Suppression of Hydrogen-Assisted Fatigue Crack Growth in Carbon Steels

Carbon steels with high resistance to hydrogen-assisted fatigue crack growth were successfully produced by addition of a carbide forming element and refinement of ferrite grain size. In carbon steels containing vanadium (V), titanium (Ti) or niobium (Nb), fine carbide (VC, TiC or NbC) precipitation and the refinement of grain size below 1 μm was achieved by caliber rolling at 833 K. In standard JIS-S45C carbon steel, hydrogen charging increased the fatigue crack growth rate to about 25 times that of non-charged steel. In contrast, for carbon steels containing carbide forming elements, the hydrogen-assisted fatigue crack growth was either absent or at most two times as fast as that of non-charged steels.