Perspectives of the Friction Mechanism of Hydrogenated Diamond-Like Carbon Film in Air by Varying Sliding Velocity

Liu, Yuhui; Zhang, Bin; Chen, Lei; Cao, Zhihui; Shi, Pengfei; Liu, Jinwei; Zhang, Junyan; Qian, Linmao

doi:10.3390/coatings8100331

Cited by 14 publications

(6 citation statements)

References 40 publications

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“…Thus, its contribution to the sharp drop in friction during the running-in process can be ruled out. Similar phenomena were reported in other studies [31,32,33].…”

Section: Discussionsupporting

confidence: 92%

Key Role of Transfer Layer in Load Dependence of Friction on Hydrogenated Diamond-Like Carbon Films in Humid Air and Vacuum

et al. 2019

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The friction of hydrogenated diamond-like carbon (H-DLC) films was evaluated under the controlled environments of humid air and vacuum by varying the applied load. In humid air, there is a threshold applied load below which no obvious friction drop occurs and above which the friction decreases to a relatively low level following the running-in process. By contrast, superlubricity can be realized at low applied loads but easily fails at high applied loads under vacuum conditions. Further analysis indicates that the graphitization of the sliding H-DLC surface has a negligible contribution to the sharp drop of friction during the running-in process under both humid air and vacuum conditions. The low friction in humid air and the superlow friction in vacuum are mainly attributed to the formation and stability of the transfer layer on the counterface, which depend on the load and surrounding environment. These results can help us understand the low-friction mechanism of H-DLC film and define optimized working conditions in practical applications, in which the transfer layer can be maintained for a long time under low applied load conditions in vacuum, whereas a high load can benefit the formation of the transfer layer in humid air.

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“…Thus, its contribution to the sharp drop in friction during the running-in process can be ruled out. Similar phenomena were reported in other studies [31,32,33].…”

Section: Discussionsupporting

confidence: 92%

Key Role of Transfer Layer in Load Dependence of Friction on Hydrogenated Diamond-Like Carbon Films in Humid Air and Vacuum

et al. 2019

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“…Comparisons of friction coefficient values have to be made with caution, since environmental and test conditions, especially humidity [43], temperature [44], sliding velocity [45], load [46] and material of the counter face [47,48], influence the absolute value of the friction coefficient [49]. Concentrating on literature values from near-identical experiments, values of 0.1 or somewhat below are commonly found for a-C:H films prepared by PSII [50], whereas values of 0.05 are usually only achieved when dopants are added [51].…”

Section: Discussionmentioning

confidence: 99%

The Influence of Preparation Conditions on the Structural Properties and Hardness of Diamond-Like Carbon Films, Prepared by Plasma Source Ion Implantation

et al. 2020

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Diamond-like carbon (DLC) films were prepared from a hydrocarbon precursor gas by plasma source ion implantation (PSII), in which the plasma generation and the film deposition were coupled; i.e., the plasma was generated by the applied voltage and no additional plasma source was used. Several experimental parameters of the PSII process were varied, including the sample bias (high voltage, DC or pulsed), gas pressure, sample holder type and addition of argon in the plasma gas. The influence of the deposition conditions on the carbon bonding and the hydrogen content of the films was then determined using Raman spectroscopy. Nanoindentation was used to determine the hardness of the samples, and a ball-on-disk test to investigate the friction coefficient. Results suggest that films with a lower sp2 content have both a higher hydrogen content and a higher hardness. This counterintuitive finding demonstrated that the carbon bonding is more important to hardness than the reported hydrogen concentration. The highest hardness obtained was 22.4 GPa. With the exception of a few films prepared using a pulsed voltage, all conditions gave DLC films having similarly low friction coefficients, down to 0.049.

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“…During the running-in of the H-DLC film, either the graphitization of the strained material or the removal of the oxide layer may change the surface properties of the substrate [12]. However, Tambe and Bhushan [34] indicated that the graphitization of H-DLC film may not occur at low sliding speed (< 400 μm/s) in the nanoscale wear tests.…”

Section: Role Of the Oxide Layer Removal In The Runningin Processmentioning

confidence: 99%

“…As an unavoidable phenomenon for most as-fabricated mechanical parts during the initial operation, runningin alters the performance of the moving components and plays a crucial role at all size scales, from macroscale engines down to dynamic nano-devices [1][2][3][4][5][6][7][8]. Diamond-like carbon (DLC) film is one of the most promising materials for reducing energy consumption and CO2 emission since it is capable of achieving super-low friction for sliding parts [9][10][11][12]. Except for a few specially treated DLC films, such as those with a pre-existing highly graphitized surface [8,13], most kinds of DLC films must initially undergo a transition to lower the friction level.…”

Section: Introductionmentioning

confidence: 99%

Running-in behavior of a H-DLC/Al2O3 pair at the nanoscale

et al. 2020

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Diamond-like carbon (DLC) film has been developed as an extremely effective lubricant to reduce energy dissipation; however, most films should undergo running-in to achieve a super-low friction state. In this study, the running-in behaviors of an H-DLC/Al2O3 pair were investigated through a controllable single-asperity contact study using an atomic force microscope. This study presents direct evidence that illustrates the role of transfer layer formation and oxide layer removal in the friction reduction during running-in. After 200 sliding cycles, a thin transfer layer was formed on the Al2O3 tip. Compared with a clean tip, this modified tip showed a significantly lower adhesion force and friction force on the original H-DLC film, which confirmed the contribution of the transfer layer formation in the friction reduction during running-in. It was also found that the friction coefficient of the H-DLC/Al2O3 pair decreased linearly as the oxygen concentration of the H-DLC substrate surface decreased. This phenomenon can be explained by a change in the contact surface from an oxygen termination with strong hydrogen bond interactions to a hydrogen termination with weak van der Waals interactions. These results provide new insights that quantitatively reveal the running-in mechanism at the nanoscale, which may help with the design optimization of DLC films for different environmental applications.

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Perspectives of the Friction Mechanism of Hydrogenated Diamond-Like Carbon Film in Air by Varying Sliding Velocity

Cited by 14 publications

References 40 publications

Key Role of Transfer Layer in Load Dependence of Friction on Hydrogenated Diamond-Like Carbon Films in Humid Air and Vacuum

Key Role of Transfer Layer in Load Dependence of Friction on Hydrogenated Diamond-Like Carbon Films in Humid Air and Vacuum

The Influence of Preparation Conditions on the Structural Properties and Hardness of Diamond-Like Carbon Films, Prepared by Plasma Source Ion Implantation

Running-in behavior of a H-DLC/Al2O3 pair at the nanoscale

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