|
As a few mature additive manufacturing reach critical mass, a few new technologies keep appearing. A new 3D printing process based on shock wave cold compaction of nano-powders is used to create micro-parts. The SWIFT technique - Shock Wave Induced Freeform Technique) as it is called - relies on the generation of shock waves generated by a short-pulse laser to selectively compact layer after layers of nano-particles to form micro-structures [1]. Let’s dig in.
Schematic of laser shock 3D printing of nanopowders [1].
Laser shock wave sintering of powders is a comparatively new technology development [2-11]. Researchers claim it has the capability to overcome limitations typically found in hot sintering processes (SLM, EBM): shrinkage, porosity and rough surface. It has been tested with various non-metal powders so far: ceramics and diamond nanopowders.
SWIFT shows potential for the fabrication of high performance diamond micro-tools with high aspect ratios, smooth surfaces and sharp edges. SWIFT does not work with microsized powders.
Shock waves are triggered by the local and rapid vaporisation of a thin sacrificial layer with a high intensity short-pulsed laser. Sublimation of the material generates recoil pressure that is confined between the substrate and the transparent cover. This plasma further expands further upon additional energy absorption. The extreme pressure waves formed (several GPa of local pressure! [2]) generate plastic deformation that result in densification at extremely high strain rates.
The shock energy is mostly absorbed by the particle boundaries. It is then dissipated in the forms of extensive plastic deformation, interparticle friction, kinetic energy and defect generation. Interparticle joining [2, 3] comes from internal heating, full or partial melting or solid-state diffusion bonding.
Researchers found that the energy absorption is much greater for small particles [2, 3] given the presence of a large number of boundaries. In nanopowders, the internal heat may transfer throughout the entire particle, thus providing an advantage over coarser materials where the heating is only superficial. In addition to shock energy, shock duration (proportional to pulse duration) is a key parameter to achieve good bonding.
References
[1] P. A. Molian, 3D Printing of Nanoscale Powders using Laser Shock Waves, Journal of Micro and Nano-Manufacturing, doi:10.1115/1.4031462 [2] Thadhani, N., 1988, “Shock Compression Processing of Powders,” Material and Manufacturing Process,” 3, pp. 493-549. DOI: 10.1080/10426918808953217 [3] Vreeland, T., Jr., Kasiraj, P., Ahrens, T., and Schwarz, R., 1983, “Shock Consolidation of Powders – Theory and Experiment,” In: Rapidly Solidified Metastable Materials. Materials Research Society symposia proceedings. No.28. Materials Research Society, Warrendale, PA, pp. 139-143. ISBN 9780444009357 [3] Akashi, T., and Sawaoka, A., 1987, “Shock consolidation of diamond powders Journal of Materials Science, 22 (9), pp. 3276-3286 [4] Kanel, G., Razorenov, S., and Fortov, V., 2004, Shock-Wave Phenomena and the Properties of Condensed Matter, Springer Verlag, New York, Chapter 1 DOI:10.1007/978-1-4757-4282-4 [5] Deng, C. and Molian, P., 2013, “Nanodiamond powder compaction via laser shockwaves: experiments and finite element analysis”, Powder Technology, 239, pp. 36-46 [20] Deng, C., and Molian, P., 2012, “Laser shock wave treatment of polycrystalline diamond tool and nano-diamond powder compact,” The International Journal of Advanced manufacturing Technology, 63 (1-4), pp. 259 – 267 [6] Baerga, V., and Molian, P., 2012, “Laser shockwave sintering of nanopowders of yttria-stabilized zirconia,” Materials Letters, 73, pp. 8-10 [7] Melookaran, R., Melaibari, A., Deng, C., and Molian, P., 2012, “Laser shock processing on microstructure and hardness of polycrystalline cubic boron nitride tools with and without nanodiamond powders,” Materials and Design, 35, pp. 235-242 [8] Molian, P., and Baerga, V., 2011, “Laser shock wave consolidation of micropowder compacts of fully stabilized zirconia with addition of nanoparticles,” Advances in Applied Ceramics, 110 (2), pp.120-123 [9] Molian, P., Molian, R., and Nair, R., 2009, “Laser shock wave consolidation of nanodiamond powders on aluminum 319,” Applied Surface Science, 255, pp. 3859–3867 [10] Zhyrovetsky, V., Kovalyuk, B., Mocharskyi, V., Nikiforov, Y., Onisimchuk, V., Popovych, D., and Serednytski, A., 2013, “Modification of structure and luminescence of ZnO nanopowder by the laser shock-wave treatment,” Physica Status Solidi (C) - Current Topics in Solid State Physics, 10 (10), pp.1288-1291 Comments are closed.
|