Alloy Castings Having Protective Layers and Methods of Making the Same

• US 20090314390A1
• Filed: 06/24/2008
• Published: 12/24/2009
• Est. Priority Date: 06/24/2008
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Petterson, Roger John, Gigliotti, Michael Frances Xavier JR., Huang, Shyh-Chin, Iorio, Luana Emiliana, Rutkowski, Stephen Francis, Elliott, Andrew John
• Granted Patent: US 8,906,170 B2
• Time in Patent Office: Days
• US Class Current: 148/284
• CPC Class Codes: B22D 19/08 for building-up linings or coverings, e.g. of anti-frictional metal
• CPC Class Codes: C23C 30/00 Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process C23C26/00, C23C28/00 take precedence
• CPC Class Codes: C23C 8/10 Oxidising
• CPC Class Codes: F01D 5/28 Selecting particular materials; Particular measures relating thereto; Measures against erosion or corrosion
• CPC Class Codes: F01D 5/288 Protective coatings for blades
• CPC Class Codes: F05D 2230/21 by casting
• CPC Class Codes: F05D 2230/90 Coating; Surface treatment
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft

Abstract

An alloy casting having a protective layer disposed on a surface of the casting is provided. The protective layer is resistant to liquid metal attack, and wherein the protective layer includes an oxide of an element present in the alloy. A method of forming a protective layer on a surface of the alloy casting is also provided. The method includes disposing the alloy in a mold, and oxidizing an element of the alloy to form a protective layer on the surface of the casting.

Claims

1. An alloy casting comprising a protective layer disposed on a surface of the casting, wherein the protective layer is resistant to liquid metal attack, and wherein the protective layer comprises an oxide of an element present in the alloy.

2. The alloy casting of claim 1, wherein the alloy comprises nickel, or cobalt, or titanium, or iron, or combinations thereof.

3. The alloy casting of claim 1, wherein the alloy comprises aluminum.

4. The alloy casting of claim 1, wherein the oxide comprises aluminum oxide.

5. The alloy casting of claim 1, wherein the protective layer is substantially continuous throughout the surface of the casting.

6. The alloy casting of claim 1, wherein a thickness of the protective layer is in a range from about 0.5 microns to about 50 microns.

7. The alloy casting of claim 1, wherein the casting is employed in an airfoil of a gas turbine engine.

8. A casting of a nickel-based alloy comprising a continuous native oxide layer disposed on a surface of the casting, wherein the native oxide layer is resistant to liquid metal attack.

9. A method of forming a protective layer on a surface of a casting of an alloy, comprising:

disposing the alloy in a mold; and

oxidizing an element of the alloy to form a protective layer on the surface of the casting.

10. The method of claim 9, wherein the mold comprises an inner coating that is reactive to at least one element of the alloy and relatively less reactive or inert to the others.

11. The method of claim 9, wherein the inner coating of the mold comprises chromia, niobia, titania, tantala, silica, zircon, yttria, or combinations thereof.

12. The method of claim 9, wherein at least a portion of the protective layer is coupled to the surface of the casting.

13. The method of claim 9, wherein oxidizing comprises:

reacting at least one material from the inner coating of the mold with aluminum present in the alloy.

14. The method of claim 9, wherein oxidizing comprises:

exposing the alloy or the casting to an oxidizing atmosphere to facilitate oxidation of aluminum metal present in the alloy.

15. The method of claim 14, wherein the oxidizing atmosphere comprises an oxygen source diluted by an inert carrier.

16. The method of claim 15, wherein the oxygen source comprises carbon monoxide, oxygen, carbon dioxide, moisture, or combinations thereof.

17. The method of claim 15, wherein the inert carrier comprises argon.

18. The method of claim 15, wherein the oxidizing atmosphere comprises oxygen source in a range of about 2 percent to about 20 percent of the total amount of a mixture of the oxygen source and the inert carrier.

19. The method of claim 15, wherein the oxygen source comprises about 10 percent carbon monoxide and about 90 percent argon.

20. The method of claim 9, wherein a thickness of the protective layer is in a range from about 0.5 microns to about 50 microns.

21. The method of claim 9, wherein the mold comprises zirconia, zircon, silica, alumina, or combinations thereof.

22. The method of claim 9, wherein at least a portion of the protective layer is formed simultaneously with a casting of the alloy.

23. The method of claim 9, wherein at least a portion of the protective layer is not coupled to a surface of the mold.

24. A method of forming an aluminum oxide layer on a casting, comprising:

providing a mold having a coating disposed on an inner surface of the mold; and

disposing an alloy in the mold, wherein at least a portion of the aluminum in the alloy reduces a portion of constituents in the coating to form aluminum oxide.

25. A method of forming an aluminum oxide layer on a casting, comprising:

providing a mold;

disposing an alloy in the mold to form the casting; and

providing an oxidizing atmosphere in the mold to oxidize at least a portion of aluminum present in the alloy.