Friction stir weld tools having fine grain structure

Patent metadata

Field	Value
Publication number	US-9283637-B2
Application number	US-201313747236-A
Country	US
Kind code	B2
Filing date	Jan 22, 2013
Priority date	Feb 5, 2010
Publication date	Mar 15, 2016
Grant date	Mar 15, 2016

Abstract

Tools for friction stir welding can be made with fewer process steps, lower cost techniques, and/or lower cost ingredients than other state-of-the-art processes by utilizing improved compositions and processes of fabrication. Furthermore, the tools resulting from the improved compositions and processes of fabrication can exhibit better distribution and homogeneity of chemical constituents, greater strength, and/or increased durability. In one example, a friction stir weld tool includes tungsten and rhenium and is characterized by carbide and oxide dispersoids, by carbide particulates, and by grains that comprise a solid solution of the tungsten and rhenium. The grains do not exceed 10 micrometers in diameter.

First claim

We claim:

1. A friction stir weld tool comprising tungsten and rhenium, the tool further comprising carbide and oxide dispersoids, carrbide particulates, and grains not exceeding 10 micrometers in diameter, wherein the grains comprise a solid solution of the tungsten and rhenium.

2. The friction stir weld tool of claim 1 having substantially no nickel.

3. The friction stir weld tool of claim 1 , wherein the rhenium is less than or equal to 20 wt % of the tool.

4. The friction stir weld tool of claim 1 , wherein the rhenium is less than or equal to 10 wt % of the tool.

5. The friction stir weld tool of claim 1 , wherein the rhenium is less than or equal to 6 wt % of the tool.

6. The friction stir weld tool of claim 5 , wherein the tool has a hardness of at least 450 H V at room temperature.

7. The friction stir weld tool of claim 1 , wherein the grains have a diameter between 100 nm and 1 micrometer.

8. The friction stir weld tool of claim 1 , wherein the dispersoids are located in the grains, on the grains, or both.

9. The friction stir weld tool of claim 1 having both hafnium carbide and cerium oxide as carbide and oxide dispersoids, respectively.

10. The friction stir weld tool of claim 1 , wherein the carbide particulates comprise hafnium carbide.

11. The friction stir weld tool of claim 1 , having a uniform distribution of carbide particulates in the tool, wherein the volume fraction of carbide particulate in any 50 cubic micrometer volume of the tool falls within 1 standard deviation of the mean volume fraction of carbide particulate in any 500 cubic micrometer volume of a dense solid provided, the carbide particulate is 1 to 5 micron in size.

12. The friction stir weld tool of claim 1 , having substantially equiaxed grains and an even size distribution of grains, wherein 80% of the grains are within 1 standard deviation of a mean grain size in any 500 cubic micron volume of the tool.

13. A friction stir weld tool comprising tungsten, the tool further comprising carbide and oxide dispersoids and grains having diameters between 100 nm and 10 micrometers, wherein the grains comprise tungsten and substantially no rhenium.

14. A method of fabricating a friction stir weld tool comprising tungsten and rhenium, the method comprising the steps of:
Providing a nanopowder comprising crystallites having an average crystallite diameter between 20 and 60 nanometers and comprising tungsten;
Comminuting a mixture comprising the nanopowder, particulates comprising a carbide compound, and an oxide material;
Compacting the mixture; and
Sintering the mixture at a temperature and for a time such that the tool has grains not exceeding 10 micrometers in diameter; and
Forming carbide and oxide dispersoids in the tool from at least a portion of the carbide compound and the oxide material, respectively.

15. The method of claim 14 , wherein the crystallites comprise tungsten and rhenium in a solid solution.

16. The method of claim 14 , wherein the carbide compound comprises hafnium carbide.

17. The method of claim 14 , wherein the oxide material comprises cerium oxide.

18. The method of claim 14 , wherein the oxide material is contained in a sol.

19. The method of claim 14 , wherein said comminuting step comprises milling the mixture in water.

20. The method of claim 14 , wherein the temperature is less than or equal to 1600° C.

21. The method of claim 14 , wherein the time is less than or equal to 5 hours.

22. The method of claim 14 , wherein the time is less than or equal to 2 hours.

23. A method of fabricating a friction stir weld tool comprising tungsten and rhenium, the method comprising the steps of:
Synthesizing a nanopowder from an aqueous solution comprising tungsten and rhenium precursors, crystallites of the nanopowder having an average diameter between 20 and 60 nanometers and comprising a solid solution of tungsten and less than 10 wt % rhenium;
Comminuting a mixture comprising water, the nanopowders, hafnium carbide particulates, and a sol comprising cerium oxide;
Compacting the mixture; and
Sintering the mixture at a temperature less than or equal to 1600° C. for a time less than or equal to 5 hours such that the tool has grains not exceeding 10 micrometers in diameter, and such that hafnium carbide and cerium oxide dispersoids form in the tool from at least a portion of the hafnium carbide particulates and the cerium oxide, respectively.

24. The method of claim 23 , wherein said synthesizing further comprises forming tungsten carbide dispersoids from excess carbon in the aqueous solution, the tungsten carbide dispersoids located in, or on, the crystallites.

Assignees

• Battelle Memorial Institute

Inventors

• Grant Glenn J
• Frye John G
• Kim Jin Yong
• Lavender Curt A
• Weil Kenneth Scott

Classifications

• C22C1/053

  with in situ formation of hard compounds · CPC title

• B22F9/24 Primary

  starting from liquid metal compounds, e.g. solutions · CPC title

• C01G41/02

  Oxides; Hydroxides · CPC title

• C22C1/045

  Alloys based on refractory metals · CPC title

• C22C1/058

  Chemistry & Metallurgy · mapped topic