Effect of elevated temperatures and applied pressure on the tribological properties of LM30/sillimanite aluminium alloy composites

Abstract

The present study focuses on the development of low-cost, lightweight and highly wear resistant composites for brake rotor applications. Sillimanite mineral reinforced aluminum matrix composites were stir cast using three distinct reinforcement particle sizes. Reinforcement level was varied in the range of 3–15 wt%. The influence of operating temperature (50℃–300℃) and applied pressure (0.2–1.0 MPa) on the wear/friction behaviour of composites was observed. Optical micrographs showed homogenous particle distribution throughout the matrix. The high nanohardness obtained for interface regions signifies good particle–matrix bonding of processed composites. Dilatometry studies showed that the increase in sillimanite content decreased the coefficient of thermal expansion of the composites. Maximum improvement of 33% in coefficient of thermal expansion (over base alloy) was observed for 15 wt% fine composites. Wear analysis revealed that the developed composites provided adequate wear resistance till an operating temperature of 200℃, beyond which wear rate increased significantly. For the high operating temperature of 200℃, the steady-state wear of composites was comparable (only 6.62% higher) to the commercial cast iron alloy used in brake rotor applications. The aluminium-based composites developed in the present research are low cost (sillimanite is a naturally occurring mineral sand) and lightweight (60% lighter than cast iron) and can be used as an alternate material for brake rotors in light vehicles. Finally, SEM of worn out surfaces divulged the dominance of adhesive wear for material removal.