Layered thermal barrier coatings containing lanthanide series oxides for improved resistance to CMAS degradation

Abstract

A coating applied as a two layer system. The outer layer is an oxide of a group IV metal selected from the group consisting of zirconium oxide, hafnium oxide and combinations thereof, which are doped with an effective amount of a lanthanum series oxide. These metal oxides doped with a lanthanum series addition comprises a high weight percentage of the outer coating. As used herein, lanthanum series means an element selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) and combinations thereof, and lanthanum series oxides are oxides of these elements. When the zirconium oxide is doped with an effective amount of a lanthanum series oxide, a dense reaction layer is formed at the interface of the outer layer of TBC and the CMAS. This dense reaction layer prevents CMAS infiltration below it. The second layer, or inner layer underlying the outer layer, comprises a layer of partially stabilized zirconium oxide.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a cross-section of the present invention applied to a component substrate before being placed into service.

FIG. 2 depicts a cross-section of a substrate coated with the present invention at 300 magnification after exposure to CMAS at 2350° F. for one hour.

FIG. 3 depicts a cross-section of a substrate coated with the present invention after exposure to CMAS at 2350° F. for one hour, showing the location of microprobe sampling at six locations.

Claims

1. A CMAS infiltration-resistant thermal barrier coating system for application to a substrate, comprising: a bond coat (16) applied to the substrate (14); anda thermal barrier coating applied overlying the bond coat (16), the thermal barrier coating including an inner layer (20) consisting essentially of zirconium oxide partially stabilized with less than 20 weight percent yttria and an outer layer (22) applied overlying the inner layer comprising an oxide of a group IV metal selected from the group consisting of zirconia and hafnia, the oxide doped with an effective amount of a lanthanum series based oxide, wherein the lanthanum series based oxide is selected from oxides of the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu and combinations thereof;wherein the ratio of thickness of the outer layer (22) to the inner layer (20) is about 0.05:1 to about 7:1.

2. The CMAS infiltration-resistant thermal barrier coating system of claim 1 further including a coating of alumina (24) overlying the outer layer (22) of the thermal barrier coating, the outer layer (22).

3. The CMAS infiltration-resistant thermal barrier coating system of claim 2 further including a dense layer (48) located intermediate a CMAS reaction zone (44) and an unaffected zone (46).

4. The CMAS infiltration-resistant thermal barrier coating system of claim 1 wherein the thermal barrier coating overlying the bond coat includes an outer layer that comprises zirconium oxide doped with the effective amount of a lanthanum series based oxide.

5. The CMAS infiltration-resistant thermal barrier coating system of claim 4 wherein the outer layer is doped with the effective amount of a lanthanum series oxide that includes pyrochlore phase zirconates, wherein pyrochlore phase zirconates comprise Zr2X2O7, where X is an element selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and combinations thereof.

6. The CMAS infiltration-resistant thermal barrier coating system of claim 5 wherein pyrochlore phase zirconates comprise Zr2X2O7, where X is an element selected from the group consisting of La, Nd, Sm, Eu, Gd and combinations thereof.

7. The CMAS infiltration-resistant thermal barrier coating system of claim 1 wherein the thermal barrier coating applied overlying the bond coat has a thickness of about 0.010-0.080 inches with a ratio of outer layer thickness to inner layer thickness in the range of from about 0.15:1 to 7:1.

8. The CMAS infiltration-resistant thermal barrier coating system of claim 7 wherein the thickness of the inner layer is from about 0.005-0.040 inches.

9. The CMAS infiltration-resistant thermal barrier coating system of claim 1 wherein the thermal barrier coating applied overlying the bond coat has a thickness of about 0.004-0.015 inches with a ratio of outer layer thickness to inner layer thickness in the range of from about 0.05:1 to 1:1.

10. The CMAS infiltration-resistant thermal barrier coating system of claim 9 wherein the thickness of the inner layer is from about 0.0005-0.010 inches.

11. The CMAS infiltration-resistant thermal coating system of claim 1 wherein the inner layer consists essentially of yttria stabilized zirconia (YSZ) having from 2-10% by weight yttria and the balance zirconia.

12. The CMAS infiltration-resistant thermal barrier coating system of claim 1 wherein the effective amount of effective amount of a lanthanum series based oxide in the outer layer includes in mole percent greater than 20 up to 70 percent of an oxide selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu and combinations thereof.

13. The CMAS infiltration-resistant thermal barrier coating system of claim 12 wherein the effective amount of the lanthanum series based oxide is 30-70 mole percent.

14. A component having a CMAS infiltration-resistant thermal barrier coating system, comprising: a substrate (30) having a surface;a bond coat (16) applied to the substrate surface;a thermal barrier coating (32) applied over the bond coat (16), the thermal barrier coating (30) including an inner layer (40) consisting essentially of partially zirconium oxide stabilized with less than 20 weight percent yttria applied over the bond coat (16), and an outer layer (42) formed over the inner layer (40) comprising an oxide of a group IV metal selected from the group consisting of zirconia and hafnia, the oxide doped with an effective amount of a lanthanum series based oxide, wherein the lanthanum series based oxide is are selected from oxides of the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and combinations thereof;wherein the ratio of thickness of the outer layer (42) to the inner layer (40) is about 0.05:1 to about 7:1,and wherein the outer layer includes a dense layer (48) positioned intermediate a CMAS reaction zone (44) and an unaffected zone (46).

15. The component of claim 14 further including a layer of alumina (24) overlying the outer layer (22).

16. The component of claim 14 wherein the thermal barrier coating overlying the bond coat includes an outer layer that comprises zirconium oxide doped with the effective amount of a lanthanum series based oxide.

17. The component of claim 16 wherein the outer layer is doped with the effective amount of a lanthanum series oxide that includes pyrochlore phase zirconates, wherein pyrochlore phase zirconates comprise Zr2X2O7, where X is an element selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu and combinations thereof.

18. The component of claim 17 wherein pyrochlore phase zirconates comprise Zr2X2O7, where X is an element selected from the group consisting of La, Nd, Sm, Eu, Gd and combinations thereof.

19. The component of claim 14 including a gas turbine engine component for an aircraft engine wherein the component is a stationary component adjacent to a rotating component.

20. The component of claim 19 wherein the component is a turbine shroud.

21. The component of claim 14 wherein the thermal barrier coating applied overlying the bond coat has a thickness of about 0.010-0.080 inches with a ratio of outer layer thickness to inner layer thickness in the range of from about 0:15 to 7:1.

22. The CMAS infiltration-resistant thermal barrier coating system of claim 21 wherein the thickness of the inner layer is from about 0.005-0.040 inches.

23. The component of claim 14 including an gas turbine engine component for an aircraft engine wherein the component is an airfoil wherein the thermal barrier coating applied overlying the bond coat has a thickness of about 0.004-0.015 inches with a ratio of outer layer thickness to inner layer thickness in the range of from about 0.05:1 to 1:1.

24. The component of claim 14 including an gas turbine engine component for an aircraft engine wherein the component is a rotating component and wherein the thermal barrier coating applied overlying the bond coat has a thickness of about 0.004-0.015 inches with a ratio of outer layer thickness to inner layer thickness in the range of from about 0.05:1 to 1:1.

25. The CMAS infiltration-resistant thermal barrier coating system of claim 14 wherein the thickness of the inner layer is from about 0.0005-0.010 inches.

26. The CMAS infiltration-resistant thermal coating system of claim 14 wherein the inner layer consists essentially of yttria stabilized zirconia (YSZ) having from 2-10% by weight yttria and the balance zirconia.

27. The CMAS infiltration-resistant thermal barrier coating system of claim 14 wherein the effective amount of a lanthanum series based oxide in the outer layer includes greater than 20 mole percent up to 70 mole percent of an oxide selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu and combinations thereof.

28. The CMAS infiltration-resistant thermal barrier coating system of claim 27 wherein the effective amount of the lanthanum series based oxide is 50-70 mole percent in the unaffected zone 46 of the outer layer.