Influence of pulse frequency on the microstructure and wear resistance of electrodeposited Ni–Al2O3 composite coatings

Nickel matrix composite coatings reinforced with sub-microsized Al2O3 particles were produced by pulse electrodeposition and the effect of pulse frequency on the microstructure, hardness and wear resistance of Ni–Al2O3 composite coatings were investigated. The results showed that the pulse frequency significantly influenced the preferred orientation of Ni–Al2O3 composite coatings; the texture of the coatings progressively changed from a strong (111) preferred orientation to a random orientation when pulse frequency increased. The hardness of composite coatings decreased slightly with the increase of volumetric content of alumina particles. The wear behaviors of composite coatings under dry sliding wear and oil-lubricated wear conditions were different significantly. The wear resistance of Ni–Al2O3 coatings decreased with the increase of incorporated alumina particles under dry sliding wear condition, which was largely influenced by the microstructure of Ni matrix due to the presence of adhesive wear. However, the wear resistance of composite coatings increased with the increase of volumetric content of the reinforcements under oil-lubricated wear condition, which mainly depends on the volumetric content of incorporated alumina particles because the adhesive wear can be avoided under oil-lubricated wear condition.