Nanomechanical characterization of the hydrogen effect on pulsed plasma nitrided super duplex stainless steel

Pulsed plasma nitriding (PPN) is used to nitride super duplex stainless steel (SDSS). Different analytical techniques are used to characterize the nitride layer on both ferrite and austenite phases existing in the SDSS. In-situ electrochemical nanoindentation is used to examine the effect of electrochemically charged hydrogen on the mechanical properties of both the SDSS substrate metal and the nitride layer. By applying this method, we were able to trace the changes in the mechanical properties due to the absorption of atomic hydrogen. The results clearly show that the hydrogen charging of the nitriding layer can soften the layer and reduce the hardness within both the compound and diffusion layers. The effect is completely reversible, and removal of the hydrogen causes the hardness to recover to its original value. The findings show that nitriding is a promising way to control the hydrogen embrittlement of SDSS.