Selective laser sintering of high-density alumina ceramic parts

Manufacturing high temperature ceramic parts with Solid Freeform Fabrication (SFF) technology has been of great research interest lately. Described in this paper is a process based on Selective Laser Sintering (SLS) to fabricate 3-dimensional alumina green parts layer-by-layer, followed by binder burnout and sintering to obtain high-density ceramic parts. This SLS process has been developed to manufacture 3D parts including airplane models, letter bars, etc. from mixtures of alumina powder and stearic acid binder. These mixtures were generated by mixing alumina powder with stearic acid in a ball mill. The average particle size of the alumina particles is 0.26 mu m. The SLS process parameters were tuned such that the green parts can be built with reasonably sharp geometrical features and that the sintered parts have good mechanical and physical properties. Proper binder burnout conditions were determined in order that the resultant parts after the binder burnout process have no visible cracks. Alumina ceramic parts were obtained by firing the green parts at 1600 degrees C. The alumina ceramic bars achieved 255 MPa in flexural strength, and the bar relative density achieved is 88%. These results are discussed.