Abstract
Friction-velocity characteristics of ZDDP containing oils were determined with a pin-on-disk type tribometer. The gradient of friction μ-velocity V curve significantly depended upon the kinds of ZDDP. That is, secondary alkyl ZDDP showed the large negative gradient, while primary ZDDP with linear long alkyl chain group showed the positive gradient. After the macro scale tribotests, the local topography and the electrical current images on the wear track of the disks were determined with a scanning probe microscope. The topographical images exhibited that the surfaces for both ZDDPs were highly heterogeneous and they were composed of the pads and the cavities between the pads. By comparing the local topographical images with electric current images, it was suggested that the pads were covered with tribofilm having high electrical resistance.
