Selectively coated gas path surfaces within a hot section of a gas turbine engine

1. An apparatus for a gas turbine engine, comprising:

a hot section structure of the gas turbine engine;

the hot section structure configured with a plurality of surfaces respectively forming boundaries of a gas path through the hot section structure, the plurality of surfaces including an uncoated first surface and a second surface; and

the hot section structure including metal and thermal barrier material, the uncoated first surface formed by the metal, and the second surface formed by the thermal barrier material;

wherein the uncoated first surface is formed by the metal such that the metal forming the uncoated first surface is configured to be directly exposed to hot gas flowing through the gas path; and

wherein the hot section structure comprises a vane, and the thermal barrier material forms at least a portion of a trailing edge of the vane.

2. The apparatus of claim 1 , wherein the thermal barrier material comprise ceramic.

3. The apparatus of claim 1 , wherein the uncoated first surface is contiguous with the second surface.

4. The apparatus of claim 1 , wherein

the gas path extends longitudinally through the hot section structure; and

the uncoated first surface is longitudinally aligned with the second surface.

5. The apparatus of claim 1 , wherein

the gas path extends longitudinally through the hot section structure; and

the uncoated first surface is laterally aligned with the second surface.

6. The apparatus of claim 1 , wherein at least a portion of the uncoated first surface is upstream of the second surface along the gas path.

7. The apparatus of claim 6 , further comprising a combustor section upstream of the hot section structure along the gas path.

8. The apparatus of claim 1 , wherein

the vane extends across the gas path; and

the vane includes the uncoated first surface and the second surface.

9. The apparatus of claim 8 , wherein the thermal barrier material forms at least seventy-five percent of an external surface area of the vane that is exposed to the gas path.

10. The apparatus of claim 1 , wherein

the hot section structure further comprises a gas path wall;

the vane projects out from the gas path wall;

the gas path wall comprises the uncoated first surface; and

the vane comprises the second surface.

11. The apparatus of claim 1 , wherein

at least a portion of the uncoated first surface has a straight sectional geometry; and

at least a portion of the second surface has a curved sectional geometry.

12. The apparatus of claim 1 , wherein the hot section structure comprises a turbine exhaust structure.

13. The apparatus of claim 1 , wherein the hot section structure comprises a turbine support structure.

14. The apparatus of claim 1 , wherein the hot section structure comprises a vane array structure.

15. An apparatus for a gas turbine engine, comprising:

a hot section structure of the gas turbine engine;

the hot section structure configured with a plurality of surfaces respectively forming boundaries of a gas path through the hot section structure, the plurality of surfaces including an uncoated first surface and a second surface; and

the hot section structure including metal and thermal barrier material, the uncoated first surface formed by the metal, and the second surface formed by the thermal barrier material;

wherein a portion of the hot section structure forming the uncoated first surface is configured without any thermal barrier material; and

wherein the hot section structure comprises a vane, and the thermal barrier material forms at least a portion of a trailing edge of the vane.