R. S. Evans, D. L. Bourell, J. J. Beaman and M. I. Campbell
Department of Mechanical Engineering
University of Texas at Austin
Austin, TX 78712
mc1@mail.utexas.edu
Reaction bonded silicon carbide (RBSiC) has a wide variety of industrial applications and a manufacturing process based on Selective Laser Sintering (SLS) has been demonstrated in previous research at the University of Texas. That study was directed toward semiconductor manufacturing applications and was based on prior indirect SLS methods. Several key research questions were addressed for three main manufacturing phases: preform SLS, binder burnout and reactive infiltration. The current research is focused on development of material systems and manufacturing capability and is directed toward a broader set of potential applications. Preform formation utilizes SiC powder of an appropriate average particle size mixed with a multicomponent binder. The preform or green part is then placed in a vacuum furnace to carbonize the binder. The details of the binder chemistry must support accurate SFF shapes and acceptable surface roughness, a strong green part and maintenance of the part shape during the first furnace operation. Finally, the physics and chemistry of the infiltration process, based on the microstructure of the initial green preform, determine the viability of the manufacturing process and the characteristics of the final composite material. The functionality of metal, polymer and ceramic matrix composites can support the growing SFF industry desire to move beyond functional prototyping and into manufacturing arenas. This project is being explored for more general application to matrix composite materials, especially highly functional systems tailored specifically for SLS. The goal is to establish the governing principles of binder function, carbonization and infiltration as well as to understand the interdependence of these phases in terms of manufacturing application. With this understanding new applications and special SLS composites can support the development of new products and a greater SFF manufacturing presence. This paper provides an introduction to the material, a look at basic rapid manufacturing trends, an overview of the previous work, a review of relevant RBSiC material science issues, and an outline of the current study.