Surface Characterization and Optimization of Electropolishing Parameters for a Near Equiatomic Binary NiTi Alloy
摘要
Electropolishing is a critical surface finishing process for NiTi alloys, particularly in biomedical applications where surface smoothness, corrosion resistance, and biocompatibility are essential. This study investigates the effect of electropolishing parameters, including electrolyte concentration, voltage, and processing time, on the surface characteristics of NiTi alloys. A series of nine experiments were conducted using varying electropolishing conditions, and the resulting surfaces were analyzed using optical microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive spectroscopy (EDS). The results showed that electropolishing significantly reduced surface roughness, with the smoothest surface (Ra = 34 nm) obtained at an electrolyte concentration of 12.5% H2SO4, 20 V voltage, and 2 min processing time. Higher voltages and longer processing durations led to the formation of pits and surface roughness due to excessive material dissolution. SEM and EDS analysis confirmed the formation of TiC/TiO2 layers, which can enhance corrosion resistance and biocompatibility of the Nitinol. AFM studies validated the presence of martensitic structures, confirming that electropolishing did not alter the microstructure of the NiTi alloy.