Surface Reaction Behavior of Isogeometrical Phosphorus Compounds

Isogeometrical phosphorus compounds, used as model oil additives, were selected to study the role of sulfur and phosphorus under increasingly severe lubrication conditions. A modified commercial test device has been applied to measure friction and wear. Application of Auger electron spectroscopy leads to a better understanding of the beneficial role of AW/EP additives. A general mechanism resulting in the formation of acid phosphates is proposed as the first step of tribofragmentation. Phosphorus seems to be mainly responsible for the load-carrying capability of reaction layers under the present experimental conditions. A reduction in the phosphorus concentration immediately leads to an increase of friction and wear.