High-frequency pulse electrodeposition and characterization of Ni-Co/ZrO_2 nanocomposite coatings

摘要

Ni-Co/ZrO_2 nanocomposite coatings were produced by high-frequency pulse electrodeposition in a modified Watt's bath containing ZrO_2 particles. The surface morphology, microstructure, and high temperature oxidation resistance of the coatings were characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray diffraction, and isothermal oxidation tests. It was found that the presence of ZrO_2 particles resulted in changes in the morphology and structure of the coatings. The results also confirmed the nanostructure and uniform distribution of ZrO_2 particles of Ni-Co/ZrO_2 nanocomposite coatings. The addition of ZrO_2 did not change the preferred orientation (200), but remarkably affected the relative intensity of planes of Ni-Co alloy. The influence of duty cycle, average current density, and frequency on the amount of incorporated ZrO_2 particles in the Ni-Co/ZrO_2 nanocomposite has been also investigated. The Ni-Co/ZrO_2 nanocomposite coatings with highest ZrO_2 content (11.6 wt%) were prepared under the condition of duty cycle of 40 %, average current density of 5 A dm~(-2), and frequency of 100 kHz. Moreover, the embedded ZrO_2 particles significantly improved the high temperature oxidation resistance of Ni-Co alloy coatings. The oxidation rate of Ni-Co/ZrO_2 nanocomposite coatings decreased with increasing the ZrO_2 content of the coatings.