FORMATION OF CYLINDRICAL SLIDING-WEAR DEBRIS ON SILICON IN HUMID CONDITIONS AND ELEVATED-TEMPERATURES

The present study investigates the mechanics of roll formation between sliding bodies at elevated temperatures and humid conditions. Silicon is used as the model material for reciprocating linear sliding tests. The evolution of tribological rolls initially involves the rapid oxid ation of silicon wear debris by water, the deformation of SiO2 particl es into platelets, and then the compaction of these particles into a f ilm deposited on the wear surface. The formation of compacted silica f ilm requires minimum adsorption of water which enhances the adhesion b etween silica platelets. The stress cycle imposed on the film leads to the delamination of platelets near the sliding surface. The delaminat ed debris cluster into multiple aggregates that are subsequently rolle d into dense cylindrical particles so as to relieve the interfacial sh ear stress. When the film and rolls are formed, the friction and wear rate is maintained at low steady state values.