Abstract
In this study, nickel matrix composites reinforced by carbon nanotubes (CNTs) are compared to unreinforced CNT-coated (by drop-casting) bulk nickel samples in terms of their friction and wear behavior, thus gaining significant knowledge regarding the tribological influence of CNTs and the underlying tribo-mechanism. It has been shown that the frictional behavior is mainly influenced by the CNTs present in the contact zone, as just minor differences in the coefficient of friction between the examined samples can be observed during run-in. Consequently, the known effect of a refined microstructure, thus leading to an increased hardness of the CNT reinforced samples, seems to play a minor role in friction reduction compared to the solid lubrication effect induced by the CNTs. Additionally, a continuous supply of CNTs to the tribo-contact can be considered isolated for the reinforced composites, which provides a long-term friction reduction compared to the CNT-coated sample. Finally, it can be stated that CNTs can withstand the accumulated stress retaining to some extent their structural state for the given strain. A comprehensive study performed by complementary analytical methods is employed, including Raman spectroscopy and scanning electron microscopy to understand the involved friction and wear mechanisms.
Highlights
In recent years, carbon nanotubes (CNTs) have been receiving a lot of attention in the research community due to their outstanding intrinsic physical properties, mechanical [1] and thermal [2]
The different sample sets were first compared in terms of the temporal evolution of the coefficient of friction (COF) using a ball-on-disk tribometer under linear reciprocating motion and an Al2 O3 ball as counter body
It can be stated that the frictional behavior is mainly influenced by the CNTs present in the contact zone, as no difference in the COF between both samples can be observed
Summary
Carbon nanotubes (CNTs) have been receiving a lot of attention in the research community due to their outstanding intrinsic physical properties, mechanical [1] and thermal [2]. Several studies have proved the ability of CNTs to reduce friction and wear; for example, when used as the reinforcement phase in composites [3,4,5,6,7,8,9], as a protective film [10,11,12,13], solid lubricant [8,9,10,12,14,15], or lubricant additive [16,17,18,19] All of these systems show improvements to a different extent, the tribo-mechanisms inducing these effects are clearly differing and not completely understood. Differences in the tribological behavior can be traced back more as a function of the purpose of use
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