Aging of Fe-Cr-Co alloys in combustion gases of CO2-reduced power plants considering the diffusion of H and C

• Applicant: Dr.-Ing. Daniela Hünert
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: from 2010 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 187887912

For qualifying power plant steels, creep strength and corrosion resistance is usually measured. These experiments are mainly independently performed from each other. Most of the corrosion tests are carried out by exposing specimen surfaces to one corrosive media. In practice, power plant steels for heat exchanger tubes are subjected to two different atmospheres (dual atmosphere). In my PhD theses, I could prove that the exposure of tubes to steam/CO2 (inner side) and air (outer side) cause an accelerated material loss. Additionally, microstructural changes could be detected (e.g. formation, coarsening of carbides). These aging mechanisms can influence the creep strength and hence shorten the life time of the power plants tubes. The primary objective of the research project is the computer based prediction of the aging effect on 12% chromium steels in a dual atmosphere exposure (H2O at the inner side; flue gas at the outer side) and the validation of the model on specific Fe-Cr-Co-alloys. In detail, the phase composition and the microstructure of power plant steels (12% Cr) are simulated thermodynamically and the development of the phase composition under long term conditions is predicted. The mechanical properties should be estimated during service using this prediction. Especially the time dependent development of the phase composition in correlation with the mechanical properties is in our focus, because information under dual atmosphere is limited. The secondary objective of the research project is the investigation on Co strengthened 12% Cr-steels with respect to phase composition. Based on a thermodynamically simulation of the Fe-Cr-Co-system, a promising alloy compositions will be identified. For the validation of the model, chosen alloys are cast and investigated under power plant conditions.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Dr. Ursula R Kattner