Mechanical properties and corrosion resistance of nanocrystalline ZrNxOy coatings on AISI 304 stainless steel by ion plating

✍ Scribed by Jia-Hong Huang; Zhang-En Tsai; Ge-Ping Yu

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 817 KB
• Volume: 202
• Category: Article
• ISSN: 0257-8972
• DOI: 10.1016/j.surfcoat.2008.05.001

✦ Synopsis

Transition metal oxynitrides have become emerging decorative coating materials due to their adjustable coloration and high hardness and corrosion resistance. This research studied the effect of oxygen content on the coloration, mechanical properties and corrosion resistance of ZrN x O y thin films deposited on AISI 304 stainless steel using hollow cathode discharge ion plating (HCD-IP). The Zr/N/O ratios of the ZrN x O y films were determined using X-ray photoelectron spectroscopy (XPS). The color of the ZrN x O y thin film changed from golden yellow to blue and then slate blue with increasing oxygen content. X-ray diffraction (XRD) patterns revealed that phase separation of ZrN and m-ZrO 2 occurred as the oxygen content reached 31.2 at.%. ZrN(O) (ZrN with dissolving oxygen) is dominant at oxygen content less than 18.1 at.%, while m-ZrO 2 phase was prevailed at oxygen content above 40.3 at.%. Phase separation lowered the hardness of the ZrN x O y films as the fraction of ZrO 2 was less than 40%. The residual stresses in ZrN phase was higher than that in ZrO 2 , and the residual stress decreased for the specimen containing 30 to 37% ZrO 2 . For the samples containing more than 44% ZrO 2 , the average residual stress was close to that in ZrO 2 phase. The corrosion resistance was evaluated by salt spray test and potentiodynamic scan in two solutions: 0.5MH 2 SO 4 + 0.05 M KSCN and 5% NaCl solutions. The results showed consistent trend in the two solutions. From the results of potentiodynamic scan, corrosion resistance increased as the packing density of the film increased, whereas the film thickness was not a crucial factor on corrosion current; moreover, the electrical conductivity of the film may be one of the significant factors in corrosion resistance. Results of salt spray tests suggested that the corrosion of ZrN x O y in NaCl may play an important role in corrosion resistance.