Nanoindentation and nanoscratch behaviors of Ag/Ni multilayers

The hardness, elastic modulus and scratch behaviors of Ag/Ni mulitlayers deposited by evaporation have been carried out by nanoindentation and nanoscratch. It has been found that the hardness ( H) increases, while the modulus ( E) decreases, that is to say an increase of H/ E as the periodicity decreases. Many mechanisms are included in nanoscratch, including initial elastic contact, plowing and fracture stage, in each multilayer. Coefficient of friction during plowing decreases with the decrease of the periodicity, which can be ascribed to decreasing material pile-up due to the increase of H/ E. Elastic recovery after scratching also increases as the periodicity decreases because of the increase of H/ E, which leads to improved wear resistance. The fracture stage will be postponed with decreasing periodicity, which also leads to better wear behavior.