Growth Kinetics of Boronized Layers and the Diffusion Zone in the Iron-Based A286 Superalloy with the Taylor Expansion Model

This work addresses the modelling of growth kinetics for FeB, Fe2B, and the diffusion zone formed after the solid boriding of the iron-based A286 superalloy. A novel kinetic model was developed to analyze the boron diffusion in this multi-layer system, with a non-linear boron distribution in each phase. The boron concentration profile within each phase was expressed as a function expanded in a second-order Taylor series. Subsequently, the proposed model was used to assess the boron diffusion coefficients in the FeB and Fe2B layers, as well as in the diffusion zone (DZ), using experimental data from the literature. As a result, the boron activation energies in the FeB, Fe2B, and DZ layers were determined to be 176.69, 201.05, and 207.80 kJ mol–1, respectively. Additionally, the experimentally measured layer thicknesses were compared with the predicted values, validating the developed model.