Fatigue strength correction factors for carbon and low-alloy steels in oxygen-containing high-temperature water

Strain-controlled fatigue tests were conducted on carbon and low-alloy steels in high-temperature water containing controlled amounts of oxygen, in order to determine quantitatively the reduction of fatigue strength due to factors such as the strain rate and the environmental testing conditions such as temperature and dissolved oxygen content. For each of these factors, the effect on fatigue strength was separately quantified and parametric equations were derived with reference to the basic fatigue curve obtained in air at room temperature. Using the formulas thus obtained, generalized expressions for predicting the expected fatigue life of a given material under specified combinations of strain amplitude and environmental conditions were deduced. Based on these generalized expressions, 'fatigue strength correction factors for environmental effects' are proposed, which can be conveniently used in combination with the design fatigue curve given in the ASME Boiler and Pressure Vessel Code, Section III, to account for fatigue strength reduction under severe service conditions. (orig.)