Influence of wear particle interaction in the sliding interface on friction of metals

The role of wear particles at the sliding interface on the frictional behavior of metals was investigated with respect to size and agglomeration characteristics using both pin-on-disk and pin-on-reciprocator tribotesters. The wear particle interaction at the sliding interface was monitored using a CCD camera. It was found that the friction coefficient significantly rises once a wear particle is produced and trapped at the interface. Wear particles of soft, ductile metal pairs go through a cycle of agglomeration and breakup, while wear particles of hard material pairs are less likely to agglomerate. The wear particles were smaller for the bidirectional sliding motion compared with those in the unidirectional sliding motion, which resulted in lower friction and wear characteristics. This difference is attributed to the higher probability of particle breakup in bidirectional sliding motion. The frictional behavior was also investigated when metal particles are introduced into the interface of Cu-Cu sliding pair. The friction coefficient increased with the introduction of Ni powder whereas it decreased with the introduction of Al powder. It is concluded from these results that frictional behavior could be altered at will by inserting appropriate particles into the sliding interface.