TWI

Dissimilar lap joints between ASTM A36 low carbon steel and Inconel 625 (Ni, 21.4%Cr, 9.65%Mo, 3.2%Nb, 2.6%Fe) were fabricated by friction stir welding (FSW) and the effects of process parameters on microstructure and hardness were investigated. FSW was performed in position control mode using a composite 40% matrix, 60% polycrystalline cubic BN reinforced tool at a constant welding speed of 100 mm/min, tool rotational speed of 300-400 rpm and plunge depth of 5.65 or 5.7 mm. Weld microstructure was observed by optical microscopy and SEM coupled with energy dispersive X-ray spectroscopy and electron backscattered diffraction. Vickers hardness was evaluated on weld cross-sections by microindentation tests. Issues discussed include ferrite and austenite grain refinement in HAZ and stir zone regions as well as intermetallic phase formation at the dissimilar metal interface.

9th International Symposium, 15-17 May 2012, Session 8A: Nickel Alloys, Paper 03