Synthesis and tribological behavior of ashless alkylphosphorofluoridothioates

Ashless alkylphosphorofluoridothioates were synthesized and their tribological performance was comparatively studied with zinc dialkyldithiophosphates (ZDDP) by high frequency reciprocating ball tests. Formulations with alkylphosphorofluoridothioates in base oil at 0.1% (w/w) phosphorus level show significantly better antiwear performance than that with ZDDP, in particular for compounds with medium or long alkyl chains. The tribofilms generated from HFRB tests were examined using X-ray absorption near edge structure spectroscopy (XANES). XANES analysis demonstrates that tribofilms from alkylphosphorofluoridothioates are made up of oxides, sulfides, sulfates and short chain phosphates of iron while tribofilm from ZDDP is made up of oxides, sulfides, sulfates and short chain phosphates of iron in addition to sulfides, sulfates and short chain phosphates of zinc.