Effects of MoS 2 particles on tribological characteristics of ZA-27 alloy metal composites by ultrasonic-assisted stir-casting

Abstract

ZA-27 alloys are widely used in applications requiring high loads and moderate speeds, such as worm gears, bearings, and bushings. The wear resistance of ZA-27 alloy can be notably improved by reinforcing molybdenum disulphide (MoS₂) particles, a soft ceramic known for its outstanding lubricating characteristics. Limited studies have focused on incorporating MoS₂ particles into zinc-aluminium alloys, highlighting a need to explore their potential to enhance wear resistance and tribological properties. This study focuses on fabricating ZA-27 composites by an ultrasonic-aided stir-casting technique with varying MoS₂ content (0.5 wt.%, 1.0 wt.%, and 1.5 wt.%) to evaluate their tribological properties. The tribological performance of the composites was evaluated using a pin-on-disc machine, emphasizing parameters including reinforcement content, sliding distance, applied load, and sliding speed. Response surface methodology (RSM) and analysis of variance were utilized to examine the effects and interactions of these factors. The findings indicate that the incorporation of 1.5 wt.% MoS₂ leads to a reduction in the coefficient of friction (COF) by 0.23 and a decrease in the wear rate by $0.882\times {10}^{-6}$ mm³/m, underscoring the role of MoS₂ in improving tribological characteristics. Notable interactions between distance–speed and reinforcement–load impacted the wear rate, whereas distance–load influenced the COF. Mathematical models for wear rate and COF were developed using RSM, and confirmation tests showed discrepancies of 1.4% and 1.7%, respectively, between predicted and experimental results. Scanning electron microscopy analysis of the worn surfaces showed diminished debris and more uniform wear tracks, suggesting a robust bonding between the matrix and reinforcement.