Macroscopic superlubricity achieved by poly-L-lysine as an additive at the cemented carbide/steel cutting interface

To extend tool life and improve machining quality, this study proposes the use of amino acids as lubricant additives to lubricate the cemented carbide/steel cutting interface. The results showed that Poly-L-lysine (PLL) as an additive in ethylene glycol induced macroscopic liquid superlubricity, achieving a remarkably low coefficient of friction (COF) of 0.006, which further decreased to 0.0007 after 4 h, even under high contact pressures of 796 MPa. The achievement of superlubricity resulted from tribofilm generation, with the combined action of this film and the liquid phase effectively reducing frictional pair contact. The PLL additive induced friction reduction and wear resistance may facilitate breakthroughs in advanced cutting fluid formulations for industrial machining and manufacturing processes.