Compositionally and structurally graded layers prepared by plasma-based ion implantation on 2024 aluminum alloy

AlN/Ti/TiN/DLC graded layers have been prepared by plasma-based ion implantation (PBII) orderly with nitrogen / titanium / nitrogen and titanium / carbon on 2024 aluminum alloy. The structures of the graded layers have been characterized by XPS, XRD, TEM, AFM and Raman spectrum. The graded layer exhibits gradually compositional and structural change. PBII respectively with nitrogen / titanium / nitrogen and titanium / carbon can respectively form a layer rich in AlN, alpha-Ti, TiN, and sp(3) bond carbons. Every two adjacent layers are connected with a transition layer with intermediate phase such as TiC, TiCN, CNx, TiAl3, and TiO2. The intermediate phases are caused by the implantation, diffusion or recoil-implantation of nitrogen, carbon, oxygen, etc. A proper graded layer has been obtained by optimizing PBII parameters, and corresponds to the most significantly improved hardness and tribological properties.