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Duplex stainless steels (DSSs) are in between the austenitic and theferritic grades, combining the best mechanical and corrosion resistance properties ofboth. As a result of their high mechanical strength, good thermal conductivity andexcellent corrosion resistance, DDSs are extensively used both in pulp and paperindustries, in chemical and petrochemical plants. They also find some applications infood and biomedical fields as well. The high chromium (between 21 and 27 wt.%) andmolybdenum (up to 4.5 wt.%) contents allow the use of DSSs under conditions ofpitting, crevice and, above all, stress corrosion cracking that would be critical for thetraditional AISI 304 and 316. Finally, some economic advantages follow as a result oflower nickel content than the austenitic grades. Fatigue crack propagation in duplexstainless steels is strongly affected by microstructure and therefore by the choice of thesteel grade or by the heat treatment conditions. In the present work we considered threedifferent sintered duplex stainless steels. Their fatigue crack propagation resistance wasinvestigated by means of fatigue crack propagation tests according to ASTM E 647standard, considering three different stress ratios (R = Kmin/Kmax). Crack surfaces wereextensively analysed by means of a scanning electron microscope. Crack paths wereinvestigated by means of a crack path profile analysis performed by means of anoptical microscope. In order to analyse phases volume fractions and microporesinfluence, da/dN-ΔK fatigue crack propagation results were compared with profile anfracture surface analysis.