Methods for making environmental barrier coatings and ceramic components having CMAS mitigation capability

1. A method of making a component having calcium magnesium aluminosilicate (CMAS) mitigation capability, the method comprising:

providing a component comprising a ceramic matrix composite or a monolithic ceramic;

applying an environmental barrier coating to the component, the environmental barrier coating comprising:

a bond coat layer comprising silicon overlying the component;

an optional silica layer overlying the bond coat layer;

at least one transition layer overlying the bond coat layer or the optional silica layer comprising a composition selected from the group consisting of mullite, barium strontium aluminosilicate (BSAS), rare earth disilicates, and combinations thereof;

an optional outer layer comprising an outer layer material selected from the group consisting of BSAS, rare earth monosilicates, rare earth disilicates, and combinations thereof; and

a separate CMAS mitigation layer overlying the at least one transition layer or the optional outer layer, wherein the separate CMAS mitigation layer consists of Lna 4 Ga 2 O 9 and optionally one or more compositions selected from the group consisting of zinc aluminum spinel, alkaline earth zirconates, alkaline earth hafnates, rare earth aluminates, rare earth gallates, beryl, and combinations thereof, wherein the separate CMAS mitigation layer contains Lna 4 Ga 2 O 9 in an amount sufficient to prevent degradation of the environmental barrier coating due to reaction with CMAS.

2. The method of claim 1 , further comprising:

applying an abradable layer to the separate CMAS mitigation layer.

3. The method of claim 2 , wherein the abradable layer comprises Lna 4 Ga 2 O 9 , a rare earth disilicate, or BSAS.

4. The method of claim 1 , wherein the environmental barrier coating is applied by a method selected from the group consisting of plasma spraying, low pressure plasma spraying, solution plasma spraying, suspension plasma spraying, chemical vapor deposition, electron beam physical vapor deposition, sol-gel, sputtering, slurry dipping, slurry spraying, slurry painting, slurry rolling, tape-casting, and combinations thereof.

5. The method of claim 1 , wherein the component is a turbine engine component selected from the group consisting of combustor components, turbine blades, shrouds, nozzles, heat shields, and vanes.

6. A method of making a component having CMAS mitigation capability, the method comprising:

providing a component, wherein the component comprises a ceramic matrix composite or a monolithic ceramic;

applying an environmental barrier coating to the component, the environmental barrier coating comprising a bond coat layer comprising silicon overlying the component;

an optional silica layer overlying the bond coat layer;

at least one transition layer overlying the bond coat layer or the optional silica layer comprising a composition selected from the group consisting of mullite, barium strontium aluminosilicate (BSAS), rare earth disilicates, and combinations thereof;

an optional outer layer overlying the at least one transition layer, the optional outer layer comprising at least one outer layer material selected from the group consisting of BSAS, rare earth monosilicates, rare earth disilicates, and combinations thereof; and

an integrated CMAS mitigation layer overlying the at least one transition layer or the optional outer layer including:

at least one outer layer material; and

a CMAS mitigation composition comprising Lna 4 Ga 2 O 9 , wherein the integrated CMAS mitigation layer contains Lna 4 Ga 7 O 9 in an amount sufficient to prevent degradation of the environmental barrier coating due to reaction with CMAS.

7. The method of claim 6 , further comprising:

applying an abradable layer to the integrated CMAS mitigation layer.

8. The method of claim 7 , wherein the abradable layer comprises Lna 4 Ga 2 O 9 , a rare earth disilicate, or BSAS.

9. The method of claim 6 , wherein the environmental barrier coating is applied by a method selected from the group consisting of plasma spraying, low pressure plasma spraying, solution plasma spraying, suspension plasma spraying, chemical vapor deposition, electron beam physical vapor deposition, sol-gel, sputtering, slurry dipping, slurry spraying, slurry painting, slurry rolling, tape-casting, and combinations thereof.

10. The method of claim 6 , wherein the integrated CMAS mitigation layer comprises the CMAS mitigation composition as a grain boundary phase on the outer layer material or as dispersed refractory particles in the outer layer material.

11. The method of claim 6 , wherein the component is a turbine engine component selected from the group consisting of combustor components, turbine blades, shrouds, nozzles, heat shields, and vanes.

12. A method of making a component having CMAS mitigation capability comprising:

providing a component;

applying an environmental barrier coating to the component, the barrier coating comprising:

a bond coat layer comprising silicon;

an optional silica layer;

at least one transition layer comprising a composition selected from the group consisting of mullite, barium strontium aluminosilicate (BSAS), and combinations thereof;

an optional outer layer comprising an outer layer material selected from the group consisting of BSAS, rare earth monosilicates, rare earth disilicates, and combinations thereof; and

a separate CMAS mitigation layer consisting of Lna 4 Ga 2 O 9 and optionally one or more compositions selected from the group consisting of zinc aluminum spinel, alkaline earth zirconates, alkaline earth hafnates, rare earth aluminates, rare earth gallates, beryl, and combinations thereof or an integrated CMAS mitigation layer comprising Lna 4 Ga 2 O 9 and at least one outer layer material, wherein the separate CMAS mitigation layer or the integrated CMAS mitigation layer contains Lna 4 Ga 2 O 9 in an amount sufficient to prevent degradation of the environmental barrier coating due to reaction with CMAS.

13. The method of claim 12 further comprising:

applying an abradable layer to the separate CMAS mitigation layer or the integrated CMAS mitigation layer.

14. The method of claim 13 , wherein the abradable layer comprises Lna 4 Ga 2 O 9 , a rare earth disilicate, or BSAS.

15. The method of claim 12 , wherein the environmental barrier coating is applied by a method selected from the group consisting of plasma spraying, low pressure plasma spraying, solution plasma spraying, suspension plasma spraying, chemical vapor deposition, electron beam physical vapor deposition, sol-gel, sputtering, slurry dipping, slurry spraying, slurry painting, slurry rolling, tapecasting, and combinations thereof.

16. The method of claim 12 , wherein the integrated CMAS mitigation layer comprises the CMAS mitigation composition as a grain boundary phase on the outer layer material or as dispersed refractory particles in the outer layer material.

17. The method of claim 12 , wherein the component comprises a ceramic matrix composite or a monolithic ceramic.

18. The method of claim 12 , wherein the component is a turbine engine component selected from the group consisting of combustor components, turbine blades, shrouds, nozzles, heat shields, and vanes.