The structural changes taking place in the dissimilar laboratory welds of 6CrMoV 8-3-2 (T25), being under development, and modified X12CrMoVNb 10-1 (P91) nitrided steels annealed at temperatures of 500 – 900 °C have been subject of study. Carbon and nitrogen redistribution measurement by the EPMA method was complemented with detailed structural analysis aimed at the phase profiles and chemical composition of coexisting carbides and carbonitrides in particular regions of the weld joint. Results of experimental work were compared with thermodynamic and kinetic modeling using the DICTRA software. A very good agreement between the modeling and the experiments was observed.

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