Investigation of growth kinetics of Fe2B layers on AISI 1518 steel by the integral method

The AISI 1518 steel was pack-borided in the temperature range 1123?1273 K for a treatment ranging from 2 to 8 h. A compact single boride layer (Fe2B) was formed at the surface of the AISI 1518 steel using the mixture of powders composed of 20% B4C, 10% KBF4 and 70% SiC. The following experimental techniques such as scanning electron microscopy coupled with EDS analysis and X-ray diffraction analysis were employed to characterize the pack-borided AISI 1518 steel. An alternative model, based on the integral mass balance equation, was used to estimate the boron diffusion coefficients in the Fe2B layers in the temperature range 1123?1273 K. Finally, the value of activation energy for boron diffusion in the AISI 1518 steel was estimated and compared with the literature data. Furthermore, the present model was validated by comparing the experimental value of Fe2B layer thickness, obtained at 1253 K for 2 h of treatment, with the predicted value.