Page 189 - Handbook of Surface Improvement and Modification

184 The Coefficient of Friction

nanoparticles affected wear and the coefficient of friction, primarily by affecting their
macroscopic hardness and the thickness and the surface coverage of their transfer films. 30
The tungsten disulfide-based nanoparticles outperformed the carbon-based nanoparticles
in terms of wear performance. Fullerene-like tungsten disulfide improved the wear rate by
10% and the needle-like tungsten disulfide by 60%. Carbon nanotubes deteriorated the
30
wear behavior by 20% and graphene nanopowder by as much as three times. Figure
30
11.26 shows images of fractured nanocomposites containing various fillers. Coefficient
of friction was reduced by fullerene-like tungsten disulfide and carbon nanotubes by about
30
30%. The needle-like tungsten disulfide increased the coefficient of friction of poly-
etheretherketone by 25% and graphene had very little impact on coefficient of friction. 30
30
Interesting to note that the coefficient of friction and the wear rate do not correlate.
The effect of nanofillers on friction and wear behavior is a subject of a book chap-
31
ter. Analysis of various systems leads to similar observation as expressed above that a
lower coefficient of friction does not necessarily correspond to a decreased wear rate. 31
Addition of nanofillers in majority of cases reduced coefficient of friction and wear rate. 31
Particle size of nanofillers has more pronounced effect on coefficient of friction that on

Figurer 11.27. (a) Top-view SEM image of PI film with flat and smooth surface; (b) side-view SEM image of PI
film showing the integrated structure; (c) top-view SEM image of composite film with well-dispersed La 2 O 3
microparticles on surface; (d) side-view SEM image of composite film with well-dispersed La 2 O 3 microparticles
resulting in a layered structure. [Adapted, by permission, from Pan, Z; Wang, T; Chen, L; Idziak, S; Huang, Z,
Appl. Surf. Sci., 416, 536-46, 2017.]