Microstructure, mechanical and corrosion properties of TiN/Ni nanomultilayered films

Abstract

Nanomultilayered TiN/Ni thin films with different bilayer periods (57.8–99.7 nm) and Ni single-layer thickness (3.9–19.2 nm) were prepared by alternatively sputtering Ti and Ni targets in N₂ gas atmosphere. The microstructure, mechanical and corrosion properties of the multilayer films were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), nanoindenter and electrochemical technologies. The multilayer films are fine with a mean grain size of ~ 8–9 nm independent of the bilayer period. However, the smoothness and compactness seem to decrease with the bilayer period increasing. The hardness (H) and elastic modulus (E) of the multilayer films gradually decrease as the bilayer period increases, and the multilayer film with bilayer period of 57.8 nm exhibits higher H, ratios of $(H/E^{*} \,\,{\text{and}}\,\,H^{3} /E^{*2} )$ ($E^{*}$ is effective Young’s modulus) than the monolithic TiN film and the other multilayers. The multilayer films exhibit an obvious passivation phenomenon in 10% H₂SO₄ solution, and the passive current and corrosion current densities decrease, whereas the corrosion potential increases when the bilayer period or Ni single-layer thickness decreases. It is found that the passivating behavior and corrosion potential of the multilayers are more sensitive to Ni single-layer thickness than the bilayer period. More corrosion pits and lamellar flaking could be found on the films with larger bilayer period or Ni single-layer thickness.