Microstructural evolution, boride layer growth kinetics, and activation energy of dual-activator borided AISI 1040 steel

This study investigates the microstructural evolution, boride layer growth kinetics, and activation energy for boron diffusion in AISI 1040 steel borided using a dual-activator medium. Boriding was performed at 1173, 1223, and 1273 K for 2, 4, and 6 h. The phase composition of the boride layers was characterized by X-ray diffraction, while microstructural features were examined using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. Under all conditions, a characteristic saw-tooth boride layer consisting of FeB and Fe 2 B phases was formed. The minimum layer thickness was 95 ± 8 μm after 2 h at 1173 K, while the maximum reached 265 ± 9 μm after 6 h at 1273 K. The activation energy for boron diffusion, determined using the parabolic growth model, was 133.62 kJ mol −1 . The results demonstrate that dual-activator boriding produces thicker, more homogeneous boride layers and offers an energy-efficient surface modification technique.