Thermal barrier coating compositions, methods of manufacture thereof and articles comprising the same
Disclosed herein is a process for coating a component, comprising applying a bond coat on a substrate of a component; applying a thermal barrier material to the bond coat; and applying a coating containing polynuclear aluminum oxide/hydroxide clusters, to the thermal barrier material. Disclosed herein too is a gas turbine engine component, comprising a superalloy substrate; a bond coat on the substrate; a thermal barrier material on the bond coat; and a coating containing polynuclear aluminum oxide/hydroxide clusters on the thermal barrier material.
1. A gas turbine engine component, comprising:
a superalloy substrate;
a bond coat on the substrate;
a thermal barrier material on the bond coat; and
a coating containing polynuclear aluminum oxide/hydroxide clusters on the thermal barrier material; wherein the polynuclear aluminum oxide/hydroxide clusters are Al 13 Keggin clusters having the formula [AlO 4 Al 12 (OH) 24 (H 2 O) 12 ] 7+ , or are salts of the Al 13 Keggin clusters called Al 13 Keggin complexes.
2. The component of claim 1 , wherein the coating further comprises a hydroxy aluminosilicate compound formed by coagulating the Al 13 Keggin clusters and/or the Al 13 Keggin complexes with an aqueous solution of sodium silicate, where the sodium silicate is present in an amount of about 0.01 to about 0.1 moles/liter in a solution that contains the Al 13 Keggin clusters and/or the Al 13 Keggin complexes, where the sodium silicate comprises sodium meta-silicate, sodium orthosilicate, disodium disilicate, or a combination thereof.
3. The component of claim 1 , wherein the coating comprises the Al 13 Keggin clusters and/or the Al 13 Keggin complexes in an amount of 0.007 to 0.07 moles/liter.
4. The component of claim 1 , wherein the Al 13 Keggin clusters and/or the Al 13 Keggin complexes are dried to form a pre-condensed coating of hydrated pseudo-boehmite (AlOOH*H 2 O), aluminum trihydroxide, or a combination thereof.
5. The component of claim 4 , further comprising heat treating the coating to form a fully dense transition alumina coating selected from the group consisting of χ-Al 2 O 3 , η-Al 2 O 3 or γ-Al 2 O 3 , and where the coating thickness is about 1 to about 1000 nanometers.
6. The component of claim 1 , wherein the Al 13 Keggin complex has the formula {[AlO 4 Al 12 (OH) 24 (H 2 O) 12 ] 7+ *7NO 3 − }.
7. The component of claim 1 , further comprising obtaining the Al 13 Keggin clusters and/or the Al 13 Keggin complexes by base neutralization of an aluminum salt solution, where the salt solution comprises a total aluminum concentration of about 0.02 to about 2.0 moles/liter, to obtain an (OH − /Al) mole ratio of about 2.1 to about 2.6.
8. The component of claim 1 , further comprising obtaining the Al 13 Keggin clusters and/or the Al 13 Keggin complexes by base neutralization of an aluminum salt solution, where the salt solution comprises a total aluminum concentration of about 0.02 to about 2.0 moles/liter, to obtain an (OH − /Al) mole ratio of about 2.2 to about 2.4.
9. The component of claim 1 , further comprising preparing the coating from a solution that comprises the Al 13 Keggin clusters and/or the Al 13 Keggin complexes in an amount of about 0.007 to about 0.07 moles/liter of the solution; where the solution comprises water or an organic solvent.
10. The component of claim 9 , further comprising precipitating the Al 13 Keggin clusters and/or the Al 13 Keggin complexes from a solution and collecting the Al 13 Keggin clusters and/or the Al 13 Keggin complexes by filtration, and drying the solution to form Al 13 Keggin cluster and/or Al 13 Keggin complex powder.
11. The component of claim 10 , further comprising redissolving the Al 13 Keggin cluster and/or Al 13 Keggin complex powder in water with a polymeric binder to form the coating.
12. The component of claim 11 , wherein an Al/Si atomic ratio ranges from about 5:1 to 15:1.
13. The component of claim 11 , wherein the coating comprises the Al 13 Keggin cluster and a hydroxy aluminosilicate compound and wherein the coating is applied by dipping, painting, spraying, electrostatic spraying, spin-coating, or a combination thereof.
14. The component of claim 1 , wherein the coating is applied by painting, spraying, electrostatic spraying, or spin-coating.
15. The component of claim 1 , further comprising drying the Al 13 Keggin clusters to form a pre-condensed coating of hydrated pseudo-boehmite (AlOOH*H 2 O), aluminum trihydroxide, or a combination thereof.
16. The component of claim 1 , further comprising heat treating the coating to form a fully dense transition alumina coating selected from the group consisting of χ-Al 2 O 3 , η-Al 2 O 3 and γ-Al 2 O 3 that has a thickness of about 1 to about 1000 nanometers.
17. The component of claim 1 , further comprising coagulating the Al 13 Keggin clusters and/or the Al 13 Keggin complexes with an aqueous solution of sodium silicate, where the sodium silicate is present in an amount of about 0.01 to about 0.1 moles/liter to form a hydroxy aluminosilicate compound, where the sodium silicate comprises sodium meta-silicate, sodium orthosilicate, disodium disilicate, or a combination thereof.