Microstructure and Performance of nano-Al2O3/Ni-Co Composite Coatings by Electro-brush Plating

To remanufacture hard chromium-plated workpiece, nano-Al2O3/Ni-Co composite coatings and Ni-Co alloy coatings are developed using electric brush plating technology. Scanning electron microscopy (SEM) and transmission electron microscope (TEM) arc used to analyze the surface morphology, phase structure and wear properties of coatings. The surface morphology of nano-composite coating is more compact. The nano-particles are well-distributed in the coating and bounded tightly with the substrate. The hardness of composite coating is HV1027, increased approximately 38% compared with Ni-Co alloy coating, overtaking the hard chrome plating. The results of sliding wear test shows that the nano-composite coating reduces friction coefficient, increases wear resistance significantly and exceeds the chromium plating.