Experimental investigation of ultrasonic immersion testing for complex-geometry additively manufactured 316 L stainless steel

This paper presents a case study of immersion ultrasonic C-scan inspection of a single fatigue-cracked laser powder bed fusion 316 L stainless steel double-hourglass specimen, relevant to the qualification of additively manufactured components for nuclear power plant applications. Ultrasonic testing of complex-shaped additively manufactured 316 L components presents particular challenges, especially for contact testing methods. Scans were performed from four lateral faces (0°, 90°, 180°, and 270°). The results show that the crack is successfully detected from the two flat-face views (0° and 180°), whereas the echo signals from the two curved-face views (90° and 270°) are dominated by geometric beam deflection, mode conversion, and amplitude loss, producing unreliable ultrasonic images. The crack detection is confirmed by Penetrant Testing.