过碱烷基酚钙与二烷基二硫代磷酸锌复配形成摩擦膜的表征

利用X射线吸收精细结构光谱(XANES)研究了过碱硫化烷基酚钙与二烷基二硫代磷酸锌(ZDDP)复配使用时对ZDDP形成摩擦膜的表面化学行为的影响, 并提出了其和ZDDP的相互作用机制. 结果表明, 在ZDDP中加入过碱硫化烷基酚钙后完全改变了ZDDP单独使用时形成摩擦膜的结构, 摩擦膜中含有一定数量的钙离子, 其结构以磷酸钙为主; 对较高碱值的过碱硫化烷基酚钙, 在高浓度下使用时, 在摩擦膜形成的同时观测到碳酸钙颗粒的沉积. 此外, ZDDP和过碱硫化烷基酚钙共同使用时形成的摩擦膜厚度减小. 摩擦膜特性的改变是ZDDP和过碱硫化烷基酚钙复配体系抗磨性能变差的主要原因.

Characterization of Tribofilms from Zinc Dialkyldithiophosphate in the Presence of Overbased Calcium Phenate Detergents

The effect of overbased calciumphenate detergents on the chemical composition of tribofilms fromzinc dialkyldithiophosphate (ZDDP) under boundary lubrication has been studied using P, S, Ca, and C X-ray absorption near edge structure (XANES) spectroscopy. Boundary lubrication was achieved by a pin-on-disk reciprocating wear machine. Calciumphenate detergents, in both high and low overbased forms, were used in combination with ZDDP. C K-edge XANES showed that when higher overbased detergents were used the micelles containing calcium carbonate broke down and calcium carbonate was deposited in the tribofilm. Direct evidence for the formation of calcium phosphate from ZDDP in combination with detergents was provided by XANES spectroscopy at the P-, K- and L-edges. Zn2+ ions were replaced by Ca2+ in the polyphosphate structure of tribofilms forming short chain polyphosphates. The effects of these chemical changes were correlated to the tribological performance of ZDDP/detergents systems.