Influence of surface microstructure on tribological properties of PEO-PTFE coating formed on aluminum alloy

Abstract

Abstract Self-lubricating polytetrafluoroethylene-containing PEO (PEO-PTFE) composite coatings were prepared by vacuum impregnation on plasma electrolytic oxidized aluminum alloy with different cathodic voltages. The topography, microstructure and composition of the composite coatings were investigated by FESEM equipped with EDX and XRD. The friction and wear properties were evaluated in the load range of 5–20\u202fN using a reciprocating tribometer. The results show that the tribological properties of PEO-PTFE composite coatings are greatly influenced by the surface microstructure of PEO coating. The PEO coating fabricated at 150\u202fV cathodic voltage shows coarser microstructure, while the corresponding PEO-PTFE composite coating registers superior self-lubricated property with lowest friction coefficient of 0.1 and 0.09 under the applied loads of 5\u202fN and 10\u202fN, respectively. In term of wear resistance ability, the 90\u202fV composite coating possesses relatively low wear rate about 7.47\u202f×\u202f10−6\u202fmm3·(N·m)−1 with the coefficient of 0.13 under the test load of 10\u202fN. The increased microcracks and diameter of micropores, like “grooves” and “ridges” on PEO coating, is beneficial for providing the scope for low-lubricating PTFE material, which can form smooth lubricating film during the friction process.