Abstract :
This paper explores the effects of hydrogen
on the mechanical properties of a 2 1/4Cr–1Mo steel.
The results for both microstructural conditions, as
received and aged, indicated a loss of ductility after
hydrogen charging treatment, but the yield strength
and ultimate tensile strength remained unaltered. The
fractograph analysis revealed that the fracture mode
was modified by the hydrogen. The steel in the
as-received condition showed craters and fisheyes on
the fracture surface. The aged steel showed a brittle
appearance associated with cleavage facets and small
portion of areas with dimples. The hydrogen diffusivity
and solubility were investigated using electrochemical
permeation technique. It was observed that the hydrogen
diffusivity decreased from 2.3 ± 0.4 · 10–10 m2 s–1
in the as-received condition to 5.7 ± 0.1 · 10–11 m2 s–1
in the aged condition. The hydrogen solubility showed
an increase for the aged condition in comparison to
the as received sample. Both phenomena can be
attributed to carbide evolution during aging, resulting
in an increase of the carbide/matrix interfacial
area.
