Influence of the microstructure on the degree of sensitization of a duplex stainless steel UNS S31803 aged at 650oC

摘要

This work evaluates the phase transformations during aging of an UNS S31803 DSS at 650oC and its influence on the DOS. The material was solution treated at 1175oC and then aged at 650oC for times up to 360 h. SEM-BSC images indicate the formation of Cr2N, σ and χ phases in the samples aged at 650oC. The analysis of DL-EPR curves, obtained in a 1 M H2SO4 + 0.25 M NaCl + 0.01 M KSCN solution, shows an increase in DOS values for samples aged at 650oC. Probably, this increase observed in DOS values is mainly related to the presence of Cr- and/or Mo-depleted α, as a result of σ phase, χ phase and/or Cr2N formation at 650oC. Moreover, a possible healing up of Cr- and/ or Mo-depleted areas is observed between 1 h and 4 h of aging at 650oC.