Microstructure and corrosion behavior of AISI 316L duplex treated by means of ion nitriding and plasma based ion implantation and deposition

Abstract

Austenitic stainless steels are the preferred materials for mechanical components in the food, oil and chemical industries due to their good corrosion resistance but they often suffer severe wear due to their poor tribological properties. Plasma surface engineering has been extended to stainless steel hardening, through the modification of the surface with ion nitriding or the application of hard coatings. In this work, AISI 316L samples were coated with titanium nitride by means of a cathodic arc (CA) and this technique was combined with plasma immersion ion implantation, in a process called plasma based ion implantation and deposition (PBII&D). The effect on corrosion resistance was analyzed, also considering ion nitriding as a pre-treatment. Microstructure and composition were analyzed by means of glancing angle XRD, SIMS, SEM, SEM-FIB and EDS. Localized corrosion resistance was analyzed in a cyclic potentiodynamic polarization experiment in 3.5% NaCl solution, and the corroded surface was analyzed with AFM, SEM and EDS as well. It was found that nitriding at 400 °C produces a thin nitrided layer with good corrosion resistance. A duplex TiN coating resulted in a further improvement of the corrosion resistance. Comparing cathodic arc and PBII&D coating techniques, the last one gives the thickest film and also the best corrosion behavior with good adhesion.