Dry sliding wear behavior of ultrasonic stir cast boron carbide reinforced aluminium nanocomposites

Abstract

In the present work ultrasonic stir casting method is used to fabricate aluminium metal matrix nanocomposites reinforced with nano boron carbide (nB4C) particles with varying (0.5, 1, 1.5 and 2) weight percentages. Microhardness and nanoindentaion hardness of the nanocomposite is found to increase with increasing reinforcement content. Pin on disk apparatus is used to study the room temperature dry sliding wear behavior of fabricated composites and base alloy. Nominal contact pressures of 0.354–1.412 MPa and sliding speeds of 0.16–0.66 m s−1 are employed. Each test run is conducted for the fixed contact period of 15 min. Field emission scanning electron microscopy (FESEM) equipped with energy dispersive spectroscopy (EDS) is used to observe worn surface and wear debris to understand the undergoing wear mechanisms. It is observed that base alloy underwent mild to severe plastic deformation led oxidative delamination wear. Nanocomposites are subjected to combination of oxidative, abrasive and mild delamination wear. Nanocomposites display less mass loss and wear rate as compared to base alloy due to the protective tribolayer formed in the contact interface. Part of the mechanically mixed transfer layer is found to adhere firmly to the composite surface under higher load-speed condition. Extremely hard nB4C particle reinforcement is found beneficial for improving the wear resistance of aluminium alloy at varying combinations of load and speed.