Improved Load-Bearing Capacity and Tribological Properties of PTFE Coatings Induced by Surface Texturing and the Addition of GO

Abstract

The PTFE coatings with excellent corrosion-resistance and lubrication properties often stop functioning under high load conditions. In this study, a composite coating of PTFE filled with silane coupling agent modified graphene oxide (mGO/PTFE) was prepared by a simple spin-coating process on textured stainless steel (SS) substrate to protect the substrate from failure under high load rubbing. The grafting reaction between GO and silane coupling agent was analyzed by FTIR, Raman, XRD, TGA, and XPS. The morphologies and tribological properties of the mGO/PTFE coatings on the untextured and textured SS substrates were characterized by SEM and UMT tribometer. The results showed that GO surfaces were successfully grafted by silane coupling agent, resulting in that the composite coating of mGO/PTFE was denser than the pure PTFE coating. The tribo-test results confirmed that the groove texture processed by laser surface texture technology greatly improved the load-bearing capacity and anti-wear life of the PTFE coatings. The PTFE coating on the untextured SS surface fails within half an hour of rubbing at the applied load of 10 N, while the one on the groove-textured surface can maintain low and stable friction coefficient for a long time even under the load of 50 N. In addition, the results showed that the loading of mGO further improve the friction reduction and wear resistance of the PTFE coating on the textured SS surface. The wear scar width and the friction coefficient are significantly reduced by 70% and 30%, respectively, as the PTFE coating was filled by 1.0 wt% mGO. Finally, the mechanisms for achieving outstanding properties of the composite coating of mGO/PTFE on the textured SS surface were illustrated by analyzing the wear surfaces of the coating and the counterpart balls by SEM and EDS.