Abstract
Among the applications for protic ionic liquids (PILs), lubrication is one of the newest and the most promising. In this work, ammonium-based protic ionic liquids were tested as lubricant fluids for aluminum-steel contacts. PILs were synthesized with 2-hydroxyethylamine (2HEA) and a carboxylic acid (formic and pentanoic), aiming to understand the effect of two different anion chain lengths on the lubricant behavior. The synthesized PILs were characterized by RMN, FTIR and TGA. Wear tests, conducted using a ball-on-plate configuration, showed that the increase of the anion carbon chain length in the PIL structure reduced significantly the coefficient of friction value. Besides, after the wear tests, the PILs structural integrity was not affected. In the same way, bending under tension (BUT) tests evidenced that the performance for stamping conditions of the PIL with the longest anion carbon chain was similar to that of the commercial lubricant. Since, both formed a uniform tribofilm, developed the same lubrication regime and the drawing forces values were close and constant. Hence, the ionic liquid obtained with 2HEA and pentanoic acid (2HEAPe) is as suitable as the commercial lubricant for metal forming processes.
Highlights
Research about ionic liquids has recently developed a trend oriented to protic ionic liquids (PILs) due to their wide spectrum of application
Another study[15] evaluated phosphonium cation-based ionic liquids with different anions and concluded that the increase of their reactivity with the steel-steel and aluminum-steel contacts allowed the formation of a tribofilm and had the best tribological behavior
The aim of this work is to evaluate the behavior of ammonium-based protic ionic liquids as lubricant fluids for aluminum-steel contacts as well as their feasibility for using in metal forming
Summary
Research about ionic liquids has recently developed a trend oriented to protic ionic liquids (PILs) due to their wide spectrum of application. Their properties of extremely low vapor pressure, high viscosity, high thermal and ionic conductivity, non-flammability, thermal and chemical stability, and low toxicity make them suitable in many fields of applications, such as catalysis, electrochemical devices and separation processes. Liu et al.[9] tested the Initially, most of the research involving ionic liquids as lubricants used alkylimidazolium as cation and tetrafluoroborate or hexafluorophosphate as anion, due to their availability[13]. Another study[15] evaluated phosphonium cation-based ionic liquids with different anions and concluded that the increase of their reactivity with the steel-steel and aluminum-steel contacts allowed the formation of a tribofilm and had the best tribological behavior
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