The Oxidation Behavior and Corrosion Resistance of ZrN Thin Films Heat Treated in Vacuum

• Main Authors: Chou, Sun-An, 周孫安
• Other Authors: Huang, Jia-Hong
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/61533064935754445404

碩士 === 國立清華大學 === 工程與系統科學系 === 102 === The purpose of this study was to investigate the oxidation behavior and corrosion resistance of heat-treated ZrN thin films. ZrN thin films were deposited on the 304 stainless steel by unbalanced magnetron sputtering system (UBMS), and then heat treated to grow ZrO2 at 1000C in vacuum (4 × 10-6 Torr) over the duration ranging from 1 to 4 hours. The results of XRD showed that the phase constituents of the heat-treated ZrN were ZrN, m-ZrO2 and t-ZrO2, where ZrN was still the major phase in the thin film even after 4-hr heat treatment. Furthermore, the compositional depth profiles indicated that there were two layers of ZrO2 on the film surface and at film/substrate interface, respectively. The retained ZrN was in the middle part of thin film and the entire thin film displayed a multilayer structure. The ZrO2 layer at film/substrate interface may result from the stress relief of substrate at high temperature. In the 1-hr duration, t-ZrO2 layer was formed at interface, while m-ZrO2 layer was formed on the film surface and Zr(N,O) layers containing m-ZrO2 formed next to t-ZrO2 and m-ZrO2 layers, where the transformation from ZrN to m-ZrO2 led to about 50% of film thickening. The film thickness remained constant with further increase of annealing duration, indicating that the oxidation mainly progressed by the formation of t-ZrO2 at the expense of ZrN or Zr(N,O), where the volume change of phase transformation is restricted by the large compressive stress. The corrosion behavior was determined by potentiodynamic polarization scan, 500-hr salt spray test and electrochemical impedance spectroscopy. The results show that the heat-treated ZrN exhibited excellent corrosion resistance, especially in 5 wt. % NaCl solution. The corrosion current density decreased with increasing annealing duration and reached up to 1000 times after annealing in vacuum for 2 hours. The corrosion area of the oxidized ZrN after 500-hr salt spray test also decreased with the increasing heat treatment duration and downs to 3% after 4-hr heat treatment.