Search

Ni–Co–BN (h) nanocomposite coating was prepared by jet electrodeposition (JED) under different temperatures. The surface morphology, element composition, crystal structure, microhardness and corrosion resistance of the samples prepared at different temperatures were analyzed and characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), microhardness tester, electrochemical workstation, respectively. The experimental results showed that the micro-protrusions on the sample surface gradually changed from spherical to diamond with the variation of the temperature, and the consistency of the micro-protrusions was improved. The coating thickness and the Co content of the samples first increased and then decreased with the change of the temperature. The deposition temperature changed the gain size of the samples, but it had no obvious effect on the crystal structure. The crystal structure of all the samples was still face centered cubic (fcc) structure. When the temperature was 60°C, the sample had better performances in the microhardness and the corrosion resistance. Under this parameter, the average value of the microhardness reached 608.5 HV0.05, the corrosion current density was 0.54 μA/cm2, and the corrosion rate was 6.51 μm/year. [ABSTRACT FROM AUTHOR]

In this study, Ni–Co–Al2O3–SiC nanocomposite coatings with varying concentrations of Co were electrodeposited in a modified watts bath using conventional electrodeposition technique. The microhardness, surface morphology and phase structure of the coatings were characterized using Vickers microhardness tester, scanning electron microscopy and X-ray diffraction, respectively. The corrosion resistance of the composite coating was evaluated in 3.5% NaCl solution using an electrochemical work station. Increase in Co concentration in the electrolyte resulted in an increase in the microhardness of the nanocomposite coating. Corrosion resistance of coatings was also seen to increase considerably with increase in Co concentration in electrolyte. This was attributed mainly to the decrease in grain size, chemical composition, phase structure and preferred orientation of the coatings. The increase in Co in the electrolyte had a significant effect on the crystallite size of the Ni–Co–Al2O3–SiC coatings. [ABSTRACT FROM AUTHOR]