Scientists from University College London (UCL) and the Central Laser Facility (STFC) have worked together to invent new instrumentation and methods to study vapour plumes during metal additive manufacturing. Their research is now published in Advanced Science.
The process of Laser Powder Bed Fusion (LPBF) presents a huge opportunity for manufacturing, as it allows a great deal of design freedom and complexity when 3D-printing metal components. However, a high degree of accuracy and reliability is needed, especially when creating components for the aerospace or biomedical sectors.
During LPBF, small faults like pores or cracks can undermine the reliability of a component, and these have been widely studied. One aspect that is not well understood is how metal vapour produced during the manufacturing process may affect the alloy composition, and ultimately the quality of the component.
We know that LPBF can result in ‘preferential vaporisation’ – which means that one element is vaporised at a faster rate – resulting in a final product with a different chemical composition to the material you started with. To make things more complicated, there are different melting modes used in LIBS, all of which may produce vapour in slightly different ways.
Working at high temperatures and with an active laser, it’s difficult for researchers to analyse the composition of vapour during the manufacturing process. Existing methods, such as synchrotron X-ray radiography, are effective for studying the materials in their solid and liquid form, but struggle to cope with the lower-density gaseous vapour. The team, led by Dr Anna Getley and Dr Chu Lun Alex Leung, have been working on new instrumentation to tackle this challenge.
Thanks to their base at the Research Complex at Harwell, they teamed up with the Central Laser Facility’s Professor Mike Towrie to develop a high-speed Laser-Induced Breakdown Spectroscopy (LIBS) device. This breakthrough required extensive calibration and the creation of custom signal processing techniques.
Using the new LIBS system, the team performed experiments to study the plume composition in situ during LPBF process, providing proof of concept and validating results from computer simulations.
The project formed part of Dr Getley’s PhD studies, aimed at developing novel instrumentation and analytical methods to minimise metal vaporisation. Her research group – Multiscale X-ray Imaging (MXI) Lab at UCL – is supported in this work by EPSRC and by IPG Photonics.
Dr Leung adds:
‘The next step is that we’ve filed a patent based on this work, and we’re developing ways to push this technology to industrial applications. We’re also supervising PhD students and post-doctoral researchers to further develop this technology.’
Read the full research article here.
