Anti-Wear Effect of Graphene Oxide in Lubrication by Fluorine-Containing Ionic Liquid for Steel

Abstract

Although fluorine-containing ionic liquids have excellent lubricity as liquid lubricants for steels, strong tribochemical reactions leading to severe wear are occurred during friction. Recently, it is reported that graphene oxide (GO) dispersed in water and oils exhibit good anti-wear property. In this study, in order to investigate anti-wear effect of GO in lubrication of fluorine-containing ionic liquids for steel, tribological properties of mixtures of GO with concentrations of 0.2, 2, and 10 mass% and an ionic liquid ([BMIM][BF 4 ]) were investigated on a steel surface. Under the pure ionic liquid lubrication, a strong tribochemical reaction occurred, resulting in corrosion wear. Under a GO-ionic liquid mixture lubrication with 0.2 mass% GO, wear was much lower than for the pure ionic liquid lubrication. Adding GO would inhibit the strong tribochemical reaction. However, wear was high with the 10 mass% GO-ionic liquid mixture. The GO-ionic liquid mixtures did not greatly decrease the friction coefficient.

Lubrication Mechanism of Halogen-Free Ionic Liquids

“…Figures (10)(11)(12)(13) show the spectra of the TOF-SIMS analysis of the disk surface for each ionic liquid from tests at a load of 50 N and Figures (14,15) show the ion count ratios. The ion count ratio was estimated by calculating the ratio of optional mass count to all mass count.…”

“…They have potential for use as novel high-performance base oils and/or additives because of their various attractive characteristics such as low volatility and high thermal and oxidation stability [1][2][3][4][5][6][7][8][9]. It has earlier been reported that ionic liquids with halogen elements in their structure exhibit excellent lubricity for metallic materials, but severe corrosion occurs on the wear track of contacting surfaces [10][11][12][13][14][15]. To prevent the occurrence of corrosive wear, the use of halogen-free ionic liquids has been proposed.…”

“…To prevent the occurrence of corrosive wear, the use of halogen-free ionic liquids has been proposed. The use of halogen-free ionic liquids will provide lubrication without the risk of corrosion damage but their lubricating effectiveness may be inferior compared to that of the halogen-containing ionic liquids [10][11][12][13][14][15][16][17].…”

Tribological Properties of Cyano-Based Ionic Liquids under Different Environments

“…Zinc dialkyldithiophosphate (ZDDP) is a well-known lubricant additive and exhibites good tribological properties [18][19][20][21][22]. Fluorine-based ionic liquids exhibit superior tribological properties than ZDDP, because of the formation of tribo-films composed of FeF 2 and FeF 3 during sliding [8][9][10][11][12][13][14][15][16][17]23]. However, use of fluorine-based ionic liquids as a lubricant results in corrosion of metallic materials due to the formation of hydrogen fluoride [8,24].…”

“…They have been used as novel highperformance lubricants, because of their attractive properties, such as low vapor pressure, low volatility, high thermal stability, and high oxidation stability [4][5][6][7]. Most of the studies on ionic liquids as lubricants focus on fluorine-based ionic liquids, such as tetrafluoroborate, hexafluorophosphate, trifluoromethanesulfonate, and tris(perfluoroalkyl) trifluorophosphate [8][9][10][11][12][13][14][15][16][17]. Zinc dialkyldithiophosphate (ZDDP) is a well-known lubricant additive and exhibites good tribological properties [18][19][20][21][22].…”