Laser Welding of Nickel Titanium and 304 Stainless Steel Tubes Available to Purchase

Shape memory nickel-titanium (NiTi) can generate large blocking stresses and high recovery strains, up to 8%, which make NiTi a good candidate for solid state actuators, resulting in substantial weight and space savings when they replace traditional electric or hydraulic systems. A challenge surrounding NiTi based actuators is integration of the NiTi components into a given system; this alloy is difficult and expensive to machine and weld to itself and structural materials. In this research, we join NiTi and 304 stainless steel tubes 9.52 mm (0.375 in) in diameter through laser welding to create joints with weld depths up to 1650 μm (0.065 in). By joining NiTi to a common structural material that is easily machined and readily welded to other materials, the challenges surrounding system integration are reduced. The joints prepared in this study were characterized through optical microscopy, hardness mapping, and mechanical testing. The average ultimate shear strength of these joints is 423 MPa (61.3 ksi) and the resulting HAZ has a maximum width of 21.9 μm with a maximum hardness of 929 HV.