Abstract
Cobalt-Nickel (Co-Ni) alloy coatings were prepared by jet electrodeposition on brass substrate under different Co2+/Ni2+ ratio contents (M = 2:1, 1:1, 1:2 and 1:3) and solution flow rates (from 2.0 to 4.5 L/min). The surface morphology, element content, and phase structure of the coating were observed by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and X-ray diffractometer (XRD). The hardness and wear resistance of the coatings were also measured. The results showed that the Co content in coatings was greater than 70%, no matter at what flow rate and concentration. With an increase of the flow rate, the Co content in the coating increases, and the grain size on the surface of the coating decreases, which leads to increased hardness of the coating. However, the flow rate of the plating solution has little effect on the grain growth orientation, and the phase structure is dominated by the elemental content of the coating. The coatings are in a single phase of hexagonal close-packed (HCP) when the Co content is more than 80%, while the coatings are in dual phases of the HCP and face-centered cubic (FCC) when the Co content is less than 80%. With an increase in the Co content, the grain size decreases, and consequently, the hardness and wear resistance of the alloy increase. A Co-Ni alloy coating with stable composition can be obtained when the ratio of Co2+ to Ni2+ is 2:1.
Highlights
Electrodeposited cobalt-nickel (Co-Ni) alloy coatings usually have superior properties that are better than both pure Co and Ni metals [1]
It is found that the Co content in the coating increases with the increasing flow rate
This is because the jet electrodeposition is a non-equilibrium process, and the metal cations are controlled by the mass transfer in the liquid
Summary
Electrodeposited cobalt-nickel (Co-Ni) alloy coatings usually have superior properties that are better than both pure Co and Ni metals [1]. Gómez et al [17] studied the influence of plating solution on the electroplating with grooves, and the results showed that the coating surface was uniform, fine and dense when the plating solution was stirred This is because the stirring of the plating solution in the bath plating affects the mass transfer of the cation. The plating solution flow rate is one of the key parameters in jet electrodeposition for preparing particle composite coatings This affects the mass transfer of the particles and the entry of the particles into the composite coating [19]. When jet electrodepositing the Co-Ni alloy matrix and particle composite coating, the plating solution flow rate may affect both the Co content and the particle content in the coating In this case, it is difficult to tell the property effect from the alloy matrix between the composited particles. Six different flow rates and four kinds of solutions were tested
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