3. Gas diffusion in metals

The interaction of a gas with a metal plays an important role in many fields of metallurgy, independently of the industrial processes widely used for surface treatments (carburizing, nitriding).

In fact, during processing, a liquid metal can dissolve significant quantities of gases (hydrogen, oxygen) which are not necessarily subsequently eliminated. This can have particularly harmful effects, such as embrittlement (zirconium, titanium due to oxygen, iron due to hydrogen), porosity (flakes) and reverse segregation.

Hydrogen's action on steels has been the focus of particular attention, as it leads to a rapid drop in mechanical properties, reducing the steel's ductility. Hydrogen can originate either in the very early stages of steelmaking, through the presence of moisture, or through cathodic hydrogen loading during electroplating (surface...