The effect of rare earth yttrium on properties of Ni-W/ZrO₂layers

Aluminum alloys often fail to meet harsh environmental conditions, such as abrasion and erosion, due to their inherent limitations in terms of unsatisfied hardness and wear resistance. In this paper, Re/Ni-W-ZrO2 composite layers are fabricated on the surface of an aluminum alloy matrix by electroplation. The cross-sectional morphology, elemental distribution, thickness and surface hardness of the composite coatings are characterized. The impact of the addition of Re-Y(NO3)3 on the characteristics of the coating is further examined. The coating is well bonded to the matrix material while ZrO2 particles are dispersed within the Ni-W base metal layer with a thickness of 136 μm. When Re is added to 1.5 g/L, the thickness and hardness are enhanced significantly. This is because the unique 4f electronic structure of rare earth elements not only plays a role in refining the grain during the coating growth process, but also effectively reduces the overpotential that may be generated during the deposition process, thereby increasing the deposition rate, so as to obtain a denser and finer grain structure.