Study of corrosion resistance property and microstructure of TiNi shape memory alloy modified by pulsed high-energy density plasma

The corrosion resistance of TiNi (Ti-50 at.% Ni) shape memory alloy is improved by about one order of magnitude after the surface is modified by pulsed high-energy density plasma (PHEDP) composed of titanium and nitrogen. The corrosion resistance property was measured by potentiodynamic polarization and electrochemical impedance methods in 2% sodium chloride (NaCl) and 0.5 mol l(-1) H2SO4 solutions. The microstructure of the film is examined by transmission electron microscopy (TEM), which showed that the film is composed of TiN and Ti2N phases. In the PHEDP surface modification, the effects of ion implanting combined with melting and rapid quenching contribute to the formation of nanocrystalline structure of TiN, which is the main reason for the corrosion resistance improvement of TiNi alloy. The existence of the transition area contributes to the adhesive strength between the film and the substrate. The unique shape memory effect of TiNi alloy is least affected by the PHEDP surface-coating technique. (C) 2000 Published by Elsevier Science B.V. All rights reserved.