Microstructure and tribological properties of electrodeposited Ni-Co alloy deposits

Ni-Co alloys with different compositions and microstructures were produced by electrodeposition. The effects of Co content on the composition, surface morphology, phase structure, hardness and tribological properties of Ni-Co alloys were investigated systemically. Results showed that the morphology and grain size of alloys are mainly influenced by the Co content and the phase structure of Ni-Co alloys gradually changed from fcc into hcp structure with the increase of Co content. The hardness of Ni-Co alloys with a maximum around 49 wt.% Co followed the Hall-Petch effect. It was found that the improvement of wear resistance of Ni-rich alloys with hardness increase fits Archard's law. In addition, the Co-rich alloys exhibited much lower friction coefficient and higher wear resistance when compared with Ni-rich alloys. It has been concluded that hcp crystal structure in Co-rich alloys contributed to the remarkable friction-reduction effect and better anti-wear performance under the dry sliding wear conditions.