Synergistic effect of cementite amorphization and oxidation on forming a nanocomposite self-lubricating surface during sliding

The in situ formation of a self-lubricating surface is potentially valuable and greatly significant for reducing wear in many steel material applications, especially nanocomposite self-lubricating surfaces. Here, we discover a novel nanocomposite self-lubricating oxide surface composed of amorphous structures and oxide nanoparticles. The nanocomposite oxide structures and tribolayer on pearlite after dry sliding were characterized in detail by using spherical aberration transmission electron microscopy (TEM), and direct evidence of cementite amorphization was observed. Moreover, cementite interfacial amorphization was visualized, and the radial distribution function was calculated by a molecular dynamics (MD) simulation. Notably, high-resolution characterization and elemental distribution analyses were performed on an incompletely formed self-lubricating surface. The relationship between the amorphization and formation of nanocomposite oxides is explained in terms of friction strain, heat and oxygen intervention. After the cementite in the tribolayer is transformed into an amorphous structure, it becomes part of the wear debris formed due to dry sliding friction. Wear debris containing nanolamellar and amorphous structures is continuously transformed into oxide nanoparticles after being mechanically mixed, rolled and oxidized on the contact surface. Utilizing the in situ formation of nanocomposite oxide surfaces can further improve the tribological and wear properties of metal materials containing cementite structures.