EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

A superduplex stainless steel grade has been produced by powder metallurgy and laser metal deposition. The proper heat treatments have been performed to obtain approximately equal volume fraction of austenite and ferrite phases and avoid precipitation of detrimental phases, as chromium nitrides or sigma phase. The corrosion behaviour of the superduplex stainless steel samples has been studied in 3,5%wt NaCl solution by electrochemical tests. In the case of the laser deposited material, both the sections parallel and perpendicular to the build direction were analysed. The electrochemical features obtained are compared to those obtained for a similar grade manufactured by ingot casting and subsequent hot working. Values of the electrochemical parameters are quite similar for all materials; open circuit potential and corrosion potential are in the range -0,25 to -0.15 V and corrosion rates in the range 4 to 5 microns/year. The shape of the electrochemical curves shows some differences once the anodic branch starts, i.e., values of potential and current density at which passivation and pitting occur. While wrought material shows a slight and continued increase of current density until pitting, the powder-based materials presented an abrupt increase in current density at the beginning of the branch, followed by a passivation state at approximately 100 A/cm2. The passivation potential value lacks repeatability in tests performed on powder-based steels.