Duplex stainless steels configure a family of metallic alloys that combined elevated mechanical properties with improved corrosion resistance when compared to standard austenitic grades. This excellent combination of properties leads to their use under many different applications, particularly in the fields of chemical, petrochemical, pulp and paper industries. Moreover, these applications usually involve cyclic loading, and consequently the study of fatigue properties has a great significance for reliable design and safe-operation. This chapter is devoted to study and analyze the cyclic deformation response of duplex stainless steels under standard testing conditions. The first point studied is the fatigue behavior of a duplex stainless steel corresponding to the last generation or superduplex. The cyclic stress-strain curve (CSSC) was determined through a wide interval of plastic strain amplitudes by incremental fatigue tests. Afterwards, constant total strain amplitude fatigue tests were performed at four different total strain amplitude values, values that correspond to marked different positions within the CSSC. TEM analysis of the different substructures developed within both constituent phases, i.e. austenite and ferrite, was done for each plastic strain amplitude. Finally, results obtained for the superduplex steel are compared to those reported for other duplex with lower nitrogen content tested under similar experimental conditions.

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