Development of a High Toughness Weld for Incoloy Alloy 908
Incoloy® alloy 908+ is a candidate conduit material for the large-scale Nb3Sn superconducting magnets of the International Thermonuclear Experimental Reactor (ITER).1 It is a nickel-iron base precipitation-hardening superalloy with a chemical composition that has been optimized for a low coefficient of thermal expansion, superior cryogenic structural properties, and phase stability during the Nb3Sn reaction heat treatment.2 The alloy precipitates γ′, Ni3(A1,Ti,Nb), as the primary strengthening phase and has demonstrated excellent mechanical properties at both 298 and 4 K.3,4 However, welds of the alloy have shown reduced fracture toughness. Since fabrication of the cablein-conduit conductors for ITER will require welding, the motive of the work has been to improve fracture toughness while maintaining adequate weld strength.
KeywordsFracture Toughness Ultimate Tensile Strength Filler Metal Postweld Heat Treatment Fatigue Crack Growth Rate
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