Effects of surface laser treatments on microstructure, tension, and fatigue behavior of AISI 316LVM biomedical wires

Recent developments in minimally invasive surgical techniques have led to a surge in advancing alternative manufacturing routes. In order to meet the functional needs of such small devices as cardiovascular stents, and guide wires, the use of new materials and delicate geometries has increased creating a new challenge for manufacturing and machining. In this work, two sets of laser parameters leading to different laser power output were employed to study the effects of systematic changes in microstructure and mechanical characteristics of AISI 316LVM biomedical grade wires. Uniaxial tension and cyclic strain-controlled fatigue with the use of flex bending machines were used in order to evaluate the mechanical properties. Surface quality, heat affected zone (HAZ), and subsequent mechanical response were also investigated. Improvements in the fatigue behavior of laser-treated wires were obtained but depended on the choice of laser parameters. Low power Nd:YAG laser treated AISI 316LVM annealed wires exhibited better fatigue performance in both high cycle fatigue and low cycle fatigue compared to the annealed AISI 316LVM wires. In contrast, high power Nd:YAG laser-treated annealed wires exhibited poorer fatigue performance in both high cycle and low cycle fatigue. Nd:YAG laser-treated AISI 316LVM hard wires exhibited poorer fatigue performance in both high cycle fatigue and low cycle fatigue compared to the AISI 316LVM hard wires. The effects of laser processing conditions on the microstructural features responsible for these changes in fatigue behavior are discussed.