Design, operation, and heat and mass transfer analysis of a gas-jet laser chemical vapor deposition system

Laser chemical vapor deposition (LCVD) is a new manufacturing process that holds great potential for the production of small and complex metallic, ceramic, and composite parts. However, the field of LCVD is still in its infancy and the deposition process is not well understood, especially as it relates to the manufacture of three-dimensional objects. Therefore, the current research has focused on (1) designing and developing an advanced gas-jet LCVD system, (2) understanding and modeling the effects of the gas-jet on the deposition process, and (3) using the LCVD system to deposit a ceramic (boron nitride) and a metal (molybdenum).; Various substrates and reagent mixtures were evaluated with the thermal and fluid models. It was determined that the most significant variable in the laser heating of a substrate for the LCVD process was the substrate thermal conductivity. The forced convection cooling imposed by the gas-jet reagent delivery system was also significant, accounting for a 15 to 20% change in the substrate temperature. The mass transport model predicted that the gas-jet was an effective tool for increasing the concentration of reagent gases at the surface of the substrate across all deposition regimes. The gas-jet also generated higher deposition rates and increased deposit resolution for those processes severely limited by diffusion.