MODELO NUMÉRICO PARA SIMULAÇÃO DA DIFUSÃO ATÔMICA EM SISTEMAS MULTICOMPONENTES CONTENDO FASES DISPERSAS APLICADO AO ESTUDO DA NITRETAÇÃO DE AÇOS

An approach for numerically simulating in a one-dimensional system the three-dimensional process of atomic diffusion in multiphase microstructures of multicomponent systems is proposed. This numerical approach is based in the Calphad method and the multicomponent diffusion formalism. A numerical algorithm for implementing the proposed approach was build up by generalizing the previous model by Engström et al.(2) with new features that allow to compute transient states during diffusion when atomic partitioning between matrix phase and dispersed phases is far from the local equilibrium condition. After describing the algorithm, it is applied to an experimental case of nitrogen diffusion in stainless steel with chromium nitride precipitation during high temperature gas nitriding. The main characteristics of the proposed approach, their advantages and their restrictions, are discussed in depth using the case study.