Tribological properties of crown-type phosphate ionic liquid as additive in poly(ethylene glycol) for steel/steel contacts

Author： Jiang Dong Hu Litian Feng Dapeng

Publisher： Emerald Group Publishing Ltd

ISSN： 0036-8792

Source： Industrial Lubrication and Tribology, Vol.65, Iss.3, 2013-04, pp. : 202-208

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Abstract

Purpose - The purpose of this paper is to design the crown-type phosphate ionic liquid additive which can dissolve in poly(ethylene glycol) (shortened to PEG) completely, and evaluate the tribological properties as additive in PEG for steel/steel contacts. Design/methodology/approach - To improve the solubility and the tribological performance of ionic liquid additive in PEG, the crown-type phosphate ionic liquid additive was prepared. The tribological properties of the crown-type phosphate ionic liquid additive in PEG were evaluated at different concentrations and rubbing frequencies on an Optimol SRV oscillating friction and wear tester. The morphology and chemical compounds of the wear scars were analyzed by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). Findings - The experimental results show that the crown-type phosphate ionic liquid additive applied in based oil exhibits better tribological properties for steel/steel contacts at different loads, concentrations and rubbing frequencies. It could improve the anti-wear ability and reduce the friction coefficients as the increased concentration. By the SEM and XPS analysis, it is found that there were the effective boundary lubricant films in the worn surface. The boundary films were composed of various tribochemical products, ferric oxide, ferric phosphate and pyrophosphate, together with the absorbed films. Originality/value - Compared with the poor miscibility of some ionic liquid in PEG, the crown-type phosphate ionic liquid additive can dissolve in PEG perfectly. It can improve the anti-wear ability and reduce the friction coefficient of PEG at different concentrations and rubbing frequencies.