Microstructural trapping effects on hydrogen induced cracking of a microalloyed steel

Abstract

The susceptibility of a Ti microalloyed HSLA steel to internal hydrogen induced cracking has been correlated with the hydrogen trapping character of the microstructure. Both of these properties are influenced by aging reactions which determine the type and extent of carbide precipitation as well as metalloid segregation to grain boundarie. In turn, crack path susceptibility and total trapping character determine in large part the threshold and steady-state cracking propensities. Thus, metalloid segregation concurrent with potent irreversible trap (TiC) precipitation results in low inherent toughness, but no appreciables drop in threshold stress intensity. Conversely, cementite precipitates formed at lower aging temperatures provide potent crack initiation sites in the absence of deep trapping, resulting in a lower threshold for cracking.