Abstract
The formation of chromium carbide-based hard-coatings on steels using a 90°-bend filtered cathodic vacuum arc (FCVA) has extensive industrial applications; such coatings are free of macroparticles and exhibit excellent characteristics. In this investigation, a working pressure of C 2H 2/Ar was adopted to synthesize amorphous chromium carbide film (a-C:Cr) and crystalline chromium carbide film (cryst-Cr 3C 2) from a Cr target (99.95%) at 500 °C under a substrate voltage of −50 V. The corrosion behavior of a-C:Cr coated on steel (a-C:Cr/steel) and cryst-Cr 3C 2 coated on steel (cryst-Cr 3C 2/steel) were compared in terms of open-circuit potentials (OCP) and polarization resistance ( R p) in an aerated 3.5 wt% NaCl aqueous solution, as determined by electrochemical impedance spectroscopy (EIS). The XRD results indicated that the transformation of a-C:Cr to cryst-Cr 3C 2 is distinct as the working pressure declines from 1.2 × 10 −2 to 2.9 × 10 −3 Torr. The OCP of a-C:Cr/steel and cryst-Cr 3C 2/steel resemble each other and both assembly are nobler than uncoated steel. The R p of the coatings exceeds that of the uncoated steel. The SEM observation and the EIS results demonstrate that the cryst-Cr 3C 2/steel more effectively isolates the defects than dose a-C:Cr/steel.
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