Characterization of creep damage by means of ultrasonic techniques

The assessment of creep damage in structural components has become important in order to improve the reliability and safety of power stations. In many high-temperature steels creep damage starts with cavity formation. Nondestructive detection of this kind of damage requires techniques which are very sensitive to porosity. The potential of using ultrasonic techniques for this purpose is evaluated both theoretically and experimentally. Measurements were performed using service-exposed ferritic material (14 MoV 6 3) as well as austenitic loaboratory specimens (Alloy 800H). Results abtained show that measurement of ultrasonic velocity is a promising technique for characterization of creep porosity and could possibly be used for the in-service detection of creep damage in components such as pipings at an relatively early stage. (IZFP)