Unveiling localized protection and media-dependent degradation mechanism of Inconel 625 coating during tribocorrosion

Localized wear and the complex microstructure trigger significant inhomogeneous tribocorrosion of the Inconel 625 coating. The micro-galvanic cell between the interdendrite and dendrite, between the precipitation and Inconel 625 matrix, as well as the macro-galvanic cell between the worn and unworn zone, accelerate corrosion in worn zone, while creating a distinct cathodic protection zone surrounding the worn zone. The interaction between wear and corrosion in different media (air, H₂O, NaCl, and HCl solution) and applied loads are quantitatively decoupled, revealing the media-dependent and load-dependent nature of tribocorrosion. Corrosive media reduces the coefficient of friction (COF) and mechanical wear. In NaCl solution, corrosion and wear are comparable, and their interaction results in the weakest tribocorrosion, whereas in HCl solution, the dominant role of corrosion is significant and leads to larger tribocorrosion degradation. Meanwhile, increasing loads exacerbated both corrosion and wear.