Alloy design and creep strength of advanced 9%Cr USC boiler steels containing high concentration of boron

The research and development project of National Institute for Materials Science (NIMS) for advanced ferritic heat resistant steels for 650°C ultra super critical (USC) plants, revealed that the addition of >0·01 mass% boron to a 0·08C–9Cr–3W–3Co–V–Nb–,0·003N steel remarkably improves the long term creep strength. Boron enriched in M23C6 carbides near prior austenite grain boundaries suppresses the coarsening of carbides during creep...