Determination of wear resistance ratio between A356–B4C and A356–B4C + graphite hybrid composites

This study investigates the tribological behavior of A356 aluminum alloy reinforced with boron carbide (B4C) and hybridized with graphite (Gr) to enhance wear resistance under varying operating conditions. The composites were fabricated using the stir casting technique with reinforcement contents ranging from 0 to 10 wt.%. Experimental results demonstrate that A356–B4C + Gr hybrid composites exhibit significantly lower wear rates than single-reinforced A356–B4C composites, particularly at higher reinforcement levels. The wear rate decreased from 0.0062 mm³/min for unreinforced A356 to 0.0020 mm³/min for the hybrid composite, corresponding to an approximate 68% reduction under standard test conditions. Analysis of variance identified temperature and reinforcement percentage as the most influential parameters governing wear behavior, followed by applied load and sliding velocity. At elevated temperatures (100°C–200°C), the combined effects of tribo-oxide layer formation and graphite-induced self-lubrication contributed to wear stabilization, while excessive thermal exposure led to matrix softening and reinforcement pull-out. Scanning electron microscopy and energy-dispersive X-ray spectroscopy analyses revealed a transition from abrasive to adhesive and oxidative wear mechanisms, with hybrid composites showing improved surface stability and reduced friction. An optimal reinforcement ratio of B4C to graphite (R1/R2 = 0.7, where R1 and R2 denote B4C and Gr contents, respectively) was identified, highlighting the suitability of A356–B4C + Gr hybrid composites for high-performance tribological applications.