EBC with mullite bondcoat that includes an oxygen getter phase
A coated component, along with methods of its formation and use, is provided. The coated component includes a ceramic matrix composite (CMC) substrate comprising silicon carbide and having a mullite bondcoat on its surface. The mullite bondcoat includes an oxygen getter phase contained within a mullite phase. For example, the mullite bondcoat may include 60% to 98% by volume of the mullite phase. An environmental barrier coating is on the mullite bondcoat.
1. A coated component comprising:
a ceramic matrix composite (CMC) substrate comprising silicon carbide and having a surface;
a mullite bondcoat on the surface of the substrate, wherein the mullite bondcoat comprises an oxygen getter phase contained within a mullite phase, wherein the mullite phase is a continuous phase, and wherein the oxygen getter phase forms a plurality of discrete phases within the mullite phase, wherein the mullite bondcoat has a thickness of 10 mils or less, and wherein the mullite bondcoat comprises 60% to 98% by volume of the mullite phase; and
an environmental barrier coating on the mullite bondcoat.
2. The coated component as in claim 1 , wherein the mullite bondcoat comprises 65% to 96% by volume of the mullite phase.
3. The coated component as in claim 1 , wherein the mullite bondcoat comprises 75% to 95% by volume of the mullite phase.
4. The coated component as in claim 1 , wherein the mullite phase comprises alumina and silica in a stoichiometric ratio within 10% of 3 to 2.
5. The coated component as in claim 1 , wherein the mullite phase comprises alumina and silica in a stoichiometric ratio within 10% of 2 to 1.
6. The coated component as in claim 1 , wherein the mullite phase consists of alumina and silica.
7. The coated component as in claim 1 , wherein the mullite phase comprises alumina and silica in a stoichiometric ratio of at least 3 to 2 and up to 3.5 to 2.
8. The coated component as in claim 1 , wherein the mullite phase comprises alumina and silica in a stoichiometric ratio of at least 2 to 1 and up to 2.25 to 1.
9. The coated component as in claim 1 , wherein the oxygen getter phase comprises a silicon-phase.
10. The coated component as in claim 9 , wherein the silicon-phase comprises elemental silicon.
11. The coated component as in claim 10 , wherein the mullite bondcoat comprises 2% to 40% by volume elemental silicon.
12. The coated component as in claim 1 , wherein the oxygen getter phase forms a plurality of discrete particulate phases within the mullite phase.
13. The coated component as in claim 1 , wherein the mullite phase spans a thickness of the mullite bondcoat and is bonded directly to the surface of the substrate and to an inner surface of the environmental barrier coating.
14. The coated component as in claim 1 , wherein the environmental barrier coating comprises a plurality of layers with at least one of the layers of the environmental barrier coating comprises a hermetic layer.
15. The coated component of claim 14 , wherein the hermetic layer is adjacent to the mullite bondcoat such that the hermetic layer defines an inner surface of the environmental barrier coating.
16. The coated component as in claim 1 , wherein the mullite bondcoat is configured to withstand exposure to operating temperatures of about 1475° C. to about 1650° C.
17. The coated component as in claim 1 , wherein the oxygen getter phase comprises elemental silicon, and wherein the environmental barrier coating comprises a hafnia layer, an alumina layer, or both.
18. The coated component as in claim 1 , wherein the oxygen getter phase comprises elemental silicon, and wherein the environmental barrier coating comprises a rare earth disilicate layer, a rare earth monosilicate layer, or both.
19. The coated component as in claim 18 , wherein the environmental barrier coating further comprises a hafnia layer.
20. A method of forming a coated component, the method comprising:
forming a mullite bondcoat on a surface of a substrate, wherein the mullite bondcoat comprises a silicon-phase contained within a mullite phase, wherein the mullite phase is a continuous phase, and wherein the silicon-phase forms a plurality of discrete phases within the mullite phase, wherein the mullite bondcoat has a thickness of 10 mils or less, and wherein the mullite bondcoat comprises 60% to 95% by volume of the mullite phase; and
forming an environmental barrier coating on the mullite bondcoat such that the silicon-phase, when melted, is contained within mullite phase between the surface of the substrate and an inner surface of the environmental barrier coating.