Recycling prospect and sustainable lubrication mechanism of water-based MoS2 nano-lubricant for steel cold rolling process

Abstract

The water-based MoS2 nano-lubricant was prepared and tentatively applied in cold rolling lubricant recirculation systems to investigate its recycling prospect and sustainable lubrication mechanism. The tribological properties and rolling lubrication performance of recycled nano-lubricants with different cycle stages were preliminarily evaluated using four-ball tribotester and two-high rolling mills. To determine the phase transformation of MoS2 in recycled nano-lubricants, the already used MoS2 nano-lubricant was collected, dried and then analyzed by means of X-ray diffraction (XRD). Molecular dynamics simulation was conducted to analyze the specialized lubrication mechanism of reused MoS2 nano-lubricant. The results revealed that the MoS2 was considered to gradually transform into MoO3 during cold rolling process. Those oxidizing metamorphic MoS2 nano-lubricants still had excellent friction reducing and wear resistance. That indicated MoS2 nano-lubricant could be recycled in cold rolling process. The recirculation of MoS2 nano-lubricant reduced the use of lubricants, the discharge of waste liquid and the production cost. Not only the pollution to environment was relieved, but also resources and costs were saved. The calculation results of adsorption energy between nanoparticles and steel surface further demonstrated the absorbing type of lubricating film in different cycle stages. A lubrication model suitable for MoS2 nano-lubricants under steel strip cold rolling lubrication circulation condition was established to explain their sustainable lubrication mechanism.