Thermal management of CMC articles having film holes

1. An engine component for a gas turbine engine generating hot combustion gas flow, comprising:

a substrate constructed from a ceramic matrix composite (CMC) material and having a hot surface facing the hot combustion gas flow and a cooling surface facing a cooling fluid flow, wherein the substrate defines a film hole extending through the substrate and having an inlet provided on the cooling surface, an outlet provided on the hot surface, and a passage defined at least in part by an inner surface and connecting the inlet and the outlet; and

a coating having a thermal conductivity that is less than a thermal conductivity of the CMC substrate, wherein the coating is on at least a portion of the hot surface and on at least a portion of the inner surface defined within the passage.

2. The engine component as in claim 1 , wherein the thermal conductivity of the CMC substrate is 10 times greater than the thermal conductivity of the coating or more.

3. The engine component as in claim 1 , wherein the thermal conductivity of the CMC substrate is 100 times greater than the thermal conductivity of the coating or more.

4. The engine component as in claim 1 , wherein the coating is on at least a portion of the hot surface, on at least a portion of an inner surface defined within the passage, and on at least a portion of the cold surface.

5. The engine component as in claim 2 , wherein the coating has a length extending away from respective film hole edge along the cooling surface, the length being about 0.5 times to about 5 times an inlet diameter in a direction of the hot combustion gas flow.

6. The engine component as in claim 1 , wherein the coating perimetrically surrounds the hot surface around the outlet defined in the hot surface.

7. The engine component as in claim 6 , wherein the coating extends across the entire hot surface of the substrate.

8. The engine component as in claim 1 , wherein the coating has a thickness defined from an external surface of the coating to the hot surface of the substrate in a direction perpendicular to hot combustion gas flow, the thickness being about 1000 μm or less.

9. The engine component as in claim 1 , wherein the coating extends around at least 50% of a downstream edge of the outlet.

10. The engine component as in claim 1 , wherein the inner surface is an upstream inner surface, wherein the engine component further comprises a downstream inner surface, and wherein the coating is over at least a portion of the upstream inner surface and at least a portion of the downstream inner surface.

11. The engine component as in claim 10 , wherein the coating is on the upstream inner surface through at least 50% of the depth from the outlet to the inlet.

12. The engine component as in claim 10 , wherein the coating is on the upstream inner surface through at least 75% of the depth from the outlet to the inlet.

13. The engine component as in claim 10 , wherein the coating is on the upstream inner surface from the outlet to the inlet.

14. The engine component as in claim 10 , wherein the coating is on the downstream inner surface through at least 50% of the depth from the outlet to the inlet.

15. The engine component as in claim 10 , wherein the coating is on the downstream inner surface through at least 75% of the depth from the outlet to the inlet.

16. The engine component as in claim 10 , wherein the coating is on the downstream inner surface from the outlet to the inlet.

17. The engine component as in claim 1 , wherein the coating completely covers all surfaces defined within the passage.

18. The engine component as in claim 1 , wherein the coating is over a thermal barrier coating forming the hot surface of the substrate.

19. A gas turbine engine comprising:

a compressor;

a combustor;

a turbine;

the engine component of claim 1 .

20. The engine component as in claim 1 , wherein the coating is an environmental barrier coating.