Characterization of electrodeposited Ni–SiC–Cg nanocomposite coating

Abstract

Nickel–silicon carbide–graphite (Ni–SiC–Cg) nanocomposite coating was deposited onto the steel (St-37) substrate by electrochemical plating method. The influence of pH parameter on the mechanical properties and morphological features was studied. The coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Elemental mapping analysis system, and field emission scanning electron microscopy (FE-SEM) techniques. Besides, the microhardness of specimens was measured by Micro hardness Tester. Based on XRD results, the dominant phases with high crystallinity degree were nickel, silicon carbide and graphite. Microscopic observations illustrated that all the coatings had a cluster like structures which consisted of some fine sphere particles with an average crystallites size of 60nm. Among of all coatings, the specimen at pH equal to 4.8 presented an appropriate morphology as well as lower porosity with high grain boundaries. Moreover, elemental mapping spectra exhibited a homogenous distribution of nickel, silicon and carbon particles. However, the distribution of silicon particles into nickel matrix at pH=4.8 was higher than the other samples. Also, mechanical properties of the attained coatings were improved with increasing of pH values up to 4.8 (593 HV) which is in agreement with microstructural characteristics. Therefore, obtaining of the optimum pH value is the major parameter in electroplating of Ni based nanocomposite which affected microhardness and distribution of reinforcement particles into the matrix.