Ceramic compositions for thermal barrier coatings with improved mechanical properties
Zirconia-containing ceramic compositions useful for thermal barrier coatings having improved mechanical properties, especially improved fracture toughness. These compositions comprise: (1) at least about 93 mole % zirconia; (2) a stabilizing amount up to about 5 mole % of a stabilizer metal oxide selected from the group consisting of yttria, calcia, ceria, scandia, magnesia, india, gadolinia, neodymia, samaria, dysprosia, erbia, ytterbia, europia, praseodymia, and mixtures thereof, and a fracture toughness improving amount up to about 2 mole % lanthana. These ceramic compositions can be used to prepare thermal barrier coatings to provide a thermally protected article having a substrate and optionally a bond coat layer adjacent to and overlaying the substrate. The thermal barrier coating can be prepared by depositing the ceramic composition on the bond coat layer or the substrate in the absence of a bond coat layer.
1. An article, which comprises a thermal barrier coating which consists essentially of:
1. at least about 93 mole % zirconia;
2. a stabilizing amount up to about 5 mole % of a stabilizer metal oxide selected from the group consisting yttria, calcia, ceria, scandia, magnesia, india, gadolinia, neodymia, samaria, dysprosia, erbia, ytterbia, europia, praseodymia, and mixtures thereof; and
3. a fracture toughness improving amount of from about 1 to about 2 mole % lanthana.
2. The article of claim 1 wherein the thermal barrier coating consists essentially of from about 93 to about 95.5 mole % zirconia.
3. The article of claim 2 wherein the thermal barrier coating consists essentially of from about 3 to about 5 mole % stabilizer metal oxide.
4. The article of claim 3 wherein the thermal barrier coating consists essentially of from about 4 to about 5 mole % stabilizer metal oxide.
5. The article of claim 4 wherein the stabilizer metal oxide is yttria.
6. The article of claim 1 wherein the thermal barrier coating consists essentially of from about 94 to about 95 mole % zirconia.
7. A thermally protected article, which comprises:
A. a substrate; and
B. a thermal barrier coating consisting essentially of:
1. at least about 93 mole % zirconia; and
2. a stabilizing amount up to about 5 mole % of a stabilizing metal oxide selected from the group consisting of yttria, calcia, ceria, scandia, magnesia, india, gadolinia, neodymia, samaria, dysprosia, erbia, ytterbia, europia, praseodymia, and mixtures thereof; and
3. a fracture toughness improving amount of from about 1 to about 2 mole % lanthana.
8. The article of claim 7 wherein the substrate is a metal substrate, wherein the article further comprises a bond coat layer adjacent to and overlaying the metal substrate and wherein the thermal barrier coating is adjacent to and overlies the bond coat layer.
9. The article of claim 8 wherein the thermal barrier coating has a thickness of from about 1 to about 100 mils.
10. The article of claim 9 wherein the thermal barrier coating consists essentially of from about 93 to about 95.5 mole % zirconia.
11. The article of claim 10 wherein the thermal barrier coating consists essentially of from about 94 to about 95 mole % zirconia.
12. The article of claim 9 which is a turbine engine component.
13. The article of claim 12 which is a turbine shroud and wherein the thermal barrier coating has a thickness of from about 30 to about 70 mils.
14. The article of claim 12 which is a turbine airfoil and wherein the thermal barrier coating has a thickness of from about 3 to about 15 mils.
15. The article of claim 9 wherein the thermal barrier coating consists essentially of from about 3 to about 5 mole % stabilizer metal oxide.
16. The article of claim 15 wherein the thermal barrier coating consists essentially of from about 4 to about 5 mole % stabilizer metal oxide.
17. The article of claim 16 wherein the stabilizer metal oxide is yttria.
18. A method for preparing a thermal barrier coating for an underlying substrate, the method comprising the step of:
a. depositing over the substrate a zirconia-containing ceramic composition to form a thermal barrier coating, the zirconia-containing ceramic composition consisting essentially of:
1. at least about 93 mole % zirconia; and
2. a stabilizing amount up to about 5 mole % of a stabilizer metal oxide selected from the group consisting of yttria, calcia, ceria, scandia, magnesia, india, gadolinia, neodymia, samaria, dysprosia, erbia, ytterbia, europia, praseodymia, and mixtures thereof; and
3. a fracture toughness improving amount of from about 1 to about 2 mole % lanthana.
19. The method of claim 18 wherein the substrate is a metal substrate, wherein a bond coat layer is adjacent to and overlies the metal substrate and wherein the thermal barrier coating is formed on the bond coat layer.
20. The method of claim 19 wherein the ceramic composition is deposited by physical vapor deposition to form a thermal barrier coating having a strain-tolerant columnar structure.
21. The method of claim 20 wherein the ceramic composition deposited consists essentially of from about 93 to about 95.5 mole % zirconia.
22. The method of claim 21 wherein the ceramic composition deposited consists essentially of from about 3 to about 5 mole % yttria as a stabilizer metal oxide.