Nondestructive evaluation of creep damage in service exposed 14 MoV 6 3 steel

Ultrasonic techniques as well as electrical resistivity measurements were applied to assess the degree of creep damage in 14 MoV 6 3 steel (0.5 Cr, 0.5 Mo, 0.25 V). Samples were cut from a tube bend which had failed after 130,000 h/535 degrees C service exposure providing us with a complete variety of damage states. Using metallographic methods the microstructural damage was classified in terms of micropore concentration and microcrack formation, respectively. The actual porosity of the material was determined quantitatively by density measurements. The obtained results show that both ultrasonic velocity (longitudinal waves, shear waves, and surface waves) and electrical resistivity can be used for damage characterization whereas ultrasonic attenuation measurements did not prove to be appropriate in this case. The experimental results are in good agreement with theoretical predictions. Especially ultrasonic velocity measurements seem to have a high potential for practical applications. (IZFP)