Abstract
Nanocrystalline TiN thin films were successfully deposited on Si (100) and D2 steel substrates using unbalanced magnetron sputtering (UBMS) system. The objective of this study was to investigate the effect of film thickness and Ti interlayer thickness on the composition, structures, mechanical properties, and corrosion resistance of TiN film. The results showed that (111) was the dominant preferred orientation in the TiN films. The effects of the film thickness were only slightly varied on the N/Ti ratio, roughness, and grain size. The packing factor was almost constant with film thickness and the thinnest specimen reached a quite high packing factor of 0.8. Nanoindentation data, ranging from 22~29 GPa, indicated that hardness of the films was not related to the film texture and film thickness. The residual stresses of all TiN films were compressive, and mostly decreased with increasing film thickness in TiN/D2 specimens. Interfacial shear stress induced from the residual stress was increased with film thickness, whereas the residual stress was not necessarily increased with film thickness. In the bi-layer TiN/Ti coating, there was a critical Ti interlayer thickness (120~150nm) to effectively reduce the thermal stress and residual stress in the TiN coating. The results of potentiodynamic polarization scan in both 5% NaCl and 0.5M H2SO4 + 0.05M KSCN solutions indicated that packing factor was more effective than film thickness to the corrosion resistance for the coating. Furthermore, increasing film thickness or adding a Ti interlayer could effectively protect the substrate from the corrosive medium, if the packing factor was sufficiently high.