Possible impacts of third body nanostructure on friction performance during dry sliding determined by computer simulation based on the method of movable cellular automata

The tribological properties of nanostructured surface films formed during dry sliding, for example during automotive braking, were determined by modelling using the method of movable cellular automata. Starting from a basic model structure, consisting of magnetite with 13% graphite inclusions, the impact of additional soft and hard particles of different size and volume fraction was studied systematically. It was revealed that agglomerates of soft particles decomposed and finally mixed with the oxide in the same way as single nanoparticles. On the other hand, agglomerates of hard particles mixed with the other components without decomposing. Whereas increasing the amount of soft components in the third body lowered the coefficient of friction, the opposite occurred with the hard particles. The boundary conditions for obtaining smooth sliding conditions with minor fluctuations between friction forces at successive time steps could be defined. In addition to features of the nanostructure, the applied normal pressure impacted modelling results. Within the parameter range of smooth sliding behaviour, increasing pressure induced thicker granular interface layers, which lead to a slight decrease of the coefficient of friction. Changing the amount of soft or hard particles did not change this pressure dependency but only the friction level.

► The nanostructure of tribologically induced surface films is determined experimentally.
► The element size of the MCA-model was adjusted to the grain size of the nanostructure.
► The model enabled us to simulate sliding and calculate corresponding coefficients of friction.
► Impacts of composition and nanostructures of films were studied systematically.