Evaluation of the phased array transmit-receive longitudinal and time-of-flight diffraction techniques for inspection of a dissimilar weld

Abstract

The use of two phased array techniques for the inspection of a representative dissimilar weld from the power industry was investigated. The performance of the phased array Transmit-Receive Longitudinal (TRL) and Time-of-Flight Diffraction (TOFD) techniques was compared to the best-practice baseline procedure using conventional ultrasonics, developed specifically for the nozzle component. Slots were implanted in several regions (parent, HAZ and austenitic weld body) under a layer of cladding. The performance criteria were the detection of the slots, through-wall sizing and signal-to-noise. Both phased array techniques performed better than the conventional techniques with regard to sizing, satisfying the ASME Boiler and Pressure Vessel Code (1) (2007) Section XI Appendix VIII. The Root Mean Square (RMS) error of the phased array TRL and TOFD techniques were 0.52 and 1.04 mm, respectively. In addition, the phased array techniques showed similar signal-to-noise performance to the conventional transducers, which were matched to the curvature of the inspection surface. Based on these results, the use of phased array techniques for the inspection of thick ferritic-austenitic dissimilar welded components is recommended, confident in their ability to outperform conventional techniques.