Tribological behavior of hybrid aluminum self-lubricating composites under dry sliding conditions at elevated temperature

Abstract

ABSTRACT In this study, the influence of n-Al2O3 (aluminum oxide) and graphene nanoplatelet (GNP) on the tribological properties of a eutectic Al–Si (aluminum silicon) alloy was investigated. For Al–Si/n-Al2O3 (advanced composite), the coefficient of friction (COF) decreased by 34.41% and the wear resistance enhanced by 43.75% compared with base matrix alloys under high temperature (HT) conditions. For Al–Si/n-Al2O3/GNP (hybrid composite), COF decreased by 61.41% and the wear resistance improved by 96.87% at HT compared with base matrixes (eutectic Al–Si alloy). This finding was attributed to enhanced lubrication through GNP, glazed layer, thin tribooxide film (TTL) and mechanical mixed layer (MML) present on wear scars. Melt wear caused by scuffing was the main wear mechanism for the base composition at 300 and 400°C, and adhesion abrasion, crack formation and delamination pits were the wear mechanisms observed for the advanced and hybrid composites at extreme temperature conditions. Highlights Al–Si/ n-Al2O3 and Al–Si/ n-Al2O3/GNP composites were fabricated through spark plasma sintering. The tribological performance of the fabricated composite samples was investigated under dry sliding at elevated operating temperatures (100–400°C). The coefficient of friction and wear resistance improved with an increase in the secondary GNP reinforcement. Transition in the wear regime occurred at approximately 0.8 of melting temperature. The self-lubrication mechanism of GNP was observed on the wear track, which significantly reduced scar surface roughness.