Operando formation of hydration layer and tribofilm of graphene oxide for achieving synergistic lubrication on electrochemical boronizing surface

Graphene oxide (GO) has emerged as a promising additive for water-based lubricants, however, its costly functionalization and the real-world challenges of integrating it in harsh environments complicate its application in engineering materials. Additionally, the mechanisms through which it effectively reduces friction and wear remain inadequately understood. This study addresses these obstacles by proposing a novel strategy to enhance the adhesion of GO on the surfaces of engineering materials through advanced surface engineering techniques. A high-hardness and anti-wear boriding surface on GCr15 steel is prepared through the fast electrochemical boronizing (ECB) treatment. GO nanosheets show a strong attraction on the ECB surface to form a dense operando tribofilm with high load-bearing capacity, through the squeezing and shear film formation mechanisms as revealed by molecular dynamics simulations. Under such confined conditions, water film existing between GO interlayers and SiO₂ surfaces induces the optimal hydration lubrication, with a friction coefficient down to 0.04 and near-zero wear for the synergistic effect of ECB surface and 1 wt% GO nanosheet solution. Conversely, the increase in sliding frequency and load damages the GO tribofilm, resulting in hydration lubrication failure. Our findings corroborate the intimate correlation between the hydration lubrication and the synergy of ECB treatment and solid-liquid composite lubricant, advancing the field of tribology and promoting practical applications of GO in lubrication.