Evaluation of inspection capability for SCC by 3D-SAFT UT method in Ni alloy weld

Stress Corrosion Cracking (SCC) phenomena in the nickel alloy weld have been increased in Japan and in worldwide recently. But it is well known that the detection and depth sizing of SCC by UT is difficult in Ni alloy weld because of the strong anisotropy of metallurgical structure of weld and the complicated morphology of SCC. New UT technique which uses three dimensional synthetic aperture focusing technique (3D-SAFT) has been applied to Ni alloy dissimilar metal weld (DMW) which had EDM notches and SCCs. It was verified that the 3D-SAFT UT technique has the superior capabilities about the imaging of the shape of SCC, the depth sizing possibility, and the depth sizing accuracy. The improvement of inspection capability which was carried out from the oblique direction to the SCC has been verified in order to reduce the un-inspected region. Furthermore the fundamental development of high temperature application of 3D-SAFT has been carried out. (author)