Effect of reinforcement in the fabrication of ZA-27 composites with hexagonal boron nitride (HBN) and graphite (Gr) nanoparticles through stir casting

Zinc aluminium alloy is widely used for bearing and load-bearing applications owing to its good castability, high strength and cost effectiveness; however, its wear resistance and frictional stability under higher loads remain a concern. While, individual reinforcement has not achieved an overall improvement in tribological performance of composites. The present study investigates the fabrication of ZA-27-based composites reinforced with hexagonal boron nitride (hBN) and graphite (Gr) nanoparticles using stir casting followed by ultrasonic treatment. The composites were reinforced with a fixed content of 2 wt.% hBN and varying proportions of Gr particles at 2, 4 and 6 wt.%. The dry sliding wear behaviour was examined using a pin-on-disc tribometer under applied loads ranging from 10 to 30 N. The outcomes demonstrated that the wear rate decreases with increasing reinforcement content. Compared to unreinforced alloy, volumetric wear loss of composites decreased by 13.80%, 22.23% and 46.26% for 2, 4 and 6 wt.% Gr reinforcement, respectively, at a load of 30 N. Energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analyses confirmed the composition and phase stability of composites, while scanning electron microscopy (SEM) shown a uniform distribution of reinforcement particles. Worn surface analysis showed deep grooves and delamination in the matrix alloy, whereas the composites exhibited finer scratches due to the formation of a lubricating tribo-film. This investigation may serve as a reference for the development of ZA-27/hBN/Gr composites for advanced industrial tribological applications (such as automotive and marine components).