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Keywords
Manufacturing, Deposition
Abstract
Laser chemical vapor deposition (LCVD) as a manufacturing process holds the potential to build compositionally and geometrically unique objects. Georgia Tech's LCVD system has been used in the past to create three-dimensional and laminate structures out of carbon. Recently molybdenum and boron nitride were successfully deposited and upgrades to the system have allowed for higher spatial resolutions and more varied geometric capabilities. Upgrades include the addition of a fourth linear stage and implementation of an argon ion laser. Detailed thermal and fluid modeling have provided more insight as to the important parameters and characteristics of the LCVD process.
Introduction
Laser chemical vapor deposition (LCVD) is a novel process, which utilizes the properties and technique of chemical vapor deposition (CVD) on a very small-localized basis for the creation of freeform parts (Duty et al., 2001; Jean, 2001). CVD utilizes reactive reagents and global heating to initiate the necessary chemical reactions for obtaining the desired deposit. The energy is typically supplied from a large heating element surrounding the reaction chamber. For this reason CVD has traditionally been used as a coating technology as opposed to a method of making freeform parts. LCVD replaces the global heater with a laser such that only the desired region is heated and therefore deposition occurs locally as shown in Figure 1. Like CVD, LCVD is used mainly to produce ceramics and metals, including many exotic materials.
Georgia Tech's LCVD system was designed to be an alternative prototyping and/or manufacturing system for parts that needed to be made of uncommon materials in specific geometries or parts that were needed in final shape after manufacture with minimal or no post processing. The system is powered by a 100 W CO^sub 2^ laser which is optically delivered by means of stationary mirrors inside a sealed reaction chamber. As the location of the laser spot is fixed within the chamber, stages are used to move the substrate, and thus the region on the substrate where the reaction is going to occur. The power of the laser can be controlled using an automatic control system monitored by a thermal imaging camera; this allows for effective controlling of temperature during the reaction. In addition to thermal control the other...