Evidence that shot peening mitigates hydrogen embrittlement in quench and tempered steel

Abstract This study explores the effects of shot peening on hydrogen-induced degradation by examining residual stress evolution and fracture behavior in a quench -and tempered medium carbon steel. Shot-peened specimens were subjected to cathodic hydrogen charging, and properties were assessed after allowing hydrogen to outgas over 72 h. Hydrogen charging relaxes compressive residual stresses due to peening; nevertheless, shot-peened samples exhibited substantial ductile fracture after charging durations from 24 to 72 h. In contrast, unpeened specimens show a transition toward more brittle fracture as hydrogen charging time increased. The difference in hydrogen embrittlement response between the unpeened and peened specimens likely arises from the dominant embrittlement mechanisms in each condition. Hydrogen-enhanced decohesion (HEDE) appears to dominate in unpeened samples, while hydrogen-enhanced localized plasticity (HELP) is the more impactful mechanism in the peened samples with a high dislocation density, resulting in less reduced ductility compared to the unpeened counterparts when hydrogen is present in solution. Graphic Abstract