Parametric investigation of tribological performance in gold surface via molecular dynamics simulation: effects of normal load, sliding speed and temperature

Au coatings are widely used in electrical contacts because of their high conductivity, chemical stability, and low contact resistance. However, repeated insertion, fretting, and high local stresses can cause wear and subsurface damage. Molecular dynamics simulations with an Au spherical tip sliding on an Au (100) single-crystal substrate were used to investigate the effects of normal load, sliding speed, and temperature on friction and damage evolution. Increasing normal load raises the tangential force but reduces the steady-state coefficient of friction (COF) and its coefficient of variation (COV), while increasing indentation depth, wear atoms, and front and side pile-up. Increasing sliding speed reduces the COF, COV, numbers of wear and hexagonal close-packed (HCP) atoms, and total dislocation length, indicating less accumulated and retained damage. Temperature has a nonmonotonic effect: friction decreases from 250 to 350 K because of thermally activated relaxation, whereas thermal softening and atomic migration at 400 K cause deeper indentation and more severe damage. Plastic deformation is dominated by 1/6⟨112⟩ Shockley partial dislocation glide and associated stacking-fault/HCP evolution. These findings connect frictional behavior with atomistic defect evolution and provide guidance for improving the reliability of Au-coated electrical contacts.