Paper 23

Abstract
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 steel creep damage starts with cavity formation. Nondestructive detection of this kind of damage requires techniques which are very sensitive to porosity. The potential of ultrasonic techniques for this purpose is evaluated both theoretically and experimentally. Measurements were performed using service-exposed ferretic material (14 MoV 6 3) as well as austenitic laboratory specimens (Alloy 800H). Results obtained show that measurements of ultrasonic velocity is a promising technique for characterisation of creep porosity and could possibly be used for the in-service detection of creep damage in components such as pipings at a relatively early stage. (IZFP)