Surface Finish Issues after Direct Metal Deposition

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