Microstructure evolution of a Z-phase strengthened 9-12% Cr steel

Paper i proceeding, 2011

A new alloy design concept for martensitic / ferritic steels aiming for 650°C – the Zphase strengthened steels – has been developed in Europe. These new steels are expected to have good corrosion and creep resistance, which is attributed to a high Cr content (up to 12 %) and a dense distribution of stable Z-phase precipitates. This paper reports a study of the microstructure evolution of a trial Ta-containing Zphase strengthened steel. Samples with different aging times, from 24 hours to 10,000 hours, were investigated by using scanning electron microscopy and transmission electron microscopy. Mainly two types of precipitates, Z-phase and Laves phase, were found. The size distribution of the precipitates was analysed. It was found that Zphase precipitates, with very small initial size, have a very low coarsening rate.