Tribological behavior of borate as additives in rapeseed oil

A new borate containing sulfur and nitrogen was synthesized and the tribological performances of the novel additive in rapeseed oil were investigated using a four-ball machine. The chemical features of the worn steel surfaces were observed and examined by means of X-ray photoelectron spectroscopy (XPS). As the results, the borate as additive can obviously increase the load-carrying capacity, antiwear and friction-reducing abilities of rapeseed oil. The XPS analytical results of typical elements on the worn steel surfaces indicate that a boundary lubricating film composed of triester of rape-seed oil, organosulphur compound, sulfate and boron oxide was formed on the worn surface, by way of chemisorption and/or tribochemical reaction. This contributes to improve the tribological properties of the rapeseed oil.