Evaluation of 3D surface roughness in electrochemical micromachining of Nitinol

Abstract

Equiatomic nickel-titanium (NiTi) composed of Nickel and Titanium (i.e. 50:50% of Ni and Ti) or Nitinol, an expensive, very smart shape memory alloy material of choice for biomedical applications because of its bio compatibility. Machining Nitinol is challenging by means of non- traditional techniques. Experiments are carried out to produce a precise geometrical micro hole in Shape memory alloy Nitinol, using Electrochemical Micromachining (Abbreviated as ECMM). In ECMM process, micro holes are produced with 500 μm tool electrode in a shape memory alloy (SMA)—Nitinol of 0.25 mm thickness using the Non-passivating electrolyte (NPE), Passivating electrolyte (PE) and the Composite electrolyte (CPE) to study the machining characteristics. A tedious effort is made to produce such a micro hole using a noval mixed electrolyte to improve machining process. Polarization studies are also carried out for all the chosen electrolytes. The process is clearly analyzed thoroughly with the help of polarization and SEM. Expected results with good precision and surface characteristics are obtained when the nitinol is machined with the composite electrolyte. The results proved that the compatibility of machining nitinol is composite type of electrolyte. Composite electrolyte provides the combined advantages of both the passivated and non-passivated electrolytes. This study resulted in finding the suitable and optimized parameters for machining Nitinol with PE, NPE and CPE with better precision and good surface integrity.