Coaxial powder delivery system for Laser metal deposition shaping

Laser forming based on Rapid Prototyping (RP) is a state-of-the-art technology, which creates part by focusing an industrial laser beam on the surface of processing workpiece to create a molten pool of metal. A small stream of powdered alloy sprayed from a nozzle is then injected into the molten pool to build up the part gradually. By moving the laser beam back and forth and tracing out a pattern determined by a CAD, the solid metal part is fabricated line by line, one layer at a time. By this method, a material having a very fine microstructure due to rapid solidification process can be produced. In the present work, a type of direct laser deposition process, called Laser Metal Deposition Shaping (LMDS), has been employed and developed to fabricate metal parts. The LMDS apparatus consists of four primary components: energy supply system, motion control system, powder delivery system, and computer control system. These components have their specified functions, but work in association with each other. Among them, powder delivery system is the most important one that considerably determines the quality of the as-fabricated metal part. Through the experiments, it is proved that the coaxial powder delivery system can provide uniform and steady powder stream, and possesses the omnidirectional characteristic which results in the smooth appearance and consistent geometry of the deposited part.