Self-lubricating, wear resistant piston seal

1. A piston seal assembly for a gas turbine engine, comprising:

a seal comprised of a nickel-based superalloy;

a component in contact with the seal and defining a seal-counterface, wherein the seal and seal-counterface define a static seal assembly; and

a coating on the seal at the seal-counterface, wherein the coating comprises a nanostructured, self-lubricating coating material, wherein the coating has a thickness of between 4 and 10 mils, wherein the coating comprises a binder matrix, a hardener and a solid lubricant, wherein the hardener and the solid lubricant are distributed through the binder matrix, wherein the binder matrix is a nickel-based composition selected from the group consisting of NiCr, Ni—Co, NiMoAl and combinations thereof, wherein the hardener is selected from the group consisting of glass, chrome carbide (Cr 3 C 2 ), chrome oxide and combinations thereof, and wherein the solid lubricant is selected from the group consisting of silver, calcium fluoride, barium fluoride and combinations thereof.

2. The assembly of claim 1 , wherein the coating has a thickness of between 4 and 7 mils.

3. The assembly of claim 1 , wherein the nanostructured, self-lubricating coating material is selected from the group consisting of NiCr—CaF 2 -glass, NiCr—CaF 2 -glass-Ag, Ni—Co—Cr 3 C 2 —Ag—BaF 2 /CaF 2 , NiCr—Cr 2 O 3 —Ag—BaF 2 /CaF 2 and NiMoAl—Cr 2 O 3 —Ag—BaF 2 /CaF 2 .

4. The assembly of claim 1 , wherein the nanostructured, self-lubricating coating material is selected from the group consisting of NiCr—Cr 2 O 3 —Ag—BaF 2 /CaF 2 and NiMoAl—Cr 2 O 3 —Ag—BaF 2 /CaF 2 , and mixtures thereof.

5. The assembly of claim 1 , wherein the seal comprises an age hardening austenitic nickel-based superalloy.

6. The assembly of claim 1 , wherein the seal has non-contact surfaces that are not in contact with the component, and the coating is on the seal at the seal-counterface, and not on the non-contact surfaces.

7. The assembly of claim 1 , wherein the component comprises two components, with the seal mounted between the two components to define two seal-counterfaces, and wherein the coating is on the seal at both of the two seal-counterfaces.

8. The assembly of claim 1 , wherein the two components comprise a mid-turbine-frame (MTF) vane and an outer air seal.

9. The assembly of claim 1 , wherein the component has a counterface that defines, with the seal, the seal-counterface, and further comprising a further coating on the counterface.

10. The assembly of claim 9 , wherein the further coating comprises the same material as the coating on the seal.

11. A seal for a gas turbine engine, comprising a seal comprised of a nickel-based superalloy and a coating on the seal, wherein the coating comprises a nanostructured, self-lubricating coating material, wherein the coating has a thickness of between 4 and 10 mils, wherein the coating comprises a binder matrix, a hardener and a solid lubricant, wherein the hardener and the solid lubricant are distributed through the binder matrix, wherein the binder matrix is a nickel-based composition selected from the group consisting of NiCr, Ni—Co, NiMoAl and combinations thereof, wherein the hardener is selected from the group consisting of glass, chrome carbide (Cr 3 C 2 ), chrome oxide and combinations thereof, and wherein the solid lubricant is selected from the group consisting of silver, calcium fluoride, barium fluoride and combinations thereof.

12. The seal of claim 11 , wherein the coating has a thickness of between 4 and 7 mils.

13. The seal of claim 11 , wherein the nanostructured, self-lubricating coating material is selected from the group consisting of NiCr—Cr 2 O 3 —Ag—BaF 2 /CaF 2 and NiMoAl—Cr 2 O 3 —Ag—BaF 2 /CaF 2 , and mixtures thereof.

14. The seal of claim 11 , wherein the seal comprises an age hardening austenitic nickel-based superalloy.