Microstructural characterization of pulsed plasma nitrided 316L stainless steel

Pulsed plasma nitriding (PPN) treatment is one of the new processes to improve the surface hardness and tribology behavior of austenitic stainless steels. Through low temperature treatment (<440 °C), it is possible to obtain unique combinations of wear and corrosion properties. Such a combination is achieved through the formation of a so-called “extended austenite phase”. These surface layers are often also referred to as S-phase, m-phase or γ-phase. In this work, nitrided layers on austenitic stainless steels AISI 316L (SS316L) were examined by means of a nanoindentation method at different loads. Additionally, the mechanical properties of the S-phase at different depths were studied. Electron back-scatter diffraction (EBSD) examination of the layer showed a high amount of plasticity induced in the layer during its formation. XRD results confirmed the formation of the S-phase, and no deleterious CrN phase was detected.