Research Papers: Friction & Wear

Tribological Investigation of Nanographite Platelets as Additive in Anti-Wear Lubricant: A Top-Down Approach

[+] Author and Article Information
Flavio A. C. Vidal

Product Research and Development Center,
Fiat Chrysler Group,
Av. Contorno, 3455,
Betim 32501-970, Brazil
e-mail: flavio.vidal@fiat.com.br

Antonio F. Ávila

Mechanical Engineering Department,
Universidade Federal de Minas Gerais,
Av. Presidente Antônio Carlos, 6627,
Belo Horizonte 31270-910, Brazil
e-mail: aavila@netuno.lcc.ufmg.br

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received December 26, 2013; final manuscript received April 14, 2014; published online May 7, 2014. Assoc. Editor: Dae-Eun Kim.

J. Tribol 136(3), 031603 (May 07, 2014) (9 pages) Paper No: TRIB-13-1260; doi: 10.1115/1.4027479 History: Received December 26, 2013; Revised April 14, 2014

A top-down approach is employed to investigate the tribological effect of adding nanographite platelets (NGPs) to mineral base oil (MBO). The performance of the NGP-modified MBO was evaluated by examining the friction and anti-wear properties. Four different types of NGPs produced by two different processes were employed. The optimal NGP-modified MBO attained a significant wear and friction reduction when compared with the MBO without NGPs. The process used to exfoliate the graphite nanoplatelet samples provided better wear properties because of the graphene layers' smoother sliding mechanism. Graphene layers seeped inside the groove marks to keep the friction coefficient low.

Copyright © 2014 by ASME
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Fig. 1

SEM images of nanographite platelets (a) NGP-1 (d50 = 9.88 μm); (b) NGP-2 (d50 = 27.53 μm); (c) NGP-3 (d50 = 52.11 μm); and (d) NGP-4 (d50 = 2.60 μm)

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Fig. 2

Typical EDX analysis for all four NGPs

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Fig. 3

TEM images of nanographite platelets (a) typical TEM image of NGP-1, NGP-2, and NGP-3 with a graphene platelet thickness of about 10–20 nm and (b) image of NGP-4 with a graphene platelet thickness of about 20–30 nm

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Fig. 4

Typical TGA curves of NGPs at heating rate 10 °C/min in N2 atmosphere

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Fig. 5

Comparison of NGPs' XRD Bragg peak at 2θ 26.5 deg, confirming morphological differences between NGP-4 and other NGPs, due to its distinct manufacturing processes

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Fig. 6

WSD depending on the percentage and type of nanographite (four-ball, 1200 rpm, 147 N, 60 min, 75 ± 2 °C)

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Fig. 7

WSD for NGP-4 and NGP-4-EX depending on the percentage of nanographite (four-ball, 1200 rpm, 147 N, 60 min, 75 ± 2 °C)

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Fig. 8

WSD of steel balls using after four-ball experiments (a) MBO, (b) NGP-4-EX with 0.25 wt. %, and (c) NGP-1 with 0.25 wt. %

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Fig. 9

WSD as a function of time for MBO and NGP-4-EX with 0.25 wt. % (four-ball, 1200 rpm, 147 N, 75 ± 2 °C)

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Fig. 10

Friction coefficent for NGP-4 with 0.25 wt. %, NGP-4-EX with 0.25 wt. % and MBO (four-ball, 1200 rpm, 147 N, 75 ± 2 °C)

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Fig. 11

SEM images of worn steel balls after four-ball wear experiments: (a, b) using MBO; (c, d) using NGP-4-EX with 0.25 wt. %

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Fig. 12

Images of worn steel balls after four-ball wear experiments (a) mineral oil with 0.25 wt. % NGP-4-EX and (b) 0.25 wt. % NGP-4-EX on the surface of wear track

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Fig. 13

EDX analysis of worn steel balls (a) using MBO and (b) using 0.25 wt. % NGP-4-EX confirming the presence of carbon on the worn steel balls' surface

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Fig. 14

Raman spectroscopy of NGP-4-EX




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