Evaluation of Mechanical Properties and Tribological Behaviour of Self-lubricating Aluminium Matrix Hybrid Composites

Abstract

In the present investigation, aluminium matrix-based hybrid composites are developed with the following set of combinations such as n-Al₂O₃ (2 wt%), n-Al₂O₃/MoS₂ (2 wt% each), n-Al₂O₃/WS₂ (2 wt% each), n-Al₂O₃/MoS₂/WS₂ (2%, 1%, 1%, respectively) by using simple and cost-effective stir casting route. Through this study, the self-lubricating aspects of the developed hybrid composites were ascertained. Microstructure and particulate distribution were studied using optical microscope and scanning electron microscope. XRD analysis was used to test the phase present and possible interaction of powders with aluminium matrix. Tensile specimens were made according to ASTM E8 standard and tested on Instron tensile testing machine. Vicker’s micro-hardness was tested by applying a load of 50 kgf for a dwell period of 15 s. Dry sliding wear tests were performed on pin-on-disc tribometer at room temperature using 8 mm diameter and height of 35 mm cylindrical pin samples with a rotating circular disc made of EN31 as counter material at constant sliding speed of 0.5 m/s and at different normal loads of 10, 20, 30 and 40 N. Worn surfaces after dry sliding wear were then analysed under SEM for possible wear mechanism. Results have shown improved density, micro-hardness and ultimate tensile strength of composites. Wear rate and coefficient of friction are observed to decrease with addition of solid lubricants (MoS₂ and WS₂). The improved wear performance is attributed to high hardness of cast composites and formation of low shear strength tribofilm at the interface.