Effect of Irradiation Dose on the Structure and Tribological Performance of Ti:WS 2 /PFPE Composite Lubricating System in Atomic Oxygen Environment

AbstractPerfluoropolyether (PFPE) oil possessing higher oxidation stability than hydrocarbon lubricant is combined with Ti:WS2 film to construct a solid–liquid composite lubricating system. The results indicate that atomic oxygen (AO) irradiation generates some important effects for the Ti:WS2/PFPE composite lubricating system. With an increase of irradiation dose, the molecular structure of PFPE oil experiences carbon chain breakage and appears to be an obvious molecule for cross-linking and polymerization. Meanwhile, Ti:WS2 film also is oxidized to a different extent to form WO3. The changes in the solid–liquid system resulted in greatly different tribological properties of the Ti:WS2/PFPE system. The friction coefficient of the system significantly increases with low-dose irradiation, while inversely, the value sharply decreases with high-dose AO, which is related to the presence of WO3 and formation of a transfer film. Finally, the failure mechanism of Ti:WS2/PFPE system under AO irradiation has been revealed.Keywords: Solid–liquid lubricationPFPE oilAO irradiationtribological performancefailure mechanism Disclosure StatementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis research was supported by the National Natural Science Foundation of China (51835012, 51975554), Basic Research Project (no. 2020-JCJQ-ZD-155-12), Gansu Natural Science Foundation under grant numbers 21JR7RA091 and 22JR5RA109, and Young Elite Scientists Sponsorship Program by CAST.