Low Distortion Repair of Thin Superalloy Components

Nickel-base superalloys, upon fusion welding, could be prone to solidification cracking, Heat Affected Zone (HAZ) liquation cracking, strain age cracking, segregation of alloying elements and the formation of porosity in the weld zone (Ref. 18). Solid-state Friction-Stir welding can also result in HAZ cracking, and strain age cracking. Additionally, repair welding thin-rolled sheet involves thickness profile restoration, stress-relief anneal and shape restoration making it an expensive operation with difficult logistics. The object of this proposal is to develop largely solid-state deformation resistance/resistance-seam weld methods using filler sheets of the same chemistry as the metals repaired. HAZ areas will be cooled using water-cooled copper alloy weld electrode extensions during welding. Largely solid-state weld microstructures will be generated as detailed in the Technical Section, without solidification defects such as solidification cracking, weld porosity, alloying element segregation. Cooling HAZ areas with water-cooled copper tooling enables counteracting defects such as HAZ liquation cracking. Thickness profile restoration is proposed using an elegantly simple technique, while shape restoration and stress-relief anneal are proposed to be done in the weld machine itself with different tooling and process parameters impacting costs and logistics favorably. The homogeneous chemistry at the weld bead should help increase mean-time-between-failures.