Ni–Co alloy and Ni–Co–Y₂O₃ multiple coatings refined with nano-Y₂O₃ particles were fabricated by ultrasonic-assisted electrochemical deposition in an acid sulfamate bath. Linear sweep voltammetry (LSV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) techniques were applied to investigate the nucleation/growth process of composite coatings in co-deposition. The LSV results indicated that the incorporation of nano-Y₂O₃ particles with the Ni–Co matrix shifted the initial deposition potential to a more positive potential and decreased cathodic polarization. For both coatings, the nucleation/growth process approximately agreed with the Scharifker–Hill instantaneous nucleation model. Nucleation parameters, including active nucleation sites (N₀) and nucleation rate (A) of the composite, were higher when the measured potential range was between −1.05 V (vs. SCE) and −1.20 V vs. SCE, when compared with the Ni–Co alloy, and the observed AFM images of the coatings were in good agreement with the calculated nucleation parameters (using the Marquardt–Levenberg algorithm) of experimental curves. EIS testing indicated that the charge transfer resistance of the composite was lower in electrodeposition. The incorporation of nano-Y₂O₃ particles in the matrix changed the preferred orientation of coatings and produced a more uniform and compact deposit layer with finer grains.

Ni–Co duplex coatings were cladded onto Cu to improve the antiwear properties of Cu products. Prior to laser cladding, n-Al₂O₃/Ni layers were introduced as interlayers between laser cladding coatings and Cu substrates to improve the laser absorptivity of these substrates and ensure defect-free laser cladding coatings. The structure and morphology of the coatings were characterized by scanning electron microscopy and optical microscopy, and the phases of the coatings were analyzed by X-ray diffraction. Their hardness was measured using a microhardness tester. Experimental results showed that defect-free composite coatings were obtained and that the coatings were metallurgically bonded to the substrates. The surface of the Ni–Co duplex coatings comprised a Co-based solid solution, Cr₇C₃, (Fe,Ni)₂₃C₆, and other strengthening phases. The microhardness and wear resistance of the duplex coatings were significantly improved compared with the Cu substrates. The average microhardness of the cladded coatings was 845.6 HV, which was approximately 8.2 times greater than that of the Cu substrates (102.6 HV). The volume loss of the Cu substrates was approximately 7.5 times greater than that of the Ni–Co duplex coatings after 60 min of sliding wear testing. The high hardness of and lack of defects in the Ni–Co duplex coatings reduced the plastic deformation and adhesive wear of the Cu substrates, resulting in improved wear properties.

In order to evaluate the electrochemical behavior of nano-ZrO₂ particles in the co-deposition process, revealing the electrocrystallization mechanism and electrodeposition parameters of composite coatings, cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) techniques were used to offer a favorable reference for electrochemical studies in an acidic amino sulfonate bath, and the kinetic parameters were calculated by fitting the experimental curves. The CV results suggested that the co-deposition of nano-ZrO₂ particles and matrix metal caused the initial deposition potential of Ni²⁺ and Co²⁺ to shift to more positive values (−0.80 V vs SCE) while the nano-ZrO₂ inhibited the reduction of H⁺ and decreased the cathodic polarization in co-deposition. The electrocrystallization of Ni-Co and Ni-Co-ZrO₂ sedimentary layer were governed by the Scharifker–Hill instantaneous nucleation model, and the nucleation rate of composite coatings was higher at potentials ranging from −1.10 to −1.15 V, and nano-ZrO₂ absorbed on an electrode surface promoted the nucleation/growth of Ni²⁺ and Co²⁺. However, nano-ZrO₂ particles hindered the nucleation/growth of Ni²⁺ and Co²⁺ at −1.20 and −1.25 V vs. SCE; the calculated results were consistent with the theoretical analysis of experimental curves. An EIS test indicated that the incorporation of nano-ZrO₂ particles into the matrix did not obviously effect the electric double layer at the electrode/electrolyte interface, but the charged transfer resistance of the composite was decreased in the electrodeposition.