Kinetic Modeling of Ultrafast Boriding of AISI 1045 Steel and Phase Homogenization

In this work, the Dybkov model was applied to simulate the boronizing kinetics of AISI 1045 steel and the subsequent phase homogenization (PH) by considering two fitting parameters and boride incubation times to reproduce the experimental thicknesses of FeB and (FeB + Fe₂B) layers. The bilayer (FeB/Fe₂B) was generated on AISI 1045 steel using the ultra fast boriding (UFB) process in the range of 1123 to 1223 K for 0.25–0.75 h. New expressions of analytical solutions of Dybkov model were then developed. As a main result, the boron activation energies in FeB and Fe₂B were determined as 145.27 and 133.13 kJ mol^–1 for FeB and Fe₂B layers, respectively. The relations describing the evolution of layers thicknesses during the phase homogenization (PH) were derived. They were used to estimate the holding time required for dissolving completely the FeB layer.