Microstructure and mechanical properties of NiTi-SS bimetallic structures built using Wire Arc Additive Manufacturing

Abstract

Dissimilar joining of Nickel-titanium (NiTi) alloy with other metallic alloys can be used to widen the applications of NiTi for developing artificial bones and joints, guidewires, and stents. This paper presents the microstructure and mechanical properties of Wire Arc Additive Manufactured NiTi-SS bimetallic structures for the first time. Defect-free deposit with a smooth transition in the composition across the joint is observed. NiTi shows a dendritic microstructure and TiCr2, TiNi3 and FeNi intermetallic phases are observed at the interface that imparts reasonable mechanical properties. The interface showed an average hardnes of 400 HV and the ultimate compressive strength is observed to be 570 MPa, with brittle fracture due to the presence of brittle intermetallics.