Abstract
In the present study, the application of nondestructive evaluation to determine the characteristics of creep damage in P92 alloy was investigated. Generally, as the hold time of static load increases, the degradation of material becomes more severe with the reduction of service life. Therefore, the creep-fatigue strength and life of high-pressure vessel such as main steam pipe at high temperature is very important in power plants. Backscattering ultrasound signals were analyzed from the creep-fatigue specimens where both static and cyclic loads had been applied simultaneously. Testing temperature was 873K and a constant load level at a stress ratio of R=0.1 was applied to the CT specimen. Various trapezoidal creep-fatigue loading wave shapes with hold times ranging from 0 to 1000 s at the maximum loads were employed. The results obtained by bulk wave of focused ultrasound were compared and analyzed with the experimental parameters. The relation between parameter, the RMS level of backscattering signals and the area fraction of cavity in creep-fatigue damage zone was investigated, where the life of the damaged specimen was evaluated.
