Tribological Characteristics of LM13/Si3N4/Gr Hybrid Composite at Elevated Temperature

Abstract

LM13/12wt.%Si3N43wt.%Gr hybrid composite was fabricated by liquid metallurgy route and its tribological characteristics were tested using pin-on-disc tribometer. The experiments were conducted as per L27 orthogonal array to study the influence of process parameter at normal and elevated temperature (150 °C) by varying process parameters such as load (10, 20, 30 N), sliding velocity (1, 2, 3 m/s) and sliding distance (750, 1250, 1750 m). The results revealed that the wear rate at both temperatures was proportional to load due to the stress induced which fractures Si3N4 particles and stripes aluminium matrix. As the sliding velocity increases, wear rate showed an increasing trend due to three body abrasion from eroded Si3N4 grits. The wear rate was inversely proportional to sliding distance, because of MML (Mechanically mixed layer) formed from chemical reactions between tribo-layers. When load increases COF (Coefficient of friction) decreases then increases due to lubricating and tillage effect. As velocity and distance increases, COF decreases due to thermal softening, hardening of layer and also the lubrication effect produced by chemical reactions. Analysis of variance (ANOVA) and S/N ratio at room temperature and elevated temperature for both Wear rate and COF were developed to study the most significant parameters on corresponding responses. Confirmation experiments were conducted to validate multi-linear regression model. Worn surfaces were examined using scanning electron microscope (SEM) to investigate wear characteristics. Energy dispersive X-ray spectroscopy (EDAX) and X-ray diffraction (XRD) results confirmed the formation of MML and different phases formed during wear mechanism. The developed material can be used to fabricate cylinder liners, cylinder blocks and brake rotors.