Ni-P-TiO2 nanocomposite coatings with uniformly dispersed Ni3Ti intermetallics: Effects of current density and post heat treatment

Abstract In the present work, the influences of current density and post heat treatment on the morphology, phase structure, microhardness, and corrosion performance of the Ni-P-TiO 2 nanocomposite coatings were investigated. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were employed to study the morphological and microstructural features of the coatings, respectively. In addition, corrosion performance of the coatings was evaluated via electrochemical impedance spectroscopy (EIS) and Tafel polarization. Results demonstrated that the Ni 3 Ti intermetallics forms all over the microstructure of the coatings. The volume fraction and distribution uniformity of such intermetallics is examined as a function of applied current density. In general, the as-plated coatings at current density of 15 A dm −2 exhibit the superior microhardness as well as corrosion resistance originated from their higher Ni 3 Ti amount. However, the morphology of the particles accompanied by chemical composition of constituent phases did not altered with change in current density. The electrodeposited coatings were heat treated at 400 °C in an argon atmosphere of electrical furnace. XRD patterns of the heat treated coatings show Ni 3 P and Ni phases. In addition, microhardness of the coatings noticeably increased with application of heat treatment mainly due to the precipitation of hard Ni 3 P intermetallics.