Evaluation of Welding Imperfections with X-ray Computed Laminography for NDT Inspection of Carbon Steel Plates

Abstract

X-ray computed laminography is a depth-resolving non-destructive testing technique well suited for the non-destructive examination of large and flat structures where traditional computed tomography is impractical. This technique provides 3D radiographic imaging and characterization with depth information of welding imperfections in welded components, ensuring component quality meets the standard criteria and safety purposes. Furthermore, determining the welding imperfection’s location in fabrication, in-service and maintenance is crucial for welding repair, resulting in the areas where the repair work needs to be started. This work highlights the characterization of welding imperfections by experimental digital radiography with digital detector array (RT-D with DDA) and coplanar translational laminography (CTL) techniques applied to welded carbon steel plates. A test specimen was tested, specially prepared with artificial planar and volumetric flaws like lack of fusion, clustered porosities and slag inclusions with varying dimensions and the approaches were analyzed. Additionally, a test phantom was fabricated with known geometry features that access the CTL system’s optimal detection accuracy to demonstrate a broad functionality and acceptance of the CTL system for depth information in the plate-like structures. The coplanar translational laminography technique provides advantages for characterizing welding imperfections and testing phantom features with high contrast and acceptable image quality. The result is confirmed by the phased array ultrasonic testing and RT-D with DDA. The exposure conditions, image sensitivity, and quality are analyzed according to ISO 17636-2 to ensure compliance with industry standards in digital radiography.