Robust ceramic based self-lubricating coating on Al–Si alloys prepared via PEO and spin-coating methods

Ceramic based self-lubricating coating was successfully fabricated on Al-based plasma electrolytic oxidation (PEO) ceramic coating in this work. The coating was reinforced with thermosetting polyimide (PI) containing tungsten disulfide (WS 2 ) fillers. The morphology, chemical composition and phase structure of the PEO, PEO/PI and PEO/PI/WS 2 coatings were observed by SEM, EDS and XRD , respectively. Tribological properties of the coatings were comparatively investigated using a reciprocating pin-on-block tribotester under different conditions. Under dry sliding conditions, the friction coefficient of PEO/PI/WS 2 coating was about 0.4, which was 50% lower than that of PEO coating. Meanwhile, the wear rate of counter pin cooperated with PEO/PI/WS 2 coating was only 0.04 mg min −1 , which was 90.9% lower than that of PEO coating. Under step loading conditions, the load was ultimately increased to 70 N and the total duration time was about 35 min, while the corresponding values of PEO coating were 30 N and 13 min, respectively. These are owed to the hard ceramic coating and the soft self-lubricating coating, which can improve the load capacity and decrease the friction, of the ceramic based self-lubricating coating.