Non-destructive testing of welded joints of 12Kh18N10T steel made by selective laser melting

The dimensions of products obtained by additive technologies are limited by the working chamber of the 3D printer. The solution to the problem of scaling products is possible through a combination of additive methods and laser welding. The paper presents the results of quality assessment of welded joints using non-destructive testing methods. The objects of the study were plates made of corrosion-resistant steel 12Kh18N10T (AISI 321) measuring 100 × 100 × 5 mm and pipes with a wall thickness of 6 mm, manufactured by selective laser melting. X-ray computed tomography, digital radiography and ultrasonic testing were used to analyze defects. It was shown that the presence of pores and lack of fusion in welded workpieces leads to the occurrence of local porosity in the weld. The digital radiography revealed the difference in the formation of negative and positive contrast of radiographs. Digital post-processing methods were applied to improve the quality of radiographs (increase in image contrast by 7 – 8 times) and to increase the detection of defects. It was established that the ultrasonic testing method allows for the qualitative determination of the presence of defects in a welded joint, but does not provide a quantitative assessment of their characteristics due to the strongly expressed anisotropy of the acoustic properties of the material. The obtained results can be used to solve the general problem of quality control of additive manufactured products, in particular, in the control of welded joints of corrosion-resistant chromium-nickel steels for aerospace products.

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