Abstract
The effect of hydrogen on fatigue crack growth behavior was investigated in SUS630 with hydrogen-charged specimens at different test frequencies. The fatigue crack growth rate was increased by hydrogen-charge. The fatigue crack growth rate of the hydrogen-charged specimen increased with decreasing test frequency from 20 Hz to 0.2 Hz. The fatigue crack path became thinner by hydrogen-charge. It was presumed to be caused by localization of slip at the crack tip by hydrogen. These factors cause the acceleration in fatigue crack growth rates in the hydrogen-charged specimens. Fatigue fracture surface observation shows that, in the hydrogen-charged specimens, there were a lot of circular-shaped patterns which were presumed to be formed by synergistic effect of cyclic loading and hydrogen concentration ahead of the main crack with a strong hydrostatic tension at the higher ΔK region. The coalescence of the main crack with advanced small cracks also causes the acceleration of fatigue crack growth rates in the hydrogen-charged specimens at the higher ΔK region.
