Rapid prototyping using direct laser deposition - the effect of powder atomization type and flowrate

For rapid prototyping and tooling, direct laser deposition (DLD) is one of the most promising techniques. The method can be used to produce fully dense metallic parts in a single stage, can be applied to a wide range of metals and metal alloys and, when a coaxial deposition head is used, is flexible enough to allow complex parts to be built. So far, however, almost all the powders chosen for use as the build material in this field have been of the gas-atomized (GA) type, and research has generally been confined to this field. The present paper considers the use of water-atomized (WA) 316L stainless steel powder by comparing it with the more conventional gasatomized powder used during the laser deposition process. Analysis of the characteristics of multiple-layer clads produced by the two powders reveals some potential benefits of using water-atomized powder: results show that the sidewall finish is smoother and the microstructure finer and more textured, although the deposition rate is considerably lower. Other disparities between parts built using the two powder types are demonstrated, and reasons for the final differences are explored.