Abstract: Method of making a ceramic core for casting an industrial gas turbine engine airfoil having a large airfoil pitch by forming a precursor core (chill) of smaller dimensions than the final desired ceramic core, firing the chill, applying a thin ceramic skin to the fired chill to form a coated core of final dimensions, and then firing the coated core. Firing of the thin ceramic skin reduces airfoil pitch shrinkage resulting from the latter firing operation to reduce overall core dimensional tolerance variations.

Abstract: An impregnated fired porous alumina-based ceramic core for use in an investment shell mold in the casting of molten metals and alloys wherein the core is impregnated with yttria to improve core creep resistance at elevated casting temperatures and times.

Abstract: An impregnated fired porous alumina-based ceramic core for use in an investment shell mold in the casting of molten metals and alloys wherein the core is impregnated with yttria to improve core creep resistance at elevated casting temperatures and times.

Abstract: Method of making a ceramic core for casting an industrial gas turbine engine airfoil having a large airfoil pitch by forming a precursor core (chill) of smaller dimensions than the final desired ceramic core, firing the chill, applying a thin ceramic skin to the fired chill to form a coated core of final dimensions, and then firing the coated core. Firing of the thin ceramic skin reduces airfoil pitch shrinkage resulting from the latter firing operation to reduce overall core dimensional tolerance variations.

Abstract: Method of making a ceramic core for casting an industrial gas turbine engine airfoil having a large airfoil pitch by forming a precursor core (chill) of smaller dimensions than the final desired ceramic core, firing the chill, applying a thin ceramic skin to the fired chill to form a coated core of final dimensions, and then firing the coated core. Firing of the thin ceramic skin reduces airfoil pitch shrinkage resulting from the latter firing operation to reduce overall core dimensional tolerance variations.

Abstract: The preparation of highly densified ceramic bodies by the sintering of certain preceramic polysilazanes filled with silicon carbide powders, metal-containing sintering aids, and, optionally, polysilazane curing agents is described. Such highly densified ceramic bodies can be prepared by either a pressureless sintering process or a hot press sintering process. The compositions of this invention can be formed into desired shapes and then sintered to form ceramic, shaped bodies with high densities. One advantage of the present invention is that the green bodies have relative high strengths and thus can be easily handled and, if desired, machined before sintering. The preceramic polysilazanes useful in this invention must yield ceramic chars which contains free or excess carbon in addition to carbon in the form of silicon carbide upon pyrolysis to elevated temperatures.