Technique improvement for crack depth estimation of steam generator tubes

A review of non-destructive techniques for the detection of creep damage in power plant steels

“…Unlike other ultrasonic techniques, backscatter can be used for the evaluation of localised creep: destructive metallographic analyses of crept specimens, including weldments, confirmed in each case that the most damaged areas were those highlighted by this method [72][73][74]. Accurate positioning of the sensor is vital in this case, and the surface often needs to be ground and etchedalthough not to the degree required by replication -in order to locate the weld.…”

“…Material noise due to inhomogeneities can cause large errors at early stages, while coarsening of precipitates and other microstructural changes due to thermal ageing can affect the results obtained with this method [72]. However, a detectably greater backscatter is produced by the development of micro-and macrocracks in the final stages of creep life [73,74].…”