Study on creep cavity morphology of P91 power plant steel by industrial computed tomography

Abstract

P91 steel is widely used in high temperature components of ultra supercritical thermal power units, whose high steam parameters can improve the thermal efficiency. Creep cavities can be used to evaluated the creep damage state of the P91 power plant steel. In this study, industrial computed tomography (CT) tests were conducted on the crept P91 steel sample. It was found that the digital radiography (DR) and CT images using 12 W target power exhibited clearer internal defect morphology than that of the images taken with 80 W target power, because the relatively low target power kept the focal spot small. In addition, combined the CT images along radial and axial directions, the creep cavities of P91 steel were judged as long strip volume defects with ~50 μm diameter along the stress direction, demonstrating that the industrial CT testing method could be applied to defect detection of other power plant materials.