Thermodynamic simulation of ferritic to ferritic dissimilar metal welds

Modern computational calculation power enables scientists to accurately predict the microstructural evolution of complex metallurgical systems and, for example, their phase formation at elevated temperature for an extended amount of time. Valuable information can be derived from those calculations without the necessity of expensive and complicated experiments. Especially the field of power generation, where service parameters strongly influence the applied materials, can benefit from computational simulations. This study will highlight the use of thermodynamic simulations on the behavior of T23 to T91 ferritic dissimilar metal welds (DMWs) at elevated temperatures, similar to creep conditions. The software MatCalc is used to calculate precipitation sequences in the base metals, as well as carbon migration in DMWs from the higher alloyed to the lower alloyed material at elevated temperatures and precipitate distribution across the fusion line of the DMWs. The results of the simulations are verified with creep exposed cross-weld samples (80 MPa, 600 °C, and 625 °C) tested for up to 14,000 h.