Molecular dynamics study on nano sliding behavior at DLC/AISI 304 interface

Abstract

Diamond-like carbon (DLC) serves as a prevalent protective coating for stainless steel in various applications, including automotive engines and medical devices, to combat wear and corrosion. This investigation delves into the nanoscale interface friction and mechanical behavior between DLC and polycrystalline austenitic stainless steel. Molecular dynamics simulations were employed to model the sliding interface structure's evolution and friction performance under differing contact pressures and graphitization states. In the friction sliding process, carbon atoms predominantly experience surface structural reorganization with minimal diffusion. The displacement of stainless steel's internal atoms is chiefly driven by deformation rather than diffusion. The study also examines the synergistic impacts of external pressure, structural transformations, and interfacial compounds on the system's friction mechanism. At low contact pressures (≤8 GPa), austenite deformation and recrystallization triggered by friction were noted. Conversely, at high junction pressures (>8 GPa), the interplay of stress and strain induces martensitic transformation in stainless steel and amplifies mechanical mixing with DLC. The α′-martensite proportion correlates positively with contact pressure and friction duration. An uptick in martensite content escalates the system's friction force; however, when the system's friction is governed entirely by martensite, it manifests a stable low friction force. Furthermore, under varied carbon atom hybridization conditions, systems characterized by high sp³ hybridization display increased strain and friction. These insights provide valuable perspectives for improving the research on DLC and stainless steel nano micro interfaces.