Modelling and experimental studies of alternative heat treatments in Steel 92 to optimise long term stress rupture properties

AbstractThe desire for power plant to give increased generating efficiency and decreased CO2 emission has led to considerable effort over the last 10–15 years, to develop ferritic–martensitic steels which can be used for steam temperatures up to about 650°C. Examples are the addition of boron and increasing chromium content to 10–12 wt-%. However, high chromium levels have led to problems with long term precipitate stability. One approach which has not been widely explored, is the use of novel heat treatments to optimise the preservice microstructure to give the best long term creep rupture strength. Increased austenitising temperatures and lower tempering temperatures have been examined in Steel 92 (9Cr–0·5Mo–2W) and have produced significant improvements in creep rupture strength at temperatures up to 650°C compared with material given a conventional heat treatment. This has been achieved without any loss in ductility compared with conventional heat treatments. Test data for durations in excess of 40 00...