AbstractIn this study, we have measured changes in hardness and residual stress state in polycrystalline nickel samples which have undergone a variety of ion beam surface treatments including self-implantation, amorphization by ion beam mixing Ni-Al multilayers, and the formation of a two-phase microstructure by elevated temperature aluminum implantation. Hardness-depth profiles of the the near-surface regions were determined using an ultra-low load microindentation system, and residual stress states induced by the surface modifications were analyzed using optical interferometry. These property changes were correlated with the accumulation of surface fatigue damage.