42654 2017 eng lecture 0 -- -- -- In recent years, the performance of heat resistant ferritic-martensitic steels under cyclic oxidation and cyclic mechanical loading has gained considerable attention. The growing contributions of renewable energy sources to electricity generation have triggered a shift from continuous (baseload) operation of conventional power plants towards cyclic or “flexible” operation, which is needed to stabilize the electric grids by balancing the highly variable renewable’s input. Compared to the impressive amount of data on isothermal oxidation/corrosion and static mechanical loading (creep) that was compiled over decades, only little and sometimes contradictory information is so far available on the reaction of these alloys to cyclic conditions. The latter may involve frequent transients or holds at intermediate temperatures, as well as shut-downs and start-ups with high temperature rates which result in cyclic mechanical loads (thermo-mechanical fatigue, TMF) and thermo-cyclic oxidation at variable temperature. Our contribution will report on recent findings obtained within the framework of a junior research group which investigates the oxidation and fatigue of the ferritic-martensitic grades P91, P92 and VM12 SHC under thermo-cyclic conditions. Cyclic oxidation tests are carried out in steam using different sample shapes (flat coupons, U-segments and rings taken from heat exchanger tubes). Special attention is paid to changes in the kinetics and the integrity and possible delamination/spalling of the oxide layers. Mechanical tests are carried out on material from real steam pipes with a focus on the softening behaviour and lifetime issues resulting from combined creep/TMF loadings. All experiments are carried out in the 300-620°C regime with temperature and load profiles that resemble typical loading scenarios in power plants and are complemented by detailed microstructural characterisation. IUTAM-Symposium Multi-scale Fatigue, Fracture & Damage of Materials in Harsh Environments Galway, Ireland 28.08.2017 01.09.2017 0 Jürgen Olbricht eng uncontrolled Low cycle fatigue eng uncontrolled Thermo-mechanical fatigue eng uncontrolled Creep-fatigue eng uncontrolled Steam oxidation eng uncontrolled Power plants Ingenieurwissenschaften und zugeordnete Tätigkeiten Angewandte Physik Datei im Netzwerk der BAM verfügbar ("Closed Access") Präsentation