Corrosion properties of stainless steel 316 L after energetic nitrogen insertion

Abstract

Using a pulse low energy ion implantation with an electronic beam switch operating in the kHz regime, a more efficient nitriding process is possible than with either pulsed plasma immersion ion implantation (PIII) or continuous low energy ion implantation (LEII). Using such an experimental setup, it is shown that the pulse length modulation (PLM) itself produces a slight beneficial effect on the corrosion behaviour of austenitic stainless steel 316 L at 400 °C. However, differences in the diffusion and phase formation exist. For 5% PLM, a lower nitrogen flux resulted in the formation of expanded austenite with a very low lattice expansion, while the highest PLM (40%) led to a reduced layer thickness caused by higher sputtering induced by the increased ion bombardment itself. Nitriding at 400 °C increases the corrosion resistance of 316 L stainless steel for all PLM. The effect is more pronounced for 15 and 30% PLM.