Durable Near-Zero Wear Behavior Achieved by Polymer-Based Protic Ionic Liquids on Engineering Steel Surfaces

Area of Science:

• Materials Science
• Tribology
• Surface Engineering

Background:

• Engineering steel surfaces experience significant wear, limiting mechanical equipment lifespan.
• Existing low-wear strategies are often condition-specific and lack broad applicability.
• Developing advanced lubricants is crucial for enhancing material durability and performance.

Purpose of the Study:

• To design and evaluate a novel polymer-based proton ionic liquid (PPILs) lubricant for achieving near-zero wear on engineering steel.
• To investigate the tribological performance of PPILs under high contact pressures and demanding environmental conditions.
• To explore the potential of PPILs in superlubrication systems for advanced material applications.

Main Methods:

• Synthesis of polymer-based proton ionic liquids (PPILs) via proton exchange between polyethylenimine and bis(2-ethylhexyl) phosphate.
• Tribological testing of PPILs on steel surfaces under high Hertzian contact pressures (2.15 GPa).
• Evaluation of lubricant performance under long-term friction and high-frequency conditions.
• Development of a superlubrication system by combining PPILs with polyol aqueous solutions for Si3N4/glass friction pairs.

Main Results:

• PPILs demonstrated a friction coefficient of ~0.08 and an exceptionally low wear rate (1.46 × 10^-10 mm³·N⁻¹·m⁻¹) on steel under high pressure.
• Durable near-zero wear behavior was maintained even under prolonged friction and high-frequency testing.
• A superlubrication system (friction coefficient μ = 0.007) was achieved with an ultrashort running-in period (<3 s) using PPILs and polyol solutions.
• The near-zero wear is attributed to synergistic effects of adsorption films, tribochemical films, and hydrodynamic lubrication.

Conclusions:

• The developed PPILs represent a new class of lubricants offering superior wear resistance for engineering steel.
• This study overcomes limitations in achieving ultralow wear, expanding the application scope of advanced lubrication materials.
• The findings contribute to the field of superlubrication by introducing effective PPIL-based systems with rapid performance.