Surface analysis of tribofilm formed by phosphorus-nitrogen (P-N) ionic liquid in synthetic ester and water-based emulsion

This paper focuses on surface analysis of tribofilm formed by a P-N type ionic liquid (trade name VANLUBE 672, abbreviated it as T672) in synthetic ester (pentaerythritol tetraoleate known as PETO) and water-based emulsion. PETO blended with T672 shows better anti-wear, anti-friction and anti-seizure properties than water-based emulsion blended with T672, which could originate from the tribofilm formed on the surface by characterization of SEM-EDS, CLSM and XANES. Tribofilm is composed of oligomeric phosphate and the polymerization and content of oligomeric phosphate could be affected by the medium and friction conditions under different test depths. The improvement of tribological properties is determined by oligomeric phosphate. And the change of oligomeric phosphate content on near surface of PETO (bulk surface for emulsion) is consistent with the change of tribological properties.