Influence of dislocation density and grain size on precipitation kinetics on P92 grade steel

In this work, we have investigated the influence of dislocation density and grain size on precipitation kinetics in case of P92 grade steel during the long-term thermal exposure using the Software package Matcalc (version 6.00). For this study Classical Nucleation theory classifying the precipitates based Onsager thermodynamic extremum principle has been applied. Microstructural evolution of precipitates has been modelled with Kampmann-Wagner model. In the simulation, we considered the MX (NbC, VN) M23C6, Laves phase and Z-phase as possible precipitates and allowed to nucleate in Ferrite matrix. Dislocations, grain boundaries and sub-grain boundaries are chosen as probable nucleation sites for MX precipitates. Grain boundaries and sub-grain boundaries are considered as probable nucleation sites for Laves phase, M23C6 whereas VN precipitates are chosen as nucleation sites for Z-phase. Thermodynamic and kinetic simulations performed with dislocation densities 10(12) (m(-2)), 10(14) (m(-2)), 10(16) (m(-2)) and grain sizes 100 (mu m), 50 (mu m) and 30 (mu m) carried at 600 degrees C for 10(5) h. It has been observed that with increase in the dislocation density precipitation formation kinetics is accelerated. With variation in grain size process of evolution of precipitates does not have any significant changes during the thermal ageing of P92 grade steel. (C) 2019 Elsevier Ltd. All rights reserved.