Tribological Properties of Ni/Cu Multilayers

Abstract

Sliding wear and hardness tests in Ni/Cu multilayers electrodeposited on polycrystalline copper substrate were carried out. The multilayers had a total thickness of 5 μm and an individual layer thickness from 5 to 100 nm. Hardness of the multilayers measured with a nanoindentation tester was found to be dependent on layer thickness. The multilayer with the layer thickness of 20 nm showed the highest value among them. It was found that the wear resistances of all the multilayers tested were higher than that of an electrodeposited nickel coating. It was also revealed that the specific wear rate of multilayers decreased with decreasing the layer thickness although the highest hardness was attained at the 20 nm layer thickness. Scanning ion microscope observation showed that the subsurface area kept the layered structure of nickel and copper even after sliding wear. The multilayer had plasticity sufficient to accommodate deformation coming from the sliding wear, because fine grains peculiar to severe plastic deformation process were formed near the worm surface.