Protective aluminum oxide surface coatings and low-temperature forming process for high-temperature applications

1. A method for both coating a substrate with aluminum oxide and infusing the substrate with elemental aluminum, the method comprising:

providing a substrate having a Cr-containing surface;

providing a metal powder/polymer binder slurry, the slurry comprising:

a solvent;

an organic binder;

metal granules, wherein the metal granules comprise Al; and

a seed element;

dispersing the slurry upon the Cr-containing surface;

after dispersing the slurry, exposing the slurry to air and maintaining the temperature of the slurry and substrate below 110° C., to remove at least a portion of the solvent from the slurry; and

after removing at least a portion of the solvent from the slurry, in a combined step, both exposing the binder, metal granules, seed elements, and substrate to air and heating the remaining slurry and substrate at a temperature less than or equal to 1000° C. to:

diffuse the at least a portion of the metal of the metal granules into the substrate;

oxidize the seed elements to form one or more of a cubic crystal lattice structure, a tetragonal metal oxide crystal structure, and/or a trigonal metal oxide crystal structure; and

coat the substrate with aluminum oxide.

2. The method of claim 1 , wherein said maintaining further comprises maintaining the temperature of the slurry and substrate above 80° C.

3. The method of claim 1 , wherein said heating comprises heating at a temperature between 700° C. and 900° C.

4. The method of claim 1 , wherein the seed element comprises Ti.

5. The method of claim 1 , wherein the seed element comprises Cr.

6. The method of claim 1 , wherein the seed element comprises Mn.

7. The method of claim 1 , wherein the seed element comprises Fe.

8. The method of claim 1 , wherein the substrate has a Cr—Fe containing surface.

9. The method of claim 8 , wherein the Cr—Fe-containing surface further comprises one or both of Co and Ni.

10. The method of claim 1 , the metal granules on average are between 0.1 and 45 μm in diameter.

11. The method of claim 1 , wherein the metal powder/polymer binder slurry comprises organic constituents that carburize and/or volatilize at temperatures near or above the melting point of the metal.

12. The method of claim 1 , wherein during the combined step at least a portion of the aluminum is oxidized.

13. The method of claim 1 , wherein the metal of the metal granules comprises an aluminum alloy.

14. The method of claim 1 , wherein the binder of the metal powder/polymer binder slurry is an organic based system having a final evaporation or decomposition temperature greater than 100° C.

15. The method of claim 1 , wherein during the exposing the slurry to air and maintaining the temperature of the slurry and substrate below 110° C. step, the metal of the metal powder/polymer binder slurry remains unoxidized.

16. The method of claim 1 , wherein the metal powder/polymer binder slurry comprises a ratio of binder to powder within the range of 10:1 to 1:10 by volume.

17. The method of claim 1 , wherein the dispersing the slurry upon the Cr-containing surface comprises applying the slurry by spray dispensing, paste dispensing, painting, dip coating, stencil printing, or screen printing.

18. The method of claim 1 , wherein the aluminum oxide comprises α-aluminum oxide.

19. The method of claim 1 , operating as a continuous process on a plurality of substrates.

20. The method of claim 1 , wherein the metal substrate is a component of a solid oxide fuel cell stack or a boiler device.