Kinetics of Formation of Fe2B Layers on AISI S1 Steel

In the present work, the AISI S1 steel was pack-borided in the temperature range 1123-1273 K for 2- 8 h to form a compact layer of Fe2B at the material surface. A recent kinetic approach, based on the integral method, was proposed to estimate the boron diffusion coefficients in the Fe2B layers formed on AISI S1 steel in the temperature range 1123-1273 K. In this model, the boron profile concentration in the Fe2B layer is described by a polynomial form based on the Goodman’s method. As a main result, the value of activation energy for boron diffusion in AISI S1 steel was estimated as 199.15 kJmol-1 by the integral method and compared with the values available in the literature. Three extra boriding conditions were used to extend the validity of the kinetic model based on the integral method as well as other diffusion models. An experimental validation was made by comparing the values of Fe2B layers’ thicknesses with those predicted by different diffusion models. Finally, an iso-thickness diagram was proposed for describing the evolution of Fe2B layer thickness as a function of boriding parameters.