Using aluminum in some applications increases the surface temperature. Low hardness along with low wear resistance cause fast failure of the metal. Anodizing process in optimized conditions makes a hard alumina coating with hardness values about ten times that of the aluminum substrate, but high friction coefficient is a big draw back for this oxide coating. The purpose of the present research is to decrease of friction coefficient of AAO (Aluminum Anodic Oxide) coatings by incorporation of PTFE as a solid lubricant on nanostructured anodic aluminum oxide. Hard AAO was made by optimization of voltage and time of the process. Then, lubricant layers were produced from solutions containing 15, 20, 25 and 30 ml/l PTFE. Finally, for increasing the PTFE layer adhesion to hard AAO coating, heat treatment process was done. For characterization of coatings, X-Ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), and Energy Dispersive Spectroscopy (EDS) were used. Experimental results indicated that the size of nano-pores were in range of 5-16 nm. Heat treatment process was carried out at 400 °C for 30 min. Changes in nano-hardness, elastic modulus and fracture toughness evaluated by Atomic Force Microscope (AFM). A large increase in nano hardness and elastic modulus, and a decrease in fracture toughness were observed by heat treatment. To study the tribology of the specimens, a pin-on-disc wear tester was employed with AISI 52100 steel pins. The tribological behavior at high temperatures was evaluated by wear testing at 150 °C and 300 °C. Weight loss of pin and samples was measured and the effect of temperature on wear behavior was studied. It was found that increasing PTFE at room temperature caused a decrease in friction coefficient, but this was not true at high temperatures. At ambient temperature, the best tribological behavior was observed in sample with 30 ml/l PTFE, but at high temperature, in the sample with 20 ml/l. Wear surfaces of pins and samples were evaluated by Scanning Electron Microscope. Keywords Anodizing, Aluminum, PTFE, Solid Lubricant, Anodic Oxide, Friction Coefficient.
