Tracing single asperity wear in relation to macroscale friction during running-in

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.