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The project results from the co-operation between Centro Sviluppo Materiali (CSM)., Rome and the Max Planck Institut f�r Eisenforschung (MPI), D�sseldorf. The main objetcives are the development and validation of particle coarsening models and their application to describe the evolution of carbides, mainly of M3C and M7C3 types, in steels for high temperature service. In such materials, the particle coarsening reduces the creep resistance, and therefore the growth kinetics of precipitates must be slowed down as much as possible. A controlled steel composition is fundamental to enhance the mechanical properties, through addition of alloying elements such as CR, Mo and V . Two alternative mechanisms can be used to effect this. The first is the precipitation of carbides containing not only iron but also chromium, manganese and other alloying elements, which influence the coarsening rate controlling the diffusion process. The second involves the formation of one or more metastable carbide phases, whose sequential precipitation is kinetically controlled by the nucleation process. Only during ageing at high temperature can the ultimate stable phase form. Its subsequent coarsening process results from a competitive diffusianl rection involving the elements shared with the metastable phases. The description of this process, which is more complex than single-phase coarsening, represents the second objective to be achieved by mathematical modelling. Within the common project, CSM developed differnt coarsening models, both for single-phase and two-phase systems. The results have been analysed in the light of recent theory.

Additional information

Authors: DI NUNZIO P E, CSM, Rome (IT);HOUGARDI H P, MPI, Dusseldorf (DE);LAN Y, MPI, Dusseldorf (DE)
Bibliographic Reference: EUR 18633 EN (1998) 185pp.
Availability: Available from OOPEC Sales agents
ISBN: ISBN 92-828-5044-7
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