Welding of gamma'-strengthened superalloys
A method of welding γ′-strengthened superalloys. The methods improve the weldability of these superalloys by creating areas having lower amounts of γ′-forming elements, resulting in stronger welds. In one method, a vacuum heat treatment is used to create γ′-depleted zones having reduced amounts of γ′-forming elements. A post weld heat treatment may then be used. In another method, a γ-stabilizing element, such as Cr or Ni, is deposited on the area to be welded. Again, a post weld heat treatment may then be used.
1 . A method for welding γ′-strengthened superalloys comprising:
pre-treating at least one area of the superalloy to be welded to reduce the formation of γ′ materials during a welding process; and
welding the superalloy in the at least one area to be welded.
2 . The method of claim 1 , wherein the superalloy is pre-treated to remove a portion of γ′-forming elements from the at least one area to be welded.
3 . The method of claim 2 , wherein at least about 10 mole % of the γ′-forming elements are removed from the at least one area to be welded.
4 . The method of claim 3 , wherein at least about 20 mole % of the γ′-forming elements are removed from the at least one area to be welded.
5 . The method of claim 2 , wherein the removal of γ′-forming elements from the at least one area to be welded is accomplished using a vacuum heat treatment step.
6 . The method of claim 5 , wherein the vacuum heat treatment step is performed at a pressure of less than about 1E-4 barr.
7 . The method of claim 2 , wherein the removal of γ′-forming elements from the at least one area to be welded is accomplished using a chemical stripping process.
8 . The method of claim 7 , wherein the chemical process is immersion in an acid bath.
9 . The method of claim 7 , wherein the chemical process is electroetching.
10 . The method of claim 7 , wherein the chemical process is vapor cleaning.
11 . The method of claim 2 , wherein the superalloy has an original γ/γ′ ratio and wherein the method further comprises the step of using a heat treatment step to restore to substantially the original γ/γ′ ratio after the superalloy has been welded.
12 . The method of claim 2 , wherein the γ′-forming elements are selected from aluminum, titanium, or a combination thereof.
13 . The method of claim 2 , wherein a fusion welding process is used to weld the superalloy in the at least one area to be welded.
14 . The method of claim 1 , wherein a γ-stabilizing element is added to the at least one area to be welded.
15 . The method of claim 14 , wherein the γ-stabilizing element is added using a deposition process, a plating process, a coating process, or a combination thereof.
16 . The method of claim 14 , wherein the γ-stabilizing element is selected from nickel, chromium, or a combination thereof.
17 . The method of claim 14 , wherein the superalloy has an original γ/γ′ ratio and wherein the method further comprises the step of using a heat treatment step to restore the original γ/γ′ ratio after the superalloy has been welded.
18 . The method of claim 14 , wherein a low heat input welding process is used to weld the superalloy in the at least one area to be welded.