抄録
The corrosion fatigue (CF) crack growth behavior of a duplex (α and γ phases) stainless steel, SUS329J1, weldment has been investigated in ASTM synthetic seawater (SSW) at the free corrosion potential and the cathodically charged potential of -957mV vs. Ag/AgCl. The tests were conducted with a sinusoidal load at stress ratios of 0.1 and 0.8 with stress cycle frequencies of 0.17Hz and 10Hz. The CF crack growth rate of the weld metal in terms of stress intensity factor range, ΔK, was considerably lower than that of the base metal, since a crack opening load was increased by the compressive residual stress by welding. In air tests, the crack growth rate of the weld metal in terms of the effective stress intensity factor range, ΔKeff, or a modified one, ΔKcont, was larger than that of the base metal, because the acceleration of the growth rate by nonmetallic inclusions in the former is more prevailing than in the latter. At low ΔKcont at the free corrosion potential, the crack growth rate of the weld metal, which was accelerated by the inclusion and hydrogen embrittlement (HE), was higher than that of the base metal, which was accelerated by dissolution. On the other hand, at high ΔKcont at f=0.17Hz of R=0.1 at the free corrosion and the cathodically charged potentials, the growth rate of the weld metal was lower than that of the base metal, since the base metal with lower area ratio of γ phase was more sensitive to HE than that of the weld metal.
