Non-destructive characterization of plasma-sprayed tungsten and braze-joints for fusion by ultra-sonic examination

• Published in: Fusion engineering and design 1998-01, Vol.42 (1), p.511-517
• Main Authors: Šmid, I., Kny, E., Scheerer, M., Hahn, P.A., Korb, G., Linke, J., Vieider, G.
• Format: Article
• Language: English
• Subjects: Applied sciences; Controled nuclear fusion plants; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Installations for energy generation and conversion: thermal and electrical energy
• ISSN: 0920-3796; 1873-7196
• DOI: 10.1016/S0920-3796(98)00327-5

High resolution non-destructive ultra-sonic testing has been applied for the characterization of joints and bul materials. The measurements were carried out with an ultra-sonic inspection system of the type Panametric Multiscan TM equipped with a four axis motorized manipulator for positioning the transducer (actuator/receiver unit). For scanning, the system is operated in pulse-echo mode, the desired penetration depth is adjusted by choosing the corresponding time window when recording the reflected signal. Transducer frequencies 5–100 MHz are available. A very fine resolution is achieved, with 100 MHz voids or pores in copper down to a size of 25 μm can be detectec Presently, objects can be scanned up to a dimension of 500 mm in steps ≥ 10 μm. Data acquisition and post processing is performed on a PC with a 1 GHz sonix digitizer card. By ultra-sonic inspection not only individual defects in fully dense materials, but also regions of higher or irregular porosity, such as in plasma sprayed coatings can be detected. To eliminate interference with the residual porosity, the resolution needed for detection can be selected with the transducer frequency. By the use of a special transducer the Cu tube and braze interface in CFC armored divertor modules of monoblock geometry (‘tube-in-tile’) was examined successfully. For the first time it is possible to inspect in-vessel components for fusion non-destructively from the inside of the coolant channel—befor high heat flux loading, reproducibly and reliably mapping all pores and imperfections down to ∼ 125 μm in size (when using 20 MHz working frequency).