Abstract
Ni-based composite coating containing nanodiamonds was deposited on the substrate of Q235A low-carbon steel in a traditional Watts solution, without any additive. The nanodiamond grains prepared by detonation synthesis were measured by Transmission electron microscope (TEM) and X-ray diffraction (XRD). The electrochemical behavior of Ni2+ ion in the composite bath including nanodiamonds was studied by linear sweep voltammetry experiments, and the morphology, elastic modulus, and hardness of Ni-based composite coating were characterized using Scanning Electron microscope (SEM) and the nano-indenter XP tester. Effects of the nanodiamond concentration in the bath, stirring speed, and the electroplate mode on the properties of Ni-based composite coating were investigated. The results show that the reduction of Ni2+ ion in the electroplating process increased initially, and then decreased as the nanodiamond concentration in the bath increased from 4 g/L to 16 g/L, irrespective of whether direct current (DC), single-pulse, or double-pulse electroplating mode was used. The highest over-potential could be obtained when the nanodiamond concentration in the bath was 8 g/L. Moreover, the hardness and elastic modulus of the composite coating prepared by the DC electroplating mode were 4.68 and 194.30 GPa, respectively. By using the same plating parameters, the coating prepared by the double-pulse electroplating mode showed better properties, with hardness and elastic modulus values of 5.22 and 197.38 GPa, respectively.
Highlights
The development of composite coatings has made great progress so far, and composite coatings have been applied in many fields
The effects of nanodiamond concentration on the electrochemical behavior of Ni2+ ion was first investigated by measuring the polarization curves in a bath with different nanodiamond concentrations to determine the optimum coating conditions
The following conclusions were drawn: The nanodiamond concentration in the bath affected the reduction of over-potential of Ni2+ ion and reached the maximum value at a concentration of 8 g/L
Summary
The development of composite coatings has made great progress so far, and composite coatings have been applied in many fields. Grosjean et al prepared Ni-SiC composite coatings on copper and gold substrate, and studied the effects of nano-SiC particle content on the microhardness and abrasion resistance of the coatings [6]. In order to provide technical guidance for the preparation of high-strength Ni/nanocomposite coatings, we explored the optimum formulation and process parameters for electroplating of Ni/nanodiamond composite in this paper. For this purpose, a low-carbon steel, Q235A, was chosen as the substrate and linear sweep voltammetry was used to test the electrochemical behavior of Ni2+ on the Q235A substrate in Watts nickel-plating solution, with different nanodiamond contents and at different stirring speeds.
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