A kinetic model for analyzing the growth kinetics of Fe₂B layers in AISI 4140 steel

A kinetic model based on the mass balance at the growing interface and the effect of the boride incubation time was used to evaluate the growth of Fe ₂B layers. The parabolic growth constant obtained by the model was expressed as a function of boron content in the Fe₂B layer and the process temperature. The simulated values were compared with experimental data derived from the literature, basically, for the boriding of AISI 4140 steel in the temperature range of 1123-1273 K. In addition, an expression of the Fe ₂B layer thickness was obtained that showed good agreement with the experimental results. Finally, the instantaneous velocity of the Fe ₂B/substrate interface and the weight gain produced by the formation of the Fe₂B layer were evaluated.