Evaluation of an induction-assisted friction stir welding technique for super duplex stainless steels

The microstructure changes and the mechanical properties of a friction stir welded (FSW) super duplex stainless steel (GX2CrNiMoN26-7-4) were analyzed. A PCBN tool was used to weld 5-mm-thick plates at a constant rotational speed of 300 rpm, at 100 and 200 mm/min, under two different conditions: conventional FSW and Induction-Assisted FSW (IA-FSW). Preheating technique allows welding with a reduction in forge forces close to 31% at the same welding speed, or doubling speed (200 mm/min) at the same axial force, obtaining sound welds. No sigma phase was detected in the welds, and the clear grain size reduction led to an increase in mean hardness value and the tensile strength of the stir zone. Ferrite percentage was found to be between 50 and 70% through the welds. Copyright (C) 2014 John Wiley & Sons, Ltd.