Investigation of the relationship between the electron work function (EWF), adhesion and friction

Adhesion and friction are of great theoretical interest and huge practical significance. The mechanisms of adhesion and friction are still subjects under investigation. Under light loads, friction is mainly dependent on the adhesion between two surfaces in contact, which is largely determined by the surface electron behavior. Electron work function (EWF) is a fundamental property of metals which characterizes their electron behavior and can be determined experimentally using a Kelvin probe.;In this study, attempts were made to establish relationships among EWF, adhesion and friction. For metal-ceramic contact, higher EWF corresponds to lower adhesive force and thus lower friction when measured under light loads using the AFM/LFM. Under higher loads involving plastic deformation, the friction of a target metal is mainly determined by its mechanical behavior. For metal-metal contact (mainly elastic contact) under light loads, an energy consumption friction (ECF) model was proposed to calculate friction coefficient. This model assumes elastic contact between two metals in contact and the calculation includes adhesion energy and deformation energy when the two metals slide on each other. Friction coefficient is thus expressed as a function of EWF and mechanical properties of the metals. Further study has established a correlation between EWF and elastic behavior which makes it possible to predict adhesion and elastic-contact friction mainly based on the EWF. Such a relationship between material's property and performance is important for materials selection and optimization of nano/micro devices.