2008 年 46 巻 4 号 p. 190-199
The function of hydrogen in the embrittlement of steels has been examined with respect to plasticity involved in the fracture process. Fractographic features and effects of stress state on the hydrogen embrittlement indicate promoted crack formation by hydrogen associated with strain localization. Hydrogen also enhances the creation of vacancy-type defects during plastic deformation, and correlations are shown between the density of strain-induced vacancies and the susceptibility to the hydrogen embrittlement.
Analyses of the role of hydrogen in the fracture process have shown that hydrogen promotes the initiation of micro-cracks and reduces the resistance to the successive crack growth, being originated in vacancy formation. Interrelations between hydrogen effects in fatigue and delayed fracture have been shown, supporting the common effects of hydrogen through enhanced creation of vacancies.
Various models of the mechanism of hydrogen embrittlement have been briefly and critically reviewed. Characteristic features of hydrogen embrittlement are the best explained with the hydrogen-enhanced strain-induced vacancies model that claims the primary role of vacancies rather than hydrogen itself in the embrittlement.