Analysis of ball milling time to produce self-lubricating copper-tungsten disulfide composite: best trade-off between tribological performance and electrical properties

Ball milling is a fundamental step of powder metallurgy widely employed for composite manufacturing. This work focuses on the influence of ball milling time on the morphological, electrical, and tribological properties of self-lubricating copper-tungsten disulfide (Cu-WS2) composites. The study investigates ball milling times between 1 and 24 h to guarantee different degrees of incorporation of WS2 in the copper matrix. Micro-scratch and wear tests are performed to evaluate the tribological behavior. Optical, scanning electron, and confocal laser scanning microscopy analyze the scratch and wear tracks. The results show the reliability of the production process and a general improvement of the composites' mechanical properties compared to pure copper. The addition of WS2 enhances the tribo-mechanical properties, increasing hardness and wear resistance and decreasing the friction coefficient. Shorter ball milling times result in larger WS2 flakes distributed in the copper matrix, while longer ball milling times result in smaller and more dispersed particles. This homogeneous fine dispersion determines a difference in the composites' electrical conductivity and tribological performance, with shorter ball milling times (i.e., between 2 and 4 h) offering the best trade-off between wear behavior and electrical properties.