High-Temperature Wettable Water-Based Lubricants toward Hot Rolling Lubrication

Abstract

Water-based lubricants have attractive properties compared to flammable oily lubricants but in high-temperature environments remain a tricky challenge due to the Leidenfrost effect-induced poor wettability once contacting sufficiently hot surfaces. Herein, a surfactant-modified Laponite nanoclay (LNC), as a prototype water-based lubricant with considerable lubricity, exhibits spontaneous high-temperature wettability by which the Leidenfrost point (LFP) can be improved above ≈350 °C on crude stainless steels, increasing by ≈140°C compared to pure water. The inter-particle attractions between LNC nanoplates increase the liquid viscosity, causing viscous force of bulk water near the substrate, allowing in situ deposition of LNC layers on the hot surface to trigger three-phase contact line (TCL) pinning. As a basis, wettable lubricants are further optimized on their lubricity by intercalating zwitterionic surfactants between LNC nanoplates, thereby reducing friction coefficient to ≈0.1. The LNC lubricants have been demonstrated in a four-ball tribometer to simulate hot rolling lubrication, providing insights for high-temperature metal processing, and potential applications in mechanical engineering and the aerospace field.