Wrought Ni-Base Superalloys for Steam Turbine Applications beyond 700 deg C

• Published in: Advanced engineering materials 2003-07, Vol.5 (7), p.469-483
• Main Authors: Rosler, J, Gotting, M, Del Genovese, D, Bottger, B, Kopp, R, Wolske, M, Schubert, F, Penkalla, H-J, Seliga, T, Thoma, A
• Format: Article
• Language: English
• ISSN: 1438-1656

The development of a new steam turbine generation for use in advanced coal fired power plants with prospective operating temperatures beyond 700 deg C and a projected thermodynamic efficiency of about 55 % requires, amongst other innovations, the partial substitution of ferritic steels by wrought Ni-base superalloys. Although Ni-base alloys are already widely used in the aerospace industry, they are faced with demands regarding component size and operation temperature, which by far exceed current aeroengine requirements. In this article, the potential of selected alloys for 700 deg C steam turbine applications is discussed with respect to their manufacturability and mechanical performance. Hereby, the focus is on the steam turbine rotor, which probably is the most critical component. It is concluded that material solutions are available for operation conditions around 600 deg C but not for temperatures of 700 deg C and above. Based on these results, alloy development strategies are suggested in order to close this gap and two new alloys, DT 706 and DT 750, are introduced.