Microstructure evolution, wear and corrosion resistance of Cr-C nanocomposite coatings in seawater

Cr-C nanocomposite coatings were deposited by multi-arc ion plating with various argon/acetylene mixtures. The XRD, XPS and HRTEM characterization suggest that the coatings consist of a carbide phase and an amorphous carbon-rich phase. The carbide phase is shown to be CrC with a fcc NaCl (B1) structure. Experiment findings and theoretical calculations reveal phase segregation of sp(2)-carbon from carbides in which the excess amounts of carbon are incorporated. Nanoindentation, scratch test and Rockwell indentation were performed to investigate the toughness and adhesion ability. A significant improvement of adhesion and toughness is achieved by increasing C content at the expense of hardness. The wear resistance of Cr-C coatings is controlled by the friction rather than hardness. Compared to dry friction, lower friction coefficients but higher wear rates were obtained under seawater condition. The corrosion behavior of Cr-C nanocomposite coatings with different C was determined by potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS). The coatings with higher Cr content display excellent anti-corrosion properties in seawater