INSPECTION OF AUSTENITIC WELD WITH EMATS

Nondestructive testing of austenitic welds is very important for nuclear, petrochemical, and many other industries. Due to the strong material anisotropy and coarse grain size in the dendritic weld zone, shear horizontal (SH) wave mode is much superior to conventional shear vertical (SV) and longitudinal wave modes. In this paper, an electromagnetic acoustic transducer (EMAT) is designed and used for the inspection of two austenitic weld samples. Compared with piezoelectric transducers, EMAT has lower efficiency in sound generation due to low conductivity of austenitic stainless steel material and strong attenuation in the weld zone. However, using our EMAT probe and cutting edge pulser and receiver, good signal to noise ratio is achieved in our testing. The angle beam EMAT probe successfully detected all defects in the samples with good signal to noise ratio including a 2% defect. The capability of detection a defect across a 2″ inch thick and 2″ wide austenitic weld zone is also demonstrated in the paper.