Structure and tribocorrosion behavior of TiAlCN coatings with different Al contents in artificial seawater by multi-arc ion plating

In this work, titanium aluminum carbonitride (TiAlCN) coatings with different aluminum (Al) contents were prepared on Ti-6Al-4V alloys using reactive co-sputtering in multi-arc ion plating system. The role of Al content (14.4 at.%-21.5 at.%) on the structure, mechanical properties and tribocorrosion behavior of TiAlCN coatings were studied. According to the x-ray diffraction (XRD) and High-resolution transition electron microscope (HRTEM) results, the TiAlCN coatings possess a nanocomposite structure composed of nanocrystalline TiN/TiC/AlN embedded in an amorphous carbon matrix. When the Al content is low (14.4 at.%), the coatings exhibits ultra-high hardness (42.6 GPa). Further increase of the Al content, the hardness of the coating reduced, as the formation of amorphous carbon increased in the coating (16.8 and 21.5 at.%). In addition, the coating with 14.4 at.% Al content also reveal better tribocorrosion performance in artificial seawater than other high Al content coatings as well as the substrate. This is owing to the denser structure can prevent the penetration of the corrosive media thus limits the material loss. Moreover, the material loss in tribocorrosion experiment is not only caused by the summation of pure corrosion and pure wear loss, but also the synergism between corrosion and wear takes a large proportion of the total volume loss.