Calculation of Precipitation Kinetics in CrMoV Power Plant Steels

J. D. Robson and H. K. D. H. Bhadeshia


A model has been developed which enables the kinetics of carbide, nitride and Laves phase precipitation to be predicted in a wide range of power plant alloys. A key feature of this model is that it allows for the simultaneous formation of all the precipitate phases, taking into account the competition for the available solute and free volume. In this way it is possible to predict the kinetics of precipitation without making any assumptions about the precipitation sequence. The model is demonstrated by correctly predicting the kinetics of precipitation in a 2.25Cr1Mo steel and a 10CrMoVNb alloy. By using the kinetics model in conjunction with thermodynamic predictions it is possible to simulate the complete evolution of the precipitate phases from a knowledge of alloy chemistry and heat treatment alone. This is demonstrated by making predictions for a commercial creep resistant 12CrMoVNb alloy. The calculated and observed phases agree well after short term tempering. After long term creep exposure discrepancies arise between predictions and observations due in part to inadequate thermodynamic data.

Modelling of Microstructural Evolution in Creep Resistant Materials, eds A. Strang and M. McLean, The Institute of Materials, London, 1999, pp. 115--128.

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