Method of making airfoils

1. A method of making an airfoil, the method comprising:

making a refractory metal core that defines an interior of the airfoil by a tomo-lithographic process, wherein the tomo-lithographic process comprises:

forming a first layer of the refractory metal core out of a first material;

forming a second layer of the refractory metal core out of the first material;

bonding the first and second layers together to form a laminate master pattern;

forming a flexible mold around the laminate master pattern;

removing the laminate master pattern from the flexible mold;

pouring a pulverulent refractory metal material mixed with a binder into the flexible mold; and

sintering the pulverulent refractory metal material in an oxygen-free environment to form the refractory metal core;

making a mold that defines an exterior of the airfoil;

inserting the refractory metal core into the mold; and

pouring an airfoil material between the refractory metal core and the mold to cast the airfoil.

2. The method of claim 1 , further comprising:

removing the airfoil from the mold; and

removing the core from the airfoil.

3. The method of claim 2 , wherein removing the core from the airfoil comprises applying an acid treatment.

4. The method of claim 1 , further comprising:

applying a ceramic coating to the refractory metal core prior to pouring the airfoil material.

5. The method of claim 4 , further comprising:

applying a metallic layer to the refractory metal core.

6. The method of claim 5 , wherein the metallic layer comprises platinum, another noble metal, chromium, and/or aluminum.

7. The method of claim 1 , wherein the refractory metal core comprises one of the following materials: molybdenum, tantalum, niobium, or tungsten.

8. The method of claim 1 , further comprising:

generating a computer model of the refractory metal core;

slicing the computer model into a plurality of digital layers; and

analyzing a plurality of empty spaces in an airfoil to generate the computer model of the refractory metal core.

9. The method of claim 1 , further comprising:

placing the refractory metal core into a wax injection die;

placing a ceramic core into the wax injection die;

encapsulating the refractory metal core and the ceramic core with a wax material to form a first wax pattern;

assembling a first wax pattern with a second wax pattern to form a wax assembly;

investing the wax assembly into a wet ceramic slurry mix;

investing the wax assembly into a dry ceramic stucco with intermittent controlled drying to build up a thickness of ceramic shell on the exterior of the assembly;

drying the thickness of ceramic shell; and

removing the wax material from the ceramic shell.

10. The method of claim 9 , further comprising:

firing the ceramic shell in an oxygen-free environment;

cleaning the ceramic shell;

casting a component in the ceramic shell;

removing the ceramic shell from the component;

removing the ceramic core with a caustic solution that is heated and under pressure; and

removing the refractory metal core with an acid solution.