Properties of Ni-Ni3Si composite coatings prepared by electrodeposition and subsequent heat treatment

Abstract

In the present work, the effect of heat treatment was investigated on the structure, hardness and corrosion behavior of Ni-Si composite coatings produced by an electrodeposition process. First, Ni-10 wt.% Si composite coatings were deposited on medium carbon steel substrate by the electrodeposition process. Afterward, the samples were heat-treated at 900 °C for 120 min under a vacuum of 10−3 atm. The produced coatings were characterized by X-ray diffraction and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. The electrochemical properties of the as-deposited and heat-treated coatings were evaluated in a 3.5 wt. % sodium chloride solution. Also, the hardness of the prepared coatings was studied and compared. The results indicated that due to the heat treatment, nickel silicide (Ni3Si) is formed in the coatings. Also, it was found that the heat treatment changes the morphology of the deposited coatings. The presence of the Ni3Si phase also decreased the corrosion current density of the deposited coatings and prevented the decline of the coating hardness after the heat treatment.