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Computational Modeling of the Strength Evolution During Processing And Service Of 9-12% Cr Steels

Dr.R.Udayakumar

9-12% Cr steels are frequently used in power plant components operating at pressures up to 280 bar and temperatures exceeding 600 °C. The complex microstructure of these materials consists of a fine-grained tempered martensite with a high density of precipitates, such as carbides, nitrides and intermetallic phases. In this paper, a novel model for simulation of the evolution of precipitates is applied to predict nucleation, growth and coarsening of precipitates as a function of the thermal history. Based on these data, the magnitude of precipitation strengthening is evaluated and set in relation to the measured creep rupture times of the test melt COST E2. It is concluded that the differences in strength observed with different production heat treatments can be well described with the new model. Moreover, the simulations confirm that the creep strength after 100.000 h of operation almost levels out due to microstructure and precipitate coarsening effects.