Effect of boric and oxalic acid additions on fatigue phenomena in selected stainless steels in high purity water

Corrosion fatigue was tested in three austenitic steels, viz., CSN 17 246.4 (7-10% Mn, 17-20% Cr, 8-11% Ni), CSN 17 460 (7-10% Mn, 17-20% Cr, 4-6% Ni) and AKRI (21% Cr, 32.8% Ni) considered as material for primary circuit pumps of PWR reactors. Demineralized water with an addition of boric acid (14 g/l) or oxalic acid (30 g/l) at a temperature of 20 and 90 degC was used as the corrosion medium. Bending tests were conducted at a rotation rate of 6000 r.p.m. Boric acid was found to cause only a slight deterioration of fatigue properties of materials CSN 17 246.4 and AKRI. Oxalic acid deteriorated the properties by about 30%. An analysis of fracture appearance showed that the appearance approaches that under air. An exception was the fracture of steel CSN 17 460 where a number of initial cracks could be seen. (Ha)