Corrosion fatigue of a 12%Cr low pressure turbine blade steel in simulated service environments

An investigation has been carried out to examine the corrosion fatigue performance of a 12%Cr stainless steel in simulated service environments. Uniaxial, constant amplitude load control fatigue tests were performed in de-ionized water at 120 °C with zero and 4 ppm oxygen, zero and 1 ppm chloride. The effect of frequency is also examined and its effect on the fatigue life of the material is discussed. The results showed that when compared with air data at the same temperature the fatigue strength is reduced, the reduction being greater with increasing oxygen content. Although no evidence of pitting was found in the zero and 4 ppm oxygen environments, some differences were found in the fracture appearance, which are discussed. Failure in chloride containing environments was found to occur from corrosion pits, although the application of a stress was found to be a necessary part of the initiation process. Static load tests indicated that this stress needed to be cyclic, suggesting the dominant failure mechanism is that of corrosion fatigue.