Effect of the Wettability of F-DLC Coatings on Oil Film Lubrication under Surface Contact

YU Yongan; FU Yongqiang; GUO Feng; WANG Jiarong

doi:10.16490/j.cnki.issn.1001-3660.2026.11.017

PDF(5592 KB)

Surface Technology ›› 2026, Vol. 55 ›› Issue (11) : 196-209. DOI: 10.16490/j.cnki.issn.1001-3660.2026.11.017

Friction, Wear and Lubrication

Effect of the Wettability of F-DLC Coatings on Oil Film Lubrication under Surface Contact

YU Yongan¹, FU Yongqiang^1,*, GUO Feng^1,*, WANG Jiarong²

Author information +

History +

Abstract

The work aims to systematically investigate the effect of interfacial wettability on lubricant film thickness and friction force under hydrodynamic lubrication conditions, with the goal of optimizing characterization parameters for solid-liquid interfaces. The innovative contribution of this work lies in the use of an MS-0808 high-density plasma application platform to achieve precise control of surface wettability via fluorine-doped diamond-like carbon (F-DLC) coatings, along with a comprehensive evaluation of multiple interfacial characterization parameters to identify the most effective one for characterizing lubrication behavior. Atomic force microscopy (AFM) characterization of surface morphology and roughness revealed nanoscale variations (Ra: 3.37-9.92 nm) across all surfaces, though these differences had no significant impact on wettability or lubrication performance. Raman spectroscopy confirmed the diamond-like structure of the coatings and indicated that as the CF₄ gas flow rate increased, the sp²/sp³ ratio of the coatings rose, suggesting an increase in graphitic structure with higher fluorine content. With the slider-on-disc lubricant film measurement system, the film thickness and friction force generated by base PAO and glycerol aqueous solution were measured on these five surfaces. All measurements were performed in a controlled environment (temperature (20±2) ℃, relative humidity (55±5)%) with sliding speeds ranging from 1.99 to 79.24 mm/s. The selected lubricants with matched viscosities included polyalphaolefin (PAO10 and PAO20) and glycerol aqueous solutions (86%GS and 94%GS). For each solid-liquid combination, the contact angle (θ_CA), contact angle hysteresis (θ_CAH), surface energy, and derived parameters including adhesion work (W_A), energy barrier (E), and spreading coefficient (η_SP) were also determined. The results showed that the F-DLC coatings significantly reduced surface energy, particularly the polar component. Under lubrication with glycerol aqueous solution, both film thickness and friction force decreased continuously with the increasing fluorine content, in the following order: film thickness: steel > 10F-DLC > 20F-DLC > 30F-DLC > 40F-DLC and friction force: steel > 10F-DLC > 20F-DLC > 30F-DLC > 40F-DLC. In contrast, the differences in film thickness and friction force for PAO oil across the various surfaces were negligible. The spreading coefficient (η_SP) exhibited an almost perfect correlation with friction force (Pearson correlation coefficient r=0.99), significantly outperforming other wettability parameters such as contact angle, contact angle hysteresis, adhesion work, and energy barrier in predicting interfacial slip behavior. The polar component of surface energy also showed a strong positive correlation with friction force (r=0.97), confirming its dominant role in interfacial slip behavior. This work demonstrates that solid-liquid interfacial wettability has a significant effect on hydrodynamic lubrication performance. F-DLC coatings with low surface energy, especially low polar components, promote interfacial slip, resulting in thinner oil films and reduced friction. Among various wettability characterization parameters, the spreading coefficient proves to be the most effective parameter for characterizing interfacial effects under full-film lubrication conditions. These findings provide new insights into the design of low-friction interfaces through surface energy modulation and highlight the importance of polar interactions in solid-liquid lubrication mechanisms. Highly polar surfaces suppress slip and increase friction, whereas low-polar surfaces facilitate slip relative to the former, thereby improving friction performance.

Key words

diamond-like carbon coating / solid-liquid composite lubrication / wettability / interfacial slip / interfacial characterization parameters

Cite this article

EndNote

Ris (Procite)

Bibtex

Download Citations

YU Yongan, FU Yongqiang, GUO Feng, WANG Jiarong. Effect of the Wettability of F-DLC Coatings on Oil Film Lubrication under Surface Contact[J]. Surface Technology. 2026, 55(11): 196-209

References

[1] TANG W W, ZHANG Z, LI Y F.Applications of Carbon Quantum Dots in Lubricant Additives: A Review[J]. Journal of Materials Science, 2021, 56(21): 12061-12092.
[2] MACIÁN V, TORMOS B, BERMÚDEZ V, et al. Assessment of the Effect of Low Viscosity Oils Usage on a Light Duty Diesel Engine Fuel Consumption in Stationary and Transient Conditions[J]. Tribology International, 2014, 79: 132-139.
[3] BJÖRLING M, ISAKSSON P, MARKLUND P, et al. The Influence of DLC Coating on EHL Friction Coefficient[J]. Tribology Letters, 2012, 47(2): 285-294.
[4] MACIÁN V, TORMOS B, RUIZ S, et al. Low Viscosity Engine Oils: Study of Wear Effects and Oil Key Parameters in a Heavy Duty Engine Fleet Test[J]. Tribology International, 2016, 94: 240-248.
[5] 李玉龙, 何永勇, 雒建斌. 航空柱塞泵关键摩擦副表面改性与性能增强[J]. 清华大学学报(自然科学版), 2021, 61(12): 1405-1422.
LI Y L, HE Y Y, LUO J B.Surface Modifications and Performance Enhancements of Key Friction Pairs in Aviation Hydraulic Piston Pumps[J]. Journal of Tsinghua University (Science and Technology), 2021, 61(12): 1405-1422.
[6] SPIKES H A.The Half-Wetted Bearing. Part 1: Extended Reynolds Equation[J]. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2003, 217(1): 1-14.
[7] SPIKES H A.The Half-Wetted Bearing. Part 2: Potential Application in Low Load Contacts[J]. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2003, 217(1): 15-26.
[8] 杨淑燕, 郭峰, 马冲, 等. 固液润湿性对流体动压润滑薄膜的影响[J]. 摩擦学学报, 2010, 30(2): 203-208.
YANG S Y, GUO F, MA C, et al.Influences of the Liquid/ Solid Wettability on Thin Hydrodynamic Lubrication Films[J]. Tribology, 2010, 30(2): 203-208.
[9] 王志君, 郭峰, 田鹏晖. 界面黏附功与润滑油膜厚度的相关性研究[J]. 润滑与密封, 2016, 41(12): 52-56.
WANG Z J, GUO F, TIAN P H.Correlation of Interface Adhesion Work and Hydrodynamic Lubrication[J]. Lubrication Engineering, 2016, 41(12): 52-56.
[10] 田鹏晖, 郭峰, 王志君, 等. 固液界面对流体动压润滑膜厚的影响[J]. 表面技术, 2016, 45(10): 77-82.
TIAN P H, GUO F, WANG Z J, et al.Effects of the Liquid/Solid Interface on Thickness of Hydrodynamic Lubricating Films[J]. Surface Technology, 2016, 45(10): 77-82.
[11] GUO L, WONG P L, GUO F.Correlation of Contact Angle Hysteresis and Hydrodynamic Lubrication[J]. Tribology Letters, 2015, 58(3): 45.
[12] 王茜, 韩素立, 郭峰, 等. 接触角滞后与流体动压润滑的相关性研究[J]. 摩擦学学报(中英文), 2019, 39(3): 340-349.
WANG Q, HAN S L, GUO F, et al.Correlation between Contact Angle Hysteresis and Hydrodynamic Lubrication[J]. Tribology, 2019, 39(3): 340-349.
[13] 杜军, 何家文. 类石墨碳膜的制备及其与类金刚石碳膜的区分[J]. 中国表面工程, 2005, 18(4): 6-8.
DU J, HE J W.The Preparation of Graphite-Like-Carbon Film(GLC) and Difference from Diamond-Like-Carbon (DLC) Film[J]. China Surface Engineering, 2005, 18(4): 6-8.
[14] RYU H, KIM J, KIM J, et al.Enhancement of a Heat Transfer Performance on the Al6061 Surface Using Microstructures and Fluorine-Doped Diamond-Like Carbon (F-DLC) Coating[J]. International Journal of Heat and Mass Transfer, 2020, 148: 119108.
[15] ZHOU C B, RU L, XIAO J R, et al.Cr Content Regulates the Friction and Corrosion Resistance of Cr/F-DLC Thin Films[J]. Diamond and Related Materials, 2025, 157: 112482.
[16] HOQUE M J, LI L N, MA J C, et al.Ultra-Resilient Multi-Layer Fluorinated Diamond Like Carbon Hydrophobic Surfaces[J]. Nature Communications, 2023, 14: 4902.
[17] ZHANG L F, WANG F G, QIANG L, et al.Recent Advances in the Mechanical and Tribological Properties of Fluorine-Containing DLC Films[J]. RSC Advances, 2015, 5(13): 9635-9649.
[18] KALIN M, POLAJNAR M.The Effect of Wetting and Surface Energy on the Friction and Slip in Oil-Lubricated Contacts[J]. Tribology Letters, 2013, 52(2): 185-194.
[19] POLAJNAR M, BIZJAN B, ŠIROK B, et al.High-Speed Optical Imaging of Liquid Film Flow and Liquid Macro- Slip over Free Surfaces with Different Surface Energies[J]. Lubrication Science, 2017, 29(8): 557-566.
[20] JING Z G, GUO F, JIN W, et al.Study on the Influence of Interfacial Slip on the Lubrication Performance of a Step Slider Bearing[J]. Tribology International, 2022, 176: 107822.
[21] 王茜, 韩素立, 郭峰. 流体动压润滑油膜厚度及油池的荧光测量[J]. 润滑与密封, 2019, 44(5): 57-63.
WANG (Q /X), HAN S L, GUO F. Film Thickness and Oil Pool Measurement of Hydrodynamic Lubrication by Fluorescence Method[J]. Lubrication Engineering, 2019, 44(5): 57-63.
[22] 杜士杰, 荆兆刚, 郭峰, 等. 面接触油膜润滑摩擦力测量系统的设计及试验研究[J]. 润滑与密封, 2024, 49(11): 138-144.
DU S J, JING Z G, GUO F, et al.Design and Experimental Study of Slider-on-Disc Contact Oil Film Lubrication Friction Measurement System[J]. Lubrication Engineering, 2024, 49(11): 138-144.
[23] 王良旺, 徐岩岩, 何立粮, 等. 石墨烯材料结构形貌检测方法研究进展[J]. 中国测试, 2024, 50(S1): 1-5.
WANG L W, XU Y Y, HE L L, et al.Research Progress of Detection Methods for the Structure and Morphology of Graphene Materials[J]. China Measurement & Test, 2024, 50(S1): 1-5.
[24] RU L, WANG Y R, LIU J J, et al.Hydrophobic, Anticorrosion, and Frictional Properties of F-DLC Films Prepared by Magnetron Sputtering[J]. Vacuum, 2023, 217: 112567.
[25] BA E C T, DUMONT M R, MARTINS P S, et al. Deconvolution Process Approach in Raman Spectra of DLC Coating to Determine the Sp3 Hybridization Content Using the ID/IG Ratio in Relation to the Quantification Determined by X-Ray Photoelectron Spectroscopy[J]. Diamond and Related Materials, 2022, 122: 108818.
[26] WANG J, ZHANG K, ZHANG L F, et al.Influence of Structure Evolution on Tribological Properties of Fluorine- Containing Diamond-Like Carbon Films: From Fullerene- Like to Amorphous Structures[J]. Applied Surface Science, 2018, 457: 388-395.
[27] DONG D, JIANG B L, LI H T, et al.Effect of Graphite Target Power Density on Tribological Properties of Graphite-Like Carbon Films[J]. Applied Surface Science, 2018, 439: 900-909.
[28] MARCIANO F R, LIMA-OLIVEIRA D A, DA-SILVA N S, et al. Antibacterial Activity of Fluorinated Diamond- Like Carbon Films Produced by PECVD[J]. Surface and Coatings Technology, 2010, 204(18/19): 2986-2990.
[29] CUI W G, LAI Q B, ZHANG L, et al.Quantitative Measurements of sp³ Content in DLC Films with Raman Spectroscopy[J]. Surface and Coatings Technology, 2010, 205(7): 1995-1999.
[30] BENDAVID A, MARTIN P J, RANDENIYA L, et al.The Properties of Fluorine Containing Diamond-Like Carbon Films Prepared by Plasma-Enhanced Chemical Vapour Deposition[J]. Diamond and Related Materials, 2009, 18(1): 66-71.
[31] VORONOV R S, PAPAVASSILIOU D V, LEE L L.Review of Fluid Slip over Superhydrophobic Surfaces and Its Dependence on the Contact Angle[J]. Industrial & Engineering Chemistry Research, 2008, 47(8): 2455-2477.
[32] SALANT R F, FORTIER A E.Numerical Analysis of a Slider Bearing with a Heterogeneous Slip/no-Slip Surface[J]. Tribology Transactions, 2004, 47(3): 328-334.
[33] JOSEPH P, TABELING P.Direct Measurement of the Apparent Slip Length[J]. Physical Review E, 2005, 71(3): 035303.
[34] HENRY C L, NETO C, EVANS D R, et al.The Effect of Surfactant Adsorption on Liquid Boundary Slippage[J]. Physica A: Statistical Mechanics and Its Applications, 2004, 339(1/2): 60-65.
[35] WHYMAN G, BORMASHENKO E, STEIN T.The Rigorous Derivation of Young, Cassie-Baxter and Wenzel Equations and the Analysis of the Contact Angle Hysteresis Phenomenon[J]. Chemical Physics Letters, 2008, 450(4/5/ 6): 355-359.

Funding

National Natural Science Foundation (52205204, 52575217); Shandong Provincial National Natural Science Foundation Youth Project (ZR2024QE047); Shandong Province Higher Education Institutions Youth Innovation Team Project (2023KJ116); Qingdao Postdoctoral Research Project Foundation (QDBSH20240201003)