Waste to wealth approach: RSM-based tribological optimization of red mud/WC hybrid reinforced AA6061 composites

Waste management has emerged as one of the most significant concerns facing all countries. In order to improve pollution reduction, reuse, and recycling, it is crucial to use the waste for practical solutions. Among the waste materials, 120 million tons of red mud (RM) are generated annually throughout the world. Hence, this study intends to use aluminum waste-driven RM and tungsten carbide (WC) particles as reinforcement to develop the AA6061 metal matrix composites (MMCs) by using stir-casting techniques. The hybrid reinforcement at varying concentrations (2, 4, and 6 wt.%) was incorporated into Al MMCs to systematically investigate their tribological behaviors with the aim of enhancing the wear resistance of aluminum matrix composites and improving their suitability for sliding-wear engineering applications. In addition, the variable wear parameters such as sliding load and speed were used for evaluating the wear characteristics of Al MMCs. The microstructure of the composites was extensively investigated using advanced microstructural characterization techniques, such as scanning electron microscopy with energy-dispersive X-ray analysis, X-ray diffraction, and 3D surface topography, to evaluate the elemental and phase composition, worn surface failure mechanisms, and surface integrity. Moreover, a Brinell hardness study was performed on stir-cast samples to evaluate the mechanical behavior of composites. Additionally, a design of experiment with response surface methodology optimization techniques was utilized to optimize the reinforcement composition and wear parameters. Experimental results revealed that 4 wt. % reinforced composites reduced wear rate and surface roughness by 80.6% and 31.01%, respectively, when compared to base alloy materials, which were validated by optimization analysis. Based on the optimization analysis, the optimal SP and SL were determined to be 300 r/min and 47.56 N, respectively. Subsequently, future directions are indicated that could lead to more efficient and superior wear performance in sustainably reinforced MMCs.