Sliding wear‐induced nano‐tribofilm formation from EP/AW agent on copper foil against ferroalloy counterparts under high load

Abstract

Sliding friction of copper foil surface, which was exposed to bis (6‐acetyl‐1,3,6,2 ‐dioxazaborocan‐2‐yl) methyl phosphate (NEPB) as extreme‐pressure/antiwear agent in base oil while rubbing by a ferroalloy disk under high load, was explored in a multi‐specimen test machine to investigate the wear mechanism of NEPB on thin film lubrication. The results reveal that NEPB reduces the friction coefficient to ~0.16 at normal load of 200 N, and it has better antiwear and friction‐reducing property than the common copper oil. Ferroalloy against copper foil is along the Cu (111) direction, and the friction coefficient decrease relies on the spontaneous formation of chemically nanolayered tribofilm (approx. 30 nm) during sliding wear. The size of wear debris arranges from 6 nm to submicron. Decomposed borate esters and organic nitrides were adsorbed on the worn surface and P element of NEPB as extreme‐pressure/antiwear agent reacted with Cu and existed in the form of phosphates, both of which contributed to the formation of boundary lubricating film.