Effect Of Pits On Fatigue Strength Of Carbon SteelIn Oxygenated High Temperature Water

Abstract

Most of corrosion fatigue tests have been carried out using polished specimens in high temperature water and these data have been used for the evaluation of actual component. Since degradations of surface such as corrosion or corrosion pit are induced during long period of operation, the surface of actual component may be different from that of polished specimen. Previous study showed that the fatigue strength of pre-corroded specimen of carbon steel was substantially reduced in oxygenated high temperature water [1]. This kind of effect should be considered for the accurate evaluation of fatigue strength of actual component. Strain-controlled fatigue tests on carbon steel were carried out in 290°C water with 8ppm dissolved oxygen. Test specimens were polished specimen and artificially pitted specimens with various shapes which simulated corrosion pit. Test results showed that the fatigue strength of the specimen with artificial pit decreased with an increase of the pit size and was influenced by the shape of pit. The relation between the fatigue strength and the size and shape of pit was discussed.