Molecular dynamics simulation on friction properties of BCC iron strengthened by nanodiamonds

As a typical reinforcement material, nanodiamond is widely used to strengthen the metal materials to improve their mechanical and friction properties. There is a long history for the iron using in industry, while its surface should be modified when used as tribopairs. In this work, nanodiamond is employed to strengthen the iron surface, and the mechanical properties and friction properties of the strengthened surfaces are investigated by molecular dynamics simulation. The hardness and elastic modulus of strengthened surface are studied by nanoindentation. It is found that with the increase of the number of nanodiamonds, the hardness (H) of the surface increases, while the elastic modulus (E) decreases. Using the strengthened iron as a substrate, a sliding contact model between an elastic iron tip and the substrate is proposed. The effects of the number of nanodiamonds and sliding velocity on the friction properties are studied. As the number of nanodiamonds increases, the adhesion component decreases. As a result, the average friction force and friction coefficient are reduced. Considering the influence of sliding velocity, more atoms of the substrate are removed for the case of a lower sliding velocity, and more dislocations are produced, leading to a higher average friction force.