The European efforts in material development for 650°C USC power plants -: COST522

Advanced Steam Power Plant is one of three working groups within the frame of European COST 522 with the aim of developing and evaluating ferritic steels for steam conditions up to 650degreesC. Today's state-of-the-art large fossil-fired steam turbines comprise live steam conditions of up to 610degreesC/ 300 bar and re-heat temperatures of up to 630degreesC. These ultra super critical steam parameters significantly increase plant efficiency and reduce fuel consumption and emissions of CO2. Ferritic materials should be used for thick-walled components to maintain high operational flexibility of such large plants. Rotors, casings, bolts, tubes/pipes and waterwalls are the critical components under current investigation. The class of the 9-12% Cr steels offers the highest potential to meet the required property level for critical components. Therefore a significant effort to increase the application temperature of these steels was the focus of study within the European COST 501 programme and has led to improved materials for 600degreesC application of forged and cast components and for pipework. These 600degreesC materials are already being successfully utilised in a number of advanced European power plants. Further potential for improvement in creep strength seems possible after taking into account the oxidation resistance for T> 600degreesC. A large number of new ferritic-martensitic compositions, which have been designed on the basis of the positive outcomes attained in previous studies as well as on the results obtained with advanced thermodynamic calculation tools are under investigation in the new COST 522 programme. Full-size cast and forged components have been manufactured from the most promising compositions and now are being evaluated by intensive mechanical testing.