Abstract
The running-in wear of a multi-asperity silicon carbide sphere-on-silicon flat interface is investigated at the micro- and nanoscale in relation to the friction behaviour of an unlubricated macroscale tribological system sliding in a unidirectional mode. Experiments and contact simulations indicated that the macroscale friction behaviour during running-in was governed by the wear behaviour of roughness asperities on the sphere and their influence on the interfacial contact pressure. Specific ploughing tracks on the flat corresponded to individual asperities on the sphere which, when worn-off, led to lower, more stable friction behaviour and mild wear at an atomic attrition-like rate. It was also found that single asperity contact simulations are unable to reliably predict multi-asperity friction and wear behaviour for this system.
Highlights
Friction and wear of macroscopic dry sliding contacts are known to have a substantial detrimental impact upon the global energy consumption, economy and environment.[1,2] As a consequence, this has sparked significant scientific interest, with the aim to manipulate and reduce friction and wear of materials under conditions of industrial relevance.[3,4,5,6] Friction and wear behaviour at the macroscopic length scale is typically influenced by the topography of the contacting surfaces.[7]
It is unsurprising that the l running-in process is poorly understood. a In order to simplify the tribological system, fundamental studies into the isolated friction rn and wear events occurring at a single asperity during the onset of dry sliding have attracted considerable attention, with the intention to collectively transform the outcomes into ‘multiu asperity’ level behaviour at the macroscale.[7,8,9,10,11,12,13,14,15,16]
The running-in friction behaviour of the single asperity tribological systems studied by Bhaskaran et al.[12] and Gotsmann et al.[13] were characteristic of a dry sliding system where a small amount of surface contamination, oxide or adsorbed species at the interface is quickly worn away to cause a greater degree of adhesion and a rise in friction.[9]
Summary
Friction and wear of macroscopic dry sliding contacts are known to have a substantial detrimental impact upon the global energy consumption, economy and environment.[1,2] As a consequence, this has sparked significant scientific interest, with the aim to manipulate and reduce friction and wear of materials under conditions of industrial relevance.[3,4,5,6] Friction and wear behaviour at the macroscopic length scale is typically influenced by the topography of the contacting surfaces.[7]. The choice to apply a ‘unidirectional’ sliding mode, f where the silicon carbide sphere always encounters a pristine silicon surface throughout the o sliding measurement, aims to trace the evolution of the asperity friction and wear whilst minimising the formation of third bodies. The latter are known to influence the friction and ro wear behaviour of this type of tribological system.[27] e-p 2. The same cleaning procedure was used for removal of wear debris as indicated
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