Shedding new light on laser additive manufacturing

Figure 1: The Additive Manufacturing Team from the Research Complex at Harwell on the Joint Engineering Environment Processing (JEEP, I12) beamline. The Laser Additive Manufacturing Process Replicator (or LAMPR) on the right is used to reveal the underlying physical phenomena during LAM.

In situ, in operando X-ray radiography
For this research, the team created a novel LAM process replicator, the LAMPR, which allows them to image and quantify the formation of the melt track as the layers are printed during AM. The LAMPR was designed to fit on the beamline and mimics a commercial LAM system, with windows that are transparent to X-rays, allowing scientists to see right into the heart of the LAM process as it takes place. They used X-ray radiography with high temporal and spatial resolution to uncover key mechanisms of laser-matter interaction and powder consolidation during LAM, including the formation and evolution of melt tracks, spatter patterns, the denuded zone (a powder-free zone) and porosity in the deposited layers. The time-resolved quantification of the pore and spatter movements gave crucial information of their flow velocities and direction, which are not possible to acquire using other techniques.

“The LAMPR is a unique piece of equipment, and beamline support was utterly essential. We worked with Diamond staff right from formulating the proposal. Diamond helped with the mechanical design, and the optics and integrating the LAMPR into the control systems”, says Dr Alex Leung, the PDRA leading the experiments.

The results of these experiments clarify aspects of the physics underlying LAM, which are crucial for its development. The previous hypothesis was that the formation of surface porosity on finished objects was due to incomplete melting or insufficient liquid feeding. However, this research shows that it is formed via a pore-bursting mechanism. Pores near the surface escape into the atmosphere, leaving behind a surface depression.

This methodology sheds new light on the mechanisms of pore formation, including the migration, dissolution, dispersion, and bursting of pores during LAM, and future investigations in these areas will deepen our fundamental understanding of the nature of the laser-matter interaction.


Figure 2: Using I12 and the LAMPR the complete process of track formation during 3D printing is revealed. A first complete track and details on the laser/gas flow are shown at the top. The first stages of the formation of this track are shown below for the first few milliseconds of track formation.

To find out more about X-ray radiography, or to discuss potential industrial applications, please contact the Industrial Liaison team on 01235 778797 or send us an e-mail. You can keep in touch with the latest development by following us on Twitter @DiamondILO or LinkedIn.