Skip to main content
eScholarship
Open Access Publications from the University of California

UC Irvine

UC Irvine Electronic Theses and Dissertations bannerUC Irvine

Long and Short Time Scale Mass Capture Mechanisms in Laser Directed Energy Deposition Additive Manufacturing

Abstract

Laser Directed Energy Deposition (L-DED) Additive Manufacturing (AM) offers unprecedented flexibility in direct fabrication of metallic components in a way that can be readily integrated with existing CNC subtractive machining technologies. The core building block of the technology is the melt pool, the dynamic bead of molten material established by the energy equilibrium between incident laser energy and thermal dissipation. While the unique solidification microstructure of the melt pool has attracted intense scrutiny, the mechanisms determining how mass is originally incorporated into the melt pool have been less well studied. In this work, three new tools are applied to the task of broadening the understanding mass capture behaviors. First, over long time scales it was observed that mass capture efficiency evolves over the course of depositing many layers as machine conditions change; a non-empirical model constructed to track this revealed self-stabilizing behavior in working distance in open-loop control systems. Second, on very short time scales, high speed videography was employed to understand what happens at the moment of impact between a feedstock powder particle and the melt pool. It was revealed that particles are captured by surface tension before fully melting. Third, this particle retention time was investigated with numeric simulation to highlight its relationship to particle size, impact velocity, thermal distributions and wettability.

Main Content
For improved accessibility of PDF content, download the file to your device.
Current View