Advanced FeCrAl ODS steels for high-temperature structural applications in energy generation systems

Abstract

Technologies and means for developing biomass plant with higher energy conversion efficiencies are essential in order to implement the commitment to renewable biomass energy generation. Advanced, indirect Combined Cycle Gas Turbine (CCGT) systems offer overall biomass energy conversion efficiencies of 45 % and above, compared with the 35 % efficiency of conventional biomass steam plant. However to attain this efficiency in CCGT operation it will be necessary to develop a heat exchanger capable of gas operating temperatures and pressures of around 1100 °C and 15-30 bar, respectively, for entry heating the gas turbine working fluid. ODS ferritic steels is the kind of advance material to deal with this challenge, however work to optimize the coarse grain microstructure to improve creep hoop strength needs to be done. In this sense, this paper reports the recrystallisation behaviour of PM 2000 oxide dispersion strengthened ferritic alloy which was cold deformed after hot-rolling and extrusion. The results can be interpreted if it is assumed that anything which makes the microstructure heterogeneous, stimulates recrystallisation. In this sense, larger strain gradients lead to more refined and more isotropic grain structures. The combination of these results with finite element modeling are used to interpret the role of residual shear stresses on the development of recrystallized grain structure.