Electric heating – Metal heating – By arc
Reexamination Certificate
2000-03-17
2001-12-25
Heinrich, Samuel M. (Department: 1725)
Electric heating
Metal heating
By arc
C219S076100, C228S231000, C228S232000, C228S262300
Reexamination Certificate
active
06333484
ABSTRACT:
The present invention relates to a process for welding superalloy articles which are difficult to weld.
As jet engine components are developed there is a continuing demand for improved capability to withstand increasingly higher temperatures due to the high temperature demands placed upon these components in the engine. Today's high pressure turbine blades and vanes are subjected to extremely adverse high temperature conditions (e.g. greater than 2000° F.). These jet engine parts may require welding processes during the manufacture of the components, or after seeing engine operations and require repair as a result of wear and cracking.
As a result of these high temperature demands these components often are manufactured from superalloys containing a gamma-prime phase. One particular problem with the gamma-prime precipitation hardenable alloys such as R′80 is the inability to weld or clad these alloys with like or similar alloys without encountering cracking and high production rejects.
Because of the welding temperatures and stresses involved, these alloys encounter shrinkage, stress cracking and the like. Due to the difficulties in welding these specific superalloys, there is a need for a process by which gamma-prime precipitation hardened alloys can be welded consistently without cracking with similar or parent metal alloys. U.S. Pat. Nos. 5,106,010 and 5,374,319 disclose such a process which preheats the weld area and region adjacent to the weld area to a ductile temperature and maintains such temperature during welding and solidification. U.S. Pat. No. 5,554,837 discloses carrying out an interactive laser welding process to maximize reproduceability and minimize rejects and waste while increasing throughput of welded components. While these processes minimize cracking in many alloys, there is still a need for improvements in the process.
SUMMARY OF THE INVENTION
Briefly, this invention provides a process for welding a nickel and/or cobalt based superalloy article, comprising preheating the entire weld area and region adjacent to the weld area of the article to a maximum ductility temperature range and maintaining such temperature during welding and solidification of the weld; and raising the temperature of the welded article to a stress relieving temperature, followed by cooling the welded article, preferably cooling at a rate of at least 100° F. (55° C.) per minute, to below the gamma prime precipitation hardening range to minimize gamma prime precipitation.
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“Evaluation of the Weldability of the Gas Turbine Blade Materials In738LC and Rene 80” by N. Czech et al., Proceedings from Materials Solutions '97 on Joining and Repair of Gas Turbine Components, Sep. 15-18, 1997, pp. 7-10.
Foster Michael
Updegrove Kevin
Bittman Mitchell D.
Chromalloy Gas Turbine Corporation
Heinrich Samuel M.
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