CHARACTERIZATIONS OF DLC/MAO COMPOSITE COATINGS ON AZ80 MAGNESIUM ALLOY

Abstract

Diamond-like carbon (DLC) coating has been widely used to modify the surface mechanical and tribological properties of materials. In most cases, a metallic buffer (e.g., Ti) is used as an interlayer between DLC coating and the substrate to improve the adhesion. In this work, the DLC coating was deposited on the AZ80 Mg alloy substrate using ion beam deposition technique. Specially, a pretreatment of microarc oxidation (MAO) was applied to the Mg alloy substrates to form the DLC/MAO composite coating instead of the metallic interlayer process. As a comparation, the DLC/Ti/MAO and DLC/Ti composite coatings were also deposited on the substrates. The sur- face morphology and roughness, mechanical, tribological and corrosion properties of the as-deposited coatings were studied. The results indicated that the DLC/MAO composite coating could signifi- cantly improved the hardness and wear resistance of the Mg alloy substrates compared with the MAO monolayer. Although the surface roughness of the DLC/MAO coating showed an increase due to the micropores of the MAO coating surface, the friction coefficient and the wear tracks exhibited a sim- ilar behavior to that of the DLC/Ti coating. Furthermore, the DLC/Ti/MAO/AZ80 system showed the best tribological properties among the current experimental samples. Meanwhile, the polarization