Friction behavior of nanocrystalline nickel near the Hall-Petch breakdown

Large-scale molecular dynamics simulations are carried out to investigate the friction behavior of nanocrystalline nickel (Ni) at low temperature. Grain sizes ranging from 4-11 nm are used to explore the behavior of nanocrystalline Ni near the Hall-Petch breakdown. Effects of grain size, grain morphology and scratch depth on coefficient of friction (COF) and deformation mechanism of nanocrystalline Ni are investigated. Reduction of the COF with the refinement of grain size in nanocrystalline nickel is observed, however, for a grain size of 5 nm this trend is observed to be reversed. It is also found that scratch depth can influence the estimation of friction behavior of nanocrystalline nickel.