Apparatus and method for bonding refractory metals

1. A clamping arrangement for use in compressing together two articles so that a welded bond can be formed between the two articles, said two articles formed of refractory metal alloy, said clamping arrangement including a first clamp that is at least partially formed of a tungsten material, said first clamp designed to releasably secure a portion of one of said articles to be bonded and to release from said article after said bond is formed between said two articles, said tungsten material includes a majority weight percent tungsten and at least one additive selected from the group consisting of rhenium, hafnium carbide, an oxide of thorium, an oxide of lanthanum, and mixtures thereof.

2. The clamping arrangement as defined in claim 1 , wherein at least a portion of an outer surface of said first clamp includes a metal oxide coating that is designed to contact said article, said metal oxide coating including one or more oxides selected from the group consisting of an oxide of titanium, an oxide of zirconium and an oxide of hafnium.

3. The clamping arrangement as defined in claim 2 , wherein said metal oxide coating has a thickness of at least about 10 microns.

4. The clamping arrangement as defined in claim 3 , including a second clamp, said second clamp designed to releasably secure a portion of one of said articles to be bonded and to release from said article after said bond is formed between said two articles, said second clamp formed of the same composition as said first clamp.

5. The clamping arrangement as defined in claim 4 , wherein at least a portion of an outer surface of said second clamp includes a metal oxide coating that is designed to contact said article, said metal oxide coating including one or more oxides selected from the group consisting of an oxide of titanium, an oxide of zirconium and an oxide of hafnium.

6. The clamping arrangement as defined in claim 5 , wherein said tungsten material includes at least 95 weight percent tungsten and one or more additives selected from the group consisting of at least about 0.5 weight percent of an oxide of thorium, at least about 0.5 weight percent of an oxide of lanthanum, and at least about 0.5 weight percent hafnium carbide.

7. The clamping arrangement as defined in claim 6 , wherein one or more of said additives is selected from the group consisting of about 0.5-2.5 weight percent of an oxide of thorium, about 0.5-2.5 weight percent of an oxide of lanthanum and about 0.5-2 weight percent of an oxide of thorium.

8. The clamping arrangement as defined in claim 5 , wherein said tungsten material includes at least about 10 weight percent rhenium.

9. The clamping arrangement as defined in claim 8 , wherein said tungsten material includes about 15-27.5 weight percent rhenium.

10. The clamping arrangement as defined in claim 1 , including a second clamp, said second clamp designed to releasably secure a portion of one of said articles to be bonded and to release from said article after said bond is formed between said two articles, said second clamp formed of the same composition as said first clamp.

11. The clamping arrangement as defined in claim 10 , wherein at least a portion of an outer surface of said second clamp includes a metal oxide coating that is designed to contact said article, said metal oxide coating including one or more oxides selected from the group consisting of an oxide of titanium, an oxide of zirconium and an oxide of hafnium.

12. The clamping arrangement as defined in claim 1 , wherein said tungsten material includes at least 95 weight percent tungsten and one or more additives selected from the group consisting of at least about 0.5 weight percent of an oxide of thorium, at least about 0.5 weight percent of an oxide of lanthanum, and at least about 0.5 weight percent hafnium carbide.

13. The clamping arrangement as defined in claim 12 , wherein one or more of said additives is selected from the group consisting of about 0.5-2.5 weight percent of an oxide of thorium, about 0.5-2.5 weight percent of an oxide of lanthanum and about 0.5-2 weight percent of an oxide of thorium.

14. The clamping arrangement as defined in claim 1 , wherein said tungsten material includes at least about 10 weight percent rhenium.

15. The clamping arrangement as defined in claim 14 , wherein said tungsten material includes about 15-27.5 weight percent rhenium.

16. A method for forming a bond between first and second articles, said two articles formed of refractory metal alloy, said method comprising:

a) providing a first clamp, said first clamp including a clamping region designed to releasably secure a portion of said first article, said clamping region at least partially formed of a tungsten material, said tungsten material includes a majority weight percent tungsten and one or more additives selected from the group consisting of rhenium, hafnium carbide, an oxide of thorium and an oxide of lanthanum;

b) releasably securing said first article by said clamping region of said first clamp;

c) positioning a portion of said first article into contact with a portion of said second article;

d) applying heat at or near a region wherein said first and second articles are in contact until a bond is formed between said first and second articles; and,

e) releasing said first article from said clamping region of said first clamp.

17. The method as defined in claim 16 , including a second clamp, said second clamp including a clamping region designed to releasably secure a portion of said second article, said clamping region of said second clamp at least partially formed of a tungsten material, said tungsten material includes a majority weight percent tungsten and at least one additive selected from the group consisting of rhenium, an oxide of thorium, an oxide of lanthanum, and mixtures thereof.

18. The method as defined in claim 17 , including the step of pressing said first and second articles together by at least one of said clamp during said step of applying heat.

19. The method as defined in claim 18 , wherein said bond between said first and second articles is formed by a controlled bonding temperature and a controlled bonding pressure, a selection of said controlled bonding temperature and said controlled bonding pressure is at least partially based on a relationship of Y=c−mX, wherein Y is a ratio of said bonding pressure to an ultimate tensile strength of said first and second articles at a temperature of 60% of a melting temperature of said first and second articles, X is a ratio of said bonding temperature to said melting temperature of said first and second articles, c is about 1 to 1.4, and m is about 1 to 1.4.

20. The clamping arrangement as defined in claim 19 , wherein at least a portion of an outer surface of said first clamp includes a metal oxide coating that is designed to contact said article, said metal oxide coating including one or more oxides selected from the group consisting of an oxide of titanium, an oxide of zirconium and an oxide of hafnium.

21. The clamping arrangement as defined in claim 20 , wherein said tungsten material includes at least 95 weight percent tungsten and one or more additives selected from the group consisting of at least about 0.5 weight percent of an oxide of thorium, at least about 0.5 weight percent of an oxide of lanthanum, and at least about 0.5 weight percent hafnium carbide.

22. The clamping arrangement as defined in claim 20 , wherein said tungsten material includes at least about 10 weight percent rhenium.

23. The method as defined in claim 16 , including the step of pressing said first and second articles together by at least one of said clamp during said step of applying heat.

24. The method as defined in claim 16 , wherein said bond between said first and second articles is formed by a controlled bonding temperature and a controlled bonding pressure, a selection of said controlled bonding temperature and said controlled bonding pressure is at least partially based on a relationship of Y=c−mX, wherein Y is a ratio of said bonding pressure to an ultimate tensile strength of said first and second articles at a temperature of 60% of a melting temperature of said first and second articles, X is a ratio of said bonding temperature to said melting temperature of said first and second articles, c is about 1 to 1.4, and m is about 1 to 1.4.

25. The clamping arrangement as defined in claim 16 , wherein at least a portion of an outer surface of said first clamp includes a metal oxide coating that is designed to contact said article, said metal oxide coating including one or more oxides selected from the group consisting of an oxide of titanium, an oxide of zirconium and an oxide of hafnium.

26. The clamping arrangement as defined in claim 16 , wherein said tungsten material includes at least 95 weight percent tungsten and one or more additives selected from the group consisting of at least about 0.5 weight percent of an oxide of thorium, at least about 0.5 weight percent of an oxide of lanthanum, and at least about 0.5 weight percent hafnium carbide.

27. The clamping arrangement as defined in claim 16 , wherein said tungsten material includes at least about 10 weight percent rhenium.

28. The method as defined in claim 16 , including the step of forming an inert atmosphere at least partially at or near a region wherein said first and second articles are in contact during said step of applying heat.

29. The method as defined in claim 16 , wherein said step of applying heat includes the use of a laser or electron beam.