Non-destructive testing for wire + arc additive manufacturing of aluminium parts

Abstract

Wire + Arc Additive Manufacturing (WAAM) has already proven to be successful for the production of large metal parts. However, there are still no specific standards available to label the quality requirements of the parts produced by WAAM and this is preventing a more widespread adoption of the technique.A crucial step towards the quality assurance of WAAM parts will be the development of Non-Destructive Testing (NDT) systems capable of identifying defects while parts are being produced. In this regard, Eddy Current Testing (ECT) can play a significant role, by allowing the inspection of both ferromagnetic and non-ferromagnetic materials, with high speeds and without contact with the material surface. The limitation here is that commercial ECT targets only the inspection of surface and subsurface defects.This study is focused on the development of a NDT system which includes customized ECT probes for the inline layer-by-layer detection of defects in aluminium WAAM samples. Results revealed that the developed EC probes were able to locate artificial defects: at depths up to 5 mm; with a thickness as small as 350 μm; with the probe up to 5 mm away from the inspected sample surface.The developed ECT probes proved to surpass the limitation of commercial ones. Also, these probes were able to overcome the limitations caused by the surface roughness of the samples and the high temperatures involved in the deposition process. These preliminary results represent an important step for the development of NDT systems for WAAM.