Self-replenishing lubrication mechanism of nano-silver-reinforced AISI 4140 steel composites under dry sliding for mechanical applications

Abstract

Wear is one of the most important factors limiting mechanical components' lifespan and durability. In this study, a novel, AISI 4140-Ag steel-based, self-lubricating nanocomposite was manufactured by the spark plasma sintering (SPS) technique. The high-level aim of this investigation is to obtain a deeper understanding of how silver (Ag) at the nanoscale can enhance the self-lubricating layer's replenishment, which aids in maintaining a steady supply of solid lubricant under dry conditions. Tribological experiments were conducted under various loads (30–150 N) at 5 Hz frequency and 300 °C temperature using a Rtec Universal Tribometer (ball-on-disc setup). After that, advanced surface characterization techniques were utilized to illustrate predominant wear modes, lubrication mechanisms, and the chemical identity of the self-lubrication layer. Noticeably, the AISI 4140-Ag nanocomposite reduced the friction coefficient and wear rate by 36.16–51.14 % and 93.40–97.36 %, respectively, compared to the AISI 4140 composite. The excellent self-lubricating performance is mainly attributed to the replenishment of a self-lubricating layer on the substrate material and a transfer layer on the counterbody, composed of AgO and Fe2O3. The results of our study hold considerable promise for the advancement of self-lubricating composites and the enhancement of their durability in mechanical applications.