Hydrogen related failure of steels – a new aspect

Recent studies of the characteristics and mechanism of hydrogen related failure in steels are overviewed. Based on an analysis of the states of hydrogen in steels, the role of hydrogen in reducing ductile crack growth resistance is attributed to the increased creation of vacancies on straining. Cases showing the involvement of strain induced vacancies in susceptibility to fracture are presented. The function of hydrogen is ascribed to an increase in the density of vacancies and their agglomeration, rather than hydrogen itself, through interactions between vacancies and hydrogen. The newly proposed mechanism of hydrogen related failure is supported by a recent finding of amorphisation associated with crack growth.