Experimental investigation of coconut shell charcoal and boron carbide/zirconium dioxide in aluminium 7075 matrix composites under varying operating conditions: a comparative analysis

Abstract

This study focused on investigating the influence of varying weight percentages of coconut shell charcoal (CSC) on the physical, mechanical, and wear properties of aluminum 7075 (Al-7075) matrix composites reinforced by boron carbide (B4C) and zirconium dioxide (ZrO2). Throughout the study, these composites were prepared with a constant 3 wt% B4C/ZrO2. The developed composites were then subjected to the tribological analysis using a pin-on-disc apparatus under a constant sliding speed (2000 m), a sliding distance (4 m s−1), and varying operating temperatures (room temperature, 150, 200, and 250 °C). The worn-out surfaces of the composites were examined using a magnified scanning electron microscope (SEM) to investigate the microstructural analysis and wear behavior. The composites containing 3% B4C/ZrO2 and 3% CSC exhibited the highest hardness and wear resistance among the studied composites. The incorporation of CSC increased the density and porosity of the composites up to a 3 wt%, but at 4 wt%, a decrease was observed. It is worth noting that the B-series samples had slightly lower hardness values compared to the Z-series samples. Regarding the effect of temperature, the wear rate decreased as the temperature increased. The Al-7075/ZrO2/CSC composite demonstrated improved wear resistance and coefficient of friction (COF) compared to the Al-7075/B4C/CSC composite, with respective enhancements of 19.30% and 42.19%. The analysis of variance (ANOVA) confirmed the significant impact of CSC weight fraction on wear for both composites, whereas only the Al-7075/ZrO2/CSC composites showed significance for COF. The SEM analysis revealed that the addition of CSC resulted in a uniform distribution of particles within the matrix, leading to improved wear resistance. Therefore, this study demonstrated that the addition of CSC influenced the density, porosity, hardness, wear resistance, and COF in the Al-7075 matrix composites. Optimal performance was achieved with a 3 wt% CSC for Al-7075/ZrO2/CSC at 250 °C. The composites developed in this study, comprising boron carbide (B4C)- and zirconium dioxide (ZrO2)-reinforced aluminum 7075 (Al-7075) matrix with varying weight percentages of CSC, have several potential applications such as in the fields of automotive, aerospace, defense, and industrial machinery.