Application of fracture mechanics to hot corrosion creep failure

High temperature Fracture Mechanics Parameter - the energy rate line integral C*, has been extended to analyse the creep rupture life prediction of stainless steel and super alloys in the presence of hot corrosion. Creep life is mainly due to the growth of voids along the grain boundaries. When the void size reaches a critical value, the remaining grain boundary area is not able to sustain the applied load, the net section stress reaches the grain boundary ultimate strength, and failure occurs. In the presence of hot corrosion the corroding species diffuse through the grain boundaries and the corroded boundary becomes weak. Thus the grain boundary strength sigma(o) is reduced to sigma(oc) and in such a situation, a small size void will be sufficient to result in the failure of the material. Thus, combining the void growth due re, creep and the reduction in grain boundary strength due to hot corrosion, a model has been proposed to estimate the creep rupture life. The predicted creep rupture life has been compared with the experimental results carried out on Type 304 stainless steel. Nimonic 80A and Superni 600 super alloy in the temperature range of 600 degrees C - 700 degrees C in the corrosion medium of sodium sulphate and sodium chloride. The correlation appears to be very good and the model can be used to predict the remaining life of high temperature service components.