Characterization and optimization of influence of MoS2 hybridization on tribological behaviours of Mg–B4C composites

Abstract

Aerospace and automobile industries are facing challenges in developing lightweight materials with high corrosion and wear resistance. The magnesium (Mg) alloys are superior to their monolithics, as they have maximum strength-to-weight ratio. These challenges can be solved with application of Mg-based hybrid composites. Therefore, this study investigated the hybridizing effect of molybdenum disulphide (MoS2) reinforcement on tribological performance of magnesium–boron carbide (Mg–B4C) hybrid composites, fabricated by powder metallurgy technique. Wear tests under dry sliding condition were carried out on the prepared composite samples with different proportions/weight percentage (wt%), using a pin-on-disc apparatus. Mg, MoS2, B4C and their various composites were characterized, using X-ray diffraction, thermogravimetric analysis, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy analysis. The experiments were conducted using L27 orthogonal array with five factors at three levels that affected the tribological performance. The wear resistance of the hybrid Mg–B4C–MoS2 composites significantly increased when compared with Mg–B4C and Mg–MoS2 composites, due to the refined effect of both reinforcements. Analysis of variance and grey-relational analysis result showed that increase in MoS2, sliding distance (DSl) and load (LSl) significantly influenced the tribological performance of the hybrid composites. Mg–10wt%B4C–5wt%MoS2 exhibited significant best improvement on the multi-response tribological performance. The optimum quantity of MoS2 reinforcement was around 7 wt%. Beyond this threshold proportion, wear was significantly increased, due to the agglomeration of MoS2 particles. Hardness of the composites increased with hybridized reinforcements. SEM micrographs depicted the homogeneous dispersion of reinforcements in the Mg matrix. Also, SEM micrographs of the worn surfaces confirmed that delamination wear mechanism was dominant on the Mg hybrid composites.