Estimation of Fe₂B growth on low-carbon steel based on two diffusion models

Two different approaches are used in the evaluation of Fe₂B growth and its kinetics over the surface of AISI 1018 steel. The first approach considers a diffusion model based on the mass balance at the growing Fe ₂B/substrate interface. In the second approach, the method of dimensional analysis was applied to obtain an expression for the boride layer thickness as a function of dependence parameters involved in the boriding process. The Fe₂B layers were formed by the paste boriding process at temperatures of 1123 to 1273 K with 2, 4, 6, and 8 h of exposure using a boron carbide paste thickness of 4 mm over the surface of the steel. Another set of boriding temperatures with 5 h of exposure were used on the surface of the steel to compare the experimental values of Fe₂B layer thicknesses with the results obtained by both diffusion models. The predicted values showed good agreement with the experimental boride layer thicknesses achieved in this work.