Characterization of Laser-Welded Nitinol

Abstract. With the increasing complexity of blood vessel-implants, heart valve frames and delivery systems for minimally invasive surgical interventions the importance of joining technologies experiences a steady growth. Due to low heat input, touchless processing and miniaturization, the laser welding for joining Nitinol has established itself as the method of choice.

The present study deals with a closer examination of the laser welding process of nitinol and the characterization of the properties of laser welded nitinol. At first, the welding process is simulated and examined by Computational Fluid Dynamics (CFD) analysis. The resulting structure and composition of the welded microstructure is determined using physical samples which are investigated by appropriate microstructural characterization methods and compared to the simulation results.

Furthermore, the properties of the weld seams, like mechanical stability or corrosion resistance, that are crucial for the complete assembly, are characterized. Also part of the study is to consider the impact of the initial state of the base material as well as subsequent treatment steps.

The results of the study are included in a Finite Element Analysis (FEA) which can be used to design the joints.