In situ tribometry of solid lubricant nanocomposite coatings

Chromik, Richard R.; Baker, Colin; Voevodin, Andrey A.; Wahl, Kathryn J.

doi:10.1016/j.wear.2007.01.001

Cited by 67 publications

(58 citation statements)

References 29 publications

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“…For example, the friction coefficients obtained on boric acid coatings [22,25] rose from 0.1 to [0.7 with the loss of a boric acid transfer film. Similar behavior has also been observed with several nanocomposite coatings when the transfer film failed [28].…”

Section: Discussionsupporting

confidence: 83%

“…They inferred that the relatively high friction coefficients with ceramic pins during run-in might have been due to the difficulty of forming a continuous transfer film, a process that accompanied the rapid drop in the friction coefficient obtained with steel pins. The NRL group used an in situ tribometer to provide direct evidence that the drop in the friction coefficient during run-in correlated with the buildup of transfer films on the stationary pin [13,[22][23][24][25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

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Role of the Transfer Film on the Friction and Wear of Metal Carbide Reinforced Amorphous Carbon Coatings During Run-in

Scharf¹,

Singer

2009

Tribol Lett

112

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The relationship between friction, wear, and transfer films of three metal carbide-reinforced amorphous carbon coatings (TiC/a:C, TiC/a:C-H, and WC/a:C-H), sometimes referred to as metal-doped diamond-like carbon coatings, has been investigated. Tribological tests were performed in an in situ tribometer with sapphire or steel hemispheres run against coated flats in dry or ambient air. The sliding contact interface was observed and recorded by optical microscopy during reciprocating sliding tests. The friction and wear behavior during run-in depended on the number of sliding cycles to form a stationary transfer film on the hemisphere. Stationary transfer films formed rapidly (within ten cycles) and the friction coefficient fell to 0.2 (ambient air) or 0.1 (dry air), except with sapphire against WC/a:C-H in dry air; with the latter, a stationary transfer film required nearly 100 cycles to form, during which the friction remained high and the wear rate was from 10 to 100 times higher than the other two coatings. For all coatings, three velocity accommodation modes (VAM) were observed from run-in to steady-state sliding and were correlated with the friction and wear behavior. The delayed adherence of the transfer film to sapphire from WC/a:C-H coatings in dry air is discussed in terms of equilibrium thermochemistry. Friction and wear behavior during run-in, therefore, depended on transfer film adherence to the hemisphere and the VAM between transfer films and the coating.

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Section: Discussionsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Role of the Transfer Film on the Friction and Wear of Metal Carbide Reinforced Amorphous Carbon Coatings During Run-in

Scharf¹,

Singer

2009

Tribol Lett

112

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“…The change of Newton's ring diameter during sliding test can be observed and measured from the images. The use of Newton's ring to quantify transfer layer thickness is given in [5,6]. Pythagoras theorem was used to estimate transfer layer thickness, as in Eq.…”

Section: Estimation Of the Thickness Of Transfer Layermentioning

confidence: 99%

Effect of Transfer Layer on Ultra Low Friction of CNx Coating under Blowing Dry Ar

et al. 2013

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In order to clarify the ultra low friction mechanism of Carbon Nitride (CN x ) coatings under blowing dry Ar, thickness and area of transfer layers on mating surface were in-situ observed with an optical microscope during sliding against a sapphire hemisphere under blowing dry Ar. During sliding, thickness of transfer layer from CN x coating to a sapphire hemisphere increased and leaded to ultra low friction. When thickness and area of transfer layer was thick and small respectively, ultra low friction was observed. The result showed that the coefficient of friction decreased from 0.18 to 0.003 and remained constant throughout the friction test. It was confirmed the formation of a graphite-like transfer layer with Raman analysis and Auger Electron Spectroscopy (AES).

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“…In situ tribometry techniques can add to our understanding of how these changes impact tribological response of solid lubricants [27][28][29][30][31][32][33]. In our laboratory, we have implemented optical in situ tribometry to examine the third bodies formed in the contact and how their morphology, motion, and properties impact friction, wear and endurance [33][34][35][36][37][38]. These various optical in situ studies of boric acid [33], Pb-Mo-S, diamond-like carbon [34][35][36], MoS 2 [38,39], and nanocomposite [37] solid lubricants have given direct evidence for the role of the third body in friction behavior [38].…”

Section: Introductionmentioning

confidence: 99%

In Situ Analysis of Third Body Contributions to Sliding Friction of a Pb–Mo–S Coating in Dry and Humid Air

2007

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Reciprocating sliding tests of ion-beam deposited (IBD) Pb-Mo-S coatings were performed with an in situ tribometer that allows real-time visualization and Raman analysis of the sliding contact through a transparent hemisphere. Experiments were performed in dry air, ambient air (*50% RH) and mixtures of dry and humid air cycled between low and high humidity. Third bodies formed in the sliding contact were monitored through an optical microscope and analyzed by Raman Spectroscopy. Third body velocity accommodation modes were identified and correlated with friction behavior in dry and ambient air. The dominant velocity accommodation mode in both dry and humid air was interfacial sliding between the outer surface of the transfer film and the wear track; this interface, based on present and earlier studies, is crystalline MoS 2 . Therefore, the friction coefficient was controlled by the interfacial shear strength of MoS 2 sliding against MoS 2 . Humid air sliding was accompanied by a rise in the friction coefficient and a small but observable second velocity accommodation mode: shear/extrusion of the transfer film. It is concluded that the friction rise in humid air was due to an increase in the interfacial shear strength, and that the rise in friction caused the third body to deform rather than the deformation causing the friction to rise.

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In situ tribometry of solid lubricant nanocomposite coatings

Cited by 67 publications

References 29 publications

Role of the Transfer Film on the Friction and Wear of Metal Carbide Reinforced Amorphous Carbon Coatings During Run-in

Role of the Transfer Film on the Friction and Wear of Metal Carbide Reinforced Amorphous Carbon Coatings During Run-in

Effect of Transfer Layer on Ultra Low Friction of CNx Coating under Blowing Dry Ar

In Situ Analysis of Third Body Contributions to Sliding Friction of a Pb–Mo–S Coating in Dry and Humid Air

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