Evaluation of ultrasonic test indications of creep damages in high temperature pressure parts of power plants

It is well known that high temperature components working in the creep range undergo material degradation to a noticeable extent after the designed life. In some instances the damage occurs in the form of creep pores and grain boundary creep cracks as a result of dislocation interactions. The intrinsic micro defects in localized regions affect the propagation of ultrasonic waves. The reflected ultrasonic echoes and the attenuation pattern of indications from different stages of crept materials followed a pattern that would enable to obtain a correlation to the severity of creep damage. This devised approach helps in-situ characterisation of components. A comparative damage evaluation of serviced plant components by metallography agrees fairly well with the ultrasonic evaluation.