Structure and method for protecting a hybrid ceramic structure from moisture attack in a high temperature environment

1. A hybrid ceramic structure for use in a high temperature combustion environment containing moisture, the structure comprising:

a ceramic matrix composite (CMC) substrate;

a thermal insulation material disposed on the substrate,

the CMC substrate and the thermal insulation material comprising respective materials susceptible to recession when subjected to temperatures of approximately 1,500° C. and higher in a combustion environment containing moisture and having respective subsurface cracks or fractures which are inaccessible from respective outward surfaces of the hybrid ceramic structure; and

a coating of water vapor resistant material on respective inner surfaces of at least some of the cracks or fractures in the CMC substrate to form respective moisture-resistant layers onto the respective inner surfaces of said at least some of the cracks or fractures as the hybrid ceramic structure transitions from a bisque condition to a fully fired condition.

2. The hybrid ceramic structure of claim 1 , wherein the coating of water vapor resistant material ranges in thickness from 0.11 microns to 50 microns on the respective inner surfaces of the cracks or fractures in the CMC substrate.

3. The hybrid ceramic structure of claim 1 , wherein the water vapor re-sistant material is selected from the group consisting of a pyrochlore structure; HfSiO 4 ; ZrSiO 4 ; Y 2 Si 2 O 7 ; Y 2 O 3 ; ZrO 2 , HfO 2 ; yttria and/or ZrO 2 stabilized by at least one rare earth element; yttria and/or HfO 2 stabilized by at least one rare earth element; yttria and/or ZrO 2 /HfO 2 stabilized by at least one rare earth element; a rare earth silicate of the form RE 2 Si 2 O 7 ; a rare earth oxide of the form RE 2 O 3 ; and a rare earth zirconate or hafnate of the form RE 4 Zr 3 O 12 or RE 4 Hf 3 O 12 , wherein the rare earth element is selected from the group consisting of: Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

4. The hybrid ceramic structure of claim 1 , wherein the water vapor resistant material fills at least some of the cracks or fractures in the CMC substrate.

5. The hybrid ceramic structure of claim 1 , wherein the water vapor resistant material partly fills at least some of the cracks or fractures in the CMC substrate.

6. The hybrid ceramic structure of claim 1 , wherein the water vapor resistant material forms a coating of water vapor resistant material on respective inner surfaces of at least some of the cracks or fractures in the thermal insulation material to form respective moisture-resistant layers onto the respective inner surfaces of said at least some of the cracks or fractures in the thermal insulation material during the transition.

7. The hybrid ceramic structure of claim 6 , wherein the water vapor resistant material fills at least some of the cracks or fractures in the thickness of the thermal insulation material.

8. The hybrid ceramic structure of claim 6 , wherein the water vapor resistant material partly fills at least some of the cracks or fractures in the thickness of the thermal insulation material.

9. A hybrid ceramic structure for use in a high temperature combustion environment containing moisture, the structure comprising:

a ceramic matrix composite (CMC) substrate;

a thermal insulation material disposed on the substrate,

the CMC substrate and the thermal insulation material comprising respective materials susceptible to recession when subjected to high temperature water vapor and having respective subsurface cracks or fractures which are inaccessible from respective outward surfaces of the hybrid ceramic structure,

wherein the CMC substrate comprises a material selected from the group consisting of silica-based materials, silica-based non-oxides, oxide matrix composites, mullite, aluminosilicate, alumina, silicon carbide composites, and silicon nitride composites, and

wherein the thermal insulation material comprises a material selected from the group consisting of mullite, mullite and stabilized zirconia, mullite and alumina, alumina, stabilized zirconia, ceria, and refractory forms of aluminum phosphate; and

a coating of water vapor resistant material on respective inner surfaces of at least some of the cracks or fractures in the CMC substrate to form respective moisture-resistant layers onto the respective inner surfaces of said at least some of the cracks or fractures as the hybrid ceramic structure transitions from a bisque condition to a fully fired condition.

10. The hybrid ceramic structure of claim 9 , wherein the water vapor resistant material fills at least some of the cracks or fractures in the CMC substrate.

11. The hybrid ceramic structure of claim 6 , wherein the water vapor resistant material partly fills at least some of the cracks or fractures in the CMC substrate.

12. The hybrid ceramic structure of claim 6 , wherein the water vapor resistant material forms a coating of water vapor resistant material on respective inner surfaces of at least some of the cracks or fractures in the thermal insulation material to form respective moisture-resistant layers onto the respective inner surfaces of said at least some of the cracks or fractures in the thermal insulation material during the transition.

13. The hybrid ceramic structure of claim 12 , wherein the water vapor resistant material fills at least some of the cracks or fractures in the thickness of the thermal insulation material.

14. The hybrid ceramic structure of claim 12 , wherein the water vapor resistant material partly fills at least some of the cracks or fractures in the thickness of the thermal insulation material.