Influence of the microstructure on the degree of sensitization of a duplex stainless steel UNS S31803 aged at 650[degrees]C

This work evaluates the phase transformations during aging of an UNS S31803 DSS at 650[degrees]C and its influence on the DOS. The material was solution treated at 1175[degrees]C and then aged at 650[degrees]C for times up to 360 h. SEM-BSC images indicate the formation of Cr sub(2)N, [sigma] and [Chi] phases in the samples aged at 650[degrees]C. The analysis of DL-EPR curves, obtained in a 1 M H sub(2)SO sub(4) + 0.25 M NaCl + 0.01 M KSCN solution, shows an increase in DOS values for samples aged at 650[degrees]C. Probably, this increase observed in DOS values is mainly related to the presence of Cr- and/or Mo-depleted alpha , as a result of [sigma] phase, [Chi] phase and/or Cr sub(2)N formation at 650[degrees]C. Moreover, a possible healing up of Cr- and/ or Mo-depleted areas is observed between 1 h and 4 h of aging at 650[degrees]C.