Hydrogen blistering and hydrogen-induced fracture of rail steel

Hydrogen blistering, hydrogen-induced plasticity loss (HIPL) under slow str ain rate test and hydrogen-induced cracking or fracture (HIC) under constan t load for rail steel were evaluated. The threshold diffusible hydrogen con centrations for blistering, HIPL and HIC were 2.03 ppm, 0.26 ppm and 0.24 p pm, respectively. During charging, blistering formed first and fissure init iated at the wall of the blistering. HIPL (I-delta) was found to decrease l inearly with the reciprocal of the diffusible hydrogen concentration (C-0), i.e. /(delta) = 105 - 27/C-0. The threshold stress for HIC (sigma (c)) in MPa decreases linearly with In C-0 in ppm i.e., sigma (c) = 642 - 284 In C- 0.