Effects of process current density and temperature on electrochemical boriding of steel in molten salts

In this study, the effects of current density and bath temperature on the hardness, thickness, and morphology of boride layer are systematically investigated. The electrochemical boride coating on steel substrates is carried out at various current densities (50–700 mA/cm2) and bath temperatures (800–1000°C) at constant electrolyte composition and electrolysis time. The FeB, Fe2B, and Fe3B phases are detected by the x-ray diffraction method. The hardness of the boride layer reaches approximately 1800 HV on the surface and gradually decreases toward the matrix. The optimum current density and electrolyte temperature for the boriding of low-alloy steel are determined as 200 mA/cm2 and 900°C, respectively.