The effect of temperature on corrosion fatigue crack propagation in reactor pressure vessel steels

The current procedures for assessment of sub-critical crack growth rates in ferritic steel pressure boundary components embodied in the ASME XI Appendix A code do not include temperature as an important variable and most of the supporting database was obtained at 290 degrees C. However, there is mounting evidence that fatigue crack growth curves in water are temperature dependent in terms of both threshold and plateau growth rate. There is also reported evidence of a mechanism change in crack growth at approximately 175 degrees C. This paper reviews the key observations on temperature effects, with discussion of possible rate controlling mechanisms. A new model which incorporates temperature effects into the crack velocity assessment method is presented