The effect of electron irradiation on the tribological property of perfluoropolyether grease in vacuum

Abstract

Abstract A perfluoropolyether (PFPE) grease was exposed to 110 keV electron beam for fluence of 1 × 1015, 5 × 1015 and 1 × 1016 e/cm2 in vacuum. The friction and wear behaviour of the electron irradiated grease-lubricated 2Cr13 steel in vacuum was investigated by using a pin-on-disk type tribometer. The morphologies of the worn surfaces for the irradiated grease-lubricated 2Cr13 steel were observed by a scanning electron microscope (SEM). Gaseous products from the PFPE grease during the electron irradiation were monitored with a quadrupole mass spectrometer (QMS). The compositions and chemical states of grease samples before and after electron irradiation were analysed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Results show that the irradiated grease-lubricated 2Cr13 steel sliding against the same material in vacuum presents a high friction and a high wear. The QMS, XPS and FTIR analyses reveal that COF2 gas, low molecular weight perfluoroethers and acid fluoride groups are formed due to decomposition when the PFPE grease is exposed to 110 keV electron beam in vacuum. Moreover, the base oil content of the PFPE grease decreases with increasing the electron irradiation fluence, leading to the loss of lubricating ability of the PFPE grease.