An investigation on the suitability of modern nondestructive testing methods for the inspection of specimens manufactured by laser powder bed fusion

• Main Authors: Cara G. Kolb, Katja Zier, Jan-Carl Grager, Andreas Bachmann, Tobias Neuwirth, Simon Schmid, Maria Haag, Markus Axtner, Fabian Bayerlein, Christian U. Grosse, Michael F. Zaeh
• Format: Article
• Language: English
• Published: Springer 2021-06-01
• Series: SN Applied Sciences
• Subjects: Laser powder bed fusion (L-PBF); Defect detection; Active infrared thermography imaging (aIRT); Neutron grating interferometry (nGI); Computed tomography (CT); Ultrasonic testing (UT)
• Online Access: https://doi.org/10.1007/s42452-021-04685-3

Abstract Laser powder bed fusion (L-PBF) is increasingly used to fabricate functional parts used in safety-relevant applications. To ensure that the sophisticated part specifications are achieved, 100% quality inspections are performed subsequent to the buildup process. However, knowledge about the detectability of defects in L-PBF parts using NDT methods is limited. This paper analyzes the suitability of NDT techniques in an ex situ environment, in particular active infrared thermography, neutron grating interferometry (nGI), X-ray computed tomography, and ultrasonic testing for the examination of L-PBF parts made from Inconel 718. Based on a test specimen with artificially inserted defects with varying dimensions and depths, these NDT techniques were compared in terms of their attainable resolution and thus defect detection capability. The empirical studies revealed that nGI shows the highest resolution capability. It was possible to detect defects with a diameter of 100–200 m at a depth of 60–80  $${\upmu } \hbox {m}$$ μ m . The results are discussed with regard to their relevance for the examination of L-PBF parts and thus not only contribute to a better understanding of the potential of the NDT techniques in comparison but also assist stakeholders in additive manufacturing in evaluating the suitability of the NDT techniques investigated.