Additive manufacturing (AM) is a rapidly evolving production technique offering entirely novel approaches towards the economic fabrication of prototype parts and the design of functional parts e.g. in space and aviation. In particular, laser powder bed fusion (LPBF) is used to manufacture metal parts by laser-induced welding of metal powder layer by layer to form parts with complex geometries. However, a deviation from the ideal process parameters and conditions may lead to an introduction of tensile stress and defects in the form of porosities severely affecting the mechanical properties of the part.

While for classical production techniques the fabrication parameters and the failure mechanisms are known in great detail, in AM there is a strong demand for research towards the understanding of causes of failure and their consequences on the mechanical properties and the lifetime of the parts. Destructive methods may be used to investigate defect structures in parts before or after failure but do not allow for e.g. a tracking of the defect evolution over time under mechanical load. Consequently, there is a strong demand for non-destructive techniques in the investigation of additively manufactured parts. In this context, most available techniques such as X-ray CT or active infrared thermography show limitations in the accessible length scales or locations of the defects. It was shown that the relatively new imaging technique known as neutron grating interferometry (nGI) provides excellent contrast even for small defects deep in the bulk of material. Moreover, nGI can additionally be used to track the growth of a defect under applied mechanical load.

With this project, we want to improve the understanding of the correlation between non-ideal process parameters, the resulting defects and their effect on the mechanical stability and lifetime of the part. You will work in close cooperation with the company INPECA, specialized in additive manufacturing to develop parts with intentionally introduced defects by alteration of various process parameters. These parts will be non-destructively investigated using neutron grating interferometry at FRM II under applied mechanical load. Additionally, to verify the results of nGI we collaborate with Hochschule Karlsruhe where the parts will be investigated after the nGI experiments by classical destructive techniques such as electron microscopy.