Machinability and surface integrity of Nitinol shape memory alloy

Nitinol shape memory alloys have wide applications in medical devices and actuators. However, the unique mechanical properties including superelasticity, high ductility, and severe strain-hardening make Nitinol exceedingly difficult to cut. This work determines dynamic mechanical behaviors of Nitinol in cutting. It is found that the very high strength and specific heat are responsible for large flank wear and fast tribo-chemical crater wear, respectively. The austenitic white layer in cutting is caused by deformation, while the twinned martensitic white layer is caused by quenching in EDM. Alloying from tools is negligible in cutting but unavoidable even in finish EDM trim cut.