Influence of anodizing time on morphology, structure and tribological properties of composite anodic films on titanium alloy

Composite anodic films containing polytetrafluoroethylene (PTFE) nanoparticles were fabricated on Ti10V2Fe3Al by anodic oxidation in an environmentally friendly electrolyte. The influence of anodizing time on the morphology, surface roughness and crystal structure of composite anodic films were studied by using field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and Raman spectroscopy, respectively. The results show that composite anodic films had a surface full of tiny bumps and PTFE nanoparticles. The bumps grew bigger and aggregated into larger ones with increasing anodizing time until 30 min later. The tribological properties of the films were investigated by dry friction tests in terms of the friction coefficient, wear loss and the morphologies of worn surfaces. The results indicated the thickness of films and the amount of PTFE particles had a synergistic effect on anti-wear and anti-friction performance of composite anodic films. The certain thickness of films provided reliable source of wear debris. PTFE nanoparticles could lead to the formation of lubricating layer.