Surface Finish Issues after Direct Metal Deposition

Abstract:

Derived from laser cladding, the Direct Metal Deposition (DMD) laser process, is based upon a laser beam – projected powder interaction, and allows manufacturing complex 3D shapes much faster than conventional processes. However, the surface finish remains critical, and DMD parts usually necessitate post-machining steps. In this context, the focus of our work was: (1) to understand the physical mechanisms responsible for deleterious surface finishes, (2) to propose different experimental solutions for improving surface finish. Our experimental approach is based upon: (1) adequate modifications of the DMD conditions (gas shielding, laser conditions, coaxial or off-axis nozzles), (2) a characterization of laser-powder-melt-pool interactions using fast camera analysis, (3) a precise check of surface aspects using 3D profilometry, SEM, (4) preliminary thermo-convective simulations to understand melt-pool hydrodynamics. Most of the experimental tests were carried out on a Ti6Al4V titanium alloy, widely investigated already. Results confirm that surface degradation depends on two aspects: the sticking of non-melted or partially melted particles on the free surfaces, and the formation of menisci with more or less pronounced curvature radii. Among other aspects, a reduction of layer thickness and an increase of melt-pool volumes to favor re-melting processes are shown to have a beneficial effect on roughness parameters.

• Periodical: Materials Science Forum (Volumes 706-709)
• Pages: 228-233
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.706-709.228
• Online since: January 2012
• Authors: Patrice Peyre, M. Gharbi, C. Gorny, Muriel Carin, S. Morville, Denis Carron, P. Le Masson, T. Malot, R. Fabbro
• Keywords: Deposition, Laser, Melt Pool, Simulation, Surface, Titanium

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