| AN Fengyang,GUO Feng,LIU Chenglong,JU Chao,WANG Xiaobo.Effect of Organic Friction Modifiers on Lubrication Characteristics of Mineral Oil under Ball-to-Disk Contact[J],54(9):70-78 |
| Effect of Organic Friction Modifiers on Lubrication Characteristics of Mineral Oil under Ball-to-Disk Contact |
| Received:July 11, 2024 Revised:January 07, 2025 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2025.09.005 |
| KeyWord:full film lubrication organic friction modifiers 500SN film thickness friction coefficient wettability |
| Author | Institution |
| AN Fengyang |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Shandong Qingdao , China |
| GUO Feng |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Shandong Qingdao , China |
| LIU Chenglong |
School of Mechanical and Automotive Engineering, Qingdao University of Technology, Shandong Qingdao , China |
| JU Chao |
State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou , China |
| WANG Xiaobo |
State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou , China |
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| Abstract: |
| The work aims to investigate the effect of in-situ adsorption of organic friction modifier molecules with various functional group polarities on elastohydrodynamic lubrication (EHL). Mineral oil 500SN and 500SN with 3 organic friction modifiers, i.e. 4% oleyl alcohol, 4% oleamide and 4% oleic acid (labeled respectively 500SNOH, 500SNCONH2 and 500SNCOOH) were used as the lubricants. With an optical ball-on-disk test machine, the oil film thickness and the friction coefficient of 500SN, 500SNOH, 500SNCONH2 and 500SNCOOH were measured at various slide-roll ratios and entrainment speeds. The organic friction modifiers adsorbed on the surface of steel balls were characterized by contact angle (CA) measuring instrument, Fourier transform infrared spectrometer (FTIR) and atomic force microscope (AFM), and the relationship between the strength of adsorption of organic friction modifier molecules and the functional group polarity was determined. Under the same working conditions, the central film thickness and the friction coefficient of 500SNOH, 500SNCONH2 and 500SNCOOH were all lower than those of 500SN, and the greater the polarity of the functional group of the organic friction modifier the lower the film thickness and the friction coefficient. The oleic acid molecule in 500SNCOOH had the greatest polarity and the strongest adsorption capacity, resulting in the lowest film thickness and friction coefficient, while the oleyl alcohol molecule had the weakest adsorption, presenting the lowest film thickness and friction coefficient of 500SNOH among the lubricants with organic friction modifiers. Under the conditions of low slide-roll ratios, the friction coefficients of 500SN, 500SNOH, 500SNCONH2 and 500SNCOOH all showed a trend of first decreasing and then increasing with the increase of entrainment speed. At the slip-roll ratio of 0.05, the average friction coefficients of 500SNOH, 500SNCONH2 and 500SNCOOH presented decrease by 6.07%, 15.79% and 24.57%, respectively, in the range of 1-512 mm/s, compared with 500SN. Under the condition of large slip-roll ratio, the friction coefficients of 500SN, 500SNOH, 500SNCONH2 and 500SNCOOH all decreased first, then increased and decreased with the increase of entrainment speed. Under the condition of low entrainment speed, due to shear thinning and some heat generation, the central oil film thickness of 500SN, 500SNOH, 500SNCONH2 and 500SNCOOH decreased with the increase in the slip-roll ratio. At the entrainment speed of 32 mm/s and slip-roll ratio of 0.05, the central oil film thickness of 500SNOH, 500SNCONH2 and 500SNCOOH decreased by 15.32%, 22.58% and 26.61%, respectively, compared with 500SN. When increased entrainment speed was used, with the increasing slide-roll ratio, more heat was generated and the temperature-viscosity wedge was induced, where the central oil film thickness of 500SN, 500SNOH, 500SNCONH2 and 500SNCOOH could not decrease, which was contrary to those at the entrainment speed of 32 mm/s. The measurement results of contact angle, Fourier infrared spectrometer and atomic force microscope show that the organic friction modifiers with different functional groups can form an oleophobic boundary film on the surface of the steel ball by in-situ adsorption, thus reducing the wettability of the lubricant on the surface of the steel ball. It is also verified that the stronger the polarity of the organic friction modifier molecular functional group, the stronger the adsorption capacity of the organic friction modifier molecule and the poorer the wettability of the formed oleophobic boundary film. |
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