Electrochemical micromachining of actuator-grade Nitinol shape memory alloy with and without laser assistance

Abstract

The growing demand of Nitinol shape memory alloys (SMAs) in medical and actuator applications has necessitated research in developing micromachining technologies which do not induce mechanical or thermal load induced microstructural transformations in the alloy. This work presents electrochemical micromachining as a potential technology for machining Nitinol SMAs without deteriorating their functional property. A further hybridization of ECM with a ns pulsed laser has been presented to enhance machining in terms of uniform dissolution of surface and processing speed. Insights into dissolution mechanisms have been presented. The results indicate successful machining of Nitinol SMAs with electrochemical machining with added benefits using laser assistance. The shape memory property (transformation temperatures) is not largely affected post-machining. The Differential Scale Calorimetry (DSC) results show only slight variations (±3 °C) of the transformation peaks, but there is no correlation between peak shifts and process energies (electrochemical and laser). Post-machining, the material remains well-suited for thermal cycling in an actuator application.