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

• Published in: Surface & coatings technology Vol. 364; pp. 127 - 134
• Main Authors: Lu, Cheng, Feng, Xiaochun, Yang, Jingjing, Jia, Junhong, Yi, Gewen, Xie, Erqing, Sun, Yuan
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 25.04.2019; Elsevier BV
• Subjects: Aluminum alloy; Aluminum alloys; Aluminum base alloys; Cathodic coating (process); Coefficient of friction; Friction; Grooves; Lubrication; Mechanical properties; Microcracks; Microstructure; Polytetrafluoroethylene; Product design; Protective coatings; PTFE; Self lubrication; Tribological behavior; Tribology; Wear rate; Wear resistance; Microstructure; Tribological behavior; PTFE; Aluminum alloy
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2019.02.064

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 N 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 V 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 N and 10 N, respectively. In term of wear resistance ability, the 90 V composite coating possesses relatively low wear rate about 7.47 × 10−6 mm3·(N·m)−1 with the coefficient of 0.13 under the test load of 10 N. 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. •Self-lubricating PEO-PTFE coating was successfully prepared on aluminum alloy.•The cathodic voltages have great influence on the microstructure of the coatings.•The PEO-PTFE coating exhibits low coefficient of friction.•PTFE lubricating film formed on the worn surface during the friction process.