ceramic slurry is prepared of alumina, aluminum and a solution of a polymerizable binder in a liquid. The slurry is extruded under low pressure into a closed cavity to form a gelled green product which is subsequently heated in an oxygen-containing atmosphere, wherein the oxygen reacts with the aluminum in the green product to form alumina which advantageously causes an increase in volume of the green product which counters the shrinkage effects of heating. The polymerizable binder is of a type which cross-links with the alumina and upon heating the liquid component of such binder vaporizes and the remaining polymer component subsequently gasifies on further heating to leave desired interstitial pores within the green product, which assist in allowing the oxygen to permeate the green product, which assists in oxidation of the aluminum through the green product. The green product is thereafter sintered to form a substantially dimensionally precise ceramic article suitable for precision-casting of super alloy materials.

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