Hydrogen embrittlement of a bainitic wheel steel

The effects of hydrogen charging on the strength, plasticity, fracture toughness and hydrogen induced delayed cracking (HIDC) of a bainitic wheel steel were investigated. The results showed that the critical diffusible (C*(0)) or total (C*(T)) hydrogen concentration for forming flaking were C*(0)=1.5 +/- 0.3 ppm and C*(T)=3.4 +/- 0.5ppm, respectively. Atomic hydrogen had no effect on the fracture toughness extended with normal strain rate. Hydrogen, however, had the effect of reducing the plasticity during slow strain rate tests, and induced delayed failure under constant displacement. The threshold stress intensity factor of hydrogen induced delayed cracking, K-IH, decreased exponentially with the diffusible hydrogen concentration C-0, i.e. K-IH(MPam(1/2))=28+81exp-2C(0)(ppm) (0.4 <= C-0 <= 3.4). And the crack propagating rate increased exponentially with the diffusible hydrogen concentration i.e. nu(mm/min)=0.01+0.0013exp1.5C(0)(ppm) (0.4 <= C-0 <= 3.4).