Corrosion behavior and adhesion of ion-plated TiN films on AISI 304 steel

Titanium nitride films were deposited on AISI 304 steel with a hollow-cathode-discharge (HCD) ion-plating technique. An extensive investigation on the corrosion behavior and adhesion of TiN-coated samples was performed. The corrosion resistance was evaluated by a potentiodynamic polarization method in 1 N H2SO4+0.05 M KSCN solution and the ASTM standard B-117 salt spray test. The ultimate shear stress, proportional to the banding strength between coating and substrate, was measured by a periodic cracking method to reflect the adhesion of the coating. To obtain good adhesion of the TiN film to the substrate, a Ti interlayer was introduced to form a TiN/Ti/steel structure. The experimental results demonstrate that the corrosion properties of the TiN-coated AISI 303 steel samples are determined first by the influence of the synergetic effect, that is the packing factor and the thickness associated with the coatings, and second by the adhesion of TiN coatings to the substrate. From the results of the interfacial stress and SIMS depth-profile measurements, the adhesive strength of the coated-samples increases with increasing interdiffusion layer thickness. Furthermore, it also indicates that the Ti sublayer can enlarge the pseudo-diffusion layer and enhance the adhesion strength of TiN coatings. For the TiN/Ti double-layered coating, good corrosion resistance can be obtained with the measured ultimate shear stress higher than 10 GPa and the interdiffusion zone thicker than 0.2 mu m (C) 2000 Elsevier Science S.A. All rights reserved.