Characterization of Boride Layers on S235 Steel and Calculation of Activation Energy Using Taylor Expansion Model

S235 low-carbon steel was boronized between 1123 K and 1273 K using a commercial powder mixture (Durborid) to study the formation and growth behavior of boride layers. The type of interface and thickness of the resulting layers were determined with scanning electron microscopy (SEM). The technique of X-ray diffraction (XRD) confirmed the formation of a predominantly single-phase Fe2B layer under most processing conditions. To assess the diffusion behavior, the kinetic model with a Taylor series expansion was implemented to calculate the B diffusion coefficients in the Fe2B layer under a transient diffusion regime. The B activation energy in Fe2B was determined to be 157 kJ/mol, which aligns well with values derived from the literature.