Airfoil external masking for internal aluminization

1 . A method for manufacturing a cooled part, the method comprising:

applying a pre-formed mask to a cast substrate having an exterior surface and an interior surface;

aluminizing the interior surface;

removing the pre-formed mask; and

applying a metallic coating to the exterior surface,

wherein:

the mask comprises a sintered body of a mask material;

the mask material comprises nickel and aluminum;

the method further comprises forming the pre-formed mask by compacting and sintering one or more powders; and

the compacting and sintering one or more powders comprises compacting with a polymeric binder, the sintering leaving porosity from vaporization or decomposition of the binder.

2 . The method of claim 1 wherein:

the applying the metallic coating is via cathodic arc deposition.

3 . The method of claim 1 wherein the metallic coating comprises:

MCrAlY.

4 . The method of claim 1 wherein the sintered one or more powders have an average overall composition of:

nickel as a largest by-weight constituent;

aluminum as a second largest by-weight constituent; and

chromium as a third largest by-weight constituent.

5 . The method of claim 1 wherein:

the part has an airfoil;

the sintered body is a first sintered body of said mask material and the mask comprises a second sintered body of said mask material; and

the applying of the preform mask is to an assembled condition forming a compartment accommodating the airfoil.

6 . The method of claim 5 wherein:

the applying of the metallic coating is via cathodic arc deposition.

7 . The method of claim 5 further comprising:

applying a collar around the first and second sintered bodies.

8 . The method of claim 5 wherein:

the mask further comprises:

a third sintered body; and

a fourth sintered body, wherein in the assembled condition the third sintered body and the fourth sintered body form a second compartment shaped to accommodate a firtree root of the part.

9 . The method of claim 8 further comprising:

mating a manifold to the firtree root, the mating comprising inserting spigots of the manifold into inlet ports of the firtree root;

assembling the third sintered body and fourth sintered body to the firtree root; and

inserting the assembled third sintered body and fourth sintered body to a body of a fixture, the inserting mating an inlet of the manifold to an inlet conduit of the fixture.

10 . The method of claim 1 wherein:

the compacting and sintering one or more powders comprises sintering at least two different powders.

11 . The method of claim 1 wherein:

the porosity from vaporization or decomposition of the binder provides increased surface area of mask material exposed to aluminization vapor in the aluminizing.