The dual role of shot peening in hydrogen-assisted cracking of PSB1080 high strength steel

Abstract

The influence of shot peening (SP) treatment on reversible and irreversible hydrogen embrittlement of PSB1080 steel was investigated using slow strain rate tensile tests and electrochemical hydrogen charging-induced cracking tests, respectively. The results demonstrate that SP plays the dual role in hydrogen-assisted cracking. On the one hand, the resistance to hydrogen embrittlement increases as the SP pressure increases for reversible hydrogen embrittlement. This is ascribed to the fact that the shot peening layer acts as a barrier from hydrogen invasion, which is illustrated by hydrogen permeation tests and fracture surface observation. On the other hand, the susceptibility to hydrogen-induced cracking increases with an increase in SP pressure for irreversible hydrogen embrittlement. The crack initiation is associated with inclusions rich in O, Fe, Al and Si or in O, Fe, Si and S for no shot peening sample, while for SP specimen both inclusions and crater rim serve as crack origins. In addition, the hydrogen-induced crack path exhibits a long strip shape for no shot peening sample, whereas the branch-type cracks are observed in SP specimens.