Cyclic overageing heat treatment for ductility and weldability improvement of nickel-based superalloys
AssigneeNational University of Singapore
InventorLeong-Chew Lim
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Abstract
The present invention is directed to a pre-weld overageing heat treatment for nickel-based superalloys, where the alloy is heated to solutionization temperature for a time sufficient to dissolve the gamma prime phase of the alloy microstructure, then slowly cooled with periods of intermittent heating, so that the gamma prime phase reprecipitates as coarse equiaxed particles, and the presence of fine sized gamma prime phase particles is substantially avoided. The present invention is also directed to a welding method wherein said pre-weld overageing treatment is used.
Claims16
A pre-weld overageing heat treatment for nickel-based superalloys, comprising:
- (a) heating a nickel-based superalloy to solutionization temperature for a period of time sufficient to dissolve a strengthening gamma prime phase of the microstructure of said nickel-based superalloy to produce a heated nickel-based superalloy;
- (b) cooling said heated nickel-based superalloy at a rate of cooling that is slow enough to allow reprecipitation of said gamma prime phase as coarse particles;
- and
- (c) interrupting said cooling with intermittent heating cycles that cause at least a partial dissolution of gamma prime phase formed during the cooling, wherein said intermittent heating is at a rate or rates, and for a duration or durations, sufficient to obtain predominantly coarse equiaxed gamma prime precipitates in said microstructure.
Dependencies are inferred from the claim text.