Electrodeposition of functionally graded Ni−W/Er₂O₃ rare earth nanoparticle composite film

Multi-layered functionally graded (FG) structure Ni−W/Er₂O₃ nanocomposite films were prepared by continuously changing the deposition parameters, in which the Er₂O₃ and W contents varied with thickness. The microstructure and chemical composition of the electrodeposited Ni−W/Er₂O₃ films were determined by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The anti-corrosion and wear properties of the electrodeposition films were investigated by electrochemical measurement and ball-on-disk friction test. The microhardness distribution of the cross section of nanocomposites was measured by nanoindentation. The results showed that with decreasing agitation rate or increasing average current density, the contents of Er₂O₃ nanoparticles and tungsten were distributed in a gradient along the thickness, and the contents on the surface were larger. By comparison, FG Ni−W/Er₂O₃ films had better anti-corrosion and wear properties than the uniform Ni−W/Er₂O₃ films. Atomic force microscopy (AFM) and profilometry measurements indicated that Er₂O₃ nanoparticles had an effect on the surface roughness.