An Evaluation of Mechanical Properties and Microstructure of Nitinol by Friction Welding

Abstract

In this research paper, the study of friction weldin g is being performed on the superelastic Nitinol ba r. Nickel Titanium alloy is also known as Nitinol (Ni 56Ti44) of 8mm diameter, 50 mm in length on one side and 80mm in length on other side was used as experimental material. Ni tinol was joined by using direct drive rotary fricti on welding machine with 6 tons capacity with fully automated mod e was used in joining process. Tensile strength of friction welded 8mm diameter NITINOL joints were investigated consid ering various process parameters: friction force (F) , upset force (U), burn off length and Spindle speed (N). Direct and interaction effects of process parameters on re sponses were studied by plotting graphs. Micro structural study of base Nitinol and friction welded Nitinol was exami ned. The results of tensile tests on the processed welded Nitinol ind icated a slight increase in strength in the process d regions; likely because of grain size refinement and no decrease in ductility compared to the parent Nitinol material. This research has shown that in term of hardness, the weld metal has th e highest hardness followed by HAZ and base metal.