Abstract
This thesis studies the effect of bias on the microstructure and properties of zirconium nitride (ZrN) coated on Si (100) and AISI 304 stainless steel. The ZrN films were deposited using hollow cathode discharge ion plating (HCD-IP) method. The optimum coating conditions were first determined using Taguchi experimental method. Based on the optimum condition, the single-variable experiment on the effect of bias was conducted. The cross-sectional microstructure reveals that the columnar structure of the ZrN film became denser with increasing bias. The results of X-ray diffraction (XRD) show that all the coating samples exhibited (111) preferred orientation both on Si and AISI 304 substrates. The microhardness values of ZrN films deposited on Si were ranging from 20~28 GPa, and on AISI 304 stainless steel were 32.5~40.8 GPa. The ZrN films deposited by HCD-IP method were very smooth with a roughness number ranging from 1.1~3.9 nm. The N/Zr ratios were close to the stoichiometric composition. The resistivity of ZrN films gradually decreases with increasing bias until -120V and then abruptly increases. The corrosion resistance of ZrN films were evaluated by standard salt spray test and potentiodynamic scanning in two kinds of solution environments: 5% NaCl and 1N H2SO4 + 0.05M KSCN, respectively. The results show a consistent trend between salt spray test and potentiodynamic scanning. The corrosion resistance increases with bias at bias ranging from 0V to -90V, then abrupt decreases at -120V, and then increases again at -150V. The properties changes of resistivity and corrosion resistance can be explained by the change of film structure due to bias-induced ion bombardment.