Coating fabrication method for producing engineered microstructure of silicate-resistant barrier coating
A coating fabrication method includes providing engineered granules and thermally consolidating the engineered granules on a substrate to form a silicate-resistant barrier coating. Each of the engineered granules is an aggregate of at least one refractory matrix region and at least one calcium aluminosilicate additive region (CAS additive region) attached with the at least one refractory matrix region. In the thermal consolidation, the refractory matrix region from the engineered granules form grains of a refractory matrix of the silicate-resistant barrier coating and the CAS additive region from the engineered granules form CAS additives that are dispersed in grain boundaries between the grains.
1. A coating fabrication method comprising:
providing engineered granules, wherein each said engineered granule is an aggregate of:
at least one refractory matrix region, and
at least one calcium aluminosilicate additive region (CAS additive region) attached with the at least one refractory matrix region; and
thermally consolidating the engineered granules on a substrate to form a silicate-resistant barrier coating, wherein in the thermal consolidation the at least one refractory matrix region from the engineered granules form grains of a refractory matrix of the silicate-resistant barrier coating and the at least one CAS additive region from the engineered granules form CAS additives that are dispersed in grain boundaries between the grains.
2. The method as recited in claim 1 , wherein each said engineered granule is a mixed granule that has a plurality of the refractory matrix regions and a plurality of the CAS additive regions attached with the plurality of refractory matrix regions.
3. The method as recited in claim 1 , wherein each said engineered granule is a core/shell granule in which the at least one refractory matrix region is a coarse core particle and the at least one CAS additive region is a plurality of fine shell particles attached on the coarse core particle.
4. The method as recited in claim 1 , wherein each said engineered granule is a core/shell granule in which the at least one refractory matrix region is a coarse core particle and the at least one CAS additive region is a shell coating attached on the coarse core particle.
5. The method as recited in claim 1 , wherein each said engineered granule is selected from a mixed granule, a core/shell granule, or combinations thereof, wherein the mixed granule has a plurality of the refractory matrix regions and a plurality of the CAS additive regions attached with the plurality of refractory matrix regions, and the core/shell granule in which the at least one refractory matrix region is a coarse core particle and the at least one CAS additive region is selected from a plurality of fine shell particles attached on the coarse core particle and a shell coating on the coarse core particle.
6. The method as recited in claim 5 , wherein the at least one refractory matrix region is selected from zirconia, hafnia, hafnium silicate, zirconium silicate, rare earth silicates, rare earth oxides, mullite, silica, aluminum oxide and combinations thereof, and the at least one CAS additive region includes SiO 2 , AlO 1.5 , and CaO.
7. The method as recited in claim 6 , wherein the substrate is a ceramic matrix composite composed of silicon carbide fibers in a silicon carbide matrix.
8. The method as recited in claim 1 , wherein the at least one CAS additive region is attached with the at least one refractory matrix region by sintering.
9. The method as recited in claim 1 , wherein the at least one CAS additive region is attached with the at least one refractory matrix region by electrostatic force.
10. The method as recited in claim 1 , wherein the at least one CAS additive region is attached with the at least one refractory matrix region by a binder.
11. The method as recited in claim 1 , wherein the at least one refractory matrix region has a size of greater than 10 micrometers, and the at least one CAS additive region has a size of less than 5 micrometers.
12. The method as recited in claim 1 , wherein the at least one refractory matrix region has a size of less than 5 micrometers, and the at least one CAS additive region has a size of less than 5 micrometers.
13. The method as recited in claim 1 , wherein each said engineered granule additionally includes at least one auxiliary refractory matrix region attached with the at least one refractory matrix region and the at least one CAS additive region, and in the thermal consolidation the refractory matrix region and the auxiliary refractory matrix region form the grains of the refractory matrix of the silicate-resistant barrier coating.
14. The method as recited in claim 1 , wherein the thermal consolidation includes thermally consolidating the engineered granules with auxiliary refractory matrix regions, and the refractory matrix region of the engineered granules and the auxiliary refractory matrix regions form the grains of the refractory matrix of the silicate-resistant barrier coating.
15. The method as recited in claim 1 , wherein the providing of the engineered granules includes forming the at least one refractory matrix region and the at least one CAS additive region into the aggregate.