Phase Mapping of Ultrasonic Fields Passed through Centrifugally Cast Stainless Steel

Mapping of ultrasonic fields passed through various solids has been used as an engineering tool to measure field distortion [1–8]. Centrifugally cast stainless steel (CCSS) has been one material of interest since many pressurized-water reactors (PWRs) use this material in the primary pressure boundary. The two-dimensional mapping of amplitude has been performed in different CCSS microstructures, and it was also of interest to extend this capability to include phase. This data was thought to be useful in validating models which are being refined to predict ultrasonic fields in solids, compensating for phase distortion when imaging reflectors, and detecting flaws by detecting changes caused by interference between the phase response of the primary wave front and a flaw. Previous work indicated that the sound field emitted by a 45°, longitudinal-wave probe was distorted at a frequency of 2 MHz but not at 1 MHz [2]. This report discusses the samples used, the process of mapping the in-phase fringe pattern, and an analysis of the fringe patterns acquired from selected CCSS microstructures at frequencies of 1 and 2 MHz