Structure and tribological properties of modified layer on 2024 aluminum alloy by plasma-based ion implantation with nitrogen/titanium/carbon

2024 aluminum alloy was implanted with nitrogen then titanium finally carbon by plasma-based ion implantation to form a gradient layer. The structure and tribological properties of the layer were investigated. Its composition profiles and chemical states were analyzed with X-ray photoelectron spectroscopy (XPS). The surface carbon layer was analyzed by Raman spectrum. The appearances were observed by atomic force microscope (AFM). The surface hardness was measured with the mechanical property microprobe. The dry wear tests against GCrl5 steel ball at various sliding loads were performed with a ball-on-disk wear tester in ambient environment. The results show that the thickness of the modified layer is 1 200 nm, the carbon layer is a smooth and compact diamond-like carbon (DLC) films, and the carbon-titanium interface is broadened due to carbon ions implantation, resulting in a good composition and structure transition between DLC films and titanium layer. Surface hardness is improved markedly, with a slow and uniform change. Tribological properties are improved greatly although they reduce with the increase of sliding loads because the modified layer becomes thin rapidly.