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Laser-matter interactions in additive manufacturing of SS316L and 13-93 bioactive glass revealed by in situ X-ray imaging

DOI: 10.1016/j.addma.2018.08.025 DOI Help

Authors: Chu Lun Alex Leung (University College London; Research Complex at Harwell) , Sebastian Marussi (Research Complex at Harwell; The University of Manchester) , Michael Towrie (Central Laser Facility, Research Complex at Harwell) , Jesus Del Val Garcia (University of Vigo) , Robert C. Atwood (Diamond Light Source) , Andrew J. Bodey (Diamond Light Source) , Julian R. Jones (Imperial College London) , Philip J. Withers (Research Complex at Harwell; The University of Manchester) , Peter D. Lee (The University of Manchester; University College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Additive Manufacturing

State: Published (Approved)
Published: August 2018
Diamond Proposal Number(s): 13641 , 15250

Abstract: Laser-matter interactions in laser additive manufacturing (LAM) occur on short time scales (10-6 - 10-3 s) and have traditionally proven difficult to characterise. We investigate these interactions during LAM of stainless steel (SS316 L) and 13-93 bioactive glass powders using a custom built LAM process replicator (LAMPR) with in situ and operando synchrotron X-ray radiography. This reveals a range of melt track solidification phenomena as well as spatter and porosity formation. We hypothesise that the SS316 L powder absorbs the laser energy at its surface while the trace elements in the 13-93 bioactive glass powder absorb the laser energy by radiation conduction. Our results show that a low viscosity melt, e.g. 8 mPa s for SS316 L, tends to generate spatter with a diameter up to 250 µm and an average spatter velocity of 0.26 m s-1 and form a melt track by molten pool wetting. In contrast, a high viscosity melt, e.g. 2 Pa s for 13-93 bioactive glass, inhibits spatter formation by damping the Marangoni convection, forming a melt track via viscous flow. The viscous flow in 13-93 bioactive glass resists pore transport; combined with the reboil effect, this promotes pore growth during LAM, resulting in a pore size up to 500 times larger than that exhibited in the SS316 L sample.

Journal Keywords: X-ray imaging; in situ; SS316L; 13-93 bioactive glass; molten pool dynamics

Subject Areas: Materials

Instruments: I12-JEEP: Joint Engineering, Environmental and Processing , I13-2-Diamond Manchester Imaging

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