Microstructure and Mechanical Properties of Rotary Friction Welded IN-600 and SS316L with Copper Interlayer

The ability to weld Inconel with stainless steel would enable design simplification for various high-temperature applications. Fusion welding and plastic deformation-based solid-state joining techniques lead to intermetallics and significant deformation zones, leading to inferior joint performance. In this work, rotary friction welds of In-600 and SS316L are performed with and without Cu interlayer, at 3000 rpm, 10 mm/min of friction feed rate, and 60 mm/min forging feed rate. Near the joint interface, dynamic recrystallization driven grain refinement on steel side and grain coarsening on Inconel side are noticed. Tensile testing results show that the joint strength and ductility of the joints with Cu interlayer are appreciably higher than the same for the joints made without interlayer. For the joints with Cu interlayer, fractography indicates ductile fracture and EDS analysis of the fracture surface suggests uniform spreading of copper at the steel side, which would impede the formation of brittle Fe-Ni intermetallics. For joints without Cu interlayer, cleavage marks are noticed on the steel side fracture surface, with significant presence of Ni indicating Fe-Ni intermetallics, which would promote brittle fracture. The joint efficiency of the joints made with Cu interlayer is 97.5% with 25.7% elongation, which also compares decently against the same for the base material (33% for Inconel 600).