Tribological functionality of aluminium sliding materials with hard phases under lubricated conditions

This paper describes the tribological functionality of hypereutectic AlSi under conformal contact conditions. Temperature and load bearing tests were performed with a ring-on-disc configuration with steel counterparts under fully formulated engine oil. Tribometric tests show significantly higher wear resistance and loadability of AlSi compared to pure Al. Post test surface characterization by light and electron microscopy revealed the load bearing functionality of the Si hard phases. Selective formation of protective tribofilms was observed exclusively on these Si particles and on the corresponding steel counterpart. This formation requires sufficient energy input and only takes place under harsh contact conditions. ► Evaluation of tribological functionality of AlSi in lubricated ring-on-disc tests. ► Hard phases (Si and Al2Cu) form a load bearing particle structured surface. ► Protective tribofilms (rich in P, O, Zn, S) form exclusively on Si, Al2Cu and steel. ► Tribofilms are only generated under harsh local contact conditions. ► Friction modifiers can change fracturing process of Si-hard phases.