Synthesis and Corrosion Performance Evaluation of Nanostructured Duplex Stainless Steel Alloys Prepared by MA and SPS

Nanostructured duplex stainless steel (DSS) was prepared using mechanical alloying (MA) and spark plasma sintering (SPS). The ball milling was performed under nitrogen atmosphere. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to identify the phases and carry out morphological investigations, respectively. XRD spectra revealed that ferrite phase formation dominated during the initial stages and austenite phase emerged after several hours of ball milling. Lattice parameter calculations showed a decrease in lattice parameter up to 5 h and later increased at 10 h of milling. A decrease in crystallite size was observed up to 10 h of milling. SPS was performed in vacuum at an optimized temp. of 1000 °C for a fixed holding time of 10 min, heating rate of 100 °C/min, cooling rate of 200 °C/min and under an applied pressure of 50 MPa. The electrochemical performance of DSS alloys was examined using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). The results showed that alloy Fe-18Cr-3Mn-1Mo-1Si-0, 22N-5Ni (wt.%), has the highest corrosion resistance among the designed alloys.