Microstructure and tribological behavior of self-lubricating (Si:N)-DLC/MAO coatings on AZ80 magnesium substrate

Abstract

The combined micro arc oxidation (MAO) and a hybrid beam deposition process was used to deposit duplex (Si:N)-DLC/MAO coatings on AZ80 magnesium alloy. The microstructure and composition of the duplex coatings were analyzed by Raman spectroscopy, X-ray photoelectron spectroscope (XPS), scanning electron microscope (SEM) and atomic force microscopy (AFM). Tribological behaviors of the coatings were studied by ball-on-disk friction test. It was found that the ID/IG ratio of the (Si:N)-DLC (diamond-like carbon) top films increases with decreasing C2H2/N2 ratio. The (Si:N)-DLC top film with Si3N 4 was formed on the MAO coated sample as the C2H2/N2 ratio was 10sccm:5sccm, which showed an increasing critical load compared with the pure DLC directly deposited on the Mg alloy substrate. As a result, the (Si:N)-DLC/MAO coating exhibited an advanced wear protection for the substrate. © The Chinese Society for Metals and Springer-Verlag Berlin Heidelberg.