Tribocorrosion behavior of Co-based self-lubricating composites with varying contents of Ag in NaCl solution

Abstract

Majority of self-lubricating composites exhibit a high wear rate due to corrosion. In this study, Co-based self-lubricating composites with addition of Ag were prepared via spark plasma sintering to manage their tribocorrosion resistance. No interfacial reaction occurred after sintering. Their tribocorrosion behavior in 3.5 wt.% NaCl solution was characterized as a function of applied potentials. In corrosion-free conditions, i.e. applying a cathodic potential (−1 V), the addition of Ag enhances wear rate of the Co-based composites. While in a state of OCP or applying an anodic potential, galvanic corrosion occurs between Ag and Co-matrix. It promotes the formation of a loose oxide film and reserves most silver debris, which contributes synergistically to reduced friction coefficient and wear rate. With the addition of 12 wt.% Ag, Co-based self-lubricating composite exhibits the lowest friction coefficient of 0.09 and wear rate of 3.8 × 10⁻⁵ mm³/(Nm) at OCP.