Fatigue crack propagation characteristics of submerged arc weldment material in a simulated PWR environment at the outlet coolant temperature

The present work compares the fatigue crack growth data for A508 Cl.III material in a high and low bulk sulphate PWR water environment at 325°C, the PWR coolant outlet temperature. Through careful fractography and a knowledge of the non-metallic sulphide distribution, it emerges that environmentally assisted crack (EAC) growth exhibiting plateau growth behaviour mainly occurs, irrespective of sulphate level over the range 70 ppb (10⁻⁹) to 1000 ppb and chloride level over the range 40 to 300 ppb, when a growing fatigue crack encounters large non-metallic sulphide inclusion clusters.