A Study of the Diffusion Characteristics of Tungsten Bar Stock and Tungsten Produced via Direct Metal Laser Sintering (DMLS)
Date of Award
Master of Science (MS)
Using a vacuum hot extraction method diffusivity and concentration of hydrogen were measured in samples of tungsten bar stock and direct metal laser sintered (DMLS) tungsten. It was found that the tungsten bar stock closely adhered to the model established by Frauenfelder. The DMLS samples approximately follow a downward sloping trend over the 500K-1200K temperature range. The trend is opposite of what is expected suggesting processing has a major effect on diffusion behavior. A CFD model was created using ANSYS Fluent to simulate the diffusion behavior. The model functions by separating out diffusion mechanisms and solving Fick’s law with each mechanism treated as its own species. When the results of the simulation are recombined the diffusion behavior of the original part is retrieved. At the coupon level the simulation proved to be an effective tool at predicting diffusion behavior. This modeling technique is intended to be applied to more complex geometries to appropriately design degassing cycles to reduce cycle on time and improve vacuum stability for DMLS formed parts.