Laser-assisted selective infiltration of superheated μ-droplets for direct fabrication of metal parts

Abstract

In today``s highly competitive marketplace, it is of great significance for the manufacturing industry to reduce lead-time and costs for the product development. Since first emerged in 1986, as a new time-reduction method, Solid Freeform Fabrication (SFF) technology, also called Rapid Prototyping (RP), has helped successfully to address the challenges. To date, various direct metal SFF processes have been developed that are able to produce metal parts or molds directly from the CAD data by using metals as part material. Since 1998, some of them have been commercialized and many others are still in research pursuing commercialization. In comparison with the conventional manufacturing processes, they have unique capabilities stemming from the layer-by-layer addition of metal. They are capable of building injection molds with the conformal cooling channels that considerably reduce cycle time and improve part quality; and functionally gradient parts that comprise multiple metals; and smart structures that contain electronic devices at intended locations. Despite such distinctive advantages, direct metal SFF processes have not yet met manufacturers`` requirements completely due to dimensional inaccuracy, poor surface finish, long build time and stress-induced deformation. This is primarily because in most of the direct metal SFF processes, each layer undergoes overall phase change. The objective of this study is to develop a new direct metal SFF process, called Selective Infiltration Manufacturing (SIM), in which superheated microscopic metal droplets are ``selectively`` infiltrated into a layer of microscopic metal powder that is preheated by a laser. During the entire process, the powders that serve as a base (or matrix) material remain solid and thus contribute to reduce thermal deformation and internal stress due to the accordingly reduced amount of molten metal at each layer. First of all, to produce superheated μ -droplets of Sn-37Pb wt.%, infiltrant, a dr...