Bio-based ionic liquid crystal for stainless steel-sapphire high temperature ultralow friction

• Published in: Wear 2021-11, Vol.484-485, p.204020, Article 204020
• Main Authors: Avilés, M.D., Carrión, F.J., Sanes, J., Bermúdez, M.D.
• Format: Article
• Language: English
• Subjects: Bearing steels; Chromium steels; Coefficient of friction; Disks; Friction reduction; Heat resistant steels; High temperature; Ionic liquid crystal; Ionic liquids; Ions; Liquid crystals; Lubricants; Lubricated wear; Melting points; Moisture content; Sapphire; Sliding; Sliding friction; Stainless steel; Stainless steels; Steel; Surface analysis (chemical); Temperature; Tribology; Wear mechanisms; Wear rate; X ray photoelectron spectroscopy
• ISSN: 0043-1648; 1873-2577
• DOI: 10.1016/j.wear.2021.204020

In the present work, the biobased protic ionic liquid crystal bis(2-hydroxyethyl) ammonium palmitate (DPA) has been studied as neat lubricant under linear reciprocating sliding at 75 °C, in the liquid crystalline region, and at 110 °C, above its melting point. Three different tribopairs have been studied using AISI 52100 steel, AISI 316L stainless steel and sapphire balls against AISI 316L disks. Tribological results at 75 °C are in agreement with the different sliding pairs and contact conditions. At 110 °C, a sharp friction coefficient reduction to reach an ultralow steady state value of 0.007–0.009, is observed for the sapphire-AISI 316L contact. Wear rate is also reduced in one order of magnitude. Results are related to water content in DPA, as determined by TG-MS. Wear mechanism are discussed upon the basis of optical and scanning electron microscopy (SEM/EDX) and of surface analysis by XPS. •DPA reaches ultralow steady state friction at 110 °C for sapphire-steel.•Friction and wear of sapphire-steel lubricated with DPA are lower at 110 °C than at 75 °C.•Water loss and surface analysis are related to tribological performance.