Modelling Precipitation Sequences in Power Plant Steels

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

Abstract

Part I: Application of Kinetic Theory

The ability of steels to resist creep deformation depends on the presence in the microstructure of carbides and intermetallic compounds which precipitate during tempering or during elevated temperature service. The precipitation occurs in a sequence which leads towards thermodynamic equilibrium. The present paper deals with an extension of the Johnson-Mehl-Avrami theory for overall transformation kinetics. The modification permits the treatment of more than one precipitation reaction occurring simultaneously, a feature which is found to be essential for representing the reactions observed experimentally in a wide range of secondary hardening steels.

Download paper, Materials Science and Technology, 28A (1997) 631-639.

Addendum

Abstract

Part II: Application of Kinetic Theory

New kinetic theory capable of dealing with the simultaneous precipitation of several phases has been applied to a variety of creep resistant power plant steels. It has been demonstrated that the model has the ability to preict the vast differences in precipitation kinetics reported in the published literature for power plant steels. New experimental results on precipitation in a 9Cr1Mo type steel are reported and shown to be consistent with theoretical precitions.

Download paper, Materials Science and Technology, 28A (1997) 640-644.

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