Effect of processing parameters on the mechanical properties of powder injection molded alumina

Abstract

In this study, powder injection molding of alumina was investigated. Initially, rheological tests in a capillary rheometer of feedstocks prepared by mixing alumina powder with a water soluble binder composed of 65 wt % polyethylene glycol, 30 wt % polyethylene, 5 wt % stearic acid were carried out. Fused alumina powder with a median diameter of 10.66 ?m and the binder were mixed in various volume percents in dry condition. Later feedstocks were prepared from these mixtures by further mixing and extruding in a twin screw extruder. Critical solids loading of alumina was determined to be 58 volume percent. Viscosities of various feedstocks prepared with 50 to 56 volume percent alumina were determined to be below 500 Pa.s at temperatures 160 °C (320 °F) to 190 °C (374 °F). Tensile and prismatic bending samples were produced by powder injection molding of the feedstock with 55 volume percent alumina. Debinding was carried out in water at 50 °C (122 °F) for 24 hour and sintering was done in various temperatures up to 1800 °C (3272 °F). Prismatic bending samples had maximum properties of 79 % theoretical density, 13.74 % shrinkage and 133 MPa (19.3×103 psi) bending strength. Tensile samples had maximum properties of 85 % theoretical density, 14.17 % shrinkage and 64.17 MPa (9.3×103 psi) tensile strength. © 2008 Metal Powder Industries Federation.