Tribological Behavior of N-containing Boric Acid Derivatives and Their Synergetic Effects with ZDDP

Two kinds of N-containing boric acid derivatives, referred to as ODOB-Ca and DPOB, as lubricating oil additives were synthesized to replace or partially replace ZDDP and characterized using infrared spectroscopy and element analysis. The two additives showed good thermal stabilities in air. The hydrolytic stabilities of ODOB-Ca (37 h) and DPOB (92 h) determined by saturation vapor pressure were better than that of T154B (9 h). Their tribological behaviors as additives in mineral oil and synergetic effects with ZDDP were evaluated on a four-ball friction and wear tester. The results show that two synthesized compounds as additives in mineral oil exhibited good anti-wear property. Synergic effect of compound ODOB-Ca/DPOB and ZDDP in terms of the anti-wear property was observed. The tribofilm which is composed of B₂O₃, iron oxide and sulphates was revealed by X-ray photoelectron spectroscopy surface analysis.