Micrometer and nanometer La2O3 particles were codeposited with nickel by electroplating from a nickel sulfamate bath. The wear behaviors of the composite coatings were evaluated sliding against AISI 1045 steel under non-lubricated conditions. It was found that the incorporation of the La2O3 particles enhances the microhardness and wear resistance of Ni coatings. The wear resistance of the Ni composite coating containing nano-sized La2O3 particles is higher than that of the Ni composite coating containing micro-sized La2O3 particles. The codeposition of the smaller nanometer La2O3 particles with Ni effectively reduces the size of Ni crystals and significantly increases the hardness of the composite coatings, resulting in significantly improved wear resistance of the nano-sized La2O3/Ni composite coating. (c) 2006 Springer Science + Business Media, Inc.