Wear Behavior of Hypereutectic Al-18Si Composites Under Linear Reciprocating Sliding

Abstract

Aluminum and its alloys are widely used due to their good characteristics like low density, non-ferromagnetism, resistance to corrosion, high electrical and thermal conductivity, non-flammability, non-toxicity, and others. Hypereutectic Al-Si alloys are finding their application for pistons, due to their good thermal conductivity, high strength-to-weight ratio and good corrosion resistance. Since pistons are operating under high loads there is a need for improvement of their mechanical and tribological characteristics. Mechanical and tribological characteristics and microstructure of composites depend on the fabrication methods and size of reinforcement particles. The investigation of mechanical and tribological properties of hypereutectic Al-18Si based composites was done on composites particulate reinforced with 0.5 wt.% Al2O3 (approx. Size 20–30 nm), 10 wt.% SiC (approx. Size 30 μm) and 1 wt.% Gr (approx. Size 17 μm). Tribological tests were done on apparatus with reciprocating linear motion in lubricated sliding conditions, at a sliding speed of 0.5 m/s, sliding distance of 1000 m and normal loads of 100, 200 and 300 N. Hardness of composites decreased with the addition of reinforcements and intermetallic phases and large primary Si particles were present in the microstructure. The increase in normal load increased wear while the coefficient of friction decreased with the increase in normal load. This study shows the potential of hypereutectic Al-18Si based composites reinforced with nano Al2O3, and micro SiC and Gr particles to be used for highly loaded pistons since the composites showed improved mechanical and tribological properties over the base alloy.