Precipitation of delta phase during solid-state diffusion bonding of Inconel alloy 718 to itself was studied in the present investigation. The joining was carried out from 910 to 1060 C deg, in steps of 30 C deg, with time and pressure fixed at 60 min and 32MPa, respectively. In the joint bonded at 910 C deg, transforming of gamma to delta was observed. Delta phases had two kinds of morphology: platelet-like in the bond line area and needle-like in the bulk material. In both shapes, delta appeared intergranular and intragranular. Widmanstätten structure was formed. For a joint bonded at 940 C deg, only platelet delta phases precipitated, both intergranularly and intragranularly. No Widmanstätten structure was observed. When bonding temperature was increased beyond 970 C deg, delta phase was not observed in the as-bonded joints. To avoid the transformation of gamma to delta, the bonding temperature should be higher than the solvus of gamma. Higher cooling rate was also found helpful in this regard, and a cooling rate faster than 5 C deg/min seemed adequate in suppressing delta precipitation.
Effect of bonding temperature on the precipitation of delta phase in diffusion bonded Inconel 718 joints
Materials and Manufacturing Processes ; 21 , 5/6 ; 452-456
2006
5 Seiten, 7 Bilder, 2 Tabellen, 13 Quellen
Article (Journal)
English
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