Selective Laser Sintering of Ceramic Materials

This paper will focus on efforts to develop the alumina - ammonium phosphate material system for Solid Freeform Fabrication. When the powder mix is irradiated with a laser beam, ammonium phosphate ( m.p. """ 190 0 C ) melts and forms a glassy phase between the alumina grains. The "green part" obtained by laser processing is then subjected to secondary heat treatment to optimize the properties of the final composite. The effect of various material, laser and machine parameters on the density, strength, surface finish and microstructure of the final part are described. One of the applications for selective laser sintering is its use in directly manufacturing ceramic molds for the investment casting process. We will describe some of the the results we have obtained so far in fabricating composite ceramic molds directly and using them to cast metals.