AlN/Ti/TiN/DLC layers more than 1 µm thick have been prepared by plasma-based ion implantation sequentially with nitrogen/titanium/nitrogen and titanium/carbon on 2024 aluminium alloy. On the basis of our previous AlN/Ti/TiN/DLC layers, new AlN/Ti/TiN/DLC layers thicken by thickening the ‘TiN’ layer and the diamond-like (DLC) film. The structures of the new layers have been characterized by XPS, AFM and Raman spectrum. The new layers exhibit improved composition and structure gradients at the interface in addition to a thicker ‘TiN’ layer and DLC film than the previous ones and hence display significant improvements in surface hardness and tribological properties. Also, their surface topography, DLC structure, nanohardness, stress and tribological properties as a function of the DLC film thickness have been discussed.