Research Papers: Tribochemistry & Tribofilms

Formation and Characterization of Tribofilms

[+] Author and Article Information
Prasenjit Kar1

Department of Materials Science and Engineering, Texas A&M University, College Station, TX 77843-3123rajkar2006@gmail.com

Pranay Asthana2

Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843-3123

Hong Liang3

Department of Materials Science and Engineering, and Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843-3123hliang@tamu.edu


Present address: Chevron, Richmond, CA.


Present address: WellDynamics, Inc., TX.


Corresponding author.

J. Tribol 130(4), 042301 (Aug 04, 2008) (6 pages) doi:10.1115/1.2958071 History: Received August 12, 2007; Published August 04, 2008

Fundamentals of tribofilm formation and their properties were studied. In order to understand the effects of lubricants on tribofilms, four base oils were investigated. Lubricants include castor oil, polyethylene glycol, mineral oil, and margarine. These oils were chosen based on their molecular structure, polarity, utility, and biodegradability. Experiments were conducted using a ball-on-disk tribometer to form tribofilms. Surface characterization was carried out using a stylus profilometer, a scanning electron microscope, and a transmission electron microscope. Results showed that oils with high polarity such as castor oil enhanced the formation of a transfer layer on the steel surface, whereas nonpolar oils such as mineral oil failed to do so. Oils with high polarity act as effective base oils to prevent metal hardening and bond debris particles to the metal surface. Oils with nonpolar components, on the other hand, generate abrasive nanoparticles during rubbing. Experiments with margarine at elevated temperature resulted in the formation of a hard and thick tribofilm. An adsorption model is illustrated to highlight the effects of lubricant molecules.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Molecular structure of lubricants

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Figure 2

Schematic of ball-on-disk tester

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Figure 3

Summary of the average friction coefficient. The top portion is the error bar.

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Figure 4

SEM pictures of wear tracks

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Figure 5

Surface roughness of tribofilms

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Figure 6

SEM image of the cross section of the tribofilm

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Figure 7

Microindentation of the tribofilm

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Figure 8

TEM analysis of the tribofilm showing nano- and amorphous structures

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Figure 9

TEM image of wear particles: (a) particles obtained through mineral oil and (b) particles obtained through castor oil

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Figure 10

Illustration of the interaction between the molecules and the steel surface




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