Spatial Distribution of the Chemical Species Generated Under Rubbing from ZDDP and Dispersed Potassium Triborate
Résumé
The partial replacement of ZDDP by dispersed potassium triborate in engine oil was studied. X-ray Absorption Spectroscopy at the phosphorus, sulphur and boron edges was used to identify the chemical species in tribochemical films on the macro-scale. PhotoElecton Emission Microscopy (PEEM) was performed to study the distribution of the chemical species on the micron level. It was found that tribofilms are homogeneous at the 1-micron scale. It was established that zinc is associated only with sulphides and not with phosphates, and phosphates and borate have the same distribution. The cation associated with phosphates is most likely to be potassium from the borate additive. The wear scar width measured on the tribofilms and XANES analysis indicated that dispersed potassium triborate associated with ZDDP has a positive effect on wear prevention.