Growth kinetics of boride layer by molten salt electrodeposition

The boride layer on silicon steel sheet was obtained by electrodeposition in KCl-NaCl-NaF-Na₂B₄O₇ molten salt at 1023, 1073 and 1123K for 15, 30, 45, 60, 90 and 120 min. The types of borides formed were analyzed by X-ray diffraction analysis (XRD). The distribution of the elements of boride layer was measured using the glow discharge spectrometry (GDS) and the depth from the surface to the substrate was taken as the layer thickness. It was found that the longer boronizing time resulted in an increase in thickness layer and the thickness of boride layers ranged from 15 to 172 μm. Depending on boronizing time, these layers can be single, double or three phase of FeB, Fe₂B and α-Fe. Layer growth kinetics was analyzed by measuring the thickness as a function of treatment time and temperature. Kinetic studies showed a parabolic relationship between layer thickness and process time, and the activation energy was 223 kJ/mol.