This work describes with the investigation of the precipitation kinetics of NbC in microalloyed steel. Using the thermo-kinetic software MatCalc, computer simulations of NbC precipitation are carried out and compared with several independent experimental results, measured in austenite and ferrite. The selected experiments involve a variety of different dislocation densities originating from distinct thermo-mechanical treatments. Two separate populations of NbC precipitates are accounted for in the simulations, representing precipitates on grain boundaries as well as dislocations. Furthermore, three different diffusion mechanisms are taken into account, which are bulk diffusion in the undisturbed crystal, accelerated diffusion along the dislocation core and fast diffusion along grain boundaries. It is demonstrated that deformation-induced dislocation densities higher than 10 ~(13)m ~2 lead to prominent diffusion along dislocation networks. Therefore, in such cases, the precipitation kinetics of NbC is dominated by the pipe diffusion mechanism, and the precipitation process is several orders of magnitude faster compared with NbC precipitation in unstrained, well-annealed microstructures.
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