Effect of in situ hydrogen charging on the pulsed plasma nitiding layer in stainless steels

In many subsea components, use of stainless steels alloy has been increased. But hydrogen entrapment resulting from external cathodic protection, combined with a certain stress/strain level causing atomic hydrogen entering into the alloy and it can weaken the mechanical strength of the alloy, cause cracks and destroy the integrity of equipment or a system. Pulsed plasma nitriding is a possible solution to coat the components to reduce the hydrogen intake an also reduces wear and galling. In this work nitride layers on stainless steel were examined by means of nanoindention method at different loads. Additionally in situ electrochemical nanoindentation technique is used to electrochemically charge the samples in situ and investigates the effect of hydrogen on mechanical properties. In this method changes in the plasticity and in the hardness due to the absorption of atomic hydrogen has been traced.