Abstract:A novel high temperature and ashless cyclic phosphate ester (CP) used as grease additive was synthesized.Thermal stability tests were conducted via a thermo gravimetric analyzer (TGA),and its anti-wear property was evaluated through an Optimol SRV-IV oscillating reciprocating friction and wear test on high temperature.SEM and XPS were also employed to investigate the morphologies of the wear scars and lubrication mechanism.Results indicate that the CP can effectively improve the tribological performances of the base grease,and can enhance the extreme pressure property of the base grease to some extent.Boundary lubrication films composed of Fe(OH)O,FexOy,FePO4 are formed on the worn surface through chemical adsorption and tribochemical reactions when using CP as grease additive,which results in excellent friction-reducing and anti-wear properties.