Characterization of electrodeposited Ni-Cr/hBN composite coatings

Abstract

In this study, NieCr/hBN composite coatings with different hBN content were deposited on AISI 1040mild carbon steel using electrodeposition. The coatings were characterized using scanning electronmicroscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffractometry (XRD), cyclic voltammetry(CV), 2D surface profilometery, nano-indentation, corrosion and wear tests. While some cracks wereobserved in the NieCr alloy coatings, more compact and crack-free surfaces were obtained in the NieCr/hBN composite coatings under all deposition conditions. XRD analysis of the NieCr/hBN layer revealedthe presence of a predominant Ni phase with Cr, Cr2Ni3B6, (Ni2Cr23)0.16, and hBN phases in the structure.Depending on deposition parameters, the microhardness and nanohardness of the NieCr and NieCr/hBNcoatings were found to range between 308 and 538 HV and 1,86e7,69 GPa respectively. hBN acted as asolid lubricant in the wear tests; the friction coefficient decreased and wear resistance was improved.Among the composite coatings, the corrosion resistance of the coating with 20 g/l hBN was found to be12 and 3.3 times higher than the steel substrate and NieCr alloy, respectively. The hBN additive providedbetter mechanical properties and corrosion resistance in the range of 5e20 g/l hBN, but after 20 g/l hBNagglomeration became a problem and impaired the mechanical properties. The highest corrosion andabrasion resistance was obtained with 20 g/l hBN.